Vocal indicators of body size in men and women: a meta-analysis Katarzyna Pisanski a , Paul J. Fraccaro a , Cara C. Tigue a , Jillian J. M. O'Connor a , Susanne R € oder b, c, d , Paul W. Andrews a , Bernhard Fink b, c , Lisa M. DeBruine e , Benedict C. Jones e , David R. Feinberg a, * a Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, ON, Canada b Institute of Psychology, University of G€ ottingen, G€ ottingen, Germany c Courant Research Centre Evolution of Social Behavior, University of G€ ottingen, G€ ottingen, Germany d Department of General Psychology and Methodology, University of Bamberg, Bamberg, Germany e Institute of Neuroscience and Psychology, University of Glasgow, Glasgow, U.K. article info Article history: Received 31 January 2014 Initial acceptance 16 April 2014 Final acceptance 4 June 2014 Published online MS. number: A14-00100R Keywords: bioacoustics formant fundamental frequency height human sexual selection source filter vocal tract voice weight Animals often use acoustical cues, such as formant frequencies, to assess the size of potential mates and rivals. Reliable vocal cues to size may be under sexual selection. In most mammals and many other ver- tebrates, formants scale with vocal tract length allometrically and predict variation in size more reliably than fundamental frequency or pitch (F0). In humans, however, it is unclear from previous work how well voice parameters predict body size independently of age and sex. We conducted a meta-analysis to establish the strength of various voiceesize relationships in adult men and women. We computed mean weighted correlations from 295 coefficients derived from 39 independent samples across five continents, including several novel and large cross-cultural samples from previously unpublished data. Where possible, we controlled for sample size, sample sex, mean age, geographical location, study year, speech type and measurement method, and ruled out publication bias. Eleven of 12 formant-based vocal tract length (VTL) estimates predicted men's and women's heights and weights significantly better than did F0. Individual VTL estimates explained up to 10% of the variance in height and weight, whereas F0 explained less than 2% and correlated only weakly with size within sexes. Statistically reliable size estimates from F0 required large samples of at least 618 men and 2140 women, whereas formant-based size estimates required samples of at least 99 men and 164 women. The strength of voiceesize relationships varied by sample size, and in some cases sex, but was largely unaffected by other demographic and methodological variables. We confirm here that, analogous to many other vertebrates, formants provide the most reliable vocal cue to size in humans. This finding has important implications for honest signalling theory and the capacity for human listeners to estimate size from the voice. © 2014 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. Among most terrestrial mammals, including humans, the voice is produced by the larynx and subsequently filtered by the supra- laryngeal vocal tract (henceforth, vocal tract; Titze, 1994). The vocal folds within the larynx vibrate to produce the fundamental fre- quency (F0) and corresponding harmonics that are perceived as voice pitch, whereas formants are the resonant frequencies of the vocal tract. Because of relatively minimal feedback of vocal tract energy on vocal fold vibration, the source-filter model of speech production treats F0 and formants as anatomically and functionally independent (Fant, 1960; Titze, 1994). Source-filter theory was originally developed by speech scien- tists (Fant, 1960; Singh & Singh, 1976; Titze, 1994), but has since been applied to the study of nonhuman vocalizations (see, e.g. Fitch & Hauser, 1995, 2003; Ohala, 1983; Owren & Bernacki, 1998; Owren, Seyfarth, & Cheney, 1997; Rendall, Owren, & Rodman, 1998; Sommers, Moody, Prosen, & Stebbins, 1992; Taylor & Reby, 2010). Research has confirmed that F0 and formants are decou- pled in most vertebrates by showing that changes in F0 and for- mants do not covary in heliox, a mixture of helium and oxygen that transmits sound twice as fast as does air. In a coupled vocal system, heliox causes both F0 and formants to shift upward, whereas in a decoupled system, only formants shift upward due to a shortened transit time of sound waves traveling up the vocal tract (Hess et al., 2006). Decoupling has been demonstrated in several species of birds, anurans, bats and many mammalian species including humans (see Fitch & Hauser, 2003). * Correspondence: D. R. Feinberg, Department of Psychology, Neuroscience & Behaviour, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada. E-mail address: feinberg@mcmaster.ca (D. R. Feinberg). Contents lists available at ScienceDirect Animal Behaviour journal homepage: www.elsevier.com/locate/anbehav http://dx.doi.org/10.1016/j.anbehav.2014.06.011 0003-3472/© 2014 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. Animal Behaviour 95 (2014) 89e99