Visual and sensori-motor influences on speech perception in infancy

Speech perception is multisensory and is comprised not only of auditory information, but also of visual (Burnham and Dodd, 2004; Kuhl and Meltzoff, 1984; Patterson and Werker, 2003) and proprioceptive motor information (Yeung and Werker, 2013). Building on previous studies examining perceptual attunement in young infants (Werker and Tees, 1984, inter alia), this set of experiments examines the role that vision and motor proprioception play during the perception of auditory speech sounds. In the first experiment, the developmental trajectory of perceptual attunement in English-learning infants is again explored using the dental-retroflex contrast of Hindi. We replicate the finding that English-learning 6-month-olds are able to discriminate auditory-only dental and retroflex stimuli, while English-learning 10-month-olds are not. In the second experiment, looking time measurements are used to explore the possibility that the addition of dynamic visual information acts as a perceptual anchor, now permitting discrimination of this same non-native contrast by 10-month-old infants. Finally, in the third experiment, we investigate the role of a temporary motor manipulation, designed to prevent relevant movement of the tongue in 6- and 10-month-old English infants during perception of the non-native Hindi contrast, to determine the effect of proprioceptive, sensori-motor mechanisms in auditory speech perception across development.