There has long been evidence that political “thinking” is not rational, that in fact it does not involve the reasoning parts of the brain at all, but instead occurs in the emotion-processing center of the brain. In a study using functional neuroimaging (fMRI) on a sample of committed Democrats and Republicans during the three months prior to the U.S. Presidential election of 2004, participants were given a reasoning task in which they had to evaluate negative information about their candidate. “We did not see any increased activation in the parts of the brain normally engaged during reasoning,” said Drew Westen, director of clinical psychology at Emory who led the study. “What we saw instead was a network of emotion circuits lighting up, including circuits involved in regulating emotion and resolving conflicts.”

David S. D’Amato, a lawyer who has written for a number of publications about public policy and other issues, has just published (in a publication promoting libertarian policies) a very interesting article gathering some of the studies that have followed up on that early one.

He points out that it is partisan identity rather than concrete policy preferences that often divides people. Most Americans are not at all ideological, have little information on the history of ideas or the empirical evidence that bears on particular policy questions and are often not able to articulate correctly their own or the other side’s specific policy positions.

D’Amato’s conclusion on partisanship is that group identification is programmed more deeply into our brains than is abstract thinking. “In other words, people will go along with the group, even if the ideas oppose their own ideologies—belonging may have more value than facts,” as one science writer put it.

Evidently these biased processes in our brains that have been put in place over years of evolution and that are instrumental in forming our conclusions about important issues are underneath or beyond our awareness. “To reflect on this for even a moment should fill anyone who aspires to critical thinking or rationality with a kind of dread, for loyalty to the team seems to be overriding the higher faculties of the mind,”  D’Amato says. And the neural pathways that lead us to the same recurring partisan viewpoint seem to be carved largely by repeatedly consuming the same media.

So we predictably fall in line with our entrenched partisan viewpoint regardless of the facts, but further evidence suggests that, because of that partisan influence, we don’t even understand how we’ve come to those opinions.

In one study, the results revealed a conspicuous “introspective blindness to the internal processes leading to a moral or political judgment.” People didn’t seem to understand why they made the decisions they made (or didn’t make), though some exhibited what the researchers call “unconscious detection of self‐​deception”—these subjects were unable to consciously detect that their answers had been influenced, but they did register lower confidence in what were “manipulated choices,” which the authors suggest points to “the existence of a neural mechanism unconsciously monitoring our own thoughts.” Interestingly, results of the study showed that females were more difficult to manipulate in a partisan way than men.

The Dunning‐​Kruger effect (where people think they know a lot more than they actually do) is apparently exaggerated within the context of politics, with low‐​knowledge participants describing themselves as even more knowledgeable than usual once partisanship is a conspicuous factor. Vitor Geraldi Haase and Isabella Starling‐​Alves posit that this kind of self‐​deception,  “a major characteristic of political partisanship,” “probably evolved as an evolutionary adaptive strategy to deal with group dynamics.” Objective truth, meaning roughly an accurate model of reality, is not important, at least not anywhere near as important as conformity with and submission to what is viewed as social reality. So partisanship isn’t as much about politics in the philosophical sense as “party loyalty” that prevails over policy and, again, even over truth.

Partisanship may also quite literally make us dumb. D’Amato calls that entrenched partisanship a kind of mind poisoning, an infection that leads to serious and, importantly, measurable cognitive impairment. In a 2018 study of why and how partisanship impairs the brain’s ability to process information objectively, NYU researchers Jay J. Van Bavel and Andrea Pereira note that “partisanship can alter memory, implicit evaluation, and even perceptual judgments.” Cambridge psychologist Leor Zmigrod writes, “Regardless of the direction and content of their political beliefs, extreme partisans have a similar cognitive profile.” Specifically, partisans show lower levels of cognitive flexibility; even when processing information that has no political character, they are more dogmatic, less adaptable, and less able “to adapt to novel or changing environments and switch between modes of thinking.” If a question mentions a politician or political party, subjects are often unable to accurately assess basic facts. A question with a mild political slant renders many subjects unable to answer a simple question despite having been given the correct answer. Strong political affiliations even affect the ability to perform basic math: if a statistic contradicts a partisan view, the subject will tend to question the calculation rather than update their position.

The only other explanation to explain this recurring profile is that dumb people are just more likely to be committed partisans, Zmigrod suggests, although she is careful to point out that her study doesn’t address that question.

In a groundbreaking study published last summer, a team of researchers led by the University of Exeter’s Darren Schreiber found that nonpartisans’ brains are different from those of their brainwashed brethren, particularly in “regions that are typically involved in social cognition.” According to those researchers, around 40% of Americans do not affiliate with a political party even though many political scientists assume they are merely covert partisans. However, the study found that most of these people are truly nonpartisans and that they are particularly turned off by the heated, often non-rational rhetoric that dominates so much of politics today, leading them to disengage. The researchers are hoping that neuroscience can help bring both partisans and nonpartisans people together by opening up their minds and emotions to rational solutions that can bind the group together. As social policy expert Elizabeth A. Segal writes, “Ultimately our goal should be to build a tribe that we all belong to: that of humanity.”

Ideally, the authors of an NYU study say, we should try to “de-bias” our information processing in order to create a shared reality “across partisan divides.” That involves consuming diverse sources of news, listening to other viewpoints and learning to tolerate the discomfort of emotional reactions to “facts” that we would rather not know about, or would prefer to explain away.