The question of why language acquisition is not instantaneous is addressed in terms of two related issues: the logical and the developmental aspects of language acquisition. The role of linguistic theory and research in determining the interplay of these two aspects of grammatical development is examined. It is suggested that the…

Outside the core grammar, the set of "peripheral" or marked properties of a language include exceptions or relaxations of the settings of core grammar and the idiosyncratic features of the language governed by particular lexical items. The core/peripheral distinction has direct implications for grammatical development in children. The…