The brains of conservative people tend to look like the brains of other conservative people — and the same goes for liberals — although it’s not exactly clear why.

“Can we understand political behavior by looking solely at the brain? The answer is a fairly resounding ‘yes,’” said study co-author Skyler Cranmer, a professor of Political Science at The Ohio State University (OSU).

Cranmer and colleagues from OSU, University of Pittsburgh School of Medicine, and New York University wanted to see whether political ideology has any neurological underpinnings. They recruited 174 participants and carried out fMRI scans while the participants were carrying out various tasks.

“None of the eight tasks was designed to elicit partisan responses,” said first author Seo Eun Yang, now an assistant professor of political science at Northeastern University, who did the work as a doctoral student at Ohio State.“But we found the scans from all eight tasks were related to whether they identified as liberals or conservatives.”

The team used an AI algorithm running on the Ohio Supercomputer Center to analyze the scans and place participants on a six-point scale from “very liberal” to “very conservative”. The fMRI signatures of the brain were as accurate as the best predictor used in political science research to predict political ideology (the ideology of people’s parents).

When the brain scans were coupled with demographic and other indicators (such as age, gender, and education), the model was better than any other single indicator at predicting ideology. In fact, even when people weren’t doing anything and were just sitting idly, the brain signatures showed a relationship to political ideology.

In particular, activations of specific regions of the brain (the amygdala, inferior frontal gyrus and the hippocampus) were most strongly associated with political affiliation.

“Even without any stimulus at all, functional connectivity in the brain can help us predict a person’s political orientation,” said James Wilson, assistant professor of psychiatry and biostatistics at the University of Pittsburgh School of Medicine and one of the study authors.

“Collectively, our analyses suggest that functional connectivity reveals noticeable and discriminative features among liberals and conservatives, and that these patterns can be identified with high accuracy,” the researchers write in the study.

Few studies have linked brain connectivity to political ideology, and the fact that the two seem to be so tightly connected suggests that political leanings have deeper roots than you may think.

However, the cause-effect direction of it is unclear. Researchers aren’t sure if it’s people’s brain wiring that’s directing political beliefs or if it’s the political beliefs that shape the brain in a specific way.

More research is needed to shed light on this, but drawing cause-effect lines is never easy in neuroscience.

The study was published in PNAS Nexus.