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Brain network for social understanding develops in early childhood

Researchers studied development of the brain areas we use to interpret other people’s states of mind. ASIFE/iStock/Thinkstock

Understanding other people’s minds and being able to guess what they believe, what they want, or how they feel is important for social interactions. This ability is called a “theory of mind.” Behavioral studies have shown that children start using information about other people’s beliefs to predict or explain their behavior around age four.

To characterize the brain regions involved in the development of a theory of mind, a team of researchers led by Hilary Richardson and Dr. Rebecca Saxe at the Massachusetts Institute of Technology used fMRI to study the brain activity of 122 children, aged 3 to 12 years, and 33 adults while they viewed a short animated movie showing the characters’ physical and mental states. The research was supported in part by NIH’s National Institute of Mental Health (NIMH). Results were published in Nature Communications on March 12, 2018.

The scientists compared participants’ brain activity while they watched scenes depicting the characters’ physical state (experiencing pain) or mental state (their emotions, beliefs, and desires). Studies have shown that two separate brain networks are activated when thinking about other people’s physical or mental states. The researchers measured activity in these two brain networks.

Children, even as young as three, had largely similar responses to adults in the two brain networks. Scenes that showed physical pain drove responses in one network, while scenes that showed mental states drove responses in the second brain network. But the older the children were, the more their brain activity looked like the adults. Over time, the brain network activity for physical pain became more distinct from the network responding to the social scenes.

Following the brain scan, each child was given a series of classic behavioral tests to measure theory of mind reasoning. The researchers found that activity in the social brain network was related to theory of mind development.

One of the major milestones studied in theory of mind development is whether a child has the ability to reason about another person’s false beliefs. However, the team tested for this milestone and found that it didn’t mark the formation of the brain network for theory of mind.

“Scientists have focused really intensely on the changes in children’s theory of mind that happen around age four, when children get a better understanding of how people can have wrong or biased or misinformed beliefs,” Saxe says. “But really important changes in how we think about other minds happen long before, and long after, this famous landmark. Even two-year-olds try to figure out why different people like different things—this might be why they get so interested in talking about everybody’s favorite colors. And even nine-year-olds are still learning about irony and negligence. Theory of mind seems to undergo a very long, continuous developmental process, both in kids’ behaviors and in their brains.”

—Tianna Hicklin, Ph.D.