Red and Blue Brains. What Biology Can (and Cannot) Tell Us About Political Polarization
By: Giulia Alice Pozzi
Tags: Democrats, Republicans, USA, Political Polarization, 2020 Election

November 15, 2020

If the 2020 historic and contested election has shown anything, it is that the wound that has ripped the nation apart has not healed at all — in fact, it has painfully deepened. For many of us, it was hardly a surprise, and not just because of the harsh political climate of the last four years: newspaper headlines regularly describe increasing dislike and animosity between liberals and conservatives, while researchers unceasingly rattle off numbers in an attempt to gauge the effects of increased polarization.

The 2020 election was the umpteenth telltale sign of how difficult it will be to bridge that gap, a feat that President-elect Joe Biden will have to take on. It is no coincidence that, in a Pew Research Center survey conducted in October, eight-in-ten voters claimed that their differences with the other side were not just about politics but especially about “core American values.”

But what if this national divide actually begins at a brain level? What can liberals’ and conservatives’ brains tell us about what we have been witnessing in this election and in several other aspects of our lives?

A group of neuroscientists and psychologists from the University of California, John Hopkins University, and Stanford University have recently tried to answer that question. In a study published in October, they found evidence of what they have called “neural polarization,” which they described as “activity in the brain that diverges between people who hold liberal versus conservative political attitudes.” The researchers asked 38 participants to watch 24 videos on six different immigration policies and scanned their brains to explore the neural processing underlying their political beliefs. Prior to the experiment, participants indicated their support for each policy on a 7-point scale. To assess the existence of neural polarization, the authors used a specific measure referred to as “inter-subject correlation,” which evaluates how similarly two brains react to the same content.

The authors were surprised to see that liberals and conservatives shared similar responses in their primary auditory and visual cortices. This finding suggested that political attitudes didn’t bias their sensory attention — something that would have confirmed the idea that people tend to pay closer attention to information supporting their own beliefs.

However, something radically different happened in their dorsomedial prefrontal cortex, the area of the brain responsible for the interpretation of narratives. Put simply, their brain activity showed that “conservative and liberal participants were interpreting the content of those videos differently,” Yuan Chang Leong, a postdoctoral scholar at the University of California and the lead author of the study, said in a phone interview. “They weren’t literally seeing something different. What was happening is that neural responses diverged in a part of the brain which cares about making sense of information.” And among the other findings of their study, Leong and his colleagues discovered that specific terms, such as “risk,” “security,” “violation,” “harm,” and “compassion,” were more likely to be associated with “greater divergence in neural responses.” In other words, neural polarization increased when participants were exposed to moral-emotional and threat-related language.

What does this study tell us about political polarization? Certainly, it provides new, intriguing evidence on something we have known for a long time — as Leong put it, that “political beliefs have a powerful influence over how people perceive, interpret, and respond to information.”

For years, psychologists and social scientists have been trying to fathom the reasons why facts do not change the opinions we hold, highlighting how our minds tend to embrace information confirming our beliefs and reject what contradicts them — a phenomenon referred to as “confirmation bias.”

Take the pandemic. The numbers are unequivocal — according to John Hopkins University’s data, more than 242,000 Americans have died from the virus. Still, 76 percent of Republicans believe that the U.S. has done a good job handling the pandemic, a view shared by only 29 percent of those who do not identify with the Republican Party. Against this background, this new study pinpoints “a neural basis for partisan biases,” outlining how, on a brain level, those biases come into play when people with different political beliefs process and interpret identical information. That is why, according to Leong, “trying to persuade participants with more information might not be the most effective strategy.” “We actually have to make an effort to think about how to frame information so that they do not create greater polarization,” the neuroscientist explained.

However, it is equally important to recognize what this study, along with other works that explore the nuanced interplay between political ideologies and the functioning of the brain, might fall short of explaining about polarization. First and foremost, why is this happening? Why has the percentage of Americans who “would be somewhat or very unhappy if their child married someone of the opposite party” increased by about 35 percentage points over the last 50 years? How did things get so far? Is this really all about how our brains work?

Does It All Come Down to the Brain?

While Leong’s study does not go beyond the description of different neural responses between liberals and conservatives in processing information, other works in political neuroscience have even suggested that leftists and rightists, as well as thinking and interpreting information differently, also show a divergent brain structure. According to John Jost, a professor of Psychology and Politics and the co-director of the Center for Social and Political Behavior at New York University, two major studies are directly relevant to that particular question.

One was run in 2011 by a group of researchers at University College London and counts among its authors the Oscar-winning British actor Colin Firth, who had commissioned the experiment for his guest-editing slot on BBC Radio 4’s Today. Firth was curious to see if a deeper, more scientific explanation could be found for the growing political polarization that he was witnessing in the U.K.

The authors scanned the brains of a group of University College London students who had identified themselves as either liberals or conservatives and found a few notable differences. “People who identified themselves as more politically conservative had more gray matter volume in the amygdala,” a structure in the brain related to the processing of “potential threats in the environment, but also social hierarchies, socially significant information, and emotionally highly arousing information,” Professor Jost explained in a Zoom interview. On the other hand, people who identified as more liberal had more gray matter volume in the anterior cingulate cortex, which “is involved in the identification of potentially conflicting pieces of information” and determines “how you resolve inconsistencies and respond when things in the environment are not what you expected them to be,” he said.

Those findings were consistent with a study that Professor Jost, along with colleagues from New York University and the University of California, had run in 2007. Left-leaning and right-leaning participants were asked to perform a computer task that required them to learn a habitual response pattern. Every now and then, they were presented with an unexpected stimulus “to see how quickly they were able to switch from the dominant habitual response to a response that was more unexpected and surprising,” Jost said.

Liberals turned out to be better at the task — they were able to handle contradictory information and consequently adapt their behavior more easily and quickly than conservatives. “They made fewer mistakes, they were in that sense more cognitively flexible, whereas conservatives were more cognitively persistent and focused on the dominant response,” the NYU professor explained. And because the authors observed a spike in liberals’ brainwaves precisely localized in the anterior cingulate cortex, the same brain region where Firth’s study found more gray matter volume, they concluded that “even at the neurological level liberals were more attentive to the potential conflict.”

Beyond the Brain

To some extent, those works seem to confirm the “perfect conservative” and “perfect liberal” sketches accurately drawn by a massive body of literature in social psychology over the last 70 years. Right-leaning people have been described as more cognitively “rigid,” more close-minded and dogmatic, more intolerant of ambiguity, more likely to experience socio-economic fear, and, as a result, less prone to social change than left-leaning people. Moreover, conservatives have been widely characterized as much more focused on the preservation of the status quo and of “what had been acquired” — something that the German social psychologist and psychoanalyst Erich Fromm called, as early as 1947, “hoarding orientation.”

However, it is also apparent that those differences underpinning political ideologies can hardly be reduced to the size of a particular brain area. For instance, a 2015 study carried out by a group of researchers from Vrije Universiteit Amsterdam contradicted the “rigidity of the right” theory, maintaining that political extremes in general, and not only right-wing voters, are likely to experience socio-economic fear and derogate out-groups. If we assumed that leftists’ and rightists’ brains are biologically different, that finding would be simply inexplicable.

That’s where more nuanced approaches to political difference come into play. In the early 1970s, the British psychologist Glenn Wilson argued that both genetic and environmental factors — such as intelligence and anxiety on one hand, and parental treatment, social class, and self-esteem on the other — could influence political orientation. A number of studies built on that theory, finding, for example, that fearful children were more likely to become conservative adults. The American cognitive linguist George Lakoff has recently linked liberals’ and conservatives’ views of the nation to their divergent approaches to childrearing. According to Lakoff, while conservatives prefer “the strict father model,” based on good manners, discipline, and respect for authorities, liberals place a greater value on a “nurturant parent model,” founded on creativity and curiosity. Other works have explained polarization in terms of moral principles, with a 2012 cross-cultural study that found progressives more likely to value benevolence and universalism, as opposed to rightists’ greater attachment to conformity, security, tradition, and power.

According to Professor Jost, each of these approaches captures “part of the puzzle.” To understand the divide, “it’s useful to think in terms of personality differences, but it’s also useful to think in terms of the contents of values, attitudes, or beliefs that differ between people on the left and people on the right,” he said. As the NYU professor put it, this interweaving of factors might be explained in terms of “reciprocal causality”: “We couldn’t say that the psychology causes the polarization or the polarization causes the psychology, but maybe it’s some of both.” And because “all those things are instantiated, in some way, in our brains, there’s going to be physiological differences presumably as well.”

In other words, not only is there no scientific basis for maintaining that an inborn, neurological difference determines people’s political attitudes but adopting a single approach to interpret polarization might end up being misleading.

After all, if biology were everything, how could we explain the geographic distribution of political polarization? It is no secret that urban voters tend to adopt liberal views, while rural voters are more likely to be conservative — a trend that the 2020 election confirmed. Does this mean that people living in rural areas have more grey matter volume in their amygdala than people living in cities? Of course, it is way more complicated than that. While some studies have pointed to the clashing viewpoints ingrained in different communities — shaped by divergent socio-economic conditions and life experiences — other works, including a 2018 Pew Research Center’s survey, have highlighted the differences in the “partisan composition of urban, suburban and rural areas.” In 2019, University of North Carolina professor Rahsaan Maxwell suggested that driven by macro-economic trends, “different types of people decide to live in different geographic areas in the first place.”



Similarly, the physiological approach doesn’t tell anything about the socio-economic and generational dimensions of polarization, with highly educated adults and millennials more likely to adopt liberal positions. Neither can it explain why political attitudes are not always constant over time — even though some studies suggest that partisanship is usually acquired at a young age and rarely changes over the life cycle. Still, if different elections might have different outcomes, that means that people’s political attitudes — regardless of their brain structure — can change.

Affective Polarization and Political Dynamics: What Biology Can’t Explain

Even more important, what biology can’t really explain is the origin of affective polarization — namely the mutual dislike between liberals and conservatives — as well as the reasons for its growth. In other words, what accounts for the fact that about 64 percent of Democrats and 55 percent of Republicans claim they have “just a few” or “no” close friends who identify themselves with the opposite party — and why has this trend become more salient over time? While there are no simple answers to that question, there must be something else beyond differences in people’s brain structure.

A 2018 paper by Stanford professor Shanto Iyengar and other researchers from the University of Pennsylvania and Dartmouth College framed the issue in terms of social identity. When people identify themselves with a political party, they tend to divide up the world into an “in-group” (their own party) and an “out-group” (the opposing party), a distinction that psychologically triggers negative feelings for the latter. But some external factors may have contributed to exacerbating the divide.

One is the high-choice and fragmented media environment and the proliferation of partisan news, which “makes those with extreme attitudes even more extreme.” But also the mainstream media coverage on polarization could very well have played a part. In 2016, it was estimated that the number of stories describing how much America is divided had increased by 20 percent compared to 2000.

This almost obsessive focus on polarization may have ended up exacerbating the animosity between liberals and conservatives. “The exposure to media coverage on polarization leads people to perceive more polarization,” Yanna Krupnikov, an associate professor in the Department of Political Science at Stony Brook University, said in a phone interview. “So the more you hear about people being divided, the more you perceive that people are divided. It becomes like a circle,” she explained.

On top of that, harsh political campaigns, particularly prone to portray the competitors as “an existential threat,” may work as exacerbating factors as well. It is no surprise that, as Iyengar’s study highlighted, “across recent election cycles, people were 50–150 percent more affectively polarized by Election Day than they were a year earlier.”

Also, the fact that people are becoming more and more embedded into their own ideological online and offline communities might have played a part. Plunged into their own “bubble,” partisans are isolated from each other and more likely to encounter only “like-minded voices,” something that ends up reinforcing dislike for the other side. To be clear, there is no agreement on the fact that on social media, users are not actually “seeing” the other part. According to the sociologist Zeynep Tufekci, the real issue is that they see a caricatural and inflammatory version of it.

Whatever the case, seen through these lenses, it is no surprise that, as a 2018 study found, after the 2016 election Thanksgiving dinners where family members and guests supported opposing political parties lasted 30 to 50 minutes less than in same-party reunions. In other words, many Americans chose to cut short their Thanksgiving family parties rather than find themselves caught up in endless debates with their most politically problematic relatives. As a result, up to 34 million hours of lively Thanksgiving discussions about U.S. politics were lost in the whole country.

On the political and ideological side of the issue, Iyengar and his colleagues argue that, over the last 50 years, partisan and ideological identities have grown more and more aligned, gradually including different salient social identities, such as religion and race. Put simply, that is why White evangelicals tend to be overwhelmingly Republican, while African Americans usually identify themselves as Democrats. We could describe it as a vicious cycle where all these social identities are reinforcing themselves. As a result, people increasingly perceive members of the out-group as irreparably distant from themselves.

According to Robert Shapiro, an International and Public Affairs professor at Columbia University, polarization emerged distinctively in the 1970s after the civil rights movement, which represented the culmination of a process that made the political parties more and more distinctive on a large number of issues. Clearly, those political dynamics fall well outside the scope of the “biological” approach to political difference. “I’m not sure what the point of that is and how far that gets you,” Professor Shapiro said in this regard in a Zoom interview. “The things that are more concerning are the kinds of things that happen in real politics and that can lead to changes in people’s attitudes and behavior,” he explained. In other words, those changes would be very hard to explain if the reasons for polarization were only confined to our brains.

That is why, to analyze the current divide, Shapiro adopts a historical approach. With the civil rights movement transforming the U.S. political landscape, he argued, polarization along ideological lines began at the level of political leaders, and then slowly penetrated public opinion. But if in the past it was the public who followed the leaders, now “the leaders are constrained by the public that they have created,” he explained. In other words, “if political leaders want to moderate their views, they might have to worry about being challenged in a primary election by someone who is more extreme,” someone who “the voters in a particular district or state support.”

But what about the “Trump factor”? Shapiro believes that the current polarization would exist even without Donald Trump. “What Trump has added to this is just a heightened degree of incivility and bullying in politics,” he said. In his view, the COVID-19 crisis turned out to be an opportunity that America missed. “Some of us thought that a national crisis would pull the country together, like after World War II. We had situations like these in the past: there was the Gulf War, which in the early 1990s unified the nation briefly. There was 9/11. There was the Iraq war,” he said.

The question, now, is whether Biden, who has already presented himself as a unifier, will rise to the challenge. But according to the Columbia University professor, the hopes are slim: “The widening of the division that is occurring and the emotional level of the current division seem to be such that, at this point,” bridging that gap “might be very difficult.”

What is certain is that, if biology were everything — if it all came down to immutable differences embedded in our brain — the mission of reconciling the nation would not be just difficult: it would simply be impossible.