What Political Polarization Looks Like In Your Brain


In a presidential election year in the United States, it’s pretty much impossible to not find yourself bombarded with political campaign commercials on TV or radio — and your share of campaign phone calls or literature by mail — especially if you live in a swing state. Whatever your own political leanings may be, you’re probably feeling anywhere between fatigued from all of it, to reassured and encouraged when you see a Facebook post promoting your candidate of choice, to enraged when you see an article promoting the other side. We live in a time when the divide of partisan politics only seems to be getting worse, is there a way to bridge the relations gap and the information we consume? A new research effort from scientists at UC Berkeley, Stanford University, and Johns Hopkins University sought to understand why our own political views cause us to process information differently, and what role our own beliefs played in it.

To do so, they scanned the brains of over three dozen test subjects, adults who identified as politically left or right of the spectrum and had them view short video clips that dealt with current political issues around immigration. Topics in the videos included the construction of a wall among the U.S.-Mexico southern border, as well as Congress making laws to protect undocumented immigrants who came to the country under the federal Deferred Action for Childhood Arrivals (DACA) program, known as “Dreamers.”

The paper was published by the Proceedings of the National Academy of Sciences and demonstrated that liberals and conservatives have a different neural response to watching the exact same images, and this became more prominent whenever the content included key vocabulary words that one frequently sees or hears in political campaign messages.

“Our study suggests that there is a neural basis to partisan biases, and some language especially drives polarization,” said the study’s lead author Dr. Yuan Chang Leong, a postdoctoral candidate in cognitive neuroscience at UC Berkeley. Leong recognized a pattern — that both right and left-leaning brains increased activity when they picked up messages that suggest threats, morality or emotions.

These results come at a crucial and interesting time — when many voters and pundits consider 2020 as the most consequential presidential election in recent American history — and reveal a look into a partisan brain that neuroscientists have never seen before. It makes you wonder that a deeper understanding of the inner workings might mean a look into a different political landscape entirely. Leong and his team emphasize that the partisan lean of an individual’s brain can be attributed to a number of factors — the way in which the news media reports on news, as well as the sources the individual relies on for news, but also on their own personal experience. These all define what the researchers call “neural polarization.”

“Even when presented with the same exact content, people can respond very differently, which can contribute to continued division,” said the study’s senior author Dr. Jamil Zaki, who is a professor of psychology at Stanford University. What’s surprising is that we tend to think of political differences sometimes arising from a tendency to disagree with one another due to circumstances beyond politics that we can’t always control, but the media we consume and our own experience are more likely culprits.

What Makes Us Tick?

Biologically, the study narrows the source of neural polarization to one of the higher-order regions of the brain known as the dorsomedial prefrontal cortex. This is the portion of the brain that acts as the brain’s polygraph — following a narrative thread and deconstructing it piece by piece so it makes sense.

The researchers found that the closer the brain activity was to an “average liberal” or “average conservative” in an individual, the more likely they were to adopt political positions associated with that group after watching the video.

“This finding suggests that the more participants adopt the conservative interpretation of a video, the more likely they are to be persuaded to take the conservative position, and vice versa,” said Leong.

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