Candidate genes

Scholars therefore recently turned their attention to specific genes that might be associated with political behaviors and attitudes. In the first-ever research to link specific genes to political phenotypes, a direct association was established between voter turnout and monoamine oxidase A (MAO-A) and a gene–environment interaction between turnout and the serotonin transporter (5HTT) gene among those who frequently participated in religious activities.^[15] In other research scholars have also found an association between voter turnout and a dopamine receptor (DRD2) gene that is mediated by a significant association between that gene and the tendency to affiliate with a political party.^{[16][clarification needed]} More recent studies show an interaction between friendships and the dopamine receptor (DRD4) gene that is associated with political ideology.^[17] Although this work is preliminary and needs replication, it suggests that neurotransmitter function has an important effect on political behavior.

The candidate genes approach to genopolitics received substantial criticism in a 2012 article, published in the American Political Science Review, which argued that many of the candidate genes identified in the above research are associated with innumerable traits and behaviors. The degree to which these genes are associated with so many outcomes thus undermines the apparent important of evidence linking a gene to any particular outcome.^[18]

Linkage analysis

Employing a more general approach, researchers used genome-wide linkage analysis to identify chromosomal regions associated with political attitudes assessed using scores on a liberalism-conservativism scale.^[19] Their analysis identified several significant linkage peaks and the associated chromosomal regions implicate a possible role for NMDA and glutamate related receptors in forming political attitudes. However, this role is speculative as linkage analysis cannot identify the effect of individual genes.

Other explanations

Associations between genetic markers and political behavior are often assumed to predict a causal connection between the two. Scholars have little incentive to be skeptical of this presumed causal link. Yet it is possible that a confounding factor exists which makes the genetic relationship with politics purely correlative. For instance work on Irish parties, which shows some evidence of a genetic basis for the otherwise inexplicable distinction between the historically two main parties there, is also and more easily explained by socialization.^[20]