So is Partisanship Really in our DNA?

Feb 1 '13

The following is a guest post from New York University political scientist Christopher Dawes.


Former Vice President Al Gore recently mentioned on CNBC’s Morning Joe that “scientists now know that there is, in human nature, a divide between what we sometimes call ‘liberals’ and ‘conservatives’.”  Most of the scientists Gore was referring to are political scientists.

Inspired by earlier work done by Nick Martin, John Alford, Carolyn Funk, and John Hibbing showed in their 2005 APSR paper, that genetic variation could explain a share of individual differences in political ideology.  Several subsequent studies, employing different samples and methodologies, have corroborated these findings.  In a forthcoming paper in Behavior Genetics, Pete Hatemi and colleagues analyzed data on over 12,000 twin pairs from Australia, Hungary, Denmark, Sweden, and the United States.  The authors examined data collected at different time periods (1970-2010) as well as several different measures of ideology. Based on the combined sample, Hatemi et al. find that approximately 40% of the variation in ideology could be attributed to genetic factors (meaning the remaining 60% is explained by environmental factors).   Of course, twin studies of political ideology have been the object of criticism in the past.

Scholars have also begun to search for specific genetic variants that may be associated with political ideology.  In the same Behavior Genetics study, Hatemi et al. conduct a genome-wide association study on a sample of over 10,000 individuals from Australia and Sweden.  However, the authors did not find a significant association that could be replicated.  Benjamin et al. also failed to find a significant association for other measures of political ideology.  These two studies, along with what we know from other genetic studies of complex traits, suggest that political ideology is influenced by many genes that each have a very weak effect.  Therefore, much larger samples are likely necessary in order to achieve the power necessary to detect these small effects.

In addition to studying the link between genetics and ideology, political scientists have studied physiological and neurocognitive differences between liberals and conservatives.  In their highly publicized Science study, John Hibbing and colleagues demonstrated that conservatives exhibited a stronger response to threatening stimuli than liberals based on startle eyeblink and skin conductance response tests.  Follow-up work showed that liberals were more responsive to pleasing stimuli than conservatives.  John Jost and colleagues found a positive relationship between liberalism and activity in an area of the brain related to conflict monitoring, suggesting that ideology may be linked to how we process new information.  A group of neuroscientists also recently reported that brain structure is correlated with ideology.

Finally, political scientists have also explored links between biology and political participation, vote choice, trust, civic duty, interest, efficacy, sophistication, and partisanship.  While we are still in the early stages of understanding these relationships, it is nice to get a hat tip from the former Vice President.

Note: For an excellent review of genetics and politics, check out the Trends in Genetics piece by Pete Hatemi and Rose McDermott.