From the time of birth through the early school years, young children rapidly acquire two complex cognitive systems: They organize their experiences into concepts and categories, and they acquire their first language. How do children accomplish these critical tasks? How do conceptual systems influence the structure of the language we speak? How do linguistic patterns influence how we view reality? These questions have captured the interest of such theorists as Piaget, Vygotsky, Chomsky and Whorf but until recently very little has been known about the relation between language and thought during development. Perspectives on Language and Thought presents current observational and experimental research on the links between thought and language in young children. Chapters from leading figures in the field focus on the acquisition of hierarchical category systems, concepts of time, causality, and logic and the nature of language learning in both peer and adult-child social interactions.