A new study has shown that people's brains are more responsive to friends than to strangers, even if the stranger has more in common.
Researchers examined a brain region known to be involved in processing social information, and the results suggest that social alliances outweigh shared interests.
In a study led by graduate student Fenna Krienen and senior author Randy Buckner, PhD, of Harvard University, researchers investigated how the medial prefrontal cortex and associated brain regions signal someone's value in a social situation. Previous work has shown that perceptions of others' beliefs guide social interactions. Krienen and her colleagues wondered whether these brain regions respond more to those we know, or to those with whom we share similar interests.
The researchers first imaged the brain activity of 32 participants as they judged how well lists of adjectives described their personalities. This helped to identify brain regions that respond to personally relevant information. In separate experiments, 66 different participants provided personality information about themselves and two friends - one friend whom they believed had similar preferences and one believed to be dissimilar.
The authors made up biographies of similar and dissimilar strangers for each volunteer based on their personality profiles. Then, while in a scanner, they played a game similar to the TV show "The Newlywed Game," in which participants predicted how another person would answer a question. For example, would a friend or stranger prefer an aisle or window seat on a flight?
The authors found activity in the medial prefrontal cortex increased when people answered questions about friends. Notably, whether the person had common interests made no difference in brain response.
"In all experiments, closeness but not similarity appeared to drive responses in medial prefrontal regions and associated regions throughout the brain," Krienen said.
"The results suggest social closeness is more important than shared beliefs when evaluating others," Krienen added.
The study has been published in The Journal of Neuroscience.