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.