Personality research has been transformed by recent advances in our understanding of personality traits. This book offers a comprehensive and accessible survey of research on traits. It discusses how they are defined and measured, and shows that they are central to personality. The authors review the origins of traits in biological and social processes, and their consequences for cognition, performance and mental and physical health. Contrary to the traditional view of personality reasearch as a collection of disconnected theories, this study presents an integrated account that links theory-driven research with applications in clinical and occupational psychology. Personality Traits is an essential, up-to-date resource for researchers of personality and differential psychology.