Where do our personalities come from? To answer that question, we need to distinguish among three different levels of personality, according to a useful theory from psychologist Dan McAdams.21 The lowest level of our personalities, which he calls “dispositional traits,” are the sorts of broad dimensions of personality that show themselves in many different situations and are fairly consistent from childhood through old age. These are traits such as threat sensitivity, novelty seeking, extraversion, and conscientiousness. These traits are not mental modules that some people have and others lack; they’re more like adjustments to dials on brain systems that everyone has.
Let’s imagine a pair of fraternal twins, a brother and sister raised together in the same home. During their nine months together in their mother’s womb, the brother’s genes were busy constructing a brain that was a bit higher than average in its sensitivity to threats, a bit lower than average in its tendency to feel pleasure when exposed to radically new experiences. The sister’s genes were busy making a brain with the opposite settings.
The two siblings grow up in the same house and attend the same schools, but they gradually create different worlds for themselves. Even in nursery school, their behavior causes adults to treat them differently. One study found that women who called themselves liberals as adults had been rated by their nursery school teachers as having traits consistent with threat insensitivity and novelty-seeking.22 Future liberals were described as being more curious, verbal, and self-reliant, but also more assertive and aggressive, less obedient and neat [That's me exactly when I was a child]. So if we could observe our fraternal twins in their first years of schooling, we’d find teachers responding differently to them. Some teachers might be drawn to the creative but rebellious little girl; others would crack down on her as an unruly brat, while praising her brother as a model student.
But dispositional traits are just the lowest of the three levels, according to McAdams. The second level is our “characteristic adaptations.” These are traits that emerge as we grow. They are called adaptations because people develop them in response to the specific environments and challenges that they happen to face. For example, let’s follow our twins into adolescence, and let’s suppose they attend a fairly strict and well-ordered school. The brother fits in well, but the sister engages in constant battles with the teachers. She becomes angry and socially disengaged. These are now parts of her personality—her characteristic adaptations—but they would not have developed had she gone to a more progressive and less structured school.
By the time they reach high school and begin to take an interest in politics, the two siblings have chosen different activities (the sister joins the debate team in part for the opportunity to travel; the brother gets more involved with his family’s church) and amassed different friends (the sister joins the goths; the brother joins the jocks). The sister chooses to go to college in New York City, where she majors in Latin American studies and finds her calling as an advocate for the children of illegal immigrants. Because her social circle is entirely composed of liberals, she is enmeshed in a moral matrix based primarily on the Care/harm foundation. In 2008, she is electrified by Barack Obama’s concern for the poor and his promise of change.
The brother, in contrast, has no interest in moving far away to a big, dirty, and threatening city. He chooses to stay close to family and friends by attending the local branch of the state university. He earns a degree in business and then works for a local bank, gradually rising to a high position. He becomes a pillar of his church and his community, the sort of person that Putnam and Campbell praised for generating large amounts of social capital.23 The moral matrices that surround him are based on all six foundations. There is occasional talk in church sermons of helping victims of oppression, but the most common moral themes in his life are personal responsibility (based on the Fairness foundation—not being a free rider or a burden on others) and loyalty to the many groups and teams to which he belongs. He resonates to John McCain’s campaign slogan, “Country First.”
Things didn’t have to work out this way. On the day they were born, the sister was not predestined to vote for Obama; the brother was not guaranteed to become a Republican. But their different sets of genes gave them different first drafts of their minds, which led them down different paths, through different life experiences, and into different moral subcultures. By the time they reach adulthood they have become very different people whose one point of political agreement is that they must not talk about politics when the sister comes home for the holidays.