Cover Story

Social psychologists have long held that attitudes--whether about America's role in Iraq or the importance of one's physical appearance--are largely the product of environmental forces, a combination of upbringing and culture.

But a handful of studies show not only that attitudes are partly, though indirectly, heritable, but that attitudes with high heritability influence people's actions more strongly than those with weaker genetic bases. Indeed, highly heritable attitudes, such as political persuasions, may even steer our choices of the social "niches" we carve out for ourselves, such as where and with whom to live, according to one line of psychological research.

"When I first started this work in the 1970s, the definition of an attitude was a response conditioned 100 percent by an individual's experiences," notes University of Georgia social psychologist Abraham Tesser, PhD, who has conducted innovative studies on the social implications of highly heritable attitudes. "I think the zeitgeist has changed since the advent of the Human Genome Project--the idea that a behavioral system has a strong genetic component is hardly an issue anymore."

That said, psychologists who study attitudes agree that environmental factors--in particular, the "nonshared environment," or a person's individual experiences outside the family, usually examined via twin studies (see page 46)--are consistently stronger in predicting attitudes than genetic ones, at least among adults. In addition, it's highly doubtful there are any specific genes for any given attitudes: Instead, attitude proclivity probably funnels through other mechanisms, such as personality, that spring from genes that influence a person's neurochemistry in areas such as impulse control, they say.

And big questions remain. For instance, to what extent does "assortative mating"--people's proven tendency to choose mates with similar attitudes--bias research results, since the partial heritability of attitudes may give children those tendencies? And what explains the fact that people's attitudes often shift as they get older? Is it the result of latent genetic proclivities emerging once a person leaves home, environmental factors, or both?

In the broadest sense, the data suggest an interplay of both genetic and environmental factors in people's attitudes toward, for example, sex, politics and religion, with environment playing a stronger role, according to a major 1999 study in Twin Research (Vol. 2, No. 2) by Virginia Commonwealth University social psychologist Lindon Eaves, PhD, and colleagues.

The team examined data on 29,691 subjects--including 14,761 adult twins and their parents, spouses, siblings and adult children--and concluded that the route to transmitting attitudes within families is complex, probably reflecting a mixture of assortative mating influences and direct parental transmission. The team also found that family environment played a greater role in attitude formation than in personality variables, strengthening the notion that personality has a stronger genetic component than attitudes.

Transmission issues

Recent studies build on this knowledge base. A 2001 study of 195 identical twin pairs and 141 fraternal twin pairs by social psychologist James Olson, PhD, of the University of Western Ontario and colleagues, for instance, adds to the range of attitudes studied--in the past, largely religious and political beliefs--and directly examines possible genetic factors that may influence attitude formation.

Reported in the Journal of Personality and Social Psychology (Vol. 80, No. 6), the study found significant heritability effects for 26 of the 30 attitude items studied, including such diverse items as attitudes toward reading books, open-door immigration policies and roller-coaster rides. (However, the effects of the nonshared environment again outweighed those of heredity across the board.)

The study also examined how attitudes might be transmitted genetically, since it's highly unlikely that attitudes are directly inherited, Olson notes. To test this, the researchers included self-report questions about three sets of characteristics generally purported to have substantial genetic components: athletic ability, personality traits such as aggressiveness and sociability, and intelligence. They then examined how well the characteristics correlated at a genetic level with all 30 attitude items on their list. In several cases, individual attitudes did indeed correlate significantly with characteristics in a similar domain: Positive attitudes toward leadership and high levels of sociability were strongly related, for example, as were attitudes toward sports and levels of athleticism.

The findings indicate how attitudes might be transmitted, says Olson. Genetic and biological factors lead to differential experiences among individuals, which in turn help create differential attitudes, he explains. An athletically gifted girl, for example, has more positive experiences with sports than others--she's chosen more often for teams and garners more praise from coaches and classmates. As a consequence, she develops positive attitudes toward sports. While on the surface it might seem that the girl's positive experiences led her to enjoy sports, those experiences were partly determined by her athletic ability, which is likely genetic, says Olson.

"The idea that individuals' biological characteristics might predispose their experiences seems so obvious it's surprising it hasn't been studied more," he comments. That said, more work also is needed to separate cause and effect, he notes, since there's no proof that athletic ability precedes positive feelings about sports rather than the other way around, for example.

Sorting out mating

Another recent study lends greater precision to the respective roles of heredity and environment in attitude formation by looking at these factors in adopted and non-adopted youth and their siblings. Looking at young adoptees has two advantages: It factors out the assortative mating problem, since adopted youth don't share their parents' genes; and it provides a different perspective on gene-environment variables and interactions, since most previous studies have centered on adults, often on adult twins, notes University of Southern California psychologist Laura Baker, PhD, one of the study's co-authors.

In the study, reported in 2002 in the Journal of Personality and Social Psychology (Vol. 83, No. 6), the investigators interviewed 654 adopted and nonadopted young people about their levels of conservatism and religious attitudes every year for four years, starting when they were 12. By examining the differences between adopted and nonadopted youngsters in how similar their attitudes were to those of their parents, the team found a significant, though relatively small, genetic influence for conservatism in youngsters as early as the first year of the study, and almost no genetic link for religious attitudes. Conversely, they found large effects of the shared environment for both conservatism and religious attitudes.

The results contradict earlier findings in several ways, Baker notes: For one, other studies have suggested that genetic influences on social attitudes don't emerge until adulthood, but the study finds such a link in youth. For another, earlier studies have noted genetic influences in religious attitudes, at least among adults, while the current study found none. For a third, the study discovered a big effect for the shared environment, probably the result of studying such a young population, Baker says.

"Our findings on the shared environment may be a function of subjects' age and the fact that they're sharing more environments than adults do," Baker comments. In fact, the findings are similar to those on IQ, she says, where research shows a large shared environmental effect for children but not for adults.

The findings highlight the need for more longitudinal research that tracks age-related changes in attitudes, Baker adds, since studies have examined either young people or adults but none have captured the transition in between. Such studies may better explain why attitudes change over time, she says.

Real-life applications

While the jury's out on how genes influence attitudes over time, it appears they may account for which attitudes affect our lives the most. The University of Georgia's Tesser has conducted a number of studies showing that attitudes found in previous studies to be highly heritable are stronger, more accessible and more reinforcing than those with lower heritability.

In a 1998 study reported in Personality and Individual Differences (Vol. 24, No. 1), Tesser and colleagues even demonstrated that people react physiologically if they are primed to change highly heritable attitudes--indeed, their heart rates increase and they show higher skin conductance.

As a whole, Tesser's studies suggest that highly heritable attitudes may drive such high-stakes decisions as who to marry, how to earn a living and where to live. "You want to be around people who agree with you," Tesser says, "and even in very abstract terms, the probability of returning to places that agree with you are higher for more highly heritable attitudes."

Tori DeAngelis is a writer in Syracuse, N.Y.