Advances in Child Development and Behavior, Volume 4

ADVi4NCES IN CHILD DEVELOPMENT AND BEHAVIOR

VOLUME 4

Contributors to This Volume Justin Aronfreed

John M . Belmont Yvonne Brackbill Earl C. Butterfield David Elkind Hiram E. Fitzgerald Frances Degen Horowitz

S. J. Hutt

H . G. Lenard H . F. R. Prechtl

ADVANCES IN CHILD DEVELOPMENT AND BEHAVIOR edited by Lewis P. Lipsitt Department of Psychology Brown University ProrTidence R Izodc Islotitl

.

Hayne W. Reese Department of Humoii 1)rwkptnent University of Kansas Lawrence, Kansas

VOLUME 4

@

1969

0

COPYRIGHT 1969, BY ACADEMICPRESS, I N C . ALL RIGHTS RESERVED. NO PART O F T H I S BOOK MAY BE REPRODUCED IN ANY FORM, BY PHOTOSTAT, MICROFILM, RETRIEVAL SYSTEM, OR ANY OTHER MEANS, W I T H O U T W R I T T E N PERMISSION FROM T H E PUB1,ISHERS.

ACADEMIC PRESS, INC. I I I Fifth Avenue, New YoiA. N e w Y o l k 10003

United Kingdom Edition published by ACADEMIC PRESS, I N C . ( L O N D O N ) LTD Be1 keley 5quaie H o u w , 1 ondon W I

LIBRARY OF CONGRESS CATALOG CARDNUMBER: 63-23237

P R I N T F D IN T H F U N I T F D STATES OF A M E R I C A

List of Contributors Numbers in parentheses indicate the page\ on h h i c h the authors' contributions begin

JUSTIN AKON FREED. Departin en i o f P s y clr o l o g y , l i t iiwr.sity of' Pt,iinsy lrw n ici Pi1 i l a d d p hia , P r nnsy 1vririiu ( 2 0 9 )

J O H N M . BELMONT, Department o f Psychology. Yiilc i l i i i ~ ~ c ~ r , s N i t yPv' MH, ( A v ( ~Cotinecticirt II, (29)

Y V O N N E B R AC K B I L 1- . I Drprirttneiit of' Psychology, Uiii\~cr.sityof' D e m ~ r Dc.ri\~>r, , Colorado ( 173)

EARL C. BUTTERFIELD. Uni17ersity O J ' K U ~ I SMdictil US Ci!titer,Kurisus C i t y , Kunsus ( 2 9 )

D A V I D ELKIND. Dcprirtinc~ntof Psychology, 7 1 i o Utiii~ersityof

Rochester, R i w r Cumpir.s Sttr-

tiori. Rochi>.siPr, Nctc, York ( I )

H l K A M E. FITZGEKALD. Drptirtinrnt of' Psychology. Mic.liigtin S t r i t e Uni\w.sity, East Ltinsing, M i c h i gun ( 1 7 3 )

F R A N C E S DEGEN HOROWI I % . Depurtment

of

Hikt?iuii

Dc

Iopnicrit,

Uniwrsity qf' K a i m i s , Latt,retice,

Kunsus (83)

S. .I. HUTT,' Dt7p N rttnc>ii1 of' Ll c \.cJlopniciit ( i I N ~ i r r'logy, ( I/ ti ir*o.sity H o s p i t d , G rot1 iiigeii Thc Nctl1crIund.v ( I 2 7 )

~

IPresent address: Ikpartment of O h t e t r i c s and Gynecologl . Georgetown University School o f Medicine. Washington. I). C'. 2Pre\ent address: St. Catherine's ( cillepe, and Human Development Research Unit, Pal-h Hospital foi- Chi Id (-en, 0 x loId. Ikglii [id. V

H . G. LENARD," Deprirtrnent of Developmental Neurology, University Hospital. Groningen, The Netherlands ( 1 2 7 )

H . F. R. PRECHTL, Department of Der~eloprnetitalNeurolog.~. University Hospital, Groningen, The Netherlands ( 1 2 7 )

:'Pi-esent address: Universitits-Kinderklinik, Gottingeti, Germany.

Preface The number of research and theoretical publications in the field of child development and behavior has increased enormously in recent years. The scientist and student are confronted with a formidable task in keeping abreast of new developments within their areas of specialization through the use of primary sources: moreover, the task of maintaining scholarly knowledge in secondary areas of interest by reading original sources is almost insurmountable. The serial publication of A t l r w n c r s in Child Developnient arid Behuvior is intended to provide scholarly technical articles serving as reference material in the field and t o serve two other purposes. On the one hand, because the articles are critical syntheses, summarizing and integrating recent advances in the tield, it is hoped that teachers, researchers, and students will find these documented reviews useful in the endless task of remaining knowledgeable in areas peripheral to their primary focus of interest. Especially in such secondary areas, there is an indisputable need to facilitate the task by reducing the frequency with which original sources must be consulted. On the other hand, the editors are also convinced that these integrative and critical papers will be of considerable usefulness lo the researcher in the problem areas of his primary concern. by exposing complexities or offering fresh viewpoints as much as by reviewing what is known. The publication of Volume 4 in the series marks the introduction of a new coeditor, Hayne W. Reese, replacing Charles C. Spiker. The present editors gratefully acknowledge the inestimable contribution of Professor Spiker, who a s cofounder of the series helped to assure its high standards of production. We will strive to maintain these standards. The senior coeditor with the publication of Volume 5 will be Professor Reese, following which he will become sole editor. The editorial policies of the cofounders of the series will. however, be unchanged. N o attempt is made to organi7e each volume around a particular topic or theme. Manuscripts are solicited from investigators conducting programmatic research on problems of current interest. The editors often vii

encourage the preparation of critical syntheses dealing intensively with topics of relatively narrow scope but of potentially considerable interest to the scientific community. Although appearance in the volumes is ordinarily by invitation, unsolicited manuscripts will be welcomed for review if submitted first in outline form. We wish to acknowledge with gratitude the help of Keith G. Scott, Doniild S. Blough, and Einar K. Siqueland, who assisted in the critical reading of manuscripts for this volume. We wish to thank Eunice Mabray for aid in the collating of materials. Appreciation is also expressed to our home institutions, Brown University and the University of Kansas, which generously provided time and facilities to produce this volume.

M u v , I969

LEWISP. L1Pwr-r H A Y N EW. REESE

Contents ............................................ PREFACE .................................................... ...................... C O N E Nrs O F P R E V I O UVSO L U M I ~ S I - I S l OF C O N IKIBUTOKS

V

vii

xi

Developmental Studies of Figurative Perception D A V I D EL.KIND

I . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Problem of Figurative I’erception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2 2

Theoretical Background oi ttie Kesexrch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Assessment o f Pei-ceplii;il .Actibities . . . . . . . . . . . . . . . . . . . . . . Variables That Affect Pel-tormnilce 0 1 1 kleasures of Perceptual Ac Pel-ceptual Activities in 0 t h r . i ( ognit ive Functions . . . . . . . . . . . . . . . . . . . . . Summary and Cornmentar) . . ............................ Kefercnccs . . . . . . . . . . . . . . . . . . . ........................

4

I1. I I I. IV . V. VI . V 1I .

7 14

18 23 26

The Relations of Short-Term Memory to Development and Intelligence JOHN M BELMONT A N D t 4 K I

(

BUTTERFIELD

I . Introduction . . . . ........................................ I I . T h e Study of Ikvelopnieiit iiiicl Intelligence . . . . . . . . . . . . . . . . . . I I I . Methodological Coiisidei at ion\ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV . The Relation of Forgetting K ; i l e to 1)evelopment . . . . . . . . . . . . . . . . . . . . . . . V. VI . V1 I . VI11 . IX .

The Relation of Forgetting K,ite to Intelligence . . . . . . . . . . . . . . . . . . . . . . . . Summary and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Direct Measurement o f Acqriisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T h e Role of Retrieval Procesws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . ...............................

.

30 31 32 37 42 52 61 75 78 79

Learning. Development Research. and Individual Differences F R A N C E S D E G E N HOKOWI I /.

I . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . T h e Problem of Individual L>ill’ei.cnccs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Individual Ditfererices and I t’t:i B > C > D t h a t involves the relation “next to”). It would be possible to illustrate how other perceptual activities such a s transport and anticipation (or set) could also be involved in reading, but these examples should suffice to illustrate the case for the importance of logic-like processes in reading.‘ In order to test the role of perceptual activities in reading, we examined a large number of school children on a battery of perceptual activity measures and tests of reading achievement (Elkind, Horn, & Schneider, I965a). A factor analysis of these tests revealed a common factor to be present in all of them. To ensure that this common factor was not general intelligence in disguise, we matched a group of slow and average readers for 1Q (on a nonverbal test) and pretested them on Form A of the PAT, then trained them on Form B, and retested them on Form A . The slow readers performed more poorly initially. took more trials to learn, and learned less than the average readers of comparable overall intellectual ability (Elkind, Lat-son. & Van Doorninck. 1 9 6 5 ~ )Here, . then. was some evidence for the validity of our analysis that perceptual activity was involved in reading achievement. If our results were reliable and perceptual activities are involved in reading. then to the extent that one can train children to improve their perceptual activities, to that extent should their reading also improve. The training, however, must be truly perceptual and really force the children to attend to the visual stimuli. With these considerations in mind we devised a set of nonverbal exercises for training groups of children on various perceptual activities (Elkind. 1966, 1969). To test the efficacy of these exercises. we (Elkind and Deblinger, 1969) matched 60 inner-city Negro children on Form X of the California Achievement Tests and on the PAT ( F o r m A ) and the PIT. All of the children were then trained by the writer in half-hour sessions given three times a week over a period of IS weeks. Half of the children, comprising the control group, were trained with the Bai7k S t r r r t Rcader-s ( 1966) and did the reading and the exercises called for in the Tccichrr’s Munuml. The other 3 0 children, comprising the experimental group, were trained with For ii niore detailed discu\sion of perceptual activity and reading. see Flkind ( 1969)

the nonverbal exercises desigiictl t o improve their perceptual activities. (The exercises involved simple scrieh, AIBC'DE - - . a n d more complex variants, scrambled words 1-1 I H I I H I .1-1 E: coding 12345 334 = T I E : I ~ R I l , ~ H I T E A 534 .symbolic transforms SUN -'O:a r i d m a n y other such exercises.) I MOON ~

-~

7

~

~

2

After- completion of the trniniiig the children were ietested o n the PIT, Form B of the PAT. and Foirn W of the California AchieLement Tests Results showed h i t the expel iriientnl children mnde significantly gieater improvement than the contiol i h i l t i i t ~ non Word Form, Word Recognition, and the PIT rhey weie ,iI\o h c ' i d of the control group in Word Association. On the othei hcintl theie weie IIO 'ippclrent differences in comprehension. and the expel i n i t ' n t d group did inore poorly than the control group on the "Meaning ot Oppo4ites" subte\t of the Califoi nin Achievement Tests The\e results lend fiirthei s ( i p 1 x ) i t lo O I I I contention thdt peiieptu'il n i tivities play a pait in the peiLcptii'il ,i\prcts of reading Oui \ucces\ has dl so e nc 0 uraged 11b to 11n d e rt ' t k c i i I o I e e i,ibo i d t e t I d i n i n g I n L e s t i g,i t i o n s i ri which the change4 i n nttitudc\ 01 tioth ttx,icher\ nnd childicn 'i', 't consequence of using the pioccciuii.4 i i i . c \ du,ited along with ch,iiig:rs in ' t ~ ; i demic achievement pei \e

-I _he present papci ha4 atteiirplL.tl to do thiee thing4

((I)

\kelch

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geii

ern1 problem of the de\elopiiiciil of tigui'itive perception. i h ) \ u i n ~ i C , i"Li the Piagetian theory of peiceptii.il tic\ elopinent '1s take-oft point t o r the study of figurative peiception. . i n d ( ( ) ic:\iew wiiie o f the i e\ e, ti ~l ith,it the writer and his colleagues h,i\c i i i i ( l t ' i t'iken i n l h i 4 d o m i i n I n [hi\ c o n cluding wction some tentntibc <enciali/,itions regnrdinp t h e g r o th ~ ot figurative perception nre given ,ind \omc p o m i \ i n g directions foi future research are outlined

One generalimtion that sceiii\ 10 I-IC .,iigge\ted b? dl ol our dc\elopmental data is that the growth 01 tigii,iti\c perception is chcii'iCteii/ed bv a transition from n process tti'it 1 4 ieLitrvely p,is\ive and static to one t h d t is relatively active nnd dyn,iiiiii With increasing nge the child is better

able to reverse figure and ground, to integrate parts and wholes, and to scan configurations in more systematic complex and novel ways. In short, our data suggest that the course of perceptual growth is marked by an increasing tendency to act upon any given configuration so as to perceive all of its many and varied facets. A second generalization suggested by our data is that as the child grows older his perception is increasingly determined by higher-order perceptual and cognitive abilities and decreasingly by the Gestalt properties of the stimulus. I t must be emphasized, however, that the Gestalt properties of the stimulus continue. probably throughout life. to exert an important influence on perceptual organization. What changes with age is that the option t o conform or not to confot-in to the constraints of the field effects is always open to the older child and adult but n o t to the young child. Perceptual maturity is, from this point of view, the attainment of a relative a u t m o m y from t he (.i e st a 1t pri nc i p I e s of organ i za t ion. Finally, a third generalization from our data is that, to some extent, the growth of perceptual activities that mediate figurative perception is relati vel y invariant itcross wide differences in environmental s t imulat ion. This is not the same, it must be emphasized. as saying that growth is independent of the environment. Rather, what seems to happen is that perception can utilize u~hatri.erstimuli are available, whether it be the barren hills of South Dakota or the cluttered rooms of a slum home. to nourish and exercise its spontaneous growth. Obviously when specific skills or contents are in question the role of particular- forms of environmental input looms much larger. On the other hand, the basic visual perceptual activities seem to be able t o grow. if not to flourish, in what might be judged as re I at i v e 1 y i m pov e I-i s hed v i sua I en v i 1-0 n m e n t s .

Our strategy in carrying out the research described above has been to throw a floodlight on the problem of figurative perception at large before spotlighting particular research areas. Accordingly, it might be well to say a few words about where our research is going and where others might find fruitful fields of study. 1 . Perc Pptuu 1 (ind Cogni t i v r A c tii9itie.s A question that appeared repeatedly in the w o r k presented here is the determination of the roles of visual perceptual and cognitive factors in figure-ground reversal, part-whole integration. and exploration. At least

three hypotheses are possible and \hould be tested. One of these I S that perception and cognition are w p x i t e systems that parallel one another and are nonetheless distinct. I-tiis i \ the hypothesis Piaget seems to favotand is the one we have advocatecl here. I t is. however, tenable that what we have called perceptual activities are merely cognitive abilities applied to visual material. ContrariMtisc, one could also maintain that what u e call cognitive abilities are simply gcnernlizecf perceptual skills. The ditfculty lies in designing experiments that can ;idequately define and test these hypotheses.

2 . Prrfort?icrti c. e A spot.is of' Pc~r.c. c p t 11 (i I .4c tiiiify Our- studies have by and large locused upon the descriptive developmental aspects of perceptual activit! . We have not, therefore, explored in detail the correlated factors that inay affect performance in our nieuwi-es. To what extent are age change\ i n attention, verbal ability. and cognitive maturity accountable for the obtained results? Likewise. we know little about the encoding. storage, arid retrieval processes involved in the production of a particular response. Where in this sequence is the young child deficient with respect to the older child'! Are the figures coded verbally in short-term memory storage bcloi-e being assimilated to verbal schema o r are they assimilated directly t o figurative schemata without verbal coding or in addition to verbal coding'.' Rlnny more questions could be raised but these should suffice to suggest the uork that must be done in this area. 3 . P r r.ceptiia I A c ti\,ity u n d I I I rli\,itlrrti I I>iff; re n c, t's I t is hardly necessary to emphasic.e i n the context of the work of Witkin. Dyk. Faterson, Goodenough, a t i d Kiirp ( 1962) and more recently of Kagan (1966) the close link between persoi.iality and perception. In addition to the process factors studied b \ Witkin ~ n Kagan, d there are the content differences between individual\ that appear in tests such as the Korschach. How are such differcriics in ligurative perception mediated'? When do they emerge in development and how do they tie u p with the individual's past history and ciilt(ire'?I t is probably fair to say that we still have no viable theory of projection. I t is :it least possible that the study of figurative perception could lead l o 4uch ;I theory. These. then. are some of the gcencnilizations gleaned from our work in figurative perception and some o l ' t h e m a n y problems and questions raised by o u r research. If we have i i o t presented ;I solid and complete body of research. perhaps we have, i n \oiiic small measure. at least indicated the complexities and the promise inherent in the study of the child's response to two-dimensional representat i o n s o t reality.

20 UPFEKENCFS Re~,ik.S/rccl retrdr,r.c. New Yurh: h1aciiiill;in. 1966. Rerlyne. I). E. C ‘ o n , j i r / , rrroristrl ciritl c u r i o s i l j . New Yorh: M c G r a w - H i l l . 1960 Hinet. A. Rr Simon. T ILe developpcment d r I’intelligence che7 le\ enfiints. Anr7c;c P / o y i c / / t e . 1908. 14. 1-94. tlinnie. C.. Elkind. D.. & S!e\bart. J. I . . A comparison o f the visual perceptual ability of ;icou\tic;ill! impaired and hewring children. / r r / r r ~ i t r f I o ~ ~ c ~ / ~ ~ r c 1966. / i ~ ~5/ .f 238-241. igj, ( ‘ I i J I . .I. S . /2ctrrriirig t o i - c i i d : Tlrc g r o t r ~e / l > h ~ i r ro; i i iriqirirv i r i / o tlrv c c . i c ~ r i [ ~ c trrt . , cirri/ rtleologj of o/J (itid u c ’ i i ’ t ~ i c , / l i o d . \(,J’tctrc,/ii,igc hi/c/rc~,it o rrtrd. N e w York. h l c G r a w - H i l l . 1967. DohLh;insky. ‘I. I‘he genetic hasis ol‘evolutiun. I n W. S . 1,anglin K: R. H . O.;borne (Etls.). H r r t ~ i ~ r i~orititiori,\ tr t i r i d origitrs. C a n r‘rnnci\co: Frecman. 1967. Pp. 9- 18. Elkind. D. 7 h e child’s conception o f hi5 i-clipiouh denomination, 1: ‘rhe Jewish child. Jourmrl of’Grrrr~ic~ /’.\w/udi)gj, 1 % I. I J Y . 209-225. l l h i n d . 0. Ambiguous piclures for the studv of perceptual development and learning. Child I ~ c ~ l ~ ~ ~ / r i p r i l 1964, c , ” / , 35. I391 - I 3 0 0 . Flkind. I>. Non-verhal exerci\es for remetli;il re;iding in\tt tiction. C o / i ~ t r t /Sof , / r f i ~ J / . ~ ~ ~ i ~ r , i [ J / , 1966. hlarcti. 3 7 - 3 X . 151hind. I). Ueading. logic and perception A n a p p r o x h t o reading instruction. In J. F. H e l l niuth ( E d . ) . E t / ~ i ~ ~ ~ r /r il ~oc~. rrf or / /) j V . o l . ? . Seattle: Speci;il C’hild Publications. 1969. Flkind. D . Per-ceptual development i n the S i o ~ i x U . n p u b l i \ h c d manu\cript. 1909. J Pel-cept ti :iI t i-;i in I ng i i i i d read iiig :ic h ieve me 11t in d isad van taged / O ~ ” i ~ Z ~ 1969. ?/. 40. I I - I 9 chncider. CJ. Modified w o t d recognition. reading achievement and perceptual de-centr-ation. Jourrrnl c;f’Gc,t~r,ric,P~yc.lio/ogj,1965, 107. 235-25 I . (a). Flhiiid, [I., Koegler. K. U.. Rr Go. E. l‘ffcct\ o f perceptti;il training at three age levels. Sc.ic,rrc-e. 1962. 137. 3 5 3 2 . Flhind. D.. Koegler. R. U.. k G o . F.. Studie\ in perceptual development. I I : Part-whole per, r i r , 35. X 1-90. ception. Child ~ r i ~ c , / ~ ~ p r ~ r c1964. Elkind. D.. Koegler. U. I. NCLLY o r k : Liveright, 1940. Kohler, W.. & Wallach, H . Figur;il ;ifter-elYect\: An investigation o f visual processes. Proccvldings of !he ArnrJric.unP h i l o ~ ~ ~ p h Si ~o c~itert yl , 1944. 88. 269-357. McMurray. J. S. Rigidity in concep(ri;il thinking i i i erogenous and endogenous mentally retarded children. Jorrrnrrl (?/ Cotrsulritig p . \ ~ hology, ( 1954, 18, 366-370. Meili-Dworetski. G. T h e developnicnt t ) l perception in the Rorschach. In H . Klopfer (Ed.j, D r r ~ 7 l o p m r n t si n thc Rorsc.htrt~/!tc( /itiiqu.Vol. 2 . Yonkers, N . Y.: WoIld H o u h , 1956. Pp. 104- 176. Piaget, J . Play. drrunis trnd irni!utio,i i,i I /ii/dhood.New York: Norton, 195 I . Piaget. J . T h e child’s c.onc.eption o j ’ r i u t i i h r . I o n d o n : Routledge & Kegan I’aul. 1952. ta) Piaget, J . Thr luriguuge und t h o i r , q h / the, child. London. Routledge & Kegan Paul. 1952. (b) Piaget. J . Les m&trnismr.s percaptlfs P,ii 1 4 . I ’ i e ~ w sUniveryitaires de France. I96 I . Piaget. J.. & Krafit, H. La notion dc I ‘oidi-e de\ Cvenernents et le t e ~ des t images e n & soudre. Architbes de P s ~ c . ~ o / o 1~9 /2 vT ,. I:)~ 40h- 349. Piaget, J., Rr Morf, A . L.cs isoniorphi\nit,\ piItieI\ entre Ie4 \tructures logique5 et les \truetures perceptives. In J . Piaget ( t - d ) , Etrrt/c\ ~ ~ c ; p i . s r i r n o l ogc~ueriqrrr. ~ir Vol. 6. Paris: Presses Universitaires de Francc. I O Y X . Pp. 5 1 - 1 16. Shaffcr. 1.. F. Children’s interpretalioiii of c;ii-toon\. Tcuchers Collagc Contributioris t o Educcition. 1930. N o . 479. Stern. C . . & Stern W . Eririnerrr!ig, u1r.5 \trx,.c’ i r d Irrgc, r n derJruhrrr kindhcir. (4th e d . ) Lcipzig: Barth. 1931. Teegarden, L. Tests for the tendenc,v ( ( 1 iev 11 iii reading. Jourrrtrl of Edirc.rr!iontrl Rcjsc.urc.h, 1933.27, 81-97. Terman, I-. M., & Merrill. M . A . S ! ( i / i / ( ~ t8di n c t i/itcl/igc,nc.c \c.ulr. Ho\ton’ Houghton hlifflin, 1960. Vernon. M . D. T h e relation of cognition mil phantasy in children. Briti.sh . / ( J u ~ M / c ! f P s y chology, 1940, 30, 273-294; 3 1 . 1 - 2 I Vurpillot, E. The development of \c:inning \trategies and their relation t o visual differentiation. J o u r m l c!f’Ex~.,rrinic,rirrr/( ‘ h i l t / P.5 w h o l o g y , 1968, 6. 632-650. Wechsler. D. W w h . t l e r intrlligonc.r \,.c C I / I , f o r c h i l d w n . N e w Yoi-k: P\ychologicnl Corporation, 1949. White. R . W. Motivation reconsidered I Iic concepr of compctence. P . ~ ~ l i d ( ~ g iRcvI’PI~.. c.a/ 1959,66,?97-333. ( I /

Winch, W. H . Children’s perceptions: A n experimental studv of ohservutian and report in young children. Baltimore: Warwick & York, I9 14. Witkin. H. A, , Dyk, R . B., Faterson, H . F.. Goodenough. D. K..& Karp. S. A . Psychological dlxerentiation. N e w York: Wiley. 1962. Wohlwill. J . F. Developmental studies of perception. Psychological Bulletin, 1960. 57. 249-288.

THE R E L A T I O N S O F SHORT-TERM MEMORY T O DEVELOPMENT A N D INTELLIGENCE'

John M . Belniofit crrid Earl C.Butter-eld YALE UNlVERSl I Y A N D UNIVERSITY OF KANSAS

1. I N T R O D U C T I O N

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I I . T H E S T U D Y O F D F V F I OPMEN'I

30

, 4 N D INI'ELLIGENCF, . . . . . . .

?I

I I I , M E T H O D O L O G I('A 1- ('( ) N S I DI- IZA~I'I ONS . . . . . . . . . . . . . . . . . . . . . A . T H E INTERPKE'I'A I I O N O t . I N ' I E R A C T I O N S . . . . . . . . . . . . . . . B. L E V E L O F I M M E D I A ' I F h l F h l O K Y . . . . . . . . . . . . . . . . . . . . . . . . C. P R A C T I C E A N D NONSf'Fciation. t h e American Association on Mental Deficiency, Dr. E. A . Holden. and Dr. 'L1. ( ' . k1;idsen for permission to quote materi;tl from Holden ( 1966) and Madsen ( 1 966).

VI. S U M M A R Y A N D D I S C U S S I O N . . . . . . . . . . . . . . . . . . . . . . . . . A. R E T E N T I O N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. A C Q U I S I T I O N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

....... ....

52 52

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........... .... A. I N T K O D U C T I O N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... B. A P P A R A T U S A N D P R O C E D U R E . . . . . . . . . . . . . . . . . . . .... C . R E S U L T S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . .

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VII. D I R E C T M E A S U R E M E N T OF A C Q U I S I T I O N

V111. T H E RO1.E O F RETRIEVAL. PROCESSES I X . CONCI U S I O N S

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1. Introduction It' short-term memory (STM) is defined as how much a person recognizes, recalls, or reproduces seconds or minutes after some material is presented, then there is ample evidence that STM increases with both age and intelligence. For example, t h e number of digits a person is able to completely reproduce shortly after their presentation (his digit span) increases regularly through childhood and is greater among persons of average intelligence than among the retarded (see, e.g.. Wechsler, 1949). I t must be recognized, however, that how much a person remembers is a complex measure, determined partly by the amount he acquires at the time the material is presented, the rate at which he forgets what he acquired, and the accuracy with which he retrieves what he has not forgotten. Changes in any of these determinants might underlie increases in STM as a function of age or intelligence. Certainly the separate evaluation of acquisition. forgetting and retrieval processes is fundamental to understanding STM functioning in any context. The first purpose of this paper is to summarize the current status of knowledge about relationships offorgetting rute to chronological and mental age ( C A and MA) and to intelligence (IQ), and to consider t h e methodological limitations and interpretative difficulties encountered in the research upon which this current knowledge is based. For this purpose we shall review those studies in which both forgetting rate and IQ or age (early childhood to adulthood) are observable variables, whether or not the investigators were explicitly concerned with the correlation of memory with age and IQ. This excludes studies in which there was either n o age or IQ variability among Ss, or no opportunity to observe retention independently of acquisition and retrieval. A second purpose is to discuss the approach that we are using to separate acquisition and retrieval in order to assess their contributions to total STM functioning.

11. The Study of Development and Intelligence Until recently. most investigators of the relation between retention and developmental level have used ('A as their index of developmental level. However, investigators have become increasingly interested in the relation of forgetting rate to intelligence, and this has led some to adopt MA instead of C A on t h e assumption that MA is a more direct measure of developmental level. Others have continued to use C A as their measure of development. Thus, some investigators have compared groups of CAmatched Ss who differ in IQ.u hile others have compared groups of MAmatched SS differing in IQ. N o consistent interpretative distinction has been made between these dispiit'iittl procedures, and a major controversy has developed over their use (Ikiumeister, 1967; Butterfield. 1968: Weir, I967b; Zigler, 1967). Champions of M A-matched c~ornpariwnshave argued that correlations between IQ and performance on m y tusk may not be clearly attributed to intelligence unless t h e variance Liasociiited with MA is removed from the correlations, either experimentally through the use of MA-matched Ss, or statistically by means of cov:itiance or partial correlation procedures (Butterfield, 1968; Zigler, 1966).This argument stems from a recognition that C A is among the least s;itisf;ictory indices of level of cognitive development. Age is, after all, only :I ineasure o f the length of individuals' lives, and there are marked differences in level of cognitive ability. by whatever criterion it is assessed, among individuals of identical CA. If MA is the appropriate index of level. theti ('A-matched comparisons confound the developmental and intelligence yueslions. because MA and IQ covary perfectly in the CA-match dcsign. Although for the purpose of \titdying some processes,' MA may be far superior to C A as an index of cleveloprnental level, we would point out that the need to match on M A u hen studying I() relations with any particular process depends upon whether that process is a developmental one. Thus, if MA were unrelated to f'orpettinp rate, i t would be unnece match Ss on MA in order t o examine the relationship of IQ to forgetting rate. We must also question, Lilong with some proponents of CA-matching (e.g., Baumeister, 1967),the assirniption that MA-matching eliminates all differences in level of performance between Ss with different IQs. Identical MA scores may reflect \uch vastly different patterns of success and failure on intelligence test items that S s of equal MA may certainly nut be "y "process" we mean changes i n pc,rforiii;ince rewlting fr-om manipulation o f independent random variables. An example ot ;I leLiriiiiigpioces.; would be a reliable change in speed of learning a s a function of variation in t t i ociiitrbe value^ o i t h e material\ to be learned: u forgetting process might he a change i n I C C ~ I I I as i i function o f the length of the retention interval.

considered to be matched, in any fine-grained sense, on performance level for basic research purposes. Yet, performance differences on some variables may interact dramatically with the particular process under investigation. Consequently, it may be differences on these variables, rather than 1Q differences per se, that underlie a relationship between intelligence and processing among MA-matched Ss. This problem vanishes if the different groups of Ss are equated on the particular variables which influence the process. For example, Gerjuoy ( 1967) suggested that Association Age, as determined from word association tasks, would be more appropriate, more relevant than MA as a matching variable in investigations of the relationship between rate of verbal learning and intelligence. A second example, of pressing importance to the study of STM, emerges from the observation that forgetting rate is influenced by the amount of material S is able to acquire during the initial presentation of the material to be remembered (Keppel, 1965; Underwood, 1964). T o study the relation of forgetting rate to intelligence (i.e., IQ) independently of acquisition abilit y , it is therefore necessary to have some direct measure of acquistion. and to account for acquisition differences while exploring the IQ-forgetting rate relationship. Thus, it may be that neither the CA- nor the M A matching procedure is either necessary or desirable in the study of particular cognitive correlates of intelligence. Rather, the important issue is whether groups differing in intelligence are equated on direct measures of variables that are known to influence the process under investigation.

11I. Methodological Considerations The relations of forgetting rate to intelligence and development may be studied either directly or indirectly. The direct approach requires presenting material which is itself to be recalled at some later time. A direct test of the forgetting rate-intelligence relation might involve independent variation of 1Q while employing the classic delayed response as t h e dependent variable. The indirect approach uses learning or other performance measures which supposedly reflect forgetting, but which do not require an overt recall of t h e originally presented stimulus materials. For example, an indirect test can involve increasing the CS-UCS interval in classical trace conditioning while examining the learning rates of subjects of different intelligence levels (Baumeister. Beedle, & Urquhart, 1964; Ellis, 1963; Lobb & Nugent, 1966). O r it might involve an examination of t h e interaction between intelligence and the length of the S-R interval in a pairedassociate task in which the S and R items are temporally separated (Baumeister, 1963).

The foregoing examples illu\tr:ite the logic underlying most of the works to be reviewed below. Although the studies reviewed represent a great variety of tasks and depart from differing conceptions of how forgetting operates in these tasks. thev ;dl use tirns as an independent variable. Either unfilled intervals or intervals filled with various activities are interposed between two events. In the case of a direct STM study, these two events may be the presentation of' material to be recalled and the signal to recall the material. In an indirect study. the two events may be two stimuli that S must associate. The dependent variables would be, respectively. accuracy of recall and strength of association. Time, then, is the independent operation, and forgetting rate is the function relating time to t h e dependent variable. A T H I~ N ILHI'Kt

I 4 I ION OF

I N I I-RAC r l O N S

Any test of memory that employs only one retention interval (1.e.. time is not a variable) provides an inadequate measure of forgetting rate because it confuses forgetting rate with xquisition and retrieval ability. Consider digit span. I t is impossible to clearly interpret a failure on digit span. because it may result f r o m Iorgetting, incomplete acquisition, incomplete retrieval, or some combination of these. Forgetting rate may be separated from acquisition and retrieval by providing two or more retention intervals (Rls). The first KI i s a s short as possible, and results in the immediate memory score. 7 h i s score is a gross index of the combined ability to acquire and retrieve. I ongcr R l s provide further points on the forgetting curve. I t is assunwd that acquisition and retrieval contribute equally to recall at all Rls, s o that the slope of the curve is a relatively pure measure of forgetting rate. Comparisons between Ss of Jiffcrent intelligence levels might be performed using a measure of the slope o f the forgetting curve, w c h as a least squares approximation. However. investigators have favored combining the assessment of forgetting rate with evaluation of the between-Ss comparison. The studies usually involve analysis of variance designs. with developmental or intellectual level ;IS one variable and R1 as a second. Differences between forgetting I-iites are inferred from a Groups by R I interation in which difference4 between groups increase with increasing Rl.," Both methods of assessing forgetting rate acknowledge the point, of bariance p i o c ~ d i i i - eprohahly pi-oduces larger error terms than the compariwn of Iea\t square\ ~ i p ~ i - ~ ) ~ i i i I V I I > I J A I . D I F F E K E N C E S . . . . . . . . . . . . . .

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111. I N D I V I D U A I . D I F b ' E R t N ( ' I . S A N D ILEAKNING . . . . . . . . . . . . . . . . A. G E N E R A L I S S U E S 0 1 - KI'SEAK('H S T R A T E G Y . . . . . . . . . . . . . B. EMPIRICAL STUDIFS O t INDIVIDUAL DIFFERENCES A N D LEARNING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

87 87

C. S O M E T H E O R E T I C A I . ,AI'l'ROAC'HES

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IV. I N D I V I D U A L D I F F E R E N C ' I S A N D I H E S T U D Y O F A T T E N T I O N 07 A. T H E O R I E N T I N G RI.'SPONSE A N D I N F A N T R E S E A R C H . . . 97 B. A T T E N T I O N , I N D I V I 1 ) l ~ A I .D I F F E R E N C E S , A N D D I M E N S I O N S OF S T I M U L A T I O N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 C . O R I F . N T I N G , A-TTENI>IN(;, AN11 L E A R N I N G . . . . . . . . . . . . . . I14 V. S O M E I M P L I C A T I O N S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. T H E C O N C E P T OF ( APAC'ITY IN DEVEL.OPMENT . . . . . . . . B. T H E R E G U L A T I O N O F l>F.VFI O P M E N T . . . . . . . . . . . . . . . . . . .

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'During the preparation of this m;rniisci.ipt the author was partially supported by funds from Grant N o . SP01-HD-00870 allotled to her and her research from funds granted t o the Bureau of Child Research by the Natioiial Institute of Child Health and Human Development. Funds were also made available through the Sigma Xi-RESA Grant-In-Aid Program. T h e author wishes to acknowledge the critical and helpful readings given this manusci-ipt by Boyd McCandless and Gerald Siegel. .Appi.eciation is also due t o the students of the infant laboratory whose interest and skepticisin contributed to the development of some of the ideas expressed in this paper. X?

VI. SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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I . Introduction Wherein lie the significant problems about child development and what research strategies will best hasten solutions? This is the question to which the serious investigator must continually address himself and the one to which each succeeding generation of students has been given a different array of answers. That each generation has seen members of its own rank propose new solutions and strategies attests more to the restlessness of the field than to substantial strides in knowledge. Yet, quietly, if not succinctly, in the last decade some important variables have begun to emerge. Improved techniques are reliably rediscovering some heretofore unreliably observed phenomena. New facts are identifying some of the main threads of the developmental complex. Early development is being brought into focus by the increasing amount of research that is taking hard and sometimes exciting looks at the newborn and very young human organism and discovering its formidable capabilities, its rapidly elaborating response repertoire, and its seemingly enormous variability. The changing arena of controversy has seen the old nature-nurture problem readdressed (Hunt, 196 1 : Lenneberg, 1967) and vigorous arguments advanced for one or another research strategy (Bijou & Baer, 1963; Gollin, 1965; Sidman, 1960). The grand theoretic scheme of Piaget has replaced Freud as the pet developmental research ground and HullSpence and Skinner are represented in the S-R developmental research. Increasingly, t h e developmentalist has been drawn to problems of special populations (Ellis, 1963: Zeaman & House, 1963: Zigler, 1967) and practically involved in the behavior management of these groups (Wolf, Risley, & Mees, 1964). He has been able to provide a wide range of rationalizations for programs geared to attacking problems of national and social significance (Bijou, 1963; Bruner, 1966; Hunt, I96 I). Few experimental attempts are aimed directly at testing the assumptions from which much of this activity stems. The extremes of the assumptional positions are described by the classical statements of nature vs. nurture. Rarely does anyone admit to the extreme position, although the distance that is traveled toward center varies widely, and it is usually possible to classif> an investigator reliably on one or the other side of middle. However, while the revival of the nature-nurture controversy is

Lrrrrning oncl l t i d i ~ ~ i d u uDifferences l

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clearly visible, the direct modification of research toward the solution of the problem has not been so apparent; rather the rationalizations for research have been modified and become more delineated. Substantively, this has taken the form of asserting that the significant focus is in identifying developmental patterns, be they naturally unfolding or environmentally prodded (Gollin, 1965). Opposed to this search for the regularity in the developmental course is the emphasis upon models of mechanisms that will explain the elaborations of the response network in the developing organism (Bandura & Walters, 1963; Zigler, 1963). Procedurally, the push has been for “developmentally” orienied research, modification as a technique, and, sometimes, single subject vs. group design strategies. Imbedded in these developments is the respectful acknowledgement of the persistent and salient fact of individual differences. As we shall see, this fact is highly relevant to the resurgent nature-nurture problem and to the discussions of research strategy. The remainder of this paper is devoted to an attempt to explore systematically the subject of individual differences in human development.

I I . The Problem of Individual Differences In traditional psychology individual differences have been regarded in two ways. In research bent upon discovering the general laws of behavior they have been treated as the “margin of error” (Anastasi, 1965). Thus, a whole cadre of inferential statistical techniques has been developed to aid the investigator to cull out the general functional relationships from an array of individual variations. We shall return to a discussion of this in a later section. The second and more popularly known concern has been in the area of differential psychology. Indeed, the term ‘“differential psychology“ has been used interchangeably with “the study of individual differences.” Beginning with Galton ( 1869) and continuing in the works of others, the two main goals of differential psychology have been articulated: to study the interrelations of traits and to factor out the relative contributions of heredity and environment to the deve1opm:ent of t h e individual (see papers in Jenkins & Paterson, I96 l ). The subsequent and continuing development of mental tests, personality assessments, and various type-trait categorical systems was aimed at the first goal: and the use of these tools., in combination with correlational and manipulative research (and sometimes accompanied by heated discourse), was aimed at the second goal. Both salvos were based upon an essentially static concept of heredity (the given), which would more or

less interact with the environment (the varied). The hope of finding the most powerful predictive assessment procedure at the earliest age possible rested upon a premise of stable individual differences that would have a continuing and measurable effect upon the course of development. This was particularly true in the areaof intelligence testing. Here was the quest for the fixed IQ. Thus were spawned the correlational studies of IQ test peiformance across age within the same subjects as well as numerous parent-child comparisons (e.g., Skodak & Skeels. 1949). I n professing an interest in individual differences, one is immediately identified with such testing and trait or type assessment. However, much of this kind of research is basically involved in repeatedly demonstrating that individual differences do, in fact, exist. The reliability of test performance, which is the hallmark of an acceptable instrument, is always a reaffirmation of this fact. Thus, we have a rather impressive amount of research to buttress our common-sense observation that individual differences do exist and, furthermore. that they persist. The environmentalist is often called upon to explain this latter observation. This he does by relying upon a familiar premise: The individual’s own cumulative history of acquisition has a continually increasing effect upon new acquisition. And, just as one “A” grade in the senior year does essentially little to affect a generally “C” cumulative grade point average, so the experiential history works to create a stable uniquely individual behavioral cumulative base, resulting in a reliable diversity of performance among a group of subjects involved in a standardized situation. However, stable and reliable individual differences are also observed in very young human organisms, at the neonatal level (as close to the naive pigeon or rat as it is humanly possible to get). These are attributed to inherent factors and comfortably accepted by the environmentalist as his concession to obvious common sense: Of course organisms differ at birth. He concedes that the individual heredity of the organism is reflected in a variety of physiological variables, and that these have some behavioral correlates. Thus, t h e environmentalist can be on two sides at once. The same observation of stability of individual differences has two explanations, depending upon the age and experience of the organism. There is the faith that the environment becomes dominant over the early hereditary factors and plays the more significant role in shaping the course of development. From the point of view of the environmentalist, stability of individual test performance over time must really be viewed as a measure of t h e stability of environmental effects rather than the persistence of individual characteristics. The end point of a discussion such as this is usually regarded as trivial and can be summed up by the statement: Environment and heredity interact; it is not possible to isolate the amount each contributes to the devel-

opment of the individual. The itrgument then moves into the practical sphere -after all, we are more likely t o be able to manipulate the environment so let us accept heredity ;IS providing the broad limits of individual capacity (and maybe some special capabilities) and get down to understanding how the organism learns and what environmental manipulations affect learning. Thus dismissing the problem, one dismisses individual differences from the research arena either by group design research strategies or by single subject design tactics. Each of these techniques allows one to avoid the problem of individual differences. Thus, one can also avoid the possibility of discovering the interactional mechanisms that might be basic in determining the coiirse of development. In effect, neither approach has been used to attenc! systematically to individual differences. The remainder of this paper is devoted to a discussion of individual differences in learning, in attention, atid i n research strategy and to an exploration ofthe consequences of becoming committed to t h e systematic study of the role of individual ditt’erences in Idevelopnient.

I 11. Individual Differences and Learning

Anyone who has ever been involved in research on learning with more than one sub.ject under the same set of conditions knows the fact o f indi.vidual variation. As Rrackbill and Koltsova have observed in relation to their review of infant learning: “;\ primary ;goal among American experimenters when planning research is to reduct: t o the minimum extent. vitriance due to between-subject difl’erences, and the tacitly understood policy when, despite all, individual differences in I esults do appear, is to ignore the fact” (Brackbill & Koltsova, 1967, p. 2 13). It has been cogently argued that the search for general principles of learning must necessarily ignore individual differences either by a group design strategy that employs the analytic tool of statistics or by the single subject design that uses experimenter control and within-subject replicability as the criteria of success (Sidman, 1960). Perhaps apocryphally. it has been said that Skinner could not care less how long it takes a pigeon to exhibit stable baseline behavior. Interest blegins once stability has been established. The point of view so well articulated by Sidman ( 1960) is that the psychologist is primarily interested in discovering techniques for gaining precise control over behaviot-. Precise control depends upon identifying the sources of variability, where variability is regarded i t s an example

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of orderliness in nature rather than capriciousness. One implication of the latter part of this statement is that an understanding of the parameters that influence behavior should shed light on the problem of individual differences. However, the tactic has been to emphasize techniques of control rather than research to understand variability systematically. Sidman’s general approach is to eliminate variability rather than study it. The prescription is a very powerful and useful one for some problems. Consider, for example, the proposal for handling variables suspected of contributing to variability: Unwanted variables of the type I have been considering [humidity] exert their maximal effect upon behavior that is maintained weakly. 1 believe that this is a general enough principle to justify ii r u l e of thumb: When intolerable variability is encountered strengthen the variiibles that are directly responsible for maintaining the behavior in question. For example . . . one might increase the subject’s level of food deprivation, inci-ease the sire o f the reinforcement, increase the shock intensity, provide the behavior with an exteroceptive feedback, employ easily discriminable stimuli and. in general make use of as many BS possible of those variables and combinations of variables which are known to exercise a high degree of behavioral control. In other words, instead of trying to manipulate extraneous variables directly, one can often oven-ide their effects by establishing baselines that are relatively insensitike 10 their influence. Successful employment of this technique foi- dealing with variability depends upon the availability o f an established body of infoi-ination. Unless something is known of the variables that are most effective in maintaining behavior at a high level it will be impossible to eliininate unwanted vai-iability by the kchnique o f sti-engthening behavioral control (Sidman, 1960. p. 165).

Let us consider the problem of research on infant learning. The investigator must first choose a response t o be controlled. T o do this he must know something about the response capabilities of the organism. Once this choice of behavior is made he then employs the usual paradigms for conditioning. For a given subject, the results will often be quite variable over a series of sessions. 1 n some sessions, the experimenter will demonstrate good control; in others, he will have little or no control; in still others, he will lose the subject entirely. This could be classified as intolerable variability. Can we increase the subject’s level of food deprivation’? Perhaps, but if you are trying to control sucking behavior in a 2- or 3-month-old infant, a high level of food deprivation is more likely to increase crying behavior and produce a high rate of limb and trunk movements, the topography of which is very variable. Can we increase the intensity of aversive stimulation? Theoretically, yes. Practically, the ethical constraints and the willingness of the responsible caretaker(s) to permit the use of the subject strongly limit this alternative.

Can we increase the size of the reinforcement? Yes, this is sometimes feasible. However, with appetitive reinforcers, increasing t h e reinforcer speeds satiation, and one encounters the problem of reducing the length of the session. There is also much we do not know about the range of events that act as reinforcers for young infants. And, there is also the problem of functionally quantifying amount of reintorcement. Can we provide the behavior with an exteroceptive feedback'? Yes, although the problem just mentioned obtains: in addition, some exteroceptive stimuli are likely to function ;IS disrupters of behavior. The problem of attention in young infants is rclated to this and is more fully discussed below. Can we employ more easily discriminable stimuli'! Yes. although our knowledge of stimulus discriminability in young infants is, a t this point, meager. It is likely to be variable from organism to organism. In t h i s dimension the problem of matching stimulus value to the individual organism may be extremely important. This is a highly relevant empirical question. If individual differences in this regard are stable, then the use of standard stimulus conditions across subje'zts should serve only to increase variability. We shall return t o this point later and discuss it at some length for it is central to the issuc of individual differences and the role of stimulation in development. It is clear that in posing the questions above, the answers suggest partly that we just d o not have the available body of knowledge to employ the techniques proposed for eliniinating unwanted variability in an experiment. But, in part, the problem is more basic than that. Except for sleep, the young human infant does not have an obvious repertoire of responses that are maintained at a high level over an extended period of time. I n this sense, there is an intrinsic within-subject variability. Perhaps this variability means that many behaviors in the young infant are maintained weakly. If so, the problem of explaining the within-subject variability may be extremely complicated, because there may be a wide range of individual differences in the strengths of the variables that control the weakly maintained behaviors, and, in addition, there may be individual differences in the ways these variables combine to control given behaviors. Auditory, visual, kinesthetic, and tactile soi~rcesof stimulation are likely candidates as relevant variables: but how one determines the "amount" of each, the number that occurs at one time, and the degree of interaction among them are empirical questions for which there are presently no answers. The behaviorist generally takes the position that eventually the principles of learning will be shown to account for the behavioral development of an organism. Recent reviews of the literature on infant learning (Brackbill & Koltsova, 1967; Horowity. 1968; Lipsitt, 1963) clearly support the

generalization that the human infant is conditionable. But the degree to which all or much of t h e very rapid acquisition and elaboration of behavior can be demonstrated to fit a learning paradigm is another question. I t is an extremely important question because an affirmative answer for the learning side has socially relevant implications about the control of development and our eventual ability to insure that all organisms will show normal behavioral progress through the formative years. Learning in the natural setting probably involves variables which must be defined more molecularly than definitions used by psychologists. It is not sufficient to demonstrate only that the infant is conditionable. This is an important first step that has been taken. The developmentalist wants to know t h e conditions under which learning occurs and whether these conditions obtain in the natural environment of the infant. He must extract the conditions from the natural environment and simulate them experimentally. If the experiment, however, creates conditions that do not adequately represent the natural processes, then his success in conditioning is a testimony to his ability to manufacture behavior rather than a discovery of basic processes. The developmentalist must eventually be able to account for behavioral development under natural conditions if he is to approximate the technological success of other experimental sciences. Are we really just simply saying that there are individual differences, we do not know very much, and we have many problems'? Yes. but not simply. For there are more important implications in the prescription for research strategy suggested above. I t may be possible to engineer behavior to a high stable rate in young infants. But, if this rarely occurs naturall y , have we learned anything about the normal process of behavioral development? The kinds of questions asked by the two typical research strategies currently employed in experimental work (group design and single subject) are quite useful questions because the methods provide reliable kinds of information. But they are usually not concerned with systematically understanding the variables that control the individual's development. The group design asks whether certain variables are operating and whether they interact; the single subject design asks how, given a stable baseline, the rate of the behavior can be increased or decreased and maintained at a stable level. The first methodology usually demands standard stimulus conditions across organisms. The second strategy requires a stable baseline in order to demonstrate the ability of the experimenter to obtain a stable increased or decreased rate as a function of specific manipulations. In the early development of the human young, the conditions required by the second strategy may be very difficult to obtain and the ones required

by the first methodology may produce results that obscure some of the important variables. An understanding of development under natural conditions is presently not available. By a careful consideration of the alternative research strategies available, some significant steps might be taken in that direction. One of the most difficult problems in research with the young human organism is variability. This would suggest that one of the most important considerations in research should be the range and stability of individual differences. T h e point is that this consideration 11snot proposed in the traditional mold of differential psychology. Suppose one is bent upon investigating the role of reinforcement contingencies in the development of a particular response. Informal observations of both the sophisticated psychologist and the observant mother will indicate that the degree of stimulus intensity required to evoke a response varies from individual to individual. In the research question posed, the selection of a standard stimulus intensity is likely to work against the production of consistent results for all subjects. Yet, to abandon the group for the single subject is to give up the possibility of understanding the relationship of the level of stimulus intensity and the effectiveness of reinforcement contingency in any systematic way. The underlying assumption here is that there are principles of learning operating within a set of parametric values that will account for response acquisition for every one of a group of subjects. This assumption, however, is presently untested. I t can be tested by imbedding it in an experimental program of research. Thus, one must ask about the range of stimulus intensities that can evoke a particular response of a measured amplitude. One must investigate the variability within and between subjects. One can then describe the lawful relationships between conditions relative to the individual that brmg about response control. This may yield a much more powcrful research strategy, capable of producing results that will indicate the degree to which principles of learning can account for behavioral acquisition. I t is a strategy that incorporates variability as one of the parameters of the design. These suggestions are particularly relevanii to infant research because of the problems of general variability. rapid development, and widely varying general developmental rates. Age is a particularly dangerous variable with infants because of these factors. I t correlates grossly with many measures. Overlap between groups on measures often can be avoided only by large gaps between the ages chosen for comparison. If one assumes that response acquisition follows som'e sequence, then the niore important consideration is where in t h e sequence the organism can be placed. This kind of control is, of course, provided in the baseline mea-

sure used in operant conditioning, and it is an extremely important control. However, the typical measure used in operant conditioning is rate of response. Response rate may not be the most useful response parameter for understanding learning in young children. If, in fact, the natural setting involves distributed response opportunities, reliable trial responding may be a better baseline assessment procedure. Research with rapidly developing human organisms must take into account general environmental factors in selecting experimental paradigms and control measures. Those discussed above and some others we have not considered will become relevant as we turn now to a consideration of empirical findings. B. E M P I R I C SATLU D I M OF I N D I V I D U A L DIFFERENCES AND LEARNING

I t is difficult to find an extensive literature of systematic studies of individual differences in learning, particularly in the area of infant research. That the individual differences are very evident in all phases of research is almost a commonplace observation. T h e problems of control for individual differences can be found in the initial selection of subjects, in the amount of variability allowed to remain in standardized procedures, and, finally, in statistical treatments. Quite often the initial selection of subjects plays the largest part in this control. With unusual completeness, this is described in research reported by Caron ( 1967) on visual reinforcement of head turning in young infants: Not all infants brought to the laboratory were retained for experimentation. I n fants were excluded because they did not remain alcrt and content for the major part of the session or because they failed either to turn their heads in response to elicitation and/or to fixate the visual stimuli consistently for the duration of its exposure. This latter category includes some infants who appeared to be “locked in.” i.e., their heads remained fixated center or to one side, and neither auditory, visual. or tactile signals aroused head-moveinent. In others. inconsistent fixation resulted when hand gaze. hand 01- finger-sucking. o r hand-to-mouth movements preempted their attention. Many of these “rqjected” infants were seen twice and continued to exhibit behavior incompatible with head-turning and visual fixation. There was. in addition. some attrition due to I I subject‘s failure to adapt at the very outset to the experimental situation. o r to his inability to return for multiple sessions (Caron. 1967, pp. 49.5-496).

Caron went on to report the results obtained with t h e infants she did not reject and quite convincingly showed with both group and individual data the effective control of head turns when they were reinforced with an opportunity to fixate a variety of visual stimuli. By any criterion, the results are clearly an addition to our understanding of the variables that operate to control infant behavior, and the succeeding remarks are not intended to diminish this fact.

Caron’s re,sults indicated that in the sample selected for laboratory conditioning, success was achieved. Her results warm the behaviorist’s heart because they point to t h e important role of stimulation in reinforcement and to the possibility that varied stimulus change is a potent factor in early learning. Since this factor exists in abuindance in the natural environment and since it is easy to conceptualize that many such changes are contingent upon particular responses, the conditioning model accrues much more status as a valid mechanism. However, the physical scientist rarely must qualify his results by such extrernes of subject selection as the behavioral scientist. And, we should be more skeptical of his results if he had to indicate seven reasons for rejecting some of his sample because they were not amenable to the procedure which would demonstrate the relationship. That the relationship exists we might not doubt, but the generality of it would be open to question. It might seem eccentrically stringent to be demanding, in essence. one hundred percent success in an experimental procedure. However, the developmental behaviorist eventually seeks a high level of generalization. H e would not generally be willing to take the position that some subjects acquire behavior through conditioning anal others through some other process. Caron’s results imply a general statement for both the individual and group dat.a she presents. Hut. given the standard set of conditions employed, the relationship was not demonstrated over all the subjects who participated. In a footnote, Caron noted that some of the rejected infants might have been shaped to the point where they could have participated. This footnote is significant for our argument. What if, by some assessment technique, it could be demonstrated that a range of stimuli will be effective with some infants and another range or partially overlapping range with others. Then one could test whether or not the matching of stimuli to organisms resulted in the rejection of no subjtects or only a few subjects. I t is just this kind of dimension of individual difference that must eventually be shown to have a functional involvement in conditioning. Later. in a discussion of attention and elicitation of the orienting response, we shall see that it may be just such factors that can be shown to have reliable individual difference parameters which, if assessed, would yield more powerful analyses of learning and development than have heretofore been possible. Few studies of early learning specify the conditions for subject selection as clearly as Caron’s, although many note individual differences observed during conditioning. Papousek2 has indicated that the range of trials necessary for obtaining stable conditioning in the infants he worked ‘personal communication, I966

with was 70 to 300. At the rate of ten trials per day, that is a range of 7 to 3 0 days. It is generally agreed that in experimental work the state of the infant is very important in determining the success of conditioning. But, even partialling out state or controlling for it does not eliminate a strong individual difference factor. We have been discussing the problem of the interaction of organismic variables with environmental conditions that determine the outcome of a procedure. In general, we see much individual difference in outcome under natural conditions. I t is quite possible that the functional control of outcome will be understood only by demonstrating the role of parametric factors of individual characteristics in lawful relationships. Proposals such as these are not unique to research on children's learning. There are many instances in which measured individual characteristics were used as levels in an experimental design. These usually involved rather grossly defined variables such as anxiety (Horowitz & Armentrout, 1965), birth order (Gilmore & Zigler, 1964), age, sex, and intelligence (Meyer, Swanson, & Kauchack, 1964), or social class (Terrell, Durkin, & Wiesley, 1959). Typically, one or more of these variables was involved in a significant interaction. Such studies were tapping currently assessed status, implicitly assuming that it represented the summated results of a history of experience. This assumption is usually not testable in the context of the given experiment, but the behaviorist has a heavy investment in the faith that it is valid. T o the extent that the results of such studies are replicable, the investigator has demonstrated that these are variables to be considered. The investigator is primarily interested, in most cases, in demonstrating that the variable is effective rather than in understanding how it interacts with the experimental conditions to produce differential results. T o the extent that such studies have successfully identified relevant variables, they have made a contribution and it is not fair to criticize them on a criterion for which they were not aiming. Because variables typically included in studies of older children are harder to assess or are suspected of being weak in very young organisms (with the obvious exception of birth order), they are largely absent from studies of infant learning. While Brackbill and Koltsova ( 1967) indicated that Pavlov was very interested in the individual differences in his results and was concerned with the possibility of temperamental types, these factors have not been the subject of systematic investigation in Russian psychology. Except for the work of Thomas, Birch, Chess, Hertzig, and Korn (1963), not much attention has been paid to temperament in the United States either. lndividual differences in learning have begun to be of some interest in traditional studies of learning in older children. Zeiler's (1967) paper on

stimulus definition and choice, which appealred in Volume 3 of this series, is relevant to this discussion. In comparing group data with individual data in studies of transposition, he reported that the group data clearly replicate previously reported studies in showing the usual decrease in the transposition response as the distance of the test set increases. However, the individual data led Zeilei- t o a rather different result. I n one study he was able to distinguish four categories of individual response types (Zeiler & Salten, 1967). He also noted within-subject consistency in the face of between-subject differences. In another study, within-subject consistency was not present and individual behavior seemed to be a function of the child’s immediately preceding reinforcement history (Zeiler 81 Gardner, 1966). An attempt to overcome individual variation was made by the use of an instructional set (Zeiler 81 Salten, 1967). and its success suggested this technique as a useful one for reducing variability. I t would seem that such results are quite supportive of the argument proposed in this paper. However, Zeiler failed to consider some iniportant problems in his discussion. ‘fhe problerns are present in many studies with older children in which the phenomena being studied in the labor-atory are also under control of environmental shaping, probably on a much more distributed schedule. Within a group (of similarly aged youngsters, an experimenter will have sub.jects at many different points along the continuum of acquisition of the type of i’esponse he is attempting to study. The experimental manipulations must operate against this natural history of acquisition. which usually cannot be assessed. Zeiler’s general analysis of the differences between individual a n d group data and the implications for understanding children’s learning may be valid; however. his prescription was not to understand individual differences systematically, but to find ways of eliminating them. This will yield some general functions but will not tell us much about developmental process. There is much empirical evidence that individual differences exist, but there is not much systematic understanding of their lawful characteristics in the learning process. I n the introduction to an interesting volume of papers on learning and individual diferences (some of which are discussed below), Gagne ( 1967) makes the following observation: The questions of how people clitfei in the r,ite. extent, style. and quality o f their learning is one which has concet ncil p.,ychologists for a great many yeai-s. T h e history of investigation of this que\tton I S not i:hal.a(:terizetl by smooth continuous development. Instead, there have tcnded to be periods o f activity followed 17)’ rather lengthy periods o f inactivity. I t ‘ippcar-2 that for many years the tradition of intelligence testing seems t o have ca\t an crhscurin;; shadow o v e r the whole enterprise. Important practical result., Ii;i\e indeerl bccri itchieved by nieasui-ing intelligence. which by arbitrary definition can hc named “learning ability.” But it is questionable whether the good efTect\ of t h e w pi-;tctic;il w t c o r n e s balance the obstacles

to clear thinking resulting from a passive acceptance of this unsupported and unanalyzed definition. At the present time i t seems fair to say that we know considerably more about iearning, its var-ieties and conditions. than h e did ten years ago. But. we do not know much more about individual‘difference!, in learning than we O 1967. p. x i ) . did thii-ty years R ~ (Gagne,

The papers for which the Gagne introduction was written are primarily concerned with learning in mature organisms. If GagnC’s comments are appropriate to such research, they are even more appropriate to developmental learning research. We have only to note the broad range of rates of development of organisms from birth onward, even under relatively similar gross environmental conditions, to realize how little we understand the specific factors that determine individual developmental outcomes.

c. S O M E THEORETICAL APPROACHES The theoretical treatment of learning and the related research has generally ignored individual differences or excluded the subject from systematic research. The major exception to this has been Hull-Spence theory. I n a I945 paper on innate individual and species differences, Hull ( 1945) proposed two tasks for a natural-science approach to behavior theory: One task was to analyze basic behavior processes: the other was to deal with the problem of innate behavioral differences between and within species. He posed the latter task in the form of a question: “Given two rats with similar antecedent life histories, why can one learn a particular maze more quickly than the other?” (Hull, 1945, p. 55). Being primarily interested in innate and species differences rather than the cumulative influence of individual differences in learning, he proposed the following hypothesis: “Innate individual and species differences find expression in the empirical constants which are essential constituents of the equations expressing the primary and secondary laws of behavior” (Hull, 1945, pp. 56-57), This was reiterated as a theoretical postulate in a later publication (Hull, 195 I , p. 117). Hull recognized that the type of research needed to identify and understand these individual factors would need to be somewhat different from the traditional approaches, and some work relating to this problem is referred to as “ongoing” in Hull’s laboratories. However, no further mention can be found of the work, and one may presume that it remained uncompleted or did not yield any publishable results. Zeaman and Kaufman (1955) made one attempt to verify the role of individual differences as they affect the theoretical curves and concluded that it was possible to derive testable hypotheses from Hull’s theory regarding this factor. Spence ( 1956, 1960, 1966) also attempted to test t h e role of individual

differences in eyelid conditioning using gross measures such as manifest anxiety and factors of awareness. However, the actual program of research to identify the parametric function OF the constants was never undertaken. Interestingly enough, the research by Zeaman and his co-workers (House & Zeaman, 1963. 1967; Zeaman & Kaufman, 1955) has evolved in the direction that Hull was outlining as well as approximating some of the methodological procedures suggested in the atheoretical position taken by Skinner. The work incorporates :some attempt to identify the components of the learning process that can be given individual difference values and to use abbreviated baseline estimations from which to launch the experimental manipulation. Zeaman anld House (1963), along with Wycoff (1952) and Maltzman ( M a l t ~ m a n ,1967: Maltzman & Raskin, 1965), have honed in on orienting and observing responses as important individual difference characteristics in learning. This brings us to the whole area of orienting and attending behavior and its relevance to our discussion.

IV. Individual Differences and the Study of Attention A. THEO R I E N nwc, K F \ P O N \ F

AND

INFANT RESEARCH

The organism, from birth (and perhaps before), is an entity within a constantly changing flux of stimulation. Most of the surrounding stimulation is in the nature of background with a small percentage of the total physical complex making up ;I foreground. The foreground is functionally defined by the behavior of the organism, and its definition, for scientific purposes, involves stimulus components to ,which the organism is directing its behavior. The behavior may be producing this foreground stimulation or t h e environment may be introducing the stimulation into the surround or accentuating already present stimuli. Except for data from informal observations of infants made by Piaget and some of his followers, little is known about the behavioral significance of self-produced stimulation. Empirical observations and theoretical formulations both suggest that change in orientation and maintenance of attention are complexly involved in the learning process. These factors have been labeled as attending responses, orienting responses, and obscrving responses. The terms are not completely synonymous hut, depending upon the operational definitions used in a particular piece of research, they may overlap in meaning. Generally, orientation is limited t o behavior occurring just after the on set of ex peri mental I y cont 1-0 I I ed s t i in ti lat ion. whi 1e attention i s cons id-

ered in the context of more sustained regard by the organism. Observing responses range between the two. I t is quite possible that behaviors we grossly label as attending or observing will eventually be shown to involve the rapid succession of a multitude of orienting responses. This will not become a testable question until we have developed much finer measuring techniques than are presently available. For our purposes here we will discuss orienting and attending behavior as two separate but related kinds of event s . The orienting reflex (OR) has played a central role in Soviet research. The most articulate account of its definition and role in perception has been offered by Sokolov ( 1960, 1963). Basically, the reflex is a physiological reaction to incoming stimulation and has the role of “tuning” the receptive capacity of the organism. In their discussion of the orienting response and heart-rate change, Graham and Clifton ( 1966) offered the following explication of the orienting response: “The orientation class, or OR, is a system of unconditioned motor, autonomic, and central responses elicited by any change in stimulation, independent of stimulus quality. Thus, both heat and cold evoke an OR on the first presentation although, upon repetition, each evokes a distinctive ‘adaptation’ reaction. While derived from earlier work of Pavlov, Sokolov’s OR is more restricted than the relatively complex chain of conditioned and unconditioned exploratory investigatory reflexes described by Pavlov and is, in addition, explicitly related to the control of sensitivity to stimulation” (Graham & Clifton, 1966, p. 306). I n addition to the orienting reflex, Sokolov identified adaptation reflexes and defense reflexes. The adaptation reflex is exemplified by the common occurrence of pupil dilation in darkness. The defense reflex is similar to the orientation reflex in that it also serves to tune the organism to stimulation, but as the name implies it shields or protects the organism from stimulation. Sokolov distinguished two kinds of defense reflexes, the passive defense reflex, which immobilizes the organism as in ;I freezing fright reaction. and the active defense reflex, which is seen in behavior that results in the removal of or escape from the stimulation (Sokolov, 1963). The OR is distinguished from the defense reflex in its physiological characteristics. I t is typically elicited by stimuli of low or moderate intensity, while the defense reflex occurs when stimulus intensity is relatively high. Upon repetition of stimulation the OR habituates but the defense reflex intensifies. Sokolov has proposed that the OR facilitates perceptual learning. Neural cells preserve properties of applied stimulation and the OR is evoked when the neuronal model in the brain does not coincide with all the parameters of the applied stimulation. The OR results in this instance,

not from stimulation itself, but from impulses caused by the difference between the model and the stimulation. I n the case of a conditioned response, he proposed the converse to he true, i.e., that the evoking of a conditioned response occurs when the stimulation does coincide with the neuronal model (Sokolov, 1960). Lacey and his co-workers have suggested similar reactivity dimensions in terms of stimuli that result in either environmental intake o r defensive reactions analogous to environmental rejection (Lacey, Kagan, Lacey, & Moss, 1963). Thus, cardiac deceleration accompanies environmental intake, while cardiac acceleration accompanies rejection of the environment. A similar. but more general principle has been offered by Schneirla (1959): “Intensity of stimulation basically determines the direction of reaction with respect to the source and thereby exerts a selective effect on what conditions generally affect the organism. This statement derived from the generalization that. for all organisms in t h e early ontogenetic stage, low intensities of stimulation tend to evoke approach reactions, high intensities withdrawal reactions with reference to the source” (Schneirla, 1959, p. 3). The functional relationship of environmental stimulation to behavioral development involves organismic receipt of and reaction to the stimulation. Thus, the conditions of stimulus change necessary to evoke the O R probably are of central importance in the more generally defined behavior of attention and in the learning process. Maltzman has tried to show the role of the OR in conditioning the GSR in adults, with particular concern for the individual differences in O K . He rea’soned that the individual differences should result in differential conditioning and presented results that support his hypotheses (Maltzman, i1967; Maltzman & Raskin, 1965). Maltzman and Raskin ( 1965) suggest that secondary reinforcers are conditioned ORs and that they are mainlhined as the result of pairing stimuli that evoke stronger ORs. Human infants are bombai-cicd with stimulation in all sensory modalities. Evidence suggests that they are much more reliable discriminators of that stimulation than traditionally supposed (Bronshtein & Petrova, 1967; Engen & Lipsitt, 1965: Fantz, 1958; Fitzgerald, Lintz, Brackbill, & Adams, 1967). If the OR plays an important role in learning, then the question of individual differences in responsivity to stimulation is relevant. In fact, a number of investigators report strong and consistent individual differences in response t o environmental stimulation (e.g., Bridger & Reiser, 1959; Richmond & I>ustnian, 1955: Steinschneider, 1967). Consistency seems to exist within a given sensory modality for a given organism but responsiveness in one sensory modality is not necessarily correlated with responsiveness in another sensory modality

(Steinschneider, 1967). Eisenberg and her colleagues have reported reliable differences i n neonatal habituation to an acoustic pattern (Eisenberg, Coursin, & Rupp, 1966). Lipton. Steinschneider, and Richmond ( I 961) reported reliable individual differences in neonate cardiac reactivity. An abstract of a study by Mirroiants (1954) reported individual differences in the conditioning of an orienting reflex to musical tones in infants 4 to 5h months of age. Gewirtz has argued that stimuli for the child are functional when they are discriminable to him and are provided in effective temporal relationship to his behavior (Gewirtz, 1968). In looking at learning, its very early manifestations. and the enormous divergence in individual rates of development, one needs to gather information about the range. extent, and stability of individual differences with respect to both the orienting reflex and the defense reflex. I t is possible that herein lies the key to understanding variability in learning; a standard stimulus condition may be functional for one infant but not for another, or its intensity may be more functional for one infant than for another. The possibility of the laboratory control of dimensions and ranges of stimulation to test out this notion is very good. The probability that the natural environment provides a comparable situation is also high. Seen i n this context, the greater congruence of development of twins as opposed to nontwin siblings is not surprising. If the twinned organisms have greater resemblance in the levels of stimulation that will functionally control the orienting and defense reactions, one should expect greater similarity in development. The question is not one of heredity 11s.environment. Rather. can the nature of the interaction of organismic characteristics with the stimulation provided by the environment be understood? To the extent that the nature of self-produced stimulation is likely to be more similar in the twinned organisms than in the nontwinned individuals. there is also more cause for t h e greater similarity in development. The elicitation of the orienting reflex may be analogous to t h e colloquial notion of successfully “catching the attention” of the organism. There are many informal indications that the natural environment varies in its ability to do this and. further. that environments are modified in order to increase the probability that it will happen (witness the contrivances of any experimental laboratory setting). Undoubtedly. there are organisms for whom the degree of environmental modification necessary to elicit the OR is more drastic than normally takes place. T o the extent that this results in a failure to elicit the OR a sufficient number of times for effective learning to occur. abnormal or slow patterns of development should follow. We shall return to a discussion of the implications of this statement in a later section.

The conditions for successfully eliciting the orienting reflex in individuals and the conditions for maintaining the attention of the organism may or may not be the same. However. etfective maintenance of attention no doubt plays an important role in the learning process, and an examination of some of the dimensions of stirnulation that control attention can contribute to the analysis being proposed. B. A T T E N T I O N1,N I ) I V I D I I I DIF'FERF-NCES. AND

D I M E N S I OOF-N S Sr I M L J L A T I O N Since before William James' statement " M y experience is what 1 agree to attend to" (James. 1890) through Pillsbury (1908). the subject of attention has been more or less part of traditional psychology. I n recent years interest in attention has increased markedly (see Bakan, 1966; Berlyne, 1960). As indicated previously, attention is a general term and is variously defined depending upon the measurement operations employed by the investigator. Usually it refers to more sustained regard of the organism in relation to a particular stimulus than the orienting reflex. Of all the behavior of the various sensory modalities, visual attention is the most easily assessed, and it has been the subject of most of the research on attention. The normal young human organism is frequently observed attending t o visual stimuli. Aiiditory attention is more difficult to observe. The research reported by Eisenberg and her colleagues (Eisenberg, Griffin, Cour-sin, 6i Hunter, 1964; Eisenberg pt ctl., 1966) strongly suggests that the naturc o f the auditory signal and the characteristics of the neonate are two important variables. Some work with older children has been reported recently (Maccolby. 1967; Turkewitz, Birch, Moreau, Levy, & Cornwell, 1966). I t is possible that the dimensions of auditory stimulation that control attention may provide some understanding of language development. but little work seems to have been attempted in this area. The dimensions o f tactile and kinesthetic stimulation have been the subject of a limited number of investigations. Attending in these sensory modalities is le ipparent and is usually measured by physiological changes in the organism (e.g.. Steinschneider, Lipton, & Richmond, 1965). The recent work in infant visu;il attention has contributed significantly to changing the notion that the infant is initially thrust into a hazy, undifferentiated world. The pioneering work of Fantz (1958, 1963. 1964) and Berlyne ( 1958) indicated that i t was methodologically feasible to study infant visual attention reliably. They also set out some of the variables that appeared t o be in control of the behavior, stimulus complexity and stimulus patterning. Interestingly. Eisenberg P t (11. ( 1964) implicate pat-

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terning as a relevant parameter for auditory stimuli also. Lewis ( I 965) and Kagan and his colleagues (Kagan, Henker, Hen-Tov. Levine, & Lewis, 1966) have used the “meaning” of stimuli as a relevant dimension of stimulation. A critical examination of the response measures used in research on infant visual attending suggests that a multivariate L-tpproachmay be a most valid measurement procedure (Lewis, 1967; McCall, 1967). Two specific kinds of research in this recently burgeoning field are relevant to our discussion. One concerns individual differences and the other developmental patterns. Individual differences in attention behavior, as in more general infant learning behavior, are clearly apparent. I n one of the few studies specifically concerned with individual differences, the focus was upon the value of the neonatal APGAR score for predicting attention in infants within the first year of life (Lewis, Bartels, Campbell, & Goldberg, 1967). Another attempt to study individual differences was related to the question of the usefulness of multivariate measurement in research on infant attending behavior (McCall & Kagan, 1967). Developmental patterns of attention have received more attention. Developmental trends appeared early in Fantz’s work (Fantz, Ordy, & Udelf, 1962) and have been repeatedly reported by Fantz and his coworkers (Fantz & Nevis, 1967). Developmental changes have also been reported by Brennan, Ames, and Moore ( 1 966). In addition, preferences among visuhl stimuli are found in newborns and older infants when the stimuli are systematically varied in one dimension (Hershenson, Munsinger, & Kessen, 1965; Spears, 1964). The interpretation of developmental patterns of preferences for visual stimuli is difficult, at best. The apparent consistency of Fantz’s findings may be affected by the manipulations of the data to produce smooth curves (Fantz & Nevis, 1967). Fantz makes little of individual differences in his data. Other reports indicate some developmental patterns, but the findings from one study to another are not entirely consistent. Generalizations found in the literature indicate that infants look at more complex rather than less complex stimuli (Berlyne, 1958), newborns prefer the least complex stimuli (Hershenson, 1964), and newborns prefer shapes of intermediate complexity (Hershenson rt al., 1965). Reported developmental changes have been difficult to understand because the stimuli employed are not similar from one study to another, nor are they usually carefully ordered on a single dimension. What, exactly, would be the implications of reliable developmental changes in preference for visual stimuli? Perceptually, it could be argued that the infant is very busy observing the consistencies and regularities of his perceptual world-that he is learning to sort out perceptual stability and is consolidating impressions and sensations into perceptual units.

[This point of view would be close to some of the proposals of Hebb (1949).] In a related fashion these changes might reflect associational learning relative to a secondary reinforcement paradigm. The infant learns to attend to those characteristics of the visual stimuli that have been associated with reinforcement. ‘The work of Kagan ef al. ( 1 966) on the development of facial schema and meaning in a stimulus is partially directed toward this kind of reasoning, although these researchers might not put the emphasis on the reinforcement paradigm as much as upon the schema notion. From another perspective, the changes in attention might relate to increasing familiarity with the simple components of visual stimuli and the tendency to seek out more and more complexity, pattern, and novelty. These notions are compatible with some of Berlyne’s ( 1 960) thinking. Last, the visual stimuli to which the organism attends and the developmental changes observed may have a genetic base with the progression of changes preprogrammed in the organism. The data on developmental changes are not consistent nor are they, at this point, sufficiently extensive to give any hints as to the sources of the inconsistencies. Part of the problem can be attributed to the many differences in stimuli and general experimental procedures. Further, the nature of the developmental comparisons - cross-sectional 1’s. longitudinal - has not been consistent. One of the more carefully executed studies of developmental changes in attention to visual stimuli was reported by Brennan et af. ( 1 966). They studied visual fixations of 3-, 8-, and 14-week-old infants using three black and white checkerboard patterns and a gray stimulus. The study was cross-sectional, since the infants at each age group were different individuals. The checkerboard stimuli were varied along one major dimension, number of checkerboard squares. The checkerboards were 2 x 2 , 8 x 8, or 24 x 24. Each stimulus was the same overall size and was presented for four 30-second trials. Figure I presents the results. It is clear that a developmental pattern was demonstrated in the group data. I t was concluded that 3-week-old infants preferred the least complex of the stimuli and decreased their looking time as the number of checkerboard squares increased. The intermediate age group preferred the intermediate checkerboard square, and the oldest age group showed increasing preference as number of checkerboards increased. The gray square was the least preferred by the 3- and 8-week-old infants (it was not shown to the 14-weekold infants). N o mention was made of any individual differences, but statistical analyses of the group data were signifcant. The orderliness of these data is very appealing. As the authors themselves noted, the underlying mechanism controlling these developmental changes is not apparent. There is a rather fascinating implication in the

I04

results. One assumes that the checkerboard squares were arbitrarily chosen. Yet, the group results indicate clear preference differences relative to age. Were the findings a function of the ubsolutc. quantitative characteristics of the stimuli? If so, the investigators made a particularly propitious choice. O r were the infants making rrliitive choices from an array of successively presented stimuli? This would be rather sophisticated behavior. I n our just-born infant laboratory at the University of Kansas, it was feasible to conduct experiments aimed at some of these questions.:' The first question concerned the relative 1's. absolute choices of the infants. Thus, the stimuli employed by Brennan and her colleagues were supplemented in such a way as to fill in the distribution and extend the range and number of checkerboard squares. I n addition to the 2 x 2 , 8 x 8, and 24 x 24 square stimuli, the following stimuli were used: 4 x 4 ; 16 x 16; and 32 x 32. The second question pertained to the problem of developmental changes. Infants develop very rapidly and at widely differing rates. As "The tirst study was conducted by Mrs. 1.illinn Morrow for her Master's thesis. T h e data presented in this paper were collected for Rli-a. Morrow's thesis by MI-s. Morrow and a dedicated infant research team. I.ucile Paden. Patricia Self. Hob Aitchison. and Kastoor Bhana. Harold Stl-ang and Saundra Silverman Scott participated in the early 5taSes of the development of the laboratory.

was pointed out earlier, because o f this fact age is not a particularly useful variable. A cross-sectional sample of infants across a limited age span may be a very suspect procedure for getting at developmental patterns. Therefore, it was decided that the study should include a longitudinal sample tested every week starting at 3 weeks of age and continuing until the fourteenth week. As a check and replication procedure ;i cross-sectional sample of 3-, 8-, and 14-week-old infants was also included. The third question was concerned with the degree of individual differences that would be found. This question involved no special procedure. I n this respect the research was concerned with some of the same problems Zeiler has cited, which were discussed in an earlier section of this paper. We attempted to replicate the procedure of Brennan c t 111. ( 1966) as closely as possible using a 30-xconcl presentation of the checkerboard stimuli. The only difference was that the monotone gray stimulus was included in every session for all subjects. The results provided some interesting comparisons. First. the longitudinal data from infants J. K, and L are shown in Fig. 2, 3. and 4. respectively:’ The graphs are plotted for each of the stimuli each week (solid line) and for the stimuli that replicate the conditions of the Brennan r’t a / . ( 1966) study (dashed line). Figures 5 , 6, and 7 show the longitudinal data for each of the infants graphed only for 3, 8 , and 14 weeks. with the full range of stimuli shown in the A portions of the figures and the stimuli exactly duplicating the conditions of Brennan r t i t / . in the H portionc. Inspection of the figures for the three patterns of response that Brennan and her colleagues reported brings out mixed results. In Fig. 2. infant J never showed the 3-week pattern of decreasing fixation time as a function of increasing stimulus complexity. Possible but not strong exceptions were at the fourth, sixth, and the eighth weeks where the dashed lines show a tendency toward this genei-alization. Infants K and L never showed such a pattern at any week (scc Figs. 3 and 4). The typical %week pattern of relatively greater attention to the stimulus intermediate in complexity appeared somewhat more frequently for each infant. Infant J showed this pattern ( i n the dashed lines) at 3. 5 . 9 , 10. and 13 weeks. However, the solid line showing the pattern for all the stimuli used indicated that the result was not generally replicated. Infant K showed relatively greater attention to the stimulus of intermediate complexity a t the ninth and tenth weeks i n the dashed lines but only at the eleventh week when all the stimuli were included. The data of infant L ‘In or-der to keep the figure\ o f oui. tlal;i cc>mp;ii-;ihleto the figure fi-om the Hi-ennan ef C J / . study. the results for the monotone grrik stiniulri\ are graphed as the L i h t point. I his should he kept in mind when looking at genei-al i-espoii\e patterns along the complexity dimension.

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Frunces Degen Horowitz

revealed such a pattern at the third, fifth, and seventh weeks in the dashed lines but only at the tenth week in the solid line. The pattern for the fourteenth week in the data of Brennan et al. ( 1 966) is the most frequent. The data of infant J showed this pattern at the seventh, eleventh, twelfth, and fourteenth weeks in the dashed lines and at the eleventh, twelfth, and fourteenth weeks when all the stimuli are included. The data of infant K showed this pattern at the eleventh, twelfth, thirteenth, and fourteenth weeks in the dashed lines and at the thirteenth and fourteenth weeks in the solid lines. The data of infant L revealed this pattern at the sixth, eighth, ninth, tenth, eleventh, twelfth, thirteenth, and fourteenth weeks in the dashed lines, but only at the eighth week in the solid lines. The best conclusion that one can draw from these data is that the infants were extremely variable in fixation times for these stimuli. The other possible conclusion is that at the fourteenth week, considering the stimuli that replicate the work of Brennan et al. ( 1 966), all three infants showed a rather clear increase in fixation time as a function of increased stimulus complexity. Figures 5,6, and 7 indicate this. So much for individual data and variability. Figures 8 and 9 show the group data for the longitudinal group and for the cross-sectional groups. The cross-sectional groups include six subjects at 3 weeks, eight subjects at 8 weeks, and seven subjects at 14 weeks. Three of the six 3-week-olds are the same subjects who continued on as the longitudinal subjects. In Fig. 8 the data are graphed for the six 3-week-olds and then for the three who were subsequently longitudinal subjects. At 14 weeks the data of each subject in the longitudinal group showed an increase in fixation time with increasing stimulus complexity, replicating the trend obtained by Brennan et al. (1966) at 14 weeks. The same trend is apparent at 14 weeks in the combined data of the longitudinal group (Fig. 8) and in the combined data of the 14-week-old cross-sectional group. However, at 3 and 8 weeks, the trends in the data of the individual subjects were not reflected accurately by the grouped data and did not replicate the trends obtained at these ages by Brennan et al. ( 1966). The questions this research was designed to ask have been answered, but in no simple systematic way. In these results neither the relative nor absolute characteristics of complexity of the stimuli were functionally controlling visual fixation behavior, with the possible exception that fixation increased as the stimuli increased in complexity. However, this was clear only in the fourteenth week data. Does this suggest a developmental phenomenon? Unfortunately, no such conclusion is possible. Some infants showed this pattern earlier than 14 weeks but not consistently. If it

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variable and that only as a history is accumulated does there develop a base of stability. If this is so, more replicable developmental patterns should appear with older infants. Unfortunately. there are no systematically collected data related to this. Within this possibility is the likelihood that individual variability may decrease and relatively stable individual differences might begin to appear ;ISa cumulative base history is acquired. The possibilities just mentioned avoid a more basic problem in trying to understand the dimensions of stirnulation which control attending behavior. Methodologically there is reason for abstracting stimulus dimensions and varying them in some systematic way. Yet, the strength of the individual differences in the data suggests that we have not tapped the dimensions that are in systematic control of the behavior. A more appropriate question might be one that tries to determine some way of identifying these dimensions of stimulation. Then the problem becomes one of understanding how to extract orderliness fruitfully. Is it a matter of stable individual differences within an oi-dered dimension with the ordering of the dimension uniform across organisms? 01. is it a matter of individual differences in the ordering of the dimensions themselves? I n t h e natural setting infants “pay attention” to many stimuli in the environment. These are often stimuli for which there is no history of association and for which no reinforcement contingencies could have been established. The most easily ohserved instance of this is attending to naturally occurring sounds and the presence of toys. We have no data gathered in such settings that provide us with a picture of the distribution of attending behaviors or of the range and dimensions of the stimuli that elicit them. There is also abroad in the world of informal observations testimony suggesting that individual patterns of attending behavior become somewhat clear to a consistent caretaker. In our laboratory we sometimes find that it is difficult for two observers t o make a reliable observation of a particular infant, even though the observers have been trained to a high criterion of reliability (.90 or over). When such infants return to the laboratory more than once, observers usually show an increase in reliability. One suspects that the observers learn t o utilize the cues that a particular infant offers in the situation. From some infants, reliability is extremely difficult to obtain. Meyer and Cantor ( I 966) reported a similar finding. There is obviously much to be learned about t h e controlling dimensions of stimulation, the developmental patterns if any exist, and the extent of reliable individual differences.

I14

Frances Drgen Horowitz

The data reviewed in this section and the brief discussion of them bring us to the question of attention and learning, and we turn now to that consideration. C. ORIENTING, ATTENDING, AND LEARNING The typical learning paradigm includes at least two components - the stimulus and the response (affectionately known as S-R). An expansion of these components reveals that the stimulus is objectively describable on a number of dimensions and that the response involves a number of motor behaviors. How many and which of the stimulus dimensions functionally control the behavior is a relevant research question. How many motor acts are involved in the response is also an empirical question. Difficulty is encountered in a learning analysis of response acquisition in the clear specification of the functional relationship between parts or the whole of the stimulus and parts or the whole of the gross response. With the addition of another event - that of reinforcement - the picture is further complicated. Objectively, reinforcement is a stimulus event. As a stimulus event it has in common with the first stimulus event mentioned (the S of S-R) the possible fact that its occurrence must also be hooked to an R. Thus, the paradigm might more appropriately be described as S-R-S-R where R in both cases involves a presently unspecified series of motor acts. If we cut a slice out of the ongoing behavior of a typical infant, the following sequence might be observed: S (multicolored ball)-R (visual fixation on the ball, reach out and touch the ball)-S (tactile stimuli from touch of ball, visual stimuli of multicolored ball, kinesthetic stimuli from movement of arm)-R (visual fixation on the ball, visual tracking of the movement). The second S-R sequence is entirely in the realm of attending to the object. One could propose that the reinforcing event involves stimulus change accompanied by orienting and attending behavior. One need only observe the young human infant to realize that the sequence just described is a frequent one. Furthermore, the motor component of the response may often include only orienting and attending. I t could be that stimulus change acts as a reinforcing event and is a particularly effective controlling variable for maintaining attention in the young human organism. As suggested earlier in this paper, the experimental analysis at this level involves more molecular control and manipulation of events than psychologists normally undertake. Custom, however, is not a sufficient rationale for scientific practice, and if we are to increase significantly our account of early development within a learning structure, this level of analysis may be mandatory. Yet, it might be argued that a more gross analysis has already proven useful in bringing behavior under control in the laboratory (e.g., the successful conditioning studies of newborn infants). The argument is valid on

two grounds: Such demonstrations at-e partial models of the conditions under which learning can occitr: such demonstrations indicate the conditions that can be used to exert control over the organism. Neither of these necessarily answers the question concerned with the full range of naturally occnrring events that control response acquisition. It is clear that no infant ca,-etakercompletely controls t h e acquisition of responses and that critics of S-R are right in suggesting that the environment j u s t does not consciously provide all the socially mediated reinforcement contingencies necessary to account for the complex and rapid development of the human i n f w t . On the other hand. rcinfoi-cement seen from the point of view of stimulus change and responding broken down into motor components involving the orienting reflex a n d attending behavior probably occurs with high frequency. Because of the stnhle physical laws of our universe, many of the necessary events in thew minute chains can be counted upon to occur with great reliability. Watmn (1966) has proposed a parxiigm that is quite compatible with this proposal. H e has suggested that events that are consequences of responding will act as reinforcer4 only if the condition of “contingency awareness” obtains. Contingency awareness is defined almost in trace terms. Consequently, a response followed by a stimulus must be repeatable before the awareness of the contingency has faded. In effect he is suggesting that there is a critical period for the distribution of trials. and, if response repeatability is sufficiently delayed, the previous reinforcing stimulus will lose its contingency effect. If Watson’s hypothesis should prove correct, then it will help u s to understand some of the things involved in the sequences of response acquisition. I f the 3-week-old cannot smoothly and quickly repeat i i foot hick of a certain force directed at a panel, the likelihood of the or-ganism‘s “holding“ the relationship of the reinforcer to the response diminishes. With increasing age. the ability of the organism to maintain an “awareness” (perhaps due to neurological changes) of t h e contingent relationship over a longer period of time increases. The organism also becomes capable of faster “recovery” and hence possible repetition of the response. The orienting reflex and many kinds of attending behavior are responses that can be performed frequently, and from birth, and that d o not require much recovery time. I n this case, “rate” may be a very appropriate measure. Many behaviors discussed s o far are known to involve stable individual differences. If the evidence continues to support this, then it is clear that the rate of response acquisition should be expected to show reliable individual differences. One must not, however, be eager to arrive at a simple picture. There is some evidence to suggest that while infants show stability within a given sense modality, there is little correlation across sense modalities (Bridger. 1960). This suggests that each organism is to be

found at some point along a continuum with regard to a particular sense modality and that the points will differ with each modality. Thus, behavior that is dependent upon the visual modality may develop in a particular infant much more rapidly than behavior dependent upon the auditory or tactile modality. Behavior that depends upon several modalities should be expected to develop with greater variability, the greater the heterogeneity of reactivity across sensory dimensions. It is likely that the proportions of sensory information in each modality necessary for response acquisition vary with the particular response involved. The picture may be complex in the extreme. Probably much early learning is facilitated by the fact that the environment adapts to the characteristics of the individual infant and in effect makes some attempts to match the eKective stimulation to the organism. That mothers do this in a variety of ways is apparent to the casual observer. One adjusts the level of tactile stimulation, the speed of kinesthetic changes, the speed with which stimulation is repeated, the intensity of stimulation, the amount of stimulation in various modalities, and so on. The frequently observed lag in the development of institutional babies may be partially a function of the fact that a less than optimal amount of this kind of matching adjustment occurs across a large and sometimes inconsistent set of caretakers. Out of every so-called impoverished environment or institution, individuals result who function at normal and sometimes superior levels. For them, it might be proposed, the conditions that existed were adequate matches and functionally allowed for adequate or superior behavioral acquisition. Many psychologists interested in learning do not think seriously about development and are not concerned with accounting for the rapid or sequential acquisition of responses in the young human organism. The view of early development presented here is entirely compatible with a learning analysis. I n order to enhance the compatibility, however, it is important to understand the constraints of inquiry. Too often we ask very gross questions and pick variables that recommend themselves because of their quantifiability rather than their relevance. This “complaint” is not a criticism of highly controlled laboratory studies of infant learning. Charlesworth’s comment, that the probability of an infant’s learning under conditions similar to those in the typical infant conditioning laboratory is zero (Charlesworth, 1968), reveals a misunderstanding about the multipaths in science. The probability that a n omega particle ever has the opportunity to exist naturally in a bubble chamber is also zero. Yet, we would hardly maintain that the behavior of the omega particle under such conditions does not contribute to a scientific understanding of the phenomenon. The conditioning-paradigm studies ask one

kind of question. What is being suggested here is that we must also ask some other kinds of questions if the S-K claims are to be adequately tested. Neither articulate belief nor vigorous denial, by themselves. will accomplish the task.

V . Some Implications A. T H ECONCEPT OF

('APAC I

ry

IN

DEVELOPMEN I

In the opening of their chapter o n infant conditioning and learning, Brackbill and Koltsova ( 1967) commented: "The infant's genetic makeup will ultimately set the limits on the extent to which his behavior is modifiable but at this time of life his susceptibility to the effects of environment, of experience, of learning is enormous" (Brackbill & Koltsova, 1967, p. 207). The reference to genetic makeup in this quotation is similar to many references to the notion of capacity when the assumption is that some limits have been set for the organism in terms of eventual level of development. Reference is often made t o the judgment that a particular person is working below or up to capacity, as if somehow a measure has been made of these limits and we can now evaluate the performance in terms of its distance from the limits. I n fact. however, the measured limit at best refers to a score on an IQ test. Often it refers to an observation that on some occasions the individual performs at a much higher level than his average performance. Sometimes, the statement is based upon a set of unspecified cues and is summed up by the comment which has graced thousands and thousands of report cards: "He could do better!" The concept of capacity, however, is a troublesome one and is one that is often unexamined by the learning psychologist. Given an interactionist position, that it is heredity and environment, A and B, respectively, and given an arbitrary multiplicative relationship A times B equals C. it is clear that except where A equals zero, C may take an infinite number of values. Given a value of C, the lower the value of A the higher will have to be the value of B to achieve that level of C, and vice versa. The factor of heredity, however, involves two dimensions. One is the presence or absence of tissue in the organism. The second is the descriptive characteristics of that tissue. The absence of tissue is analogous to a zero value. Development with one of the necessary ingredients missing would involve definite limitations. I n human development, some tissues may take over the role of other tissues, often bringing lesser qualifications into the interaction in such a substitution. N o one would argue with the proposal that the wholesale absence of essential tissue involves a poor prognosis

for development. On the other hand, the characteristics of the tissue involved in development are of prime importance for prognosticating development in the usual sense ofthe use of the term “capacity.” If, however, we regard the interaction of our A and B factors as involving relatively unlimited manipulations in the regulation of the value of B, then t h e role of A in limiting developmental outcome becomes less crucial. Capacity, under these conditions. loses its role in determining the level of development. Instead, the level of developmental outcome rests upon the nature of the interaction, in which the hereditary factor assumes importance because of its relationship t o the environment. A concrete example may be of some help. We know that a given level of auditory stimulation will result in variability of responses across a sample of organisms. As suggested above, individual differences in orienting and attending responses quite probably play an important role in learning and in the rate of learning. Thus, we should predict that under standard stimulus conditions a stable amount of variability will be produced in a given sample of individuals. Suppose, however, that one could determine the level of auditory stimulation that most easily facilitated an orienting response in a particular infant. In conditioning a response to auditory stimulation, the speed of conditioning should be altered by matching the stimulation to the individual. Thus, hereditary characteristics in this case do not determine the outcome but an interaction of hereditary characteristics and en v i ro n me n t al c ha rac t e ri st i c s . Many of our references to concrete illustrations have relied upon the physical characteristics of stimulation. I t is possible that the pacing of stimulation is also an important dimension. Most good speakers know the importance of pacing their oral delivery to the estimated ability of their audiences to process the information given. In addition to choosing terminology and illustrations, a professional person will pace his delivery to an audience of peers somewhat differently than to an audience of laymen. Casual observation of natural environments reveals great variability in the rate of occurrence of stimulus events. Effective environments possibly are ones that partially control the rate of stimulus presentation for maximum impact. If we assume that adequate pacing of stimulation is an important parameter, it is also obvious that. particularly with the human infant, there is much self-produced stimulation. To t h e degree that the organism can pace his own stimulation, that aspect of his development is in his control. If some of what has been said about the organism “seeking” optimal stimulation is valid, then to the extent that the organism can pace his own stimulation, certain aspects of his development should be adequate (leaving the definition of “adequate“ aside for the moment). T o the

extent that the infant lacks this control in an area. the role of the pacing of environmentally provided stirnulation becomes important for developmental outcome. From this perspective, behavioral development that depends upon self-stimulation is relatively insured for the unrestrained organism. Behavioral development that does not depend upon self-stimulation would be determined by environmental control. If we assume with Brackbill and Koltsova (1967) that the potential effects of the environment are enormous. then the concept of capacity under the point of view just outlined is descriptively useful only under stand a rd st i m u 1us cond i t i o ti s :I c 1.0 s s organ i sms . Such st an dard conditions rarely if ever exist in the natur;il environment. The interaction o f hereditary factors with environmental i;ictors is d w a y s occurring. In addition to the implications that this obser\,;irion has for fruitful research directions ;IS discussed in earlier sections o f this paper. the implications for the control of developmental outconic arc significant.

The often reported finding that identical twins resemble each other more than fraternal twins. M h o . i n turm, show greatet- resemblance than nontwin siblings, has been crtcil :IS ccidcnce that the genetic constitution provides the limiting conditionr lor-dcvclopmental outcome. Such results are not inconsistent with t h o position proposed in this paper. As menti o ned ea rl ie r, u nd e r re I ii t i v c I ! \ i rn i 1:I r c n v i ro n me n t a I con d it ions , c I o se r concordance in clevelopmencal outcome yhould be expected. the greatett he p h y s i c al s i mi 1ai-it 4 between t ) l'g:I n I s 171s . The c r i tical q 11e st i o n con c e t-ns those dimensions of environnit.rit tlriit make a difference in controlling development. .[-he specifcLitioii o i thc controlling variables and the mechanism of the interaction with oipinismic characteristics may eventually I ead to v e I- y pow e rfu I too I s fo r c t ) n t ro I I i n g the d e ve I o p me I 1 t a 1 p roc e ss . Such control has aIr-e:idv hcen tletnonstrated in the partial success of adj ti s t i ng the de v e I c) p me n t :I I ( 11 I i()m e :Itiio ng chi Id re n i de nt i ti e d its p h e n y I ketonuric (Berman, Waisman. M Cirahani, 1966). I n this case the o b s e r vation of a metabolic condirion t-esults i n a dietary prescription that, fotso me i n d i v i d ii a Is . drastic ii I I \) :I I t c r s :in o t h e 1-wi s e bleak de v e I o p me n t al prospect. In ;I methodologic~illq siiiiilat- vein. the proposition implied throughout this paper is that, whcn M c understand t h e interactional mechanisms of the organism and thc environment, an alteration of the environmentally supplied diet of stiniulalic.~nshould result in control o f developmental outcome. Such ti propos;il is r i o t new and is directly and indirectly implied in many parts o f the pq\,ctiologic:il liternture. Certainly this is the

underlying thesis of much social experimentation now being done in early enrichment programs provided for populations whose members make up a large part of the low end of the distribution of social and intellectual functioning. These programs are, however, extremely gross and have adopted, for the sake of expediency, a general shotgun approach. The results of studies of early stimulus deprivation range from the destruction of unstimulated organs to partially and completely reversible effects. The early work of Riesen and his colleagues (Riesen, 1961) indicated much dysfunction in light-deprived chimps. When conditions of full daylight stimulation of vision were restored, the vision of the chimps improved but never caught up with the vision of normally reared animals. Yet, taken in the context of the present paper, it probably does not make sense to talk of general stimulus deprivation. Rather, the more adequate conceptualization may be one of functional stimulus deprivation in which the stimulation is either physically absent, or when physically present is not in interaction with the organism. The results of absence or noninteraction should functionally be the same. The organism will not show expected response acquisition. In human development the range and rate of development are highly variable. Most organisms develop “normally.” The normal classification, however, is extremely wide and within it are an enormous number of describable individual difference outcomes. For the most part these differences are not judged to be serious and after a certain period of lime are hardly worth identifying. Some children learn to read at 4, others at 6. The 2-year difference by itself is only grossly related to later intellectwl functioning. Whether to manipulate this behavior so that all children learn to read at 4 is a choice that a society and an educational system must make on the basis of their own value systems. A 2-year difference in a behavior occurring earlier in the sequence of development portends a more serious implication. The long range differences between the child who leal ns to sit at 6 months and the child who learns to sit at 30 months is quite a different matter. This lag in this kind of behavior, occurring so early in the developmental process, provides a good prognosis for t h e organism ending up in a retarded classification. Retardation is a relative classification and is always made on the basis of defined normality. Bijou ( 1 963) has made a cogent case for using the term developmental or behavioral retardation rather than mental retardation or mental deficiency. In another context, Horowitz ( 1 965) has suggested the relevance of individual differences to behavioral retardation, and the general points are pertinent to the present discussion. Briefly, retardation should be the expected result for an organism when the func-

tional stimulus conditions are not present at a level sufficient to provide for normal response acquisition. ' f h e apparent tautology of this statement belies the implication for control that would be available if the nature of the functional interaction between stirnulation and organismic characteristics were understood. Then, just as one can prescribe an adequate dietary control for phenylketonuria, so one could prescribe an adequate (functional)diet of environmental stimulation. The prevention of developmental retardation thus would become a possibility, however distant considering our current state of knowledge. Prevention is possible only when necessary neurological tissues are present. Since the largest percentage of identified retardates exhibit no gross neurological tissue absence. the population to which these suggestions are applicable is significantly large. If, as Hull suggested (Hull, 1 W 5 ) , individual differences affect the constants of a functional relationship rather than its form, then the values of t h e ultimate level of development will be determined by individual differences. If they can become the measure for manipulating environmental stimulation, then the eventual level of functioning of the organism may be controllable. Since early human development is extremely rapid, the point of effective control may need t o be very early in the process. This raises the question of reversibility, a question for which a cleat- answer is not presently possible. Reversibility is perhaps not the most useful term. for it implies a turning back of effects. Rather, the question might better ask where in the developmental progression it change of conditions is likely to produce only limited results. We know that even with severely retarded youngsters, operant conditioning techniques can produce behavior once thought to be impossible. However, it is one thing to teach a 10-year-old retardate to petform a behavior no one thought him capable of performing, and another to teach him to behave so that he is indistinguishable from his normal age peers. The relative plasticity of the organism for behavioral change is an interesting matter. It can never be proved that complete plasticity ever ceases to exist. However, it is probably safe to say that the earlier one institutes prescriptive stimulus conditions for behavior, the greater the likelihood of success in insuring normal development. The regulation of behavioral development depends upon an understanding of what constitutes functional environmental stimulation for an organism. In turn this probably rests upon a methodology for identifying the parameters of individual difierences in learning. The identification of these parameters has a twofold implication. One is in leading us to a more complete understanding of the laws of learning in human development. The other is in the application of such knowledge to control developmental outcome.

VI. Summary This paper has ranged over a set of topics that do not often occur together in the traditional literature. Many of the ideas presented here may be interesting more for the implications caused by their rearrangement than hy their novelty. They are not new. and even the implications are to be found in many current sources. Jeffrey ( 1968) has indicated the importance of the orienting reflex and attending responses in the development of response chains in learning. Hunt ( 196 I ) , Kiesen ( 196 I ) , and Thompson and Schaefer (1961) have discussed the role of stimulation in early development. Cjewirtz ( 1968) has talked of the role of functional stimulation. 'rhomas and his colleagues (Thomas cf d.,1963) have reported on individual differences in temperament. Some of their reported findings are relevant to this paper, although most of the work has been concerned with identifyingcharacteristics of individual temperament. Certainly the broad position of the interactionist is not new. As suggested earlier, it is not a matter of bringing the environmentalist and constitutionalist views into balance. Rather. it is a matter of identifying, on a more molecular level, the sources of control of the developmental process. The process has been assumed by many to involve a basic learning paradigm, but it must be understood in terms of the organismic variables loosely referred to as individual differences. It has been suggested that such a position has important implications both for the design of research and for the concept of the control of developmental progress. Matters of behavioral sequence and the problem of accounting for them have been left for another occasion. H F. FEK E NC ES Anustasi. A . liidividriecl diffewrices. New York: Wiley. 1965. Hakiin. P. (F.d.)Attcvitioii.Princeton. N.J.: Viln Nostnind. 1066. Wanduni. A.. & Walters. K. 11. Sociccl leuriiin~cirid prr.wiicrlif.v dewhprwrif. New York: Holt. Kinehart & Winston. 1963. Hcrlync, D.E.The influence of the albedo iuid complexity of stimuli on visu;il fixation in the human inkint. British Jortrird r ~ f P s y c . / i ~ i l o ~I95X.1Y. y. 3 15-3 I X. Hrrlyne. D.E.Cotflicf.crrciitsccl cord c.itriruit.v.K c w York: Miicmilliin. 1960. Berman, P. W.. Wiisman. H . A.. & Graham. I:. K. lntelligcnce in trciited phcnylketonuric children: A developmental study. Cliild Dcwloprnrtir. 1966. 37. 73 1-747. Hijou. S. W. Theory and research in ment;il (dwclopmuntiil) retardation. IJ.s.schrIiigical Hrc.cird. 1963. 13.95-I 10. Hijou. S. W.. & h e r . D.M. Some methodologioitl contrihutions from ii functionill analysis of child development. In I.. ID. I-ipsitt & J. 270-276. Hershenson, M.. Munsinger, H., 61 Kessen, W. Preference for shapes of intermediate variability in the newborn human. Science, 1965, 147,630-63 1. Horowitz, F. D . Theories of arousal and retardation potential. Mental Retmdution, 1965. 3 , 20-23. Horowitr. F. D. Infant learning and development: Retrospect and prospect. Merrill-Palmer Quarterly. 1968, 14. 101-120. Horowitz. F. D., & Arrnentrout, J . Discrimination learning. manifest anxiety, and effects 1965, 36, 73 1-748. of reinforcement. ChiltlDe~~elopment, House, B. J . , B: Zeaman, D. Miniature experiments in the discrimination learning of retardates. In I-.P. Lipsitt & C. C. Spiker (Eds.). Advnnces in child dfJveloprnentund behavior. Vol. 1. New York: Academic Press. 1963. Pp. 3 13-372. Hull, C . L. Es.sc,n/ial.s ofbehui~ior.New Haven. Conn.: Yale University Press, 195 1 , of behavior. Psvchologiccil ReL.iew, 1945. 52. 55-60. Hull, C. L, Essentials ofbr,hcn,ior. New Haven, Conn.: Yale University Press. I95 1, Hunt. J. McV. Intelligence ui7d experience. New York: Ronald Press, 196 I . James. W. Principles qfpsvcholagv. Vol. I . New York: Henry Holt, 1890. Jeffrey. W. E. T h e orienting reflex and attention in cognitive development. Psyc,hologicul Review, 1968.75, 323-334. Jenkins, J. J . , & Paterson, D . G . (Eds.)Studies it1 indii8idrrcr/di~kre.,.c.,7cr.s. New Yoi-k: Appleton-Century-Crofts, 196 1. Kagan, .I.,Henker, B. A.. Hen-Tov, A.. Levine, J . . & Lewis, M. Infants' differential reactions to familiar and distorted faces. Child Det.elopment, 1966,37, 5 19-532. Lacey. J. I . , Kagan, J . , Lacey, B. C., & Moss. H . A. The visceral level: Situational determinants and behavioral correlates of autonomic response patterns. I n P. Knapp (Ed.). Expression ofthr emotion.^ in mmi. New York: International Universities Press, 1963. Pp. 161-196. of lunguugr. N e w York: Wiley, 1967. Lenneberg. E. H. Eiologic~~lJountfations Lewis, M. Exploratory studies in the development o f a face schema. Paper presented at the Symposium on the Origins of Social Behavior, American Psychological Association Meeting. Chicago. September 1965. Lewis, M. T h e meaning of a response. o r why researchers in infant behavior should be oriental metaphysicians. Mrrrill-Palmer Quurrerly, 1967, 13, 7- 18. Lewis, M., Barrels. B., Campbell, H., & Goldberg, S. Individual differences in attention. American Jour~rulofDi.secrsc~.scifChildren, 1967, 113. 46 1-465, Lipsitt. I-.P. Learning in the first year of life. In L. P. Lipsitt & C:. C. Spiker (Eds.). Ad~ ' c r n c in ~ schild development and he/rui,ior. Vol. I . New York: Academic Press. 1963. Pp. 147- 196. Lipton. E. L.. Steinschneider, A., & Richmond, J . B. Autonomic function in the neonate: IV. Individual differences in cardiac reactivity. Psychosornotic Mrdicirie, I96 I , 23, 472-484.

klcCall. R . B. The use of multivariate pi-ocedures in developmental psychology. Unpuhlished manuscript, University of North Carolina at Chapel Hill. 1967. McCall, K. B., & Kagan, J . Individual di1tl.i-ences in the distribution of attention to stimulus discrepancy. Unpublished manuscript, University of North Carolina at Chapel Hill. 1967. Maccoby. E. E. Selective auditory attention in children. In L. P. Lipsitt & C . C . Spiker (Eds.). Advat7ce.s in child devr/opm(,tz/ trtid hdiaiior.. Vol. 3. New York: Academic Press. 1967. Pp. 99- 125. Maltzman, I . Individual differences i n “;tttctitioii”: The orienting reflex. I n R. GagnC (Ed.). Learning r i n d indii,idiccz/ di’ert2t7~~c,.\. (‘olumhus. Ohio: Merrill, 1967. Pp. 94- 1 12. Maltzman, I., & Raskin, D. c‘. E f c c t \ of indi\ idual differences in the orienting reHex on conditioning and complex p r o c a w \ . Jcj urti d of’ Experiniental Resrarch in Per..sotftr/ity, 1965,l. 1-16. Meyer, W . J . , & Cantor. G. N . Infants‘ observing and heart period responses as related to novelty of visual stimuli. Psyckorroni~c.Scicticc., 1966. 5. 239-240. Meyer, W. J., Swanson, B., & Kauchack. N . Studies of verbal conditioning: I . Effects of age, sex, intelligence, and reinforcing stimuli. C/iildDri,rlopme,i/, 1964,35, 499-5 10. Mirzoiants. N. S. Uslovnyi orientirovochnyi rcHcks i ego differentsirovka u rebenka. (The conditioned orienting reflex and its differentiation in the child.) Zliurricrl I Deintelnosfi, I 9.54.4.616-6 19. Pillsbury, W. B. Atretition. N e w York: hlacniillan. 1908. Richmond, J. B., & Lustman, S. I-. Autonomic lunction in the neonate: Implications for psy~, 17. 269-275. chosomatic theory. Psyc/iosomtr/it , h i ’ c , d i e ~ i r i ~1955, Kiesen, A . Stimulation as a requirement I‘m growth and function i n behavioral development. r.rperic~t7c.e.Homewood, 111.: In D. W . Fiske & S. K. Maddi ( I ci\.l. F r t t i c . t i o t i A vfi~co.ic~c/ Dorsey Press, 196 I . Pp. 57-80. Schneirla, T. C . An evolutionary and tlevelopment;il theory o f biphasic processes underlying approach and withdrawal. I n M ..)ones (FA.), Nrhruska symposirrni 0 1 1 rnotii,ution. Lincoln, Neb.: University of N e h r a d a Prcss, 1959. Pp. 1-42. Sidman, M. Tactics vfscierzfiJic re.rcwrc.li. New York: Basic Books, 1960. Skodak, M., & Skeels, H . M. A final follo\v-up \tudy of one hundred adopted children. .IourrialofGenetic Psychology. 1949.75. 85-1 2 5 . Sokolov. E. N. Neuronal models and the orienting reflex. In M . A . B. Brazier (Ed.), The central !ier~’oids system crnd helic~i~ic~r. New York: Josiah Macy Jr. Foundation. 1960. Pp. 187-276. Sokolov. E. N . P t w e p t i o n rind / l i e c o t i d i t i o r r c , t / reflex. New York: Macmillan, 1963. Spears. W. C . Assessment of visual preference and discrimination in the four month old infant. Jvurnul of Compcrrcrlii,r ( t i i d P/i~~sio/ogicer/ P . s ~ c h o l o g y 1964. . 57, 38 1-386. Spence. K. W . Behui~iort h e o r y oud t , o t i c / i f i o t i i t i g . New Haven. Conn.: Yale University Press. 1956. Spence. K. W. Behavior Iheory (znd Iccrrtiitig. Fnglewood Cliffs. N. J .: Prentice-Hall, 1960. Spence. K. W. Cognitive and drive factoi-s in (he extinction of the conditioned eye blink in human subjects. Psyckologiccrl Kcwicjii., 1966, 7 3 , 445-45 I, Steinschneider. A. Developmental psychophysiology. In Y. Brackbill (Ed.). f n f i r t i c , y trnd etrrly cl7ildhood. New York: Free Press, 1967. Pp. 3 - 5 0 , Steinschneider, A. . Lipton, E. L.. & Richnrond. .I.B. Stimulus duration and cardiac responsivity in the neonate. Paper presented at the biennial meeting of the Society for Research in Child Development, Minneapoli\. March 1965. Terrell, G., Durkin, K., and Wiesle). b1. Social class and the nature of the incentive in discrimination learning. J o u r t i u / o j ” 4 h i e ) r ~ mc r~t r/ d Social P.cycho/ogy, 1959, 59, 270-272.

Thomas, A , Birch, H . G., Chess. S.. Hertzig. M. E., & Korn, S.B e / i o i , i o r u / i/idii~iduu/ityin ear/? childhood. N e w York: New York University Press. 1963. Thompson, W. K., & Schaefer, T. Early environmental stimulation, In D. W. Fiskc & S . R. Maddi (Eds.), Functions of varied c~.rprrieticc-.Homewood. 111.: Dorsey Press. I 9 6 1. Pp.81-105. Turkewitz, G., Birch. H . G., Moreau. T.. Levy, L.. & ('ornwell, A . C-. Effect of intensity of auditory stimulation on directional eye movement in the human neonate. Ariimcrl Re,hc iiior, I 966, 141, Y 3- 10 I . Watson, J. S. T h e development and generalization of "contingency awareness" in early i l l fancy: Some hypotheses. Mrrrill-Pnlnier Qucirterl\.. 1966, 12, 123- 136. Wolf, M . M., Risky, T. K.. & Mees, H. I . Application ofoperant conditioning procedures to the behavior problems of a n autistic child. Rrhrrvior R c ~ s r w ~cind / i T/icrop\.. 1964. 1. 305-3 12. Wycoff. I>, B., Jr. T h e role of observing responses in discrimination behavior. Ps~c~/iologic.n/ Revieir,, 1952.59,43 1-44?, Zeaman, D. & House. B . J . An attention theory of retardate discrimination learning. In N . R. Ellis (Ed.),Handbook ofmeri/(i/ dc$ciicic~ncy.New York: McGraw-Hill. 1963. Zearnan, D.. & House, B. J . T h e relation of IQ and learning. I n R . ClagnP ( E d . ) . Lctirtiing und indii>iduci/d@erf,.ricc,s. Columbus. Ohio: Merrill. 1967. Pp. 192-2 12. Zeaman, D.. LY( Kaufman, H. Individual differences and theory in R motor learning task. Psychologicu/Monogrccplis. 1 YS5. 69. (Whole No. 3 Y I ) . N o . 6. Zeiler, M. D. Stimulus definition and choice. In 1.. P , Lipsitt & C . C . Spiker (Fds.). .4dvatices in c/ii/d dc'WkJpttirTittrrrd hahtrr,ior. Vol. 3 . New York: Academic Press. 1967. Pp. 126- 156. Zeiler, M. 11.. & Gal-dner, A. M . Intermediate sire discrimination in seven and eight ceaij ~ . 71, 203-207. old children. J o r ~ r r ~ c i / ~ ~ ~ ' ~ x p e r i iPi si c\ ~~cn~t/tirol/ o , y1966. Zeiler, M . D.. & Salten, C. S. Individual gradients of transposition and a b ~ o l u t cchoice. Journal ofExprrinietitril Child P.syclio/ogy, 1967, 5 . 172- 185. Zigler. E. Metatheoretical issues in developmental psychology. I n M . Maru (Ed.). T/i(,oric..s in conternporciry psyc.ho/og.v. New York: Macmillan, 1963. Pp. 34 1-368. Zigler. E. Familial mental retardation: a continuing dilemma. Sciericc, I Y67. 155. '792-298.

PSYCHOPHYSIOI.,OG ICAL STUDIES IN NEWBORN INFANTS

S. J . Hutt,' H . G . 1,c~tiurd.' tirid H . F. R . Prechtl UNIVERSITY HOSPITAL., ( i H O N INGEN, T H E NETHERLANDS

I. IN~I'K0I)UC"I'IC)N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. 1 H E NEWBORN IN1 AN I I N I T S HI01 OCil('AI- (.'ON'lI<XT. D. I)F.'TE.KMINANTS 01.. .1 Ill: HFHAVIOK 0 1 : I H E NF.WHOKN INIANI. ..............................................

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. 128 I30

II. THE PROHI.F.hl O F Sl XI I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I32 A. I ~ k S ~ ~ ION ~ l I 'OF l l ~ l ~ l l ; l \ ' l O K A l S'I . A'I'F . . . . . . . . . . . . . . . . . . . 132 H. PHl'SlOl.OCilC.I\1. INIII(':\ I ()Its OF STATE . . . . . . . . . . . . . . . . 133 sr..i-i-F I00 F V ) phasic uctivity urising ,from electrically silent buckground (ucc,onlpunic,d in this case b y u slartlr); ( h ) bursts ofaclivity, minimrim durution I second. average i d l u g e > SO p V arisingfronf electrically silent huc.kground; (c) high ~ ~ i l t t r g( a> I O U p V ) phasic crcfivitv arising f r o m tonic' background uc'tivity (see L Quadric.rps); ( d ) bursts c$increti.s(,d ( t i t ~ i c ethat of buckground) voltirge uctivity. minimurn duration 1 second, superimposed upon ulrecr& prcsent tonic crctivity (see L Biceps) (/rom S . J . Hurt et al., 1968, ri.ith kind permission).

146

S.J . H u r t , H . G . Is.ncird, trnd I I . F . R . Preclitl

Fig. 3. Rail, duto . s h o w ~ i nprohubility ~ of E M G response i n euc.h hehtrviorrrl stute with (1nd

three types of uuditiny stirnulation. For compututions. correcieti response valltes were used; these ii’ere ohtciined b y suhtrcictirm of‘the no-stimultrtion response probabilities (dotted line)from / l i e respon.sc-to-stitrrulotion prohuhiliiias ( s o l i d line). T h e nutnher i ~ f m u l r voice stimuli presented in Stcite 111 NYIS insufficient Jbr merrningffirl representation ( f r o m S. J . Hutt et al., 1968, witli kiridpernrission). wiihorrt

given in a recent symposium of the New York Academy of Sciences (Block & Bridger, 1962; Lacey & Lacey, 1962; Selbach, 1962; Wilder, 1962). A simple restatement of the law of initial value might be: The amount and direction of change elicited in a physiological variable by a stimulus is inversely related to the prestimulus value of the variable; i.e., the direction of change is negative if the initial value is large, and vice \‘emu. In the experiments of Bridger and Reiser (19S9) twenty or more presentations of a 5-second air stream were given to infants ( 3 - 5 days old) during a I+-hour period “regardless of the state of the baby that varied from profound sleep to violent crying.” Only the electrocardiogram was continuously recorded. Three heart-rate values were computed, in number of beats: ( I ) in the 5 seconds preceding the stimulus, (2) in the 5-second stimulation period, and (3) in the 5 seconds following stimulus offset. Change in heart-rate response was measured as the difference between

the prestimulus heart rate atid either the 5 seconds during the stimulus or the 5 seconds after the stimulus, '"whichever 5 sec period reflected maximal change in the direction that correlated with the accompanying behavioral change." Each individual's heart--rate changes were plotted against their respective initial values; t h e regi-ession of the former upon the latter was then calculated. All regre\\ions had negative slopes; product-momen t c orre I at io n s between 1-1e ;I rt - i-;i t e c h an ge s and initial v al ii e s t-a nged from -.4 1 to -.93 for individu;il babics. A somewhat curious procedure adopted by Bridger and Keiser ( I9591 was to exclude from consideration all heart-rate responses that LI ere n o t accompanied by observable behavioral responses. The present writers are unable to see the rationale ofthis procedure. If it is that heart-rate changes occur only in the presence of muscle changes, we would maintain that isometric muscle contractions, which are quite unmistakable when recorded electromyographically. are usually not observed by the unaiclerl eye. If, on the other hand, it is considered that heart-rate changes are a n epiphenomenon of some central stimulus analyzing mechanism. then responses to rill stimuli are relevant to how the mechanism work.;. /'he efl'ect of selecting only certain responses, and of using the stimulus intervals showing maximum change correlated with behavior, is o f c'o~irscto maximize t h e law of initial value. If an inquiry is concerned with the operation of the law of initial value in heart-rate changes, then no refcrencc to accompanying behavioral changes should be necessary. Quite clearly, if we are to say anything meaningful about changes from baseline levels following a stimulus. we need to examine the relationships that would be found between r;intlonily selected pairs of readings in the absence of stimulation. Bridger ;ind Reiser were obviously aware of this problem and quite correctly c how pairs of adjacent 5-second intervals between stimuli and plotted the lincat- regression of the latter interval of each pair upon the former. I n thc singlo case quoted from theit- material, both the regression and correlation coefficients thus obtained differed greatly from the corresponding .;timulus values. Unfortunately, we are not told whether the process o f eliminating heart-rate changes not accompanied by behavioral changes was applied to the interstimulus data as well. The report suggests that thi.; was n o t the case, leaving the doubt that the differences in the regression slopes for stimulation and nonstimulation epochs could have been due t o ;I diFfcrerrce in procedure. This point may be important since later experimenters (working with adults. not babies) did not find such large differences betuseen the regression coefficients for stimulus and interstiniulus periods. Siirwillo and Arenberg ( 1964) presented a series of I-second tones ; i t 750 cps to adults and computed heart rates from the 5-second pre- and poststimulus periods. An equal number

148

S . J . H u t t , H . G . Leriurd. and H . F . R . Prechtl

of 10-second interstimulus intervals was selected and divided into two 5second periods. Mean heart rates were obtained for each 5-second period and the regression of the second in each pair upon the first was computed. Slope values were found to be identical with those of the regressions of stimulus upon prestimulus levels. Similarly, Schachter et al. ( 1 967), using behavioral rating scales, found that the law of initial values fitted interstimulus data better than stimulus data. In the study already referred to ( S . J . Hutt et al., 1968), heart-rate changes were recorded throughout. An analysis of these heart-rate data was carried out ( C . Hutt & Hutt, 1969) in the manner suggested by Surwillo and Arenberg. The linear regression of Y upon X was drawn for heart-rate changes on presentation of a 2-second square wave tone at 125 cps taking 5-second pre- and poststimulus periods. I t may be remembered that in this study, matched interstimulus periods of 10 seconds had been selected to take account of baseline activity. A second (control) regression line was drawn of the mean heart rate of the latter 5 seconds upon the mean of the former 5 seconds of these periods. The slopes of the two regression lines were both less than unity but did not differ significantly from each other. I t appears, therefore, that the law of initial value is really a proposition about physiological “regression towards the mean.” “Measures at the extremes of a distribution will, when replicated, show a tendency to be less extreme” (Surwillo & Arenberg, 1964, p. 368), and this will be a s true of physiological measures made between stimuli as those made during stimuli. Since the mean baseline heart rate differs with state, it may be of interest to examine the relationship between initial values and amount of change within states. T h e law of initial value is operating when the slope of the regression of stimulus level (Y) upon prestimulus level ( X ) is less than unity and greater than zero (Hord, Johnson, & Lubin, 1964). Thus, t h e smaller the regression coefficient b,,,.,the more strongly the law of initial values holds. Regressions of Y upon X were next computed separately according to babies’ states at the time of stimulation. The relationships shown in Fig. 4 emerged; the data are from six infants, each of whom contributed three points. The value of bl,r is less than unity in States 1 and I11 and is slightly greater than unity in State 11. Again, the regressions of stimulus level upon prestimulus level are significantly different from the control regressions in each state. Thus, it appears from these data that the law of initial value does not operate as Bridger and Reiser suggest independently of state. In the present case the law does not hold at all in irregular sleep. Moreover, the correlation between Y and X was small and not significant in this state, showing that there was very little relationship between the two variables. This would be in accord with the suggestion made by

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Prechtl and Lenard ( 1967) that irregular sleep is normally the “noisiest” state. In order to answer the possible objection that the law of initial value applies to individual data rather than to group data, a reanalysis was also made of the scores of two babies each of whom had been studied for a continuous 6-hour period ( C . Hutt & Hutt, 1969). The differences between states in the individual data exactly paralleled those in the data. It thus appears that heart rate functioning in irregular sleep obeys rules that are different from those that operate in deep sleep or in quiet wakefulness.

A further possible way of measuring the effects of stimulation is by averaging the data from a large number of identical stimuli. Bridget- and Reiser (1959) have reported heart rates ranging from 68 to 2 2 2 beats per minute. 1’0 average over such a range would be manifestly absurd. In any o n e behavioral state, however, the range is relatively circumscribed. In the rates shown in Fig. 1 for example. the mean heart rate pet- 3-minute epoch in State I varies from 109 to 122 and has a standard deviation of o n l y about five beats. In State I I , the mean varies from 109 to I36 and the standard deviation is somewhat greater. I t would thus appear that rt~itliiti states, averaging is a legitimate procedure. O n e of the most interesting averaging procedures is the “evoked heartrate response” technique of Hord, Lubin, and Johnson ( 1966). A cardiotachometer is used to convert each rate response interval from the EKG into a heart rate. A n averaging epoch is chosen containing M pre- and N poststimulus beats. Readings a r e averaged for the first beats in all epochs, then the second beats. then the third and so o n , until an average heart rate has been computed for each of the M N beats. I n this way. a11 fluctuations that are not time-locked to the stimulus are averaged out, leaving those c han ge s that a r e spec i fic :I I I y and c oti s i st e n t I y st i in ul u s -re la t e d (Hord c’f ( I / . , 1966). T h e technique thus performs with autonomic nervous system data an operation very similar to that used in averaging evoked cortical potentials. In an analysis of heart-rate response t o auditory stimuli of different pattern s and freq ~t e nc i e s, beat -b y - bea t card i o t ;ic home t e I- r e ad i n gs w e re treated by the above technique (C. Hutt rf u/., in preparation). Computations were based upon 22 beats following stimulus onset and 22 beats from the beginning of the paired interstimulus epoch. A typical result i s shown in Fig. 5 ; this compares the effects of two square wave tones ( 125 H z and 2000 Hz) each of 2 seconds duration and 75 d b intensity. With averaging, the interstimulus baseline tends to a stable level. T h e homogeneity of the baseline activity preceding the two stimuli enables direct comparisons t o be made of the relative effects of the stimuli, once state has been taken i n t o account. I t can be seen that the 2000 H z square wave tone produces no clear-cut heart-rate response. T h e I25 H z square wave tone produces a pattern that w e have found to be characteristic of tones from 70 H z to 5 0 0 H z : in all states, there is a bradycardia for two to three beats, a tachycardia for about seven beats. followed by a slow return to the baseline. T h e single fast beat. relative t o the baseline. in State I w a s found with all stimuli below S O 0 H z : its significance is n o t yet understood. For statistical purposes, parameters similar t o those employed in evoked cortical potential studies may be extracted: latency to peak ( a n d / o r first trough) a n d peak amplitude relative to baseline activity (mean, range, and standard deviation).

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I52

S..IH .u t t , H . G . Lencrrd, und H . F . R . Prechtl

While averaging of heart-rate data has been used in several studies of adult subjects (Hord et al., 1966; Lang & Hnatiow, 1962; Meyers & Gullikson, 1967), it has received only slight attention in studies of neonates (Williams, Schachter, & Tobin, 1967). I t would, however, appear to be a valuable technique for treating data having a multiphasic distribution (e.g., heart-rate acceleration-deceleration) as a response to the stimulus. Further, since by averaging, prestimulus levels tend toward the overall baseline level for the state, special computations to exclude prestimulus levels are unnecessary. When the problem under investigation is one of the comparative effectiveness of different stimuli, averaging would appear to be a particularly useful method of analysis. D. THEI N F L U E N C E

OF

STATE

I t was seen in Sections B and C that measurements of baseline activity were a necessary requirement for evaluating the effect of a stimulus but they were not sufficient. Both the probability of interstimulus “responses” and responses to stimulation were affected by the baby’s state. Meaningful comparisons of stimulus and interstimulus events could t h u s be made only when state was taken into account. 1. Rejlexes The ubiquity of the state variable is clearly seen even in studies of spinal reflexes. These may be categorized as monosynaptic or as polysynaptic, and it appears that the two types of reflex are differentially affected by state. By repeatedly evoking a reflex during polygraphic recording, its relationship to state may be clearly seen. In one study (Prechtl et al., 1967b) comparison of the effect of state on the tendon knee jerk (a monosynaptic reflex) and on the exteroceptive skin reflex of the distal part of the tibia (a polysynaptic reflex) was made. The babies were studied under physiologically neutral conditions for periods of 1 to 2 hours between feeds. Recordings were made of respiration, heart rate, E E G , and E M G from eight sites. Reflexes were elicited manually at regular intervals of either 15 or 30 seconds. Responses to both kinds of eliciting stimuli were scored on a four-point scale using EMG criteria. The baby’s state was monitored by an observer and substantiated by reference to the polygraph. Only States I-IV were studied. Motor responses after exteroceptive stimulation of the skin were absent or weak in State I . Positive reactions occurred more frequently and were more strongly expressed in State 11. Negative responses in States I11 and IV were rare. In contrast, the knee jerk was regularly obtained in both States 1 and I11 but was either weak or totally absent in State 11.

The lip-tap reflex (Prechtl & Beintema, 1964) is of particular interest since it contains both monosynaptic and polysynaptic components. On applying an abrupt but gentle tap with the finger upon the baby’s philtrum, there occurs first a short-lasting jerk (the monosynaptic component) followed by a prolonged protrusion of the lips (the polysynaptic component). In a study of the effects of regular and irregular sleep, the lip-tap reflex was elicited repeatedly at IS- to 30-second intervals in a group of eleven full-term babies, aged 4 to 8 days (Prechtl et al., 1967a). The babies were again studied under physiologically neutral conditions for 1 to 2 hours between feeds. Polygrams were recorded of respiration, heart rate, EEG, and eye movements, together with an E M G from the obicularis oris. T h e lip jerk could be clearly seen in the EMG record as a high voltage phasic response, and the lip protrusion as a large tonic response. T h e two reflex components were seen to vary in intensity with respect to the two sleep states. In State I, the lip jerk was consistently elicited and was of high amplitude, whereas lip-protrusion responses were rare. In State 11, lip-jerk responses were significantly smaller, but lip-protrusion responses now occurred frequently. The polygraphic studies thus showed that the mechanisms of spinal reflexes were differentially organized in relation to state. In a more recent study, Lenard, von Bernuth. and Prechtl ( 1968) examined the relationship between twelve reflexes and behavioral state in a group of twenty normal infants, aged 4 to 8 days. The babies were studied under standard conditions for 2 to 3 hours between feeds. Each reflex was elicited at least once in each of States 1, 11. and 111. The order of reflexes was randomized, and the first reflex of any series was elicited only when the baby had been in a stable state for 4 minutes. The interval between successive reflexes was never shorter than 30 seconds. All reflexes were scored on ordinal scales of intensity. varying from no response to very strong response. The results were clear-cut. When considered in relation to different states of the infant, the reflexes fell into three groups: I. Proprioceptive reflexes: These were the knee jerk, the biceps jerk, and the ankle clonus (all monosynaptic reflexes), and the Moro reflex. These reflexes were equally strong during regular sleep and wakefulness but were weak or absent during irregular sleep. 11. Exteroceptive reflexes: These were the palmar and plantar grasp, the Babkin reflex, the palmo-mental reflex, and the tonic components of the glabella and lip-tap reflexes (all polysynaptic). These reflexes were almost totally absent during regular sleep, were weak during irregular sleep, and were strongest during wakefulness. 111. Nociceptive reflexes: These were the abdominal skin reflex,

I54

the Babinski reflex, and the exteroceptive skin reflex from the thigh. These reflexes were easily obtained in each of the three states investigated . The magnet reflex could not be obtained in any of the three states studied. ( I t can generally be elicited during active wakefulness or during crying.) I t is thus seen that even relatively simple reflex responses are intimately bound u p with state. ’The optimal state for eliciting one reflex is not necessarily the optimal state for eliciting another. Only nociceptive reflexes appear to function independently of state. and it is biologically adaptive that this should be the case. If. therefore. the changes of state from I to V are considered as a gradual increase in “wakefulness.” ”activation,” or “arousal.” it is seen that there is no corresponding orderly change in reflex responsivity. I n regular sleep some reflexes are easily elicited, only to disappear in irregular sleep and then to reappear on waking. Other reflexes appear in irregular sleep. but disappear on waking; some appear only when the baby shows a high level of behavioral activity and yet others seem to be present continually. I t would thus appear that, from a neurophysiological viewpoint, states may be more usefully thought of a s qualitatively different systems of organization rather than a s different “levels of arousal” arranged on some hypothetical continuum. Indeed, with respect to reflex mechanisms, the notion of an arousal continuum has little predictive v’d I ue.

2 . Sensory Thrcisliolds it1 N t w n a t r s I f a constant stimulus can have such variable erects, depending upon the baby‘s state, it is to be expected that t o elicit responses of similar magnitude in each state, quite different stimulus intensities will be required. Similarly, it will be expected that the minimum stimulus magnitude required to produce a response on 50‘ i of occasions (the absolute threshold for the stimulus) will be a function of the baby’s state. Data on auditory thresholds in neonates are contained in a report by Bat-toshuk ( 1964) on the relationship between stimulus intensity and heart-rate change. Tones of I000 cps and of I second duration were presented through a loudspeaker. Four intensities. varying from 38 db to 67.5 d b above the ambient noise level, were presented consecutively in first ascending then descending order for five complete cycles. The amount of change in heart rate, plotted on a logarithmic scale, wab found t o be linearly related to intensity in decibels. T h i s is consistent with Stevens’ ( I96 I ) power law relating sensory magnitude anti physical intensity. Responses to tones 47.5 db above noise level were signiticantly greater than the “spontaneous‘. changes observed when the lout1spe:tker W;IS dis-

connected. Responses to a tone only 38 db above noise level did not. according to Bartoshuk, differ significantly from the spontaneous changes, showing that for this tone the absolute threshold for cardiac acceleration was between 38 and 48 db above the ambient noise level. While the design of the experiment is valid for denionstrating Stevens' powet- law, it is not an appropriate design for investigating sensory thresholds, if these are state-dependent. ( I f they are not. the finding is so important that it should be reported.) Using a 2-second sine wave tone at 1000 cps and 75 db (25 db above the ambient noise level), we found that cardiac change, as computed by Bartoshuk's ( I 964) method, wits significantly greater when t h e baby was in State 111 than when he was in States I and 11. To produce an equivalent heart-rate change in regular slecp required an increase in the intensity of the stimulus of approximatel), 2 0 db. I t is important, therefore. that studies of thresholds specify the behavioral state of the babies during stiniulation. Without such specification, the results can, at best, be regarded only as an approximation for all states. arid not in any sense indicative of absolute thresh o Id s . Several authors (Gullikson KL C'i-ob/ell, 1964; Kaye & Lipsitt, 1964; Lipsitt & Levy, 1959) have studied changes in sensory thresholds during successive days of the baby's lifc. Here again, the question of state is neglected and the details of procedure are not sufficiently explicit to make accurate inferences possible. While this in no way affects the validity of the results. it does make interpretation difficult. Moreover, when quite contrary results are obtained i n t ~ ' \tudies o of the same phenomenon, it is not unreasonable to look at considerations of state as one possible source of such differences. For example. in the Gullikson and Crowell study. increasing electrotactual threshold\ were found in tests conducted at approximately 24, 48, and 72 houra after birth. While the apparatus is described in detail, no information i\ giLen a s to whether the babies were asleep, awake, or crying. Since, generally. the intensity of stimulus required to produce a behavioral response varies directly with state. one possible interpretation of the results might be that the babies were spending progressively longer periods i n State I on successive days. [This would be in accord with what is known of the development of sleep states in the neonate- the amount of State I sleep being smallest on day 1 and thereafter increasing on successive dab,s, even though none of the mothers received any drugs before or during delivery (Prechtl & Weinmann. in preparation).] The fact that the threshold of the control group, tested on the third day of life, did not differ significantly from that of the experimental groups on day 1 should have been ;I convincing argument against this interpretation. Unfortunately, here agitin we are told nothing of the be-

havioral state of the control group. Thus, while the authors‘ own interpretation that the experimental infants developed a n habituation to the shock is plausible, Kagan and Henker (1966) have been tempted to suggest: “An alternative interpretation is that the control babies did not have the experience of being brought i n t o a strange room and manipulated and, as a result, may have been in a higher state of arousal.” Transport of the control babies to the laboratory and attachment of the electrodes would have been a valuable control. A decwasc in electrotactual threshold is reported by Lipsitt and Levy (1959) and Kaye and Lipsitt (1964). I t is possible, as Gullikson and Crowell suggest, that their quite contrary findings are due to differences in procedure. I t is equally possible, however, that the differences may have been due to differences in the babies’ states. I n the report of 12ipsitt and Levy, the state of the babies o n stimulation is not recorded. but. interestingly, the authors suggest as one of f o u r possible explanations of their results that “thresholds are higher when the baby is asleep, the child tends to be awake an increasing amount of time o n successive days, and the baby has a higher probability of being tested during an awake state with increasing age.” In the later report (Kaye & Lipsitt, 1964) a clearer account is given of the conditions under which stimuli were presented: “after at least 10 secs of record had passed in which there was no stabilimeter or leg movement, and in which the breathing record was smooth and rhythmic” ( p . 309). As i t is not possible to decide whether the babies were predominantly in State I or in State 111, the possibility that the results could be partly accounted for in terms of state is not excluded. To give credit, Kaye and Lipsitt are obviously aware of this fact, but it is regrettable that the variable was not more diligently examined i n an otherwise admirable study. I t may seem somewhat ad hoc to proffer an interpretation of one set of findings in terms of an increase in regular sleep and the other in terms of an increase in wakefulness. The point is, however, that because state is not consistently treated as an experimental variable, we are always left in doubt as to whether a significant amount of the variance could have been accounted for by this factor. Moreover, the amount of time spent in any state is, in part, a function of the environmental conditions under which the experiment is conducted. I n one study, the environment may be conducive to producing regular sleep. in another wakefulness. Wolff ( 1966), for instance, has shown that continued stimulation with noise results in prolonged periods of regular sleep, which are nevertheless atypical in certain respects. I t is thus desirable that reports should contain a statement of temperature, humidity, ambient illumination, noise, the use of drugs, etc. Even more informative would be a description of state in relation to

stimulation. Alternatively, state could be varied as an experimental variable. I n the absence of such treatmenth, we would have to regard the threshold measurements obtained in the studies quoted as very approximate. Nevertheless, the direction o f the serial measurements made by I-ipsitt and his colleagues, are biologically of considerable interest as they show a rapid increase in the sensitivity of a sensory system during the first few days of life. These results also agree well with another threshold study of olfaction by Lipsitt, Engen. and Kaye ( 1063). This study is highly informative; the precise environmental conditions are reported, together with adequate descriptions of the baby's state at the time of stimulation, i.e., regular sleep. Olfactory thresholds, measured in terms of the concentration of a solution of asafetida in cliethylphthalate required to produce a response. fell steadily during the first 4 days after delivery. I t is quite clear in this study that the threshold measurements are relative to one state only, regular sleep; thus the results cannot be explained by variability in the baby's state on successive clays. This enables us to reduce the number of interpretations. Unfortunately. this is one case in which more details of maternal medication during labor would have been most relevant. That decreasing sensory thresholds during the first 4 days of life may be a biological phenomenon is nevert helexc an intriguing possibility. 3. Stntc. C y c l r s In Section C of Part I I , we discu\ced the serial changes in state that occur in an unstimulated baby between tw3o feeds. Failure to take cognizance of these changes may lead to difficulties of interpretation in studies in which the time course extends ;icros'~such endogenous changes. An investigation in which state cycles should have been a crucial variable, since it purported to study "~ti-ousitllevel," is the interesting reexamination by Brackbill, Adams. Crowell, and Gray (1966) of Salk's findings (1960, 1962). Salk had presented it recording of a heartbeat (at 72 beats per minute and 8S db) through ;i loudspeaker in a newborn nursery for 4 days. Seventy percent of the I 0 2 newborn infants exposed to this stimulation had gained weight at the end of the 4 days, compared with 33% of a control group of 1 1 2 babies not thus exposed. The control group cried 60% more than the experimental group. Food intake was almost identical in the two groups. In a later study with 2-year-old institutionalized children, Salk compared the relative effectiveness in inducing sleep of the heartbeat sound, a metronome at 72 beats per minute, and lullabies. The study by Brackbill et a / . (1966) was in two parts: the first examined the relative efficacy of four stimulus conditions in producing sleep in nursery school children, and the second studied their effects upon crying, movement,

S. J . M u t t . H . G . Lencird, cind H . F . R . Prechtl

158

heart rate, and respiration in neonates. The stimuli were: no sound, lullaby, metronome, and heartbeats. For the older children, the mean number of minutes taken to fall asleep was 20.04. 17.96, 17.95, and 14.64, respectively, for the four conditions, which were presented on different days for different subgroups. For the neonatal study, the four sound conditions were presented consecutively, each for I 5 minutes. Eight orders of presentation were used, the no-sound condition appearing twice in each of the four possible positions, the position of the remaining three stimuli being randomly determined. The resulting experimental design is of interest. Omitting the no-sound condition, which appears equally often in each 15-minute period, the frequency of occurrence of the stimuli in each position was as shown in Table I . Irrespective of stimulation, babies will be in a more active state in the period immediately following fixing of the electrodes than in subsequent periods. By the beginning of the third period, most babies will be in State I. We would therefore predict that overrepresentation of the heartbeats condition during the fit-st period and its under-representation in the third and fourth periods would militate against the association of heartbeats with a low activity state, the heartbeats condition having a higher probability of being associated with fast and irregular heart rate and irregular respiration. In short, the experiment was unintentionally biased against Salk. What is surprising, therefore, is not that by analysis of variance the heartbeat condition was not significantly different from the other two sound conditions, but that the rank order of the various experimental conditions, in terms of their effects upon each parameter, should so consistently have favored heartbeats. On both measures of "crying rate," the lowest values were obtained under the heartbeats condition. Despite its overrepresentation during the period of greatest endogenous activity, the heartbeat condition produced heart-rate and activity level values that were no higher than those for lullaby and metronome. Thus, the heartbeat condition was producing values that were better (in the sense of produc-

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ing lower activity scores) than would be predicted on the basis of endogenous changes only. Since the experimental design placed the heartbeat condition at a particular disadvantage. the absence of a statistically significant effect is not strong evidence against the Salk phenomenon. The greatest effect of state changes is likely to be manifested in studies of habituation because of the relatively long period of time over which they extend. A particularly interesting example is presented by Bartoshuk (1962a). One-second trains o f 5 0 clicks were presented via a loudspeaker to babies aged 1 to 4 days. T h e intensity of the stimuli was 85 db above adult auditory threshold. Forty signals were presented with interstimulus intervals of 15, 30, or 60 seconds in each of three subgroups. Changes in heart rate were measured by comparing rates computed from the five beats before and the five beat5 after the stimulus. The differences between pre- and poststimulus rates were then expressed as percentages of the response obtained on the first stimulus presentation (appropriate corrections having been applied to tahe i n t o account the law o f initial value). Repetitive stimulation produced ;I gradual decrement in heart-rate response over the 40 stimulus presentations. While the actual heart-rate changes were not given, it is possible to infer that the response decrement between the second and fortieth presentations must have been about two to three beats. The interstimulus interval did not significantly affect the rate of decline. Bartoshuk interprets his results iis evidence for habituation of tonic arousal and points o u t the similarity of his findings to those of Sharpless and Jasper ( 1 956) on acoustic habituation in cats. He rqjects the possibility that his results can be accounted for by a "gradual over-all reduction in activation level during the experiment because mean heart rate was higher before the fortieth than the first stimulus." Unfortunately, this increase in prestimulus heart rate neither supports nor refutes the author's claim that the results her-e not due to a change in activation level. With a 15-second separation between successive stimuli, the experimental session would last for 10 minutes, ;ind with a 30-second separation, for 20 minutes. Bartoshuk gives no information regarding his environmental conditions or the timing of his experiment, making comparisons with our own data difficult. Nevertheless. asstiming that his babies were studied shortly after feeding- for nursing convenience. a iisiial pi-ocedure - and in conditions approximating p h y s i ol ogic it 1 neutral it y we wou I d (from the findings in Section 11, C ) expect heart rate to increase for approximately the first 30 minutes of experimental time and then to decrease even if no stimuli were applied. I t is interc5tin.g that with a 1 -minute interstimulus interval, heart rate before the fortieth stimulus did not differ significantly from that before the first stimulus. Again, we are given no information about the state of the babies at a n y time during recording. Their prestimu-

.

lus heart-rate levels lead one to suppose, however, that the babies were certainly not in regular sleep at the beginning of the experiment. From our own natural history studies of normal unstimulated babies we would expect, however, that most babies who were awake at the beginning of the experiment would have passed into irregular sleep, even during the shortest experiment, and that babies who were originally in irregular sleep would have certainly passed into regular sleep in the longer experiments. Since level of behavioral responsivity t o sound is lower in regular than in irregular sleep, and lower in irregular sleep than during waking, any decrease in responsivity could be accounted for by a state change. Using both electromyographic activity and heart-rate changes as their measure of responsivity to repeated sounds, C. Hutt et al. (1968) were unable to demonstrate a decremental process other than one due to a change of state. Their stimuli consisted of 2-second square wave or sine wave tones and human voices, all calibrated to produce a sound pressure reading of 75 d b at the baby’s ear when delivered from a loudspeaker 40 cm away. Each stimulus was presented 60 times with an interstimulus interval of 30 seconds. Polygraphs of respiration, heart rate and EKG, EEG, eye movements, and EMG (6 channels) were recorded. The EMG channels were first independently assessed by two experimenters, for the presence or absence of an EMG response following every stimulus using the criteria already mentioned (see discussion of Fig. 2). With the EMG channels covered, another experimenter then assessed the state of the baby from the remainder of the polygraph. Only States 1. 11, and I 1 1 were considered: regular sleep, irregular sleep, and waking. The state assessments were then matched with the EMG data. A typical sample of the records thus obtained is shown in Fig. 6. For convenience the stimuli are grouped in blocks of five. There is a decrease in EMG responsivity in those blocks during which the state changes from 111 to I1 and from 11 to I . In our data a s a whole (ten babies were studied for periods varying from 2 to 6 hours each), no decrement in responsivity could be demonstrated within a steady state. The heart-rate data showed a similar pattern. The possibility arises, therefore, that Bartoshuk was measuring behavioral responsivity during different states and that what he construed as habituation may represent only a diminution of response contingent upon a “downward” state change. The point at issue is not the validity of the findings but their interpretation. Without adequate monitoring of the state and of the presence or absence of behavioral changes, such results are always open to at least one other interpretation, namely, that the experiment is merely reflecting endogenous changes in an “ultra stable” system (Ashby. 1957).

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A similar problem of interpretation arises in considering the phenomena of dishabituation, i.e., the re:tppear;ince of a response when a habituated stimulus is changed. I n ;I stud!, by Bartoshuk (1962b), a S O 0 cps square wave tone of 80 db was presented 17 times, at 1 minute intervals. As in his earlier study (Barto\huk, 1962a). heart-rate change was computed as a percentage of stiniuliis change on the first trial. A decrease in responsivity was again obset-vccl: and again we would predict that a change of state of at least one downward step would have occurred in most babies. On the eighteenth trial the stimulus intensity was increased to 9 1 db, producing an increaw i n heart rate of SO‘? above that of the first trial. This phenomenon was interpreted as evidence of dishabituation. Our own experience with sound stimuli has shown that. if the baby is in regular sleep, broad-band signal\ (such as square wave pulses) of this intensity generally produce a startle (again. Bartoshuk gave no behavioral data) followed by it period of irregular sleep or by waking. Following the intense stimulus, the responses to dl six subsequent stimuli were greater than those to the six stimuli preceding the intense stimulus, again suggesting that the babies’ state had changed. Although this interpretation does not invalidate that of the author. it does change the point of emphasis. Evidence regarding dishabitiriirion was also obtained from the study of C . Hutt et 01. ( I 968). I f iterative stimulation was continued after “habituation” had occurred, a sudden increa\e in responsivity frequently oc-

S . .I. l l i i t t , H . G . Lrilcirtl, c i i i t l If. F‘. R . P w c h t l

I62

curred. When state changes were entered on the polygraphs, it was found that these response increases invariably corresponded with a state change upward. Changes in the properties of the “habituated” stimulus did not produce dishabituation unless such a change had already begun. An example of “dishabituation” in one baby is shown in Fig. 7. Further evidence suggesting that state changes may account for much of the response decrement regarded as habituation, particularly to acoustic stimulation, is provided by the study of Eisenberg, Coursin, and Rupp ( 1 966). Eight normal newborns, three rated as “suspect” and two as “at high risk” of developmental disorders of communication, were stimulated repeatedly with a modulated tone falling in pitch from 5000 cps to 200 cps in 4 seconds. The mean intensity of the stimulus was approximately 80 db. Stimuli were repeated at intervals of 10 seconds, until ten consecutive failures to respond had been obtained. The sound pattern was then presented in reverse order 10 seconds later. Habituation was considered to have occurred when ten nonresponses were followed by a clear-cut response to the reverse pattern sound. Responses were motor, visual, or vocal events, which were carefully distinguished from nonstimulus behaviors. In addition to specific stimulus-bound responses prior to each stimulus, observers recorded the baby’s state using a seven-point scale varying from deep sleep to extreme excitation. The relation between behavioral

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responsivity and state is an interesting one. Following presentation of the first three signals, all normal subjects showed upward changes in state, attaining “peak arousal within 7-8 trials.” Thereafter there was a gradual decline in response to the stimulus. This was accompanied by one or more downward changes of state until the prestimulus state was regained within 16 to 20 trials. Stimulation was then continued until the criterion for habituation had occurred. In eight cases (including two rated as “suspect”), the baby’s state at this point was one or more steps lower than its prestimulus state: “infants who were wakeful during the pre-stimulus period either were sleeping or approaching that state when stimulation was terminated; those who were dozing went to sleep; those who were sleeping returned to sleep.” When there were fluctuations in responsivity, these were accompanied by almost parallel changes of state. We would therefore suggest that it may be physiologically both more meaningful and more parsimonious to talk of changes of state than of habituation. Certainly, in our own experiment we were unable to demonstrate any systematic decline in responsivity i?,irliin ;I stable state, and the findings of Eisenberg et (11. are essentially in agreement with ours. It is of interest that two of the subjects of the Eisenberg ot ul. study did not show habituation: both showed upward changes of state following onset of stimulation and remained effectively in that state for the duration of the experiment. The babies were those described as at “high risk” for developmental disorders of communication. Again, it may be more parsimonious to say that risk babies stay in the more active behavioral states longer than normals. That the endogenous behavioral cycles of neurologically abnormal babies are deviant has recently been shown in our work. The states of irregular sleep were prolonged in such babies and the regular sleep states foreshortened. I t may be more helpful to look at their abnormality in terms of the functional perversion of a biological clock, than in terms of a “learning” process such ;IS failure to habituate.

IV. Discussion and Conclusions We have seen that the human infant possesses at birth a large and varied repertoire of self-generated and stimulus-elicited behaviors. These behaviors were developed during intrauterine life and may have served important adaptive functions in the prenatal environment. Certain of the neonate’s self-generated activities (both behavioral and physiological) cluster together in recurring patterns called states. State may be defined as “any well defined condition or property that can be recognized if it occurs again“ (.Ashby, 1957). Thus state is a n injunctive

I64

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concept (Hassenstein. quoted in Lorenz, 1956); it is defined by a large number of propxties, all of which are necessary but none of which is sufficient. The state categories primarily used in the present essay were those of Prechtl and Beintema ( I 964). These categories were originally defined behaviorally, but subsequently their heuristic value has been confirmed by the addition of physiological measures such as respiration rate. heart rate, eye movements, EEG, and EMG (Prechtl. 1968b). Because states have generally been placed on an ordinal scale in which is implicit the notion of increasing or decreasing nervous excitation or behavioral activity. it is tempting to regard these states as discrete points on an “activation continuum” (Duffy, 1962). This concept, however, would now seem to be highly questionable. For instance, systemic functions such as blood pressure do not show an orderly progression with ascending steps on a scale from regular sleep to intense behavioral excitement. Similarly, the EEG and evoked cortical responses show a decrease in amplitude in irregular sleep relative to regular sleep. This paradoxicul sleep has often been compared electrocortically to that of extreme alertness or behavioral excitement, when low amplitude, high frequency waves dominate the EEG. Recent work. however, has shown that, at least in the infant, paradoxical or irregular sleep consists of the same low frequency components as regular sleep but with an overall reduction i n amplitude (Prechtl, 1968b). Lacey and Lacey ( 1958). among others, have demonstrated that, in the adult, autonomic variables such a s GSR, heart rate, and respiration do not covary in regular progression as would be demanded by a strict continuum theory. I t is thus clear that the changes in physiological activity that occur between successive states are not necessarily monotonic, as is required by the activation continuum theory. In the human newborn, the probability and magnitude of a response to a given stimulus is almost without exception a function of state. Here again, however, there is no regular progression in responsiveness from state to state. This was most clearly seen in the case of spinal reflexes. Some reflexes could be elicited strongly in regular sleep, but not during irregular sleep. Other reflexes showed t h e converse relationship: yet others could be elicited only during intense behavioral activity; while a further group could be evoked irrespective of the baby’s state. While, therefore, we would regard specification of t h e baby’s state as a sine ~ I A Ution of psychophysiological studies. we do not consider that the physiological evidence requires that these states be placed on a continuum. Rather. they may better be regarded as qualitatively difl’erent neurophysiological conditions with specific functional organization. Although state is a variable of the utmost importance in determining the degree of response to a stimulus, it is often remarkably little affected by

the stimuli applied. In our own studies o f the effect of repetitive elicitation of monosynaptic and polysynaptic reflexes (Prechtl et a/., 1967b)and auditory stimulation (S. J. Hutt r t ( i / . , 1968) the state cycles showed similar durations to those observed in unstimulated babies (Prechtl, 196%). Moreover, the heart rate showed the same saw-toothed pattern of fluctuations as in the unstiniulated baby (see page 139). the different stimuli having little apparent effect. Whatever the nature of the physiological mechanism that regulates the newborn infant’s state cycles, it clearly has great stability. This does not mean t h a t it is impervious to all environmental influence s . Dress i n g, en v i ro ti in e n t a I t e ni pe ra t u re. and po s si b I y hum idi t y influence both the duration and stability o f the state cycles. Wolff ( 1966) has claimed that ambient noise and light also affect the baby’s state. Pending further research on the effect\ of environmental influences upon state, it is important that the fullest cletails o f recording conditions be given in reports of newborn psychophysiologic~ilstudies. Both the stability of state cyclcs and the effects of stimuli are influenced by brain damage arising from obstetric complications (Beintema. 1968). by maternal ingestion of analgesics and anaesthetics, by abnormalities of postnatal adaptation, and later \ysternic disturbances. I t is therefore important that babies are screened both pediatrically and neurologically prior to testing. Maternal drug ingestion may be a particular hazard in the interpretation of psychophysiologic~ilfindings from the first 3 days of life. Changes in behavior on successive days to t h e same stimulus may simply reflect recovery from the effects of maternal sedation. We observed in the previous section that while environmental conditions and the baby’s state during stimulation were often precisely recorded in relation to sensory threshold determinations, maternal sedation was not. Since several of the studies reported changes in threshold (luring the first 4 days of life (e.g., Kaye & Lipsitt, 1964),the interest o f the findings as well as their interpretability would have been increased had information regarding drugs been given. As a general rule, for studies of infants under 4 days of age, a record of drugs taken by the mother is essential. and, whenever possible, a control group without drugs shorild be compared. Before an event (behavioral or physiological) can be said to be causally related to a stimulus, it must he shown to have a consistent and reliably different probability or magnitude of occurrence from its occurrence in the absence of stimulation. Within any one state, therefore, the effect of a stimulus can only be judged if the baseline activity is sampled in proportion to the stimulus presentations. If data are not adequately sampled hetn~rcristimuli, changes in the dependent variable may quite erroneously be attributed to the stimulus. which are merely the result of endogenous changes in the infant‘s activit),. T h i s problem can be seen “writ large” in

I66

S. J . Hictt. H . G . Lencird, mid H . F . R . Prechtl

studies of the law of initial value. The deviations from prestimulus values following onset of the stimulus are frequently not reliably different from random fluctuations about the mean baseline value of the variable being tested. If the time course of an experiment is such that one or more changes of state have taken place, it is essential that stimulus and interstimulus epochs are represented equally in all states. Unless the physical and neurological status of the infant, his behavioral state, and the conditions under which h e is studied are taken into account, statistical significance is of little value. This point needs some emphasis since statistically significant results may be obtained in a study because of the chance concurrence of a number of uncontrolled variables, each of which individually is of small effect. A number of studies (that have not been reviewed in this paper) appear to be of this kind and have produced data notable for their lack of biological plausibility. Such “chance significances” are particularly likely to arise from studies using large numbers of subjects. Levy (1967) has recently discussed the question of substantive versus statistical significance of differences between groups. H e points out that with large samples very small absolute differences may be statistically significant. A significant result achieved from a small number of cases is of greater potential value than a result from a large number of cases that achieves the same level of significance. One of the striking features of many neonatal studies is the very large number of subjects used. I t may be argued that the larger the sample, the greater the generality of the results. In some studies, however, in which the biological significance of the findings is proving particularly elusive, it is tempting to wonder whether the result was indeed a “chance significance.” We are n o t arguing that appropriate statistical tests are unnecessary, only that the statistical significance of a result needs to be reviewed alongside its biological and practical significance. A similar point is made by Johnson and Lubin (in press): “lf we reject all results not bearing a certified confidence level, then we reject almost all of our heritage of biological research including most of the work done by the winners of the Nobel Prize. Formal significance tests may be helpful, informative, and sufficient, but they are not necessary.” In summary, we are advocating a more biological approach to the psychophysiological study of the human neonate than hitherto has been customary. Such an approach has three prerequisites. First, the present unseemly haste to apply stimuli of every possible kind should at least be preceded by more assiduous study of what infants do (behaviorally and physiologically) when they are not stimulated. The effects of stimuli can be correctly evaluated only by reference to such natural history studies. Second, studies should proceed from a detailed knowledge of the specific

organismic and environmental influences that affect the activities of the unstimulated baby. Third, when stimuli are applied it is desirable that priority should be given to those stimuli that occur in the infant’s natural habitat. If, as we have suggested. the human neonate is highly adapted to the job of surviving on the mother’s body, it would be surprising if the immature nervous system was not in some measure “tuned” to react to the stimuli that form that habitat. Questions regarding the innate capacities of the immature nervous system may be more appropriately framed in terms of how the infant deals with naturally occurring stimuli than in terms of reactions to stimuli chosen only for technical expedience. In the last analysis, psychophysiology has but one aim: to illuminate the physiological mechanisms underlying behavior. We believe that progress toward fulfillment of this aim will be made more quickly when the infant himself, rather than the experimental psychology textbook, poses the questions.

Ashby, W. R. An i~troduc.tiot7t o c y b c r t r r t i c . .. London: Chapman & Hall. 1957. lo~y. 1964, 1, 8-25 Ax, A. E‘. Goals and methods in p s y c h ~ i p l i y ~ i ~ ~Psychophysiology. Barnet. A . B.. Lodge. A.. & Armington.1 C.. 1.lectroretinogram in newborn human infants. Scietice, 1965, 148.65 1-654. Bartoahuk. A . K. Human neonatal c;ti~cli;tc itcceler-ation to sound: Habituation and dishabituation. Perc,eptutrl und Mo/orSXill.v. 1962. 15. 15-27. (a) Bartoshuk, A. K. Response decrement with repeated elicitation of human neonatal cardiac a P/rysio/ogic,n/Psyc.ho/ugy. 1962. 5 5 , acceleration to sound. Jour)ru/ (?f ( ‘ o r ~ i p t r r t r t i i ~ntrd 9-l3.(b) Bartoshuk. A. K. Human neonatal cardiac re\ponse to sound: A power function. PsychonomicScience. 1964. 1. I S 1-15? responses to sound: hlethoBeadle. K. R.. & Crowell, D . H . Neonatal electi-ucai-diogr~iphic dology. J o u r n d ofSpeec/r urrd k / ~ ( r r ! K~~gv c t r r c , / r1962, . 5 , 1 12-1 23. infutrts. Clinics in Developmental MediBeintema, D. J . A neurological .s/udv c!f’ nc~ii~hr~rn cine. N o . 28. London: Heinernann. 1968. Bell. K . Q. Some factors to be controlled in \tridie\ of the behavior of newborns. Biologia Neonutorum, 1963. 5. 200-2 14. Bench. R. J . The choice of responw index in p\ychophysiological studies of the human on Mediccrl und Biologicul Engineonate. Digest of’ rhc. 7th It?tet-fru/ionu/C‘onfc~rencc~ neering. Stockholm: Almquist & Wik5ell. 1967. Block. J . D., & Bridger. W. H . The law 01 initial vaIue in psychophysiology: A reformulation in terms of experimental and theoretical con\iderations. Annc1l.v o f t k e Nrit, York Acudr n i y ofSc.ienc,es. 1962. 98. 1229- 124 I . Brackbill. Y . Research in infnnt behrix~ior:A cross-indexed bibliography. Baltimore, Md.: Williams & Wilkins, 1964. Brackbill, Y., Adams. C i . ? Crowell. I). H . . & (ii-ay, M . I..Arousal level in neonates and preschool children under continuoti\ auditory stimulation. J o u r n ~ lof Experimental Child P.sychlogy, 1966. 4, 178-IXX.

I68

S. J . Hurt, H . G. I.ri7ard. uiid H . F . R.Prechtl

Brazelton, T. B. Psychophysiologic reactions i n the neonate. Jortrrltrl c!fPeditrrrics, 1961. 58.508-5 18. Bridger, W. H. Ethological concepts and human development. In J . Wortis ( E d . ) ,R e c e n t advances in hiologic.a/psychiatry. Vol. 4. New York: Plenum Press, 1962. Bridger, W . H., Birns, B . M . , & Blank. M. A comparison of behavioral ratings and heart rate measurements in human neonates. Psvc.ho.sonitrtir Mediciilr, 1965.27, 123- 134. Bridger. W . H.. & Reiser M . F. Psychophysiological studies of the neonate: An approach toward the methodological and theoretical problems involved. P.sycho.somrrtic Medicine. 19.59.21, 26.5-276. Crowell, D. H., Davis, C. hl.. Chun. B. I . . & Spellacy. F. J . Galvanic skin reflex in newborn humans. Science. 1965, 148. I I OX- I I I I . Delange, M.. Castan. P.. (’adilhac. .I.,& I’assouant. P. I.cs divei-s stade\ du sommeil chez le nouveau-ne et le nourisson. Rctsrre Nertrologiqric., 1962. 107.27 1-276. Dreyfus-Brisac. C . Electroencephalography in infancy. In F. Linneweh (Ed.), Die phy.sio/ogische Ent~ic.Hungdes Kindes. Berlin: Springel-. 1959. Dreyfus-Brisac. C. T h e E E C of the premature infant and full-term newborn. In P. Kellaway & I . Petersen (Eds.). Nerrrologicml und r l e c ~ t r o c ~ t i c e p h a l o ~ r ~c,orrelatiw rp/~i~ sfutlies in infuncy. New York: Grune & Stratton. 1964. Dreyfus-Hrisuc, C‘., Fischgold, H.. Samson-Dollfus. 0.. St. Annc Durgassies. S..7iegler. D., M o n o d , N..B Hlanc. C. Veille, somnieil c t rliictivitl sensorielle cheL ICpi-&mature rrrid C l i i ~ i c ~ c iNcrrrophy.\ioloKy, l Suppl.. et l e nouveau-nl. ~/~~ctroc~rlc~eI,hrrloK,.rrph? 1965. 6. 418-440. Dreyfus-Brisac. C . . & Monod. N . Sleep of premature and lull-term nconates: A polygraphic study. ProccJedingsiifthe R ( J w / Soci OfMedicirZc~.I965.58,6-7. Dreyfus-Brisac. C . . Saniwn. D.. Blanc. & Monod. N . L’i.lectroenceph~ilogranimede I’enfant de moins de 3 ans. Biologici Neoiiatorirm. 1958. 7 . 143- 175. Duffy, E. Activatiou undbehntior. New York: Wiley, 1962. Eisenberg, R. €3.. Coursin, D. €3.. & Rupp, N . R. Habituation to a n acoustic pattern as a n index of differences among human neonates. Jorrrilol of Auditory RrscJcrrch, 1966. 6, 239-248. Eisenberg. R. B.. Grillin. E. J . . (’oursin, I). B.. & Hunter. M . A. Auditory hchavior in the r Ilctrritlg Rc.secirch. 1964. human neonate: A preliminary report. Joitrii(i/ (tf S p c ( ~ ’ /cirltl 7, 245-269. Eisenberg, K. B.. Griffin. E.. & Coursin, D. B . Auditory behavior in the human neonate: A preliminary report. Jortrncil o f S p e r c h r r n d Hecrritig Reseclrch. 1964. 7. 245-269. Eliet-Flescher. J., & Dreyfus-Brisac, C. Le sommeil du nouveau-ne et du prematurt. 11. Relations entre I’EEG et I‘EMG nientionner ;it1 coui-s de la maturation. Hiologicr Nron(JtOrU?H, 1966, 10, 3 16-33’), Escalona, S. K. T h e study of individual differences and the problem of state. Americcin Academv of Child Psyehirrtrv Jouriicrl, 1962. I . 1 1-37. Fantz, R. L. Visual perception and experience: A look at the hidden side of behavior development. In H. W . Stevenson, E. H . Hess, & H . I-. Rheingold, (Eds.), Early hehaLior: Compurotive and der.rlopmentul npprooches. New Yoi-k: Wiley, 1966. (;oldie, L.. & v a n Velzer. C. Innate sleep rhythms. Brtiiii. 1965.88, 1043- 1056. Graham, F. K., & Clifton. R. K . Heart-rate change iis a component of the orienting response. Psychologicul Bulletin. 1966. 65, 305-320. Greenberg, N . H . Studies in psychosomatic differentiation during infancy. Arc,hit.es of Genrrul Psychiciin. 1962.7, 389-406. Gullikson, G . R., & Crowell. D. H. Neonatal habituation t o electrotactual stimulation. Joirrncrl of Experimental Child Psvchology. 1964. 1, 388-396. Hershenson. M. Development of the perception of form. Psychologicol Rullrrin, 1967. 67. 326-336.

.

Hooker, D. (Ed.) The p r r r i t i r d ~ i g i t ( Ji / /w//(/i,/(tr.Lawrence, Kans..: University of Kansas Press, 1952. Hord. D. J . . Johnson. L. C.. & LLubiii. .I I)ilfeiriiti:il effect of the law of initial value t L I V ) on autonomic variables. P , \ ? . [ . / I ( ) / J / / ~ \I/!K>4, , ~ / I 1J.~79-87, ~, Horcl. D. J . , Lubin. A,. XC Johnson. I ( . I Iic cLoketl heart-i-ate I-esponse during sleep. Psy('I/Oph?..\iO/Ofi?,1966. :?.46-54. Humphrey. T. Some correlations bet&c.cn the appearance of human fetal reflexes and the de\.elopnient of the nei-vous s y \ t e i i i /'ro,cr(,\.< iir Brcri17 R11.se.crrc.h. 1964. 4. 93- 1 3 5 . I n D. P. Purpura XC I . P. Schude ( F d \ ) , (;~IJII I / / e m / viu/idrotior! o f t h c hr(rirr. A n n t e r d a m : Elseviei-. 1964. Hutt. C ~ . .& H u t t , S. J . ;he neonatal cvohetl he;ii.t-rate response and the law of initial value. P . ~ ? . c , l / ( ~ i . ' / / ? . . ~1069, i ( ~ / ~ ~ing pre\\. ~, Hutt. C . . Lenard, H. C J . . v o i i Bernuth. I I . lHult%S J.. & Prechtl. H. F. R. Habituation in t-elation t o state in the human neoriate N e i r r t r - 6 , . 1968. 220. 6 18-620. Hutt. S. .I..Hutt. C., Lenard. H . C; . ~ o i Ikriiutli. i H.. & Munt,jeweiff. W . F. A u d i t u r y responsivity i n the human neonwtc ,%~~r//o'c. I O h H , 218. 8x8-890. I r w i n . 0. C . The amount and nature o I : i ~ t i ~ ~ 0i 1t i iicwborn c~~ infants under constant external stimulating conditions during the lii.\t tcii d:ik 'I o f life. G c ~ r i i ~ t i cP. . \ ~ c . / I Ihlouo~o~~ grnphs. 1930. 8 , 1-92. Johnson. 1.. C.. & L.ubin, ti. On pliiiiiiiiiL: [>\!I l i ~ ~ p l i ~ s i o l o g i cexperiments: "I De'Iign. measurement and analysis. I n N.S. Circenlieltl A R. A . Sternbuch (Eds.). N t / / i d h ~c!fpsy~k chophvsio/ogy. N e w Y o r k . Holl. Kiiiehai-1 B Winston. i n press. Joiixis, J . H . I'.. Vissel.. 1.1. I(. ,A.. k 1 i ( ~ ~ ' l \ t l.I~ i ,I . ( E d \ . ) .7 / / 1 , ( / d ( / / J / ( / / ; # J / 7 ( J f f / / C , / / r , i i . h o r r / i / f f c / t i / / O i ~ . ~ / u - / i / e r i/if;,. u i ~ I .cideii SIeiii'ei t hi.oc\e, 1964. Kagan. J.. & Henker. B. A . I k v e l o p n i c n l ~ i lp\)chologq. Ai7/1rrtil Rei,ieil of P,syc/io/r)gj, 1966. 17, 1-50, Kaqe. H.. & L-ipsitt. L. 1'. Relation of elceti~o-t;ictii:il threshold t o basal skin conductance. C//iltlDel~elr,y,,Iet/t.1963. 3 s . I 3 0 7 - I 1 I 2 Kleitman. N.Sleep untl I t . t r k e f i t l / ? c , . s . c . ( ? i i d ed.) ( hicago: Chicago Universit), Pres5. 1963. Kron. R. E., & Goddai-d, K. E. N e \ i l x ~ i n\uchiiig behavior affected by obstetric sedation. Peditrtrics. 1966. 37. 10 I 1-I 0 16. I.acey. .I.1.. & Lacey. B. C . Verific,ition iiiid ekteti4on of the principle\ o f autonomic response-stereotypy. A ~ ~ 7 ~ , ~ r ~ , ~ i r( J // ~Pl. ci \i ~f ~~/ ~7 o/ l(l J/ /g1058. y . 71. 50-73. Lacey. J . I . . & Lncey. B. C. T h e la\\ of i i i i t i i i l i a l ~ i ei n the longitudinal study o f autonomic constitution: Reproductivity o f :iiitonomic iesponses and response pattern5 over a fouryear interval. Anntrls ( ~ . f t / i tNrit ~ ) ( J ~ , L~ ~ ~ I / I / ofSciencc~s, c,IHv 1962. 98. 1257- 1290. Lang, P. J.. & Hnatiow. M . Stimulus rcliolilioii ; i d heart-rate response. J o u r t / 0 / ofCompcirriti\,r cind Ph.v.sio/ogiccil P s L Y . / I o /1062 (I~~\~. Langredei-. W. Uber Fdtalreflexe uncl d e i c i i in deutung. %eirsc/ir(ftfyir G c h i t r f .s/ii!fe / / / i dC ~ / i i i k d ~ g1940. i ~ . 1 : i I . 2 \7--252 1-ehmian. D. S. Ethologq and psycholog! I n I Wortis (Ed.). Krcenr cidi~urice.~ it? biolr~giccrl p s d i i c r r r y . Vol. 4. N e & Y o r k : Plenririi h e \ \ . 1962. Pp. 86-94. Lenard. H . G.. von Bernuth. H.. K: l'ieclitl. ti I-.R. Reflexes and their relationship to behavioral state in the newborn. A c / [ i f'tirdrrrrrictr. 1968. 57. 177-185. L.evy. I'. Substantive significance o f 'Iigiiilieiiiit tlitt'ereiices between t w o groups. P A ? . c . ~ / I J ~ o ~ I (,c// Birllrtin, 1967. 67. 37-40. I.ipsitt. I.. P. Learning i n the human i i i t i i i i t . 1 1 1 t i . M'. Stevenwn. E. H. Heah. & H . L. Rheinfold (Eds.). Ernrl?. h e h ~ r i ~ i o rCco / t / p i r ( i t / i , (ei r r d d( lopmerrttrl rrpproc~chr.s,N e w Y o r k : Wiley. 1967. I-ipsitt. I.. P.. Engen, T.. Kaye. H I)c\ clopriiental changes i n the olfactory threshold of the neonate. C/7i/d/) / ( J p U I P / / /l ,( J f > 3 " :bi. 37 1-376.

170

S . J . I l i r t t , H . G. Letitirtl. unrl H . F . K . Prrchtl

Lipsitt, L. P.. & Levy. N . Electrotactual threshold in the neonate. Child Developmt,nt, 1959,3O.547-554. Lipton, E. L., & Steinschneider. A . Studies on psychophysiology of infancy. Merrill-Prrlnzrr Quarterly. 1964. 10. 103- 1 17. Lipton. E. L... Steinschneider, A.. & Kichniond. J . B . Autonomic function i n the neonate. hosotii(1tic. M(’dicitIr. 1960. 22, 57-65. I,ipton. E. L., Steinschneider, A.. & Richmond. J . B. Autonomic function in the neonate. IV. Individual difference5 in cardiac 1-eactivity. Ps.whosotnri/ic Medicine. 1961. 23. 472-484. ( a ) Lipton. E. I>., Steinschneider, A.. & Richmond. J . B . Autonomic function in the neonate. I I I . Methodologic considerations. Psycliosotntrric Medic,ine, 196 1 , 23, 4 6 1-47 1 . (b) Lipton. E. L.. Steinschneider. A,, & Richmond. J . B. T h e autonomic nervous system in early life. N ~ EnglandJournuI N c$Metlicinr. 1965. 273, 2 0 1-208. Lipton. E. L.. Steinschnetder, A., & Kichniond, J . B. Autonomic function in the neonate: VII. Maturational changes in cardiac control. Child D c v r l o p m e n t . 1966, 37. I - 16. LorenL, K. Comments on Professor Piaget’s paper. In J . M . Tanner & B. lnhelder (Eds.). Di.scussion.s on child dr\vlopmetit. Vol. I . London: Tavistock, 1956. Meyers, W. J.. & Gullikson. G . K . T h e evoked heart-rate response: T h e influence of auditory stimulus repetition, pattei-n ~-eversaIand autonomic iirousiil level. P.\yclwplrysi ~ l o g 1967,4. ~, 56-66. Minkowski, M. Neurobiologische Studien a m menschlichen Foetus. Handhucli der Biologischen Arheirsmethotlcn, A h / . 5 . I928.SB. 5 I 1-6 18. Monod, N . . & Pajot, N . Le sommeil du nouveau-nC et d u p k m a t u r t . I . Analyw des etudes polygraphiques. Riologicc Neontctorirni, 1965. 8 . 28 1-307. Papousek, H . Conditioned head rotation reflere\ i n infant\ in the firct months of life. Acta Ptlrditi/ric.cI. I96 I , SO, 565-570. Parmelee, A. H.. J r . , B r i c k , K.. & Hriick, R1. Activity and inactivity cycles during sleep of premature infants exposed to neutral temperature. Hiologitr N t , O / l ( r t O t - i i l t l . 1962. 4. 317-339. Parmelee. A . H . , Schulr. H. K . , Kc Dishrow. M. A. Sleep patterns of the newborn. J o u r n a l q f P r . d i t ~ t r i ~1961, . ~ , 58. 241-250. Passouant, P., Cadilhac. J.. & Delange, hl. I x somineil du nouveau-ne. ConTiderations s u r le periode des mouvements oculaires. Archii.es Frtrnqtrises dr PPtlitr/rior, 196.5, 2 2 , 1087- 1092. , Petre-Quadens. 0. Etude d e sommeil chez le nouveau-ne normal. In Le son7meil dr nuit normal p t pathologiqur. Electroenc&phalogl.aphie et neurophysiologie clinique. Nouvelle serie, Vol. 2. Paris: Mnsson, 1965. (a) Petre-Quadens. 0. L’ontogenkse de l a phase clu scminieil correspondant au rtve. Acfci Ncirrologia e t Psychicitricci B~lgicri.196.5.6.5. 97 I . ( b ) Petre-Quadens, 0. On the different phases of the sleep of the newborn with special reference to the activated phase. or phase D. Journtil of’ Nrurologictrl Scienc.c~.r.1966. 3, 151-161. Prechtl. H . F. R . T h e directed head turning respunse and allied movements of the human body. Behaviow. 1958, 13. 212-242. Prechtl, H. F. R. Problems of behavioural sttidies in the newborn infant. In D. S. Lehrman & R. Hinde (Eds.). A d ~ ~ c i n c ei sn t h e sfrrdy o f h t ~ h c r i ~ i o rVol. . I . N e w York: Academic Press. 1965. Prechtl. H . F. R. Neurological sequelae of prenatal and pcrinatal complications. Brirish Medical Journal. I967.4,763-767.

Prechtl. H . F. K. Neurological findings i n t i c w born infants after- pre- and paranatal complications. I n J . El. P. Jonxis. H . K . ;\ Vi\\ct.. K J A . 'T'roelstra (Eds.).A.spec.tc o f p r i i ~ ~ m ~ tiirir? cind lly.\nlcrtio.iry. Leiden: Stenfelt K n ~ e w I96X. . (a) I'rechtl. H . F. K. Polygraphic studie\ ot'tlic lull tet'ni newborn infant. 11. Computer analysis ofrecorded dala. I n M. c'. 0. H a x S. Itri,ecru-nii I c r i n e . (1Ioctor;il di.;sertations. L 111 IIC P:it I > ) , 1'ai.is: Foulon. I 9 5 5 Smder, L. W.. Xr Julia. H . L. ('ontinuoil\ iiiteiiiI::tiot:iil monitoring in the neonate. Psyc / 7 o . s 0 r r l r r r i c ~M d i c . i n e , 1966. 28. x22-X 35 Schachter, J.. Williams, T. A . . Hcnnett. S . Iyc Willi;iiii\. .I. [I.Spontaneous and stiniiilusevoked hehavioural vari:ition\ III neiin;itc\ Paper p i - c x n t e d at the meeting of thc S o ciety for Re\earch in C h i l d I 1 l o p i i i c - n t ~N e n \I'oi-k. A p r i l 1967. Sclbach. H . T h e principle of relaxation o \ c i l l a t i o n ;is a special instance of the law of initial value in cybernetic functions. Anir- hc i-eLi\e\ nioi-e m d nioihe ?i-aduall> liilli :i\lecp. then \uJdenl\ lerhs 'ibahe. H I \ r.be!id\ . upheii visible. h a c e a gl ippeai-ance. Respiration I\ m o r e apt t o he marked b> reytilarity than i r r e g u l x i t )

4

There

I\ little gross motor' acti\it>. i.e.. niovements involving the whole hod). although there ma) he some movements of the extremities a n d face. T h e baby's eyes are open and in WolfYs terms (1966)are

characterized by :I bright. shiny appearance. T h e m:ijor difference between this state and the other t h o waking states is that this i s ii prtrc,qfirl state. .Accordingly. the vocalizations that occur during this state are not o f an "unhappy" variety. Respiration is relatively regular. though l e s s regular than i n quiet sleep. i

,Active awake

T h i s state i s marked b y ;I considerable xniount of gross motor activity. For example. iis an infant become< unhappy he ma) begin to wi-ithe. Ke4piration i\ often quite irregular. W i t h i n the qpectrum of vocaliziitions occurring during this per-iod are those of the c r a n k y . fussy car-iety.

6

(.vying awake

T h e criteria for this state are the same ;IS t h o w for the preceding state except that i n addition the infant I S ci-ying. ( H e may 01- m a y not be producing tears: most very young infants do not.) T h e lower limit of crying is defined iis pi.otesting of a definite, sustained nature.

"Used b y Hrackhill a n d associates at the University o f D e n v e r Behavior Development l-aboratorq

5

I76

Y w n n e Bruchhill und Hirum E . Fitzgrrald

been developed with three sleep states, e.g., Wolff s ( 1 966), or even more -there are six in the scale used by Metcalf et ul. (personal communication)-it has not yet been demonstrated that these or other more elaborate categorizations can be made reliably or that such a refinement is useful. Two points might be noted about the category “drowsiness.” First, since it is a transition state (the others are not) it occurs less frequently than the other states. Second, as Wolff has pointed out ( 1 966), a state of drowsiness occurs more frequently in the transition from awake to asleep than from asleep to awake. From data on changes in state that we have collected in connection with various studies of infancy, we estimate that the probability of an infant’s passing through a drowsy period en route to sleep is about .8, while the probability of his being judged as drowsy as he passes from sleep to awake is about half that. The number of categories for ~ w k i r z gstates in this scale may be reduced from three to two if there is some reason for recording crying as a separate variable, for crying is indeed the only point of distinction between states 5 and 6. The chief advantage of including it as the end point on a scale of state is that it dispenses with the need for another event marker when recording is carried out by mechanical aids. Roffwarg, Muzio, and Dement ( 1 966) have stated that in falling asleep all neonates move directly into active sleep rather than quiet sleep. Our data show that the picture is not so clear for infants beyond the neonatal period. Some of our data on I-month-old infants, for example, show that in only 68% of the instances in which infants fell asleep did they go directly into active sleep from a waking state. I n fact, the transition in the opposite direction was more striking for these infants: 83% of them awoke from active sleep, while only 1 7 5 awoke from quiet sleep. The scale shown in Table I is. generally speaking, both easy and reliable to use. In fact, it is simple enough for reliable use by people who have never heard of “state” nor even encountered a baby at close range. By way of illustration, the first author recently escorted three groups of undergraduate volunteers from a lower division child psychology course to a residential nursery where, after reading through the scale definitions, they proceeded to observe and rate every available infant between the ages of 4 days and 6 months. The median correlation between their judgments and the author’s was .98. In terms of absolute number of agreements with the standard observer, 168 of 186 observations (or 90.32%) agreed perfectly, 15 or 8.06% disagreed by one point. 1 or .54% disagreed by two points, and 2 or 1.08% disagreed by three points. Two final notes may be made on the measurement of state. The first is that, generally speaking, spot checking or time sampling yields greater

agreement among judges than does the continuous recording of state. This is chiefly because continuous recording involves making decisions apropos transitions from one level to another, and these are not always easy to make, especially when the infant is moving toward lower levels of activity. T h e second point is that the assessment of state in infants depends, far more than during any subsequent stage of development, on the observation of real, live behavior and on-the-spot judging. With adult S s , it is entirely possible to determine state “blindly” from a polygraphic record taken when no observer was present during the recording; even relatively inexperienced judges can distinguish with considerable accuracy whether an adult S had been awake or asleep, and, moreover, which of the five sleep states his record exhibited at any given time (though the distinction between states 3 and 4 cannot be made as accurately as the others. On the other hand, for infants (at least for young infants) this is not possible. Polygraph records, unaccompanied by an observer’s records, cannot be reliably interpreted since in young infants neither behavioral nor physiological functions have as yet developed the unique characteristics that impose distinctiveness and clarity on the various states identified so easily in adults. Fur one example, the range of speed of electroencephalographic (EEG) activity in adults is about twice that for infants. For another, adult polygraph records show peculiar forms of EEG activity, e.g., K complexes and sleep spindles, which almost invariably indicate a particular state o f sleep. but such distinctive patterns are absent from infant records. Again. in adults, the hallmark of REM sleep is, as t h e name implies, rapid movements of the eyes; these occur on the order of 5 to 10 times a minute. I n infants, however, truly conjugate eye movements during active sleep are both rarer and less distinct. B. RESPONSE TO U N C H A N ( , I N CS,I I M ~ J AI I I O N : PACIFICATION

Most adults require an environment of low-intensity stimulation in order to fall asleep. Light is excluded: noise is blocked out: and the temperature is regulated. This is not the way we responded as infants to such stimulation. For most young infants, continued sensory input of a monotonoiis character has the effect of lowering rather than raising level of arousal. Thus infants are less aroused in ii noisy environment than in a quiet one, less aroused under high illumination than in darkness, less aroused when swaddled or clothed than when naked. and less aroused when being jiggled than when lying quietly in their cribs. And by “less aroused” is meant a quite specific pattern of behavioral and physiological effects: I t means that infants move about less, that they cry less and sleep more, and that their heart and respiration rates are lower and more stable. A more conno-

tatively appealing term for this pattern is “pacification” or “quieting.” [Lipton. Steinschneider, and Richmond (1960) have referred to it as “removal from a state of stress.”J Empirical evidence relating to pacification under continued stimulation has a long history but one that is composed mostly of bits and pieces. [Some of it is reviewed by Brackbill, Adams, Ct-owell, and Gray (1966).] I t has never previously been the focus of programmatic research so that many of the larger and more important questions have yet to be answered. For example. one of the first that comes to mind is how long such an effect lasts. I n work currently underway at the University of Denver, we are trying to find out whether pacification increases as one increases the number of sensory modalities continuously stimulated. The design of this study requires each infant S to serve as his own control under five difierent conditions: no extra stimulation (the control condition) and continuous stimulation of one, two, three, and four sensory modalities. The particular stimulus conditions being used are as follows: Auditory stinzulritiori. The sound stimulus used is a tape-recorded heartbeat found in previous research to be an effective quieting agent although no better or worse than any other auditory stimulus used in that study (Brackbill ct al., 1966). This particular sound is truly a continuous one, although periodic variation in intensity lends it ;in intermittent character. It is played at 85 db. Ambient noise level during the control condition is 671 db., and all frequencies above 500 H z are attenuated to less than 30 db. Visual stiniulation. l’he visual stimulus comes from two 40-watt fluorescent lamps, approximately 4 feet above S. Illumination during the control session comes from a 50-watt incandescent bulb in a translucent bowl. giving the minimum level that allows u s to monitor state over c I o sed-c i rc u i t t e I e v i si o n . Proprioceptive-tactil~stimulation. Under this condition, the infant is swaddled tightly from neck to toes in long, narrow strips of flannel in the old-fashioned style still used today in some parts of the world.:’This mode of swaddling and the almost immediate effect it has on most young infants, is illustrated in Fig. 1. (A glance at Fig. 1 will also reveal why it seemed necessary to eliminate state 5 [active awake] from the rating scale, since the accurate discrimination of state 5 depends upon the observer’s ability Lipton (’I ~ z l (. 1960) interpreted swaddling :I\ ;i drc.rc,cisc, of \timulation. an interpretation that certainly accords with logical considerations. O n empirical grounds. however. swaddling compels definition as irlrre.u.srd stimulation. since its use produces patterns of behavioral and physiological change that are identical to those found untlei- continuous stimulation of other modalities. ,J

I79

to perceive movement of the body a s a whole.) The swaddling strips weigh 3 ounces; during the control condition the infant is clothed with an extra 3 ounces of shirting or blanketing which d o not, of course, restrict his movements. Temperature stimulafion. During the high-temperature condition, the temperature averages 88"F, and during the control condition, 78°F. To date, 15 one-month-old infants have been tested under all five conditions. Figure 2 shows the principal results tabulated concerning state amount of sleep (states 1 and 2) and amount of crying (state 6) -as a function of the number of sensory modalities stimulated. T h e data are plotted

I80

Yvonne Brackhill and Hiram E . Fitzgerald

State I (Ouiet sleep) State 2 (&five skep)

\

State 6 (Crying) .

I

I

2

3

.

4

Number of modalities stimulated in experimental condition

Fig. 2. Preliminary results showing amount of sleep (state5 I and 2 ) and amount of crying (state 6 ) a s a function of the number of senson modalities stimulated.

in terms of the difference between each S’s performance under the control condition and his performance under one continuously administered stimulus, two continuously administered stimuli, and so on. These results show a very definite additive effect for stimulus conditions: The infant who is continuously stimulated by light and sound and temperature and swaddling sleeps more and cries less than when he is bombarded by only three of these stimuli; in turn, three stimuli are more effective than two, and two are more effective than one. One is not more effective than no extra stimulation -a result not in keeping with previous findings (Brackbill et al., 1966). A final word is in order about the significance of pacification research for practical application. One would not, of course, want to keep a normal baby in a constant state of high-intensity stimulation. For one thing, longterm changes do take place, as Dennis and Dennis noted of Hopi babies who preferred being swaddled (1940).N o adult should be so out of step with his culture that he is unable to sleep except in a brightly lit, hot, noisy room. However, even normal babies have spells of sickness and crankiness when it is advisable to arrange, for the sakes of all concerned, that they cry less and sleep more. Moreover, there are some types of abnormal babies, chiefly prematures, for whom the most important and immediate goal of life is simply to sustain life. For these babies restricting energy output is literally synonymous with survival, and this means not only

maximizing sleep and minimizing crying but also controlling the spontaneous motor discharges that occur with such great frequency in the very premature and that constitute in themselves a real threat to viability. It is probably no exaggeration to say that whether or not one can keep a 1000gm infant from writhing continuously may swing the balance between life and death. Here is a situation in which the long-term application of continuously administered stimulation is more a necessity than an advantage. C. RESPONSETO

C H A N G E I N S l ~ I M I l L . 4 T I O N :THEO R I E N T I N G

REFLEX

The entire foregoing discussion of arousal or state has dealt with the effects of continuously applied, unchanging stimulation. What of the infant's response to the onset of such stimulation or to discrete stimuli of brief duration'? An organism's first response upon sensing a new stimulus or some change in an old one is to attend to it. Pavlov, who was the first to study this most basic, primitive aspect of response to stimulation, called it the orienting reflex. Orienting can be thought of as the preliminary step in processing sensory information (Pavlov also called it the \z~hat-i.s-it'? reflex). The orienting reflex has several identifiable components that have differential probabilities of occurrence, depending upon such factors as the intensity of the stimulus, its signal value. and the age and state of the organism. T h e orienting reflex includes both behavioral and physiological components. They include attempts to localize the source of stimulation; increased muscular tonus and muscular contractions such as eyeblinks or movements of the extremities; diminution of any motor activity that had been going on just prior to stimulation (external inhibition); momentary decreases in absolute sensory thresholds; pupillary dilation; increased galvanic skin response (GSK); a change in E E G toward low amplitude, fast waves, and evidence of a n evoked response; vasodilation in the forehead and vasoconstriction in the extremities; respiratory pause; and change in heart rate (most often seen ;is deceleration). I t has taken about half a century for Eastern interests in the orienting reflex to infect Western research so that until recently practically all studies of orienting in young organisms were of Russian origin." The classic study of orienting in infants was carried out by Bronshtein and Petrova "he Soviet Union has also been the wurce of many theoretical and expenmental refinements in the study of orienting, e.g., the di\tinction between generalized and localized orienting reflexes o r among the adaptive. orienting. and defensive reflexes. Such refinements have as yet undetermined relevance to infant research so they will not be considered in thi\ chapter. The interested reader should c ~ n ~ uI.ynn l t ( 1966) oi- Sokolov ( 1 963).

I82

Yvonne Bmckhill und Hiram E . Fii,-gt>rald

(1952), who used external inhibition (cessation of sucking) as their measure of orienting. [Keen ( 1 964) and Sameroff ( 1967) recently tried, with some success, to repeat this study.] Other Soviet investigations have been concerned with differences in orienting as a function of structural and functional maturity at birth (Polikanina & Probatova, 1955a) and with conditionability of the orienting reflex (Kasatkin, Mirzoiants, & Khokhitva, 1953; Mirzoiants, 1954; Polikanina & Probatova, 1955b). In most of these investigations, a major focus of concern has been to use the orienting reflex, or more specifically, the rate at which it extinguishes (“habituates” in American terminology), as an index of the organism’s ability to inhibit a response. For this reason, premature infants are especially interesting as Ss: Their prematurity presumes structural incompleteness of cortical development, and this, in turn, presumes incomplete development of the functional ability to inhibit responding. In their study of the orienting reflex in premature infants, Polikanina and Probatova remarked of Ss in their most extreme group, who were premature by 3 months: I t is important to note. however. that even at this period in very premature children during momentary repetitions of the sound. the orienting reflex does not extinguish. T h e latter occurs later and very slowly; it is not fully apparent even by the age of 3 months. For example. in one of these infants extinction could not be obtained through repeated application of the sound stimulus even at the age of 3 months and 17 days [Polikanina& Probatova, 1955a. p. 2301.

However, from work being carried out in the Behavior Development Laboratory, it does not appear that the premature’s inability to inhibit orienting to a sound stimulus is quite so clear-cut. In cooperation with Marion Downs of the University of Colorado Medical Center, we are currently studying the behavioral or motor-response components of the orienting reflex, as enumerated on p. 18 1, to auditory stimuli in premature infants. (The sound on each trial is a 2-second burst of 90 db white noise; trials are separated by 10 seconds.) T o date we have tested 38 prematures whose gestational ages range from 26 to 37 weeks (M = 32 weeks) and whose chronological ages range from 1 to 63 days (M = 19.9 days). None of these infants has failed to reach an extinction criterion of five consecutive failures to respond. On the other hand, it is true that the orienting reflex, as enumerated on p. I8 I , to auditory stimuli in premanormal infants matched for chronological age (CA) and for state at the time of testing. For 32 matched cases, the mean number of trials to extinction taken by prematures is 26.00, while the same figure for full-term infants is 18.81. Although this is a substantial difference in relative terms, it should be pointed out that the gestational-age difference between the two groups is also substantial, a mean of 7 weeks for the sample tested to date.

In any event, these data, as well as data from other American studies, are not in full accord with the conclusions drawn by Soviet investigators. Why? Among the several possibilities are t h e following three. The first has to do with a general failure to pay sufficient attention to the parameters of stimulation and stimulus presentation. Studies of orienting in Ss other than infants suggest that the orienting reflex is very sensitive to such stimulus characteristics as duration, interstimulus interval, and others, but parametric studies of stimulus variables have yet to be done on infants. In fact, stimulus characteristics vary so widely from study to study and are reported with such casualness, if at all, that one often gets the impression t h e y were selected for reasons of expedience rather than rep1icabilit y . A second reason for the discrepant findings on orienting may be that there are real differences in responsiveness. Many studies of the orienting response, especially the American ones, have been carried out on neonates since hospitalized Ss are captive and convenient to use. But it is precisely during this period that one expects all CNS-mediated functions to be maximally depressed from the anesthetics and analgesics administered to the mother during delivery. Although there have been relatively few studies of these effects, we do know that responsiveness to visual stimuli is impaired in those neonates whose mothers have been given medication during childbirth (Stechler, I964), and it is difficult to imagine that responsiveness to auditory stimuli w ~ t i l dnot be impaired as well. Some form of anesthesia is the rule in the United States, but it is the exception in the Soviet Union, where a system o f natural childbirth has been in use on a nation-wide scale for over a quarter o f a century. It is quite likely that many real differences in neonatal behavior do exist between the two countries' populations of newborns. A third possibility underlying the discrepancies in results stems from investigators' failure to take into account the infant's state at the time of stimulation. There is no doubt that t h e orienting reflex does differ both in qualitative and quantitative aspects depending on whether the infant is asleep or awake at t h e time of stimulation. (More will be said about this point later .) Orieritirig to Sociully Sign$crrrir StirTiirli In the United States, pupillary reactivity has for the most part been conceptualized not as a component of the orienting reflex but rather as an index of affective responsiveness, piipillary dilation being regarded as an indicator of pleasant experience and constriction as a measure of unpleasant experience (Hess, 1060. Notice that in the case of pleasant

184

Yvonne Bruckhill und Hirurn E . Ficzgerald

experience the same outcome, pupillary dilation following stimulus presentation, is predicted from both the orienting and affectivity frames of reference regarding pupillary activity. However, when an unpleasant stimulus is presented, the two different perspectives suggest different outcomes: From an orienting point of view, the response should still be dilation; whereas from an affectivity point of view, it should be con~ t r i c t i o n Thus, .~ from either point of view, presentation to a baby of a picture of his own mother should be followed by dilation. On the other hand, according to the orienting point of view, presentation of a stranger’s face should still be followed by dilation, but, according to the affectivity point of view, it should be followed by constriction, or at least should not be followed by dilation. (This assumes, of course, that S s are old enough to discriminate between mothers and nonmothers.) Fitzgerald’s recently completed study ( 1968) was designed along these lines of investigation. H e confronted babies with pictures of their mothers and of a female stranger and compared pupil diameters before and during stimulus presentations. Fitzgerald found that nine of his ten 4-month-old Ss, most probably the only group old enough to have made any significant progress toward a mother-stranger discrimination in real, three-dimensional life, showed pupillary dilation upon viewing a stranger (Fig. 3, 10% by Hess’s method of measuring change). These same S s , however, showed no consistent response to pictures of their mothers. In general, the results suggest that orienting to novel stimuli is the more influential determinant at this age of pupil change under constant illumination. D. STATEA N D RESPONSIVENESS TO STIMULATION

Two important questions yet to be explored systematically in developmental psychology concern the interaction of the orienting reflex and arousal level. In what way does responsiveness to stimulus onset depend upon preexisting state, i.e.. the infant’s state at the time of stimulation? I n what way does arousability depend upon preexisting state‘? At present the only possible answer to either question is “in some way,” since currently available evidence is scanty and some of it contradictory. Moreover,judging by the number of contradictions and qualifications apropos the same questions that have emerged from research with adult human beings and subhuman species, it will take some time and a ‘These two point\ of view are not neceswr-ily conrradictory. hlomentai-y initial dilation can precede constriction but remain undetected when the measure used involves averaging pupil diameters over several seconds rather than a trial-by-trial examination of pupil size. Another consideration here is that pupillary constriction is by far the stronger and faster of the two unconditioned pupillary reflexes.

185

Fig. 3. Photograph of a n injhnt ,gtrzing (it the televised picture o f his mother a s u n e.rperimc~nterphotographshis pupillury w c i c t i o t i t o this srirnulits (Fitzgernld, 1968).

great many research studies before definitive answers are forthcoming. When the question of infant responsiveness during sleep is considered in terms of specific monosynaptic or polysynaptic reflexes, contradictions are more prevalent than agreements in the literature. Thus, for example, Prechtl, Akiyama, Zinkin, and Grant ( 1968) find t a t one component of the lip-tap reflex, the lip-jerk, is greater, both in terms of probability of occurrence and amplitude, during quiet sleep than active sleep but that just the opposite is true for the other component, lip-protrusion. In his article on the palmomental reflex in premature infants, Parmelee remarked that “Though the palmomental reflex was somewhat more easily obtained in babies awake than asleep. it was nevertheless obtained with great frequency during sleep and in three out of four infants considered to be in coma. Thus the response does not seem to be very dependent on state” (1963, p.384). It looks at present as if more congruence will result from considering responsiveness in terms of the specific modality stimulated rather than in terms of a specific reflex or response. By way of illustration, Table I1 con-

T A B L E II SI EEPING

K E S P O N S I V E N E S S .TO S T I M U I . A T I O N IN

I N F A N T S AS A

JOIN-I FUNCTION

OF S L E E P S T A T F A N D S T I M U I . U S M O D A L I T Y

Sleep state

Percent change in motor movement of twelve neonates“ Painful Tactile Vestibular Auditory stimulation stimulation stimulation stimulation (jarri ng)

Quiet sleep Active sleep “

”

94.1

96.3

57.1 61.8

47.5 13.3

19.1 44.x

Percent increased motor movement in eighteen I month-old infants” Auditory stimulation 5.6 22.2

From Wolff ( 1966). From Brackbill f t r r l . (unpublished obsei-vations)

tains data from two studies of responsiveness as a function of state and sensory modality. The first of these studies, by Wolff ( 1966), used as criteria of responsiveness both increased motor movements (if the preexisting state had been quiet) and decreased motor movements (if the preexisting state had been active). The second set of data comes from an unpublished study carried out by Brackbill, Fitzgerald, and David Metcalf, of the University of Colorado Medical Center, on responsiveness of 1 -month-old babies to discrete auditory stimuli as a function of ( a ) the nature of the measure of responsiveness (EEG and evoked response as opposed to behavioral measures), ( h )background auditory condition (quiet vs. noisy), and (c) state of the organism at the time of stimulation. The criterion of a motor response to the auditory stimulus was agreement by two judges that a definite startle-like pattern had appeared on stabilimeter and arm movement recordings within 2 seconds of stimulus onset. From the data shown in Table 11, it appears that vestibular stimulation is more effective in producing a response during quiet sleep than during active sleep, that tactile and painful stimuli are equally effective in both states, and that auditory stimulation is more effective during active than during quiet sleep. The agreement between Wolff s data and ours on responsiveness to auditory stimuli is reasonably good if one considers the difference in Ss’ ages and in the criterion of “responsiveness.” [Wolff has found ( I 966), as we have, that the probability of a spontaneous startle, i.e., a startle to no apparent external stimulation, is greater in quiet sleep than in active sleep.] Another variable that we have found to affect responsiveness during sleep is the type of measure one uses a s the index of responsiveness. Up to this point we have spoken only of motor movements, changes ef-

fected by the skeletal niuscitl;ititt-e. A rather different picture emerges when we consider the evoked I-ehponhe. Under the usual quiet laboratory conditions, evoked response aniplitude is higher when the subject is in quiet sleep rather than active slecp. This is apparently true both for adults (Goff, Allison, Shapiro, & Knsner, 1966) and for infants (Pi-echtl et al., 1968). In our laboratory we have found the two amplitudes to be on the order of 17.2 and 12.0 p V . respectively. This greater responsiveness to auditory stimuli during quiet \leep than during active sleep is, as the reader will recall. just the opposite from the active-quiet response differential found when motor movement is uvxl as the index of responsiven e s s .'; Stritr rind Arousrihility

from Slcop

Almost no developmental data ;tre available regarding the interaction of state and arousability. I t would be, of course, outside the scope of this paper to review in detail the results from studies of adults that are pertinent to this question. However. it i 4 worthwhile mentioning, if only to suggest some of the directions that future developmental research might take, some of the major findings regarding arousability in adults. It appears that adult Ss are more easily awakened from the KEM state or from state 2 than from delta sleep (states 3 and 4) (Kechtschaffen, Hauri, & Zeitlin, 1966; Stoyva, personal communication) although the clarity of this difference in arousability disappears after the first 3 hours of a night's sleep o r when the stimulus to i i aken ~ is a painful shock (Pisano, Rosadini, Rossi. & Zattoni, 1966). ( I n genet-al. this agrees with a study of young infants recently completed i n o ~ i rlaboratory in which we observed 64 instances of spontaneous awakening and found that in 83% of these instances the sleep state existing just prior to the infant's awakening had been active rather than quiet sleep.) Among the other variables that have been found to affect arousability in iiclults, often in interaction with each other, are the following: ( n ) stiniuliis parameters such as intensity and meaningfulness or signal value to S (e.g.. Buendia, Sierra, Goode, & Segundo, 1963; Wilson & Zung, 1966): ( h )degree of fatigue (e.g., Williams, Hammack, Daly, Dement. & I .ubin. 1964); ( c )time of night, or more precisely, cumulative sleep time since the beginning of the session (e.g.. a pel-sonal communication. 1)i- I homa\ Williams of the National In.;titute o l Mental Health reports that he and D r . Joscph Schacter of Columbia University are now analyzing heart rate data that so far reveal no cle:d\ discer-nible differences in responsiveneb\ during R E M a s compared with NKEM sleep. I he slimuli used were repetitive. I-millisecond. 100db clicks. and the auditory backgrounti condition was a constant random noise lebel of 7 5 db. T h e S s , neonates. were inimobili,ed i i i air rplints during testing sessions.

188

Yvonne Bruckbill and Hiruni E . Fitzgeruld

Rechtschaffen et al., 1966; Williams et al., 1964); and ( d ) sex of S (e.g., Wilson & Zung, 1966). As a final discomforting note, we should mention that results have already appeared in the sleep literature indicating definite species differences when adult human beings are compared with adults of subhuman species. For example, one of the distinguishing features of REM periods for subhuman species is a sharp decrease in muscle tonus throughout the body, while in human beings this decrease is restricted to the muscles of the head and neck.

111. Conditioned Responses to Stimulation During the past few years we have been engaged in a program of experiments with the intent of exploring in a systematic way parameters of perceptual development and learning in infancy. The primary orientation of these studies has been toward testing two principles advanced by Soviet physiologists. T h e first principle holds that there is an immutable developmental order in which conditional stimuli become effective in establishing a conditioned response. According to this view, vestibular stimulation is the earliest effective conditional stimulus (CS), followed in order by auditory, tactile, olfactory, gustatory, visual, and thermal stimuli (Brackbill & Koltsova, 1967). [It has been suggested (Brackbill & Koltsova, 1967) that time as a C S should probably be at the very earliest end of the developmental scale, but among true Pavlovians time discrimination is regarded a s a capacity intrinsic to all sensory analyzers rather than as the work of a separate sensory analyzer.] The second principle that derives from Soviet physiology and that has guided the direction of our research is that the nature of the unconditioned stimulus (UCS), and consequently the natures of the unconditioned response (UCR) and the conditioned response (CR), are not important factors in classical conditioning. If a particular C S is effective at all in conditioning, then any response that an organism is capable of making can be conditioned to that CS. In spite of the uniformity with which these beliefs are held, there are no comprehensive or systematic studies in the Russian literature that will confirm or deny these propositions. Instead, the beliefs are referable only to a vast amount of unpublished research experience and to widely scattered, typically single-variable studies. The American and Czech literatures similarly lack information on a possible rank ordering by C S modality during early infancy. One reason for this is that the Americans, at least, have never previously considered

the question. A second reason is t h a t American and Czech investigators have generally used the same type of C S , auditory, from one study to the next. This is largely because auditory CSs are in many ways the easiest to use, from the viewpoint of methodology, at early age levels. (For example, the infant cannot escape the action of an auditory stimulus to the extent he can that of a visual stimulus.) I t should be pointed out that challenging the proposed rank order means, in effect, posing a null hypothesis: posing. for example, that a visual stimulus cannot successfully be used in establishing a C R at a s early an age as an auditory CS. The available experimental evidence is too thin to give much support to such ;I null hypothesis. With additional experiments, using C Ss in different modalities and using Ss of different ages, evidence for o r against the hypothesis should begin to emerge -although like any other null hypothesis this can never really be "proved." The second principle, that the CS i s important and the UCS is unimportant in classical conditioning, is also insufficiently supported by experimental evidence. In fact, the evidence that is currently available suggests that the nature of the U C S is an important factor in infant conditioning. It might be pointed out in this respect that if the UCS does determine the outcome of conditioning, then the validity of the principle of rank-ordering stimulus modalities in terms of their effectiveness as C S s is even more seriously in doubt. The UCS-UCR combinations of airpuff and eyeblink, bright light and eyeblink, food and sucking, shock and limb withdrawal, and shock and GS R account for a majority of the conditioning studies with infant Ss. (The orienting response and cardiac and vascular changes have also served as U C R s in a few studies.) Not one of these UCS-UCR combinations has been paired with CSs trorn all modalities with infant Ss; in fact, relatively few of the many possible ('S-UCS pairings have been investigated at all. Our experimental program is attempting, as one of its aims, to introduce systematization into this area. It is worth adding that if there is indeed a developmental sequence of effectiveness of CS modalities i n classical conditioning, this presumably must depend in turn on a sequence of development of cortical (or at least central nervous system) interconnections. Certainly the simple visual stimuli used for conditioning are clearly sensed well before the age of 40 days, yet this is supposedly the earliest age at which a C R can be established to a visual CS (Brackbill Kr Koltsova, 1967, p. 2 18). Ineffectiveness of a visual CS cannot be attributed t o a failure to sense on t h e part of the infant. Neither can it be attributed simply to immaturity of neural or motor mechanisms necessary to conditioning in general since a C R to a vestibular o r an auditory CS can be established before this age. Logically, it

seems the failure must be due to some as-yet-undeveloped interconnections between the visual centers and the motor centers. Assuming that this is true, then it seems profitable to speculate a little further and to suggest that there is no compelling reason to assume that interconnections from a particular sensory area will develop to all effector areas simultaneously. If this is true. then there should be a C S by UCS interaction, developmentally, and it would become necessary to pair each C S modality with each response in order to trace out the interactions. This is not a prospect that invokes lightheartedness and joyous anticipation, but then, neither psychology nor neurophysiology has a reputation for simplicity. I t remains possible, however. that a simpler categorization of interactions might represent the true state of affairs, i.e.. that C R s can perhaps be grouped as autonomic vs. somatic or that UCSs can be grouped as appetitive 1’s.noxious. The studies to be described have something to say to this point, but much more evidence is necessary before any conclusions may be drawn with confidence. In the Behavior Development Laboratory. the infant conditioning studies recently completed or currently underway have dealt with an autonomic response (the pupillary response) and a somatic response (the eyeblink). The CSs have been either auditory, tactile, or temporal (elapsed time). T o be more specific, the CSs that have been used thus far in our laboratory and the responses with which they have been paired, are: temporal CSs with eyeblinking and pupillary responses: an auditory CS with eyeblinking and pupillary responses; a compound C S consisting of time plus sound with pupillary response nd a tactile CS paired with pupillary constriction. Three of these studies have also been done with adults for a developmental comparison of the conditioning involved. All of our classical conditioning experiments have been planned with as many common components 21s possible in order to maximize their- comparability. Almost all Ss for these studies come from the same population and are of like age. In addition, a partial reinforcement design has been used consistently. with the ratio of reinforced to test trials averaging 3.5: 1. Finally, the experimental room and general surroundings are the same from one study to the next. Brief descriptions of these studies follow. A . TEMPORAL ~ONDIIIONING

For the most part, temporal conditioning studies have been carried out by Soviet investigators and usually with infrahuman Ss. Three investigations (Bystroletova, 1954; Krachkovskaia, 1959; Marquis. 194 1 ) have studied “natural” temporal conditioning in human infants in connection

with feeding schedules. although only one of these studies, Bystroletov a’s , was actual 1y c o nc e i ve d iis t e iii por i i I conditioning by the e x pe r i in e n ter. None of the three investigiitions is Iree of methodological flaws; however, their combined results suggest that time is indeed an effective CS within the first 1 0 days of life. More recently, Lipsitt and Anibrose ( 1 967) reported successful temporal conditioning with a 30-second CS in fifteen Ss ranging in age from 3 to 5 days. These investigators used auditory, 01factory, and vestibular stimuli ;is lJCSs and heart rate, respiration. and body movement as CKs. The paradigm for temporal cc)nditioning is simply that the interval from one U C S onset to the next is constant throughout conditioning sessions. This period of elapsed time is the CS. and a test trial consists of withholding the UCS and noting whether. at this time, a response appears despite the absence of the UCS. 1 . Trmporul C S in Piipill~iryCcrtrtlitiotritig The experimental setting for pupilhry conditioning i n this experiment (Fitzgei-ald. I-intz. Br-ackhill. R Atlam\. 1967)and in subsequent pupillar-y conditioning experiments, was ; I I i-;tngrti iis shown i n Fig. 4. The CS was a 20-second period of elapsed tinie. and the UCS was ;t change in illumination level. For conditioning dilation, ii 100-uatt blue bulb. 15 inches in front of the subject, was tut-tied oft‘ t o i - 4 seconds: for conditioning constriction. the same bulb, norrii;illv olf. was turned on for the it-second UCS duration. Hunter timers controllecl (’S kind UCS duration. The pupillar-y response was recorcletl on iiifr;ired tilm by a Bolex 16-mm motion picture c;inier;i driven at one li-;ime per second by an external synchronous motor. A 4-inch telephoto Icn\ with extension tubes permitted photographing a I .S-inch square :ii-e:i of’ s ’ s face from a distance of approximately 3 feet. A small red pilot hulh taped above S ’ s left eye arid shielded from his view provided a record of c\etits on the film. A mirt-or reflected an image of S’s left eye thi-ough ;I tuhc to the camera outside the booth. Light for photography came froin t h o 25-watt red twlbs, 12 inches in front of S . which were turned on A I :ill times during experimental sessions. A red filter on the camera len\ elYecti\ely blocked the predominantly blue illumination from the UCS lami> s o that exposure of the film was practically independent of t h e state ot’ the II(‘S lamp. One experimenter inside the booth held S ’ s head in position and. when necessary. also held S ’ s lcft eyelid open. After processing, the films wcic pt-oJectetlon a Kekordak viewer. ‘The scorer adjusted ii caliper t o iiiiitch the piujected pupil diameter and pressed a ’’record but t o n . A 11 t o i 1i;i t i c i i na I og- t o -d i g i t al conversion ecl u i 1)nient. compensated for the enlaigerriciit and reduction steps between S ”

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F i g . 4 . A scaled rrpresentntion of the inside o j ’ r / i e experinientul boorh. The picture s h o ~ , s pupillary photogrcrpliy.

t/7e crppnrcitus necessary f o r

and the projected image. printed actual pupil diameters to the nearest hundredth millimeter. Interscorer reliability checks with this apparatus yielded correlations ranging from .90 to .96 (median = .94). The 20-second elapsed time CS was not chosen arbitrarily. In pilot temporal conditioning work with infants, a 1 0-second intertrial interval (ITI)was tried but proved too short: 10 seconds after one U C S presentation, the pupil was still in the process of recovery. Consequently, we collected data on recovery time from both constriction and dilation with both infant and adult Ss. On the average, recovery from the 4-second duration of the 100-watt UCS used in these experiments was essentially complete after 14 seconds. Therefore, a 20-second interval from UC S offset to UCS onset was adopted as the temporal C S . Sixteen infants with a median age of 54 days served as Ss. There were two experimental groups (dilation U C R and constriction UCR) and two

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pseudoconditioning control groups (dilation and constriction) with four Ss per group. I n a single session, 32 paired presentations of C S and UCS were given to each experimental S . Nine test trials, on which the U C S was omitted, were randomly interspersed among t h e conditioning trials. Without interruption, 35 extinction trials followed. For half the Ss:the U C S was offset of the 100-watt lamp, and for the other half the UCS was onset of the lamp. The control groups also received 32 paired presentations of CS and UCS, and nine intermixed test trials, but the IT1 was varied randomly between 10 and 30 seconds (and averaged to 20 seconds) rather than the constant 20-second interval used for the experimental groups. The data on pupil size for all comparisons were from all photographic frames collected during the 4 seconds immediately preceding each test trial and the 4 seconds of the test trial itself. For conditioned dilation. difference scores were obtained by comparing the single largest diameter during a 4-second test trial with the single largest diameter during the corresponding 4-second pretest period. For conditioned constriction, the difference score was the single smallest test diameter compared with the single smallest pretest diameter. Difference scores were obtained in the same manner for all extinction trials. The data were analyzed using f tests for the difference between the correlated pretest and posttest nienns. The mean pupillary change for the experimental dilation group was +. I 1 m m ,and the mean change for the experimental constriction group was - - . 3 1 mm. Both differences were significant (in both cases, PiF 2

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controlled, and the stimulus cannot be easily overlooked or escaped (unlike a visual stimulus). The impetus for the auditory conditioning studies to be described was our wish to pair an auditory CS with the UCSs used in temporal conditioning under conditions comparable to those used in the temporal conditioning studies. 1 . Auditorv C S in Pupillary Conditioning

The S s in this experiment (Brackbill et ul., 1967) were 32 infants with a median age of 53 days. Four Ss were assigned to each of six experimental groups and two control groups. T h e experimental groups differed in terms of the C R (constriction vs. dilation) and interstimulus interval (1.5 seconds, 6 seconds, or 9 seconds). For the pseudoconditioning control groups, constriction and dilation U C R s were combined with the limiting case of backward conditioning, i.e.. a 0-second interstimulus interval (ISI). T o avoid conditioning to time, the intertrial intervals were randomized for all groups; they ranged between 10 and 30 seconds, with a mean of 20 seconds. As in tcrnporal conditioning, each S received 39 conditioning trials intermixed with nine test trials in a single session. The CS was a 65-db complex sound, with experimental groups receiving CS onset either I .S,6. o r 9 seconds prior to the onset of t h e 4-second UCS. For the control groups, onset of the CS was simultaneous with the onset of the UCS, i.e., a 0-second IS1 was used as described previously. I n all groups, C S and UCS ended simultaneously. The apparatus for controlling intervals. recording the response, and scoring the records was the same a s described earlier. DiFerence scores were derived by comparing pupil diameters during the 4-second test trial intervals with the 4-second intervals preceding CS onset on test trials. As in the temporal conditioning experiment, f tests for the differences between correlated means were used in analyzing the results. There was no evidence of conditioning in any group. Although the pupillai-y response could be conditioned to time as a CS, it apparently could not be conditioned to an auditory CS. However, it irernained possible that with more conditioning trials a CR might be established. Therefore, one infant (S weeks old) was run through six conditioning sessions, on successive days, with a maximum of 68 reinforced trials and 20 intermixed test trials per session, for a total of 392 paired presentations of CS and UCS. Even at the end of this extended period, this S showed no evidence of conditioning. It seems likely that pupillary conditioning to an auditory C S is impossible at this age. Using the same design, and as far as possible the same procedures, the study of auditory conditioning of pupillary dilation and constriction was repeated with 32 adults. Again there were eight groups of four Ss: con-

striction and dilation experimental groups with CS onset 1 . S , 6, or 9 seconds before U C S onset, and control groups with simultaneous onset of C S and UCS. One of the four Ss showed conditioned dilation and three of four conditioned constriction when the IS1 was 1 .S seconds. N o subject conditioned in the 6- and 9-second IS1 groups. Apparently the pupillary response can be conditioned to an auditory C S in at least some adults and under some conditions.

2. Auditory C S in Eyeblink Conditioning Twenty infants were used in this experiment (Lintz, Fitzgerald, & Brdckbill, 1967). Their ages ranged, at the beginning of the experiment, between 3 3 and 133 days, with a median age of 69.5 days. Eight Ss were used in the experimental group and four S s in each of three control groups. All details of UCS presentation and of recording the response were the same as described for temporal conditioning of the eyeblink. The CS was a tape-recorded sound, 0.20 second in duration, played at a 65-db level. Intertrial intervals were random between 30 and 60 seconds (mean = 39.2 seconds), and the interstimulus interval was 1 .OO second. Each daily session consisted of a maximum of I9 conditioning trials with six intermixed test trials. A session was ended if the infant could no longer be maintained in a state of quiet alertness. A relatively stringent criterion of conditioning, nine C R s in ten successive test trials, was adopted. All eight experimental Ss reached this criterion. T h e number of paired CS-U(’S presentations up to, but not including, criterion ranged from SO to 774. In Control Group I , Ss received the same total number of C S and U C S presentations as the four slowest conditioners in the experimental group, but C S and U C S were never paired for this control group. Control Group 1 I received random-interval presentations of CS only. Control Group 111 received no CS o r UCS presentations and furnished a measure of spontaneous blinking. The test-trial results for the experimental group and for the major control condition, Control 1, are shown in Fig. 6. For Control I I , the probability of a blink to the C S was .OX. For Control I I I , the probability of a blink during any of the 1.3-second intervals that corresponded in time with CS presentations administered to Ss in Control I I was .06. Clearly. the eyeblink was conditioned to an auditory CS. 3. S u m m a s y of Auditosy Conditioning These experiments demonstrate that an auditory C S is effective in conditioning a n eyeblink response with infant Ss. An auditory CS is not effective in conditioning a pupillary response with infant Ss, but is effective in some cases with adult Ss.

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Because time had been an effective CS in conditioning pupillary responses in infants and because sound had been totally ineffective, we were interested in presenting a compound CS combining the temporal CS used in infant pupillary conditioning with the auditory CS used in the same procedure. Eight Ss, 32 to 67 days old (median = S 3 ) , were run in the same procedure as in temporal conditioning of the pupillary reflex, except that t h e 65-db complex sound used in auditory conditioning accompanied the UCS presentations. O n test trials, the sound was presented at the standard 20-second interval after the preceding UCS had terminated, but the UCS was omitted. Data were scored and analyzed exactly as for temporal pupillary conditioning. Both conditioned constriction and conditioned dilation were successfully established in every S. N o pseudoconditioning control groups were run specifically for this procedure. The control groups for temporal conditioning already indicated that UCS presentations at random intervals which averaged 20 seconds did not result in a pupillar-y response that could be mistaken for a CR. Similarly, the control groups for auditory conditioning already indicated that unpaired presentations of C S and UCS did not result in sensitization, i.e., that the sound component of the compound stimulus did not evoke a pupillary response in the absence of conditioning. I n addition, of course, our failure to find conditioning in the auditory CS groups also establishes

that the sound component alone should not contribute to any observed response. Response magnitudes of the (‘Ksin temporal and in compound conditioning were compared, and significant difyerences ( P < .01) were found for both dilation and constriction. l’he compound CS produced a larger dilation CK than did time alone, but time alone produced a larger constriction C R . The direction of this diffcrence is, in both groups, consistent with the fact that sound on its initial presentations evokes pupillary dilation. However, the results from the control groups who received random-interval unpaired presentations of ( - S and LJCS indicated that the sound CS did not. at least after the first few presentations, evoke a pupillary response. The reason for this diffet-ence cannot be satisfactorily explained by the available data. Because we had found that adults did not condition to a temporal CS and that some adults did condition to an auditory CS, the compound CS of time plus sound was also used in an attempt to condition pupillary dilation and constriction in adult Ss. Only one of four Ss in the dilation group and one of four in the constriction gtoup showed evidence of conditioning. I).

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Brackbill and Koltsova (1967. p. 2 7 6 ) pointed out that very little systematic work exists on tactile stimulation in conditioning. I n fact, Spears and Hohle (1967) devote only two paragraphs to summarizing what is known of pressure and touch sensitivity i n infants. However, a tactile stimulus can easily be used in classical conditioning, without elaborate apparatus, and the very lack o f knowledge about a tactile CS makes it an interesting modality for classical conditioning studies. The experiments described in this section are ;is yet incomplete, and the results in some cases must be regarded as preliminary rather than final.

Tactile CS in Pupillurv Conditiotiitig This experiment uses much the same procedure and apparatus as was used in the pupillary conditioning experiments already described. However, the services of a second experimenter, inside the booth, are required to time lTIs with a stopwatch, to initiate one cycle of the timers by pressing a silent pushbutton, and to deliver the tactile CS at the appropriate times by stroking the sole of S’s foot with a large camel‘s hair brush. The ITls range between 10 and 30 seconds: CS onset is 1.5 seconds before UCS onset; and the CS overlaps with the 4-second UCS but terminates before it ends. The UCS is not presented on test trials, which are randomly intermixed with conditioning trials in :I I : 3 ratio. Subjects in the pseudocondi-

tioning control group receive presentations of the CS and UCS in intermixed but unpaired order. Light onset is the UCS, and constriction the CK. Ten Ss, with a median age of SO days. have been run to date in the conditioning procedure, with total numbers of conditioning trials ranging from 33 to 100 (mean = 56). Only one of the 10 Ss showed evidence of conditioned constriction. Two Ss of the experimental group were seen in repeated sessions, on successive days, to check on the possibility that conditioning might occur following a greater number of reinforcements. These Ss received 343 and 240 conditioning trials. respectively. but neither showed any evidence of conditioning. For the Ss in the control group, alternate CS-only trials were scored, taking a s prestimulus diameter on each trial the single smallest diameter during the 4-second period preceding CS onset and as test diameter the smallest during the 4-second period beginning 1 .S seconds after CS onset. Two Ss showed no significant response to the CS, and one showed a significant response ( P < .()I). Figure 7 shows. in blocks of C S presentations, t h e average data for the 3 Ss run so far under the control procedure. There is a tendency, at least during later trials, for the tactile CS to elicit a constriction response; the explanation of this is not clear. All in all, however, it seems that the failure to condition in the experimental Ss cannot be attributed to any effects of the CS itself; in fact, CS effects should have favored finding a significant constriction response in the experimental Ss. The parsimonious conclusion, based on currently available data, seems to be that pupillary conditioning t o a tactile C S is not possible under the experimental conditions we have used, and that the one experimental S who did show a conditioned constriction response was probably showing nothing more than a response elicited by the C'S. i.e., that this was pseudoconditioning rather than true conditioning. E.

S U M M A R Y 4 N D C O N C l USIONS

We have used CSs from three modalities, time, auditory, and tactile, in our studies of infant classical conditioning. In addition, we have used a CS compounded of time plus sound. All four of these have been used in attempts to condition both pupillary dilation and pupillary constriction. The time and auditory CSs have, in addition, been used in experiments attempting to condition the eyeblink reflex to an airpuff. 1. The Soviet Developmental Sequence of Conditionability One of our research interests is to find whether or not there is an invariant sequence, developmentally, in which CS modalities become effective in

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classical conditioning. An additional interest, closely related to the sequence of conditionability, is to determine something of the importance (or, in the Soviet view, the unimportance) of t h e nature of the response to be conditioned. The conclusion4 to be drawn from our studies that bear on these points seem plain: l'here is not an immutable developmental sequence of CS modalities, nor is the outcome of conditioning predictable without taking into account the response that is being conditioned. I t appears that any adequate developmental theory of conditioning must deal not only with CS modality but, also. on some basis with the response. When two CSs in difTei.enr moclalities can both be perceived by S. but one is effective in conditioning a response and the other is not efTective in conditioning the same I-esponsc, then it seems that there must be differential rates of maturation of' the cei-ebral structures that serve as the central portions of conditioned rellex arcs. When S is perfectly capable of making two responses, and one of those responses can be conditioned to a particular CS but the other response cannot be conditioned to the same CS, again it seems that difl'ei-ential maturation of cerebral structures must be responsible. With infant Ss, the autonomic response did condition to time as ;I CS and did not condition to auditory or Lactile C S s : the eyeblink response conditioned to an auditory CS bul not to time. Tentatively, it seems possi-

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ble that a contrast between autonomic and somatic responses may be useful in predicting the outcome of conditioning studies in that the pupillary reflex is an autonomically controlled response whereas the eyeblink reflex is somatically controlled. Such a conclusion must remain tentative, of course, until the conditioning outcomes for other autonomic and somatic responses have been determined. As an interesting, and purely speculative, basis for explaining the CS by UCS interaction in classical conditioning of infants, adaptive significance for homeostasis is a possibility. Of all the sensory modalities, it seems logical that time and temperature are the two which, very early in life, should require an autonomic response from the organism in order to maintain homeostasis. For these two modalities, then, the early establishment of interconnections between sensory structures and autonomic effector structures would be of greater adaptive significance than, say, an interconnection between the visual sensory system and the autonomic effector system. This hypothesis would suggest that in classically conditioning an autonomic response, time and temperature should be the CS modalities that are effective earliest in life. Unfortunately, there seems to be no study that has paired a thermal CS with an autonomic response and that has used very young Ss, either human or animal. Usoltsev and Terekhova’s (1958) study used a somatic response (the eyeblink reflex to an airpuff). 2. Sensory Analyzer Function in Infants With regard to sensory analyzer function in infants, our results with the temporal CS are of particular interest. The literature on time perception (summarized by Brackbill et al., 1967) is extensive, but there has been little research with infant S s . The most pertinent references are those of Hellbriigge (1960) and Lobban (1965) on developmental phases in the acquisition of diurnal rhythms. Hellbriigge’s results indicated that cyclic rhythms for skin resistance, temperature, and heart rate appear at 1, 4, and 6 weeks of age, respectively. Lobban’s review of the literature led her to conclude that there is “. . . good evidence for the existence of true endogenous physiological diurnal rhythms in man” (p. 381). She also points out that all the diurnal rhythms of older children and adults appear to develop from polyphasic rhythms which, in her opinion, appear “independently of external stimuli” (p. 380). Our results for temporal conditioning of the pupillary response indicate that infants at least as young as 26 days can accurately perceive and respond to the passage of a short standard interval of time (20 seconds). The results for conditioning stereotype pupillary responses suggest that 2-month-old infants can also perceive temporal patterns, although with considerably less accuracy than is found for a single interval.

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An interesting issue is raised by the contrast between the pupillary conditioning results with infant S s and with adult Ss. All infant Ss did condition to the temporal CS, but no adult S showed clear evidence of conditioning. In addition, although n o infant S showed a conditioned pupillary response to an auditory CS, whether the IS1 was 1.5, 6, or 9 seconds, four of eight adult Ss did show pupillary conditioning to an auditory CS with a I .5-second ISI. Given, then, that it is possible to condition a pupillary response in adults, and given that a temporal C S was uniformly successful for such conditioning in infant Ss, it is sui-prising that the temporal C S was completely unsuccessful with adult Ss. There is nothing in the Soviet or American literature on conditioning that would suggest an inverse relationship between age and the effectiveness of a C S modality for conditioning; yet that is apparently the state of affairs for a temporal CS. Certainly the literature establishes that children do a great deal of learning with regard to time and time concepts. (‘ertainly, too, it is possible that time perception begins in infancy as a function of the first signal system (in Soviet terminology), but that with progressive acquisition of facility in language, time perception becomes more and more a function of the second signal system. At any rate, we believe that further studies of time perceptiop in the human infant are necessary and are of potentially great value in contributing to our knowledge of sensory development.

3 . D evelopni en tal Di’erences in Contiit ion ing The contrast between adult Ss and i n f m t Ss in pupillary conditioning, described in the preceding section, points to developmental changes in sensory analyzer function, or in conditionability, or both. I n any case, whether the change in conditioning outcome is caused by learning new ways of processing time information that supplant an earlier and perhaps more primitive (but nevertheless surprisingly accurate) way, or whether caused by maturational changes in neural structures, the course of conditioning the pupillary response to time is markedly different, and less effective, in adults than in infants. Obviously. infant conditionability is not the same as adult conditionability, nor is the first simply a less well-developed or less efficient version of the second. Generalizations from adult data can be in error, and the need for additional developmental studies is apparent.

Brackbill, Y . , Adams, G . , Crowell, D. H . , Xr Gray., M . L. Arousal level in neonates and preschool children under continuous auditory stimulation. Journal of Experinienral Child Psychology. 1966.4, 178- 188.

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Brackbill, Y., Fitzgerald. H . E., & Lintz, I.. M. A developmental study of classical conditioning. Monographs of /he Society f o r Rrseurch in Child Deve/(Jpnfen/. 1961, 32, No. 8. Brackbill. Y . , & Koltsova, M. M . Conditioning and learning. In Y . Brackbill (Ed.). Infuncy find early childhood. New York: Free Press, 1967. Pp. 207-288. Hrackbill, Y., Lintz, L. M., & Fitzgerdld, H . E. Differences in the autonomic and somatic conditioning of infants. fsychosonzutic Medicine. 1968, 30. 193-20 1 . Hronshtein. A. 1.. & Petrova. E. P. lssledovanie zvukovogo analizatora novorazhdennykh i detei rannego grudnogo vozrasta. ( A n investigation of the auditory analyzer in neonates and young infants.) Zhurnal Vysshri Nc.rvnoi Deiatrlnosri, 1952, 2, 333-343. (Reprinted in Y . Brackbill & G. Thompson (Eds.), Behavior in infan(.!, and ear/y childhood: A book ofreadings. New York: Free Press, 1967.) Ruendia, N . , Sierra, G . . Goode. M., & Segundo. J . P. Conditioned and discriminatory responses in wakeful and in sleeping cats. Elrc.froancPphaloarciphycind Clinical Neurophysiology. 1963. Suppl. 24, 199-2 18. Bystroletova, G . N . Obrazovanie u novorozhdennykh detei uslovnogo refleksa na vrernia v sviazi s sutochnym ritrnom kormleniia. (The formation in neonates o f a conditioned reflex to time in connection with daily feeding rhythm.) Zhurnrrl Vyssliei Nervnoi D e i a telnosti, 1954, 4, 601-609. Dement. W.. & Kleitman. N . Cyclic variations in E E G during sleep and their relation to eye movements. body motility. and dreaming. Elcctroeric.ephaloyraphy and Clinical Nelrroph>JsiolOgy.1957. 9. 673-690. 1)ennis. W.. Xr Dennis. M . C i . The effect ofcradling practices upon the onset of walking in Hopi children. Journul ofGerwric. Psychology, 1940, 56. 77-X6. I-itLgeraltl. H . E. Autonomic piipillary reflex activity during early infan Social and nonsocial visual stimuli. Jorrrnu/ ofExpc2rinwn/o/ Child fsycho/ogy, 1968, 6, 470-4x2. f-itzgerald, H . E.. Lintz. 1.. hl.. Brackbill. Y . . Xr Adam\, C;. Time perception and conditioning a n autonomic responw in human infants. Percrp//rul und Moror Skills. 1967, 24. 479-486.

(;off. W . R.. Allison. T.. Shapiro, A., & Kosnei-. B. S. Cerebral somatosensory responses r p h C/inic.ci/ y Nrurophysio/og?, evoked during sleep in man. E / r ( ~ f r ( J r ~ f c r . p h t r / o ~ r rtint1 1966.21. 1-9. Hellbriigge. T. The development of circadian rhythms in infants. Cold Spring Hurhor Symposiu on Q ~ r u n t i t u t i i ~Bai o l o g y , 1960. 25. 3 I 1-323. s. E. H. Attitude and pupil s k e . S(,ietrtiji(,Americ.un, 1965, 212. 46-54. itkin. N . 1.. Mirzoiants. N . S.. Xr Khokhitva. A . Ob orientirovochnykh uslovnykh refleksakh u detei pervogo goda rhirni. (Conditioned orienting responses in children in the hi-st year of life.) Zhitrnul C'wshei Nert,noi D r i c i t c h x r i . 1953. 3. 192-202. (Reprinted in: T h c c.r!itrul n(Jri'0ii.s.sv.\fct71 c i n d brhmi2ior. Translations fi-om the Russian medical literature collected for participants o f the Third Macy Conference on the central nervous system and behavior, Princeton, N.J., Feb. 21-24, 1960. Pp. 343-358. Prepared and distributed by the Russian Scientific Translation Program, National Institute of Health. 1-ibrary of Congress Catalog card number: 5960785.) Keen, K. Effects of auditory stimuli o n sucking behavior in the human neonate. Journal of Expc~rirnc.ntu/ Child Psychology, 1964, 1. 348-354. Krachkovskaia. M. V . Reflex changes in the leukocyte count of newboi-n infants in relation t o f w d intake. PavlovJolrrnul ($Higher N(,rwrr.s A(.riviry, 1959. 9. 193- 199. L h t z . L. M . . Xr Fitzgem . E. Apparatus foi- eyeblink conditioning in infants. Journul of ExpcJrirnPnrulChild h o l o g y . 1966. 4, 276-279.

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Lintz, L. M., Fitzgerald. H . E., & Brackbill. Y. Conditioning the eyeblink response t o sound in infants. Psychononiic Science. 1967. 7, 405-406. Lipsitt, L. P. Learning in the first yeai- of life. In I.. P. Lipsitt & C. C . Spiker (Eds.). Advances in child development und bchuvior. Vol. I . New York: Academic Press. 1963. Pp. 147-194. L.ipsitt, L. P., & Ambrose. J. A . A preliminary report of temporal conditioning to three types of neonatal stimulation. Paper presented at the meeting of the Society for Research in Child Development, N e w York, March 1967. Lipton. E.L.. Steinschneider, A,. & Richmond, J . B. Autonomic function in the neonate. 11: Physiologic effects of motor restraint. Psvchosornutic Medicine. 1960.22, 57-65. Lobban, M. C . Time, light and diurnal rhythms. In 0.G . Edholm & A . L.. Bacharach (Eds.), The physiology ofhumun siirrivul. New York: Academic Press, 1965. Pp. 35 1-386. Lynn, R. Attention. urousal. und thi, orirntufion reuction. New York: Macmillan (Pergamon), 1966. Marquis. D. P. Learning in the neonate: The modification of behavior under three feeding schedules. Journal of Experimentirl P.\vchology, 1941.29. 263-282. Meier, G . W.. & Berger, R. J . Thresholds t o arousing stimulation in the developing infant rhesus monkey. Psychonornic Sciencc, 1967. 7, 247-248. Mirzoiants, N . S. Uslovnyi orientir-ovochnvi reflehs i ego differentsirovka u rebenka. (The conditioned orienting reflex & its ditlerentietion in the child.) Zhurncil Vvsshei Nervnoi Deiatelnvsti, 1954, 4. 6 16-6 19. Morgan, J. J . B., & Morgan, S. S. Infant learning as a developmental index. Jorirnal of Genetic Psychology, 1944,65. 281-289 Parmelee, A. H., Jr. The palmomental retlex in premature infants. Dri*eloprnentcz/ Medicine cindChildNeurology. 1963.5, 3XI-3X7. Pisano. M . . Rosadini. G.. Rossi. G. F.. Kr h t t o n i , J . Relations between threshold of arousal and electroencephalographic p a t t t m \ during sleep in man. Physiology und Behavior, 1966, 1,55-58.

Polikanina. R. I., & Probatova. L. E. Rwvitie orientirovachnoi reaktsii na zvukovoe razdrazhenie u nedonoshennykh detei. (Devclopmcnt of the orienting reaction to sound stimulation in premature children.) Zhrirntrl Vy,\v h e i Nenlnoi Deicitelnosti. 1955, 5 , 227236. (a)

Polikanina. R. I . , & Probatova, L. E. Stanovlenic i razvitie pishchevogo dvigatelnogo uslovnogo refleksa na zvuk ti nedonoshennvkh detei. (The formation and development of the conditioned feeding movement reflex to w i n d in premature children.) Zhurncrl Vysshei Nervnoi Deiuielnosti. 1955.5. 237-245. ( b ) Prechtl, H . F. R., Akiyania. Y.. Zinkin. I’.. & Gr-ant, D. K . Polygraphic studies of the fiillterm newborn: I. Technical aspects and qualitative analysis. In M. Bax & R. C. MacKeith (Eds.), Studies in in/irnc,v. Clinic. in developtnen~ulmedicine. Vol. 27. London: S.l.M.P./Heinemann. 1968. Kechtschaffen, A , , Hauri, P., & Zeitlin. M. Auditory awakening thresholds in REM and N R E M sleep stages. Prrceptiicil untl Motor Skills, 1966, 22, 927-942. Rendle-Short. J. T h e puff test. An attempt to assess the intelligence of young children by use of a conditioned reflex. Archii,es (!f’lIiscersc i n Childhood, I96 I.36. 50-57. Roffwarg. H . P., Muzio, J . N., & Dement. W. C . Ontogenetic development of the human sleep-dream cycle. Science. 1966, 152,604-6 19. Sameroff. A. Nonnutritive sucking in new horns under visual and auditory stimulation. Child Dewlopment, 1967. 38, 443-452. Sokolov. E. N . Perception und the conditioned rqfirx. N e w York: Macmillan (Pergamon), 1963.

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Spears, W. C., & Hohle. R. H. Sensory and perceptual processes in infants. ln Y. Brackbill (Ed.), Infancy and eurly childhood. New York: Free Press, 1967. Pp. 5 I - 124. Stechler, G. Newborn attention BS affected by medication during labor. Science, 1964, 144. 315-3 17. Usoltsev. A. N., & Terekhova. N . T. Functional peculiarities of the skin-temperature analyzer in children during the first six months of life. Pavlov Joirrnal of Higher Nervous A c tivity. 1958,8, 174-184. Weinberger. N . , & Lindsley. D . Behavioral and electroencephalographic arousal to contrasting novel stimulation. Science, 1964, 144, 13.55- 1357. Williams. H . L., Hamrnack. J . T., Daly. R. L., Dement, W. C.. & Lubin, A. Responses to auditory stimulation, sleep loss and the E E G stages of sleep. Electroencephal~graphy and Clinicul Neurophysiology, 1964. 16, 269-279. Wilson, W. P.. & Zung, W. W. K. Attention, discrimination, and arousal during sleep. Archives of Generul Psychiatry, 1966, 15. 523-528. Wolff. P. H. Observations on newborn infants. Psvchosomutic Medicine. 1959, 21, 110-1 IS. Wolff, P. H. The causes. controls, and organization of behavior in the neonate. Psychologicu1 I s s u r ~ 1966, . S ( 17. Whole N o . 1). 1-93.

THE PROBLEM OF IMITATION

Justin A ronfreed UNIVERSITY OF PENNSYLVANIA

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IV. O B S E R V A T I O N A L L E A R N I N G . . . . . . . . . . . . . . . . . . . . . . . . . . . A. C R I T E R I A O F O B S E R V A T I O N A L ILEARNING . . . . . . . . . . . . . . B. O B S E R V A T I O N A L L E A R N I N G IN C H I L D R E N A N D A D U L T S C. O B S E R V A T I O N A L L E A R N I N G IN A N I M A L S . . . . . . . . . , . . . . . D. O B S E R V A T I O N A L CONTROL. OF E S T A B L I S H E D D I SPOS IT1 O N S . . . . . . . . . . . . . . . ....................

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250 V. I M I T A T I O N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. A N A L Y S I S OF S O M E E X P E R I M E N T S W I T H C H I L D R E N . . . . 251 B. T H E L O C U S OF CONTROL. O V E R A T T E N T I O N . . . _ . . . . .. . . 2 5 5

V I . C O N S T R A I N T S O N A T H E O R Y , . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 A. S O M E A L T E R N A T I V E C O N C E P T I O N S OF M E C H A N I S M S . . . 261 B. C O G N l T l V E T E M P L A T E S A N D A F F E C T I V E C O U P L I N G S . . 269 VII. T H R E E E X P E R I M E N T S , , . . , . . . . . . . . . . . . . . . A. S E L F - C R I T I C I S M . . . . . . . , . . . . . . . . . . . . _ . B. S Y M P A T H E T I C B E H A V I O R . . . . . . . . . . . . C . E X P R E S S I V E MOVEMEN-I . . . . . . . . . . . , . REFERENCES . . . . . . . . . . . . . . . .

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I . Introduction Almost forty years ago, C. W. Valentine made the following assessment of our understanding of the variety of phenomena which are commonly taken t o be evidence of children’s imitative dispositions: T h e psychology o f imitation is in u soviewhat chaotic stcite, partly o\t>ing to the ambiguity o f the term cind purtly owing t o disagreement us t o f u c t s (Valentine, 1930-31). It would be no exaggeration to say that his assessment is equally applicable today, even though its extension in time would now include three further distinct and systematic approaches to the definition and study of imitation. Miller and Dollard ( 194 I ) proposed an account of imitation in terms of a behavior-contingent learning process that was based on the paradigms of instrumental training. They demonstrated this form of learning with both animals and children. Piaget ( 193 I ) has used very keen observation of his own children, during their infancy and early childhood. to suggest that imitation belongs in a developmental series of progressions between sensory-motor processes and representational thought. More recently, there have been a number of demonstrations of children’s capacity to reproduce the observed behavior of another person, with varying degrees of correspondence, after relatively brief periods of observation during which they have had no opportunity for overt practice (and, therefore, no opportunity to produce external reinforcing outcomes of their own behavior). The experiments which are described in some detail toward the end of this monograph are attempts to uncover the mechanisms of certain kinds of acquisitions which children may display under these conditions. But the most prolific body of examples can be found in the many cleverly arranged demonstrations which have been reported by Bandura and his coworkers (Bandura, 1962, 1965b). The three approaches which are outlined above have used the concept of imitation to focus, respectively, on very different kinds of phenomena. There are serious questions which can be raised about even the immediate interpretation of their observations and experimental findings. And none of the approaches has yet provided a general theoretical conception of the psychological mechanisms which underlie imitation. Piaget’s treatment of imitation is concerned primarily with the description of developmental changes in the child’s behavioral and cognitive dispositions. It does not give much attention to t h e specific mechanisms of imitation. Almost all other contemporary investigators of children’s behavior have assumed that imitation is a problem in the psychology of learning. Yet there is a widely shared recognition that conventional theories of learning do not provide anything like a satisfactory account of the phenomena of

imitation. It is a commonplace observation that the procedure which Miller and Dollard introduced, as ;i paradigm of imitative learning, was only a form of discriminative training in which critical cues happen to be transmitted to the learner through the behavior of another member of the same species. Their conception of imitation did not e:..;end to the capacity of children to learn the contingencies between acts and outcomes, in some cases quite rapidly, on the basis o f sheer observation of the consequences of another person’s behavior. Nor did their procedure engage the kind of social transmission process in which a child reveals its capacity to imitate with great fidelity the sequence or structure of a fairly complex pattern of observed behavior. A more impressive capacity to learn through observation is often apparent in recent demonstrations of the effects which can be produced in children’s behavior by the opportunity to observe the behavior of others, and also in certain demonstrations of the observational learning of other primates. But the great number of empirical confirmations of children’s ability to reproduce the observed behavior of others has not generated theoretical conceptions which go much beyond the mere inference that the relevant mechanisms of learning do not require the emission and external reinforcement of overt behavior. The ubiquity and strength o f human imitative dispositions led many earlier observers to the conclusion that imitation was an innately programmed phenomenon. In some instances. the nature of the programming was not specified. But imitation was regarded as an attribute or propensity with which people were endowed (Morgan, 1896. pp. 173-1 93; Tarde, 1903).Other observers were onlv slightly more specific in suggesting that children imitated others as ;I result of their instinctive perceptual and motoric propensities (McDougall, 1908, pp. 101-106), or as a result of the interaction of these propcnsities with “circular reflexes” which produced an association between the stimulus of another person’s action and the response of a corresponding action from the child (Baldwin, 1895). Somewhat later, a number of investigators became convinced that the phenomena of imitation could be reduced to simple principles which were derived from more general conceptions of the conditioning or training of discrete overt responses. Some of these investigators emphasized the role of contiguity in establishing an a\soci;itive bond within the circular or reciprocal relationship between the child’s actions and those of another person (F. H. Allport, 1924. pp. 240-24 I ; Holt, 1 93 I , pp. I 12- I 19: Humphrey, 192 I ) . Other investigators apparently viewed imitation as the product of a form of training i n which the child’s behavior was reinforced by rewards or other favorablc outcomes (Guillaume, 1923; Hobhouse, 1915,pp. 184-185; Watson, 1919).

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Thorndike (191 1) believed that imitative learning was reducible to the principles of both exercise and effect, but that an instinctive determinant was also required in order to account for some of the behavior that he had observed in animals. Woodworth (1922, pp. 185-1 91) once proposed that children had innate dispositions to initiate, perceive, and correct their imitative acts, and that any requirements of learning were superimposed on these predispositions. An honest appraisal of the contribution that more recent attempts to formulate the learning process have made to our understanding of imitation does not reveal substantial improvement upon Woodworth’s casual proposition. The extensions of contemporary concepts of learning to the phenomena of imitation are not persuasive contradictions or even amplifications of the flat assumption that children imitate because they are constructed with the inclination to do so. There is in fact much to be said for beginning the study of imitation with an allowance for the possibility that children may have strong unlearned predispositions toward imitative behavior. However, such predispositions may constitute only relatively mild constraints on the broad array of behavioral acquisitions and modifications that can be produced in a child by its exposure to a social environment. Analysis of the phenomena of imitation may therefore disclose some interesting and general features of the learning capacities of a highly complex animal, provided that certain preconceptions about the very nature of the learning process can be freely re-examined. The problem of imitation has a central place in developmental psychology because it bears upon an extremely powerful channel of socialization. The power of imitation has been noted from many different points of view. Freud (1927, 1936) treated imitative behavior as an index of the process of identification-a process which he regarded as crucial to the socialization of the child’s instinctive dispositions, and in which he supposed that the child underwent a major transformation of cognitive and motivational status. The speed and efficiency of observational learning is recognized even in those conceptions of socialization which emphasize the paradigm of behavior-contingent instrumental or operant training (Skinner, 1953, pp. 116-1221. Bandura (1962) has outlined some of the reasons for supposing that the capacities of children would make their observational learning of a complex performance more effective than the kind of learning in which they must first produce the required behavior without the benefit of observation. The rapidity and stability of observational learning also have impressed laboratory and field investigators of primate behavior (DeVore, 1965; Hall, 1963; Harlow, 1959). A number of comparative psychologists have suggested that the deleterious effects of early social deprivation on the later behavior patterns of primates may

be attributable to interference w i t h the formation of social dispositions which are the basis for the transmission of behavioral repertoires by observational learning (Alexander & Harlow, 1965; Harlow & Harlow, 1965; Mason, 1965: Nissen. 1951). And some anthropologists have argued that the imitative tendencies of primates are the key resource of cultural transmission in the evolution o f human society (see, for example, Washburn, 1961). In this introduction to the problem of imitation, a number of liberties have been taken against some important distinctions which are yet to be developed here. I t has become a common practice to use the term imitation rather indiscriminately in reference to virtually any behavioral correspondence that results from a child's opportunity to observe the behavior of another person. This practice is reflected in the frequent use of the concept of a model to designate the observed behavior (or the person who displays the behavior), with little attention to the nature and extent of the correspondence that is produced in the behavior of t h e child. There are actually great differences among the various phenomena which are treated collectively as evidence of imitative modelling. The differences pertain not only to underlying mechanisms, but also to the very question of whether in some cases there is ;my requirement of learning. T h e analysis of these differences may point the way to a more precise conception of imitation-one that is useful in more than a terminological sense. This analysis of the problem of imitation will begin with an attempt to thread apart the various kinds of' conlrol which social observation may exercise over a child's behavior. Our aim will be to distinguish imitation as one form of true observational learning. Children will be the main focus ofthe evidence that is to be analyLed m o s t closely. since our primary concern here is with the role of imitation and observational learning in the socialization of the child. But i t will not be possible to arrive at an integrative theoretical view of the entire range of relevant phenomena without also examining the analogous evidence from the behavior of animals. The capacities of animals are less awesome than those of children and, therefore, permit a longer look at simpler versions of the complexity ofobservational learning in the human case. I t will also occasionally be appropriate to take note of similar evidence from the behavior of human adults. All of the evidence will be used to make some inferences about constraints on a theoretical conception of observational learning and imitation. We will then consider how a tentative outline of such a conception might be phrased in terms of cognitive and affective mechanisms of learning. Finally, the results of some experimental paradigms of socialization will be presented as initial tests of the foi-mulation of these mechanisms.

11. Social Facilitation Many of the observations which are interpreted as evidence of the influence of a model on children’s behavior are more accurately described as the effects of a generalized social facilitation that produces only an indifferent and nonimitative correspondence between observed and elicited behavior. The undifferentiated quality of such effects can be seen very clearly, for example, in experiments which have demonstrated that children’s observation of the aggressive behavior in film cartoons will facilitate their own subsequent aggressiveness in play or in control of the interaction between dolls (Lovaas, 1961; Mussen & Rutherford, 1961). The conditions and findings of these experiments make it obvious that the observed behavior does not serve as a model for the children. On the contrary, the experiments show that the children are induced to engage in relatively indirect expressions of aggression by their observation of other aggressive actions which are always more direct and generally entirely different in their form. Piaget (1951) has suggested that a nonspecific social facilitation of behavior is present in early infancy, and that it is a forerunner of more specifically directed imitative dispositions. I t seems probable that many instances of the social elicitation of infants’ movements or vocalizations are attributable to generalized arousal or motivational effects, rather than to specifically imitative control over the correspondence between the infants’ reactions and the social stimulation that elicits them (Holt, 193 1 : Valentine, 1930-3 1 ; Wolff, 1963). A particular form of stimulation may simply facilitate or release a pattern of behavior for which the infant is strongly primed by its unlearned predispositions. I n general, whatever behavioral correspondence is produced can be quite incidental to the form of the behavior that the child observes, since the social stimulation may elicit the child’s behavior without exercising any control over its form. Many different kinds of stimulation in the behavior of others may be equally effective in eliciting t h e same form of behavior from the child. There is no necessary correspondence between the stimulus properties of the evocative and the elicited behavior. Conversely, certain specific features of the behavior of others may act as social stimuli which simultaneously activate a number of the child’s behavioral dispositions, only one of which incidentally corresponds to the behavior that is the source of stimulation. The findings of a great many experiments with adults also illustrate facilitation of aggression by social observation, without any imitative correspondence between observed and induced behavior (Berkowitz, 1965;

Berkowitz & Geen, 1967; Lxfcourt c t u/., 1966: Walters & Llewellyn Thomas, 1963; Walters, Llewellyn Thomas, & Acker, 1962: Wheeler & Caggiula, 1966; Wheeler & Smith, 1967). As in the case of parallel experiments with children, the observei-’s potential aggressive actions are determined primarily by the modes and targets of aggression which are inherently provided in the situation. I t cannot be inferred that the observed aggression acts as anything more than a generalized motivational or releasing stimulus for the subject’s own aggressive dispositions. T h e experimental conditions often providc cues which indicate the appropriateness or the consequences of the ohserved aggression. But they are not designed to show that the observed aggression itself exercises discriminative control over the form of the indiicvl aggression, since the subject’s options for aggressive behavior are so highly constr‘iined by the situation. I n a number of the experinictits which have been cited. the test for induced aggression does not even permit the subject’s behavior to take the form of the previously observed behavior of another person. I n other cases, the subject is assigned ;I task in which the mode or target ofpotential aggression will necessarily correspond to that of the aggression u hich has been observed. However. the observed aggression also tnight have facilitated virtually any form of aggressive behavior fot- which the situation was structured. For example, in Ihe experiments which are reported by Wheeler- and his co-workers, the siihject has the opportunity to observe verbal aggression toward atwttiei person. and then to expi-css the same general form of aggression toward that person. But the sub-ject’s behavior is assessed only for the frequeiic!, with which it shows verbal aggression. There is no evidence of any cot t.espvndence i n the specific structure O I sequence of behavior. o r even ot‘corr-espondencei n choice miong alternative acts, between t h e obset-vet1and the induced verbalized aggres\ion. A generalized arousal function ot‘obsei.vation, together with the channe!-ling of an observer’s behavior by situational constraints, is likewise suggested by the effects of social l.acilitation on the behavior o f ct-owds (Brown, 1954: LeHon, 1896) or 0 1 1 the individual’s performance of tasks of skill ( F . H. Allpot-t, 1924; D;ishiell. 1935). Much the same point can he macie ahout the interesting experiments which Schachter has devised in order to separate generalized physiological arousal from the cognitive determinants of the quality of affective experience (Schachter-. 1964: Schachter & Singer, 1962). The results of these experiments i n fact demonsrrate that even social facilitation is not always so simple a phenomenon ;is to he entirely attributable to an undiffe re n t i a t ed mot i v a t iona I aro u sa1. A n observet-’ s cog n it i ve rep re se n t a t ion of external information may also 4pecify. to some extent, the general na-

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ture and direction of his behavior. However, the expressions of hostility or euphoria which become evident in the behavior of the subjects of the experiments are only roughly correlated to the observed behavior of their experimentally controlled peers. Whatever degree of behavioral correspondence is present appears to be heavily dependent on situational supports. Similarly, Epstein (1966) recently reported that adult subjects were more likely to give electric shocks to a victim, when they were supervising punishment for errors in learning, if they first had observed another person administer shocks. But the previously cited studies by Waliers and his associates make it clear that the subjects’ use of shock could have been facilitated equally well by their preliminary observation of filmed sequences of totally unrelated forms of aggression (Walters & Llewellyn Thomas, 1963; Walters ct ( I / . , 1962). The observation of the administration of shock might therefore have acted prirnarily as a source ofgeneralized excitation of aggressive dispositions, rather than as a source of discriminative informational control over the subjects’ behavior. Observations of the behavior of animals are especially useful as revelations of the lack of discriminative control that characterizes the release of behavioral repertoires by social facilitation. Many years ago, Shepherd ( 19 I 1) drew the conclusion that numerous examples of actions which were attributed to the imitative capacities of animals were in fact evidence of a more gross and “instinctive” social contagion. Other observers have since noted the importance of distinguishing between the phenomena of social facilitation and those which engage the processes of 1.r.alning . (see, for example, Thorpe’s [ 19631 review of this problem). The facilitative effects of the behavior of one aninial on the corresponding behavior of another animal have been demonstrated in a variety of niamnialian species (Harlow & Yudin. 1933: James, 1960; Scott & McCt-ay, 1967; Simmel, 1962; Weiskrantz & Cowey, 1963). I t has been suggested that even the sheer presence of another member of the same species, without the contribution of overt activity, may be sufficient to facilitate the release or the vigor of an animal’s behavior (Crawford, 1939; Zajonc, 1965). However, there is very little evidence of social facilitation that actually has been obtained under conditions in which the observed activity of another animal can be entirely eliminated as a potential determinant. Most of the studies of animals that are cited above demonstrate the elicitation or enhancement of feeding, which appears to be especially sensitive to social facilitation. The constraints which the animal‘s ethological repertoire places upon the form or topography of the facilitated behavior often make it difficult to discern the grossness of the control that is being exerted by socially transmitted stimulation. This difficulty is very apparent in the behavior of birds, which are highly susceptible to social facilita’

tion. Armstrong (1947) has described the specificity of the effects of social facilitation on the displays of birds. Pre-programmed behavioral specificity also is obvious in extensive observations which have been made on the social facilitation of feeding in birds (Turner, 1964). Altmann ( I 967) and Andrew (1963, 1964) have pointed out that even the highly developed and specific communicative signals of primates may release their corresponding expressions, in another member of the species, under requirements which may be quite tninimal with respect to any learned discriminative control. The generalized motivational properties of social facilitation become highly visible when the elicited behavior is subjected to the requirements of modulation by its outcomes. Under these conditions, one often sees how gross, indiscriminate, and nonadaptive social facilitation can be when an animal must take account of the external consequences of its behavior. Behavior that is released or enhanced by social facilitation frequently seems relatively insensitive to both the ;zffective and informational value of its outcomes. For example. it has long been known that social facilitation will induce chickens to feed. despite apparent satiation of hunger, in the presence of another chicken which I s feeding (Bayer, 1929; Katz & Revesz, 192 1). Hake and Laws ( 1967) recently found that pigeons which had been trained to peck for food would suppress their pecking during a warning stimulus that had been paired with shock, but that their pecking could be released from suppression by the presence of another pigeon which pecked for the food during 1 he warning stimulus. The most compelling evidence ['or lack of discriminative control in social facilitation can be found in situations where facilitation interferes with learning. For example, Klopfei. ( 196 1 ) found that social facilitation of feeding behavior led to a failure of observational discrimination learning in two species of birds. The birds were quite capable of learning the discrimination, which resulted in selective pecking for a palatable food, if they were placed individually in the learning situation. But they could not learn in the presence of a trained performer, apparently because of a highly indiscriminate mutual facilitation of pecking. It seemed that the relatively infrequent errors of the trained peiformer disrupted the learning process in the naive observer. The dominance of social facilitation was so great that the performance of the trained bird actually deteriorated as a result of the indiscriminate pecking of the observer. Skinner (1962) observed a similar phenomenon when he put together two birds which had been individually trained t o high levels of performance in discriminative pecking. Their performances temporarily deteriorated until they later became coordinated to a behavioral criterion of simultaneous performance for the reward of food.

Zajonc ( 1965) has suggested that the generalized motivational effect of social facilitation enhances the performance of a well-established pattern of behavior, but tends to intetfere with the progress of learning. This distinction finds some support in the results of experiments with humans and other primates, which indicate that social facilitation tends to exercise motivational control over established performance rather than informational control over the learning process. For example, Ader and Tatum ( 1963) found that free-operant avoidance training of human adults was likely to be disrupted when a subject had to learn the avoidance contingency in the presence of another subject who also received electric shocks but who could not exercise control over them. More recently, Ganzer ( I 968) showed that female college students were less efficient in the serial learning of nonsense syllables when they were led to believe that they were under the scrutiny of ;I hidden observer. The converse positive effect of social facilitation on an established perfot-mance is apparent in an experiment that was reported by Miller and Murphy ( I 956). These investigators found that monkeys were more accurate in their solutions of discrimination and oddity problems when they were tested in pairs. Their monkeys received substantial amounts of individual training before the tests for social facilitation. and also had frequent intermittent opportunities to consolidate their training while performing alone. I t is surely an oversimplification, however, t o suppose that the releasing or motivational effects of social stimulation always facilitate well-established patterns of behavior and disrupt the learning of new patterns. Social stimulation may sometimes elicit responses which are incompatible with well-established behavioral dispositions. Many years ago, Jones ( 1 924) showed that the fearful behavior of one child sometimes could be reduced, and also that another child who was not afraid might be made more fearful. when both children were placed together in the situation that was initially fear-provoking only for one of them. Similarly, Davitz and Mason (1955) were able to use the absence ofany behavioral evidence of feat- in response to ;I buzzer, among rats which had not been conditioned to an association between buzzer and shock, to facilitate the reduction of established fearful behavior for a paired rat that had been so conditioned. Masserman (1943) obsei-ved, in his studies ofthe feeding behavior of cats, that an acquired suppression which had been established by punishment could be overcome by the presence of a fearless companion that continued to feed. Scott and McCray ( 1967) found that dogs ran significantly faster to a source of food when they were paired, and in close physical proximity, than they did when they ran singly-provided that food was available for both clogs. However. the dogs' well-rehearsed behavior was sharply disrupted when competition was introduced by making food available only to t h e one which reached the source first. Some facilitative ef-

fect of pairing still remained. But the competition significantly slowed the speed of running because it also elicited behavioral repertoires of fighting and avoidance, which were irrelevant to t h e original performance of the dogs. I t is equally true that social facilitation does not always interfere with learning. I n many instances, social stimulation may facilitate the learning process. Etkin ( 1964a, 1964b) has pointed out that “cultural transmission” in various animal species may occur through social facilitation of species-specific patterns of behavior, which can then be attached to new stimulus situations after they have been released. Angermeier, Schaul, and James (1959) trained rats to run at the sound of a buzzer. apparently without the benefit of any additional motivation, by first placing them together with other rats which had learned to run in order to avoid shock. Social facilitation also may be an important determinant of the learning of new contingencies between acts and their outcomes in the environment. For example, a child’s attention to local stimulus features of its environment may be enhanced by its observation of the behavior of another person. This enhancement of attention may facilitate forms of learning which are then relatively independent of any further social transmission of critical information. Thorpe ( 1 963) has emphasized the role of local stimulus enhancement in the transmission of behavior patterns among animals. And Turner (1964) has suggested, o n the basis of his work with birds, that socially mediated localization of attention may be regarded as social facilitation with a specific directional component. T h e directional enhancement of a socially released and pre-programmed pattern of behavior in animals bears an interesting resemblance to the situationally constrained phenomena of social facilitation t t i a t are observed among human subjects in the previously summarized experiments which Schachter, Wheeler, and others have conducted. I t will be seen that social facilitation is a dominant or at least significant component of a number o f phenomena which have been treated as evidence of observational learning or imitation in children. Social facilitation also makes an important independent contribution to a child’s use of the capacity for true observational learning, when it produces orienting or exploratory reactions which focus the child’s attention and cognitive repre sen tat i on on the observed behavior of other s.

I 11. Choice-Matching The matching of a child’s discrete behavioral choices to those of another person, on the basis of learning that is dependent upon external reinforcement of the child’s behavior, presents a marked contrast to the

phenomena of social facilitation. Unlike the generalized motivational or releasing effects of social facilitation, choice-matching requires discriminative control by specific cues in the behavior that has been observed. Miller and Dollard ( 194 1 ) constructed the classic formulation of choice-matching as behavior-contingent training in their conception of “matched-dependent” behavior. They suggested a paradigm in which the imitative act could be viewed as a response that had become attached, more o r less gradually through repeated performance and external reinforcement, to the cues which were transmitted in the behavior of others. The existence of this form of social transmission of behavioral correspondence actually had been noted earlier by investigators who had attempted to study observational learning in animals. For example, Berry ( 1906) concluded that a rat’s learning of a difficult task was facilitated by the opportunity to observe another rat’s performance, but only because the learner was given cues for the locus of rewarded behavior and the immediate opportunity to practice correct movements. Other investigators also noted the usual gradualness of the behavioral changes which appeared in the observational learning of animals (Shepherd, I 9 I 1 : Spence, 1937). and suggested that the animals were merely using social cues for trial-and-error learning without any requirement of imitative use of a model. They were saying essentially that the learning of choicematching could occur without the observer’s capacity for a cognitive representation either of the observed behavior or of t h e contingencies between behavioral alternatives and their outcomes. Miller and Dollard demonstrated that hungry rats could be trained to make correct choices in a T-maze, under the control of food a s a reward, when their only available discriminative cues were transmitted in the concurrent choices of another rat. Essentially the same demonstration has been repeated in other experiments with rats (Church, 1957a, 1957b). Solomon and Coles (1954) found that a rat’s use of the cues from the choices of a “leader,” when it was first learned under the appetitive control of food as a reward, did not then transfer to the choices of another ‘‘leader’’ under the aversive control of shock-avoidance training. Bayroff and Lard ( 1 944) were unable to induce even the acquisition of a choicematching disposition among rats in the aversive learning paradigm of escape from water. However, they did observe the usual choice-matching phenomenon in the appetitive situation. In these demonstrations of the choice-matching of animals through behavior-contingent training, the course of learning typically is quite gradual. Moreover, the behavioral match occurs in the immediate presence of the relevant cues. Perhaps the most distinguishing characteristic of the paradigms is the locking of specific choices to specific external cues -in

contrast to the cognitive representation o f alternative act-outcome contingencies, which is often apparent i n true observational learning. This same characteristic of behavioral inflexibility is discernible in the results of experiments that have imposed a requirement of cooperative integration on performances which two animals already have acquired as individuals, through the device of making :I reinforcing event contingent on the occurrence of both performances within a narrow interval of time. Crawford ( 1 937-38) successfully induced t h o chimpanzees to watch one another’s behavior closely enough that they could produce a concurrent performance of skills which they previously had learned individually in order to obtain food. Ulrich ( 1 967) has shown that rats which are trained individually to escape shock can subsequently be shaped to some coordination of their behavior in pairs, by making the termination of shock contingent on both rats’ performance of the escape response within a short period of time. A very instructive demonstration of this type occurs in the previously cited study by Skinner ( I 963). who trained two pigeons to peck for food simultaneously in a discrimination task, while they were directly adjacent to one another and facing in the same direction. He then reversed their placement in the two trainiiig compartments, and found that they immediately assumed their original left-to-right orientations with respect t o one another. But their orientations now required that they face away from the panel of discriminative \timull, with the result that they continued their coordinated pecking movements in the absence of a target. The consequence of the positional reversal clearly revealed the lack of a representational matching of behavior. There was a stimulus-bound quality in the original learning o f the coordinated pecking. Miller and Dollard also used their behavior-contingent training paradigm to induce choice-matching in children. T h e y dispensed candy as the reward for a child’s correct choice among different boxes to be opened, rings to be pulled, or directions of movement of a lever-. The children were required to choose on each trial, usually from among two alternatives, in accordance with the cues which were given in the immediately preceding choice of another child or an adult. Other investigators have since used various forms of social or material reward to produce similar demonstrations with children (McDavid, I Y59. I Y62; Stein & Wright, 1964; Wilson, 1958). However. the later demonstrations differ from the original paradigm that Miller and Dollard used. In the later studies, the observed choice of the other person does not have a rewarding outcome. Both variants of the paradigm also have becn used to induce adults to match their discrete choices or judgements to t h w e of another person (Kanareff & Lanzetta, 1960; Lanzetta & Kanarefl. 1959; O’Connell, 1965; Kosenbaum & Tucker, 1962; Schein. 1954). In many of the demonstrations with

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adults, reinforcement consists only of information that indicates the correctness of a choice (without explicit reward or social approval). Among the properties which can be used to identify behavior-contingent choice-matching, one of the most common is the grossness of the correspondence that obtains between the behavior of the learner and the behavior of the already trained performer. I t is usually apparent that the observed behavior transmits cues which come to control only the choice of an environmental location at which to act, the selection of an attribute of objects, or the verbalized prediction of an impersonal event. This type of control of an observer’s behavior is quite distinct from the kind of observational learning in which the behavior of another may serve as a representation of the structural or sequential features of the behavior to be acquired by the observer. Miller and Dollard used their choice-matching paradigm to display the arbitrariness that could be introduced into the discriminative control which the observed behavior of another person exercised over the child’s behavior. They trained some of their subjects to make the opposite choice in two-choice problems, and were able to produce either matching or opposite choices with equal facility (in both children and rats). Rosenbaum and Tucker ( 1962) have used adults to demonstrate the same arbitrariness in the direction of the social control of choices in a task. Demonstrations of the use of reward to shape the cooperative behavior of children, under the control of mutually transmitted social cues, are another example of the minimal constraints which behavior-contingent choice-matching may place on the specific form or structure of the child’s behavior (Azrin & Lindsley, 1956; Weingold & Webster. 1964). The same irrelevance of the form of behavior is apparent when cooperative integration is imposed by a reward criterion on the behavior of other primates (Boren, 1966; Mason, 1959). In many studies of the effects of outcomes on the cooperative matching of choices by human adults, subjects actually must rely on cues which are not even directly given in the observable behavior of another person (Deutsch & Krauss, 1960; Kelley er nf., 1962; Sidowski, Wyckoff, & Tabory, 1956). The use of observed behavior as a source of cues which predict the outcomes of choices, rather than as a representational model, is also indicated by the interchangeable and competitive relationships between social and nonsocial cues in choice-matching paradigms. I t is always obvious in these paradigms that the same basic effects could be produced by cues which are transmitted either from observed behavior or from the physical environment. And Barnhart ( I 968) has recently reported an experiment with children that demonstrates this point unequivocally. Church ( 1 957a) found that rats which had learned to use another rat’s behavior as the cue

for their own choices could then transfer their performance to other external cues which had been incidentally discriminative for correct and incorrect choices. Wilson (1958) obtained the same effect with children, and also showed that the incidental cues could then be used alone to facilitate the children’s learning in a second two-choice discrimination problem. In another type of experiment, Church ( 1 957b) showed that environmental cues to which rats had been trained to respond could later be used as incidental cues to facilitate their matching of choices to those of another rat. McDavid ( 1 962) found that children learned readily to match their choices among three alternatives to those of a n adult when a color cue was consistently correlated t o the adiilt’s choices. But the children had more difficulty in learning to match the adult’s choices when the choices varied across color cues. These findings suggest that an important function of social cues in choice-matching paradigms may be to direct the child’s attention to other discriminative cues in its environment. The interaction between social and nonsocial cues may be sharply affected by the child‘s relative orientations or preferences among different stimulus dimensions of the environment. A. THE COGNITIVE

OhlPONI N I

IN

CHOICE-MATCHING

Comparisons among the expctimerits which have used animals, children, and human adults in choice-matching paradigms indicate that the course of learning ordinarily is more rapid in human subjects. The rates of learning are often different enough to suggest that the learning process, in the human case at least, is not entirely dependent on selective reinforcement of the subject’s overt behavioral choices in response to immediate situational cues. There are a number of aspects of the experimental effects which point to the inference that the human subjects are learning more than are the animals during the course of the observation itself-undoubtedly because of their advantage i n the capacity to give a cognitive representation to the contingencies among cues, choices, and the outcomes of choices. Miller and Dollard found that children were easily able to learn to match the choices of another person in only three or four trials, even during their first exposure to ii c hoice-matching paradigm. The paradigms which have been used respectively for humans and animals also make different demands on it subject’s capacity for storage and retrieval of information. H u m m subjects almost always make their choices after the termination of the relevant cues in another person’s choice; whereas the corresponding paradigms for animals typically permit the subject’s behavior to occur in at least partial concurrence with the immediately present cues of another animal’s behavior. Even the para-

digms for human subjects still maintain, however, a close temporal relationship between the occurrence of the social cues and the point at which the subject makes a choice. In general. the arrangement of the contingencies for learning in these paradigms does not permit one t o infer the presence of an observational learning process that goes beyond the immediate control of overt acts by concrete external cues. There are other types of experiments which can be only partially analyzed as behavior-contingent choice-matching to external cues, because their effects also reveal a significant component of true observational learning. In one type of paradigm that has been used with monkeys. the subject makes a discriminative choice after having observed the choice of mother animal (for example. Darby & Kiopelle, 1959. or Kiopelle. 1960). Rewards are provicled for the correct choices of both the first performer and the observer. The initial course of learning is gradual, and it appears that the observer’s choices are being slowly locked by reinforcement to specific external cues in the corresponding choices of the per-former. But the presence of a cognitive representation of alternative act-outcome conti ngen c i e s become s p I-ogressi v e I y more ii p pare n t a s the obse rv e r acq ui re s a discriminative learning set that makes it proficient in the solution of a new problem after only a single observational trial. There have been some very striking recent demonstrations of the power of the dispositions which children niay acquire toward the matching of their actions to those which are displayed by another person (or by a puppet), when the shaping of their behavior through reinforcement by food o r verbal approval establishes a foundation for their use of representational capacities in observational learning (Haer. Peterson. & Sherman. 1967; Baer & Shet-nilan, 1964: Liivaas r t ul., 1966; Metz, 1965). These demonstrations have been conducted with normal, retarded. and autistic children. They do not yield much evidence of the child’s use of a representational model for the imitation of the internal and structural features of observed behavior. But they do produce more than simply a matching of directions of choice. since they build into the child’s behavior a certain amount of fidelity to the general form, and sometimes to the sequence. of the behavior that it has observed-for example, the child is required to touch its toes. to place its hands upon its head. or to pronounce and assemble certain components of words, following the corresponding actions of the adult or the puppet. Whatever fidelity exists in the children’s reproduction of observed behavior in these demonstrations raises the question of how they are able to use observation to attain the criterion of rewarded perforniance. There appears to be a n initial period during which the children use observed

behavior as a source of cues for trial-and-error learning. rather than as a representation of the behavior that they are to perform, since their ability to reproduce the necessary movements or vocalizations at first only gradually approximates the criterion that is inherent in the form of the observed behavior. The minimal I-oleof cognitive representation in the initial learning process is reflected in the technique of external physical guidance of the required actions, which has been used by Metz ( I 965) and by Baer et a / . ( I 967) as a way of helping autistic and retarded children to arrive at the point where they will reproduce the actions spontaneously. This techniqiie of “putting through” was first employed in earlier experiments with animals, in contexts where i t was clear that the subject’s behavior was gradually shaped to the control of cues which were not being used as a representation of the required movements (Konorski, 1948: Thorndike. 1898). However, in all of the recent demonstrations with children, the children‘s final behavioral dispositions show clear evidence of the effects of observational leaiming that is based on their capacity for the representation of actions which will produce reward. After they have had a considerable amount o f triiiniiig on ; I series of tasks, they often match with some speed and accuracy thc action that they observe on the first trial of a new task. R. GFNERAI I/A

1 ION 0 1

( HOIC t

M ArC H I N G

Dl5POsl r l O N S

A powerful source of the ell’ectiveness of socialization may lie in children’s acquisition of a generali7rtl disposition to reproduce the obsei-ved behavior of others. This disposition ma!’ rest on their cumulative exper ence with the external outconic value of the behiivioral products of both their gradually shaped choice-iwitching and their representational learning by observation. I t might apply to any actions which correspond roughly to the actions of others. A generalized disposition to replicate the behavior of others may be responsihle for the effects of extended training on the performance of childrcn who. in the experiments which were described above, begin to reproducc actions as soon a s they have observed them for the first time. The existence of such a disposition seems t v be confirmed by another phenomenon that has been obtained in all o f these same experiments: a small suhsct of hehavioral matchings can be niaintained without any reward. when they occur within the context of ii much larger variety of matchinps which are tieing maintained continuously by repeated rewards. Generalized di\pr)silions toward choice-matching also are implied in the previously cited finding that monkeys become capable of solving discrimination probletns with only one exposure to the outcome

of another monkey‘s choice, after they have had prolonged experience with the reinforcing consequences of using the information that observation makes available (Darby & Riopelle, 1959; Riopelle. 1960). The most extensive work on generalization of choice-matching dispositions was carried out by Miller and Dollard ( I94 I ) . They found that rats which had been trained to use the cues of another rat’s choices in a T maze readily transferred their choices to the cues in the choices of a third rat of a different coat color, regardless of whether they had been trained to make the same or an opposite choice. Their rats also transferred the choice-matching that they had acquired under the motivation of hunger to the cues of another rat’s choices under the motivation of thirst (although Solomon and Coles [ 19541 did not obtain generalization of the choicematching of rats from appetitive to r i v c w i w control). These demonstrations of generalization were quite limited. Miller and Dollard did not obtain reliable generalization effects when they changed environmental cues and the form of the criteria1 behavior, in an experiment in which rats that had been trained to match choices in a T-maze were then placed in a situation where they could match choices of movement from a central position to one of four platforms. Skinner ( 1962) reported some evidence of a generalized disposition toward coordinated behavior between pigeons which were reinforced forjoint pecking, but again without mobility across different forms of behavior. Miller and Dollard obtained more impressive evidence of children’s generalization of the matching and opposition of choices. They first showed that children would generalize their acquired use of another person’s choice cues from a two-choice problem to a four-choice problem. Then they gave other children the opportunity to observe the choices of both an adult and a peer on the alternate trials of a two-choice problem. One group of children was trained to match their choices to those of the adult and to make choices opposite to those of the peer. Another group of children was trained to the reverse of this pattern. Almost all of the children showed complete generalization o n the first trial of a new series in which different adults and peers were used as the sources of choice cues. But they did not generalize well to cues in the behavior of others when they were moved to another two-choice problem in which the required behavior- no longer took t h e same form. However, after some additional training on the second problem, they showed excellent generalization of both matching and opposition, to the respective behavioral cues of an adult and a peer, in a third two-choice problem for which still another form of behavior was required. This last finding was interesting because it indicated that the children were able to acquire, after- only two successive training series, a principle or at least a discriminative set of matching or

opposing the observed choices of another person, which was conditional on the distinction between adult\ and peers. There has been a number of experiments which demonstrate that mere observation of the behavior orjudgements of others will elicit corresponding choices from a child (Hartup, 1964; Hetherington, 1965; Kosenblith, 1961; Rosenhan & White. 1967: Sgan, 1967). Hartup found that children's dispositions to match choices showed some uniformity across a variety of representational figures in doll play. In all of these experiments, the children are not being exposed to paradigms of behavior-contingent training, since their choices are not being modified by any explicit rewards. It seems fairly obvious that the experimental effects are attributable primarily to social elicitation ofali.eady established behavioral or cognitive dispositions which the children carry with them into the experimental situation. The effects are not distinguishable from those which are commonly obtained i n other demonstrations of children's conformity to immediate social influence in the absence of external reinforcingoutcomes (Abelson 8( L e s ~ r I9.59; , Harper ef a / . , 1965; lscoe & Williams, 1963; Jakubczak & W;ilters. 1959). Similar demonstrations have been conducted with adults (Bryan Kr Test. 1967: deCharms & Rosenbaum, 1960; Walters. Bowen. Rr Parke, 1964: Wheeler & Arrowood, 1966). In all of these demonstrations. the observer's behavior is very quickly subordinated to the control of discriminative cues in the behavior of another person. The most relevant analogue for an understanding of their results would be the well-known paradigm of social constraint of an observer's perceptual judgements b y the judgements of others (for example, Asch. 1956). The importance of children's established dispositions toward conformity is nicely illustrated in the results of two recent experiments which have been reported by Hartup a n d ('oates ( I 967) and by Hetherington and Ft-ankie (1967). Both of these experiments provided children with the oppoi-tunity to use the observed expressive behavior of another child or an adult as a topographic moclcl for imitation. Their findings actually included, however. considerably more evidence of the children's conformity to the discrete choices 01. preferences which had been shown in the potential model's behavior. without respect to the structure or form of the behavior. And the children'\ choice-matching was responsive in interesting ways to the prevailing climate of their past experience of interaction with the child or adult whose choices they had observed. Hartup and C'oates allowcd childixn to observe generous acts of sharing o n the part ol'a peer (to\s;ii-d;I third child who was not present). when alternative actions h e r e o b ~ i o ~ i s lavailable, y and then required the observers t o make their own choice\ i n the same situation. Among children

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who were accustomed to a generally high incidence of rewarding interaction with their peers, those who observed a peer with whom they had much positive interaction were more influenced toward generosity than were those who observed a peer with whom they had little positive interaction. But the converse of this effect appeared among children who generally experienced a low frequency of rewarding interaction with their peers. Clearly, the behavior of the children in the former group may have been under the positive control of an expectation of social approval that was based on their extensive past experience with their peers; while the behavior of the latter group may have been under the aversive control of anxiety that was based on their past experience as recipients of social disapproval and rejection. There are similar implications in the findings which Hetherington and Frankie reported. They confronted children with observed discrepancies between the choices which were made, respectively, by their two parents in t h e context of a series of small tasks. The children’s own subsequent choices appeared to be influenced both by t h e warmth and the dominance which were characteristic of each parent’s behavior. I t is difficult to estimate the extent to which any learning occurs in the experimental paradigms which have been summarized here as examples of socially elicited choice-matching without external reinforcement. The observed behavior of others is the source of cues which signal. from the child’s point of view, the appropriateness and perhaps the implicit approval of its potential choices among different objects. judgements, or a s signments of valuable resources. Yet there are no external outcomes which function as contingencies of reinforcement to mark the correctness ofthe child’s choices. Nor is there, over the course of repeated trials, the kind of change that usually is associated with modification of behavior under the control of outcomes. Ordinarily. the extent of the child’s choice-matching disposition becomes apparent very quickly and remains stable. Accordingly. the number of matched choices is usually simply totalled rather than analyzed with respect to its distribution over‘ time. I t is reasonable to suppose that the social information which the child receives during these demonstrations has an affective value that controls the child’s own choices. Moreover, it seems clear t h a t the child cannot bring its behavior so rapidly under the control of a temporary social environment unless it has some cognitive representation of the relationship between its own choices and the choices which it has observed. But it is also clear that the choice-matching may engage learning in only the most trivial sense. Certainly there is no modification of behavior of the kind that can be said to require the child’s use of observed behavior a s a model for its own behavior. The matching of behavioral choices can be attained

without any new acquisition of ;I representation of t h e specific features of the observed behavior or of its discriminate outcomes. Children may be merely told about the preferences of others with much the same effect (Bandura & Mischel, 1965; Ihincker, 1938). A few other experimental findings may be usefully examined here as possible examples of c hildren’s generalized choice-matching dispositions. Bandura and McDonald (1963) identified two groups of children whose verbalized judgements of the magnitude of hypothetical transgressions were primarily oriented, respectively. to either the intention or the consequences of an act, as suggcstd in Piaget’s ( I 948) treatment of inoral judgement. They then prodrrcecl chatiges in the children’s judgements by requiring each child to verb;rlitc it4Jutlgenient of each transgression just after it had heard an adult m i k c ;I judgement that was discrepant from its initially dominant orientatiori. ‘ I hese changes were obtained regardless of whether or not a child received tlireci social approval of those of itsjudgements which conformed to the judgements of the adult. Turiel ( 1966) has reported a similar experiment in which children‘s responses to an extended verbal inquiry first were classified according to the more complex criteria which are employed i n Kohlbei-g’s ( 1970) systematic analysis of moral thought. The children rhen wcre exposed to a n adult‘s verbalized judgements of various acts 01’ conduct, following which they gave their own evaluations of the same conduct. I t was possible to shift the children’s judgements toward pririciplcs crf evaluation of an abstractness and “moral type” which were either an order above or an order below their initially dominant orientatioii.; ( h u t not toward principles which were two orders of complexity beyond their initial orientations). The findings of these experiments indicate that ii child’s evaluative judgements can be moved in the direction of cognitive sinictures which the child only recently has begun either to acquire or to move beyond - in other words, that social observation may havc a tuning effect on cognitive structures which are exerting either a waxing or a waning influence on the child’s judgement. Randura and Harris ( 1966) h;ive shown that children’s relatively infrequent use of the passive sentence construction can be increased by exposing them to the repeated use o f t h e cwnstruction by an adult. in the context of direct social approval of their owii use of the construction. and following instructions which are de5igned l o provide them with a problem-solving set. Exposure to the con\trirction\ of an adult had no facilitative effect on children’s already coninioii use of prepositional phrases, hobever, beyond that induced merel) by ;I combination of direct approval with a probleni-solving set. I n the case of both evaluative jirtlgernents of transgression and sy ntac-

tic constructions, the effects of exposure to the verbalization of an adult would certainly require the child to use some cognitive and verbal representation of what it had heard. But the design of these experiments does not permit the inference that the child has acquired, through imitative or any other kind of representational learning, new evaluative structures for the judgement of transgressions or new grammatical structures for the passive transformation. I t seems more likely that the observed judgements or syntactic constructions of adults elicit from the child its overt expression of cognitive capacities which already have been established, but which have only either a rudimentary or a vestigial status.

IV. Observational Learning A great number of experiments with both human and animal subjects, as well as descriptions of behavior in natural settings, have been reported as evidence of the determinants of true observational learning. Many of these reports do demonstrate that the sheer opportunity to observe the behavior of another person or animal induces some correspondence in the subsequent behavior of the observer. But close examination of the evidence indicates the importance of making distinctions among ;I variety of types of induced control over the observer’s behavior. These different types of control vary in the contingencies which are required to infer their presence, and also in t h e nature of the correspondence between the observed and the induced behavior. Observational learning that requires a cognitive representation of observed behavior constitutes only a restricted portion of the reported evidence. Moreover, in the case of some of the evidence, there is reason to question the existence of any kind of learning. Opportunity for social observation frequently produces effects which appear to follow simply from elicitation of the observer’s well-established behavioral dispositions. Hinde ( 1 953) and Thorpe (1963) have noted that the social transmission of behavioral correspondence in animals can be broken down into a number of different types of paradigms, the effects of which are dependent on both species-specific and learned components of the animal’s behavior. Thorpe distinguishes observational learning, for example, from the social facilitation in which the mere presence or activity of one animal will release another animal’s integrated pattern of behavior, and also from the behavioral correspondence that is induced by social enhancement of an animal’s exploration of local features of its environment. Campbell ( 1963) and Wheeler- ( 1 966) have suggested similar outlines of the variety of paradigms of social influence under which a human

observer may be induced to match behavioral choices to those of another person. Many different kinds of socially transmitted stimulus events have either an inherent or an acquired value for control over a child’s behavior, and therefore enter into a variety of contingencies which make the child’s behavior increasingly similar to that of its agents of socialization. But this increased behavioral similarity does not necessarily require the exact correspondence that can be produced by the imitative use of a model. Nor does it require even that the child learn through the capacity to form a cognitive representation of the contingencies between observed behavior and potential outcomes of the behavior. ‘The behavior of others is a pervasive source of motivation and information for children. It will very often induce correspondence in their behavior because it elicits well-primed and assembled patterns of action, or because it provides discriminative cues for the gradual outcome-controlled shaping of their behavior without cognitive representation. A child will therefore frequently match the observed behavior of another person, in choosing among discrete alternative acts, or in reproducing an established and integrated pattern of behavior, because its past experience in it social environment places it under the discriminative constraints of external cues. The influence of observation on the child’s behavior need not be based, then, on its representational learning of new contingencies hetween acts and their outcomes. Observational learning and imitation often have been used, especially by investigators of animal behavior, as more or less interchangeable designations of what are presumed to be ;I common set of phenomena. There is an important type of observational learning which is imitative in the sense that the behavioral product shows an internal structural fidelity to the form of the observed behavior. But observational learning is also the channel of socialization for vast repertoires of less imitative behavioral skills which children acquire for the engagement and control of their environment. These behavioral i-cpertoires are learned through the child’s capacity to form a durable cognitive representation, during the period of observation, of the general direction or the gross form of the behavior that it has observed. The acquisition of such repertoires requires the child’s representation of the contingencies between its choices of where or how to engage the environment and the outcomes of those choices. And the representation of these contingencies in turn depends on the child’s having had the opportunity to observe the act-outcome contingencies which are produced by the behavior of another person. The outcomes which are crucial to this type of observational learning are not necessarily events that are ordinarily regarded ;is explicit rewards, in the case of either the observed behavior or the child’s subsequent performance. They are the

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more general class of external effects which have a reinforcement value for the behavior o n which they are contingent. Reinforcing outcomes may be inherent, for example, in effects which provide information about the correctness of sequential choices within a task, or in effects which confirm control over other potential events in the environment. A . CRII ERIA

OF

OBSERVAI I O N A L LEARNING

The single characteristic of observational learning that sets it apart categorically from the mere use of social cues in behavior-contingent choicematching is the occurrence of learning through cognitive representation during the period of observation. Evidence of observational learning usually is most apparent in the course of learning, which typically is considerably more rapid and efficient than what might be expected if the same criteria1 behavior were to be induced only by behavior-contingent training. The power of cognitive representation also is reflected in the saltatory changes which sometimes occur in the observational learning process. Finally, observational learning tends to generalize with a considerable independence of concrete situational cues. When the opportunity for observation produces a learned behavioral correspondence only through the observer’s discriniinative use of immediate social cues, the absence or minimal presence of cognitive representation ordinarily will show itself in the gradualness with which the cort-espondence appears. I t is symptomatic of this gradual shaping of matched behavior that the cues which are given through observation do not attain their informational value, during the learning process, until the observer’s own overt behavior produces outcomes which are contingent on the cues. The contrast with observational learning does not imply, however, that the active formation of cognitive representations during observation is the only component of learning in the latter case. On the contrary, the observer’s overt behavioral performances, and his direct experience of their outcomes, can function to test and consolidate the cognitive representations which have been formed during observational learning. Conversely. the shaping of overt behavioral correspondence, without an independent component of learning during observation, does not always obviate the use of the capacity for cognitive representation or result in a laborious learning process. Representational capacities also may facilitate the learning of contingencies which become apparent only in the consequences of the observer’s own overt behavior. In the best demonstrations of true observational learning, i t is quite easy to draw the inference that the learner is not bound to fixed cues in the behavior that he observes or in the external environment, and that he in-

stead employs the capacity f o r ;I cognitive representation of the observed behavior and its contingent oiitconies. The interval of time between the opportunity for observation and the observer's own performance should be sufficiently long that the ohservet- cannot perform correctly through maintenance of a perceptual 01.motoric orientation toward critical environmental stimuli. In the design of many experiments, this criterion is met by not giving t h e learner an opportunity to perform until he has observed either the course of learning 01- ;I long sequence of established performance by another subject. Descriptions of the leatmer's performance, in reports of observational learning by animals as well as by human sub.jects, frequently confirm in other ways that the learner's cognitive representation of contingencies permits ;I free and mobile relationship between his behavior and the social cues which are transmitted during observationfor example, in the adaptive variations o f behavior which the learner may show in taking account of the oiitcomes of both the correct and incorrect choices in an observed performance. B. OBSERVATIONAL 1

I4RNINIr

IN

CHILDREN

AND

At>ut rS

There have been relativel}, few convincing experimental demonstrations of the advantage that ohset-vat ion of another person's behavior can give t o children in disci-iniin;rtion learning and problem-solving tasks. Although some of the choice-m;itcliing tasks which Millet- and Dollard (1941) first used with children may have exploited their subjects' cognitive representations of act-outcome contingencies. their procedur;.- \ were not designed to demonstrate representational learning. Problem-solving tasks have been used by some investigators as a means of structuring paradigms in which the main t'octis of interest is on the child's imitative acquisition of the incidental and expressive topographic features of a model's behavior (for example. in the studies which are reported by Bandura and Huston, 1961, or by M L I S X Iand ~ Parker. 1965). For reasons which we will consider later, there is little evidence of observational leal-ning of task requirements under these conditions. T h e most interesting denionstrations of children's observational learning have been those in which the children can give a cognitive representation to the order- of the c o r t w t alternatives in ;i sequentially pattei-tied task. Poliakova ( 1958) found that young children were able to learn to walk through a maze more efficiently if they first had t h e opportunity to observe the performances of an iidult i n the maze. Rosenbauni ( 1 967) recently has reported a n experiment in which children of elementary school age individually observed the perfor-niance of other children who were learning to negotiate a hanri-m;iLe with a stylus. In a subsequent test of

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recall of the correct pattern, without an actual performance, observers were superior to performers. This finding contains the interesting suggestion that the observer may have had an advantage over the performer in not being bound to the perceptual-motor requirements of overt performance, since the observer would have been able to invest total attention in the formation of a cognitive representation of the sequentially integrated pattern of behavior. Ross (1966) used the behavioral example of an adult agent, together with verbal instruction, to teach the operation of a “post office” to young children. She then required the children to teach the same skills to a peer, and found substantial evidence of task-relevant learning. But there was no control group that would allow the distinct effect of observation to be identified. I n another recent experiment, Rosekrans (1967) has shown that preadolescent boys who are asked to play a game of strategy will reproduce, both spontaneously and in response to instruction, the choices of equipment and tactics which they have seen in a filmed presentation of t h e behavior of a peer. However, there was no criterion of learning inherent in the task that the boys were given, nor any comparison of their performance with that of subjects who had no opportunity for observation. Moreover, their behavior was insensitive to conditions which determined whether they observed the peer’s actions to be followed by social approval, by disapproval, or by no explicit consequences. Adult subjects have also been used in some instructive demonstrations of the observational learning of a sequential performance. Summaries of a number of studies of adults’ observational learning of perceptual-motor tasks can be found in Lumsdaine’s ( I96 1 ) edited compendium. Craig ( I 967) has found that an adult observer of another person’s learning of a complex temporal maze can subsequently learn the same maze more quickly than the original learner. His subjects were able to observe both the information that confirmed the correct choices of the other person and the effects of the electric shock that was administered for incorrect choices. Gurnee ( 1968) has used a paradigm in which two partners learn a maze, under either a collaborative or competitive instructional set, while reversing the roles of observer and performer on alternate trials. Learning was more effective among subjects who were given a collaborative set. in which the observer and the performer were respectively encouraged to offer and seek advice concerning the choices within the maze. This finding suggests that observational learning may be facilitated when the observer’s cognitive representation of act-outcome contingencies can be more actively engaged by the requirement of some degree of control over the observed behavior.

I n a series of experiments that is particularly illustrative ofthe extent to which an observer may enter actively into the task in which another person is engaged, Berger ( 1966) gave subjects the opportunity to observe a confederate who appeared to be learning the manual hand signals of the alphabet for the deaf. T h e subjects had the signal code available and always knew which letter the confederate was learning. T h e findings of this experiment focussed on the subjects’ behavior during the period of observation, rather than on a subsequent criterion of what they had learned. The great majority of subjects displayed numerous overt rehearsals of the motoric representations of letters, regardless of whether or not the confederate engaged in overt practice, and regardless of whether they had been led to believe that they would o r would not subsequently be asked to learn some of the signals. These tindings are quite interesting in a number of respects. For subjects who were told that they would later be required to learn some of the signals, overt practice may have been to some extent an anticipatory preparation of the general skills which they expected to use. However, the display of overt practice during observation by subjects who did not expect to be asked to learn the signals confirms the common observation that people may define their own incentives and performance criteria, in t h e absence of external requirements, when they are confronted with a potentially interesting task. The fact that subjects engaged so heavily in overt reheai-sal of signals, even when they did not observe overt rehearsal on the part of the confederate, makes it clear that their behavior was n o t depenclenl on ;t cognitive representation of the confederate’s behavior. There has also been a number of studies of the effects of observation on children’s simple and discrete motor actions or verbal choices - for example, on the speed with which they move it lever, or on their learning of the choice of words in the construction of sentences (Bruning, 1965: Ditrichs, Simon, & Greene, 1967; Kobasigawa, 1965; Rosenbaum 8i Bruning, 1966). These studies employ pat-dignis in which children have the opport u n i t y to observe the occurrencc. frequency, or magnitude of the rewarding outcomes of another child’s choices or actions. Both candy and verbal approval have been used as positive reinforcers in such experiments. The observed performance of the othcr child may be either “live” or only heard on tape. The effects of observation are then tested in t h e observer’s subsequent learning or performance. I3runing ( 1965) found that the speed with which kindergarten children moved a lever was highly sensitive to shifts in magnitude of reward. rcgnrdless of whether they had directly experienced the previous bascline foi- the shift or had only observed it in the outcomes of another child’s performance. Ditrichs et ul. ( 1967) have

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shown that junior high school children’s observation of social approval of another child’s choices of verbs which express hostility will facilitate the subsequent operant shaping of their own choices of the same class of verbs. Adults have also been used in demonstrations of facilitation of the shaping of verbalization by the opportunity to observe the social approval of another person’s verbal choices (Kanfer & Marston, 1963: Marston, 1966). Lewis and Duncan ( I958) found that observation of the intermittent reward of another person’s choices produced more subsequent resistance to extinction of an adult’s own corresponding performance than did the observation of continuous reward. A very interesting recent demonstration of another kind is reported by Greenwald and Albert (1968). who required college women to watch the discriminative avoidance training of another sub.ject, including the punishment of the subject’s errors, when the women knew that they would later be asked to learn the same discrimination. These investigators found that the subsequent learning of their observers was facilitated in accordance with the extent of the similarity, between the observer’s and the initial performer’s tasks, in the orientation of the apparatus and the use of the left versus the right hand. In almost all of these demonstrations of the effects of observation on the pet-fot-mance of either children or adults, in tasks which require only simple motor or verbal choices. it is fairly clear that observational learning has occurred. The subsequent learning of subjects who are first given the opportunity to observe is shown to be superior to that of other subjects who must learn without the benefit of observation; or observation of the outcomes of another person’s performance is shown to produce modifications of the observer’s behavior- which are comparable t o those produced in the behavior of the perfcmnet-. The conditions undcr which the effects are obtained indicate that the learner has acquired, during the period of observation, a cognitive representation of initially unfx~iiliarcontingencies between acts arid outcomes. The learner observes, over the course of time, the repeated performance of at least two alternative behavioral choices and t h e differential outcomes of those choices. And the opportunity to observe does not merely immediately elicit established patterns of behavior.

There has been active controversy for a long time about t h e presence and extent of the capacity for-observational learning or imitation in a varie t y of species of animals. Different investigators have drawn their conclusions from the study of different types of phenomena in animals which

also vary considerably in their phylogenetic slatus and behavioral repertoire. A brief analysis of the esteiisive hody of work on these phenomena is useful in establishing a bi.oa~lci-coinp~ir-ative perspective f o r the analysis of the influence of soci;il observitrion on the behavior of children. Some earlier reviews of t h e heliavior of animals in experimental parad i g m of observational learning ciiipliastzed that the paradigms provided the opportunity for learning u i t t i o u t i i n y "copying" of another animal's behavior (Crawford & Spence. 1939: Spence. 1937)-particularly through social facilitation of the observing animal's attention to environmental stimuli, which could theti he ~ t s e da s discriminative cues in trialand-er-t-or-learning. 'There i s little que\tion that many purported demonstrations of observational leaming i n animals include uncontt-ollecl c u n ponents of socially facilitated rclt:asc o f the observer's established behavior, or of enhancement of the silience of' cues which the obser\jer can use in learning that is not represerit~rtii,naI with respect t o a prrfoimer'b behavior. Nevertheless, there is suhstanl ial evidence that certain animals. in particular the primates, are cap;iljle o f some forms o f true obsei-vational learning. Many early investigators repor~edevidence of social facilitation or release of the behavior of animal\ in ol,bet.v;itiunal paradigms. and even evidence of learning, without being >atistied that the anirnals displayed an observational o r imitative capacily t h a t could be chxactcrized as "voluntary," "inferential," o r "inlelligent" (Porter', 1910: Shepherd. 19 1 1 ; Thorndike, I9 I I ) . A prohleni 01' ititcrpretation of findings often at-ose because of the gradualness o f the Iearnitig, since repeated test trials might have given the observer the oppot t i i n i t y to learn independently of observation (for example, Haggerry. I900). 'I'horndike (191 1 ) was unable to produce what he regarded as adequate evidence of imitation in a variety of animals, and concluded that ti.i~rl-~incl-errotlearning was sufficient t o account for the phenomena which were being attributed to learning by observation. Watson ( 1908, 19 14) denied the existence of a distinct process of observational learning or imitation in monkeys. despite what appeared to be his own fairly convincing demonstrations of the process. He took the view that nothing beyond the monkeys' direct experience of the reinforcing consequences of their own overt behavior was required to account for such demonstrations. N umerous other investigators have reported failures t o obtain trite nbsei.vational learning in b i d s (Porter, 19101, in rticcoons (Cole, 1907: Davis. 1907: Shepherd, 191 I ) . in dogs (Brogden, 1942). and even in monkeys (Shepherd. I9 10). There does not appear to be ;I clear demonstration o f true observational learning among rats. Berry ( 1906) once attempted such a demonstration. but his findings were essentially those of trial-and-error learning. Berry

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J u rtiri Aronfierd

(1908) was later able to offer a more persuasive case for observational learning of act-outcome contingencies in his demonstration that cats could produce a “general solution” to a problem after having observed the performance of another cat. Haggerty ( 1909) was perhaps the first investigator to claim a positive demonstration of observational learning in monkeys. Some years ago, Fisher and Hinde ( 1949) reported a very rapid and geographically wide contagion of the habit of opening the tops of milk bottles among tits in England, which they interpreted as evidence of imitation among birds. However, as Etkin (1964b) points out. the spread of this behavior is easily accounted for by the socially stimulated release of wellestablished pattet-ns of use of the beak, together with local stimulus enhancement. A great deal of evidence points, not surprisingly, to a relatively powerful capacity for observational learning among primates. The most highly controlled laboratory demonstrations of this capacity have been conducted almost entirely with monkeys (see, for example, the review by Harlow [ 19.591). although Crawford and Spence ( 1939) reported a comparable demonstration with chimpanzees. The descriptive field reports of the Japanese investigators of the behavior of monkeys in natural settings also suggest the occurrence of observational learning i n the transmission of new feeding habits (Imanishi, 1957: Itani. 19.58; Kawamura, 1963; Tsumori, 1967). The fact that the habit of eating candy spreads through a population of monkeys might be the result of little more than social facilitation. However, social facilitation could also make a monkey’s attention to a palatable food, and to the feeding behavior of its peers, the basis for discriminative observational learning of fairly specific actions i n connection with attainment or consumption of food-for- example, as in the washing of sweet potatoes in water, which has been reported by some of the Japanese investigators. The most striking evidence of observational learning among the larger primates has been seen in relatively unstructured situations in the laboratory (KBhler, 1927; Yerkes, 1927. 1934,) and also in the remarkable range of preparation and use of tools that they show in their natural habitat (Goodall. 1965: Hall. 1963: Kortland & Kooij, 1963; Washburn, Jay, & Lancaster, 1965). The description by Hayes and Hayes (1952) of the behavior of a chimpanzee which t h e y raised at home also suggests a considerable capacity for observational learning. A number of reports of observational learning in animals have emphasized the importance of social facilitation as a base for the requirement of attention. I t appears that affective components of the observational situation are crucial determinants of the observer’s attention, and that the opportunity for learning is dependent on the observer’s attachment, orien-

tation, or approach to the performer. For example, Haggerty ( 1909) found that monkeys were not inclined to reproduce observed behavior if the performer’s actions were not rewarded. Yerkes ( 1934) noted that the observational learning of chimpanzees was facilitated when the observer approached the performer, and that it was disrupted by a poor social relationship between observer and petformer. Crawford and Spence ( 1939) obtained poor observational learning among chimpanzees unless the initial performer’s food was given at the location of the correct discriminative stimulus and the observer also received food for the performer’s correct choices. The Japanese field reports on monkeys also suggest an interaction between social facilitation and observational learning. They note that new food habits are most readily transmitted when there is a close relationship between the observer- and the animal that has already acquired the habit (Imanishi, 1957; I t m i , 1958). Hall’s (1963) review of the social transmission of behavior among primates also points to attachment and physical orientation 21s the base for the attentional requirements of observational learning. Formal experiments on observational discrimination learning and problem-solving in monkeys give the most detailed picture of the observational learning process in primates. Kiopelle (1960) and Darby and Riopelle ( 1 959) have shown that observational learning can be made highly efficient when a monkey has repeated opportunities to observe the performance of a peer and then t o engage in its own performance at the same task. I n a typical paradigm, each monkey must choose among two or more locations in order to uncover food. The correct location remains constant between observation and performance. During the initial course of learning, the performance of the observer- appears to be shaped quite gradually. But after a large number of trials, the observer becomes very proficient at solving a problem after a single opportunity to observe another monkey’s performance. Perhaps the most interesting finding is that the observer becomes able to take into account a n error of the performer when it makes its own subsequent choice. This finding would seem to eliminate the possibility that the observer‘s performance could be dependent on an orientation toward any fixed cues or stimulus objects, and to confirm the inference that the observer must be using a cognitive representation of the contingencies between the performer’s acts and their outcomes. Presley and Riopelle ( 1 959) showed that monkeys which had the opportunity to observe the shock-avoidance training of another monkey learned significantly faster than the naive perlormei- when they were then exposed to the same training. However, this last result does not require the inference that the observing monkeys gave ;I cognitive representation to discriminative act-outcome contingencies. I t might have been produced merely by

the effect of focussing the observer’s attention on the light that was used as a signal for avoidance training, or by conditioning of the observer’s empathically elicited anxiety to the light. In another type of demonstration of observational learning, Warden, Fjeld, and Koch ( 1940) showed that monkeys could more readily solve problems which required sequential manipulative behavior when they had first observed the performance of another monkey. They allowed both the observer and the initial performer to engage the problem simultaneously during test trials, even though the observer first had the opportunity to watch the performer for a number of trials. Herbert and Harsh ( 1 944) and Adler ( 1955) demonstrated observational facilitation of the learning of cats in a somewhat simpler kind of manipulative problem-solving. Herbert and Harsh reported the interesting finding that observational learning was more effective when the cats had the opportunity to observe learning rather than a skilled performance, and also that the advantage of observing the learning process was even greater when the performer frequently used the manipiilanda incorrectly. These findings are analogous to Riopelle‘s ( 1960) finding that a well-trained monkey’s performance on a discrimination problem was more accurate when it first observed another monkey’s error than when it observed a correct choice. The findings suggest that the opportunity to observe another animal’s errors gives the observer more discriminative cognitive representations of alternative behavioral directions and their potential environmental effects. Warden, Jenkins, and Warner ( I 936) once asserted that imitation or true observational learning did not exist other than in primates. Warden and his co-workers employed criteria which tended to emphasize the representational learning o f act-outcome contingencies in a situation where there were two or more relevant ways to engage the environment (Warden & Jackson, 1935). I t is interesting to consider, in the light of these criteria, the demonstrations of manipulative observational learning in cats (Adler, 1955: Herbert & Harsh, 1944). These demonstrations appear to require more correspondence of the specific form of behavior, between the observer- and the initial performer. than do the demonstrations of the observational learning of monkeys i n discrimination paradigms (Darby & Kiopelle, 1959: Riopelle, 1960). Close analysis of the behavioral effects which were obtained with cats reveals, however, that there was only one way in which the cats could engage the environment in the direction of interesting and salient objects. They were exposed to an apparatus and setting which necessarily produced a certain amount of specific correspondence of behavior between observer and performer, assuming that the observer was going to learn anything-for example, they were required t o pull a little food cart by its attached ribbon. The

same absence of a requiremenr ot’discriniination, between contingencies which govern the outcomes of two or more active behavioral alternatives, can be seen in the recent experimental demonstrations by John ct cil. (1968) of cats’ observational learning o f hurdling to avoid shock or leverpressing to obtain food. The constraint on the single direction of the cats’ engagement of the environment is also suggested in the fact that the largest learning efiect occurred on the early trials, i n cotrlt-ast t o the gradualness of the initial effect in observational discrimination learning by monkeys. Adler’s ( I 955) finding that the observational learning of cats under this constraint was not disrupted by change i n the location of the manipulanda, between observation and test, indicated that the cats were capable of learning behavioral directions with respect to ob.jects and outcomes, rather than only with respect to a fixed location in space. Hut such a performance might require only more or less direct or iconic representation of observed behavior; whereas the monkeys‘ Icarning of discriminative contingencies between alternative acts and dilt’erential outcomes. with less environniental constraint on the direction of hehavior. would require something closer to the kinds of cognitive represetitations which are implied in conditional rules or operators. Observational learning by uninials provides little or no evidence of fidelity to the topography or structural features of observed behavior. Even in those cases in which thc animal appears to learn manipulative o r sequential behavior. the behavior is limited to fairly simple operations upon the environment, such as t~rrninga knob or pushing a pedal. These actions do not require that the ;inimal give a structural representation to the topographic components of an extended pattern of observed behavior. I n the demonstrations of observational discrimination learning by monkeys, there is only an incidental correspondence between the forms of the observed and the produced behavior. The accuracy and speed of the general direction of the monkey’s behaviol-. in its approach to the location at which it can make a correct choice, is the primary criterion for identification of correct performance. The specific form of the monkey’s behavior is irrelevant. Although the initial performer will ordinarily use its hand to uncover food, the observer’s subsequent use of its hand can be more plausibly attributed to its manipulative dispositions than to any imitative use of a model. I n an interesting experiment. which Harlow ( I 944) reported some years ago, monkeys were able to learn it discrimination by observing the cue that the experimenter proviclcd in tapping the correct stiniulus-location, even though their opportunity to make a choice was delayed. This paradigm was essentially the same ;IS that used by Hunter (1913) in his

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experiments on the delayed reaction in children and animals. Hunter’s work showed that children were able t o bridge longer delay intervals than were animals. The children appeared to be much less dependent on a bodily orientation or motor set toward the location of a reward, and obviously had a greater capacity for cognitive representation of the location. I t can be seen that the paradigm which was used in these experiments was very close to the paradigm of observational learning. But successful performance clearly did not require a reproduction of the f o r m of the observed behavior of another person or animal. I t is interesting to note that many experimenters who have obtained what they considered to be evidence of observational learning or imitation in animals also have pointed out that the phenomenon occurred only when the relevant behavior was natural or familiar to the animals (Berry, 1908: Kohler, 1927; Yerkes, 1927). Herbert and Harsh ( 1944) noted that observational learning in cats occurred most easily when almost any form of behavior was sufficient once the observer had arrived at the correct location in the environment. There does not seem to be any experimental evidence of an animal’s imitative fidelity to the specific features of the behavior of a model. Nevertheless, certain forerunners of imitative learning may be present in the higher primates. The report by Hayes and Hayes ( 1 952) of the behavior of their home-reared chimpanzee suggests the possibility of imitative use of a model-for example, in the chimpanzee’s puckering of its mouth when it appeared to be applying lipstick.

I n another type of study, of which there have been many recent examples, an important component of the effect of observation may reside in elicitation or suppression of the child‘s behavior by its opportunity to observe the explicitly rewarding or punishing consequences of another person’s behavior. Most commonly, these studies focus on classes of behavior for which the child has fairly well-established constraints on the basis of its past social experience-for example, on acts of aggression or on the choice of whether to play with a forbidden toy. The paradigms typically are designed to expose the child to ii single observation of the rewarding or punishing reactions of an agent of socialization to the behavior of another child or an adult. The child is then placed in a situation where it may engage in the same behavior. I n most cases, only one test for the effect of observation is made, immediately following the child’s opportunity to observe. In some of the demonstrations of the effects of observation on children’s aggressive behavior, the child observes a series of differentiated

actions which, quite independent of their consequences, might lend themselves to imitation in a sense that we will consider later. We are primarily concerned at this point, however, with the mechanisms for the much simpler effects which are implied i n the respectively facilitative and suppressive influences of observed reward and punishment. I n the majority of the relevant demonstrations, the behavioral product of these effects is a gross choice, on the part of the child. of whether or not to commit a discrete action. T h e effects which are obtained seem to be quite distinct from those which meet t h e criteria that were described earlier for the observational learning of contingencies between acts and outcomes. The child does not have t h e opportunity to observe the diffk~rrtititrloutcomes of another person's rrltc~matir~e behavioral choices. N o r is there any evidence to indicate that the child forms, over the c ~ u r s of e time during the observation, a discriminative representation of contingencies with which it was previously unfamiliar. Bandura ( 1 965b) has suggested that the facilitative or suppressive effects of observing the consequences of another person's behavior may be classified as phenomena which t ~ v e a l"no-trial" learning. They might equally well be described. however. a s phenomena which reveal no learning at all. The evidence makes i t clear that sheer observation of another person's behavior. irrespective of whether or not the behavior has r-ewarding consequences, may act to release well-established corresponding behavioral dispositions in the child. ('hildren who have seen the aggressive behavior of an adult rewarcled show a greater incidence of similar aggression in their own subsequent behavior than do children who have seen the adult's behavior punished (Bandura, Ross, & Ross, 1 9 6 3 ~Rose; krans & Hartup, 1967). Likewise. children who have observed socially rewarding consequences of another child's violation of a prohibition are more likely to commit the same violation than are children who have observed punishing consequences (Walters, Leat, & Mezei, 1963). However, the results of other experiments show that there is only a significant suppressive effect of the observed punishment. Children who observe behavior that is followed by no explicit consequences engage in the same behavior almost as readily as clo children who have observed rewarding consequences of the behavior (Bandura, 1965a; Walters & Parke, 1964; Walters. Parke, & Cane. 196.5). The large component of social facilitation in the mere observation of another person's behavior is confirmed by the fact that children who do not first observe any aggressive behavior, in the control gt-oups of some of the experiments which have been cited, subsequently display only a negligible amount of aggression of their own. Stein ( 1 9 h 7 ) has found that children who merely see another child commit a prohibited act are more likely to commit

the same act than are children who do not observe a violation. Similar and equally obvious effects have been reported in studies of the social conformity of adults (Kimbrell & Blake, 1958; Lefkowitz, Blake, & Mouton, 1955). In general, it appears that these findings reflect the difficulty of bringing a child’s behavior under the control of observed or anticipated external rewards when the behavior itself has inherently reinforcing consequences -for example, when the situation provides an attractive target for aggression. There is some evidence that behavior which has less support from its inherent consequences, such as sharing or the application of high criteria in rewarding one’s own performance, shows more facilitation by the child’s observation of social reward of another person’s corresponding behavior (Bandura, Grusec, & Menlove, 1967b; Doland & Adelberg, 1967). There is much firmer ground for the expectation that observation of the punishment of another person’s behavior will have a distinct suppressive effect on children’s subsequent corresponding behavior. Children who have observed punishment of a n adult’s aggressive behavior (Bandura, 1965a), or of another child’s violation of a prohibition (Walters & Parke, 1964; Walters et al., 1965), are substantially less prone to engage in the same behavior than are children who have observed only the behavior followed by no consequences. Similar findings are described in reports of the effect of observed punishment on the aggressive dispositions of adults (Lefcourt rr al., 1966: Wheeler & Smith, 1967). Although all of the evidence shows that the observation of punishment has an independent suppressive effect on the child’s behavior, it does not necewirily demonstrate that the effect of suppression is specific to the contingency between the observed actions and the punishment. It is quite possible that the observation of another person’s punishment might have a generalized suppressive effect on all of the child’s subsequent behavior,and not a selective effect on the behavior that has been observed to produce punishment. Unfortunately, none of the demonstrations is designed so as to permit separation of the potentially generalized and specific suppressive effects of observation of the punitive treatment of another person’s behavior. It is unlikely that the experimental effects which have been summarized can be attributed entirely to t h e kind of generalized motivational or affective arousal that would produce indiscriminate elicitation or suppression of the child’s behavior. The effects are specific in their direction to the aversive outcomes, and occasionally to the positive outcomes, which are observed in the consequences of another person’s behavior. I t seems very probable that this specificity rests on the child’s cognitive representation of the critical contingency between the observed behavior and its outcome. T h e findings suggest that the child’s performance or suppression of

the behavior that it initially observes is controlled by the affective value of the information that is transmitted during observation. But this observational control of the child’s behavior cannot easily be treated as evidence of learning without a drastic expansion of the conception of observational learning and a corresponding reduction in its utility. The control that observation exercises over the child’s behavior in these demonstrations appears to operate through a temporary attachment of change in affectivity to the child‘s cognitive representation of actions for which it has wellestablished behavioral dispositions. There is no reason to suppose that the child acquires new behavioral dispositions, or that it engages in any learning which would introduce changes into the discriminative control that familiar external cues exercise over the overt expression of its established dispositions, The control of children‘s behavior by the affective value of information about potential outcomes is a commonplace phenomenon in naturalistic settings, particularly in certain areas of social behavior where children experience great variability i n the I-ewarding or punishing consequences of their actions. Children often must integrate all of the available information that signals the probability of social approval or disapproval of their behavioral alternatives. What seems to be demonstrated in the experimental settings is that the child’s integrative estimate of the potential outcomes of its behavior, in a concrete situation that strongly invites particular actions, is highly sensitive to its observation of the rewarding or punitive consequences of anorher individual’s actions. There is no doubt that children have the cognitive capacity with which to translate these observed consequences into control o f their own behavior. The speed with which the observed reward or punishment transmits its affective value to control of the child’s behLivior suggests that the transmission process may be analogous to a rapid Corm of conditioning of affectivity to the child’s cognitive representation o f t he observed behavior. I t should also be noted that demonstrations of observational facilitation and suppression of children’s behavior characteristically do not show that observed rewards and punishments are significant determinants of the children’s representational use of the specific form or structure of the observed behavior. When the observation of punishment of another- person’s behavior, for example, induces suppression of the child’s corresponding behavior. what the child has in fact observed is the commitment rather than the suppression of thc behavior in question. In a few of the experiments which have examined the influence of observed rewards and punishments on children’s aggi-essive behavior, the evidence indicates that the consequences of the observed behavior exercise control over the child’s subsequent performance o f similar behavior, but not over its ac-

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quisition or retention of a cognitive representation of the specific features of the observed behavior (see, for example, Bandura rt al., 1 9 6 3 ~ )I. n almost all other demonstrations of this type, the effects of observation of the outcomes of another person’s behavior are limited to a general direction or choice in the child’s subsequent behavior. Despite its prevalent use (cf. Bandura & Walters, 1963), there does not seem to be an interesting sense in which the concept of a model can be useful to an account of such effects. Two experiments which recently have been reported by Bandura and his co-workers (Bandura, Grusec, & Menlove, 1967a; Bandura & Menlove, 1968) are perhaps the most interesting and well-designed examples of the effects of social facilitation on changes in the relative strengths of children’s behavioral dispositions. These investigators have shown that children who have a strong fear of dogs can be induced to engage in a series of increasingly intimate interactions with dogs, after they have first repeatedly observed the same interactions on the part of one or more fearless peers. The effects of observation are tested in the absence of the peers. These demonstrations are particularly persuasive because they assess behavioral change from a pre-observational base, and also because the effects are apparent some weeks after as well as immediately after the period of observation. Children who do not have the opportunity to observe a peer’s fearless interactions with dogs do not show the same modifications of behavior. Although it may be argued that the results of these experiments hinge on the fearful child’s opportunity to observe the absence of aversive outcomes of a fearless peer’s behavior, the conditions make it difficult to infer that the fearful child’s subsequent contacts with dogs are the product of observational learning of act-outcome contingencies. The observed behavior of fearless peers in itself may elicit some of the pleasurable affect that even the fearful child may have experienced in previous contacts with other animals. Or it may elicit other dispositions which are incompatible with the original avoidance reactions of the fearful child. It may also be noted that the behavioral effects do not require any representational fidelity between the observed and the subsequently performed actions. The originally fearful children usually later engage in some sequential interactions with the dog. And these interactions are roughly the same as those which the children have observed in the behavior of the fearless peer. But each of the sequential actions is separately specified for the children by direct instruction. Moreover, their performance corresponds only in a very general way to the observed actions of the fearless peer. It has become a common practice to invoke the presence of empathic or vicarious experience in order to account for the facilitative and suppres-

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sive behavioral effects of observed rewards and punishments, and also to account for observational learning in which the learner actually does appear to acquire new cognitive representations of discriminative contingencies between acts and their outcomes (Bandura, 1965b; Kanfer, 1965). This practice rests on the assumption that empathic or vicarious mediation is demonstrated when the observed outcomes of another person’s behavior have no immediate consequences for the observer, but do exercise some control over the observer’s subsequent behavior. However, although the determinants of this class of phenomena may sometimes include an empathic or vicarious component, it is not necessary to assume such a component. The terms empathic and vicarious have their greatest utility when their application is confined by criteria which are fairly close to the connotations of ordinary usage- that is, when an observer’s affective experience corresponds in certain respects to the perceived experience of another person. The author has presented elsewhere a more detailed analysis of the nature of empathic and vicarious experience (Aronfreed, 1968a, Ch. 4). The crucial ingredient is the observer’s responsiveness to social cues which convey something about [he direction and quality of another person’s affective experience. This ingredient cannot be inferred from the conditions of experiments which have shown only that a child’s learning or performance is influenced by observation of the outcomes of another person’s actions. These experiments generally do not provide the child with cues which would transmit information about the affective experience of the person who is exposed to the outcomes. It is more parsimonious to suppose that the results of the experiments are determined by the information that is carried simply in the positive or aversive contingencies which have been observed. This information will have an affective value of its own for the child, which may be entirely independent of the value of any information about another person‘s affective response to the contingencies. Even if explicit cues of the other person’s affective experience were observable to the child, it would still be difficult to infer the presence of empathic or vicarious experience without an overt behavioral index of the value of the cues during the period of observation. If these social cues were made the contingent outcomes of the child’s own overt performance of an act, however, so that their potential reinforcement value could be examined, then their function as elicitors of empathic or vicarious experience might be demonstrated more convincingly. Another group of demonstrations of children’s cognitive capacity for the representation of socially transmitted information can be found in a series of experiments in which the observed actions of adults or peers are used to influence a child’s performance criteria for the distribution of re-

wards to itself (Bandura & Kupers, 1964; Bandurd & Whalen, 1966; Mischel & Liebert, 1966). These experiments use paradigms in which the child observes another person’s variable quality of performance at a bowling game. At the close of each of the observed peiformance trials, the other person chooses whether or not to take some candies or other tokens of reward from a readily available supply. The criteria which are used in this choice are made explicit for the child, since they are distinctly verbalized by the other person on each trial, with particular reference to the deserving or undeserving quality of the performance. Some children observe a consistently high performance criterion for the self-controlled reward. while others observe a low criterion. When the child then plays the game and is likewise permitted to control its own rewards, immediately following the period of observation. its behavior is substantially influenced by the performance criteria which it has observed. For example, a child who has observed another person‘s use of a high criterion tends to limit its own self-controlled rewards by adhering to the same criterion, even though its choices are not under any direct external constraint. Marston (1965) has described comparable results from a similar experiment with adults. Children‘s adoption of observed performance-reward criteria under the conditions of these experiments does not require the inference that they have acquired new behavioral or cognitive dispositions on the basis of observational learning. The information that observation provides about values which are appropriate to the situation may be sufficient to generate the experimental effects, quite independently of any learning from observation of another person’s behavior. A number of studies have shown that observation of the self-rewarding behavior of others is no more effective in gaining control over the child’s subsequent performance criteria for selfreward than is an initial exposure to a direct training paradigm in which the criteria for reward are first externally imposed on the child’s own performance at the game (Bandura & Whalen, 1966: Liebert & Ora, 1968; Mischel & Liebert, 1966, 1967). In the direct training paradigms, the experimental agent’s verbalizations of the criteria are essentially the same as those which are uttered by the self-rewarding performer in the observational paradigms. I t is clear that these verbalizations are crucial to the effects in both types of paradigms. and that t h e y tune the child’s already established cognitive structures for the evaluation of contingencies between performances and rewards. Bee and Colle ( 1967) found that children did not adopt the performance criterion that they had observed another person to use under conditions in which verbalization of the criterion failed to include assertions that the performance at bowling deserved or did not deserve reward. The total pattern of evidence from these experiments indicates that

verbalization and other sout-ces ofirif~~i.riiation, during the period of observation, act to elicit alternative options from within the child’s established evaluative dispositions toward the control of reward by criteria1 performances. Bandura and Perloff ( 1907) have shown that many children will privately maintain very high pet-forinance criteria for self-reward even when they have not first been exposed to the influence of either observation or direct training. Other evidence confirms that the influence of observation on the child’s subsequent self-reward is very much determined by immediate situational cues. McMains and Liebert (1968) found that children adhered to the last ctitcrion that they had obser-ved when they were exposed in quick succession to the inconsistent self-imposed criteria of two different people. Bantlur:i ct t i / . ( I967b) found that observed social approval of an adult’s use of ;I high performance criterion facilitated children’s subsequent adoption of the same criterion in rewarding themselves. I n contrast, conditions which would seem to have transmitted information that was discrepant with thc application of high criteria -for example, the simultaneous use of ;t lower criterion by a peer, or the display of nurturance toward the subject by the adult-interfered with the children’s adoption of the adult’s criterion. I n all of these demonstrations of social influence on children’s perfot-mance criteria in the allocation of their own rewards, there is virtually no evidence of their representalional use of the behavioral features of a model. The demonstrations are not designed to show that the specific form of the children’s behavior i n the performance of the game itself, or in the distribution of rewards t o themselves. is in any way patterned after the behavior that they have observed (although Bandura and Kupei-s [ 19641 did report that some children spontaneously made self-evaluative coniments which were similar to those of the previous performer). Of course, the children’s own evaluativeJudgments of when to reward their performances could not have been influenced b y their observation of the contingencies which governed another person’s control of reward unless they had been able to give a cognitive representation to these contingencies. But the experimental effects did not require them to give discriminative attention to either directional or internal features of the other person‘s behavior. It is interesting to note the finding by Liebert and Ora ( 1968) that children, in dispensing rewards t o themselves for their own performances, more often violated the previously observed performance criterion of another person when their- auhcritet-ial performances were relalively high than they did when their pct-i’orniances were low (even though they had never observed such a loosening of the criterion). Apparently, they were using their own evaluative dispositions to extend the range of application of the information that they had received in the observed criterion. Observational control of chilclren‘s behavioral or evaluative disposi-

tions is also illustrated b y the findings of other experiments in which children :ire given information about socially approved or desirable choices. Bnndura and Mischel ( 1965) were able to influence children’s expressed preferences for immediate versus delayed rewards by exposing them to observation of an adult whose verbalizations of the relative predictability and value of such I-ewat-dswere discrepant with their own initial preferences. There is in this finding no evidence of t h e representational learning of behavioral structure or of discriminative contingencies. Nor is there such evidence in the results of experiments in which children or adults are shown to be more likely to extend aid or help when they themselves previouslv have experienced distressful or dependent roles in similar situations (Berkowitz & Daniels, 1964; Berkowitz & Friedman. 1967; Goranson & Herkowitz. 1966: Lenrow, 1965).The experimental effects take the form o f a gross correspondence of direction or intent between the subject’s choices and the behavior that the subject has observed as a recipient of help or relief of distress.

V. Imitation We have noted that observational control of children‘s learning, and also of their established behavioral or evaluative dispositions, characteristically produces only a gross correspondence to example when the effect of observation is determined by external outcomes of the observed behavior of another person. Observational learning that is controlled by the child’s anticipation of rewards, of punishments, or of other kinds of external reinforcing or informational effects. seems to require cognitive capacities which are representational only with respect to the general form of behavior or to the direction in which it should engage the environment. These capacities may be quite powerful, with o r without a symbolic component, when they must represent alternative act-outcome contingencies or patterned sequences o f choice which ;ire under- the control of complex disc rim i na t i v e cue s . B 11t out come -con t 1-0 I I e d obse rv a t io na 1 learn i ng does not ordinarily reveal the child’s cognitive representation of the specific form or detailed topography of the observed behavior. In contrast to observational learning that is controlled by the outcomes of observed behavior, there is another kind of observational learning that is relatively independent of the outcomes of both the behavior which the child has observed and the child’s own reproduction of the behavior. I n this latter type of observational learning, there appears to be an intrinsic value for the child in the behavior that it reproduces. ‘The learning is imita-

tive in the sense that the child uses the internal structural features o f o b served behavior as a model for the topography of its own behavior. Iniitative reproduction of behavior is ;t pervasive phenomenon in the socialization of the child. I t is apparent in the behavioral aspects of the identity that the child acquires i n various social roles, in the expressive or stylistic elements of its skills at many manual and intellectual tasks, and in numerous other areas of its intet.action with a social environment. A . ANAI Y S l S OF

SOMI

E x P t K I M E N I S WITH C H I L D R E N

There are a number of types of experiments which might be regarded, at least in part, as demonstrations o f childi-en’s imitative representational use of a model. I t is often tlitlicult to evaluate, however. the extent t o which the observed correspondence hetween a child and its potential model can be attributed to imitative learning. Most of the experiments provide children with the opportunity to observe and reproduce the sequential structural compont‘rils of another person’s behavior. And the behavior that the children di5pl;iy i n some of the experiments seems to have an intrinsic expressive viil~icthat is independent of reinforcing extet-nal consequences. Yet the dcxriptions and analyses of the children’s behavior frequently leave much uncertainty about both its innovatiie features and its topographic fidelit! to ;I model. The analyses o f the findings of’ thcse experiments do not give sutticient attention to the fidelity and rcbl;itive frequencies of the discrete coniponents of behavioral evidence of inlitiition. Components that are quite different in their representatioiial requirements are cl. ified together in ;i common index of the experimt‘ntiil elt:cts. thus obscuring the distinction between those which may hc elicited from the child’s established r e p ” - toire and those which may hc ;icqiiii.ed by imitation. .The absence o f clarity in this distinction is fairly sei-ious. since evidence of imitittive learning generally is n o t assessed from ;I I~i-e-ohserv~itioti~il baseline. I t is xisuined, quite reasonably, that learning w i l l he obvious when the child i-cproduces behavior that is novel with t-espect to m,hat one might expect to find i n it5 repertoire. And in the case of‘ i n o h t o f the experiments, i t is in fact clewithat the children would not spontant‘ously have emitted much o f the behavior that they show, if they had nut first had the opportunity to observe the corresponding behavior of another person. But this effect of observation in itself can hardly suppor-r the i nference that imitative learning has occurred. I n the experiments which have focussed on observational control of chi Id re n ‘s aggression , the ;i 11:I Ib, xe s e 111p h a s ize the co ni pari son bet wee t i

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those children who have observed the corresponding aggressive behavior of another person and those who have not. The difference that emerges, however, is essentially quantitative rather than qualitative. I t is not claimed (nor does the evidence show) that none of the same basic forms of aggression will appear spontaneously in the behavior of the children who have not been given the opportunity to observe these forms. Some minimal spontaneous evidence of the same modes of aggression actually would seem to be inevitable, in view of the fact that the potential target of aggression is a large inflated plastic doll which is perfectly tailored to invite the most common forms of physical aggression from children. Even in other types of experiments in which children may be unlikely to show any spontaneous evidence of a particular form of behavior, when they have not first observed another person’s similar behavior in the same situation, the effect that observation will produce can be entirely attributable to motivational or informational sources of a generalized social facilitation or of a more discriminate elicitation of specific behavioral dispositions which are already established. The crucial question of interpretation always remains, then, the one of whether the children have acquired new behavioral dispositions on the basis of their representations of an external model. Perhaps the most difficult experiments to interpret are those which Handui-a and others have devised in order to demonstrate that children’s aggressive dispositions are influenced by their preceding observation of another person’s aggressive behavior (Bandura, 1065a; Bandur-a. Ross, & Ross. 196 I , I963a, 1 9 6 3 ~Hicks, ; 1965: K u h n , Madsen, & Becker, 1967; Korekrans & Hartup, 1967). The setting for the children’s aggression in these experiments typically is dominated by the ubiquitous inflated “Bobo” doll. And the observed aggressive behavior is almost always dis{played by an adult. There are substantial similarities between observed and induced aggressive behavior in the findings of these experiments -for example, in punching, kicking, o r sitting on t h e doll. These similarities could indicate that a model’s expressive modes of aggression had acquired some new and intrinsic value for the children. But the evidence is uncertain because the child observes and performs familiar aggressive acts which would appear to afford it a great deal of pleasure in their inherent external consequences. The pleasurable vigor and the situational appropriateness of the potential aggression would be obvious to the childnot only in the very behavior that it has observed, but also in the presence of highly attractive instruments and targets which are specifically designed to produce maximally interesting effects of physical aggression. The situation is clearly one of play rather than of anger or destructiveness. Kuhn rt al. ( 1967) found that frustration tended t o suppress rather

than to enhance the effect of observation on children’s aggression toward the doll. The findings of these last investigators have the advantage of being the only ones which are based on a pre-observational assessment of the children’s initial aggressive dispositions. The physical forms of aggression which are reproduced by children in these experiments are prepotent in their repertoires to an extent that often makes it seem unlikely that their performance would require any significant amount of learning through the representational use of a model. Punching and kicking, for example. can hardly be regarded as novel forms of behavior for children. And the usual suppressive controls o n such behavior can easily be released by social cues which indicate that it has become permissible. More evidence of learning would be apparent if the children reproduced aggressive actions which were more foreign to their repertoires, o r if the inflated doll were less salient as the object of aggression that dominates the play environment. Although the experiments include control conditions in which children do not observe aggression, there are no controls which are designed to examine whether or not observation of totally unrelated aggressive behavior might also have elicited the same characteristic aggressive actions toward the doll. Other findings of the experiments clearly suggest the strong effect of a generalized social facilitation from the observed aggression. For example, the incidence of nonimitative aggression i s usually as high as, and sometimes higher than, the incidence of aggression that is classified as imitative. Imitative use of a model could be assessed more readily, in these denionstrations of the influence of observation on children’s aggressive behavior, if separate indices of the individual behavioral components were presented, with greater attention to their fidelity to a model. I n the manner in which the findings are presented, i t i s not possible to judge the extent to which the children’s behavior reproduces specific expressive motor patterns of the potential model. Nor is it possible to judge whether their behavior is directed toward the same features of a target of aggression. More discriminate information about the relative incidence of the physical and verbal components of the children‘s aggressive behavior would be useful to an estimate of whether these components reflect imitative learning or the children’s prepotent dispositions. For example. in one of the experiments (Rosekrans & Hartup, 1967). i t is reported that children sometimes reproduce relatively unusual observed acts of aggression toward a clay figure. But the incidence of these acts is not specifically indicated. Likewise. some of the investigators suggest that children reproduce verbal accompaniments of aggressive behavior which are quite specific in their fidelity to the verbalization of the model. However. the incidence of these verbal expressions of aggression is lost in more general indices of the chil-

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dren’s behavior. Bandura (1 965a) notes in one report that children reproduce verbal components of observed aggression with a much lower frequency than they do motor components. Rosekrans and Hartup ( 1 967) examined the frequency of imitative verbal aggression specifically, and reported that children reproduced virtually none of the potential model’s aggressive utterances. The findings of another type of experiment provide somewhat more evidence of children’s ability to represent with some precision the relatively idiosyncratic and expressive motor or verbal behavior that they have observed. There are a number of experiments which have demonstrated that a child’s expressive imitation of a potential model is enhanced by the model’s nurturance toward the child. The indices of nurturance, which are either injected into the experiment o r assessed as naturalistic dispositions of the model, take the form of physical affection, verbal approval, dispensation of consumable treats or assistance, and other kinds of pleasurable interaction with the child. Bandura and Huston (1 96 1) found that children toward whom an adult model had first established a nurturant relationship reproduced more of the model’s task-irrelevant expressive behavior than did children toward whom the model had previously assumed a non-nurturant role. This finding was essentially replicated by Mussen and Parker ( 1 965). on a more naturalistic foundation, when they used highly nurturant and less nurturant mothers as models for the mothers’ own daughters. Bandura, Ross, and Ross ( 1963b) found that children more readily repeated the idiosyncratic patterns of behavior of an adult who dispensed nurturant resources, either to themselves or to another person, than they did the behavior of an adult who was the recipient of such resources. The findings of other investigators also indicate that nurturant or rewarding characteristics of either an adult or a peer model facilitate children’s reproduction of stylistic or task-incidental features of the model’s patterns of movement or verbalization (Hanlon, 1964; Hartup & Coates, 1967; Hetherington & Frankie, 1967). An experiment that is reported by Stein and Wright ( 1964) appears to be the only one in which imitation of a model’s expressive behavior was not enhanced by the model’s nurturance toward the child. However, an important and consistent contrast to this body of findings can be seen in the findings of a number of other experiments, in which the nurturance of an adult has been shown to have an ambiguous or even a disruptive effect on children’s dispositions to match the adult’s discrete and nonexpressive directions of choice or verbal judgements (Aronfreed, 1964; Bandura et a / . ,1967b; Rosenhan & White, 1967; Sgan, 1967). In all of the experiments in which children have the opportunity to re-

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produce the expressive behavior of a model, the imitative effect can be indexed by their adoption of behavioral features such as repetitive verbal utterances, an accent, o r unusual postures and motoric actions. Unfortunately, the extent of the effect cannot be fixed because these more topographically imitative features of the child’s behavior are thrown, in the treatment of the data, into a larger classification of behavior that includes discrete choice-matching indice\ such as the selection of a color. In a third type of experiment, the child’s reproduction of a model’s behavior is brought under aversive control through the child’s experience of punishment. The author (Aronfreed, I 964) has conducted an experiment in which children learn to apply a new self-critical label to their own actions by reproducing a verbal component of their previous external punishment. Other investigators have replicated this phenomenon with familiar verbal labels which already have a value that has been established by the child’s past aversive social experience (Grusec, 1966; Mischel and Grusec, 1966). A closely related type of experiment has been used to demonstrate aversive control over the child’s observational learning of sympathetic behavior (Aronfreed. 1969). These experiments will be described in the last section of this monograph. B . THELocus

OF

CONTROL OVER ATTENTION

Experiments which demonstrate a facilitative effect of nurturance on children’s imitation include some highly interesting and overlooked evidence of a competitive relationship between the child’s representation of a model’s expressive behavior and its representation of observed behavioral choices which are instrumental to the control of outcomes. This evidence points to the crucial functions of attention and cognitive capacity in the mechanisms of observational and imitative learning. In certain of the experiments which were summarized above, the child’s previous experience of nurturance from an adult uniformly appears to facilitate its subsequent imitation of expressive behavior that is incidental to the adult’s observed performance at a task. The nature of the task varies from one experiment to another, but the accuracy or effectiveness of the potential model’s performance is always indicated at least by informational outcomes. In many instances, the adult’s performance is set into a context of intentional observational learning for the child, so that there can be an assessment of the effect of observation on the child’s later performance at the same task (Bandura et al., I967b; Bandura & Huston, 1961; Hanlon, 1964; Mussen & Parker, 1965). But the nurturant role of the adult does not facilitate the child’s observational learning of the adult’s task-directed

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behavior. On the contrary, the findings often suggest that the nurturant attributes of the adult may disrupt the child’s observational learning of the contingencies between performance and outcomes in the task. Another point of importance is that all of the experiments which are being examined here have been conducted with young children of nursery school or kindergarten age. I t is not surprising that the young child’s respective dispositions toward the acquisition of the expressive form as opposed to the instrumental features of an adult’s behavior are differentially affected by the adult’s nurturance toward the child. The difference in the effects of nurturance is very probably related to the limited capacity that young children have been shown to have for the screening of taskrelevant from task-irrelevant information. Recent investigations which have been stimulated in part by Broadbent’s (1958) analysis of the concept of informational channels have shown that there is a gradual developmental increment in children’s ability to separate relevant from irrelevant information in the course of intentional learning, with the result that the ratio of incidental to intentional learning declines with age (Hagen, 1967; Hagen & Sabo, 1967; Maccoby & Hagen, 1965; Siegel, 1968; Siegel & Stevenson, 1966). It appears that young children do not show as much attentional and motivational persistence as do older children in learning which is governed by criteria or outcomes of performance. The contrast with the dispositions of adults is especially sharp, of course, since adults use extensive representational rehearsal of the task-relevant information that they have been instructed to learn and retain (Dornbush & Winnick, 1967; Postman, 1964). The limited information-processing capacity of young children is relevant to the fact that the nurturance of an adult does not facilitate, and may even disrupt, their observational learning of the adult’s performance under the discriminate control of outcomes. Young children may be strongly inclined to reproduce the expressive behavior of a potential model- behavior that is often incidental to the criteria of an effective outcome-controlled performance - in part because they give more attention to the expressive features of the model’s behavior. The nurturant or affectionate role of a n adult toward a child has, as its most salient component, the expression and transmission of positive affectivity. A child’s cognitive representation of behavioral features which are inherent to or correlated with this affective expression may require less information-processing capacity, in a number of respects, than does its representation of discriminative contingencies among cues, acts, and environmental outcomes. T h e child’s attention to the behavior of an adult, and its rehearsal of a cognitive representation of the behavior, may have different sources of affective control which respectively determine its imitation of expressive behavior and its

observational learning of task-oriented or instrumental behavior. Imitative learning of expressive behavior may be controlled by the affective value of the behavior itself, since expressive behavior is inherently a medium for the transmission of affectivity. In contrast, the observational learning of instrumental engagements of the environment will tend to be controlled by the affective value of external outcomes or criteria of performance. Relatively neutral stimuli which are brought into association with reward o r other events of established positive value for children will subsequently independently draw the children’s selective attention (for example, Parker & Nunnally, 1966). The nurturance of a potential model would tend to focus a child’s attention on the model’s expressive behavior not only because nurturance transmits positive affectivity, but also because it provides a context for the salience of behavior that may control the onset and termination of the child’s aversive a e c t i v i t y . Because of what may be a generalized disposition of children to control their own affectivity, the effect of nurturance in maximizing their attention to expressive features of an adult’s behavior may also be one of maximizing their cognitive and behavioral representations of these features. T h e findings of recent experiments suggest that a model’s nurturance toward a child may facilitate even the child’s reproduction of certain components of the punishment or disapproval that it has experienced from the model (Grusec, 1966; Mischel & Grusec, 1966). Grusec and Mischel ( I 966) have reported findings which indicate that the expressive behavior of a potential model does assume a more focal position in the child’s attention when the model has been nurturant toward t h e child. They asked yoking children to recall and reproduce the observed expressive actions o f an adult model from whom the children had previously experienced either nurturant or non-nurturant treatment. Since they did not rely on spontaneous imitative performance, but instead offered strong external incentives for accurate recall following both conditions of treatment, they were able to obtain a fairly reliable assessment of the children’s formation of cognitive representations of the model’s behavior. Children who had received nurturance from their model were superior in recall of the model’s expressive actions. Their advantage in recall extended to the criticism and delaying actions with which the model had sometimes reacted to their play activity-a finding which implies that nurturance enhanced their altention to both the positive and aversive expression of affectivity in t h e model’s behavior. Bandura. Grusec, and Menlove ( 1966) also have reported evidence which suggests that children’s representations of a model’s expressive behavior tend to be controlled by the inherent affective value of t h e be-

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havior rather than by the potential outcomes of its performance. They found that external positive incentives did not facilitate children’s recall and display of a model’s expressive behavior, even though the incentives were introduced before observation of the model. Ross ( 1 966) found differences in both incidental and task-oriented observational learning between two groups of nursery school children who were respectively classified, on the basis of their teachers’ judgements, as highly dependent and relatively independent. The dependent children showed more incidental learning of a model’s task-irrelevant expressive behavior than did the independent children: but the independent children showed better intentional learning of the task-relevant performance. These findings are in accord with the expectation that a child’s attention to an adult’s nurturant attributes will enhance the inherent value of the adult’s expressive behavior, and will therefore also facilitate the child’s imitative representation of the behavior, but may interfere with the observational learning of an outcome-controlled performance. One would expect the dependent child to be more oriented than its independent peer to the nurturant actions of potential adult models. Bandura and Huston ( 1 96 1 ) also noted a somewhat greater incidence of expressive imitation among dependent children. In conclusion, it appears that young children are highly attentive and sensitive to the changes of affectivity which are directly transmitted in the behavior of their potential models. The nurturance of a model seems to enhance this sensitivity and to strengthen the young child‘s disposition to represent and reproduce the expressive or topographic features of t h e model’s behavior. I t must be emphasized, however, that the extensive empirical work on nurturance a s a determinant of expressive imitation should not be taken as evidence that nurturance has a unique status in the affective control of children’s attention and cognitive capacities. Rosekrans and Hartup (1967) found that variation in the observed rewarding or punishing consequences of an adult‘s aggressive actions had, among the younger children in their sample, a much sharper effect upon a generalized social facilitation of subsequent nonimitative aggression than it did upon the more imitative reproduction of the same actions which had been observed. This finding suggests that the young child’s imitation of the expressive features of an aggressive model is, just as in the case of a nurturant model, less sensitive to anticipated outcomes than it is to the affectivity that is inherent in the imitative performance itself. There are u n doubtedly also many instances, particularly among older children, in which imitation of the structural or topographic features of a model’s behavior is dependent neither on the nurturance of the model nor on any inherently expressive affectivity in the behavior itself. Some kinds of high-fidelity behavioral products of imitation may be under the control of

the affectivity that is associated with environmental effects or correlated events for which the behavior is a motoric or symbolic representation. The sensitivity of young children to the expressive cues in the behavior of others may be complementary to the rudimentary status of the control that more symbolic mediators can exercise over their behavior. In contrast to young children’s sensitivity to expressive features of the verbal or nonverbal behavior of others, the behavior of older children comes increasingly under the affective control of their capacity for symbolic and abstract representation of cues and outcomes in their social environment (Lewis, Wall, & Aronfreed, 1963: McCullers & Stevenson, 1960). The common impression that young children imitate more readily than older children may well be attributable to a developmental decline in children’s orientation toward the expressive aspects of other people’s behavior.

VI. Constraints on a Theory When learning is based on behavior-contingent training, the child must first emit some relevant behavior. The behavior is then changed in its probability or form as a result of the selective contingencies of its outcomes. True observational learning, however, does not require that the child first produce behavior that has some similarity to another person’s behavior, and that the child then gradually increase the behavioral correspondence under the control of its direct experience of selective external outcomes. The foundation of observational learning appears to lie in the conditions under which the child observes another person’s behavior, rather than in the conditions under which the child itself behaves. In the case of certain kinds of expressive imitation of a model, where the behavioral product may have its own inherent value, it often seems that even the consolidation of observational learning does not necessarily require reinforcing external outcomes of the child’s performance. Children will very often reproduce a detailed sequence of another person’s behavior, after having observed the behavior only a few times, under conditions in which it is clear that their own performance has not previously received external social reinforcement. Their performance not uncommonly may be repeated many times either in privacy or in a context where it is obviously not directed to the control of potential social approval or reward. The performance will also frequently be independent, of course, of whatever cues might have been provided by the presence of the model. Gewirtz and Stingle ( 1968) have suggested that these phenomena can be understood if the child is credited with a generalized imitative disposition that includes an unlimited number of “responses.” The imitative

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behavior is presumed to be maintained by intermittent external reinforcement, and to be under the control of samples of cues which the child matches in conditional-discrimination learning paradigms. This approach appears to concern itself entirely with the external cues and outcomes which may enter into the control of the behavioral product of the child’s observational learning. Conversely, it appears to be entirely unconcerned with the mechanisms of learning which enable the child to produce the behavior in the first place. The theoretical problem that observational learning presents is the problem of how the child is able to reproduce with such speed and accuracy the observed behavioral performance of another person. It is not merely the problem of how the child’s reproduction can be brought under the control of external events. An adequate account of the relevant phenomena must also address itself to the child’s remarkable capacity to store and retrieve the behavior that it has observed -as manifested, for example, in the fact that its reproductions can become independent of the immediate presence of the cues which are transmitted in an external sample of the behavior. Conceptions of the observational learning process which attempt to place it within the paradigm of behavior-contingent training treat the observed behavior of another person only as a source of cues for the child’s performance of the correct behavior. However, when cues for learning are transmitted in the behavior of another person, their mode of transmission may be entirely incidental to the behavior that the child acquires. Either nonsocial cues or direct verbal instruction might be equally effective in providing information about the discriminate contingencies which will determine the outcomes of the same behavioral choices on the child’s part. Miller and Dollard (1941) recognized that the use of another person’s behavioral cues, a s set forth in their exposition of the “matcheddependent” paradigm, did not account for children’s learning of the patterned sequence or precise form of another person’s behavior. They tried to remedy this deficiency by suggesting, in their alternative conception of “copying,” that the child was also sensitive to cues of the extent of similarity between its own behavior and the behavior that it had observed. But the power of observational learning is in the child’s capacity to use the observed behavior of another person as a represetitation of the direction, the form, or the internal structure of its own subsequent behavioral reproductions. It is particularly true in the case of imitative learning that the observed behavior of another person cannot simply be treated a s a source of cues which the child uses for the control of its own behavior. The behavior is more accurately described as a representational sample, the intrinsic structure of which literally serves as a model for the child. Without some provision for the child’s capacity for cognitive representation, it would not be possible to use the cues and selective reinforce-

ments of a behavior-contingent training paradigm to account for the efficiency with which the child may acquire the sequence and topography of another person’s behavior. Under the conditions of naturalistic socialization, behavior-contingent training supports a wide latitude in the form of the behavior that the child is to learn. Since the reinforcing events of a social environment are not ordinarily contingent on the exact topography of a child’s behavior, they tend to induce behavioral dispositions in which a number of similar but differentiable actions have roughly the same value. In the learning of a patterned sequence of actions, it will often be difficult (if not impossible) for reinforcing events to exercise control over the fine grain of most of the components, since it is frequently the case that information about correct performance is given to the child only by outcomes which occur at the termination of the sequence. It is true that reinforcement’can be controlled in such a way as to induce children to match with some precision the observed actions of another person, as is shown in some of the interesting recent demonstrations which were described earlier (Baer er al., 1967; Baer & Sherman, 1964; Lovaas r t uf., 1966; Metz, 1965). Even when teinforcement is used with a high degree of selectivity, however, it is still necessary to specify how the child meets the criterion of performance that will be reinforced. When observational learning is controlled by valued outcomes of observed behavior, the child’s subsequent performance will reproduce those features of behavior which the child has observed to be criteria1 to the outcomes. T h e child may reproduce the sequential components of another person’s behavior, for example. when the sequence is critical to successful completion of a tusk or to explicit social rewards-as is illustrated in demonstrations o f children’s observational maze learning (Poliakova, 1958; Rosenbaum, 1967). I t would be more unusual, however, for the child to imitate the precise topography of a model’s behavior, if its observational learning were controlled by anticipated outcomes of performance, unless it had previously observed the outcomes to be contingent on correspondingly precise features of the model’s behavior. But children do often use representational imitation with a fidelity that goes well beyond the requirements of control over the external consequences which they have either observed or directly experienced. This phenomenon indicates that variation:, of behavior which are only grossly equivalent in their fidelity to a model are sometimes not at all equivalent in their inherent value for the child. A. S O M E A L I E R N A I

IVI

ONCFPTIONS OF

MECHANISMS

Some of the phenomena which have been taken to be evidence of children’s imitative dispositions ac~uallymight be more accurately viewed as

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primitive analogues of a conditioning process that rests on a gross similarity between the stimulation from another person’s behavior and the selfstimulation which is inherent in behavior that the child would spontaneously emit without the opportunity for observation. The external stimulation may have either an unlearned or an acquired value that adds a component of intrinsic reinforcement to the stimulation that the child can reproduce in its own behavior, because the two forms of stimulation have a rough correspondence and cannot be well differentiated by the child. Such a mechanism is suggested in Mowrer’s well-known proposition that the vocalization of infants may become more intrinsically reinforcing to them through the conditioning of positive affectivity to the crudely similar vocal properties of their nurturant caretakers (Mowrer, 1950. Ch. 24, 1960, Ch. 3). Some of Piaget’s (1951) examples of the development of imitative dispositions during infancy - particularly those which he uses to illustrate his conception of the second through the fourth stages- might also be interpreted as evidence of a movement of affective value from socially produced to self-produced stimulation. However, the existence of such a mechanism would account only for the affective value that observed behavior might acquire for the child as a result of the environmental contingencies in which the behavior is embedded, and possibly also for the subsequent generalization of that value across an undifferentiated and nonrepresentational correspondence to the child’s behavior. I t would not explain the child’s capacity to reproduce extensive samples of the complex sequential and structural features of the motoric and verbal behavior patterns which it has observed. The imitative behavior of children often is a high-fidelity replication of the exact structure or sequence of a model’s behavior. I t sometimes appears that an innovative and accurate imitative program emerges with remarkable suddenness in the child’s overt behavior, following only a limited exposure to a model. The speed of the programming very clearly points to the intervention of a cognitive representation of the behavior. Even if some allowance were to be made for “generalization” or drift from the child’s established behavioral resources, we still would not have begun to account for the high topographic precision of novel imitative behavior, or for the child’s ability to reproduce so quickly the order of components in a behavioral sequence. The role of representational cognition in these acquisitions is sometimes quite visible in the speed with which children’s imitation begins to gravitate, after only a few opportunities for practice, toward an exact fidelity to the original model, even though their practice may no longer be interspersed with exposures to the model. This phenomenon suggests that the imitative performance may have, at least during the initial learning and consolidation process, an in-

trinsic value that is governed by the affectivity which has become attached to the child’s representation ofthe model. I t also suggests that t h e intrinsic value may be proportionate to the fidelity of the imitation. Common observation makes it obvious, then, that children have the capacity to produce rapid behavioral acquisitions on the basis of their relatively brief observation of t h e behavior of others. But this capacity does not imply that observational learning and imitation have no component of overt practice. The power of cognitive representation will not allow the child to reproduce with immediate ease and precision a pattern of behavior that has motor components which are alien to its available repertoire. There is a variety of evidence which confirms the expectation that cognitive representation will attain fidelity to a model much more quickly than will a corresponding motor representation (Maccoby & Bee, 1965; Miller, Galanter, & Pribram, 1960, C’h. 6 ) . And i t may well be the case that many naturalistic instances of children’s observational learning and imitation give an impression of speed and efficiency which is partially attributable to the past history of the child’s cxposure to similar models and of its opportunities to practice the imitative program. Closer analysis of children’s initial imitative productions would no doubt often reveal only a low replicative fidelity to the precise patterns of motor outflow in the behavior o f a model. Whatever motor precision is attained would come only after some opportunity for practice. The speed and accuracy of cognitive representation in observational learning, and the fidelity of form that is sometimes apparent in t h e case of imitation, would instead be more visible in the child’s behavioral assembly of the sequential and structural relationships within the observed behavior-tor example, in the integration of movements or in the transposition of embedded components. In order to take account of the apparent speed of observational learning, and of its relative independence of externally reinforced practice, some theorists have supposed that the child engages in covert rehearsal of observed behavior during or after the period of observation (Logan et ul., 1955, pp. 149-15 1; Maccoby, 1959: Sears, Maccoby, & Ixvin. 1957. Ch. 10). I t is quite clear that the opportunity for oi-ert practice does facilitate the observational learning process (Lumsdaine, 196 I ). and that people will sometimes engage intentionally in overt rehearsal of the observed or even the assumed behavior of another person (Berger, 1966). Covert rehearsal also would surely advance the representational assembly or structuring of the elements of a behavioral program that is being learned on the basis of observation. Bandura c’f trl. ( 1966) found that children w h o were explicitly instructed to verbalize to themselves the actions of a model, during the course of observation. showed better recall and reproduction of the actions than did children who were not told to verbalize. The capacity

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for covert rehearsal in itself cannot account, however, for the child’s rapid coordination of the sometimes novel and complex programs which are the object of the rehearsal. And to the extent that the rehearsal is understood to be a representational process, without the engagement of the motor components of behavior, it will also have little utility toward an account of the precision that the child may finally attain in its overt imitative performances. Of course, children may give the behavior of their models much overt rehearsal which is either private or miniaturized to the point that it is difficult to observe. But there is no reason to think that the purely representational rehearsal of a behavioral program can flow easily into precise overt performances of what may be topographically new forms of behavior for the child. Whether the child engages in overt or covert rehearsal of the observed behavior of others, it must be able to store and retrieve the program of behavior that it will rehearse. The complexity and fidelity of the programs which can be stored, often under limited opportunity for observation, are important aspects of the evidence that the child has the capacity to acquire fairly rapidly a cognitive representation of the behavior to be reproduced. The performance of children on many tasks which have been used for the assessment of intelligence reveals developmental increments in the ability to copy motor and verbal behavior patterns of varying degrees of complexity (Biihler, 1935; Gesell ef i ~ l . , 1940; Shirley, 1933: Terman & Merrill, 1937). The findings of studies of the capacity for role-playing and mimicry also indicate increments with advancing age and intelligence (Berges & Lezine, 1963; Bowers & London, 1965; Kwint, 1934). A very interesting clue to the interaction between a child’s cognitive and behavioral representations of a model is indirectly suggested by the findings of Russian investigators who have shown that auditory discriminations are facilitated by asking a subject to use vocal reproductions of sounds as discriminative responses (Chistovich, Klaas, & Alekin, 196 1 ; Leontiev, as described by Pick, 1963). These findings could be extended to arrive at the inference that a child’s cognitive representation of a model also may be consolidated by its own behavioral reproductions. Another reason for the requirement of cognitive representation in an account of the child’s observational learning is the discrepancy, from the point of view of the child’s concrete perception, between the stimulus properties of the observed behavior and those of the child’s reproduction. Conceptions of the observational learning process which emphasize either the conditioning of affectivity to proprioceptive cues or the formation of perceptual-motor linkages by contiguity (for example, Mowrer, 1960, pp. I 12- 1 16, or Sheffield, 196 1) do not provide a satisfactory account of the relevant phenomena, in part because they do not focus on

capacities which would allow children a fairly saltatory learning process for the storage and reproduction o f the assembly of intrinsic structural and sequential features of observed behavior. Such conceptions also have another severe limitation that is inherent in the very nature of any nonrepresentational perceptual feedback. This limitation can be exemplified in the dependence of children on the visual modality for so much of their observation of the nonverbal behavior of potential models. Their reproduction of the behavior will produce stimulation in a number of modalities, including all of the proprioceptive cues of movement, but will not ordinarily produce even an approximation to the visual cues which were available during the original observation. However, this discrepancy would not reduce either the accuracy or the potential intrinsic value of the child’s performance, if the performance were governed by its fidelity to a cognitive representation, rather than by the match between its direct perceptual feedback and the form of the concrete cues which were originally given in an external sample of observed behavior. In an experiment that was recently reported by Wapner and Cirillo ( 1 968), the same point is demonstrated in a more task-oriented and nonspontaneous setting. When children and adolescents were commanded to reproduce the hand movements of an adult whom they were facing, the number of correct left versus right translations increased with advancing age. Conversely, the number o f mirror-like translations decreased with advancing age. Piaget notes that infants already begin, during what he describes as the fourth stage in the development of imitation, to reproduce the actions of others even when they cannot directly perceive the correspondence of their own actions (fot example, sticking out the tongue). All of these observations indicate that mobility of cognitive representation, across the immediate stimulus properties of external behavioral samples, makes the child’s subsequent performance independent of control by a self-produced fidelity to an originally direct perceptual representation. A large number of investigators and theorists have assumed that observational learning must be based entirely on contiguity mechanisms, since it so often occurs under conditions in which it does not appear to be under the control of the classes of positive or aversive events that are conventionally identified with the operations of incentive or reinforcement (Allport, 1924, pp. 240-241 ; Handura, 1962, 1965b; Berger, 1966; Holt, 193 I , pp. 1 12- 1 19; Humphrey, I92 I : Maccoby, 1959; Piaget, I95 1, Part 1; Sheffield, 1961). These theoretical conceptions d o not require the child’s observational learning to be controlled by the potential affective value of a behavioral reproduction, although both Bandura and Maccoby suggest that incentives or outcomes may control performance after an acquisition process has taken place. Both Holt and Piaget have pointed

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out that a close temporal succession between corresponding actions of the child and another person is inherent to the child's early experience in a social environment. It is quite possible that infants do acquire some disposition to respond to another person's actions with corresponding actions for which they have acquired either sensory-motor or representational schemas, in part because of past temporal contiguities between the successive actions. But it is not apparent that such a disposition would be independent of the affective value of the actions. And the mechanisms which are proposed for such a disposition would hardly subsume, in any case, the great range of contingencies under which children will reproduce the previously observed behavior of others, including those in which they may replicate sequential or topographically novel behavioral programs even though the model is no longer present. Many paradigms of observational learning give the child the opportunity only to observe, and not to perform, during its exposure to another person's behavior. If a contiguity mechanism of learning had the requirement of a close temporal association between stimulus and overt response, it would therefore not appear to account for any kind of attachment of the child's behavior to cues in the course of observational learning. If the contiguity concept were instead being extended to an association between the external cues which control another person's behavior and the child's perceptual or cognitive "responses" in coding the behavior, then the concept might be useful i n accounting for the subsequent elicitation of the child's perceptual or cognitive representations of the behavior by relevant cues in t h e environment. But it would not provide an understanding of how the representations themselves are formed and stored. Nor would it explain how the representations exercise control over the child's overt performance of the behavior. The primary deficiency of the contiguity concept. in an account of observational learning, lies in its failure to make any provision for an affective component of the control that t h e child's cognitive representations may exert over its overt behavior. The suggestion that explicit incentives or reinforcements influence t h e child's performance, but not its acquisition of a cognitive representation of the observed behavior, in no way resolves the problem of allowance for an affective component. For example, it does not specify any mechanism of affective control over the child's formation of a durable representation of the behavior that it observes, even though such a mechanism appears to be crucial to the role of attention in observational learning. Nor does it explain the functional value of spontaneous imitative performances that the child may emit without any apparent control by t h e anticipation of outcomes which are associated with reward or punishment.

Contiguity theories seem to be overly reactive to t h e fact that observational learning can occur without explicit rewards or punishments which are contingent on the performance of either the observer or the person whose behavior has been observed. As was pointed out earlier, behavioral acquisitions that are based on observational learning may be controlled by the affective value of environmental effects which serve as sheer informational outcomes o f :I performance. The more highly symbolized and internalized iise of such informational outcomes may, of course, not always be readily available to children. I t should not be surprising that the more impressive demonstrations of observational control over learning or performance at a task (Berger, 1966; Lumsdaine, 1961), in the absence of opportunity to observe explicit rewards of another person's performance, have been carried out with adults rather than with children. Quite aside from the variety of outcomes which may reinforce performance at a task, the events which are conventionally classified as rewards and punishments give i i i-:ither impoverished view of the sources of affectivity in a social environment. A great many different kinds of stimulation that have ;I pleasurable value for the child may be directly transmitted in the observed behavior of another person, or may provide an external context i n which the behavior is observed. Particularly in the case of imitation of expressive ot other topographic features of observed behavior. it is necessary to expand our view of the stimulus events which may have a positive affective value for the child. Piaget (19s 1 ) observes that young children often reprodlice the behavior of others in order to produce either intrinsically or externally pleasurable stimulus consequences. These consequences sometimes appear to have a value for the child that is only minimally dependent on its previous social experience. However, it is difficult to do more than point to the phenomena which suggest the importance of an affective component in observational learning. There is very little empirical knowledge of the nature and magnitude of the affective value that various social and nonsocial stimuli may impart to the child's representations of the behavior of others. There are two other characteristics of observational learning which also indicate that it has affective prerequisites. First, observational learning is selective. Children do not imitate all of the behavior of the potential models whom they observe. The induced changes of affective state which are associated with their observation o f particular kinds of behavior may be one ofthe determinants ofthis selectivity, as we noted earlier in the analysis ofthe role of attention in observational learning. And the behavior that they are most disposed to represent kind reproduce may be a useful source of information about the relative values of the diRerent forms of stimulation which control their affectivity in a social environment. Second. the

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products of observational learning can be very persistent. For example, children sometimes display fairly precise imitative productions repeatedly, over a long period of time, even though the fidelity of their performance may not elicit reinforcing social consequences. Their imitative performance seems to have an intrinsic value that is closely bound to its representation of the features of an original external model. Some theorists have proposed that the attributes of caretakers become powerful social stimuli for the elicitation of the child’s positive affectivity, as a result of their previous association with the child’s experience ofnurturance and affection, and that the child therefore acquires a very generalized disposition to reproduce many of the attributes of its socializing agents in its own behavior (Mowrer, 1950, Ch. 2 1, 1960, Ch. 3: Sears et al., 1957; Whiting & Child, 1953, Ch. 1 I ) . I t appears also to be assumed that the child is particularly likely to provide itself with the acquired value of these attributes when its potential models are absent or their affection has been withdrawn. These extensions of conditioning concepts are quite similar to Freud’s ( 1933) original observation that children were disposed to reproduce the properties of an absent “love object.” We have already reviewed the findings of a number of experiments which demonstrate some of the conditions under which young children are indeed more inclined to reproduce the expressive actions of a nurturant model than those of a non-nurturant model. There is also some more naturalistic and indirect evidence, from surveys of the correlates of variations in child-rearing practices, which suggests that nurturance may facilitate children’s adoption of certain of the attributes or values of their parents (Bandura & Walters, 1959; Bronfenbrenner, 1961; McCord, McCord, & Howard, 1963; Sears et al., 1957, Ch. 10; Whiting& Child, 1953. Ch. 11). Although it is clear that the nurturance of an adult may facilitate a child’s disposition to reproduce the adult’s behavior, the observational learning of children has a range that goes far beyond the control of the affectivity that can be directly asscciated with their experience of nurturance. Some experimental paradigms of socialization have been designed to demonstrate that children will reproduce an adult’s verbal criticism of their own actions (Aronfreed, 1964), or that they will reproduce the sympathetic actions which have been directed toward them by an adult (Aronfreed, 1969), when they are first exposed to conditions under which their observation of the relevant behavior has been closely associated with termination of their own anxiety or distress. These experimental effects, which will be analyzed later in some detail, are not dependent on a more general context of nurturant treatment from the adult, but instead appear to be controlled by the value that the reproduced behavior has acquired for reduction of the children’s aversive experience.

That the experience of nurturance from another person cannot be a crucial determinant of the child’s disposition to reproduce the person’s behavior is made evident by ii number of other considerations. The kind of social stimulation that is specifically designated as nurturance or affection is only a small sample of the variety of social stimuli which, from the point of view of the child’s experience, may attach positive value to the observed behavior of an adult. Many stimuli which may originally acquire their affective value from their association with the child’s early experience of care and affection-for example, verbal or nonverbal indicators of social approval and attention- may t h e n independently transmit some of their value to the observed behavior of others. Of course. there are also other kinds of social stimulation which may have a positive value that is entirely independent of the child’s previous experience of a nurturant environment. The interesting and pleasui-able effects of certain forms of aggressive behavior, for example, m a y be important determinants of the ease with which children’s aggression can be elicited by observation of the aggressive actions of another person (Bandura & Walters, 1963). An inventory of the forms of stimulation which may govern the functional value of the child’s observational learning must be further extended to include events which can induce afectivity even though they are only indirectly experienced by the child. C’hiltlren may respond empathically or vicariously to social cues which convey the affective experience of another person. And they are also highly sensitive to the affective value of the observed external outcomes of another person‘s behavior. Some theorists have even proposed that ;I model‘s control of valued resources is the most effective determinant of‘the child’s disposition to adopt the attributes of the model (Kagan. 1953; Maccoby. 1959; Whiting. 1960). B. COGNITIVE T E M PAII I s

AND

AFFECTIVECouPi-iws

A child’s cognitive representations of the observed behavior of others might usefully be conceptualized ;ISa set of templates. T h e phenomena of observational learning have ;I number of properties which lend themselves to the concept of a template. Tu begin with, there is the requirement that the child must be able to store for reproduction the direction, the sequence, and sometimes the intrinsic structure of the behavior that it has observed. Secondly, the child’s cognitive representations must be capable of being used to generate parallel representations in its overt behavior. Finally, the concept of a template encompasses the variety of devices which may be available t o the child’s cognitive capacities. For example, the child’s storage and reproduction of the behavior that it observes need not be dependent on a direct or “photographic” represen-

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tation of the behavior. The child may also bank the programs of reproducible behavior in cognitive structures which have more abstract, symbolic, or hierarchical features. Although all forms of observational learning would require the child’s use of representational templates for storage and guidance of the behavior that is to be reproduced, it is necessary to make some important distinctions among the different forms which the templates may take. One of the most critical of these distinctions can be found in the variation of the fidelity with which the templates represent the specific features of observed behavior. The nature of this variation of representational form actually can be best understood through an analysis of the various sources of affectivity which a social environment may provide for control of the observational learning process. The behavior of other people in the child’s environment is embedded in a context of inherent and associated stimulation that has an affective impact on the child. I t will therefore often be true that the changes of affectivity which are induced in the child, in close conjunction with its observation of another person’s behavior, become directly coupled to the cognitive template that the child forms for the behavior. The coupling would occur through processes which are essentially like those of Pavlovian conditioning. The child may then reproduce the observed behavior, if the change of affectivity that has become attached to its template has a potential reinforcement value. For our purposes here, it is sufficient to specify that the required changes of affectivity be an induction of positive affect or a reduction of aversive affect. Whatever the externally reinforcing consequences of the behavioral reproduction may then be, it can also now have a certain amount of intrinsic value, since it strengthens or articulates the activity of its corresponding template and t h e affectivity which is coupled to that template. I n other words, the overt behavioral reproduction is to some extent under the control of the affective value that has become attached to the template. The affective value of much of the behavior that a child observes in a naturalistic context is transmitted through the child’s direct experience as the recipient or object of the behavior. Potentially replicable components of another person’s behavior may themselves have an inherent value for the child-for example, when the child reproduces actions which other people have used to express affection toward it or to relieve its distress. Or the reproducible features of another person’s behavior may not have inherent value initially, but may acquire value because they are interwoven in time with other features which do have an established value. For example, a parent’s instrumental skills or expressive actions may acquire value because they occur in close contiguity with the parent’s nur-

The Problem

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lrniration

27 I

turant behavior toward the child. Under either of these two conditions, the child’s behavioral reproduction itself may acquire an intrinsic value that shows some independence of its original sources of affectivity in an external social medium. It should also be noted that certain kinds of expressive behavior which are emitted by others may acquire a rather generalized value for elicitation of the child’s affectivity, even when they may not be directed to the child. Children may respond empathically even to relatively trivial and unfamiliar components of another person’s behavior, if they can place those components within broader and more familiar classes of behavioral expressions of afiectivity. Thus, children may easily respond to and reproduce the affective expressions which they identify in another person’s exercise of skill, vigorous activity, or control over the environment. Observational learning may also be governed by the affectivity that is induced in the child by the observed outcomes of another person’s behavior, rather than by the affective value that is inherent in the behavior itself. The affective value of the observed positive or aversive consequences of another person’s actions may become directly attached to the child’s cognitive template of the actions, provided that the actions and their consequences are sufficiently close in time. And the child’s behavioral expression of the actions which are stored in the template may therefore have some intrinsic value even before the behavior is directly exposed to the control of its own outcomes. I n some instances, the valuc of the outcomes of another person’s behavior may be directly experienced by the child. For example, the behavior of an adult may produce external environmental effects which are pleasurable for both the adult and the child who observes the behavior. But the child also has many opportunities for observational learning in situations where it does not directly experience the outcomes of another person’s behavior. Control of the learning process under these conditions may sometimes be mediated by the child’s empathic or vicarious response to cues which transmit another person’s affective experience - either the person whose behavior produces the outcomes or others who experience their effects. However, the affective value of the observed outcomes for the child may lie entirely in its observation of the outcomes themselves, or in the informational value of the contingency between the observed behavior and the outcomes. Many demonstrations of outcome-controlled observational learning which are attributed to empathic or vicarious experience (Bandura, 1965b; Kanfer. 1965) could undoubtedly be conducted with equal effectiveness if the nece ry environmental contingencies were displayed through disembodied actions in which the presence of another human being was not discernible.

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When the affective value that becomes coupled to a child’s representational template of observed behavior is originally inherent in the behavior itself, the child’s observational learning tends to be focussed on the intrinsic features of the behavior rather than on its instrumental control over external outcomes. As has been already noted, this type of learning is especially characteristic of (though not restricted to) the child’s adoption ofthe behavior that its models use to express and monitor their own affectivity. Because expressive behavior is highly affect-laden, there are sharp gradients of affectivity which are associated with its specific components. When potentially reinforcing changes of affectivity are induced in the child by its observation of expressive behavior, the child tends to form a cognitive template that has high fidelity to these specific features of the behavior. I t also tends to reproduce the behavior with the same degree of fidelity. The child’s imitative behavioral reproduction in fact appears to be very closely monitored by the template, in such a way that it matches those precise features of the original external model which transmitted potentially reinforcing changes of affective state. I t seems reasonable to infer that varying degrees of fidelity in the reproduction are a function of a gradient of affective value along the representational dimensions of the template, and that control of the magnitude of the value by fidelity of the match accounts for the topographic precision of this type of observational learning. For reasons which will become apparent shortly, topographic precision of the surface of behavior in itself should not be overemphasized as a criterion of imitation. The more telling criterion lies in the structure or patterning of the behavior. Topographical precision is only sometimes correlated with fidelity of structure. The concept of imitation may therefore have maximum utility when it is used to designate a variable property of the behavioral products of observational learning- the property of structural fidelity to an original external model, which is in turn dependent on the formation of a cognitive template that serves as an internal representational model. This property is much less in evidence when the child’s observational learning is controlled by the affective value of the outcomes of observed behavior. Outcome-controlled observational learning provides a basis for cognitive templates which represent discrete act-outcome contingencies and also the sequence of components in a pattern of instrumental behavior. But there is room for a great deal of variation in the form of the behavioral product of this kind of learning, since the control of outcomes usually requires very little or no fidelity in the form or structure of the behavior. The representational template that the child forms for the observed behavior can be quite gross and undifferentiated, since the affective value of the behavior will be determined by its instrumental effects,

rather than by gradients of affectivity which are associated with its intrinsic components. The template nlay be. for example, only a representation of the general direction in which to produce certain effects in the environment. T h e child may thus learn to use discrete or sequential actions discriminately, in order to produce the same control over outcomes that it has observed in another person’s txhavior, but with a resemblance to the other person’s behavior that is only trivial and grossly constrained by the situation and by long-established behavioral dispositions. If potentially reinforcing changes of affectivity become coupled to a child’s cognitive template for the behavior that it has observed, then the child’s subsequent behavioral representation of the template in overt performance will tend to have a certain amount of intrinsic value even upon its first occurrence. The mechanism for the establishment of this value requires that the behavioral reproduction be controlled by the affectivity that has become attached to the template in the absence of the overt behavior itself (during the period o f observation). The findings of a number of experiments with animals indicate that external stimuli can acquire motivating and reinforcing properties. for either positive or aversive control of behavior, when they arc first exposed to Pavlovian conditioning procedures in the absence of the overt behavior that will subsequently be used to test their acquired value ( K n o t t & Clayton, 1966; Rescorla & LoLordo, 1965; Sheffield, 1965: Solomon & Turner. 1962: Stein, 1958; Williams, 1965). Of course, the alfectivily that social experience couples to a child’s internal representational template of an external model may extinguish if it is not reinforced or confirmed by the child’s subsequent experience-for example, by exlernal reinforcement of the child’s behavioral expression of the template, or by reinstatement of opportunities for observation in the original affective context. I t is possible that certain kinds of imitative behavior, which are not dependent on external outcomes. may tend to become somewhat automated out of the control of affectivity after the original learning process, although perhaps never to the extent that their value becomes entirely divorced from the reinstatements of affectivity which are available in a social environment. Some forms of imitative behavior may iilso become so habitual as to be released from t h e control of their original cognitive templates. Their control may become entirely localized, at ;I sensory-motor level, in the self-produced cues which are directly inherent i n their very performance. Direct external reinforcement is the most important source of selective maintenance of many of the behavioral dispositions which children acquire initially through observational lenrning. In addition to their selective control by explicit social rewards. some behavioral products of observational learning are reinforced by external consequences which are inher-

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ently correlated to their performance. For example, observational learning of various kinds of active behavioral control over the environment -of which aggressive behavior might be one example - may be subsequently reinforced by the immediate effects that they produce on the people or objects toward which they are directed. Bandura ( I 965a) has used explicit external incentives to show that children sometimes retain more of what they have observed in another person’s aggressive behavior than they will reproduce spontaneously. Grusec ( 1 966) has reported findings which indicate that termination of punishment will reinforce children’s overtly verbalized self-critical reactions, after the reactions already have been acquired on the basis of observational learning. Common observation indicates that behavioral dispositions which children acquire through observation may also be extinguished or suppressed by either nonreinforcing or punitive consequences. Children may also acquire many representational templates of the behavior of models which cannot be given an overt expression within their own socially prescribed roles, and which therefore may be stored in a dormant state until maturational and environmental conditions provide appropriate stimulus controls and incentives. I n general, no matter how powerful may be either the intrinsic value or the potential external outcome value of a child’s behavioral reproductions of a model, the reproductions will always continue to be sensitive to the discriminative control of external situational cues. I t should be noted that the child’s direct experience of external rewards, or its observation of the rewarding outcomes of another person’s actions, may sometimes serve to increase the fidelity of an initial behavioral product of observational learning to specific criteria of form or sequence. lf the child observes that valued outcomes are controlled selectively by certain precise features of another person’s behavior, then the affective value of the outcomes may become coupled to a template in which the child represents those features with increasing fidelity. Likewise, selective reinforcement of the child’s own behavior may gradually produce an imitative performance that is more topographically precise or structurally intricate than the behavioral features which originally were coded into the child’s cognitive template of an observed model. The concept of affectivity contributes to an understanding of the control that the child’s attentional dispositions exercise over the cognitive ingredients of the observational learning process, as well as to an account of the control of overt behavior by the templates which the child already has acquired. Attention is a prerequisite of all forms of observational learning. Cognitive templates and their affective couplings can be formed only to the extent that the child is oriented toward external samples of

behavior and toward the inherent or correlated stimulus events which have an affective value for it. We have already noted evidence of the interaction between affectivity and attentional control in the contrast between the conditions which re s pec t i v c Iy fac i 1it ate chi Id re n ’s ex pre s s i v e i mi t ation or their observational learning of‘ performance at a task, and also in the effects of social facilitation and local stimulus enhancement on the observhonal learning of primates. A verbal medium of socialimtron also may focus a child’s attention and cognitiire representation more eliiciently on the behavior of another person. F c r example, verbal instruction can be used to enhance observational control of the child’s learning or established behavioral dispositions, when it is used to give the child an orientation or set toward specific aspects of observed behavior. Hatidim and Harris ( 1 966) found that a probleni-solving instructional orientation toward the syntactic constructions of adults facilitated children’s adoption of the same constructions. Sheffield and Maccoby ( 196 I ) have summarized findings concerning a number of instructional devices which enhance adults’ observational learning of perceptual-motor tasks by directing their attention to distinctive cues in filmed demonstrations. The most powerful use of ;I verbul medium in observational learning is the use of language in the description of propet-ties of the behavior to be learned. This use of a verbal mcdium will enhance learning not only because it can focus the observer’s attention, but also because it introduces a very poweiful mode of represenlation of the form of the observed behavior and of its criterial feature5 for the control of outcomes. Any treatment of observational learning could hardly fail to take note of the speed and efficiency with which direct verhal instruction may induce a criterial form of behavior, even when the lexner may have had no opportunity to observe a sample of the behavior (Handura, 1962; Skinner, 1953, pp. 1 19-12?). But the role of language in observational learning in no way changes the requirements for ;I basic conception of the mechanisms of observational learning. Except when speech itself may be the behavioral product of imitative acquisitions, external verbalization does not have the status of a model merely because it can control the child’s learning of an overt behavioral performance. ‘l‘he verbaliza:ion is rather a mode of representation that either enters into the formation of a new cognitive template (where an external behavioral sample is available) or engages templates which were already available from past experience. Poliakova ( 1958) noted that children’s observational learning of the correct patterns for walking through ;I maze showed more intelligent generalization, and was less closely bound to t h e original demonstrations, if the demonstrations were accompanied by verbal instructions. Bandura et

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ul. ( 1966) found that children who were instructed to describe the expressive actions of a model to themselves were better able to recall and reproduce the actions than were either children who observed the same actions without the instruction to verbalize or children who were asked to give verbalization to distracting stimuli. However, Rosenbaum ( 1 967) reports the interesting finding that the opportunity to hear another child’s overt verbalization of appropriate numbers, at the completion of correct choices in a hand-negotiated maze, facilitated both observers’ and performers’ subsequent retention of the correct pattern for the maze: whereas the requirement of active verbalization of the numbers did not facilitate retention. This finding suggests that although symbolic representations may facilitate visual-motor coding of external information during observational learning, the requiremtnt of overt communication of the symbolic representations may actually interfere with the formation or rehearsal of a cognitive template for the information. In general, it might be expected that the power which language adds to cognitive representation would be especially visible in observational learning that depends on the child’s representation of discriminative cues and contingencies for the control of outcomes by the direction and sequence of potential actions. Language may be less adaptable to the representation of expressive behavior or of the precise topography of any form of behavior (although there may be variations among languages in this respect). The cognitive templates which are required for the more imitative kinds of observational learning are not necessarily simple copies or direct images of external models. Nor are their behavioral expressions limited merely to complete or partial reproductions of the original samples on which they were based. Some kinds of templates are capable of generating new behavioral productions which are derivatives of the form in which the original external model was stored. Such templates may employ rules or operators which give them the character of constructions on an external model rather than of copies. The constructed properties of these templates d o not require an extension of t h e concept of imitation to any kind of control of behavior by cognitive representations which are formed on the basis of observation -that is, they d o not require a retreat to the more general case of observational learning, without the further criterion of fidelity to the form of a model’s behavior. The criterion of high-fidelity representational use of a model can be found in behavioral reproductions from which one can infer the presence of cognitive templates that capture the underlying structure of the model’s behavior. I t is this intimate structural correspondence to the model that defines imitation. The more iconic and photographic identities which are sometimes found on the topographic surface of imitative behavior are probably more attributable to

sensory-motor templates than they are to representational templates. Behavioral reproductions of a model would more properly be called mirnicry when they show only this external or surface fidelity. True imitation is identified by its cognitive mobility - by the representational impositions that it makes upon the concrete perceptual input from an original model. Children may have capacities t o r a number of different kinds of templates which vary greatly in the extent of their mobility and freedom, with respect to original external models, and also in the extent to which they are intrinsically prestructured within the nervous system. A sensory-motor type of mimicry may be present in children’s echolalia, or in their stimulus-bound and nonrepresentational imitation of certain patterns of movement of the body. The behavioral indices which Piaget ( 1 95 1) uses, in the outline of his conception of the development of imitative capacities during infancy, suggest a progression of sensory-motor templates which culminate in cognitive representation. But Piaget does not appear to carry the analysis of representational imitation beyond the level of a direct image or copy of the external model. The imitative capacities which some animals appear to have often seem to rest only on the more limited and prestructured types of templates within the broader range that is available to children. For example, there is evidence that the songs of birds can have a very high topographic fidelity to a model. But these songs appear to be entirely dependent on templates which are sensitive only to the inherent perceptual feedback that they provide. T h e y do not seem t o require templates which are cognitive in the sense that they impose representational constructions on an external sample. T h e “imitative” component of the songs is restricted to the sheer phonetic reproduction of the stimulation to which the birds have been exposed. In a comparative approach to the psychology of imitation and observational learning in general, it may be useful to allow for important distinctions among animals in the degree of capacity for even the truly representational templates which are primarily reflective copies and do not code the information from a model in a more hierarchical or structural form. The observational learning capacities of primates, for example, may be partially dependent o n their relatively highly developed social orientation toward one another’s behavior and on their consequently fuller representation of observed patterns of behavior, in contrast to the representation by lower animals of what may be merely points of movement or contact in the environment. The extensive work that has been done on birds’ acquisition of their characteristic songs is a convenient point of entry into the larger problem of the extent to which the templates for imitative behavior must be re-

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garded as being set down in the nervous system. Recent investigations of the songs of birds make it clear that most birds have a strong innate disposition to produce a species-specific phonetic pattern in their song, but that normal song development usually requires exposure to stimulation which can serve as a model for what has been characterized by some ethologists as imitation (Armstrong, 1963; Hinde, 1966, pp. 332-338; Marler & Hamilton, 1966, pp. 442-467; Thorpe, 1959, I96 1 ). T h e innate disposition toward the coding of a specific song seems relatively resistant to experience in some species (for example, Lade & Thorpe. 1964). I n the case of certain domestic fowl, which have a pattern of vocalization that can be called a song only with some generosity, the pattern may develop even though the young bird has been made deaf (Konishi, 1963). For the great majority of species, however, the development of a song appears to be very sensitive to early exposure to the song. This sensitivity is demonstrated in the effects of exposure during the period of maximal imprintability, in the acquisition of characteristics of the song of another species, and in the failure of development ofthe song when the birds are deprived of appropriate stimulation. Stevenson (reported in Hooker, 1968) has used operant techniques to show that the opportunity to hear the full adult song will serve as a reinforcing event for the young male chaffinch which has begun to acquire its song under natural rearing, but not for the handreared chaffinch which has had no early experience of the song. This finding is extremely interesting because it suggests that experience may couple some intrinsic atfective value t o the template for the song. The findings of a number of other investigations also may be interpreted as evidence that the vocalizations of birds are interwoven with imprinting and maintenance of social bonds, and that the templates for the vocalization become coupled with an affectivity for which the birds are innately primed, but which is dependent on early exposure to the vocalization of other birds (Hooker, 1968; Thorpe & North, 1966). The songs of birds constitute only one band within a spectrum of phenomena that reveals great phylogenetic variability in the innate and experiential determinants of the templates which animals have available for their communicative signals. Wennet- ( 1 969) recently has mounted persuasive empirical evidence to argue that the remarkable correspondence of flight paths which seem to be transmitted in the “dance language” ofthe bees (von Frisch, 1950, 1967) is attributable to a direct release of innately integrated motor patterns by external stimulation from the dancer, together with some effect of conditioning, rather than to any representational or abstracted coding of information. On the other hand, it has been noted, even in the case of birds, that a concept of innate prestructuring of templates is not at all useful toward an account of the ability of certain

highly mimetic birds to reproduce an astonishing variety of phonetic patterns (Hooker, 1968; Thorpe. 1063: Thorpe & North, 1965). The mimicry of these birds is a salient case of the more general problem of the flexibility or experiential structuring of templates of vocalization for both short- and long-term storage. F o r example, Lilly ( 1962, 1965) has reported that dolphins easily reproduce the number and duration of the vocal bursts which they hear from one another or from human beings. Investigators of vocal communication in primates also have pointed to evidence that a complex series of differentiated vocal signals is acquired through social transmission. even though the templates for decoding and production of the signals seem to be prcstructured in the animals (Bastian, 1965; Marler, 196s). For these higher animals, there may also be acquired structural impositions on phonetic input, which are required in order to obtain the “meaning” of a signal. The most interesting exaniple of the problem of separating the innate and acquired determinants of templates for imitation can be found in children’s language. Recent devclopments in the psycholinguistic treatment of syntactic structures have led ;I number of theorists to the specul,‘1 t ’ton that learning. and imitative learning in particular. could not possibly provide a satisfactory account of the child‘s acquisition of grammar (Chomsky, 1959, 1966; Fodoi.. 1966; McNeill, 1966, 1970). I t is their view that the child’s nervous system is innately preprogt-ammed with syntactic structures or analyzers t’or which exposure to a natural linguistic environment acts a s a catalytic cxperience. Among the arguments which have been offered in support of t hese itssertions, the most strongly emphasized have been the presence 01’ rules o r hierarchical structures in a grammar, the apparently unlimited cqwcity of children to generate new sentences on ii grammatical model. ;ind the relatively rapid appearance of grammar during a “critical period.“ Ixnneberg (1962. 1967) also has argued, on the basis of a variety of e\,idence, including a case of congenital anarthria- a child who could understand speech, but was unable to produce it - that language acquisition cannot depend o n any form oflearning which requires an overt motor output. Close examination of these atgunients suggests that their- view of the role of learning in language acqirisition is based on a conception ofpotentially relevant learning processes that is limited to operant training paradigms (Skinner-. 1957) and to the classical conditioning of reinforcement value to the vocalization of “tiilhing birds” (Mowrer. 1950, 1952). However well prepared the human ncrvous system may be for t h e acquisition of language, at any point in its maturation, a conception of the acquisition process must give an account 01‘ the transmission of external information to the templates which the child uses in the production of speech. I t would

be a very considerable advantage if such an account also had some utility toward an understanding of the child’s capacity for reproduction of other kinds of external models than those which are provided in speech. T h e conception of imitative learning through representational templates. which has been outlined here i n some detail, would not be inconsistent with any of the phenomena that characterize a child’s acquisition of grammar, provided that the appropriate properties of structure and sequence are specified for the templates. Of course, the central place of auditory information in the imitative acquisition of language tends to show a crack in the veneer of the terminology that has been applied to the broader class of phenomena to which imitation belongs, since the term “observational learning” seems to carry the connotation of a process that occurs through the visual modality. The fact that language is generative, and is not merely a copy of external samples, can hardly be a persuasive argument against t h e view that children acquire grammatical structures by imitation. In speech a s in nonverbal behavior, absolute correspondence cannot be taken as the only criterion of imitation. The acquisition of language may engage different levels of imitation which range from phonetic stimulus reproduction to symbolic representation that is an abstracted construction on an external model. Some psychologists have recognized that generative constructions and hierarchical order are not unique to linguistic productions. There are similar structural features of behavior, and similar theoretical problems. to be encountered in children’s imitative play or in other kinds of serially integrated motor action (Lashley, 195 1 : Piaget, 195 1 ). Vygotsky made the same observation years ago in a lecture that only recently has been published (Vygotsky, 1967). T h e generative property of representational templates also can be seen. for example, i n the imitative learning of dancing. But it appears to be most powerful in the case of language, where only a limited amount of t h e required structuring of information can be provided by external models. One kind of testimony to the role of imitation in language acquisition can be found in a recent compendium of papers on children‘s acquisition of language, edited by Smith and Miller (1966).in which most of the authors do not seem to find it possible to talk about any aspect of speech without at least casual use of the term imitation. Fry ( 1966) obtained good evidence of the contribution of imitation to children’s acquisition of the phonological system for language. Analyses of the extended naturalistic observations which Brown and his co-workers have gathered on t h e development of children’s language suggest that children do imitate adult expansions of their initial utterances, and that they also show evidence of telegraphically reduced imitation even in their very first use of a given

construction (Brown & Bellugi, 1904: Brown & Fraser, 1964; Slobin, 1966, 1968). Ervin ( 1 964) concluded that there was no evidence for children’s acquisition of grammar by imitation, on the basis of her finding that their utterances were no closer to the adult grammar when they immediately fcllowed corresponding utterances of an adult than they were when they occurred spontaneously. What Ervin may have observed in the ‘?mitative” utterances of her young subjects, however, was a social facilitation or release of verbal behavior. rather than a linguistic interaction with a potential model to whom the children were directing their attention. Her subject3 usually selected just the last few words in an adult sentence as the basis for their imitative utterances. Mere fidelity in the repetition of an utterance would not seem to be an adequate index, in any case, of the imitative learning of the type of structures which presumably are required for the acquisition of grammar. A more realistic and flexible test might lie in observations of shifts in the child’s level of grammar, without focussing only on utterances which are exact copies, when the child is responding verbally to adult speech in more extended linguistic interactions. Fraser, Bellugi, and Brown ( 1963) reported an extremely interesting experiment that indicates some of the complexities of the imitative control of speech by grammatical structures. Their findings have since been essentially replicated by Turner m d Rommetveit ( 1967). They tested a variety of grammatical contrasts in their three-year-old subjects by plating each subject in each of three tasks. In an imitation task, the subject was asked simply to repeat individually each of two short sentences which were spoken by an adult and varied in only one syntactic feature. In a comprehension task, the adult spoke sentences which were equivalent to those used in the imitation task, and the subject was required only to point to each of two pictures in the order appropriate to the contrast in each pair of sentences. In a production task, the subject was required to produce the pair of sentences with each contrast. in t h e order appropriate to the pictures to which the adult pointed, after having heard the adult speak the two sentences. The procedures for the comprehension and production tasks were designed so that the adult’s utterances did not reveal the pictures with which they were to be associated. The children’s performance in the imitation task was superior to their performance in the comprehension task, which was in turn superior to their performance in the production task. I t can be seen that the imitation task did not require the children to use a grammatical conlr-ast with any reference or identifiable meaning. Accurate imitation conceivably could have rested even on an immediate reproduction of’ H perceptual-motor template rather than on a representational template for the proper syntactic distinction. Successfu 1 p e rf.3rma nc e in the more (1 e ti1 ;I n d i n g c om pre h e n si on task necessitated

a representational template that could function at least on a receptive basis to decode a grammatical contrast which had external referents. T h e criterion in the production task required that the grammatical contrast in a representational template be used not only to engage external referents, but also to control overt speech -a requirement at least as demanding as the requirement of behavioral fidelity to a template in a nonverbal imitative peiformance.

VI 1. Three Experiments’ Three experiments on children’s observational learning will be described here. The experiments concern themselves with what would apelf-criticism, sympathetic pear to be rather different kinds of phenomen behavior, and expressive movement in the use of the hand. But all of the experiments share an underlying conception of the affective and cognitive mechanisms which mediate their effects. I t is incidental to their history that two of the experiments use aversive control of the learning process, while the third is based on positive control. T h e experiments were designed to maximize their utility in uncovering the mechanisms of affective control over observational learning. T h e y have a s a common feature their employment of contingencies which are devised to produce an essentially Pavlovian conditioning of changes of affectivity to children’s cognitive representations of the observed behavior of others, under conditions in which the children’s overt reproductions of the behavior do not occur during observation. The overt behavior of the children is then subsequently used as an index of the affective value that has been coupled to their cognitive representations. However, the experiments also provide some ground for inferences about the role of cognitive representation itself in the learning process. I n particular, the third experiment attempts to exercise some control over conditions which might affect the child’s formation of acognitive template of the behavior that it has observed. Only one of the experiments which are described below produces behavior that has a strong imitative component in the sense that it shows a fairly high fidelity to the specific features of an external model. However, the effects which are obtained in the other experiments also contain some evidence of the intrinsic representational affective value of the behavior that the children reproduce. When a child’s behavior has some distinguishable components of structure or sequence. with which it can display

’ Ihe experimental work that is ireported in this section was supported in par-t hy Research G r a n t MH-0667 1 from the National Institutes 0 1 Health. United States Public Health Sei-vice.

its fidelity to a model, it is usually easier to discern that the behavior has acquired an intrinsic value of its own. But it can also sometimes be shown that even discrete acts of choice have acquired intrinsic value, when contingencies are designed so as to make it possible to infer the locus of affective control over the child’s behavior- particularly when the behavior is not instrumental to the control of external outcomes. Two of the experimental paradigms which are described focus on a discrete criteria1 act rather than on an expressive pattern of behavior. The intrinsic representational value of the act cannot therefore be apparent in any fidelity to the internal structure of the behavior of a model. T h e intrinsic value of the act instead can be inferred by comparing the effects of different experimental conditions which are arranged to show that the child’s performance of the act has some independence of external outcomes, and that it is controlled to some extent by the original temporal relationship between another person’s performance of the act and events which could be expected to produce a significant change of affectivity in the child. A. Sli

l-C‘RITICISM

An experimental study of the origin of self-criticism, which has been reported in detail elsewhere (Aronfreed, 19641, can be usefully re-examined here as an example of the techniques which may be employed to demonstrate that there can be intrinsic representational value in the child’s reproduction of a discrete element of a model’s behavior. Selfcriticism as a reaction to transgression is perhaps the most common instance of a type of imitation i n which a child reproduces components o f a model’s behavior that have accluired value through their previous conjunction with termination o f anxiety. Self-criticism reproduces verbal components of the punishment which the child has experienced from the model. When a child has experienced a sufficient frequency and intensity of punishment for a transgression, anxiety will become conditioned to the intrinsic behavioral and cognitive correlates of the transgression itself (Aronfreed. 1968b; Aronfreed Rr Reber, 1965). On subsequent occasions when the child commits the transgression, it will experience anticipatory anxiety for some duration of time before the actual occurrence of punishment. Certain components of the punishment may therefore acquire anxiety-reducing value because they function as signals which mark the end of the interval of anticipation. I t is not necessary for such components to occur at the termination of punishment. Provided that the punishment is not unusually prolonged or extremely aversive, components at any point within the course of a characteristically brief social punishment may ac-

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quire value for the reduction of the internalized anxiety that intervenes between transgression and onset of the punishment. Since the punishment that is used by socializing agents frequently includes verbal criticism of the child’s behavior, the child’s cognitive representation of the criticism may also acquire some anxiety-reducing value. And the child may then reproduce the verbalization of the criticism (covertly, and sometimes overtly) in order to exercise its own control over the anxiety that it experiences in response to later transgressions. The child’s self-criticism will now inherently induce a reinforcing change of affectivity, which already has been established through the contingencies in the original external behavior of a model, without the requirement that the child first emit overt behavior and produce reinforcing external consequences. The experiment that was designed to test this conception of the learning of self-criticism was conducted with nine- and ten-year-old girls as subjects. A female experimenter took the role of the adult agent of socialization and potential model. Each child engaged individually in a task that required her to make repeated guesses as to how many of four dolls were looking at her from behind a screen. There were ten distinct trials, and the child indicated her guess on each trial by pushing down an appropriate number of levers from among an array of four. The four levers were deployed on a panelled box that was ostensibly instrumented with expensive equipment. The instructions made it clear that the experimental agent was interested in whether the child pushed the levers in a “blue way” or a “red way,” and also that the child would be punished for using the levers in the “blue way” (except that reference to punishment was omitted in the control paradigm). There was no further specification of the nature of either the punished or nonpunished behavior. When the child had completed the operation of the levers on a nontransgression trial, the agent labelled the child’s behavior as “red” (“Uhhuh, y o u did ir the red way”). Correspondingly, the agent labelled the child’s behavior as “blue” when a transgression occurred in the course of operating one of the levers (“You did it the blue way”). Since the occurrence of “blue” behavior was arbitrarily defined, the child actually had no behavioral cues with which to identify a transgression. The occurrence of a transgression was externally signalled by a buzzer that sounded five times in an unpredictable sequence among the ten trials. Punishment consisted of sharp verbal disapproval ( “ N o ! ” )together with deprivation of candy that already had been given to the child. The buzzer and the punishment were initiated simultaneously, immediately upon the child’s operation of one of the levers, and also were terminated simultaneously. A period of roughly ten seconds was required for the agent to administer the various components of punishment and labelling of the child’s behavior,

while she walked to where the child was seated at the choice-box. removed candy, and finally turned off the buzzer. The critical difference between two of the experimental paradigms was a variation in the temporal position at which the agent verbalized the label ‘‘blue,’’ with respect to the parallel durations of the transgression signal and punishment. In one of the paradigms, the agent integrated the label into her behavior so that it was produced just at the termination of the transgression signal and punishment, in order to maximize its potential acquired anxiety-reducing value for the child. In the second paradigm. the label was verbalized at the very onset of signal and punishment, where the child’s anticipatory anxiety in response to the transgression could not yet have been fully elicited. There was also a third punishment paradigm, which was designed to examine the effects of the agent’s nurturance toward the child and of the consequent withdrawal of nurturance in the agent’s punishment. In the third paradigm only, the agent displayed much warmth toward the child, and gave the child repeated physical affection and approval, both during the initial instructions and when she labelled the child’s behavior as “red” on each nonpunishment training trial (“Good! You did it the red b t x q v ’ ’ ) . When a transgression occurred. the agent verbalized the label “blue” at the onset of buzzer and punishment (just as in the second paradigm). Finally, no punishment was used in a control paradigm in which the buzzer signalled the behavior that was to be labelled ‘‘blue’’ and the agent verbalized the label as the buzzer terminated.2 The children were given theii, first opportunity to verbalize the label “blue” overtly on two identical test trials which immediately followed all of the paradigms. On each of the two test trials, the buzzer signalled the occurrence of “blue” behavior, and t h e agent asked the question: “What happened this time?” This question was asked casually, while the agent obviously had suspended her earlier punitive role and seemed preoccupied with another activity. The children gave many different replies to the question. But there was one very sizeable and reliable difference among the replies in the frequencies with which children from the various paradigms used the label “blue” to describe their behavior. The great majority of the children who had heard the label verbalized by the agent at termination of their transgression signal and punishment showed a self-critical application of the label to theit own actions on both test trials (for example: “ I did it the blue way”). Among children from any one of the other ‘The numbers of children used in e;icIi of tlie four paradigms were: Label at termination of punishment-27; Label at onset o f piinialiiiient -74; Nurturance (with label at onset)--26: Control - 12.

three paradigms, only a small minority used the label “blue” in response to the question (on either test trial). When three additional groups of ten children each were trained in the label-at-termination punishment paradigm, in order to prepare them for a variety of extinction procedures which introduced additional test trials, almost all of them continued to use the label “blue” to describe their actions throughout the entire course of the test trials. None of the three attempted extinction procedures effectively curtailed the children’s self-critical applications of the label. The findings of this experiment indicate that the learning of self-criticism requires aversive control of the child’s imitative dispositions. The difference between the effects of the first two punishment paradigms, in which the label “blue” occurred respectively only at termination and only at onset of the child’s aversive experience, provides strong support for the view that the child reproduces verbal components of social punishment when they are embedded in external contingencies which permit them to acquire anxiety-reducing value. The critical temporal prerequisite of this acquired value, which is almost always present in naturalistic socialization, is a sufficiently long interval of anticipatory anxiety between the occurrence of transgression and a verbal component of punishment. It is theoretically entirely incidental that the label “blue” actually is placed at the termination of punishment in the paradigm which most successfully generates self-criticism. Provided that there is an interval during which the child can experience anticipatory anxiety, the verbal criticism of an agent may acquire value even when it is located at the onset of punishment. Grusec ( I 966) has reported an experiment that demonstrates precisely this point. Using an adaptation of the techniques which have been described here, she found that children would reproduce the verbal criticism of an experimental agent even though it had occurred at the onset of the agent‘s punitive reactions to their transgressions, under conditons which permitted ample time for the children to experience anticipatory anxiety between transgression and criticism. Unfortunately, Grusec mistakenly interpreted the fact that the external criticism did not coincide with termination of punishment as evidence that the learning of self-criticism was not controlled by anxiety-reduction. The conditions which most effectively induced the children’s verbalized application of a model’s criticism to their own behavior did not include the opportunity to observe the control of external outcomes by the model’s verbalization. Nor did they include the children’s direct experience of external reinforcing consequences of their own verbalization. I t therefore seems apparent, despite the absence of any clear evidence of internal structural fidelity to a model. that the children’s behavioral reproduction of the label “blue” must have acquired some intrinsic representational

value for them. At t h e same time, the failure of the control paradigm to produce much self-criticism makes i t obvious that whatever advantage may have accrued to the children‘s cognitive representation of the label “blue” during training, as a result of its mere conjunction with termination of a buzzer, was not enough to give overt behavioral expression to the label if the children were not also exposed to punishment. There was also other evidence which indicated that the children’s representations of the model’s verbalization required substantial affective couplings in order to flow into the children’s behavior. After the first two test trials, the children were given two further trials which were designed to test their application of the label “red” to their behavior, in response to the agent’s inquiries when a transgression had not occurred. Only a small number of the children from ail)’ of the paradigms overtly reproduced the “red” label - a finding which indicated that the children from the label-attermination punishment par;iciigm had not simply acquired a generalized disposition to reproduce the agent’s verbalization. Although the children must have had a cognitive representation of both the “blue” and the “red” labels, and particularly of the external correlates or consequences of the labels, there was a considerable difet-ence between the two labels in the children’s dispositions toward verbalization. This difference seemed to reflect the different contingencie\ that originally had controlled the nature and extent of the changes of afectivity which were associated with the labels. I t is interesting that the label “red” was not frequently reproduced even by those children who heard it applied to their behavior in a nurturant context of physical afTcction and verbal approval. However, the agent’s verbalization of the Iahel was not timed so that it was well correlated with the onset of the rewxrding consequences of “red” behavior. The absence o f the buzzer. at the point where the child had just completed her operation of the levers. w a s actually the first informational signal of reward. Moreover, it may hiive been difficult to establish the positive affective properties of the label “red” in a learning situation in which the child was continually confrontcd with the prospect of an unpredictable punish menl. I t is also a finding of some interest that the nurturance of the agent did not facilitate the children’s repimiuclion of t h e critical label that she used as a component of her punishment. when the label was used i n a position (onset of punishment) at which their anticipatory anxiety could not yet have reached any substantial intensity. Of course. the fact that children did reproduce the criticism of an entirely non-nurturant model. when the critical label occurred at termination of punishment, clearly demonstrates that self-criticism cannot be regarded ;IS a form of imitation which extends the positive control that m a y he exercised over children’s behavior by

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their observation of nurturant or affectionate models (cf. Sears et al., 1957, Ch. 10). T h e results of other experiments which have been based on this experiment do suggest that a model’s nurturance toward a child can facilitate the child’s reproduction of the model’s verbal criticism (Grusec, 1966; Mischel & Grusec, 1966). However, these results do not imply that the affective control of the self-criticism can somehow be generalized from the child’s pleasurable experience with the model. They indicate rather that the effects of nurturance can enter into the contingencies of aversive learning which establish the anxiety-reducing value of self-criticism. The nurturance of a socializing agent might well enhance a child’s attention and sensitivity to the agent’s punishment, since the contrast of withdrawal of nurturance would increase the salience of the punishment and its effectiveness in the elicitation of anxiety. But it is hardly plausible that the positive affective value of nurturance would extend to the agent’s punitive behavior. B. SYMPATHETIC BEHAVIOR

The concept of sympathy has been used with more than one meaning. Some psychologists have used the concept to designate a generalized disposition to respond empathically or vicariously to the experience of others (Allport, 1954; Asch, 1952, pp. 171- 172; Heider, 1958, pp. 277-282; McDougall, 1908, pp. 150- 179). However, it is when sympathy is used to refer to a behavioral disposition toward relief of another person’s distress that it becomes most relevant to the phenomena of observational learning. An act cannot be identified as sympathetic in this sense, of course, merely because it has the effect of eliminating the distress of another person (for example, it may be motivated by the actor’s own direct experience of the same source of distress). The truly sympathetic component of an action is controlled by the actor’s empathic or vicarious response to the actual or anticipated distress of the other person. Although the elicitation of sympathetic behavior requires the capacity for empathic or vicarious distress, a child may sometimes experience directly reinforcing consequences of its overt sympathetic actions, with the result that the actions also come under the control of the child’s expectation of direct social reward or reciprocity from others. The naturalistic observations which lsaacs ( 1 933) and Murphy (1937) made some years ago clearly suggested that children’s sympathetic behavior often anticipated social approval or the reciprocal benefits of cooperation. However, a sympathetic act may also be altruistic, to the extent that its expected outcome will be only empathically or vicariously experienced through the child’s perception (or cognitive representation) of either the reduction or

avoidance of another person’s distress. An altruistic component of sympathetic behavior may be present in experiments which Lenrow ( 1 96s) and Rosenhan and White ( 1 967) have conducted as demonstrations of the conditions under which children’s sympathetic actions may be influenced by their observation of the corresponding actions of others and by their experience as recipients of the actions. Altruism also may have made some contribution to recent demonstrations of the types of social interaction which are effective in eliciting sympathetic reactions among adults (Berkowitz & Friedman, 1967; Buss, 1966; Goranson & Berkowitz, 1966; Schopler & Bateson. 196.5). But none of these demonstrations is directly addressed to the mechanisms of learning through which socialization originally induces sympathetic dispositions. It is interesting to note that many experiments which demonstrate that animals will act to avoid or reduce distress to a peer cannot even be taken as evidence of sympathetic dispositions, since their procedures and findings suggest that the animals may have been acting to avoid stimulation (either distress cues or correlated noxious events) which they experienced as directly aversive to themselves (Horel, Treichler. Rr Meyer, 1963; Lavery & Foley, 1963; Masserman, Wechkin, & Terris. 1964; Miller, Banks, & Ogawa, 1963; Miller, Caul, & Mirsky, 1967; Rice & Gainer, 1962). The socialization of sympathetic behavior requires first that the child acquire empathic or vicarious affective responses to cues of another person’s distressful experience, a n d secondly that it acquire overt actions which are instrumental to reduction of the other person’s distress. A recent monograph by the author ( Aronfreed, 1968a) gives a more detailed analysis of the different forms of learning through which these criteria1 acquisitions may be established. We are concerned here primarily with the child’s acquisition of sympathetic behavioral dispositions through observational learning. But it will also be necessary to give some attention to the social conditioning of the empathic or vicarious sensitivities which are the affective base of sympathy. The opportunity for observational learning of sympathetic behavior would occur whenever the child observes another person’s sympathetic actions in the context of its own experience of a potentially reinforcing reduction of distress, regardless of whether the distress-reduction is directly or only empathically experienced. The most powerful paradigm for this form of observational learning would be the one in which the child itself is the recipient of Sympathetic actions from another person. As a result of the child’s common experience of relief of distress through the actions of nurturant socializing agents who serve as potential models, the affective value of reduction of distress would become coupled to the child’s cognitive representations of its models’ sympathetic behavior.

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When the child responds empathically to the perceived distress of another person (because of earlier social conditioning),it can then use sympathetic behavioral reproductions of its acquired representations in order to reduce its own empathic distress. Since potentially reinforcing changes of affectivity already have been attached to the child’s cognitive representations of the sympathetic actions (and of their consequences for others), its reproduction of sympathetic behavior under these conditions will have some intrinsic value that is not dependent on directly observable consequences. However, it will also often be true that the child’s sympathetic behavior is further reinforced by the empathic reduction of distress that follows from direct observation of the effects of the behavior on others. This conception of the observational learning of sympathetic behavior was tested in an experiment that was designed by the author with the collaboration of Vivian Paskal (Aronfreed & Paskal, 1 966).:i The experiment was carried out with seven- and eight-year-old girls as subjects. Five distinct groups were exposed to different experimental sequences, each of which consisted of three immediately successive phases of socialization. During each phase, a child was individually engaged in a task which required that she classify each of twelve small toy replicas of real objects. in accordance with whether it was most appropriate for a house, a dog, or a school. The female socializing agent held each t o y separately in view on discrete classification trials, and the toys were changed between phases. The child was instructed to indicate her classifications by pushing down one of three levers o n a choice-box. The categories of classification were labelled by the words which appeared on panels above their respective levers (house, d o g , sc.hool). The middle lever was chosen very infrequently or not at all for the purpose of classification, since it represented the category of “dog” and the toys were selected so as to make its use inappropriate. Because choices of the middle lever were not instrumental to the task of classification. it was possible to use them as an index of Sympathetic behavior during the third or test phase of all of the five sequences. The first of t h e five experimental sequences was the prototype of t h e requirements for both empathic conditioning and observational learning in the child’s acquisition of sympathetic behavior. Each of the remaining four sequences introduced disruptions of certain crucial contingencies within one of the three phases of socialization. The first phase of the basic first sequence was a paradigm of the original acquisition process for the establishment of a child’s empathic dispositions. I t was designed to condi,“Thesuccess ofthis experiment was in gi’cat incasure iittrihut;hle to Vivian kiskiil’s intellectual warmth a n d enthusiawi for the problems that i I posecl. H e r untimely death. in JanLiary of 1969. ai-i-esteci plans foi- ;I co-wtithored separate empirical report o f the complete d e tails of the experiment.

tion the child’s distress to the observable affective cues of another person’s distressful experience, through the medium of a temporal contiguity between the occurrence of the cues and the child’s own direct experience of aversive stimulation. The child and the experimental agent sat opposite one another. Both wore earphones which were attached to the choice-box on the pretext of a requirement ut surveillance of the noise from the apparatus within the box. The child was told that she would hear noise occasionally, and that the agent’s earphones would transmit an even louder noise. During the intertrial intervals which followed six of the child’s choices among the twelve classification trials (well aftet- the child had pushed down a lever), the child heard a highly aversive loud noise that lasted for seven seconds. The occurrence of the noise across trials was unpredictable and not contingent on the child’s choices. Three seconds before the noise began, the agent lowered her head in her hands as a distress cue (as though the noise wei-e already audible in her own earphones). Her distress cue then continued until the noise that the child heard had terminated. The cue was theretore visible for a total duration of ten seconds. The second phase of socialization in the basic first sequence was designed to maximize the distress-reducing affective value that could become intrinsically attached to the child’s cognitive representation of the act-outcome contingencies which were observable in the agent’s sympathetic actions toward her. The child continued to wear her earphones. But the agent no longer wore earphones (and. of course, showed no sign of distress). She sat beside the child and used a second choice-box to indicate her own classification of each toy aftet- the child had chosen a classification. She also told the child t h a t she might be able to use the second box to turn off the noise that the child would continue t o hear occasionally through the earphones. After the child had used one of the levers to classify each toy, the agent poised her hand for two or three seconds above the levers on her choice-box. a s though she were considering her own classification. The two outer levers in the array of three were designated “house” and “school,” and were clearly the only correct ones to use for almost all of the toys. On six of the twelve classification trials. the agent did choose one of these levers. On t h e remaining six trials, however, the child began at this point to hew the unpredictable aversive noise through her earphones. The noise had the same high magnitude that it had during the first phase. I t was terminated after ;I duration of three seconds, when the agent quickly pushed down the middle lever on her choice-box. As the agent made this choice, she told the child that she was pushing the middle lever in order to turn off the noise. I t was apparent that she chose to reduce the child’s distress and thereby gave up the opportunity to make a correct classification.

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The third phase of the basic first sequence was designed to test whether the child had acquired a disposition to reproduce the sympathetic action that the agent had used, during the second phase, to turn off the noise and thus reduce the child’s distress. The child was now given a number of opportunities to use the same action to reduce her own empathic distress, in response to the distress cues from another child. Contingencies were arranged so that the child’s choice of a sympathetic action would not only be empathically motivated by the observed distress cues, but would also be empathically reinforced by the outcome of elimination of the cues. Another girl was introduced as a new subject at the beginning of the third phase. The new girl actually already had been a subject. And she had been subsequently trained to emit distress cues, upon covert signals from the earphones, at critical points during the test of another subject’s acquired sympathetic dispositions. This more or less innocent “dummy’‘ wore earphones, but now the subject did not. The subject could therefore no longer be directly exposed to the aversive noise. The earlier role of the agent was given to the subject. After the “dummy” had classified each toy by using one of the levers on the first choice-box, the subject used the levers on the second choice-box to classify the same toy. The agent was merely an observer who sat behind the subject. “Dummy” and subject made their successive choices uneventfully on six of the twelve classification trials. But at the point where the subject was about to make her choice on the remaining six trials, the “dummy” placed her head in her hands (in response to a low signal from her earphones)- thus showing the same distress cue that the agent had shown during the first phase of socialization. If the subject reacted to this distress cue by making the non-taskoriented sympathetic choice of the middle lever- the same choice that the agent previously had used to relieve the subject’s own distress (during the second phase)-then the “dummy” would immediately terminate the cue by raising her head (in response to offset of the signal in her earphones). However, if the subject made t h e task-oriented nonsympathetic choice of one of the two outer levers, the “dummy” did not terminate her distress cue until five seconds later, so that the empathically mediated reinforcement of such a choice would be insignificant. The other four experimental sequences represented a series of alterations of the basic contingencies within the three phases of socialization for the first sequence. They were constructed to allow certain inferences about the affective and cognitive mechanisms of the expected acquisition of sympathetic dispositions by children who were exposed to the first sequence. The second sequence varied from the first only during the initial phase of socialization, where the children experienced the same frequencies of occurrence of both the aversive noise and the distress cue

from the agent, but without the temporal contiguity that was required fotconditioning of empathic distress. The noise occurred during the same six intertrial intervals as it did during the first sequence. But the agent emitted her distress cue only during the noiseless intervals which followed the remaining six trials. The third sequence also closely replicated the first. But it was designed to minimize the potential alTective value of distress-reduction that could be coupled to the child’s cognitive representation of the agent‘s sympathetic actions, so that the child would acquire little disposition to t-eproduce the actions under subsequent conditions of empathic distress. Accordingly, during the second phase of socialization, the noise that the child heard in her earphones w;14reduced to a very mild intensity (in contrast to the second phase of the first sequence, in which the children continued to hear a highly avet-sivc noise). The fourth and fifth sequences differed from the first o n l y during the third (test) phase, where they introduced two levels of reduction of the external social cues which had been used to elicit and reinforce the sympathetic choices of subjects in the first sequence. During the test phase of the fourth sequence, t h e “dummy” wore earphones but emitted no distress cues. During the test phase of the fifth sequence, the “dummy” did not even wear earphones.‘ During the first two phases of a11 sequences, the children were uniformly task-oriented in their classification of the toys. T h e y typically chose the middle lever, for clas\ification in the “dog“ category, only once or twice among the twelve trials in either phase. A striking difference emerged, however. during the third (test) phase, when the children from the basic first sequence suddenly showed a sharp preference for the middle lever, and thus lost many opportunities to make correct classifications. Half of these children made the 5ympathetic choice of the middle lever on six or more of the test trials (almost invariably including all of the six trials on which the “dummy” showed the distress cue). Virtually all of t h e remaining children from the first sequence chose the middle lever four or five times during the test phase. Hi11 children from all of t h e other four sequences continued to show ;I strong task-orientation during the test for sympathetic behavior-. Some ot them showed a tendency toward choices of the middle lever in I-espoiiw to the “dummy’s” distress cue (particularly those from the fourth sequence). ‘The frequency distributions of their choices during the test were quite similar, however, to the distributions of their choices for the lint two phases. There was a large and highly reliable difference between the effect of the first sequence and the T h e numbers of children used i n e a c h (it’ the socialiiation sequences were: first sequence -26: second sequence-71: third s e q u e n c e - 2 1 : fourth sequence- 17: fifth sequence- 17.

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effect of each of the other sequences, when t h e five experimental groups were compared with respect to individual children’s shifts in frequency of choice of the middle lever between the first two phases and the test phase. The differences among the effects of the five sequential paradigms provide firm ground for inferences about the mechanisms of observational learning in the acquisition of dispositions toward sympathetic behavior. They also confirm the contribution that is made by empathic conditioning. The requirement of empathic distress in the establishment of sympathetic dispositions can be seen in the difference between the effects of the first and second sequences. During the first phase of the socialization paradigm, children from the second sequence observed the agent’s distress cue at times which did not coincide with their direct experience of the highly distressful noise from their own earphones. I t was therefore expected that their experience of distress would not become empathically attached to the cue of the agent’s distress. And these children did show very little evidence of sympathetic behavior when the same cue was emitted by the “dummy” during the test phase. ‘They seldom chose the middle lever in order to relieve another child’s distress. even though this action was readily available to them, and even though they previously had observed the agent’s repeated use of the same action to relieve their own distress (during the second phase of socialization). I t was apparent that sheer information about the “dummy‘s” distressful experience was not suficient to elicit their reproduction of this sympathetic action. What appeared to have been missing was an empathic reinstatement of the affective experience under which the action, when observed in the agent’s behavior, originally had acquired value for them. The difference between children from the first and third experimental sequences, in their dispositions toward sympathetic behavior. is the most interesting one for our purposes here. It is clear that the sympathetic actions of children from the first sequence cannot be attributed merely to a generalized disposition to be influenced by the previously observed choices of an adult, even if we were to suppose that their choices of the middle lever were somehow further constrained by a requirement of empathic distress. The children in both the first and third sequences were exposed, during the first phase of socialization, to the paradigm that was designed to condition their empathic experience of distress to a specific distress cue from another person. The two groups therefore should have been equally responsive to this same cue when it was later emitted by the dummy during the test. The relatively unsympathetic behavior of children in the third sequence also revealed that the more sympathetic actions of children in the first sequence could not be explained simply by their earlier opportunity to

observe the corresponding actions of the agent, or by their knowledge of how these actions could be used to relieve the apparent distress of the “dummy.” During the second phase of socialization, both groups had access to the information that was transmitted during their observation of the actions with which the agent effectively relieved their own distress. Consequently, both groups should have been able to form the cognitive representations which were required for observational learning of the sympathetic act-outcome contingency. The two sequences differed in only one respect. The agent’s sympathetic actions during the second phase terminated a noise that had been diminished to only a mild intensity for children in the third sequence; whereas they terminated a noise that continued to be highly aversive for children in the first sequence. I t would appear that this difference in experience gave different amounts of acquired intrinsic distress-reducing value to an action which the children would later be able to reproduce when they felt empathic distress in response to the “dummy’s” distress cues. Their actual behavioral t-eproductions of the action were determined by the respective magnitudes of the changes of affectivity which they had experienced earlier as recipients of the same action. During the first and second phases of any experimental sequence, the children had no opportunity to relieve their own distress with overt actions. Their later overt reproduction of the sympathetic actions which the agent had shown during the second phase must therefore have been initiated under the control of an affective value that had become directly coupled to their cognitive representation of the actions (and of the consequences of the actions). Children from the first sequence experienced the relief of intense distress in cor1,junction with their observation of the agent ’ s sympathetic behavior . The i r own potential I y sympathetic actions would, accordingly, have acquired substantial inherent distress-reducing value as representations of an earliet- external sample of behavior. Comparisons of the contingencies of socialization in the different sequences can be used to infer that the sympathetic actions of children from the first sequence retained an intrinsic reptesentational value throughout the test phase, and that their actions were nut primarily controlled by the observable and empathically reinforcing external outcome of termination of the “dummy’s” distress cue. Children from the third sequence also could have produced this empathically reinforcing outcome. But they seldom attempted to terminate the “dummy’s” distress by choosing the middle lever, even though their conciitioning in the first phase would have provided the empathic motivation to do so, and even though their opportunity to observe the agent’s behavior during the second phase would have provided the necessary information about the outcome of such a choice.

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Because the agent’s sympathetic actions had terminated only a mild noise for these children, their cognitive representations of the actions did not acquire the same intrinsic value for reduction of distress as did the representations of children from the first sequence. Although the termination of the “dummy’s” observable distress cue during the test was apparently not the primary source of reinforcement of the sympathetic dispositions which children from the first sequence had acquired, as a result of their empathic conditioning and observational learning during the first two phases of their experience, it was quite clear that the presence of the distress cue was required in order to elicit the behavioral expression of these dispositions. When the “dummy” showed no evidence of distress, during the test phase of the fourth and fifth sequences, the children did not show marked increments in their frequency of choice of the middle lever, even though they were identical to children from the first sequence in their previous exposure to the contingencies for empathic conditioning and in their opportunity for observational learning The role of the external distress cue is also nicely confirmed by the pat. tern of test trials on which children from the first sequence chose the mid. dle lever. They confined the increments in the frequency of their use of the middle lever almost entirely to the six test trials on which the “dum my” emitted the distress cue. This finding shows once again that the be. havioral product of the children’s observational learning was under tht affective control of their empathic experience of distress. An interesting point of evidence of the control of cognitive representa. tion over the children’s sympathetic behavior appeared during the test phase of the fourth experimental sequence, when the children showed some increase in the frequency of their choice of the middle lever, despite the absence of a distress cue from the “dummy.” Even though they continued to maintain a relatively strong task-orientation, their behavior during the test was closer to that of children from the first sequence than was the behavior of children from any of the other sequences. For example, they chose the middle lever significantly more often than did the children from the fifth sequence (in which the “dummy” wore no earphones). Since their choices were independent of an observed distress cue from the “dummy,” it is reasonable to assume that the choices were determined in part by the affective value that had become attached to their cognitive representation of the distress-reducing (or distress-avoiding) outcomes of their actions for another child who was wearing the earphones. Somewhat more direct evidence of the role of cognitive representation in the experimental effects appeared in the children’s reports during a verbal inquiry that closed the session for many subjects. Admission of awareness of the contingency between choice of the middle lever and re-

lief of the dummy’s distress wits ;I reliable predictor of sympathetic behavior among children in the first sequence. But it was not a reliable predictor among children in the second or third sequences. C. EXPKI-SSIVI MOVEMENT

This third experiment represents an attempt to introduce some externally controlled components of children’s affectivity into the intrinsic value of a model’s expressive behavior. I t also attempts to vary conditions which would determine the children’s opportunity for anticipatory representational rehearsal of the model’s behavior. Although the experiment is an exploration of techniques which are somewhat different from those which were employed earlier, its results are sufficiently interesting to examine here. Boys and girls from the first and second grades are the subjects for the experiment. They are equally distributed by sex and grade within each of the five experimental paradigms which are described below. A female adult agent conducts the experimental procedure and serves as the potential model for the children’s imitative behavior. Each child is engaged in the task of classification of a large number of small toy replicas of real objects, one at a time, with respect to whether they are most appropriate for ”home” or “school.” Most of the toys represent objects which might be placed with some justification in either category. The child receives verbal instructions (from the agent) which specify that it may select toys in any order from a large supply in a tray directly in front of it. Well behind the tray are two transparent plastic collection boxes. Each box sits just in front of a large painted picture on a vertical mounting. One picture portrays a house and the other a school. Each picture rises twelve inches above the top of its respective collection box, and the vertical edges of the picture have a series of markers at oneinch gradations. The child is instructed to pick up each toy, to decide on its classification, and to then place it o n the table directly in front of the appropriate box. The agent explains to the child that, after three toys have been classified in this way, she will show the child where the toys really belong by placing each toy inside its correct box. The child will then classify the next three toys, and the same procedure will be repeated. Since there are forty-eight toys in all, the task actually includes sixteen threetrial sequences on which the child and the agent alternate in classification of the toys. Before the task itself begins, the agent spends a certain amount of time in the establishment of a nurturant and affectionate role for herself. She displays a great deal of warmth Lind interest toward the child, engages the child in conversation that gives her frequent opportunities to express ver-

298

Justin Aronjreed

bal approval, and begins the task only after the child is thoroughly at ease. When the task begins, the agent sits side-by-side with the child-close enough to produce some occasional body contact -and maintains one arm around the child’s shoulder (in a lightly hugging position) during the instructions. When the instructions have been completed, the agent raises her arm from the child’s shoulder and rests it over the back of the child’s chair, in preparation for the physical affection that is to be given in most of the experimental paradigms. The basic procedure during the task itself can best be described by reference to Paradigm One, which is designed to maximize the child’s POtential imitative behavior. As soon as the child has completed a sequence of classification of three toys, the agent activates a small light that is mounted between the two collection boxes. Simultaneously, the agent casually states: “There’s the light.” After an empty interval of six seconds, the agent then begins her classification of the toys. On eight of the sixteen sequences, the agent treats the child’s classifications as predominantly correct by placing two of the toys (the first and third that she picks up) inside the boxes in front of which they have been put by the child. The remaining (second) toy is placed in the opposite box. On the remaining eight sequences, the agent treats the child’s classifications as predominantly incorrect by placing the first and third toys inside the boxes opposite to those in front of which they have been placed. Correct and incorrect sequences are varied in an unpredictable order over the sixteen sequences. When the agent places the toys on a correct sequence, she repeatedly uses certain expressive movements, for all three of the toys, including the single toy that has been ostensibly classified incorrectly by the child (that is, the movements are associated with the child’s attainment of two out of three correct classifications on the sequence as a whole). The agent lifts the toy to a height of twelve inches above the top of the box in which she will place it, pauses for two seconds, and then drops the toy into the box with a sharp flaring motion of her hand. As the agent releases the last of the three toys, she simultaneously initiates a sequential compound reward of physical affection. verbal approval, and dispensation of candy. She drops her arm from the back of the child’s chair to its shoulder, and begins a gentle hugging-squeezing movement. At the same time, she says: “Good for J O N ! ” (or “Very good!”)--“yorr g o t most of them right!” And she continues without a pause: “I’llput a Tootsie Roll in yorir box.” With this last statement, she takes a Tootsie Roll from a supply that is available in a small container, and places it in an identical container that is close to the child. As t h e agent completes these actions, she removes her arm from the child, turns off the light, and initiates the child’s classification of the

next sequence of three toys. I n contrast, when the agent places the toys on an incorrect sequence, she simply places each of the toys in turn into its appropriate box by setting it in with her hand over the edge of the box (in a more or less ordinary fashion). After she has placed the last toy. she turns off the light without comment. The procedure of Paradigm One is designed to couple positive affectivity to the child’s cognitive representation of the agent’s expressive movements. T h e agent’s movements are the child’s first signal of the correctness of its classification of a set of three toys, and are then followed by concurrent physical affection, verbal approval, and candy for the child. The use of a light to signal the agent‘s imminent classification of toys on each sequence is designed to elicit the child’s anticipatory representational rehearsal of the agent’s movements, at a point when it is still uncertain as to whether or not the movements will occur. The interval between the onset of the light and the agent’s initiation of her classification of the toys is designed to provide the time in which the child’s anticipatory representation of the movements can be rehearsed and consolidated. The procedure for Paradigm .l’wo is essentially the same as that for Paradigm One. But there is a reversal of the relationship of the agent’s expressive movements to the correctness and reward of the child’s classification. In Paradigm Two, the agent uses her expressive movements in placing the toys on incorrecf sequences, and conversely places the toys in the ordinary way on the correct sequences. This reversal is designed, of course, to remove the contingencies which would be required to couple positive affectivity to the child’s cognitive representation of the movements, and to produce contingencies which might even give the child’s representation of the movements the aversive affective value of the frustration that would be associated with an incorrect and unrewarded performance. Paradigm Three is also identical to Paradigm One, except that there is no interval between the onset of the signal light and the agent’s initiation of her classification of the toys. The agent begins her classification of the toys as soon a s she turns on the light (for both correct and incorrect sequences). This procedure eliminates the child’s opportunity to engage in anticipatory representational rehearsal of the agent’s expressive movements. From the point at which the child can begin to anticipate the agent’s classifications, very little time elapses before the actual occurrence or absence of the movements is apparent in the agent’s placements of the toys. Paradigm Four is likewise identical to the basic Paradigm One. But it omits the compound reward for correct classification as a source of positive affectivity. Consequently, o n l y the affective value of information that

300

J u s t i n Aronfrred

indicates correctness can be coupled to the child‘s cognitive representation of the agent’s expressive movements. Finally, Paradigm Five varies the procedure of Paradigm One only by omitting the light on incorrect sequences. The interval that precedes the agent’s classification of each three toys, following the child’s classification, still remains for either correct or incorrect sequences. But the light marks the onset of the interval only in the case of correct sequences. This procedure is designed to make the light the first informational signal of correctness of classification and subsequent reward -in contrast to Paradigm One, where the first informational signal is the agent’s expressive movement in beginning the classification of the toys.” A common test for spontaneous imitation is introduced immediately following the completion of all of the training paradigms. The agent asks the subject to be her “helper” and to take her place for another child who is to be brought into the room. It is explained to the subject that the other child will now classify toys by placing them in front of the appropriate boxes, and that the subject will then indicate the correct classification of each toy by placing it inside one of the boxes (the same role that the agent had previously). Following this instruction, the agent takes the subject to a far corner of the room, behind a nest of room-divider screens, and gives the subject a book to read. Then the agent brings another child to the room, and gives the new child the basic task instructions, including the information that another child (the agent’s “helper”) will indicate the correct classification of toys by placing them inside the boxes. after the new child has placed the toys in front of the boxes which it considers appropriate. The new child, who actually has the role of a n innocent “dummy,” is always of the same sex as the subject and from a grade just below the subject’s grade. Thirty new toys are made available in the tray, and all of the other experimental materials are reset to their original state. The primary subject is now introduced to the ”dummy,” and both are seated side-byside in front of the experimental materials. The agent sits at another table just to the right and slightly behind the two children. Each time that the “dummy” has classified three toys in sequence. the agent activates the light, and the subject t h e n classifies the same three toys by placing them inside of the boxes (whichever boxes the subject considers to be correct). This procedure continues recursively until the thirty toys are exhausted by ten three-trial sequences. The primary observations of the test session are found in the extent of the subject’s imitative reproduction of components of the agent’s earlier expressive movements in placing toys within t h e boxes. The agent makes T h e numbers of children used in each 01‘ the five p;u.adigms wei-e: Paradigm One- 24; ParadigmTwo- I ? ; Pnnidigm-rhree- 12: Par;digm Four- I ? : P a r a d y m Five- 12.

these observations according to ;I very simple scheme. She notes the readily identifiable components of the pause and flare of the hand, and also records the height to which the child lifts each toy before dropping it into the box. The judgement of the height can be made quite easily, since the movement of the child’s hand over either box is displayed against the background of the large pictures o n which the one-inch gradations are marked. Before examining these observations in detail, however, certain more general features of the children’s behavior are worth noting. During the training paradigms. all o f the children are more or less entranced by the expressive movements of the agent’s hand, and give their close attention to the movemenls each time that the agent uses them. During the test session, it is relatively unusual for any subject to treat more than one of the “dummy’s” classifications as being incorrect within a given sequence of three trials. Virtually all of the children apparently regard the “dummy’s” classifications of the toys as being predominantly correct on the great majority of the ten three-trial sequences. Accordingly, any differential distribution of ;I subject’s imitative behavior between the “dummy’s” correct a n d incorrect sequences (as now defined by the subject) is a negligible factor in the results. The pause and flare components are always linked in the children‘s imitative behavior. They can therefore be treated as a single u n i t . I t is often true, however, that the pause-flare components are visihle when a subject merely drops a toy within one of the boxes, without a n y discernible lifting of the toy above the level of the top of the box. On the other hand, lifting of the toy never occurs without the combined pause-fare components. Table I shows, for each individual subject from each of the five treatment paradigms, the distribution o f the occurrence and extent of fidelity of imitation across the thirty clwssilication trials of the test situation. Since the boys and girls who are drawn from a n y single paradigm give essentially the same patterns of behavior, t h e y are shown without distinction by sex. in order to simplify the presentation in the table. Casual inspection of the density of the components atid degrees of fidelity of imitation reveals some interesting differences among subjects drawn from certain of the training paradigms. An initial rough distinction can be seen in the number of subjects who show no evidence of imitation across the entire thirty test trials. For example, only two o f the twenty-four subjects in the basic Paradigm One show no imitation at all. Hut more than half of the subjects in Paradigm T w o show no imitation. A third of the subjects in both Paradigms Three and Four also s h o ~n,o evidence of imitation. Paradigm Five is the only one that is comparable t o Paradigm One in the relatively low frequency of subjects who show 110 imit,‘I t‘ton. There are a number of ways i n which more formal analyses can be

TABLE I OCCURRENCE A N D FIDELITY OF IMITATION: INDIVIDUAL SUBJECTS FROM EACHOF FIVEEXPERIMENTAL PARADIGMS Frequency of imitation across thirty test trials Paradigm and subject

Paradigm One (N=24) Subject I 2 3 4 5

6 7

8 9 10 I1 12 13

NO imitation

30 30 26 25 24 23 22 21 21

16

17

10

IN 19

8

I

4 5

6 7 8 9 10 I1 I2

4 I

I 2

I

I

-7

I

7

3 4

3

3

2 1

2

1

2

7

5

6 7 27

1

3

1

I I

2

2 2

1

1

2

2 I 1

1 1 3 1

I I

4

-7

2 13

I

3

9

2

3

8 5 1 2

3

1

5 5

2 6

1 7

1 1

1

1

I 2

1 1

2

8 2

2 2 3

1 1

2

II 9

2 5

2

1 7 7

4

2

2 4 1 3 4 1

2

I 2

4 4

3

3

I

1

2 9 2 5 5

8 4

I

8

14

I6

5

I I

II+

1 2 1

12

30 30 30 30 30 30 30 18

Lifting with pause-flat-e: Height of lift (inches) 3 4 5 6 7 8 9 I0

7

I9

IS

2 3

Pause-flare components only

18 17

14 15 16

20 21 22 23 24 Paradigm Two (N=12) Subject

imitation

2

2 1

I 2 3 2 3

1

9

2 3

9

I 1 2 7 3

2 1 6

3

1

1

3

Frequency o f imitation across thirty test trials Paradigm and subject

N0 imitation

I mi tat ion

P~ru\e-flalc comporlcnt\ 0111\

Paradigm Three (N=12) Subject I

3 4 5

6 7

30 29 29 27

I

6

2 3 2 1

4

6

15 14 13

17

I1

17

9

4

I

30 30 30 30 26 23

5

6 7 8

9 10 11 12 Paradigm Five (N=l?) Subject

I 2 3

I 2

3

1

7

I

1

5

1

13

I 9

7 7 4

2

1 3

2

1

I1 I2

1

6 6

9

7 8

1

14

10

6

2

8

30 27 23 20 16 14 10 7 I

4 5

II+

30 30 30

8 9 I0 II 12 Paradigm Four ( N = 12) Subject 2 3 4

2

I

Lifting with pause-flare: Height o f lift (inches) 3 4 5 6 7 8 9 I0

1

I

I 9 2 6 1 2 8 3 5 6 3 1 5 3 2 7 1

5

1 6 30

3

7 I0 I0 1h I I 2

2 7

4 5 2 2 2 2 1 2 3 8 1 2 4 8 9 4 3 9 1 9 4

19

1

10

5

12 I1

304

J u s f i n A ronfrrrd

made of the data in Table 1. One useful way to look at the data is to take the occurrence of any degree of lifting of a toy (which always includes the pause-flare components) as a criterion of imitative behavior. This is a criterion of higher fidelity than the occurrence of the pause-flare components alone. Each subject can be given a score that represents the frequency with which he or she meets this criterion in the course of the thirty trials. When the subjects from Paradigm One and Paradigm Two are compared with respect to the frequencies with which they show any imitative lifting behavior, by application of the Mann-Whitney test to the relative ranks of their frequencies, the obviously greater amount of imitation among subjects from Paradigm One proves to be highly reliable (pc.005).This difference strongly confirms the expectation that the context of correct performance and multiple reward, in which the agent’s expressive movements occur as a signal in Paradigm One, will attach positive affectivity to the child’s cognitive representation of the movements and corresponding intrinsic reinforcement value t o its behavioral reproduction of the movements. From the point of view of their association with incorrect performance and lack of reward, it is surprising that the agent’s expressive movements are reproduced at all by any of the children from Paradigm Two. I t is possible that the expressive actions of an adult model maintain a certain amount of inherent value for a few of the children, or that the actions acquire some value from the spread of the affectivity that is associated with a generally nurturant and rewarding model. But it should be noted that the frequencies of imitative lifting behavior for children from Paradigm One are not reliably greater than t h e frequencies for children from Paradigm Four, who were not explicitly rewarded by the agent for their own originally correct performances. This finding suggests that sufficient affective value to control the imitative behavior of some of t h e latter group may have become attached to their cognitive representation of the agent’s expressive movements. I t seems quite likely that sheer information about the correctness of their performance might have been enough to establish this value, without the additional components of positive affectivity which would have been induced by physical affection, verbal approval, and candy. However, the frequencies with which imitation includes lifting tend to be bimodal among the children from Paradigm Four, in contrast to the relatively uniform distribution of frequencies among children in Paradigm One. It may be that there are some predispositional differences among the children in their respective orientations toward correct performance in a task and toward the nurturant attributes of a model. For reasons which were pointed out in the earlier analysis of the sources of affectivity in imitation, attempts to gain experimental control over

children’s imitative learning o f expressive behavior would be especially vulnerable to such differences. Subjects from Paradigm One are also reliably different from those in Paradigm Three, when they are compared with respect to the relative ranks of the frequencies of their imitative lifting behavior (peund P/iy.siologic~cr/Psychology, 1959, 52. 370-372. Armstrong, E. A. Bird displuy ~)idhehui.ior.London and New York: Carnhridge Univei-sity Press, 1947. Armstrong. E. A. A study of’ bird song. 1-ondon and N e w Yoi-k: Oxford llniversity Press, 1963. Aronfreed, J . T h e origin of self-criticism. P.sychologic.ui Ke\,iew. I964,71. 193-2 18. Aronfreed. J. Condrtct und conscience: ?’he sociulizution of’internnlized control over hehuiiior. New York: Academic Press, 1968. (a) Aronfreed, J . Aversive control of socialization. In W. J. Arnold (Ed.), Nebruskti symposium o n motiwfion. Vol. 16. 1.incoln. Neb.: University of Nebraska Press, 1968. Pp. 27 1-320. (b) Aronfreed, J . The socialization of altruistic and sympathetic behavior: Some theoretical and experimental analyses. In J. R. Macaulay (Ed.), AItrtrism rind helping. (tentative title) New York: Academic Press, 1969. in press. Aronfreed. J., & Paskal. V . T h e developnient of sympathetic behaviol- in children: an experimental test of a two-phase hypothesis. Unpublished manuscript. University of Pennsylvania. 1966. Aronfreed. J., & Rebel-, A. I ntei-nalired behavioral suppression and the timing of social punishment. Journal of’Personalitv nnd .Soc.iul P.\ychology, 1965, 1. 3- 16.

Asch. S. F.. Suc.itr/p.syc.hr)lc,fiy.Engk~w~ootl (‘1111s. N I . : Pi-entice-Hall. 1952. Asch. S. F.. Studies of independence ;ind conformity: I . A minorit) of onc aguinst 21 unanimous majoi-ity. P.s?.r./rologic~o/ t b f o ~ ~ r ~ ~ r 1956, t ~ / ~ 70 / ~ .(4, \ . Whole No. 416). Arrin, N . H.. & Lindsley, 0. R. I tic reinforcement of cooperation hetwc.cn children. Jorrrr?rr/0,f’AbflOf’t?lcl/ r l / l t / .sOCifl/ P.\\ r ’ / l O / ( J & , V , 1‘156. 52. 100- 102. Haer, D. bl., Peterson. K. F.. & Shci-iiiaii. I A . The development o f imitation b y reinforcing Ar?cr/ysi.c r!f’ R e / ? t r ~ . i r w . behavioral similarity to a model . / o r r r t ? r r / of //rr, E.upcvir?rc~frtrr/ 1967,10.405-416. Baer. 0 . M . , & Sherman. J . A . Reinforcenient control of genet-ulizcd imitation in young children. Jorrrncrl c?fF;rpc,r.irnc,n/cr/(‘hild P,\v(,/ro/ogy.1964, l . 37-49. Baldwin, I . bl. Menrrrl c/ei,c.lopment 111 / l i e c.lriltl t r d irr / / r e m c c . N e w York: blacrnillan. 1895. Handura, A. Social learning through iniitti t o / C'h ild P.sychology, I 9 6 5 , 2, 2 80- 2 89. Mnrler. P. ('omniunic~ition in moiiheys and apes. In I . DeVore ( E d . ) . f r i u i u f t , hehcriior: Field .sliidic.s c!f'rnorike,y.s crrid trpc's. New York: Holt. Kinehart. & Winston, l06.5. Pp. 544-583. blarler. P.. HL H;imilton. W . J . , 111. dMrc~/iertiisrnsof t r t i i r ~ ( r /heh(ri.ic~r.N e w Yorh: Wiley. 1966. hlarston, A . K. Imitation. self-reinfoi-cement. and reinforcement of another person. Journcrl c!fPersorlcrli/y crrrd Socitrl Psyc~/70/0gy,1965. 2 . 255-26 I . blarston. A . R. Deter-minants of the effects o f vicarious reinfoi-cement. Joi!rt7(r/ of Expczrir ? r < , ~ i / < iP l s ~ c . / I o /1966. o ~ ~ 71. . 550-558, Mason. W . A. Development o f conimunication between young rhesus monkeys. Sriericc, 1959. 130. 7 12-7 13. blason, W. A . The social development of monheq.5 and ape.;. I n I . DeVore ( E d . ) . Prinicrte b c ~ h c r l ~ i o r Field .: slrtelic,.s ( Jljl f 0 l ~ k crriel trpczs. New Yorh: Holt. Kinehart. & Winston. 1965. Pp. 514-543. M 'issermiin. , .. J . H . HahtriYor crnd rwrrrosis. Chic:igo: University of ('hicngo Press. 1943. Mazserman. J . H.. Wechkin. S . . Xr Terris. W. "Altruistic" behavior in rhesus monkeys. Al??