Multimodality in infancy: vocal-motor and speech-gesture coordinations in typical and atypical development.

From very early in life, expressive behavior is multimodal, with early behavioral coordinations being refined and strengthened over time as they become used for the communication of meaning. Of these communicative coordinations, those that involve gesture and speech have received perhaps the greatest empirical attention, but little is known about the developmental origins of the gesture-speech link. One possibility is that the origins of speech-gesture coordinations lie in hand-mouth linkages that are observed in the everyday sensorimotor activity of very young infants who do not yet use the hand or mouth to communicate meaning. In this article, I review evidence suggesting that the study of gesture-speech links and developmentally prior couplings between the vocal and motor systems in infancy can provide valuable insight into a number of later developments that reflect the cognitive interdependence of gesture and speech. These include aspects of language development and delay, the infant origins of the adult speech-gesture system, and early signs of autism spectrum disorder. Implications of these findings for studying the development of multimodal communication are considered.