Adaptations in humans for assessing physical strength from the voice

Abstract

Recent research has shown that humans, like many other animals, have a specialization for assessing fighting ability from visual cues. Because it is probable that the voice contains cues of strength and formidability that are not available visually, we predicted that selection has also equipped humans with the ability to estimate physical strength from the voice. We found that subjects accurately assessed upper-body strength in voices taken from eight samples across four distinct populations and language groups: the Tsimane of Bolivia, Andean herder-horticulturalists and United States and Romanian college students. Regardless of whether raters were told to assess height, weight, strength or fighting ability, they produced similar ratings that tracked upper-body strength independent of height and weight. Male voices were more accurately assessed than female voices, which is consistent with ethnographic data showing a greater tendency among males to engage in violent aggression. Raters extracted information about strength from the voice that was not supplied from visual cues, and were accurate with both familiar and unfamiliar languages. These results provide, to our knowledge, the first direct evidence that both men and women can accurately assess men's physical strength from the voice, and suggest that estimates of strength are used to assess fighting ability.

Three-month-old human infants use vocal cues of body size

“…For example, lowering of F n and/or F 0 in dog barks increases attributions of the dog's aggressiveness in human listeners [20]. Playback studies with male deer vocalizations also show that male deer perceive the experimental lowering of F n and F 0 as more threatening ( [21]; see also [9,11,16,22,23] for more extensive reviews). Adult domestic dogs also correctly match the growls of larger versus smaller dogs onto visual cues of dog body size [24].…”

“…Previous experimental evidence demonstrates that human adults are sensitive to these relationships, even within age and sex morphs [11,[16][17][18]. For instance, experimentally lowering F 0 and formant dispersion in young men's voices increases the speaker's perceived masculinity, size and age [19].…”

“…Because this relationship is robust and recurrent across taxa, and presumably phylogenetic time, natural selection may have shaped developmental processes to capture this invariance relatively early in ontogeny, as a means of building a reliably developing phenotype capable of identifying and representing an organism's size, sex, and/or life-stage via acoustic as well as visual channels. Further, because transient fitness-relevant states and behavioural intentions-such as attack versus friendly approach-are often individual-specific and signalled through vocalization content [16,25,26], this is potentially also a mechanism for reducing uncertainty in matching vocalizations to the entities producing them [27].…”

A psycho-ethological approach to social signal processing

“…For example, a posture that facilitates the assessment of body size can be considered as an index. Body size is a cue to physical strength (Sell et al 2010) and can be enhanced by an erect posture, like the one usually observed in the expression of pride (Tracy and Robins 2004). In this case, perceived body size is increased but within the limits offered by the actual size of legs and chest.…”

Sexual Selection and Life History: Earlier Recalled Puberty Predicts Men’s Phenotypic Masculinization

“…We used a tailor's tape to measure the circumference of participants' right and left flexed biceps at the widest points (see Table 1 for descriptive statistics). Flexed biceps circumference and hand strength are strong predictors of upper body strength (Sell et al 2010); for example, flexed biceps circumference accounts for approximately 50 % of the variation in upper body lifting ability (Sell et al 2009). …”