Abstract

Asif A. Ghazanfar,1,3,* Hjalmar K. Turesson,1,3 statistical pattern recognition [16, 17] and psychophys- Joost X. Maier,1 Ralph van Dinther,2 ics [13, 18–23] have suggested that formants are signif- Roy D. Patterson,2 and Nikos K. Logothetis1 icant contributors to these indexical cues. It is likely, 1Max Planck Institute for Biological Cybernetics then, that detecting formants could have provided 72076 Tuebingen ancestral primates with indexical cues necessary for Germany navigating the complex social interactions that are the 2Centre for the Neural Basis of Hearing essence of primate societies. One important indexical Department of Physiology cue is body size. Formant cues related to body size University of Cambridge could be used by monkeys to determine the sex (in sex- CB2 3EG Cambridge ually dimorphic species), degree of potential threat (e.g., United Kingdom whether a competitor is larger or smaller), and/or age of an individual, as such cues do for human listeners [13, 18, 20, 21]. Summary Formants are the result of acoustic filtering by the supralaryngeal vocal tract—the nasal and oral cavities Vocal-tract resonances (or formants) are acoustic sigabove the vocal folds. During vocal production, pulses natures in the voice and are related to the shape and of air generated by the rapid movement of the vocal length of the vocal tract. Formants play an important folds produce an acoustic signal. The frequency of these role in human communication, helping us not only to pulses—the glottal-pulse rate—determines the fundadistinguish several different speech sounds [1], but mental frequency of the signal, which in turn is perceived also to extract important information related to the as pitch. As the signal passes through the supralaryngphysical characteristics of the speaker, so-called ineal vocal tract, it excites resonances, resulting in the dexical cues. How did formants come to play such an enhancement of particular frequency bands; these are important role in human vocal communication? One the formants..