Acoustic, emotional, and perceptual variation in human screams: Exploring the diversity in a basic call type Open Access

Engelberg, Jonathan (Summer 2021)

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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


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


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