Disagree takes up a lot of brain space

The Yale researchers developed a way to scrutinize the brains of two people at the same time while discussing. What they found will not surprise anyone who is discussing politics or social issues.

When two people agree, their brains exhibit a calm synchronicity of activity focused on sensory areas of the brain. When they disagree, however, many other regions of the brain involved in higher cognitive functions are mobilized as each individual fights the other’s argument, a research team led by Yale reports Jan. 13 in the newspaper Frontiers of human neuroscience.

“Our entire brain is a social processing network,” said senior author Joy Hirsch, professor of psychiatry at Elizabeth Mears and House Jameson and professor of comparative medicine and neuroscience. “However, it takes a lot more mastery of the brain to disagree than to agree.”

For the study, researchers at Yale and University College London recruited 38 adults who were asked to say whether they agreed or disagreed with a series of statements such as “same-sex marriage is a civil right” or “marijuana must be legalized.” After matching pairs based on their responses, the researchers used an imaging technology called functional near-infrared spectroscopy to record their brain activity while they participated in face-to-face discussions.

When people agreed, brain activity was harmonious and tended to focus on sensory areas of the brain, such as the visual system, probably in response to social partners’ stimuli. However, during disputes, these areas of the brain were less active. Meanwhile, activity has increased in the frontal lobes of the brain, home to higher-order executive functions.

“There is a synchronicity between the brains when we agree,” said Hirsch. “But when we disagree, the neural coupling is disconnected.”

Understanding how our brains work while we disagree or agree is particularly important in a polarized political environment, noted Hirsch.

In disagreement, she said, two brains involve many emotional and cognitive resources “like a symphony orchestra playing different music”. Accordingly, “there is less cognitive involvement and more social interaction between the brains of speakers, similar to a musical duet”.