We have seen that aspects of phonology, syntax and semantics develop separately and in parallel, beginning in the first twelve months of life, appearing to cohere with the architecture of the Language Faculty in figure 2.2. The development of language and the development of thought appear to proceed independently, though interactively. We have also seen that many questions remain regarding how different components of knowledge interact in language acquisition as it proceeds over time. How does language “grow” over time? Debates persist: does language development involve qualitative changes in the structure of children's language knowledge or in their computational mechanisms, e.g., is language acquisition analogous to a discontinuous “tadpole-to-frog”-like development, or do children continuously employ formal analyses?

This chapter will focus on mechanisms of developmental change especially after the first twelve months. It will briefly introduce several areas where significant cross-linguistic variation in adult grammars exists and where language development is delayed; here language acquisition must involve some induction. It will briefly introduce several proposed mechanisms of growth. If language acquisition involves continuous linguistic computation, as previous chapters have suggested, then such mechanisms of growth will involve continuous linguistic computation by children. If the architecture of the Language Faculty is in place continuously, then children will not be forced to resort solely to general non-linguistic conceptual means, even at early periods.