Humans read emotional arousal in monkey vocalizations: evidence for evolutionary continuities in communication

• Type of Material: Article
• Authors: Jay W Schwartz, Emory University; Harold Gouzoules, Emory University
• Language: English
• Date: 2022-12-01
• Publisher: PeerJ Inc.
• Publication Version: Final Published Version
• Copyright Statement: © 2022 Schwartz and Gouzoules
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.7717/peerj.14471
• Title of Journal or Parent Work: PeerJ
• Volume: 10
• Grant/Funding Information: This study was supported by the U.S. National Science Foundation Graduate Research Fellowship under Grant No. DGE – 1343012, by the U.S. National Institutes of Health (NIH) Grant Number 1R01HD077623 and the NIH Office of the Director, Office of Research Infrastructure Programs, P51OD011132 (Emory National Primate Research Center-ENPRC-base grant). The ENPRC is fully accredited by AAALAC, International. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
• Keywords: Emotion; Scream; Nonverbal; Primate; Arousal; Evolution; Macaca mulatta; Empathy; Vocal communication; Acoustics

Abstract

Humans and other mammalian species communicate emotions in ways that reflect evolutionary conservation and continuity, an observation first made by Darwin. One approach to testing this hypothesis has been to assess the capacity to perceive the emotional content of the vocalizations of other species. Using a binary forced choice task, we tested perception of the emotional intensity represented in coos and screams of infant and juvenile female rhesus macaques (Macaca mulatta) by 113 human listeners without, and 12 listeners with, experience (as researchers or care technicians) with this species. Each stimulus pair contained one high- and one low-arousal vocalization, as measured at the time of recording by stress hormone levels for coos and the degree of intensity of aggression for screams. For coos as well as screams, both inexperienced and experienced participants accurately identified the high-arousal vocalization at significantly above-chance rates. Experience was associated with significantly greater accuracy with scream stimuli but not coo stimuli, and with a tendency to indicate screams as reflecting greater emotional intensity than coos. Neither measures of empathy, human emotion recognition, nor attitudes toward animal welfare showed any relationship with responses. Participants were sensitive to the fundamental frequency, noisiness, and duration of vocalizations; some of these tendencies likely facilitated accurate perceptions, perhaps due to evolutionary homologies in the physiology of arousal and vocal production between humans and macaques. Overall, our findings support a view of evolutionary continuity in emotional vocal communication. We discuss hypotheses about how distinctive dimensions of human nonverbal communication, like the expansion of scream usage across a range of contexts, might influence perceptions of other species’ vocalizations.