Learning and representation in speech and language.

Infants learn language with remarkable speed. By the end of their second year they speak in sentences with an 'accent' typical of a native speaker. How does an individual acquire a specific language? While acknowledging the biological preparation for language, this review focuses on the effects of early language experience on infants' perceptual and perceptual-motor systems. The data show that by the time infants begin to master the higher levels of language--sound-meaning correspondences, contrastive phonology, and grammatical rules--their perceptual and perceptual-motor systems are already tuned to a specific language. The consequences of this are described in a developmental theory at the phonetic level that holds promise for higher levels of language.