Running Head: USING SYNTACTIC PROCESSING AS A DIAGNOSTIC FOR SYNTACTIC KNOWLEDGE Syntactic Processing as a Diagnostic for Syntactic Knowledge: Principle C in 30-month-olds

Thorough investigation of early syntactic knowledge necessitates methodologies that tap young children's linguistic competence while minimizing extra-linguistic demands and not relying on production. The preferential looking paradigm is uniquely suited to such a task. We present here a test case for the exploration of early syntactic knowledge in young children: Principle C effects at 30 months. Our investigation serves two goals: first, to utilize the fine-grained temporal information available in preferential looking data to identify the response pattern to sentences in Principle C contexts. We show that all children at 30 months show adult-like restriction of interpretation in Principle C contexts. Second, we utilize individual variation in the response pattern to identify the underlying knowledge driving this observable behavior. We show that variation in processing speed at the syntactic but not the lexical level predicts speed of interpretation in Principle C contexts. This result not only dissociates empirical measures of lexical and syntactic processing but also highlights the dependency between structural processing and structure-dependent interpretation. This novel use of individual differences at the processing level to probe similarities across a population at the knowledge level represents the development of a critical method for the exploration of syntactic comprehension in young children. The following terms have been abbreviated in the following text: