Personality can be defined along a small number of well established dimensions, each of which is partially determined by hereditary factors. Heredity acts on behavior through its influence on variations in the structure and function of neural and biochemical systems. This book explores the biological basis of individual differences in personality from genes to the structure, chemistry, and function of the brain and peripheral nervous system. In addition to basic dimensions of normal personality, the book examines the biology of several types of psychopathology. The concluding chapter provides a psychobiological model for personality. This thorough analysis of the pathway from gene to personality trait will be of interest not only to biologists, but also to psychologists and psychiatrists.