From The New York Times:
Why do some men and women cheat on their partners while others resist the temptation? To find the answer, a growing body of research is focusing on the science of commitment. Scientists are studying everything from the biological factors that seem to influence marital stability to a person’s psychological response after flirting with a stranger. Their findings suggest that while some people may be naturally more resistant to temptation, men and women can also train themselves to protect their relationships and raise their feelings of commitment. Recent studies have raised questions about whether genetic factors may influence commitment and marital stability. Hasse Walum, a biologist at the Karolinska Institute in Sweden, studied 552 sets of twins to learn more about a gene related to the body’s regulation of the brain chemical vasopressin, a bonding hormone.
Over all, men who carried a variation in the gene were less likely to be married, and those who had wed were more likely to have had serious marital problems and unhappy wives. Among men who carried two copies of the gene variant, about a third had experienced a serious relationship crisis in the past year, double the number seen in the men who did not carry the variant. Although the trait is often called the “fidelity gene,” Mr. Walum called that a misnomer: his research focused on marital stability, not faithfulness. “It’s difficult to use this information to predict any future behavior in men,” he told me. Now he and his colleagues are working to replicate the findings and conducting similar research in women.