Advances in
THE STUDY OF BEHAVIOR VOLUME 15
Contributors to This Volume WILLIAM W. BEATTY T. M. CAR0 W. J . CARR DAR...
16 downloads
650 Views
16MB Size
Report
This content was uploaded by our users and we assume good faith they have the permission to share this book. If you own the copyright to this book and it is wrongfully on our website, we offer a simple DMCA procedure to remove your content from our site. Start by pressing the button below!
Report copyright / DMCA form
Advances in
THE STUDY OF BEHAVIOR VOLUME 15
Contributors to This Volume WILLIAM W. BEATTY T. M. CAR0 W. J . CARR DARLENE F. KENNEDY S. N . KHAYUTIN PAUL MARTIN MICHAEL J . MEANEY KLAUS R. SCHERER DAVID F. SHERRY JANE STEWART
Advances in THE STUDY OF BEHAVIOR Edited by
JAY S . ROSENBLATT Institute of Animal Behavior Rutgers University Newark, New Jersey
COLINBEER Institute of Animal Behavior Rutgers University Newark, New Jersey MARIE-CLAIRE BUSNEL Laboratoire de Physiologie Di@&entielle Groupe Ge'ne'tique et Comportements Paris, France PETERJ . B. SLATER Department of Zoology The University St. Andrews Fife, Scotland
VOLUME 15 1985
ACADEMIC PRESS, INC. (Harcourt Brace Jovanovich, Publi\her\)
Orlando San Diego New York London Toronto Montreal Sydney Tokyo
COPYRIGHT @ 1985, BY ACADEMIC PRESS. INC. ALL RIGHTS RESERVED. NO PART OF THIS PUBLICATION MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM OR BY ANY MEANS, ELECI'RONIC OR MECHANICAL, INCLUDING PHOTOCOPY, RECORDING, OR ANY INFORMATION STORAGE AND RETRIEVAL SYSTEM, WITHOUT PERMISSION IN WRITING FROM THE PUBLISHER.
ACADEMIC PRESS, INC. Orlando. Florida 32887
United Kingdom Edition published by
ACADEMIC PRESS WC. (LONDON) LTD. 24-28 Oval Road, London NWI 7DX
LIBRARY OF CONGRESS CATALOG CARD NUMBER:
ISBN 0-12-004515-X PRINTED IN THE UNITED STATES OF AMERICA
85 86 87 88
9 8 7 6 5 4 3 2 1
6 4-803 I
Contents
CotitriBic/or.s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pr+uce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ix xi
Sex Differences in Social Play: The Socialization of Sex Roles MICHAEL J . MEANEY. JANE STEWART. AND WILLIAM W . BEATTY I. I1 . I11. IV .
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Determinants of Sex Differences in Social Play . . . . . . . . . . . . . . The Function of Social Play . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 4 32 45 48
On the Functions of Play and Its Role in Behavioral Development PAUL MARTIN AND T . M . C A R 0 I. I1 . I11. IV . V. VI . V11.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Defining Play . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Existing Evidence Concerning the Functions of Play . . . . . . . . . . Play May Have No Major Benefits . . . . . . . . . . . . . . . . . . . . . . . . Theoretical Problems in Detecting the Benefits of Play . . . . . . . . Methodological Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V
59 61 66 78 85 93 97 98
v1
CONTENTS
Sensory Factors in the Behavioral Ontogeny of Altricial Birds S . N . KHAYUTIN
I . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 I1. Organization of Natural Behavior in the Nestling . . . . . . . . . . . . . 108 111. Development of Acoustic Sensitivity . . . . . . . . . . . . . . . . . . . . . . . IV . Role of Audition in the Organization of Defense Behavior . . . . . . V . Ontogeny of Some Visual Mechanisms . . . . . . . . . . . . . . . . . . . . . V1. Complexity of Behavior Organization in Early Postembryonic Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VII . Discussion and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
118 128 134 138 143 149
Food Storage by Birds and Mammals DAVID F . SHERRY
I . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 I1. Memory and the Recovery of Stored Food . . . . . . . . . . . . . . . . . . 160 111. Social Consequences of Caching . . . . . . . . . . . . . . . . . . . . . . . . . . 168 IV . Economics and Decision Making . . . . . . . . . . . . . . . . . . . . . . . . . . 171 V . Food Storing and Food Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 VI . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
181 183
Vocal Affect Signaling: A Comparative Approach KLAUS R . SCHERER
I . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 I1 . Empirical Evidence on Vocal Indicators of Emotion . . . . . . . . . . . 191 111. A Psychobiological Approach to Emotion . . . . . . . . . . . . . . . . . . . IV . Emotional Determinants of Vocalization .................... V . The Component Patterning Theory of Vocal Affect Expression . . VI . Cross-Species Universality in the Component Patterning of Vocal Expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VI1. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
198 206 215 235 237 238
CONTENTS
vii
A Response-Competition Model Designed to Account for the Aversion to Feed on Conspecific Flesh W. J . CARR AND DARLENE F. KENNEDY
I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11. The Aversion by Norway Rats to Feed on Conspecific Flesh . . . . III. A Response-Competition Model . . . . . . . . . . . . . . . . . . . . . . . . . . . IV. Constraining Intraspecific Predation via Response-Competition . .
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Contents of Previous Volumes . . . . . . . . . . . . . . . , . . , . . , . , . . . . . . . . . . . . . . . . , . . , . . , . .
245 248 263 268 270
215 279
This Page Intentionally Left Blank
Contributors Numbers in parentheses indicate the pages on which the authors’ contributions begin
WILLIAM W. BEATTY ( I ) , Departtnent University, Fargo, North Dakota 58105
of Psychology, North Dakota State
T. M. C A R 0 (59), Sub-Department of Animal Behuviour, University of Cambridge, Madingley, Cambridge CB3 8AA, England
W. J. CARR (245), Department of Psychology, Beaver College, Glenside, Pennsylvania I9038 DARLENE F. KENNEDY (245), Department of Psychology, Beaver College, Glenside, Pennsylvania I9038
S. N. KHAYUTIN (103, USSR Academy of Sciences, Institute of Higher Nervous Activity and Neurophysiology, Moscow I 1 7485, USSR PAUL MARTIN (59), Sub-Department of Animal Behaviour, University of Cambridge, Madingley, Cambridge CB3 8AA, England MICHAEL J . MEANEY ( l ) , Center for Studies in Behavioral Neurobiology, Department of Psychology, Concordia University, Montreal H3G I M 8 , Canada KLAUS R. SCHERER (189), Department of Psychology, University of Giessen, 0-6300 Giessen, Federal Republic of Germany DAVID F. SHERRY (153), Department of Psychology, University of Toronto, Toronto, Ontario M5S I A l , Canada JANE STEWART ( l ) , Center for Studies in Behavioral Neurobiology, Department of Psychology, Concordia University, Montreal H3G l M 8 , Canada
ix
This Page Intentionally Left Blank
Preface The aim of Advances in the Study of Behavior is to serve the increasing number of scientists who are engaged in the study of animal behavior by presenting their theoretical ideas and research to their colleagues and to those in neighboring fields. Since its inception in 1965, this publication has not changed its aim, to serve “. . . as a contribution to the development of cooperation and communication among scientists in our field.” We acknowledge that in the interim new vigor has been given to traditional fields of animal behavior by their coalescence with closely related fields and by the closer relationship that now exists between those studying animal and human subjects. Scientists studying animal behavior now range from ecologists to evolutionary biologists, geneticists, endocrinologists, ethologists, comparative and developmental psychobiologists, and those doing research in the neurosciences. As the task of developing cooperation and communication among scientists whose skills and concepts necessarily differ in accordance with the diversity of phenomena that they study has become more difficult, the need to do so has become greater. The Editors and publisher of Advances in the Study of Behavior will continue to provide the means to meet this need by publishing critical reviews, by inviting extended presentations of significant research programs, by encouraging the writing of theoretical syntheses and reformulations of persistent problems, and by highlighting especially penetrating research that introduces important new concepts.
xi
This Page Intentionally Left Blank
ADVANCES IN THE STUDY OF BEHAVIOR. VOL. 15
Sex Differences in Social Play: T h e Socialization of Sex Roles* MICHAEL J. MEANEYAND JANE STEWART CENTER FOR STUDIES IN BEHAVIORAL NEUROBIOLOGY DEPARTMENT OF PSYCHOLOGY CONCORDIA UNIVERSITY MONTREAL, CANADA
WILLIAMW . BEATTY DEPARTMENT OF PSYCHOLOGY NORTH DAKOTA STATE UNIVERSITY FARGO, NORTH DAKOTA
Introduction ........................ ............ Determinants fferences in Social Play . . . . ...... A. Social Play in Mammals.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. Sex Differences in Social Pla ..................... C. Neuroendocrine Basis of Sex rences in Social Play.. . . . . . . . . . . D. Social Influences in Social Play.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111. The Function of Social Play . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. Developmental Significance of Social Play. . . . B. Relationship between Sex Differences in Adult Behavior and the Nature of the Contribution of Social Play to Social Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. Sex Differences in the Response to Social Deprivation.. . . . . . . . . . . . D. Possibility of Immediate Consequence of Social Play . . . . . . . . . . . . . . IV. Conclusion . . . . . . . . . .................................... References . . . . . . . . . ....... ............. I.
11.
2 4 4 14 17 28 31 32 32
34 44 45 46 48
*We are publishing two articles on the subject of play in this volume of Advances in rhe Srudy of Behavior. The two articles are quite different from one another and, since this series has not published any articles on play in previous volumes, we felt that having these two articles would provide our readers with a limited survey of this interesting and important topic in animal behavior [the Editors].
I
Copyright 0 198.5 hy Acddcmic Press. Inc. All rights of reproductinn In any forni reserved. ISBN 0-12-004.515-X
2
MICHAEL J. MEANEY ET AL.
I.
INTRODUCTION
Sex differences in social behavior exist in all mammalian species. The very act of copulation requires that the participants be engaged in different behaviors. These differences also extend to courtship or proceptive behaviors, such that males are normally attracted to the social cues of females and females are normally attracted to the social cues of males. In most species, however, there are sex differences in social behavior that extend beyond these rather obvious differences in mating behavior. Reports of sex differences in behaviors such as social grooming, infant care, territorial defense, and dominance-related activities are common, especially in primate species (for a review, see Mitchell, 1979). Variations occur across species in the extent to which the occurrence of these and other nonsexual, social behaviors are sexually dimorphic. Nevertheless, in most species of social-living mammals, there exist sex roles within groups. One problem that has received considerable attention has been the description of the factors that influence the development of sex differences in social behavior. The majority of the work on this problem has focused on the influence of perinatal hormonal events and, in particular, on the influence of gonadal steroids. Thus, in many species the expression of a particular, sexually dimorphic behavior has been associated with the early exposure to gonadal hormones (for reviews, see Beatty, 1979; Goy & McEwen, 1980). This developmental influence has been attributed to an organizational effect of gonadal hormones (Phoenix, Goy, Gerall, & Young, 1959). According to this organizational hypothesis, hormones act during an early period of neurogenesis to organize the CNS in such a way that an individual is predisposed to respond to a particular stimulus in a certain way. An organizational effect is an empirical concept, and it is defined by instances in which the probability of the occurrence of a particular behavior can be statistically related to the presence or absence of a hormone during some previous period of development. In examining this hypothesis, behavioral endocrinologists have described several hormonal events that, in part, account for the development of sex differences in social behavior. The development of social behavior, including behaviors that are sexually dimorphic, is also dependent on the early social experience of an animal. There is strong evidence from several mammalian species, and in particular from rhesus monkeys, that the deprivation of social contact during the preadult period interferes with the ability of an animal to exhibit normal social behavior. Behaviors such as male mounting (e.g., Harlow, 1969; Gerall, Ward, & Gerall, 1967; Hard & Larsson, 1968), female presenting (Harlow, 1969), agonistic behavior (Lore & Flannelly, 1977; Mason, 1961), and affiliative behaviors (Harlow, 1969) have all been found to be influenced by the absence of early social contact. Thus, in many species the ability to express male-typical or female-typical patterns of behavior is dependent on certain early experiences with other animals.
SOCIAL PLAY
3
Considered in this way, the degree to which an animal expresses the behaviors typical of the male or female role within any group is dependent on early social interactions with conspecifics as well as on perinatal and concurrent hormonal events. In most species these early social interactions occur in the context of play behavior, and it is interesting to note that there are, in many species, sex differences in the social play of young animals (see Table I). The range of species (literally from pinnipeds to primates) in which sex differences in social play have been observed is impressive. These sex differences in the social play of infant and juvenile animals suggest that the opportunities for early social learning may depend on the gender of the young. The possibility exists, then, that these sex differences in social play contribute directly to sex differences in adult social behavior. The two questions that emerge from these considerations, and the questions upon which we have focused this article, are (1) what are the determinants of sex differences in social play and (2) what are the functions of sex differences in the socialization process as a whole. In the pages that follow we shall argue that social play does serve to facilitate the social development of young animals and that sex differences in social play are directly related to sex differences in adult social behavior. In answer to the question of the determinants of sex differences in social play, it appears that perinatal hormones, independent of their actions on adult social behaviors, exert organizational effects on social play. The sex differences observed in one form of social play, play-fighting, appear to be due, in part, to the actions of perinatal androgens. Sex differences in social play, however, also seem to be influenced by the differential behavior of the adults, especially the mother, toward the male and female infants. The behavior of the adults toward male infants appears to enhance the forms of social interactions that best serve the social development of males, and the same appears to be true of the behavior of adults toward female infants. Thus, both perinatal hormone actions and adult-infant interactions serve to promote sex differences in social Play. This illustration of sex differences in the socialization of infant and juvenile behavior is not universal across species. Likewise, sex differences in adult social behavior also vary across species. This variation can serve as the basis for a comparative analysis. The approach taken here with respect to the function of play has been to compare the social play of males and females in species in which there are well-documented sex differences in adult social behavior with that of species in which sex differences in adult social behavior are far less pronounced. We believe that this form of analysis may be one of a few ways in which to address meaningfully the question of the function of social play. There are several pitfalls in attempting to generate conclusions based on the behavior of species that vary greatly in their morphology, ecology, and social organization. It is unlikely that we have avoided all of them. The present analysis
4
MICHAEL J . MEANEY ET A L .
TABLE I S U M M A R Y OF
EVIDENCE FOR
S t X D l b F E R t N C t S IN
PLAY-FIGHTING ACROSSSPECIES Finding
6>9
Species studied
6-9
Primate Hominoideu (apes and man)
Humans
Blurton-Jones (1976); Braggio et a / . (1978); Blurton-Jones and Konner ( 1 973) van Lawick-Goodall (1968)
Chimpanzees Cercopithecoideu (old-world
monkeys) Cercopithecinae
Rhesus monkey
Bonnet monkey Stumptail monkey
Harlow ( I 965); Hinde and Spencer-Booth (1967); Symons ( 1974) Simonds (1977) Bertrand (1969)
Olive baboon Hamadryas baboon
Owens (1975a.b) Kummer 1968)
Pupio
Cercopithecus
Vervet monkey
Bramlett (1978); Raleigh
Talapoin monkey Patas monkey
Wolfheim ( 1977) Seay et al. (1972)
(1979)
Colobinae
Hanuman langurs
Jay (1963); Hrdy (1977)
does, however, provide a number of hypotheses that can in the future be directly refuted by observations from the appropriate species. In this way we believe that the analysis provided in this article forms a context within which a fruitful debate about social development might occur.
11.
A.
DETERMINANTS OF SEXDIFFERENCES I N SOCIAL PLAY
SOCIALPLAYI N MAMMALS
In this section we shall outline the various forms of social play that have been reported to occur among juvenile mammals. In addition, we shall consider the problem traditionally associated with play behavior, that of the definition of play as a behavioral category.
5
SOCIAL PLAY
TABLE I (Continued) Finding Species studied
Ceboideu (new-world monkeys) Suirniri Squirrel monkey Cullitrichinue Common marmoset Nonprimate species Cunis Timber wolf Coyote Domestic dog F r lidue Domestic cat Rodentiu Norway rat
Golden hamster
d > ?
6 5 9
Baldwin and Baldwin ( 1974) Abbott (1978)
Bekoff (1974, P.c.; Traylor, 1982) Bekoff (1974) Bekoff ( 1974) Barrett and Bateson (1978) Meaney and Stewart (1981a,b); Poole and Fish (1976); Olioff and Stewart (1978) Goldman and Swanson (1975)
Mongolian gerbil
Meaney (unpublished)
OViS
Domestic sheep Pinniped Stellar sea lion
Sachs and Harris ( 1978) Gentry (1974)
1. Play-Fighting
The most commonly reported form of social play is that of play-fighting, this behavior has also been referred to as rough-and-tumble play (e.g., BlurtonJones, 1976; Harlow, 1969) or as mock combat (Calhoun, 1962). The behavioral components of play-fighting vary from species to species but are generally predictable from a knowledge of those components involved in the fighting of adults. As Aldis (1975) has noted, the apparent “goal” of the participants involved in play-bout is to “mouth” or to play-bite an opponent (see Figs. 1-3). Both of these behaviors may be interpreted as an inhibited form of biting. In many species play-fighting also involves an attempt to get on top of (to dominate) the other animal, and descriptions of play-fighting invariably include a reference to wrestling-like behaviors (see Figs. 4-6).
6
MICHAEL J . MEANEY ET AL.
FIGS. 1-3. Play-fighting in wolf cubs and in juvenile vervet monkeys. Note the open mouth approach in each case. All photographs in the text are by M. Meaney and D. Cantin.
SOCIAL PLAY
7
Fig. 3.
This apparent similarity between the behavioral components that make up play-fighting and those that constitute one feature of the agonistic encounters of adults, then, is one of the defining features of play-fighting. Naturally this raises the question of how one in turn can discriminate between play-fighting and intraspecific aggression. Traditionally, play-fighting has been distinguished from “real” fighting by its seeming lack of seriousness. Even though this may appear a somewhat nebulous and unsatisfying description, it is not hard to find evidence for the differences between play-fighting and intraspecies aggression. An example comes from the work of Poole (1966) with polecats (Mustella putorius). Poole reports that five out of seven of the behaviors that appear in the attack component of the agonistic encounters of adults also appear in the play-fighting of juveniles, as do three out of four of the behaviors that constitute the defensive components. The two attack behaviors that were absent in play-fighting (sustained neck-biting and sideways attack) are behaviors that serve the function of inflicting injury on an opponent. The defensive behavior not seen in play-fighting was that of defensive threat. The “screaming” vocalization recorded from attacked adults was also not heard during play-fighting. These latter two behaviors may be seen as a response to the attack components of neck-biting and sideways attack. Thus, in the play-fighting of polecats, the more extreme forms of both the attack and the defensive components of adult aggression are not observed. Similarly, in the play-fights of juvenile Norway rats, the distress vocalizations that are common in the agonistic encounters of adults are rarely
8
MICHAEL J . MEANEY E T AL.
FIGS.4-6. Play-fights in several species (shown here in wolf cubs, hamadryas baboons, and Norway rats) culminate in one animal on top of another.
SOCIAL PLAY
9
Fig. 6.
recorded (Calhoun, 1962; Meaney & Stewart, 198 la). Another distinguishing feature of play-fighting among rats is that, unlike adult agonistic encounters, roles (i.e., attacker/target) are frequently reversed; an animal that is dominated for a brief period during a play-bout will often immediately pounce on the other animal and then dominate it (Poole & Fish, 1976). Symons (1974) has reported that in the rhesus monkeys the facial expressions that characterize the combatants in an aggressive encounter are not seen in the play-fighting of juveniles. Particularly noteworthy is that in the play-fighting of rhesus monkeys “there are no gestures of threat or submission” (p. 321). Rather, in many species there are facial expressions (van Hoof, 1972; Symons, 1974) and body postures (Bekoff, 1974) that are unique to play-fighting. In children (Blurton-Jones & Konner, 1973) the feature most commonly associated with play-fighting is a laugh-play face. Thus, while play-fighting is similar to the fighring components of an agonistic encounter, it bears little resemblance to the ritualized forms of intraspecies aggression (particularly the communication of threat) that predominate within the stable social groups of most mammals. In addition, play-fighting contains only the milder forms of attack and defense seen in the fighting of adult animals. Most notably absent in play-fighting are components that lead to the infliction of injury in an opponent and, thus, the components associated with “defeat.” It is probable that, although one animal may gain the upper hand in the course of a wrestling bout, there is no defeat or complete submission. Thus,
10
MICHAEL J . MEANEY ET AL.
the immediate function for the participants of a play-fight is apparently different from that for animals involved in an agonistic encounter whether it involves direct fighting or ritualized gestures.
2.
Chase Play
Harlow (1969) has described a form of play that occurs between juvenile rhesus monkeys and that has been termed approach-avoidance play. This form of play involves one animal approaching and then quickly retreating from another animal. The end point of this sequence is often a chase in which the animal that has been approached chases the animal that has withdrawn. Owens (1975a) has described a very similar pattern of social play in juvenile olive baboons, referred to as dodging play. Here again the pattern seems to be an invitation for chase. We have observed a similar form of social play in juvenile Norway rats. Among rats the sequence involves an approach and pounce followed almost immediately (60%). The names of the 16 vocalizations shown are, beginning with the innermost circle, I, spitting, growling, purring; 11, shriek-cackling, cackling, chattering, twittering; 111, squealing. isolation peep, chirping; IV, alarm peep, yapping, clucking; V, shrieking, cawing, groaning. From Jurgens (1982, p. 55).
208
K L A U S R. SCHERER
mation or meaning of a discrete, discontinuous kind is encoded by the structural relationships of the different acoustic features and the referents of the discrete classes of vocalizations. On the other hand, the individual acoustic parameters which constitute the call-specific structural configurations can change continuously within certain limits. This makes analog coding of continuous underlying dimensions such as arousal or aversiveness possible. A more detailed discussion of the interesting issues of the design features of communication systems and the different types of codes, such as discrete versus continuous, iconic versus arbitrary, or probabilistic versus deterministic is beyond the scope of this article (see Giles, Scherer, & Taylor, 1979; Hockett, 1960). It may be noted in passing that many of the issues relevant to coding have interesting implications for theories on the origin of language and the issue of referentiality in animal communication (see Green & Marler, 1979). In the following discussion of the emotional determinants of vocalization, a distinction between the class or type of vocalizations and the modality of production of that type, reflecting the specific values of the variable parameters for this token, will be made. Thus, as discussed earlier, in many animal communication systems there are a limited number of particular classes of calls, the types, which seem to have distinct emotional/motivational or, in some cases, object-referential (e.g., type of predators) meaning. In human vocal communication, language has developed as a second, more powerful system of communication which often dominates but has not entirely replaced the older nonverbal system of affect vocalization which is probably phylogenetically continuous (see Scherer, 1979a; and below; but see also Goerttler, 1972, for a description of some discontinuities dnd unique features of the human voice). The types in this nonverbal vocal system, sometimes called “interjections” by linguists, consist of the “uhs,” “ahs,” and “ohs” that humans tend to produce under strong emotional arousal (or, interestingly enough to assure their interaction partners that an emotion is truly felt). Scherer (1977), based on early suggestions by Wundt (1900), proposes a distinction between spontaneous affect vocalizations which are likely to be universal across languages and vocal emblems, stereotyped and ritualized vocalizations that have been integrated-phonologically and often lexicallyinto a language system (often without affective meaning). These types of vocalizations can be produced by many different patterns of interacting respiratory, phonatory, and resonatory settings in both animals and humans. The resulting acoustic waveforms differ in features which vary in the intensity, frequency, and time domains. As suggested above, variations in these features which do not change the type of vocalization will be called modality of production of a token, for example, variations in the energy distribution in the spectrum and in the height of fundamental frequency (FO). A more detailed nontechnical introduction to the processes of voice production and the major
VOCAL AFFECT SIGNALING
209
acoustic parameters as well as their measurement (including references to the more technical literature) can be found in Scherer ( 1982a).
B.
INTERNAL PUSH AND
EXTERNAL PULLEFFECTS
Which factors are likely to determine the occurrence of particular types of vocalization and the nature of their production, the modality? Scherer and his associates have distinguished internal push and external pull factors in trying to identify the determinants of paralinguistic behavior (Scherer, Helfrich, & Scherer, 1980, p. 279): “Are paralinguistic features such as tempo and rhythm of speech and pitch and quality of voice determined by an internal, intrapersonal ‘push’ exerted by personality traits and dispositions as well as affective states or by the external ‘pull’ of social norms and expectations concerning the appropriateness of particular speech patterns and the need for adequate self-presentation?” In terms of the component process model, these push factors are defined as those changes in the states of the internal support and action subsystems which affect the production of vocalization in an essentially nondirective manner. For example, increased muscle tension produced by ergotropic arousal can affect breathing patterns, the shape of the vocal tract, and facial expression. In addition, the behavior resulting from a particular emotional state, such as threat postures and rapid movement, for example, will also affect vocalization (Zahavi, 1982). These effects are exemplified by Darwin’s notion of “muscles thrown into violent action.” In other words, internal factors “push” voice production in various ways and without a predetermined direction or set point in terms of acoustic targets; the acoustical outcome, which results from the interaction of the different forces applied, is free to vary, whereas the factors that produce it are determined. For example, if an object is pushed down a hillside, the “pusher” usually does not intend to determine or predict the exact location of the final resting point, yet the laws of physics determine the course of the object. External pull factors, on the other hand, are defined as norms or expectations imposed by the external physical or social environment which require the production of specific acoustic features in terms of a set point or target. The sender needs to produce this acoustic pattern to achieve a particular effect, particularly in those cases where vocal communication serves adaptive purposes. In this case, the acoustic outcome or target is fixed, and the processes by which it is brought about are variable. In terms of the example used carlier, if an object is pulled up a hillside, the “puller” usually has very definite intentions concerning the final resting point of the object and will attempt to overcome all those physical forces obstructing the desired course. One such pull factor which is obviously important for socially living species in
210
KLAUS R . SCHERER
which members of a group might be dispersed over an area concerns the distance transmission characteristics of a sound structure and the locatability of a sender. In this case the physical environment imposes certain acoustic targets. Darwin wrote, “A scream, for instance, uttered by a young animal, or by one of the members of a community, as a call for assistance, will naturally be loud, prolonged, and high, so as to penetrate a distance” (1872/ 1965, pp. 90-91). Many recent surveys of animal communication emphasize the importance of these transmission and localization issues and the selective pressure that they are likely to exert on the acoustic structure of vocalization (Brown, 1982; Green & Marler, 1979; Tembrock, 1975). A second pull factor consists of self-presentation: the kind of impression the sender “wants” to create in the receiver. This might be a form of “vocal mimicry,” if one can assume that particular acoustic features serve as innate releasing mechanisms or always lead to particular inferences or attribution. Again, Darwin supplied an example: “When male animals utter sounds in order to please the females, they would naturally employ those which are sweet to the ears of the species; and it appears that the same sounds are often pleasing to widely different animals, owing to the similarity of their nervous systems. . . . On the other hand, sounds produced in order to strike terror into an enemy, would naturally be harsh and displeasing” (1872/ 1965, p. 91). Morton (1977, see earlier discussion) also seems to specify the mechanism for the harshness-hostility relationship in terms of a pull factor (i.e., trying to give the impression of a big, powerful body by low-frequency harsh vocalization). These examples show rather well to what extent pull factors are based on underlying push effects because big vocalizers naturally phonate at a lower fundamental frequency and small vocalizers at a higher fundamental frequency. The infant-helplessness impression created by the high-pitched harmonic sounds in fear, submission, and friendliness works according to the same principle, although in an opposite direction, that is, making the vocalizer appear smaller. In human communication, self-presentation may be a rather powerful determinant of voice quality and speech style (see Scherer, 1979b). In both animals and humans there seem to be self-presentation tendencies in terms of identity, ability, power, and intention, all of which are likely to affect vocal expression by amplifying or deamplifying the signals likely to result from push effects. Darwin suggested another possible mechanism that might be operative in selfpresentation-the “principle of antithesis”: “The interrupted, laughing or tittering sounds made by man and by various kinds of monkeys when pleased, are as different as possible from the prolonged screams of these animals when distressed” (1872/1965, p. 91). The following quote shows that Darwin thought of this principle in terms of a pull factor: “As the power of intercommunication is certainly of high service to many animals, there is no a priori improbability in the supposition, that gestures manifestly of an opposite nature to those by which
VOCAL AFFECT SIGNALING
21 I
certain feelings are already expressed, should at first have been voluntarily employed under the influence of an opposite state of feeling” (1872/1965, p. 61). Although this principle has not found much acceptance in the literature, it would appear to be a reasonable explanation for some situations in which selfpresentation pull factors seem to be the major determinants of expression. For example, in trying to control an affect expression they do not want to openly display (because of strategic intentions, shame, social display rules, or other reasons), many individuals do seem indeed prone to strive for an expression of an affect state exactly opposite to the one they are actually in. However, for some phenomena it may be possible to find other, more functional and/or parsimonious explanations than the principle of antithesis. For example, as shown in the quote above, Darwin uses the principle of antithesis to explain the acoustic features of pleasure sounds. In turn, he tried to explain the facial features found in smiling and laughter (“corners of the mouth retracted and upper lip raised”) as necessary adjustments of the “orifice of the mouth” to produce these sounds in such a way as to be as opposite as possible to distress screams. Ohala (1980) uses Morton’s (1977) motivation-structural rule explanation to propose an acoustic theory of the origin of smiling. He hypothesizes that in order to produce high-pitched, tonelike sounds, submissive and fearful organisms tend to retract the corners of the mouth to shorten the vocal tract (which raises the resonances). This facial movement may have become an autonomous visual signal in the course of evolution. While this might be a more parsimonious explanation for the smile than Darwin’s, it remains to be explained why the zygomaticus muscle is used to produce the appropriate shape of the vocal tract at the mouth opening rather than other muscle groups which would have the same effect and which would be closer to the facial expression of fear (Ekman, personal communication). A third type of pull factors which may just be a variant of the self-presentation variety concerns the attraction or repelling of others-conspecifics or members of other species. In this case the acoustic features pulled should be the ones that are likely to induce approach or avoidance tendencies, respectively, in potential receivers. A fourth, very clear-cut type of pull effects is associated with conventionalized social signals-stereotyped acoustic sounds that have a shared meaning for the group. For example, predator-specific alarm calls (Marler, 1984; Seyfarth & Cheney, 1982) would seem to belong in this category. In general, any formalized and conventionalized signal, particularly if it involves iconic or arbitrary referencing, will be the result of a pull effect on vocalization. There is a final, fifth type of pull effects-vocal accommodation to an interaction partner. For example, Mundinger (1970) described how flight calls in finches converge on a common group pattern. For humans research in the social psychology of language has shown that speakers converge or accommodate to
212
KLAUS
R.
SCHERER
various speech variables of a conversational partner if they have developed positive affect for the other and diverge in the case of negative affect (Feldstein & Welkowitz, 1978; Giles & Smith, 1979). C.
RELATIVE IMPORTANCE OF PUSHAND PULLEFFECTS
While push and pull factors can be analytically separated, they often seem to work in the same direction. For example, harsh sounds which have been shown to covary with a high degree of arousal, often antagonistic in nature (Green, 1975; Jiirgens, 1979; Morton, 1977; Rowell & Hinde, 1962), also seem to be optimally suited for perceptually focusing attention on the vocalizer. Thus, “collectively, these observations are consistent with the proposition that the level of arousal and the level of contact seeking registered by different calls may be communicatively reemphasized by the signal’s relative locatability. The ease of localization may be one of a number of prelinguistic codes in which a facet of the affective state of the vocalizer covaries with a perceptual dimension” (Brown, 1982, p. 159). Another case of push and pull factors operating in the same direction is the use of harsh voice in agonistic encounters, where aggressive intent and strategic use of this signal to enhance the threat value coincide, as described earlier. This is of course strongly related to the classic issue of the “ritualization of signals” in ethology: expressive behavior elements becoming more stereotyped, being produced with “typical intensity” (Morris, 1957) to provide unambiguous information to the receiver or to hide their true motivation in antagonistic encounters (Maynard Smith, 1972) and thus becoming “emancipated” from the motivational states they were originally connected with (Hinde, 198 1; Huxley, 1966; Lorenz, 1965; Smith, 1984; Tinbergen, 1952). The strong pressure exerted by impression (pull) factors on expression (push) factors during the course of the evolution of communication in socially living species is the topic of a stimulating paper by Leyhausen (1967). The relationship between the acoustic structure of the signal and the nature of the referent, then, is frequently similar for both push and pull effects, with the former having developed out of the latter. The difference between the two types of effects is the actual presence or strength of the referent-the referent being an affective or motivational state-at the time when the signal is produced.
D.
DECEFTION IN VOCAL SIGNALING
Producing signals of affective states that the organism does not really experience at the time implies deceptive or manipulative intent. Recently, a number of sociobiologists have claimed that almost all communication is manipulative and deceptive to gain a selective advantage in the reproduction of the organism’s
VOCAL AFFECT SIGNALING
213
genes (Caryl, 1979; Dawkins & Krebs, 1978). This claim implies that virtually all expressive behavior is almost exclusively determined by pull factors and does not provide any reliable information about push factors. If correct, this means that it is impossible to use expressive behavior to diagnose anything other than strategic intent of the sending organism. This rather extreme view has been challenged by a number of other workers in this area. Hinde ( I 98 1) pointed out that there are a number of situations in which cooperative behavior, and consequently truthful signaling, are clearly advantageous to the sender. It would be rather useless and wasteful, for example, to broadcast deceptive messages of sexual readiness to members of one’s own species. In agonistic situations, there is frequently a conflict between several behavioral alternatives (e.g., fight and flight), and the organism may not actually have decided about the behavioral response (a decision which may depend on the changes in the behavior of the opponent). In this case, rather than outright deceit, maximum ambiguity in the meaning of the expressive display would seem to be the optimal strategy (Hinde, 1981). Zahavi (1982, 1983) has argued that an individual who feels superior in an agonistic encounter, confident of winning, does not gain by deception (except by enhancing the expression of confidence to further frighten the opponent), whereas the weaker individual actually stands to lose: producing the deceptive signal is costly and may reduce the chances for successful flight (e.g., by depleting energy). Zahavi concludes that it is the cost of the signal which selects for its reliability. Signals low in cost, in terms of time or effort, can be easily used for deception, without much risk to the sender; the more costly the use of deceptive signals on the other hand, the greater the risk that the disadvantages will outweigh the advantages. “A display of relaxation during an encounter, which provides the rival with the option to attack first, is a reliable display of confidence (the display is reliable) because attacks by rivals select against weak individuals which relax in order to deceive their opponents about their confidence” (Zahavi, 1982). Intuitively, it seems that at least in human communication the sincerity attributed to a sender is directly correlated with the extremity (and thus the cost both in terms of muscular exertion and social image) of an affect display. Furthermore, a signal is seen as all the more trustworthy the closer it comes to being determined by push effects. Scherer (1977) has pointed out that “raw” affect vocalizations seem to be interpreted as more spontaneous and reliable signals, as well as more truly felt, than conventionalized, ritualized “vocal emblems,” produced in a socially stereotyped way with “typical intensity” (cf. Hinde, 1981). For example, the pain experienced by a sender emitting an unarticulated roar seems more real to us than the one indicated by the use of conventionalized emblems like “ouch.” These considerations support the notion that the pull effects cannot move too far away from the original push effects on which they are
214
KLAUS R. SCHERER
based, at least as far as signals of underlying affective states for self-presentation are concerned. This does not hold, of course, for vocalizations with iconic or arbitrary coding of external referents. Clearly, this does not mean that deception will not occur with high-cost signals. On the contrary, as Goffman (1969) has shown rather convincingly, deception is all the more profitable in those cases where the adversary thinks that a maneuver is too costly or risky to involve deception. To be able to fabricate cues commonly held to be difficult to fake is the high art of the skillful deceiver. However, because of the risk involved and the skills needed, the incidence of high-cost cheating is likely to be low. Quite apart from the cost, the efficacy of deceit clearly depends on the reliability of the signal. Nobody, for example, would be tricked by counterfeit money, even though it looked like the real thing, if the real money did not actually buy something. It is difficult to envisage an economy with only counterfeit money circulating. This is equivalent to the notion of a species with exclusively deceptive signal use. Just as deception requires the existence of truth, fake requires the real. If a signal does not represent anything but the deceptive intent of the signaler in most instances of its use (and if, in addition, it is a cheap signal), it would quickly lose its value. For example, if both opponents in an agonistic encounter were able to use the most powerful threat signal available, just because that would be strategically the most advantageous course of action, and if they could do this without incurring any cost or risk, a real fight with a costly outcome should invariably result (losing the advantage of avoiding actual fighting through the exchange of ritualized intention movements/signals). The outcome of such a fight, however, would not be related in any way to the signal use which preceded it, depriving the signal of its adaptive value. It seems more realistic to assume (as most social psychologists do) that self-presentation generally works to modify (enhance or play down) essentially truthful information about traits and states rather than to simulate nonexisting traits or states. It should be noted that the concern in this section has been exclusively directed toward the determinants of the form, that is, the acoustic structure of affective vocalizations. Although concepts like communicative intention, meaning, and message (see Mackay, 1972; Smith, 1977) are obviously related to this discussion, the issues of sender intentionality and signal meaning are too broad and complex to allow adequate treatment in the present context. Speculatively, one might expect push factors to characterize nonintentional, continuous, affective state signaling and pull factors to dominate intentional, discrete, representational signaling. On the whole, then, one has to assume that both push factors (providing essentially truthful information about the affective state of an organism) and pull factors (which may work in the same direction or which may counteract push
215
VOCAL AFFECT SIGNALING
effects if deceptive intent is involved) jointly determine affect expression. The relative predominance of the two types of determinants may vary widely across situations. This is of particular importance in the light of the suggestion that the evolutionary origin and the actual production of many displays may be related to conflicting motives or behavior tendencies (Baerends, 1975; Hinde, 198 I ; Tinbergen, 1959). Assuming that both push and pull factors can underlie motivation and behavior tendencies, this would support the notion that there is usually joint determination of the display by the two kinds of effects. In the next section, I shall propose a theoretical model which attempts to conceptualize the multiple determination of the dynamic patterns of affect expression by interacting sets of push and pull factors. This model is based on human vocalization as the most advanced form of vocal communication. An extension of the predictions to animal call systems and a comparative discussion will be offered in the final section.
v. A.
THE COMPONENT PATTERNING THEORY OF EXPRESSION
VOCAL
AFFECT
THECONCEPTUAL FRAMEWORK
Based on the component process model of emotion, Scherer (1984a) has proposed a theoretical approach concerning the determinants and the nature of emotional expression-the component patterning theory-which emphasizes the dynamic nature of emotional processes and the multiple determination of affective expression by push and pull factors. Since motor expression is produced by the action system (in particular, the striated musculature), expressive behavior will be affected by dynamic changes in response to SEC outcomes. In addition, motor expression is also affected by the changes in the other subsystems of the organism following stimulus evaluation. Thus, the characteristics of the vocal, facial, or postural expression at a particular point in time represent the net result of the effects of the outcomes of preceding SECs in the information processing subsystem and of the total effect of the changes in the other subsystems impinging upon the action system. Table VI (reproduced from Scherer, 1984b) shows some hypothetical predictions concerning the changes in the various organismic subsystems following specific SEC outcomes. While very speculative, the following changes in the various subsystems can be expected on the basis of functional considerations (changes in the functioning of the vocal organs will be described in more detail below). Evaluation of novelty, in addition to the orienting response, may lead to straightening the posture, raising eyelids and eyebrows for scanning, interrupting ongoing loco-
TABLE VI COMPONENT PATTERNING THEORY PREDICTIONS OF SEC OUTCOME EFFECTSON SUBSYSTEMS“ Action system SEC outcome Novelty Novel
N
Organismic functions
Social functions
support system
Muscle tone
Orienting Focusing
Alerting
Orienting response
Local changes
Homeostasis
Reassuring
No change
No change
Recommending
Sensitization Slight of decrease sensorium
Warning Decommending
Defense response: desensitization
lncrease
Announcing stability
Trophotropic shift
Decrease
o \
Old
Intrinsic pleasantness Pleasant Incorporation
Unpleasant
Expulsion Rejection
G o a h e e d significance Consistent Relaxation
Face
Voice
Instrumental
Posture
Locomotion
Browsilids UP Open orifices No change
Interruption Inhalation
Interruption
Straightening Intemption Raising head
No change
No change
No change
Expanding orifices, “sweet face” Closing orifices, ”sour face”
Wide voice
Centripetal Expanding movement Opening
Approach
Narrow voice
Centrifugal movement
Shrinking Closing in
Avoidance Distancing
Relaxed tone
Relaxed voice
Comfort position
Comfort position
Rest position
No change
Activation
Announcing activity
Ergotropic dominance
Increase
Cormgator Tense voice
Taskdependent
Taskdependent
Task-dependent
Readjustment
Indicating withdrawal
Hypotonus
Lowered eyelids
Lax voice
No activity or slowing
Slump
High power/ Control
Goal assertion
Dominance assertion
Slight decrease Tension in head and neck
Baring teeth Tensing mouth
Full voice
Agonistic movement
Anchoring body, lean forward
No movementor slowing Approach
Low power/ control
Protection
Indicating submission
Trophotropic dominance Ergo-tropho balance Noradrenaline Respiration volume UP Ergotropic dominance Adrenaline Peripheral vasoconstriction Respiration rate up
Hypertonus Tension in locomotor areas
Open mouth
Thin voice
Protective movement
Readiness for locomotion
Discrepant
Coping potential No control
-
N
-4
OFrom Scherer (1984b).
Fast locomotion or freezing
218
KLAUS R. SCHERER
motion and instrumental action, and deep inhalation. A pleasantness evaluation is likely to cause autonomic sensitization of the sensory organs and orofacial changes maximizing taste and smell sensations as well as instrumental and locomotor approach behavior. Unpleasantness evaluations should result in autonomic desensitization of the sensory organs and defense reactions, including orofacial actions to close the orifices or to expel noxious matter. This involves faucal and pharyngeal constriction (see below) and instrumental and locomotor distancing or avoidance behavior (Andrew, 1963; Gratiolet, 1865; Huber, 1931; Piderit, 1858; Trojan, 1975). The major function of the goal/need significance check is to prepare the organism for appropriate action if things do not happen according to plan. Cannon (1929) was the first to describe the important functions of “emergency” responses in several organismic subsystems in the case of a threat to the organism. Adopting the functional description of the organismic arousal states in terms of a balance between an ergotropic (mostly sympathetic ANS activation) and a trophotropic (mostly parasympathetic ANS involvement) system proposed by Hess (1954) and Gellhorn (1964, 1970), it is suggested that a state of ergotropic dominance follows a discovery of a mismatch between desired state and actual state. A positive outcome of the goal conduciveness check should produce a shift to the trophotropic side of the ergotropic-trophotropic balance, an effect which I will call trophotropic “tuning,” and a balanced tone in the striated musculature, as well as comfort and rest behavior. A negative outcome-a mismatch between actual and desired state-on the other hand, should produce ergotropic dominance, that is, increasing arousal or activation. The effect on the action system should consist of strongly increased tonic innervation of the musculature as well as phasic task-dependent innervations. A facial expression frequently found in response to this condition is the frown (corrugator activity) which has often been treated as a sign of “something difficult or displeasing encountered in a train of thought or action” (Darwin, 1872/1965, p. 222; see also Ekman & Friesen, 1975; Redican, 1982). When the organism sees no possibility of controlling or avoiding a negative event and its consequences, trophotropic dominance and general hypotension of the musculature with slumping posture, slow movement, and a flaccid facial tone is to be expected. When events or outcomes are still controllable but flight is indicated, ergotropic dominance increases still further to provide the organism with sufficient energy for an emergency reaction. Increased adrenaline secretion redirects blood flow to the muscles of the peripheral organs (for running or defense). The hypertension of this musculature may give rise to trembling. Another effect is peripheral vasoconstriction, which reduces the amount of bleeding in the case of injury. Peripheral vasoconstriction also results in a drop of skin temperature. Finally, respiratory rate increases. If the power subcheck results in the evaluation that there is enough power to
VOCAL AFFECT SIGNALING
219
threaten, and if necessary to fight an adversary, dominance assertion will occur. This is predicted to be accompanied by increased noradrenaline secretion (cf. Ax, 1953), which has a “thermogenetic” effect (van Toller, 1979). This may be the reason why anger feels “hot” (Ekman, Levenson, & Friesen, 1983; Scherer, Summerfield, & Wallbott, 1983). Blood flow is redirected to the head and chest to support threat displays and fighting responses (cf. Baccelli, Albertini, Del Bo, Mancia, & Zanchetti, 1981). The i’acial musculature is predicted to show preparatory biting patterns and tensing of the muscles in the neck and around the mouth. A more detailed discussion and justification of these predictions is provided in Scherer (1984b). However, since there is very little pertinent research evidence in most of the areas addressed in this discussion, the predictions are very speculative and will have to be revised as data become available. Apart from changes in the predictions of details in the patterns, the component patterning model is expected to be borne out by future work. The following simple example for a human vocal response, reproduced from Scherer (1984c), illustrates component patterning in somewhat more detail for vocal expression: Following the appraisal of a stimulus as dangerous and requiring action (obstructive to the important goal of survival; coping potential not guaranteed), FO (fundamental frequency of the voice, heard as pitch) will increase because of the effect on the action system (increased muscle tension); at the same time salivation will decrease because of the changes in the support system (sympathetic dominance in the ANS). Both effects will tend to make the voice sound more high pitched (changes in vocal fold vibration and vocal tract resonance). If a split second later the event is reevaluated as a hoax, the state of the fast-responding action system will change again, lowering pitch because of a decrease in muscle tone. The ANS is slower, and it is likely that the effect of reduced salivation on vocal tract resonsance will persist for some time. This example shows that different aspects or features of affective expressions can be differentially affected by system changes over time, such that the pattern of features at any one point in time reflects the impact of a number of very different factors that occurred at different points in the process. These {actors consist not just of the push factors mentioned earlier (e.g., muscle tone driving up FO) but also of pull factors. In the example given earlier, increased FO is likely to be registered by the monitor subsystem (“My voice is terribly high all of a sudden”), and a control command may be routed to the action system (possibly via the executive system) to reduce FO to a level corresponding to the individual’s baseline (or even below that, to ward off all speculation by observers that arousal might be present). However, this voluntary muscular action, because of the force applied or the particular mechanism chosen to reduce FO, may result in other changes in the phonation pattern that may make the voice sound harsh, for example. Thus, the pattern of vocal features immediately after this command
220
KLAUS R . SCHERER
TABLE VII COMPONENT PATTERNING THEORYPREDICTIONS OF VOCAL CHANCES SEC OUTCOMES" FOI.LOWING DIPFEREN.~ Novelty check Novel
Old No change
Interruption of phonation Sudden inhalation Silence Ingressive (fricative) sound with a glottal stop (noiselike spectrum)
No change
Intrinsic pleasantness check Pleasant
Unpleasant
Faucal and pharyngeal expansion, relaxation of tract walls Vocal tract shortened by mouth corners retracted upward More low-frequency energy, FI falling, slightly broader FI bandwidth, velopharyngeal nasality Resonances raised
Faucal and pharyngeal constriction, tensing of tract walls Vocal tract shortened by mouth corners retracted downward More high-frequency energy, FI rising, F2 and F3 falling, narrow F1 bandwidth, laryngopharyngeal nasality Resonances raised
Wide voice
Narrow voice
Goallneed significance check Relevant and discrepant
Relevant and consistent ~
~~
~~
~
~
Shift toward trophotropic side: overall relaxation of vocal apparatus; increase of salivation FO at lower end of range, low to moderate amplitude, balanced resonance with slight decrease in high-frequency energy
Relaxed voice If event conducive to goal: relaxed voice + wide voice If event obstructive to goal: relaxed voice + narrow voice
~~
~
~
~~
~
Ergotropic dominance: overall tensing of vocal apparatus and respiratory system, decrease of salivation FO and amplitude increase, jitter and shimmer, increase in high-frequency energy, narrow FI bandwidth, pronounced formant frequency differences Tense voice If event conducive to goal: tense voice wide voice If event obstructive to goal: tense voice + narrow voice
+
has been executed is the net result of a multitude of push and pull effects which have consecutively modified the vocal settings and may have all left their traces in determining the vocal features at a particular point in this dynamic process. To understand the factors determining a particular affective expression, the
22 1
VOCAL AFFECT SIGNALING
TABLE VI1 (Continued) Coping potential check Control
No control
Ergotropic dominance: (see tense voice)
Trophotropic dominance: hypotension of the musculature in the vocal apparatus and respiratory system Low FO and restricted FO range, low amplitude, weak pulses, very low high-frequency energy, spectral noise, formant frequencies tending toward neutral setting, broad FI bandwidth
(see tense voice)
Lux voice
Tense voice
Power
No power
Deep, forceful respiration; chest register phonation Low FO, high amplitude, strong energy in entire frequency range
Rapid, shallow respiration; head register phonation Raised FO, widely spaced harmonics with relatively low energy
Full voice
Thin voice
Norm/self compatibility check Standards surpassed
+
Wide voice full voice + Relaxed voice (if expected) Tense voice (if unexpected)
+
Standards violated Narrow voice + thin voice + Lax voice (if no control) + Tense voice (if control)
(‘From Scherer ( 1 9 8 4 ~ )
effects of the various components of emotion, including monitor control attempts, on the dynamically changing patterns of motor expression have to be taken into account. It may help to consider the example of the “value-added’’ notion in industrial production (and taxation in some countries) to visualize the process. Each consecutive SEC adds to the meaning of the stimulus or event for the organism, and at each step changes in the different subsystems are instigated which may enhance or modify the states resulting from earlier SEC outcome changes. A vocalization beginning during the evaluation process will be continuously modified as the “value” of consecutive SEC outcome changes are addsd. A vocalization that begins only after the sequence has been completed will reflect the combined effect of the sequence of changes in the various subsystems. According to the component process model and the component patterning model, the outcome of each of the SECs postulated in the sequential evaluation theory of emotional differentiation will have direct effects and indirect effects on
222
KLAUS
R.
SCHERER
affective expression. The direct effects consist of the adaptive changes in the action system (i.e., changes in the tonic and phasic tension of the striated musculature) following the SEC outcome (and possibly mediated through the monitor and executive systems). The indirect effects are the push effects from the changes in other subsystems, such as the support system (particularly the ANS). While these consecutive changes continuously modify the pattern of affect expression, it is possible to analytically separate the specific changes produced by the SEC outcomes. B.
DETAILED PREDICTIONS OF COMPONENT PATTERNING
On the basis of this model, Scherer ( 1 9 8 4 ~ has ) proposed a set of predictions concerning the vocal effects of the different SEC outcomes. Table V11 shows a summary listing of these predictions which will now be described in somewhat more detail. For each SEC, the major adaptive function, the predicted push effects, and possible pull effects will be described (and will closely follow the descriptions in Scherer, 1 9 8 4 ~ ) . 1. Novelty Check
The response of the organism after encountering a novel stimulus is an orienring response: an interruption of ongoing processes, a focusing of attention, and a sensitization of sensory mechanisms in order to gather information about the novel stimulus event and to evaluate its significance. The changes in the organism’s subsystems have been rather well studied: cortical arousal, cardiac deceleration, vasoconstriction in peripheral organs and vasodilation of the blood vessels in the head, pupil dilation, skin conductance increase, and changes in the respiratory pattern (Graham, 1973; Lynn, 1966). Also, postural changes directing the sensory organs (particularly eyes, ears, and nose) in the direction of the novel stimulus, will occur. On the whole, these changes will barely affect vocalization (except, possibly, to interrupt ongoing vocalization). Because the SECs follow each other in very rapid succession, various inspiration and expiration sounds which are often associated with surprising events (Darwin, 1872/ 1965, p. 92) are likely to be the joint result of the novelty check and consecutive SECs. Thus, a positive outcome of the intrinsic pleasantness check will have a differential effect on vocalization, depending on whether the stimulus was evaluated as novel or expected (e.g., the joyful surprise “oh” versus the quiet enjoyment “aah”). In general, the characteristics of vocalizations following a novelty evaluation are predicted to show higher amplitude and steeper onset (more explosive) given the preceding deep inhalation and the need to exhale rapidly. As far as pull effects are concerned, while there may be adaptive value in informing other group members about novel
VOCAL AFFECT SIGNALING
223
events, it may also be dangerous to allow oneself to be localized on the basis of a sound before the stimulus has been analyzed further. 2. Intrinsic Pleasantness Check
In terms of adaptive function, “pleasant” outcomes lead to approach behavior tendencies in the action system, whereas “unpleasant” outcomes instigate avoidance tendencies (Berlyne & Madsen, 1973; Schneirla, 1959; Tobach, 1970). Based on speculations by Darwin (187211965, pp. 21 I , 257) and Trojan (1975), it is argued that the approach-avoidance response most directly relevant to vocalization has to do with the acceptance or rejection of pleasant or noxious foods or smells. The assumption is that the oropharyngeal constriction observed in food rejection or regurgitation has generalized to all unpleasant or painful stimuli, whereas oropharyngeal expansion common in the enjoyment and swallowing of food has become associated with nonnutritive or nonolfactory stimuli evaluated as pleasant. On the basis of the phonetic literature, the following acoustic effects are predicted for an unpleasant outcome: faucal and pharyngeal constriction and tensing as well as shortening of the vocal tract should lead to higher energy in the high-frequency region, narrow formant bandwidth, a rise in F1, a fall in F2 and F3, and some degree of “pharyngeal nasality.” This pattern is called “narrow voice.” The effects of a pleasant outcome are more difficult to predict. Faucal and pharyngeal expansion and relaxation should result in a fall in FI and a lowering of the high-frequency energy. On the other hand, a shortened larynx might offset the latter effect. The net result might be a balanced resonance throughout the frequency range, yielding a clear harmonic structure, as postulated by Trojan (1975). In addition, one might expect some velopharyngeal nasality. The summary description is “wide voice.” It seems likely that pull effects developed in response to this SEC outcome since the sharing of the information that particular stimuli deserve approach and others avoidance would reduce the overall trial-and-error behavior in a group and thus be of adaptive value. An issue of particular interest is the question whether the smile may be a ritualized signal originally based on food enjoyment responses and the accompanying vocalizations characterized by oropharyngeal expansion. In terms of the other explanations for the origin of the smile which have been suggested so far (Andrew, 1963; Ohala, 1980; Redican, 1982; van Hooff, 1972), it would seem possible that there are different kinds of smiles with different functions that might well have developed from different origins. 3.
GoullNeed Significance Check
The major functions of this check are ( I ) to establish the significance of a stimulus or event in terms of the goals or motives of the organism, (2) to
224
KLAUS R . SCHERER
determine whether it is conducive or obstructive to reaching a goal or satisfying a need, and (3) to determine the degree of deviation of the state reached after the stimulus impact from the expected state, thereby specifying the need for external action or internal adjustment. The outcome of this SEC determines the urgency of action and the degree of involvement of the organism. The major effect of this outcome is ergotropic tuning or in the case of emergency reactions, ergotropic dominance. The intensity of ergotropic arousal should increase with increases in the importance of the goals or needs of the organism affected by a stimulus event and increases in the deviation from the expected state. The acoustic effects of ergotropic arousal are fairly well established. On the basis of convergent hypotheses and findings in physiological and acoustic phonetics, the following changes are predicted. Assuming that there are no counteracting pull effects, FO and amplitude increase; there is moderate to extreme jitter and shimmer resulting in the auditory impression of harshness; relative energy of the higher harmonics increases, with corresponding changes in the energy distribution in the spectrum and a narrowing of formant bandwidth (producing the auditory impression of a metallic or piercing voice); and formant values should tend toward greater distance from a neutral position. These characteristics are summarized as “tense voice.” The effects of ergotropic arousal on vocalization are expected to be continuous and graded, that is, the effects should become increasingly stronger as ergotropic arousal goes up. There is no assumption, however, that this relationship is linear. The direction in which there is a discrepancy between desired and actual state affects vocalization in addition to the ergotropic effects. The model predicts that effects similar to a positive outcome of the hedonic valence check will occur if the discrepancy is in the direction of reaching or surpassing the goals: balanced resonance, low F1, and, possibly, velopharyngeal nasality. Conversely, faucal and pharyngeal constriction should occur with failure outcomes, reinforcing some of the characteristics of tense voice and possibly adding faucal nasality. A potential for pull effects is seen in the adaptive advantage of communicating arousal or activity level to the social surround, to advertise the likelihood of highly active behavioral responses to occur in the near future. If expectation and outcome match, the ergotropic-trophotropic balance should shift to the trophotropic side, thereby resulting in “relaxed voice”: FO close to the lower end of the range, low to moderate amplitude, and balanced resonance with slight decrease in the energy of the high frequency region. 4 . Coping Potential Check
This check serves to evaluate the organism’s response potential after a stimulus event requiring a behavioral reaction or internal adjustment has been detected with the goallneed significance check. Three major subchecks determine the nature of the reaction once the causation of a stimulus event (agent and
VOCAL AFFECT SIGNALING
225
motive) has been determined: (1) checking the degree of control over a stimulus event and its consequences (past, present, and future), (2) checking the amount of power to free the organism from domination by the event through external action (fight or flight), and (3) the possibility and difficulty of internal adjustment (e.g., restructuring of goals or self-concept). The outcomes of these subchecks determine the nature of the response, including the type and modality of vocalization. The following acoustic changes are predicted: trophotropic dominance in response to an evaluation of a stimulus event as not controllable and in the case of difficulties with internal adjustment should result in hypotension of the vocal musculature producing the pattern of “lax voice” (low FO and restricted FO range, low amplitude, absence of a clear pulse structure and interharmonic noise due to breathiness, severe energy loss in the upper partials, some nasality, formant frequencies tending toward the neutral setting, and wide formant bandwidth). If the event or its outcome is seen as controllable, the ergotropic system will remain dominant and push vocalization in the direction of tense voice. The second subcheck, the power check, further differentiates the vocal response. A confident outcome is predicted to reduce ergotropic arousal and to result in a shift from tense to relaxed voice. In addition, deep forceful respiration and chest register phonation should produce low FO, high amplitude, and strong energy in the harmonics throughout the frequency range, a pattern named “full voice.” Conversely, further increase in ergotropic arousal and thus tense voice, combined with a pattern referred to as “thin voice,” is expected when the power check is negative. Here, shallow respiration and head register phonation are hypothesized to yield raised FO and widely spaced harmonics with relatively low energy.
5 . Norm Conjormity Check This SEC is expected to occur very late in both phylogenetic and ontogenetic development, with the possibility that it is completely absent in many (or all) species of animals. Thus, it seems rather likely that there is no major biological mechanism responsible for specific vocal effects. The changes in vocalization that do occur may be combinations of the mechanisms described earlier (see Scherer, 1984c, for a more extensive discussion of this point). VI.
CROSS-SPECIES UNIVERSALITYI N THE COMPONENT PATTERNING OF VOCAL EXPRESSION
In Sections I11 and V a new conceptual scheme to describe emotional states in a form amenable to comparative analysis and detailed predictions on the patterning of vocal responses to major determinants of emotion (based on evidence for
226
KLAUS R . SCHERER
human vocalization) have been proposed. In the remainder of the article these tools will be used to attempt an integration and systematic interpretation of the findings on animal and human vocal expression of emotion reported in Section 11. Furthermore, a set of hypotheses for systematic comparative research in this area will be proposed. These hypotheses rest on the assumption that animal and human affect vocalizations are produced by similar central and peripheral processes, an assumption which may need some supportive argument given the enormous differences in structural and functional complexity between animal call systems and human speech on the one hand and animal affective states and human feelings on the other. However, as for many other organismic structures and functions, the specifically human capacities for vocalization make use of phylogenetically old structures, together with some newly evolved structures which supplement and control but do not replace the old, to achieve more complex results. There is good evidence that both in animals and humans, the limbic system is centrally involved in the mediation of emotion (Arnold, 1960; Heilman & Satz, 1983; MacLean, 1975; Pribram, 1984). Brain stimulation studies in animals have shown that the limbic system controls emotional vocalization (Jurgens, 1979; Jurgens & Ploog, 1970, 1976; Robinson, 1972; see also Steklis & Raleigh, 1979). The important role of the limbic system for human affective vocalization is well summarized by Robinson (1972, p. 442): “human speech normally depends on two systems rather than one. The first and phylogenetically older system is located in the limbic system, is bilaterally represented without hemispheric dominance, antedates primate development, is closely related to emotional, motivational, and autonomic factors, and is capable of transmitting only signals of low informational content. The second system is supplementary to the first, was developed in man, is neocortical, lateralized, and usually dominant in the left hemisphere. . . . The two systems seem to be intimately related and normal speech seems to represent a harmonious mixture of both. In rational and logical discourse, the neocortical system is dominant. In times of emotional stress, however, the limbic system reclaims its old primacy and rational thought and speech are subordinated.” Thus, in terms of central organization, animal and human affect vocalization may well share a number of central characteristics even though there are many important differences. The same seems to be true for the peripheral production site, the vocal apparatus. Apparently, only man is equipped with the phonatory and articulatory structures that are required for the production of speech sounds (see Goerttler, 1972; Lieberman, 1975). Neither the chimpanzees, our closest relatives, nor infants can produce all of the vowel sounds utilized in human languages because of the shape of their vocal tract. Yet, many of the major sound production features involved in respiration, phonation, and resonance are similar in many species of mammals (Negus, 1949; DuBrul, 1977). As will be shown later, even the inner-
V O C A L AFFECT SIGNALING
227
vation of differential groups of laryngeal muscles controlling register differences are the same for the squirrel monkey and for man. Certainly, the effect of heightened muscle tension on vocalization should be comparable (see Scherer, 19794. Therefore, in the hypotheses developed below, a generalization from the predictions in Table VII for human vocalization for a comparative approach will be attempted, although changes concerning articulatory processes are excluded (the term formcinr is used to refer to a neutral vocal tract resonance setting). While the component process model outlined earlier theoretically allows for a large number of combinations of different SEC outcomes, and consequently a large number of different emotional states, it seems reasonable to expect that only a small number of major types will occur very frequently, although there is likely to be much variety in terms of the specific combinations of differentially graded SEC outcomes within each type. The appearance of a small number of major types can be attributed to the existence of a few prototypical, recurring situations in the life of organisms, such as encountering pleasant or unpleasant stimuli or experiencing satisfaction or frustration of important needs or goals. Together with the respective coping potential of the organisms these antecedents seem to define the major types of emotions and their behavioral consequences. Given the frequent occurrence of a small number of typical emotional states, as compared to the less frequent appearance of more unusual combinations of SEC outcomes, one can understand why discrete emotions theorists postulate a small number of innate, basic emotions (Tomkins, 1962, 1963; Izard, 1977; Ekman, 1984). However, as pointed out earlier, the view suggested by the present author differs from that position in questioning the unitary and innately prewired nature of emotional responses. There is agreement, however, on the relative importance of a small number of phylogenetically continuous emotional states arising from a rather small set of antecedent situations. A.
MAJORTYPESOF EMOTIONAL STATES
In this section five major types of emotional states that can be expected to occur frequently in the daily life of many organisms, both animal and human, will be discussed: contentment/ happiness, displeasure/disgust, helplessness/sadness, apprehension/fear, frustrationianger. Using the facet description system proposed in Section Ill,J3, we can define these states in terms of the respective SEC outcomes in the information processing system as well as by the predicted states of the support and executive subsystems. For the executive subsystem, not only organism-centered motivations or behavior tendencies will be mentioned but interactional behavior tendencies likely to be evoked by a particular outcome of the SEC sequence. This is based on the assumption that socially living organisms are frequently in the presence of conspecifics when experiencing emotional states, and thus the behavior instigated by an emotional
228
KLAUS R . SCHERER
state is frequently social behavior, whether another individual caused the emotion or not. Given the special focus of this article, only the state changes relevant to vocal expression will be discussed for the action system. The labels used to refer to the five types of emotional states are tentative; they have been chosen in such a way as to deemphasize the “feeling” aspect by adding a description which is more antecedent-oriented in order to minimize the danger of anthropomorphizing in applying these labels to animal states. The feeling language cannot be avoided altogether, though, particularly in referring to the states of the monitor subsystem. Here both terms reflecting the intraorganismic state, using established emotion terms, and terms referring to the state of a relationship with an interaction partner will be used. Clearly, it is not suggested that animals experience such feelings in the same way as humans. However, it is not unreasonable to postulate a monitor subsystem with functions similar to the human case for many species of animals with flexible behavioral repertoires. As mentioned earlier, such a subsystem would be in charge of attention deployment and the mediation of feedback from other subsystems. The latter function is particularly important in emotion, a state which is frequently characterized by conflicting messages from the different subsystems and by competing behavior tendencies. As Jiirgens (1979, p. 98) points out, “Emotional terms . . . are often the only terms available for a brief description of complex motivational states of an animal, that is states which cannot be characterized by the probability of occurrence of a single behavior pattern but only by the probabilities of occurrence of a great number of different behavior patterns.” In summary, then, the types of emotional states discussed below are expected to be descriptions valid for both the human and a large number of animal species. They will be used as a basis for a comparative analysis of vocal expression of emotion. Detailed predictions of the acoustic features of vocalization to be expected for these five types of emotional states are listed in Table VIII. Based on the component patterning predictions for the major SEC outcomes in Table VII and the combinations of SEC outcomes postulated earlier for the five types of states, these predictions can be derived as hypotheses to be tested in further research. Each of the five types of states will now be described in detail. In each case, an attempt will be made to integrate the observations on animal vocal expression described in the first section with the major findings on human expression. While the evidence on animal vocalizations will be examined in some detail, the literature on human vocal expression is referred to only summarily since a detailed discussion is available in Scherer ( 1 9 8 4 ~ )While . the emphasis in this discussion will be on the modal patterns for each type of emotional state, some of the transitions and gradations between patterns will be mentioned. Indeed, the value of the conceptual system proposed earlier is seen particularly in its ability to
229
VOCAL AFFECT SIGNALING
TABLE Vlll PRbDlCTED ACOUSTIC FEATURES OF MAJOREMOTIONAL STATES“
Feature :O modulation ;O mean :O range :O variability :O shift contour :O shift regularity :I mean :2 mean ;I bandwidth ’otal intensity ntensity variation xquency range ligh-frequency energy ipectral noise hation :ate
Contentment/ happiness
Displeasure/ disgust
Helplessness/ sadness
Apprehension/ fear
>
> < >
< Q Q
B
<
>
e
B
>
>
> >
>
Q
9
>
< < <