Human vocal communication of body size

Abstract

The human voice may convey meaningful information about socially and evolutionarily relevant characteristics of the vocalizer. In turn, listeners may readily evaluate personal characteristics, such as body size, on the basis of nonverbal voice features. Research investigating vocal communication of physical size in humans has focused on two salient and largely independent voice features, fundamental frequency and/or corresponding harmonics (perceived as voice pitch) and formant frequencies (resonance frequencies of the supralaryngeal vocal tract). However, the degree to which fundamental and formant frequencies reliably predict variation in body size controlling for sex and age, and their relative role in the perception or accurate estimation of body size, has to date been unclear. In the current thesis, using meta-analysis, I establish that formants reliably predict variation in men’s and women’s heights and weights. In contrast, fundamental frequency only weakly predicts men’s heights and women’s weights. These findings corroborate work on many other mammals whose vocal production, like humans, follows the source-filter model. Despite the lack of a robust physical relationship between fundamental frequency and size within sexes, I further demonstrate that listeners utilize voice pitch to accurately gauge men’s relative height. My research suggests that voice pitch indirectly facilitates accurate size assessment by providing a carrier signal (i.e., dense harmonics) for formants. This is the first evidence that pitch does not confound accurate size estimation. Finally, I demonstrate that voices with lowered pitch, but not raised pitch, are perceived as larger when projected from a low than high spatial location. These results suggest that strong cross-modal perceptual biases linking low pitch to low elevation and large size may, in some contexts, cause errors in size estimation. Taken together, this thesis provides a detailed account of human vocal communication of body size, which can play a meaningful role in sexual and social contexts.