Human brains seem to be hard-wired to recognise and respond more to friends than strangers, a new Harvard study has found. The brain-imaging study showed that increased activity in a network of brain regions took place when participants viewed pictures of themselves and thought about themselves as well as when they thought about friends regardless of their similarities to each other.
Previous studies have suggested whether another person is similar to you is an important dimension in our social world and played a role in humans’ survival.
“The theory is that we can only understand the minds of other people to the extent that we view them as similar enough to us,” said Fenna Krienen who led the research at Harvard University.
The team figured closeness might also play a role. “Maybe closeness would also be an important dimension to explore, because we are a social species, we may have evolved with a need to recognise and respond differently to people who are part of our social alliance, part of our clan,” Krienen told LiveScience. To find out, the researchers imaged brain activity of the participants as they judged how well lists of adjectives described their personalities as well as that of former President George W Bush. This test revealed which brain regions are linked to personal, “self” information. In three other experiments, a total of 66 different participants provided personality information about themselves and two friends — one friend who they believed had similar preferences and one believed to be dissimilar. That information was also used to create fictitious biographies of two “strangers” for other participants. Then, while in a brain scanner, the participants played a game in which they predicted how another person would answer a question. For example, “Would a friend (or stranger) prefer an aisle or window seat on a flight?” When answering questions about friends, both similar and dissimilar,
the participants showed increased activity in the brain’s medial prefrontal cortex and associated regions.
“It was interesting to us, because the same network that was active when people saw pictures of themselves was also highly active when they answered questions about their friends,” Krienen said.