Now in a revised and expanded fourth edition, this definitive reference and text has more than 50% new material, reflecting a decade of theoretical and empirical advances. Prominent researchers describe major theories and review cutting-edge findings. The volume explores how personality emerges from and interacts with biological, developmental, cognitive, affective, and social processes, and the implications for well-being and health. Innovative research programs and methods are presented throughout. The concluding section showcases emerging issues and new directions in the field. New to This Edition: Expanded coverage of personality development, with chapters on the overall life course, middle childhood, adolescence, and early adulthood, Three new chapters on affective processes, plus chapters on neurobiology, achievement motivation, cognitive approaches, narcissism, and other new topics, and Section on cutting-edge issues: personality interventions, personality manifestations in everyday life, geographical variation in personality, self-knowledge, and the links between personality and economics.