Political Beliefs: Nature or Nurture?

There’s a growing body of evidence that there may be a genetic component to your political leanings.

Mother Jones highlights a new study published in the journal Political Psychology that looks at the political leanings of identical twins vs. those of fraternal twins. The identical twins share 100% of their genetic makeup, while the fraternal pairs have only 50% in common. What they found is political belief tended to be more common among the identical twins.

Using this “twin study” paradigm—which is widely employed to determine the heritability of a variety of traits, such as eye color and height—researchers can estimate what percentage of a given characteristic is rooted in genetic influences rather than environmental influences. The twin study approach then attributes the remaining variability to either factors in the environment that lead twins to be similar (“shared environment”), or those that cause them to be different (“unique environment”). “Maybe you saw a robbery, and your twin didn’t,” Hibbing explains. For politics, the studies tend to suggest that genes and “unique environment” experiences provide the bulk of the explanation, with “shared environment” seeming to matter relatively little. (Given that “shared environment” is usually taken to include influences on both twins in the home as they grow up, this may be the most surprising finding of all.)

And it isn’t just our political beliefs: It’s a range of complex social traits. Personalities have also been repeatedly shown to have a substantial genetic basis, and so has religiosity. None of this research, to be sure, says that genes determine everything. The “environment” still matters a great deal. Nonetheless, the percentage of total variation in our views attributed to genes is quite substantial. According to Hibbing, the body of published evidence is homing in on a number around 30 to 40 percent for our political views.

The truly interesting question then becomes: Precisely which genes are determining our political views, and how are they operating? That’s where it gets tricky: Scientists don’t really know. Arguably the best study seeking to identify a single political gene examined DRD4, a gene coding for a receptor for the neurotransmitter dopamine in the brain. One variant of DRD4 has been associated with novelty-seeking and exploratory behavior, and sure enough, the study found that it was also associated with liberalism—but only, the paper noted, among those who had a lot of friends growing up. In other words, the scientists didn’t actually find a “political gene”; what they found was a gene that has political implications in a particular life context.