Personality is now understood to be a function of both biological and environmental influences. This revised and updated edition of Psychobiology of Personality describes what is currently known about the biological basis of the primary personality traits, including genetic, neurological, biochemical, physiological, and behavioral influences. Emphasis is placed on understanding the connections between phenomena at these levels. The research discussed makes use of animal models, based on experimental brain research, as well as human clinical and normal personality research. Chapters are devoted to temperament and personality trait structure, psychobiological methods, and each of four major personality traits: extraversion, impulsive, sensation seeking, and aggression. Recent advances in psychobiological methods, such as molecular genetics and brain imaging have enabled us to begin to unravel the genetic and neurological sources of behavior and personality. These advances are discussed in this new edition, making it essential reading for advanced students of psychology and psychiatry.