ABSTRACT
Specialization of training and expertise within contemporary psychology is a necessary consequence of the complexity and rapid expansion of the field. Individual psychologists must specialize in order to attain sufficient depth of knowledge to make an effective contribution to either research or practice. More and more psychologists came to recognize that theory and empirical data must work together in the identification of research problems, in the design of experiments, and in the interpretation of results. The field of life-span developmental psychology is rapidly integrating the well-established traditional fields of child psychology, adolescent psychology, and the psychology of old age. The emergence of a systematically organized field of cross-cultural psychology was preceded by a long period of scattered psychological studies of isolated cultural groups. The hierarchical model is what provides the convergence of the various conflicting theories. One involves the development of comprehensive models, such as hierarchies, that incorporate initially discrepant findings.
