Book excerpt: How do we come to be who we are? Why do we differ in our personalities? How do these differences matter in life? Individual Differences and Personality aims to describe how and why personality varies among people. Unlike books that focus on individual theorists, this book focuses on current research and theory on the nature of personality and related individual differences. The book begins by discussing how personality is measured, the concept of a personality trait, and the basic dimensions of personality. This leads to a discussion of the origins of personality, with descriptions of its developmental course, its biological causes, its genetic and environmental influences, and its evolutionary function. The concept of a personality disorder is then described, followed by a discussion of the influence of personality on life outcomes in relationships, work, and health. Finally, the book examines the important differences between individuals in the realms of mental abilities, of beliefs and attitudes, and of behavior. - Presents a scientific approach to personality and related individual differences, as well as theory and research on the fundamental questions about human psychological variation - New edition presents findings from dozens of new research studies of the past six years - Includes new chapter on vocational interests and a revised chapter on personality disorders reflecting DSM-5 formulation - Contains streamlined descriptions of measurement concepts and heritability research - Includes various boxes containing interesting asides that help to maintain the student's attention