Pii: S0010-0277(99)00069-4

Many developmental psycholinguists assume that young children have adult syntactic competence, this assumption being operationalized in the use of adult-like grammars to describe young children's language. This ``continuity assumption'' has never had strong empirical support, but recently a number of new ®ndings have emerged both from systematic analyses of children's spontaneous speech and from controlled experiments that contradict it directly. In general, the key ®nding is that most of children's early linguistic competence is item based, and therefore their language development proceeds in a piecemeal fashion with virtually no evidence of any system-wide syntactic categories, schemas, or parameters. For a variety of reasons, these ®ndings are not easily explained in terms of the development of children's skills of linguistic performance, pragmatics, or other ``external'' factors. The framework of an alternative, usage-based theory of child language acquisition relying explicitly on new models from Cognitive-Functional Linguistics is presented. q 2000 Elsevier Science B.V. All rights reserved.