Science Now

Liberal or conservative? Brain's 'disgust' reaction holds the answer

Is politics tied to biology? Scientists find a key difference in the brains of liberal and conservative people

Think your political beliefs arise from logic and reason? Think again. A team of scientists who studied the brains of liberal, moderate and conservative people found that they could tell who leaned left and who leaned right based on how their brains responded to disgusting pictures.

The findings, published in Current Biology, show that the brains of liberals and conservatives may indeed be wired differently — and shed light on the biological factors at play in political beliefs.

Biology and politics have long been seen by many researchers as two very separate realms. Some argue that biology is irrelevant to political questions, or that the links between the two are murky or oversimplified.

“Despite growing evidence from various fields, including genetics, cognitive neuroscience and psychology, many political scientists remain skeptical of research connecting biological factors with political ideology,” the study authors wrote.

But many of the same subjects at issue in certain political ideologies – attitudes toward sex, family, education and personal autonomy, for example – have an emotional component as much as a logic-based one. And some research has indicated that political leanings can be inherited (much in the same way that height can inherited but modified, affected by a number of factors from nutrition to the environment).

To probe this controversial question, a team led by Virginia Tech scientists called upon 83 volunteers who took a test to determine what their political leanings were. Then, while sitting in the fMRI machine, they looked at 80 different images – 20 each of disgusting, threatening, pleasant or neutral images. The researchers watched how the participants’ brains reacted to each of those images while in the machine. Later, they were asked to rate how disgusting, pleasant or threatening each image was.

When shown a disgusting image – particularly one of a mutilated animal body – the conservatives’ brains reacted more strongly, and in different ways, compared with the liberals’ brains.

“Although our results suggest that disgusting pictures evoke very different emotional processing in conservatives and liberals,” the authors wrote, “it will take a range of targeted studies in the future to tease apart the separate contribution of each brain circuit.”

The difference between the two groups was stark in spite of the fact that, oddly enough, these neural responses didn’t match the conscious ratings that participants gave those pictures.

Other images, whether threatening or pleasant or neutral, didn’t show the same link, but it’s possible that pictures of threats don’t register the same way a real threat would, the authors pointed out.

“People tend to think that their political views are purely cognitive (i.e., rational),” the study authors wrote. “However, our results further support the notion that emotional processes are tightly coupled to complex and high-dimensional human belief systems, and such emotional processes might play a much larger role than we currently believe, possibly outside our awareness of its influence.”

Certainly politics is more than a few (possibly subconscious) emotional reactions; life history and experience also affect political beliefs, the study authors wrote. But it does raise some questions about whether partisans will need to develop new strategies to reach across the political aisle.

“Would the recognition that those with different political beliefs from our own also exhibit different disgust responses from our own help us or hinder us in our ability to embrace them as coequals in democratic governance?” the researchers wrote. “Future work will be necessary to answer these important questions.”

The good news – there’s just enough time for a little political soul-searching before the Nov. 4 election.

Fascinated by the science of political science? Follow @aminawrite for more dispatches from the recesses of the human brain.

Copyright © 2016, Los Angeles Times
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