This book is an excellent introduction to the field of child language development. It demonstrates the need for both a theory of language development and reliable speech and comprehension data in child language research. As Foster-Cohen states in the preface to the book, the adoption of only a single approach, as opposed to a combination of different approaches, is unlikely to lead to a productive understanding of child language acquisition. The book successfully adopts the perspectives of both the empiricist and the rationalist traditions in its treatment of key issues.