Pitch affects human (Homo sapiens) perception of emotional arousal from diverse animal calls.

Abstract

A growing body of research demonstrates that humans can accurately perceive the emotional states of animals solely by listening to their calls, highlighting shared evolutionary ancestry. Yet, the cognitive and perceptual mechanisms underlying heterospecific emotion perception have remained open to investigation. One hypothesis is that humans rely on simple acoustic heuristics to make such judgments, for example, perceiving higher-pitched calls as reflecting heightened emotional arousal (the "pitch rule"). This could lead to accurate judgments of emotion since in most mammals, as in humans, vocal fundamental frequency (the acoustic determinant of the pitch percept) does objectively correlate with emotional arousal. In the present study, we used digital pitch manipulation to create pairs of animal calls that were perceptually identical except for pitch, and we measured human perceptions of the caller's emotional arousal using an online survey. Calls of six phylogenetically diverse species were included as stimuli. Participants attributed slightly but statistically significantly higher arousal to higher-pitched versions of the same calls. Variation in application of the pitch rule across species was not well explained by familiarity, and prior experience with cats did not significantly predict sensitivity to pitch in cat vocalizations. Cross-species variation also did not align with phylogenetic distance from humans, or the hypothetical usefulness of pitch for making accurate judgments. Thus, the pitch rule may be a "mammalomorphic" heuristic leading to accurate emotion judgments in some taxa and call types and erroneous judgments in others, depending in part on phylogenetic distance and the mechanisms of call production.

Within the sound of trouble: Do humans use pitch to correctly assess emotional arousal across species?

“…In this issue, Schwartz et al (2024) tackle the pitch rule in humans by testing to what extent we use pitch alone to judge emotional arousal across closely and distantly related animal species. Notably, the authors used audio manipulation to study pitch perception across diverse animals: they created different calls that were identical in every detail except for pitch.…”

“…Notably, and somewhat in contrast to previous research (Schwartz & Gouzoules, 2022) raters were least sensitive to pitch when it came to the primate calls which might be attributed to the higher noisiness of the macaque calls compared to some of the other species. The cricket calls in turn were most uniform in nature thus perhaps making the pitch manipulation more salient to the human ear (Schwartz et al, 2024). This would suggest that baseline acoustic structure and perceptual salience may be more important to the applicability of the pitch rule than phylogenetic distance or familiarity with the species.…”

“…The findings of Schwartz et al (2024) open a number of intriguing possibilities for future research: Notably important additional steps would include to further investigate the accuracy of the pitch rule across closely and distantly related species. Upon this, in order to study the evolutionary ancestry of the pitch rule, it will be necessary to study its applicability across nonhumans.…”