Your Reaction to “Gross” Pictures Can Betray Your Political Beliefs

Liberal and conservative brains show different activity patterns when they look at pictures of things typically thought of as disgusting

fly on meat
Robert Recker/Corbis

Just in time for the U.S. midterm elections, here’s evidence that the decisions we make at the polls are not the stunningly rational choices we’d like to imagine. Turns out, people more prone to disgust are more likely to be conservative. The signature of this difference between right-wing and left is visible in our brains, a research team reports in Current Biology

Brain scans on an fMRI machine revealed striking patterns when 83 volunteers were shown different images. Some of the images were neutral, some pleasant. Others were threatening, and the final group was disgusting—it included images of bodies and gore. Later, the participants rated what they thought of those images. They also took a test of their political leanings.

Conservatives’ brains reacted more strongly than liberals’ did to disgusting images, the Virginia Tech researchers found. This difference was stark, reports Amina Khan for the Los Angeles Times, even though the ratings the people gave the pictures didn’t differ much.

This connection between how disgusted you get and which way on the political spectrum you lean has been studied before. An article by Alison George in New Scientist hints at why disgust can push us to turn up our nose at those we perceive as unlike us: 

After all, other humans are all potential disease-carriers, says Valerie Curtis, director of the Hygiene Centre at the London School of Hygiene and Tropical Medicine. "We've got to be very careful about our contact with others; we've got to mitigate those disease-transfer risks," she says. Disgust is the mechanism for doing this - causing us to shun people who violate the social conventions linked to disgust, or those we think, rightly or wrongly, are carriers of disease. As such, disgust is probably an essential characteristic for thriving on a cooperative, crowded planet.

Does understanding this quirk of biology help or hinder finding solutions to political debates? It’s not clear yet, the researchers write. They note (as most studies do) that more work on this question is needed. But at the least, we’d need to admit that our political ideas are more deeply wired than we thought.

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