The ability to distinguish words within an apparently continuous stream of speech is a crucial step for infants in learning to speak themselves. This book examines the initial capacities that infants possess for discriminating and categorizing speech sounds and how these capacities evolve as infants gain experience with native language input. Attention is paid to the ways that speech perception capacities develop in very young children. Jusczyk also looks at how infants' growing knowledge of native language sound patterns may facilitate the acquisition of other aspects of language organization, and he discusses the relationship between the learner's developing capacities for perceiving and producing speech. One of the first efforts to integrate the field of infant speech perception research into the general study of language acquisition, the book fills in a key part of the acquisition story by providing an extensive review of research on the acquisition of language during the first year of life, focusing primarily on how normally developing infants learn the organization of native language sound patterns. An appendix reviews the test procedures used to evaluate infant speech perception capacities.