Human speech and birdsong: Communication and the social brain

要旨

At first glance, communication in babies and birds appears to have little in common. Babies' babblings become words and sentences, whereas birds' initial notes become species-typical songs. However, a comparison of the ontogeny of communicative repertoires in human infants and avian song birds shows striking parallels (1) (Fig. 1). Both species show initial innate predispositions for species-typical signals and have to be exposed to species-typical vocalizations during a sensitive period to acquire them. Both show an initial phase of developmental learning that is primarily perceptual, during which babies and birds commit to long-term memory the detailed characteristics of the communicative repertoires they hear. Both species subsequently use the patterns stored in memory to guide motor production through the process of imitation (2–4). For babies, the task involves committing to memory the phonetic units and prosodic (pitch and intonation) characteristics that typify the mother tongue: Japanese is not French. Birds store the specific notes, syllables, and prosodic characteristics that typify their species. Storing the species-typical patterns is not the end of the task for either species. Both babies and birds must then rehearse and refine their communicative repertoires, actively comparing and gradually matching (through auditory feedback) their productions to the sound patterns stored in auditory memory (5, 6). Fig. 1. Timelines for speech development in infants and song development in birds. Both species show innate predispositions for the perception of species-typical signals, and periods of sensory learning followed by periods of sensory-motor learning. [Reproduced with permission from ref. 1 (Copyright 1999, Annual Reviews).] The article by Goldstein et al. (7) in a recent issue of PNAS provides support for yet another fascinating link between communicative development in babies and birds. Goldstein et al. show that social contingency strongly influences babbling in human infants. Although well established in certain songbirds, …

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