Larger social networks — especially earlier in life — leads to larger brain development

The World

Story from PRI’s The World. Listen to the above audio for a complete report.

New research suggests human social interactions leave a physical trace in our brains and scientists say it reveals the importance of rich social experiences early in life.

The study, out of the U.K. was done with monkeys, but humans share a great deal with primates, including having relatively large brains compared to other animals.

“There’s been quite a debate on why is it that our human brains and the brains of other primates are so enormously big,” said Rogier Mars, a neuro-psychologist at the University of Oxford.

One theory is that primates evolved with bigger brains to manage complex social lives.

“They have to keep track of who’s dominant, who’s been friendly to you in the past, who you have to be friendly with in order to have access to food, to have a good life really,” Mars said.

But Mars and his colleagues were interested in a related question: If large brains enable complex social interactions, could social interactions in turn affect the structure of an individual’s brain? To answer that question they worked with a research facility that housed rhesus macaques for a range of scientific experiments.

Mars says the monkeys were already kept in groups of different sizes.

“Some are singly housed, some have one friend, and some have bigger groups.”

The researchers wanted to know if the brains of monkeys in the larger groups were different from the brains of monkeys in the smaller groups. So they did MRI scans of the monkeys’ brains, and found that indeed there was a difference.

Two parts of the brain were noticeably larger in monkeys that lived in larger groups.

One of those regions is the temporal cortex.

It’s a region “that contains areas that are sensitive to facial expressions, to body posture, to emotional expressions, all areas that are involved in processing of social stimuli,” Mars explained.

The other region that was larger is the pre-frontal cortex, which sorts through information and helps us make decisions. The new study is an important one, said Lisa Barrett, a professor of psychology at Northeastern University in Boston.

“It shows that experience in social groupings can change structural aspects of the brain,” she said.

Many recent studies in humans have found a connection between the size of people’s social networks and the size of certain brain structures.

In fact, Barrett herself has shown that people with larger and more complex social networks have larger amygdalas, a part of the brain involved in processing social cues.

“These findings do strongly suggest that people who are exposed to larger and more complex social grouping will develop changes in their brain structures, that will be measurable and have visible effects in terms of emotional processing, and social ability,” she said.

Those with fewer social interactions early in life might be at a disadvantage later, said Robin Dunbar, a cultural anthropologist at Oxford University. He said this was an especially big concern today, when so many children spend so much time online, engaging in virtual interactions.

“You don’t learn how to handle relationships with other people when you do it online because you can simply pull the plug if they offend you,” Dunbar said. “You know you don’t have to sweat it out, you don’t have to find some sort of social compromise with them in the way that you have to in real life — in the sandpit, or play pit as it were.”

But online interactions may also affect the brain. A recent study showed that parts of the brain that process social cues are larger in people with larger online networks. However, those very same people also had large real-life networks.


PRI’s “The World” is a one-hour, weekday radio news magazine offering a mix of news, features, interviews, and music from around the globe. “The World” is a co-production of the BBC World Service, PRI and WGBH Boston. More about The World.

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