Liberals may owe their political outlook partly to their genetic make-up, according to new research from the University of California, San Diego, and Harvard University. Ideology is affected not just by social factors, but also by a dopamine receptor gene called DRD4. The study's authors say this is the first research to identify a specific gene that predisposes people to certain political views.

Appearing in the latest edition of The Journal of Politics published by Cambridge University Press, the research focused on 2,000 subjects from The National Longitudinal Study of Adolescent Health. By matching genetic information with maps of the subjects' social networks, the researchers were able to show that people with a specific variant of the DRD4 gene were more likely to be liberal as adults, but only if they had an active social life in adolescence.

Dopamine is a neurotransmitter affecting brain processes that control movement, emotional response, and ability to experience pleasure and pain. Previous research has identified a connection between a variant of this gene and novelty-seeking behavior, and this behavior has previously been associated with personality traits related to political liberalism.

Lead researcher James H. Fowler of UC San Diego and his colleagues hypothesized that people with the novelty-seeking gene variant would be more interested in learning about their friends' points of view. As a consequence, people with this genetic predisposition who have a greater-than-average number of friends would be exposed to a wider variety of social norms and lifestyles, which might make them more liberal than average. They reported that "it is the crucial interaction of two factors – the genetic predisposition and the environmental condition of having many friends in adolescence – that is associated with being more liberal." The research team also showed that this held true independent of ethnicity, culture, sex or age.

Fowler concludes that the social and institutional environment cannot entirely explain a person's political attitudes and beliefs and that the role of genes must be taken into account. "These findings suggest that political affiliation is not based solely on the kind of social environment people experience," said Fowler, professor of political science and medical genetics at UC San Diego.

"It is our hope that more scholars will begin to explore the potential interaction of biology and environment," he said. "The way forward is to look for replication in different populations and age groups."