This book offers an interdisciplinary perspective on verb argument structure and its role in language acquisition. Much contemporary work in linguistics and psychology assumes that argument structure is strongly constrained by a set of universal principles, and that these principles are innate, providing children with certain “bootstrapping” strategies that help them home in on basic aspects of the syntax and lexicon of their language. Drawing on a broad range of crosslinguistic data, this volume shows that languages are much more diverse in their argument structure properties than has been realized. This diversity raises challenges for many existing proposals about language acquisition, affects the range of solutions that can be considered plausible, and highlights new acquisition puzzles that until now have passed unnoticed. The volume is the outcome of an integrated research project and comprises chapters by both specialists in first language acquisition and field linguists working on a variety of lesser-known languages. The research draws on original fieldwork and on adult data, child data, or both from thirteen languages from nine different language families. Some chapters offer typological perspectives, examining the basic structures of a given language with language-learnability issues in mind. Other chapters investigate specific problems of language acquisition in one or more languages. Taken as a whole, the volume illustrates how detailed work on crosslinguistic variation is critical to the development of insightful theories of language acquisition.