'No Two Alike: Human Nature and Human Individuality,' by Judith Rich Harris - The New York Times Book Review - New York Times

'No Two Alike: Human Nature and Human Individuality,' by Judith Rich Harris - The New York Times Book Review - New York Times: "From this evolutionary logic, Harris builds a theory of personality based on three systems in our brains. The socialization system absorbs language, customs and skills, making us more alike. Mommy and Grandma wear dresses; you're a girl, so you want a dress too. The relationship system distinguishes people so we can deal with each one appropriately. Crying gets milk from Mommy but not Grandma; Billy is gentle, but Bobby hits people. Even random differences are important: Anne helped you with your homework, but her twin sister owes you a dollar. You find ways to tell people apart because you have to."

Your socialization system figures out how to conform to your group. Your relationship system figures out how to get along with each person. Your status system figures out how to compete. It monitors people's reactions, gathering information about how smart, pretty, weak or talented they think you are. It looks for virtues, activities and occupations at which you're most likely to best your peers. It notices tiny differences between the way people regard you and the way they regard others in your peer group, or even your twin. By choosing pursuits based on these differences, it magnifies them. It drives you to be different.