Study links brain activity and political beliefs

A USC-led study aims to explain the neurological reasons behind the growing national political divide.

Conducted by the Brain and Creativity Institute at USC and Project Reason, the study shows how different parts of the brain are activated when an individual is presented a challenge to strongly held political beliefs.

The study gathered 40 self-professed “strong liberals” who were then asked eight political and non-political questions. While political statements came from a small pool of questions, non-political statements were tailored to each person.

“We started with a series of beliefs that people had previously told us they believed really strongly, so we gave them a scale from one to seven and asked them how strongly they believed these things,” said Jonas Kaplan, lead author of the study and an assistant research professor of psychology at the Brain and Creativity Institute at USC Dornsife College of Letters, Arts and Sciences. “All of these beliefs we showed them while inside the brain scanner were beliefs they had rated six or seven, so they were rated pretty strongly. Then after we [presented] the arguments to them, we asked them again how strongly they believed this.”

According to Kaplan, a change in belief was recorded if an individual modified their response from a higher to a lower ranking on the scale after the counterargument was presented.

This occurred while the participant was in a brain scanner, allowing the study to determine which parts of the brain were activated. Researchers found that the amygdala, insular cortex and default mode network were all triggered more when contrary thinking was presented against political questions than non-political ones. The researchers found that these regions were also activated in people less likely to change their minds.

“The insular cortex is a part of the brain that processes feelings from the body,” said Sarah Gimbel, a co-author of the study and a senior research assistant at the USC Brain and Creativity Institute. “We know from other research that it’s important for emotion and emotional salience — like how emotionally important something is to you. The fact that we saw increased activation in this region … shows us when we feel threatened or anxious or emotional that we’re less likely to change our minds about these strongly held beliefs.”

While the amygdala and the default mode network act as separate mechanisms in the brain, they share similar functions. When challenged, an individual becomes emotional and threatened, which Gimbel said reveals something deeper about politics and personal identity.

“Activity when the political beliefs are challenged compared to when the non-political beliefs are challenged shows us that these areas of the brain have been linked to thinking about who we are,” Gimbel said. “It’s showing that these strongly held political beliefs have become a part of our sense of self and our sense of identity.”

The study may also have implications for similar kinds of thinking as well. Kaplan believes that the results are not confined to politics, but rather he uses politics as an example of a more general group of ideas that people resist changing their minds about.

“We used politics as a test case because we thought it would be difficult to change people’s minds about political things, and we were testing what happens when we resist changing our minds,” Kaplan said. “We don’t think this process is specific to politics. We think it’s probably more general to everything we think is important to us — so politics, religious beliefs and maybe beliefs about the USC football team if you’re a sports fan.”