For many years, research and theory on language acquisition have been sustained by data on
English language learners, with an occasional crosslinguistic contribution. With more than 5,000
languages currently spoken in the world, we are not even close to a systematic sampling of
languages and language learners. However, current crosslinguistic inquiry motivates much of the
most interesting work in theoretical linguistics, neurolinguistics, and, thanks in large part to Dan
Slobin's multivolume series, language acquisition. Volumes 1, 3, and 4 of The
Crosslinguistic Study of Language Acquisition summarize critical features and the overall
course of development for 25 languages. The chapters in Volume 2 consider theoretical issues
raised by the crosslinguistic evidence. Volume 5 is the most recent publication, and, like Volume
2, its chapters provide a broader perspective on the data. The five chapters of the current volume
attempt to enlarge the all-too-often narrow portrayal of the individual language learner grappling
with the intractable problems of syntax and morphology. The authors review relevant data from
previous volumes and consider how prosody, semantics, and pragmatics can disambiguate syntax
and morphology and how a framework of systematic typological variation is crucial to
understanding just how this might be accomplished.