Learning to match auditory and visual speech cues: social influences on acquisition of phonological categories.

Infants' language exposure largely involves face-to-face interactions providing acoustic and visual speech cues but also social cues that might foster language learning. Yet, both audiovisual speech information and social information have so far received little attention in research on infants' early language development. Using a preferential looking paradigm, 44 German 6-month olds' ability to detect mismatches between concurrently presented auditory and visual native vowels was tested. Outcomes were related to mothers' speech style and interactive behavior assessed during free play with their infant, and to infant-specific factors assessed through a questionnaire. Results show that mothers' and infants' social behavior modulated infants' preference for matching audiovisual speech. Moreover, infants' audiovisual speech perception correlated with later vocabulary size, suggesting a lasting effect on language development.