The 7R variant of DRD4, a dopamine receptor gene, had previously been associated with novelty seeking. The researchers theorized novelty seeking would be related to openness, a psychological trait that has been associated with political liberalism.
However, social environment was critical. The more friends gene carriers have in high school, the more likely they are to be liberals as adults. The authors write, "Ten friends can move a person with two copies of 7R allele almost halfway from being a conservative to moderate or from being moderate to liberal."
They theorize a larger social network may bring more diverse viewpoints, which could be an influence on the liberal development.
Neither the gene nor social networks alone influenced political identification.
Participants without the gene had no relationship between number of friends and ideology.
The sample consisted of over 2,500 individuals. Respondents were asked during their high school years to name five female and five male friends. The number of nonfamilial friends named was the measure of their social network.