Efficacy in deceptive vocal exaggeration of human body size

Abstract

How can deceptive communication signals exist in an evolutionarily stable signalling system? To resolve this age-old honest signalling paradox, researchers must first establish whether deception benefits deceivers. However, while vocal exaggeration is widespread in the animal kingdom and assumably adaptive, its effectiveness in biasing listeners has not been established. Here, we show that human listeners can detect deceptive vocal signals produced by vocalisers who volitionally shift their voice frequencies to exaggerate or attenuate their perceived size. Listeners can also judge the relative heights of cheaters, whose deceptive signals retain reliable acoustic cues to interindividual height. Importantly, although vocal deception biases listeners’ absolute height judgments, listeners recalibrate their height assessments for vocalisers they correctly and concurrently identify as deceptive, particularly men judging men. Thus, while size exaggeration can fool listeners, benefiting the deceiver, its detection can reduce bias and mitigate costs for listeners, underscoring an unremitting arms-race between signallers and receivers in animal communication.

Singers show enhanced performance and neural representation of vocal imitation.

“…We showed that both singers and controls can volitionally modulate vocal parameters in a goal-directed fashion to imitate voices of different sizes and pitches, in line with previous work investigating volitional vocal size exaggeration [16][17]. Specifically, we showed that both groups adjusted F0 downward and upward to imitate lower-and higher-pitched voice targets, respectively and, for the first time, we also showed that modulations to imitate longer and shorter VTLs were achieved via appropriate upward and downward movements of the larynx in the vocal tract.…”

“…A region of left somatomotor cortex identified in the whole participant group did not correspond topographically to previous reports of the larynx motor cortex (LMC). However, a further direct comparison of singers and controls revealed an expertise-related enhancement of VTL representation in right somatosensory cortex, just posterior to the reported location of the dorsal LMC in humans [16][17][18] and in line with a postcentral site previously linked to singing experience [33][34][35]. We speculate that this dorsal site could represent a larynx sensory cortex that is closely coupled to its corresponding LMC during speech motor control [9]: in line with this, probabilistic diffusion tractography analyses of LMC connectivity have revealed dramatically stronger connectivity with somatosensory and inferior parietal cortices in humans than in macaques [46].…”

“…∆F is related to the resonant properties of the vocal tract and covaries negatively with vocal tract length (VTL) -thus, adults show lower ∆F than children (whose vocal tracts are typically shorter), and adult male voices typically have lower ∆F than adult female voices due to the secondary descent of the larynx during puberty in human males. Previous research on speech acoustics has shown that humans can readily modulate ∆F in the appropriate direction when attempting to sound larger/smaller [16][17].…”

“…The ability to modulate the voice is potentially adaptive for individuals. For example, vocal size exaggeration is effective in changing listeners' evaluations of talker height [17], which may provide advantages in competitive situations. Furthermore, recent evidence on social trait expression has shown that talkers can volitionally modulate their speaking voice to generate exaggerated impressions of specific traits in naïve listeners [21].…”

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

“…In humans, in addition to a permanently descended larynx [7], men and women in diverse cultures can effectively exaggerate their size by volitionally lowering their vocal tract resonances (formants) as well as their fundamental frequency ( f 0 , perceived as voice pitch) [3,8]. In turn, human listeners systematically associate low voice pitch with a large size and physical prowess [9,10].…”