title: The evolution of speech: vision, rhythm, cooperation.
abstract: A full account of human speech evolution must consider its multisensory, rhythmic, and cooperative characteristics. Humans, apes, and monkeys recognize the correspondence between vocalizations and their associated facial postures, and gain behavioral benefits from them. Some monkey vocalizations even have a speech-like acoustic rhythmicity but lack the concomitant rhythmic facial motion that speech exhibits. We review data showing that rhythmic facial expressions such as lip-smacking may have been linked to vocal output to produce an ancestral form of rhythmic audiovisual speech. Finally, we argue that human vocal cooperation (turn-taking) may have arisen through a combination of volubility and prosociality, and provide comparative evidence from one species to support this hypothesis.
authors.affiliation: Princeton Neuroscience Institute, Departments of Psychology and Ecology & Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA. Electronic address: asifg@princeton.edu.
authors.forename: Asif A
authors.initials: AA
authors.lastname: Ghazanfar
authors.affiliation: Princeton Neuroscience Institute, Department of Psychology, Princeton University, Princeton, NJ 08544, USA.
authors.forename: Daniel Y
authors.initials: DY
authors.lastname: Takahashi
mesh_terms: D000818:Animals; D005075:Biological Evolution; D003299:Cooperative Behavior; D005149:Facial Expression; D006801:Humans; D007398:Interpersonal Relations; D046709:Pattern Recognition, Physiological; D010507:Periodicity; D013060:Speech / Q000502:physiology*; D014785:Vision, Ocular / Q000502:physiology*; D014828:Vocalization, Animal