You will have gathered by now that the driving force behind the usage-based approach to language development is Michael Tomasello. His homepage provides an excellent source of recent, downloadable research reports on child language. Tomasello has wide research interests, so you will also come across interesting comparative research on communication in chimpanzees (relevant to chapter 2).
Cynthia Fisher is a leading exponent of syntactic bootstrapping, a theory which ascribes a relatively sophisticated level of syntactic knowledge to children by the age of 24 months. This work therefore provides a direct challenge to the usage-based belief that early child speech is not based on productive, adult-like syntactic generalizations. If the URL defeats you, Google Cynthia Fisher and you’ll get there quite soon.