A fresh synthesis of ideas and findings has recently emerged across the several areas of developmental investigation. As indicated in Chapter 1, this synthesis employs concepts that have issued from longitudinal investigations, life-course studies of contextual change, cognitive development, and developmental psychobiology. Consistent with the collaborative statement, the stuff of development is seen as arising from the dynamic interrelations among systems that exist within and without persons. A nuclear principle of this holistic framework of development is that “the individual is an active, purposeful part of an integrated, complex and dynamic personenvironment system. A consequence of this view is that it is not possible to understand how social systems function without knowledge of individual functioning, and it is not possible to understand individual functioning and development without knowledge of the environment” (Magnusson & Stattin, in press). Accordingly, development is not simply a property of individuals – social interactions develop, communities change, and societies evolve. In this chapter, we summarize some principles that provide a bridge between the conceptual framework of developmental science and the concrete methods required for the conduct of developmental research.

In the consensus statement in Chapter 1, we observed that “recognizing the complexity of development is the first step toward understanding its coherence and simplicity”. The problem has been that it has been difficult for researchers to move beyond the first step. Accordingly, the holistic perspective described in the collaborative statement presupposes multidisciplinary methods and multilevel measures.