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He’s Definitely a Liberal—Just Check Out His Brain Scan

New research finds political ideology can be easily determined by examining how one’s brain reacts to disgusting images.
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(Photo: mdgn/Shutterstock)

(Photo: mdgn/Shutterstock)

Candidates, voters, and political scientists alike resist the idea. But we’ve had solid indications for a while now that our ideological biases are based, in large part, on the biology of our brains.

As we noted two years ago, research has found the brains of conservatives are structured in such a way that, compared to liberals, they are more prone to feelings of disgust. This leads to less-accepting attitudes on issues ranging from gay marriage to illegal immigration, which to right-wingers conjures up vague but palpable fears of contamination.

Of course, we’d like to think we came to our core beliefs through a process of rational reflection and discussion—or, at the very least, as a psychological reaction to the influence of our parents and peers. And there is certainly some evidence for the latter position.

But the profound influence of basic brain biology has just been re-affirmed in a new research paper, which found liberals and conservatives can be easily identified through fMRI scans.

While the intensity of our reaction may not reach conscious awareness, it influences the way we think about issues, and compels us to adopt certain policy positions.

“Remarkably,” writes a team led by P. Read Montague of the Virginia Tech Carilion Research Institute, “brain responses to a single disgusting stimulus were sufficient to make accurate predictions about an individual subject’s political ideology.”

Writing in the journal Current Biology, the researchers describe a study in which 83 volunteers viewed a series of images while their brains were being scanned. Chosen for their ability to evoke emotional responses, the images were, in turn, disgusting, threatening, pleasant, and neutral.

Afterwards, participants reported their response to each image, and filled out a questionnaire on their political affiliation, ideology, and positions on hot-button issues including gun control and immigration.

Liberals, conservatives, and moderates “did not significantly differ in subjective ratings of disgusting, threatening, or pleasant pictures,” the researchers report, “except that the conservative group had marginally higher disgust sensitivity than the liberal group.”

The brain scans, however, told a different story. Researchers “reliably differentiated the conservative and liberal groups” by observing how the distinctive ways their brains responded to images that evoked disgust—particularly ones that served as reminders of our animal nature, such as images of mutilated bodies.

“A single disgusting image was sufficient to predict each subject’s political orientation,” Montague told Cell Press. “I haven’t seen such clean predictive results in any other functional imaging experiments in our lab or others.”

So while the intensity of our reaction may not reach conscious awareness, it influences the way we think about issues, and compels us to adopt certain policy positions. As psychologist Jonathan Haidt noted in 2012, “When you’re disgusted by something—say, deviant sex of some sort—you tend to come up with reasons why it’s wrong.”

At least theoretically, these results could help lower the temperature of our political squabbles. If we could do away with the idea that “You’re an idiot for thinking that way” and replace it with “Your brain simply processes things differently than mine,” it would make it harder to demonize those on the other side.

But that would require giving some thought to how our ideological leanings arise, and letting go of the mindset that insists we’re right because we know we’re right.