What Political Polarization Looks Like In Your Brain


When Leong and his fellow researchers began their study, they had several competing theories on how an individual’s ideological leanings would impact how they took in and assessed political information. Their initial hypothesis proposed that if sensory information processed by the brain — just simple sounds and images played a force in neural polarization, the brain scans would indicate new levels of brain activity taking place in both the visual and auditory cortices.

However, if the narrative of the video told the story and determined what sensory information people took in from watching the videos, the researchers supposed they would find this disparity occurring in higher-order brain regions, like the prefrontal cortex, and this is the theory that won out.

Your Brain On Politics

To determine how sentiments toward immigration policy could betray either a conservative or liberal bias in an individual, the researchers initially conducted a survey on 300 people who described themselves as either liberal, moderate, or conservative, with varying degrees.

The team then recruited 38 young and middle-aged men and women, all of whom shared similar economic statuses and education levels. who had rated their opposition or support for controversial immigration policies. Using functional MRI technology, they scanned their brains as they watched the videos, which were a pastiche of news clips, campaign ads, and excerpts from campaign speeches by recognizable politicians.

After the subjects watched a video, they were asked to rate on a scale of one to five based on whether or not they agreed with what the video was trying to say, how much they believed the content being presented was trustworthy, and also the degree to which the video challenged their own stance on immigration and changed their minds.

To tabulate the brain responses from each group, the researchers used a method called “inter-subject correlation,” used as a contrast to measure objectively the difference in how two brains react to the same phenomenon.

Their results indicated a high level of shared response throughout the group, taking place in both the auditory and visual cortices. This shared response was visible with no regard for the participants’ political views. However, the neural responses was where the researchers found an observable difference — as it happened along partisan lines in the brain’s dorsomedial prefrontal cortex, the same region of the brain we use to process word meanings.

By this time, it was clear that there were key phrases that played a role in neural polarization. It was just a matter of determining which ones do it. So the researchers then edited their videos down further — into 87 brief segments. They took recurring phrases from each segment that were then split into 50 categories: statements pertaining to things like morality, emotions, or threat, and religion.

Words in the video pertaining to risks and threats — or morality and emotion, led to higher levels of polarization in the subjects’ neural response.

Too Great A Risk?

One risk-related statement from the clips was: “I think it’s very dangerous, because what we want is cooperation among the cities and the federal government to ensure that we have safety in our communities, and to ensure that our citizens are protected.”

A moral-emotional statement key phrase Leong listed was: “What are the fundamental ethical principles that are the basis of our society? Do no harm, and be compassionate, and this federal policy violates both of these principles.”

The paper’s conclusion suggests that political messages using either risk/threat-related or moral-emotional language can bring out the partisans in us — so we begin to interpret the same message in the opposite manner, and in doing so, do more to increase a climate of polarization.

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