Personality Traits is an essential text for students doing courses in personality and differential psychology. It also provides researchers and practitioners with a coherent, up-to-date overview of this important area. Personality research has been transformed by recent advances in our understanding of personality traits. Matthews and Deary 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 research as a collection of disconnected theories, Personality Traits presents an integrated account, linking theory-driven research with applications in clinical and occupational psychology.