This book is dedicated to Jaap Kruijt. His pioneering approach to the study of the causal mechanisms of behavioural development has inspired many, as is obvious in many of the contributions to this volume. We have both had the pleasure of working with him, as postdoctoral fellow and as doctoral student, respectively. Chapters in this book were commissioned from a wide range of scientists interested in behavioural development. Some of these have been former students or colleagues of Jaap Kruijt, but many are workers in the field with interests and approaches that are compatible with the approach Kruijt has taken to development. Each author was asked to review a specific area of the field in such a way that we think almost all the important conceptual and empirical advances in the study of development have been covered in one chapter or another. A special feature of the approach taken here is that learning, as studied by experimental psychologists, is considered to be one process contributing to the development of the individual from conception to death. Learning is seen to play an important part in development in several chapters in the book, and the relation of learning to other developmental processes is discussed specifically in the last three.

We are grateful to Bob Lockhart and Rob Honey who have read several of the chapters in manuscript form and commented on them.