INTRODUCTION

Scientific interest in the longitudinal approach to ontogenetic development dates back to the eighteenth century (Bakes & Nesselroade, 1979), but it has never really become a consistent feature of research in child development. This state of affairs is hardly surprising as the practical and methodological difficulties associated with longitudinal research on human development constitute a formidable barrier. These difficulties (Fletcher, Satz & Morris, 1984) are so numerous and persistent that longitudinal research may easily become a rocky road to disillusionment. In our opinion, however, practical problems are not the only nor even the main reasons for the dearth of longitudinal studies on motor development. In no small measure this is due to the nature of prevalent theoretical persuasions in general and the scarcity of clearly articulated concepts in particular. After all, the first research step required is the formulation of theoretically meaningful questions and not, one hopes, the selection of a methodology. The type of longitudinal methodology employed is to a large extent determined by the nature of developmental theory.

This chapter focuses on a number of conceptual issues that can be best addressed by longitudinal research. Specifically, we address the question of how longitudinal research can contribute to a better understanding of the mechanisms involved in developmental transitions. Such research will have a crucial role to play in examining any theory of developmental transitions as it is the only means of providing a direct test of hypotheses about this phenomenon (see Woollacott, Chapter 6; Connolly and Dalgleish, Chapter 12, this volume).