Research on first language acquisition has typically focused on characterizing children's linguistic competence at specific time points. While this research is of critical importance, it provides little insight about how transitions between the time points arises, or about how knowledge of language interacts with more general cognitive processes in the course of sentence processing. Both of these issues have recently been receiving more attention, by means of research demonstrating how children's performance on linguistic tasks varies even after adultlike competence has been established. In this talk, I will consider research on children's interpretations of linguistic dependencies and discuss how non-adultlike behavior can help us understand the role of non-adultlike performance systems in language acquisition.