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. *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. *Added breadth and accessibility–42 more concise chapters, compared to 32 in the prior edition.