ABSTRACT
The book that, more than any other, provoked us into thinking and theorizing in terms of age-related change is Jack Wohlwill’s (1973) classic, The Study of Behavioral Development. This book made clear as no other before that within psychology there are three fundamental approaches: the experimental, the differential and the developmental. The first approach tries to ascertain the causes of behaviour through experimental manipulation; the second systematically details and attempts to explain natural individual differences; and the third focuses on the development of behaviour – on the nature of psychological changes in childhood and adolescence. The history of psychology and the nature of current research clearly demonstrate that these three approaches cannot be reduced to a single common denominator. Instead, they complement each other and, together, form the ‘trinity of human behavioural science’. The study of individual differences and the study of causes are of a fundamentally different character when applied to developmental studies – something we hope to make clear in the following pages. Since our own research concentrates on the development of aggression, we discuss this in relation to its links with anti-social behaviour and youth offending. We begin with a discussion of the concept of causality in developmental theory.
