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"There are certain qualities parents would like to see in all their children—kindness, conscientiousness, intelligence—and other qualities they are willing to let vary within reasonable limits. But the findings for the universally desired qualities are the same as for the optional ones: no evidence of a long-term effect of the home environment.
One thing that could have worked in favor of the nurture assumption, but didn’t, is birth order. Parents treat firstborns and laterborns differently, and the differential treatment isn’t just a response to characteristics the kids were born with. But researchers have been trying for more than half a century to find convincing proof that birth order leaves lasting marks on personality, and their efforts have not panned out. Nor have efforts to show differences in personality between only children and children with siblings. If parents have major effects on their children, how come they don’t mess up the personality of the only child? These two disappointments—no birth order effects, no only child effects—should knock the last remaining prop from under the nurture assumption.
If the peer group’s culture differs from the parents’, the peer group’s always wins. The child of immigrant parents or deaf parents invariably learns the language of her peers and favors it over the language her parents taught her. It becomes her native language. You can see it happening as early as nursery school, when three-year-olds start bringing home the accents of their peers. Perhaps it begins even earlier than that.
Experiences in childhood and adolescent peer groups modify children’s personalities in ways they will carry with them to adulthood. Group socialization socialization theory makes this prediction: that children would develop into the same sort of adults if we left their lives outside the home unchanged—left them in their schools and their neighborhoods—but switched all the parents around.
Personality generally does not change much in adulthood.
My theory predicts that low status in the group, especially if it persists for years, will leave permanent marks on a child’s personality.
What about birth order effects on intelligence? Claims of a firstborn advantage in IQ are periodically made and receive a lot of publicity, but I remain unconvinced. If firstborns really were smarter, we would expect them to make better grades than their younger siblings, and they do not. Nor are they more likely to go to college.
Most criminologists and developmentalists believe that the right sort of parenting can keep a kid from joining the wrong sort of peer group.
This time the researchers used behavioral genetic methods (the subjects were twins) to assess the genetic contribution to adolescents’ membership in antisocial peer groups. They found a sizable genetic contribution to membership in such groups, and no influence of parenting practices. Neither parental behaviors shared by both twins, nor parental behaviors applied differentially, could account for the twins’ peer group affiliations or antisocial behavior. How do genes influence the kind of peer group a teenager will join? Indirectly, by their influence on the teenager’s personality, intelligence, and talents. Kids whose genes predispose them to be intelligent and conscientious are more likely to become members of academically oriented peer groups. Those whose genes predispose them to be risk-takers or sensation-seekers are more likely to end up in the kind of group that their parents don’t want them to join. As I said in Chapter 12, “As birds of a feather flock together, aggressive teens and those who are attracted to excitement and danger find others like themselves. Such personality characteristics are partly genetic, so when kids seek out other kids who are similar to themselves, to some extent they are seeking out those with similar genes.”
As you’ve no doubt noticed, my favorite method for eliminating the effects of genes is by looking at language and accent. Children are not genetically predisposed to acquire one language or accent rather than another: it is entirely a function of their social environment—specifically, the environment they share with peers. The evidence I presented in Chapter 9 comes from observations of the offspring of immigrants, the hearing offspring of deaf parents, and the deaf offspring of hearing parents. In all cases, the offsprings’ primary language in adulthood is the language they used to communicate with their peers in childhood and adolescence. But don’t misunderstand me. Sometimes the offspring of immigrants do speak with a “foreign” accent in adulthood. There are several reasons why this might happen. Rarely, it might be due to some sort of social impairment. Children with autism retain their parents’ accent, evidently because they do not identify with peers. Far more commonly, it simply means that the speaker grew up in a neighborhood, or attended a school, where there were many immigrants from the same part of the world. In such places, children often remain bilingual—they share both their languages with their peers. They retain the accent because their peers speak that way, too. The other common reason for retaining an accent is age. People who were in their teens when they immigrated will probably never entirely lose the accent of the country they came from. But the cutoff age varies and no one seems to know why."