Introduction: developing theories of speech perception - constraints from developmental data, Judith C. Goodman et al. Part 1 Innate sensory mechanisms and constraints on learning: observations on speech perception, its development, and the search for a mechanism, Joanne L. Miller and Peter D. Eimas the importance of childhood to language acquisition - evidence from American sign language, Rachel I. Mayberry. Part 2 Perceptual learning of phonological systems: cross-language speech perception - developmental change does not involve loss, Janet F. Werker perceptual learning of non-native speech contrasts - implications for theories of speech perception, David B. Pisoni et al the emergence of native-language phonological influences in infants - a perceptual assimilation model, Catherine T. Best. Part 3 Interactions of linguistic levels - influences on perceptual development: infant speech perception and the development of the mental lexicon, Peter W. Jusczyk sentential processes in early child language - evidence from the perception and production of function morphemes, LouAnn Gerken learning to hear speech as spoken language, Howard C. Nusbaum and Judith C. Goodman.