Acoustic, emotional, and perceptual variation in human screams: Exploring the diversity in a basic call type Público
Engelberg, Jonathan (Summer 2021)
Abstract
The nonlinguistic vocal repertoire predates language in human (Homo sapiens) evolution, and call types such as laughs and screams are likely homologous to acoustically similar calls in nonhuman animals. However, most research on nonlinguistic vocalizations centers on vocalizers’ abilities to express emotion without accounting for the call types represented among those expressions. This perspective ignores important questions about why some call types are associated with a variety of emotional contexts, whether acoustic variation within types is communicatively significant, and what functions they might serve beyond emotional communication. To address these questions in human screams, I adopted an alternative perspective from the literature on animal communication, wherein researchers first identify the call type(s) of interest before exploring their potential meanings and functions. In Study 1, I investigated whether the variation among screams elicits varied emotional perceptions in listeners. Listeners rated contextually diverse screams on six emotion scales. Their ratings of screams varied along two primary dimensions, one separating the perception of anger and pain from happiness and surprise, and one independently accounting for some perception of fear. Acoustic parameters predicted listener ratings in ways consistent with patterns of emotional variation reported in other human and nonhuman vocalizations. To compare this variation in screams to speech directly, in Study 2, I recorded nine actors’ screams and single-utterance speech samples across five emotional contexts. I found similar patterns of acoustic variation by emotion across screams and speech, suggesting that the same mechanisms underlie variation in each vocalization type. Listeners also achieved similar accuracies across vocalization types in an emotion recognition task, although they demonstrated some response biases, such as a greater tendency towards false alarms for pain and fear, that were potentially specific to screams. In an additional task, listeners rated screams on five hypothesis-based perceptual scales. I found that that some perceptual characteristics, such as attention-getting, did not vary significantly by scream emotion, whereas others, such as communicating distress, did vary by emotion, possibly hinting both at general functions that unite screams across disparate emotional contexts as well as more contextually specific subfunctions. In all, these findings suggest that acoustic variation within human call types is informative and functional. I suggest that the influence of language faculties on preexisting call types that are shared with other taxa partly explains the contextual and acoustic diversity of human calls.
Table of Contents
CHAPTER I. GENERAL INTRODUCTION.. 1
Terminology. 6
Lessons from animal communication. 8
Signals, senders, and receivers 8
Function, form, and the role of emotion. 10
Extended example: Emotion and functions of antipredator screams 12
Call types, contextual diversity, and variation within types 14
Extended example: Variation, function, and emotion in primate screams 22
Summary: Applications from animal communication research. 25
Nonlinguistic vocalizations in humans 28
The existence of human call types 28
Possible effects of language on nonlinguistic vocalizations 30
Infant cries 33
Laughter 36
Summary. 37
Human screams and this dissertation. 39
References 44
CHAPTER II. The emotional canvas of human screams: Patterns and acoustic cues in the perceptual categorization of a basic call type. 55
Abstract 56
Methods 61
Participants 61
Stimuli 62
Procedure. 65
Analysis 66
Results 70
Overall ratings and agreement 70
Correlations between emotion ratings 72
Acoustic predictors of emotion ratings 73
Ratings as a function of source contexts 78
Discussion. 79
Agreement and perceptual dimensions 79
Acoustic predictors of emotion perception. 81
Accuracy and the case of happiness 85
References 88
CHAPTER III. Emotion-related variation in simple speech extends to screams: Implications for human nonverbal communication. 92
Abstract 93
Methods 107
Participants 107
Stimuli 108
Experimental procedure. 110
Acoustic analysis 113
Statistical analysis 115
Results 120
Emotion Categorization. 120
Acoustic differences between emotions 125
Perceptual effects ratings 131
Listener-classified screams 134
Discussion. 137
Emotion categorization of screams and speech. 137
Perceptual effects of screams 144
Screams as a call type. 149
References 154
CHAPTER IV. General Discussion. 161
Contextual diversity and variation within call types 163
Call function and emotional communication. 166
Human call types and language. 170
References 173
APPENDIX.. 176
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