Political orientations are correlated with brain structure in young adults

Abstract

Substantial differences exist in the cognitive styles of liberals and conservatives on psychological measures. Variability in political attitudes reflects genetic influences and their interaction with environmental factors. Recent work has shown a correlation between liberalism and conflict-related activity measured by event-related potentials originating in the anterior cingulate cortex. Here we show that this functional correlate of political attitudes has a counterpart in brain structure. In a large sample of young adults, we related self-reported political attitudes to gray matter volume using structural MRI. We found that greater liberalism was associated with increased gray matter volume in the anterior cingulate cortex, whereas greater conservatism was associated with increased volume of the right amygdala. These results were replicated in an independent sample of additional participants. Our findings extend previous observations that political attitudes reflect differences in self-regulatory conflict monitoring and recognition of emotional faces by showing that such attitudes are reflected in human brain structure. Although our data do not determine whether these regions play a causal role in the formation of political attitudes, they converge with previous work to suggest a possible link between brain structure and psychological mechanisms that mediate political attitudes.

Figure 1

Individual Differences in Political Attitudes and Brain Structure (A) Regions of the anterior cingulate where gray matter volume showed a correlation with political attitudes (see Experimental Procedures for full details) are shown overlaid on a T1-weighted MRI anatomical image in the stereotactic space of the Montreal Neurologic Institute Template [29]. A statistical threshold of p < 0.05, corrected for multiple comparisons (see Experimental Procedures), is used for display purposes. The correlation (left) between political attitudes and gray matter volume (right) averaged across the region of interest (error bars represent 1 standard error of the mean, and the displayed correlation and p values refer to the statistical parametric map presented on the right) is shown. (B) The right amygdala also showed a significant negative correlation between political attitudes and gray matter volume. Display conventions and warnings about overinterpreting the correlational plot (left) are identical to those for (A).