Brain responds more to close friends than strangers

WASHINGTON - People’s brains are more responsive to their friends than strangers, even if the stranger has more in common with them, study shows.

Researchers at Harvard University examined a region of the brain known to be involved in processing social information. The team obtained results which suggest that social alliances outweigh shared interests.

The study, led by graduate student Fenna Krienen and senior author Randy Buckner, investigated the process by which the brain’s medial prefrontal cortex and associated regions signal a person’s value in a social situation.

Medial prefrontal cortex is the region linked with personality expression, decision making and social behaviour.

The researchers probed whether these regions respond more to those we know, or to those with whom we share similar interests.

“The results suggest that social proximity is the primary factor, rather than social similarity, as previously assumed,” Krienen said.

The researchers mapped the cerebral activity of a group of participants as they judged how appropriately a list of adjectives described them. This was done to identify the regions of the brain which respond to personally relevant information.

In a separate experiment, 66 persons provided information about themselves and two of their friends, one of whom had preferences similar to them.

The authors then prepared 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 are asked to predict how another person would answer a particular question.

The authors found that activity in the medial prefrontal cortex increased when people answered questions about friends. Notably, whether the person had common interests or not made no difference to the brain’s response.