"All people are born alike-except Republicans and Democrats," quipped Groucho Marx, and in fact it turns out that personality differences between liberals and conservatives are evident in early childhood. In 1969, Berkeley professors Jack and Jeanne Block embarked on a study of childhood personality, asking nursery school teachers to rate children's temperaments. They weren't even thinking about political orientation.

Twenty years later, they decided to compare the subjects' childhood personalities with their political preferences as adults. They found arresting patterns. As kids, liberals had developed close relationships with peers and were rated by their teachers as self-reliant, energetic, impulsive, and resilient. People who were conservative at age 23 had been described by their teachers as easily victimized, easily offended, indecisive, fearful, rigid, inhibited, and vulnerable at age 3. The reason for the difference, the Blocks hypothesized, was that insecure kids most needed the reassurance of tradition and authority, and they found it in conservative politics.