Adult cognitive development is one of the most important, yet neglected aspects in the study of human psychology. Although the development of cognition and intelligence during childhood and adolescence is of great interest to researchers, educators, and parents, they assume that thisdevelopment stops progressing in any significant manner when people reach adulthood. In fact, cognition and intelligence do continue to progress in very significant ways. In Developmental Influences on Adult Intelligence, Warner Schaie lays out the reasons why we should continue to study cognitivedevelopment in adulthood, and presents the history, latest data, and results from the Seattle Longitudinal Study (SLS), which now extends to over 45 years. The SLS is organized around five questions: Does intelligence change uniformly throughout adulthood, or are there different life-course-abilitypatterns?