A new study found that people who are politically conservative have a slightly larger amygdala than progressives. The results suggest that the relationship between brain anatomy and political ideology is more subtle than previously thought. The corresponding study was published in iScience.
The idea that brain structure and political ideology are linked arose from a 2011 study involving 90 English students. The study suggested that conservatives have a larger gray matter volume in the right amygdala- a region key for processing negative emotions like sadness, fear, and threat, and less gray matter in the anterior cingulate cortex (ACC), an area of the brain linked to error monitoring, belief updating, and affect-regulation.
The current study is a replication study of the former. In it, researchers analyzed MRI scans from 928 Dutch people with an average age of 22 years who represented a cross-section of the Dutch population in terms of education and political leanings. They compared participants' MRI scans with questionnaires on their political ideology.
“This is the largest preregistered replication study in the context of political neuroscience. By using Dutch as opposed to British or American data, we also extend the amygdala-conservatism link to a multiparty, multidimensional political context,” wrote the researchers in their study.
Ultimately, the researchers found that the amygdala of conservative people is slightly larger than that of progressives. In a press release, co-author of the study, Dr. Steven Scholte of the Faculty of Social and Behavioral Sciences at the University of Amsterdam, discussed the extent of the size difference. Whereas the amygdala of the average conservative voter is 157 sesame seeds in size, that of the average progressive is 156 sesame seeds. He noted that the small, but significant difference may suggest a very indirect connection between brain anatomy and ideology.
Unlike in the English sample, however, the researchers found no relationship between the ACC and political leanings.
"Our expectation was [...] to find no effect at all. [...] We do not know exactly how conservatism and the size of the amygdala are related,’ said the corresponding author of the study, Diamantis Petropoulos Petalas, from the Department of Psychology at the American College of Greece, in a press release.
‘The amygdala has mainly been studied in relation to threatening situations and fear, but seems to respond much more broadly to emotions in general and to divergent information. There may be a connection where the amygdala is larger in individuals who react more strongly to information, which could sometimes result in more conservative ideas in politics,” he added.
The researchers further found that ideology is more complex than simple identification on socio-cultural themes. For example, participants who voted for a party with radical left-wing economic positions but more conservative social values tended to have a larger amygdala than participants identifying with more progressive parties.
The researchers also found a link between the volume of the right fusiform gyrus- a part of the brain important for facial recognition- and more conservative social and economic positions. Why this is the case remains unclear.
Sources: Neuroscience News, iScience
