Harsh is large: nonlinear vocal phenomena lower voice pitch and exaggerate body size

Abstract

A lion's roar, a dog's bark, an angry yell in a pub brawl: what do these vocalizations have in common? They all sound harsh due to nonlinear vocal phenomena (NLP)—deviations from regular voice production, hypothesized to lower perceived voice pitch and thereby exaggerate the apparent body size of the vocalizer. To test this yet uncorroborated hypothesis, we synthesized human nonverbal vocalizations, such as roars, groans and screams, with and without NLP (amplitude modulation, subharmonics and chaos). We then measured their effects on nearly 700 listeners' perceptions of three psychoacoustic (pitch, timbre, roughness) and three ecological (body size, formidability, aggression) characteristics. In an explicit rating task, all NLP lowered perceived voice pitch, increased voice darkness and roughness, and caused vocalizers to sound larger, more formidable and more aggressive. Key results were replicated in an implicit associations test, suggesting that the ‘harsh is large’ bias will arise in ecologically relevant confrontational contexts that involve a rapid, and largely implicit, evaluation of the opponent's size. In sum, nonlinearities in human vocalizations can flexibly communicate both formidability and intention to attack, suggesting they are not a mere byproduct of loud vocalizing, but rather an informative acoustic signal well suited for intimidating potential opponents.

Nonlinear vocal phenomena affect human perceptions of distress, size and dominance in puppy whines

“…Increasing the duration of subharmonics further increased perceived size and dominance. These results are consistent with recent work on human nonverbal vocalizations [18,32]. Our results also confirm the well-established perceptual effect of f o on size and dominance [45][46][47]-whines with a relatively low f o were systematically perceived as produced by larger and more dominant-sounding puppies, independent of the effects of NLP on perceived size and dominance.…”

“…Our results also confirm the well-established perceptual effect of f o on size and dominance [45–47]—whines with a relatively low f o were systematically perceived as produced by larger and more dominant-sounding puppies, independent of the effects of NLP on perceived size and dominance. Although we show that f o directly affects perceptions of size and dominance, we cannot completely rule out the possibility that NLP independently lower the perceived pitch of whines (as they do in human vocalizations) [18]. This pitch-lowering effect may thus be one of the perceptual mechanisms whereby NLP cause puppies to sound larger and more dominant.…”

“…We suggest that bifurcations between the tonal and non-tonal sections of the calls may be less salient in calls with a largely dominant nonlinear regime. In a recent study, we showed that subharmonics and sidebands added to human nonverbal vocalizations lowered their perceived pitch [18]. As such, when exposed to subharmonics or sidebands affecting 80% of the whine duration, listeners may have perceived these calls with a relatively high tonality at a lower f o and may thus have associated these lower-pitched sounds with behavioural contexts of aggression, rather than distress.…”

“…In this context, another hypothesis regarding the potential functions of NLP may be to exaggerate perceived size and dominance [4,5]. Some NLP can indeed lower perceived pitch, enhancing the perceptibility of vocal tract resonances by increasing spectral density, and potentially, may affect perceptions of the vocalizer's size and dominance [4,18]. Together, several hypotheses have thus been put forward regarding the functions of NLP: attention grabbing, communication of distress, and/or size or dominance exaggeration.…”

“…We predicted that NLP added to whines, particularly chaos, would increase human perceptions of the puppy's distress, and that higher proportions of NLP would enhance these perceptual effects. Moreover, because NLP affect perceptions of size and dominance in synthetic human vocalizations [18,32], we tested whether these perceptual effects generalize to other mammal vocalizations. Indeed, dominance-like behaviours have been described as a trait of individual temperament in dogs [36,37], and can occur during the early development of pre-weaned canids, including puppies (e.g.…”