At a time when an overwhelming number of Americans – about eight out of 10 – acknowledge that members of the two major political parties struggle to agree on the most basic facts (let alone policy), new research suggests otherwise. It shows that these political opponents have a lot in common.
The Brown University researchers discovered that the most committed partisans – from both ends of the spectrum – share some common ground. The authors claim that the brains of extreme left and right-wing voters process political content in surprisingly similar ways.
“Our study showed that the brains of highly conservative and highly liberal individuals are processing the same charged political content in ways that are even more similar than people in their own political parties with more moderate beliefs,” co-author Oriel FeldmanHall, PhD, a Brown professor of cognitive and psychological sciences explained.
The Roots of Polarization
Academics have long since discovered that emotions drive political division. Negative feelings – such as anger and fear – don’t just drive these groups apart. These primal emotions also fuel the risk of extremism and, in the worst cases, violence.
Even so, very little research has looked into the neural machinery behind these reactions.
The authors of this newest study wanted to answer at least two questions:
- Do extreme political views correspond with stronger emotional processing in the brain?
- And do extremists’ brains synchronize with one another while they’re watching the same content?
Methodology
Appearing in the latest Journal of Personality and Social Psychology, the paper details the researchers’ efforts to dig into what happens when ideological extremes watch the same heated political debates. To do so, the team relied on brain imaging, physiological monitoring, and computational language analysis to track participants’ reactions.
What they found is that extremism itself (much more than party affiliation) appears to tune people’s minds to react in lockstep.
The researchers recruited 43 adults from both ends of the political spectrum for the project. Participants first identified their ideology on a scale from “extremely liberal” to “extremely conservative.” Then, while inside an MRI scanner, they watched nearly 18 minutes of the 2016 vice-presidential debate between Democrat Tim Kaine and Republican Mike Pence, focusing on the hot-button issues of immigration and policing.
To capture a more comprehensive picture, the team tracked brain activity in regions tied to emotional processing (the amygdala and periaqueductal gray) and social interpretation (the posterior superior temporal sulcus, or pSTS).
They also monitored physiological arousal through skin conductance, gauged eye movements to rule out simple attention effects, and later analyzed the debate transcript with a large language model to quantify the levels of “extremist” language.
What the Brains Revealed
The results appeared to be quite clear. Participants with stronger ideological leanings – of either party – showed heightened activation in emotion-related brain regions during the debate. The amygdala, periaqueductal gray, and pSTS lit up more intensely in those who sat at the edges of the political scale than in moderates.
But the most intriguing finding came when the researchers compared brain activity across individuals. People who both held extreme views—again, regardless of whether liberal or conservative—exhibited synchronized patterns in the pSTS and temporoparietal junction. In other words, their brains processed the debate in remarkably similar rhythms, even when they fundamentally disagreed on its substance.
That synchrony grew stronger during moments when the candidates used more extreme language. It also intensified when pairs of participants displayed similar spikes in physiological arousal, such as sweaty palms captured by skin conductance sensors. Together, these findings suggest that emotion acts as a binding force for extremists, aligning their neural responses in ways that transcend simple ideology.
The results lend support to the so-called “horseshoe theory,” the idea that extremists on opposite ends of the spectrum resemble one another more than they resemble moderates in the middle. Neural synchrony provides a biological signature of that phenomenon.
Making Sense Of It
Understanding these mechanisms could help explain why it’s become so challenging to bridge growing partisan divides. If extremists are neurally wired to experience political battles through heightened, synchronized emotion, then facts and arguments won’t make much of a difference. Emotional regulation – not persuasion based on logic – could be a more effective lever.
The findings also help explain why inflammatory language resonates. When political leaders escalate the rhetoric, they could amplify neural synchrony among their most committed followers, reinforcing a shared sense of extremity.
“When someone is so entrenched in their own extreme beliefs, it can be hard to think about how others might see the world,” FeldmanHall said. “I think it might be shocking to know that the way that their brain is processing information is very similar to someone who is on the other side of the spectrum, and who holds ideological beliefs that are diametrically opposed to theirs. And in that sense, it might be a useful way of making a vast political divide a little smaller.”
As the United States creeps toward another (almost certainly) contentious midterm election, this new research serves as a sobering reminder. Partisans might look like polar opposites, but underneath? Their brains usually march to the same beat.
Further Reading
The Psychology of Political Polarization
Politics Emerge in Everyday Grocery Decisions
Post-2020 Election Partisan Hostility Left Americans Traumatized
