Adds essential clarification to the ongoing debate between nature and nurture in the development of intelligence. Contains a broad overview of the way motivation and cultural conditions shape the growth and use of cognitive skills. Many familiar concepts from the classical psychology of personality--need for achievement, level of aspiration, field dependence, the authoritarian personality--are reviewed along with others more recently defined--fear of success, learned helplessness, mastery orientation. Surveys the cognitive roots of mental ability including language and its relation to thought, memory and metamemory, methods of problem solving and heuristics for creativity. Offers new information that has serious potential as an influence in social and educational policy, race relations and more.