This chapter, to be included in "Carmichael's Manual of Child Psychology," edited by P.A. Mussen, deals with the connection between the acquisition of language and the growth of intellect, and the connection between both of these and the process of maturation. The author feels that various theories of development cannot account for the child's acquisition of grammar in a relatively short time, and he discusses the reasons as well as the lines which the explanation must follow. The bulk of the chapter is a survey of language acquisition itself. It is organized under three major headings, one for each of the three main components of a grammar: syntax, phonology, and semantics. A description of the methods typically used in studying the development of each component is given. The emergence of the components themselves is traced (insofar as it is known), and a discussion of various theoretical issues in the light of the empirical findings is presented. Wherever possible, mention is made of children exposed to languages other than English, with the chief contrast languages being Russian and Japanese. (See related document ED 017 921.) (DO)