ABSTRACT
It is often remarked that the study of adult age changes has but a short history and that one should therefore expect emphasis to be placed upon descriptive studies as a means of building the necessary foundation of empirical data. At least twenty years have passed, however, since the first important cross-sectional studies of the adult life span reached publication, but research emphasis has changed very little. It is timely, therefore, to look for theoretical models which will help integrate the wealth of research data now available.
