ABSTRACT
Without formal instruction all healthy children acquire a reasonable command of their native language or languages. What do children learn as they do so, and how do they do it? Children acquire their language on the basis of their experience—the speech they hear and what happens when people talk. From this complex of experience children acquire the rules and mechanisms for understanding and producing interpretable speech. During the progression from babbling to adult speech, children develop increasingly complex grammars. This notion represents a departure from the view that children speak a garbled and error-ridden version of adult language. Instead, children’s speech can be characterized at any given level of language development as a rule-governed system. The rules children use at one stage differ systematically from the rules at other stages, and they differ systematically from the rules adults use. Even when children use the rules of adult language, their “mistakes” are not mistakes in the usual sense. For example, when a child says “I goed” instead of “I went,” he is displaying the use of a past-tense rule. The trouble is, of course, that the rule is applied inappropriately. It is overextended to an irregular verb, but it is certainly not applied randomly or nonsystematically.
