ABSTRACT
Perhaps the most distinguishing features of psychological approaches to the study of human development are the assumption of underlying continuities between behaviours at different points in the lifespan, and the attempt to understand how interactions between the individual and the environment at one point in time make possible more elaborate interactions at some later point in time. A simple example concerns the question of continuities between early motor abilities, such as crawling and reaching, and later, more sophisticated abilities, such as walking and pointing. Needless to say, when developmental psychologists are studying language, the ‘environment’ includes not only the physical environment provided by objects and materials, but also the social environment provided by other people.
