Proceedings of the Annual Meeting of the Cognitive Science Society

What is it about a child's linguistic competence that changes during syntactic development? Within the principles and parameters framework of Chomsky (1981), a child's grammar differ from an adult's in having different settings for certain parameters. The process of acquisition, under this view, consists of the sequence of parameter vectors which the child entertains as hypothesis grammars. If at some point in acquisition a parameter which is relevant for a particular construction is incorrectly set, the child will be unable to perform an adult-like analysis. While this view provides an answer to the "logical problem of language acquisition" it fails to explain why certain developmental stages exist. Beyond stipulated orderings of parameter settings, there is little that can be said in this framework to truly explain the time course of acquisition. In this paper, I argue that the stages of syntactic acquisition can be understood as deriving from an increase in the child's ability to handle granunatical complexity. I consider a number of wellattested acquisitional difficulties in a range of seemingly disparate aspects of syntax: relative clauses, control and verbal morphology. Using the formal system of Tree Adjoining Grammar (TAG), I show h o w the single hypothesis that children lack the ability to perform the T A G operation of o^/ommg relates these difficulties in a novel way, and provides us with a n ew type of explanation for the time course of syntactic development in terms of the complexity of formal grammatical devices.