Robert Havighurst was an American developmental psychologist and educator known for his theory of developmental tasks. He proposed that there are certain tasks or milestones that must be achieved during each stage of human development from infancy through late adulthood. These tasks arise from biological and physical changes, personal values, and societal pressures. Havighurst identified six main stages of development - infancy & early childhood, middle childhood, adolescence, early adulthood, middle age, and later maturity - each with its own developmental tasks. His theory helped shift educational approaches to focus more on how children develop psychologically and emotionally.