When do we start to develop social intelligence? It might be younger than you think

To investigate how infants’ brains process other people’s actions, researchers measured the brain activity of 36 infants while they watched an actor reach for one of two toys.

Immediately after, the seven-month-old infants were allowed to select one of the same toys. This procedure was repeated 12 times.

The results show the babies’ brain activity, measured using EEG, predicted how they would respond to the actor’s behavior.

When the infants recruited their motor system while observing the actor grasp one of the toys, they subsequently imitated the actor. When they didn’t imitate the actor, there was no detectable engagement of the motor system in their brain activity as they watched the actor.

Fundamentally, the researchers identified the neural processes that contribute to intelligent social behavior in infants. And it’s the first evidence that motor system activation in infants predicts the imitation of others’ actions, as well as an apparent understanding of others’ goals.

“This is big news, that babies understand what they are observing, that there is a direct connection between observing others, understanding what others are doing, and learning how to act,” says study coauthor Amanda Woodward, a psychology professor at the University of Chicago.

Never tested in infants

The researchers used EEG to measure a component of brain activity—desynchronization of activity in the mu frequency band—that has been linked to motor cortex activity in adults. Like adults, infants show this response when acting themselves and when watching others’ actions, suggesting that the motor system may play a role in the perception of others’ actions.

Until the current study, however, this possibility had not been tested in infants.

“This research tells us that, by the middle of their first year of life, babies are beginning to be able to understand that people act intentionally—that they choose one toy over another because they want that toy,” says Helen Tager-Flusberg, professor of psychological and brain sciences at Boston University, who is familiar with but was not involved in the research. “This understanding on the part of a baby involves not just seeing the other person’s action, but also involves the baby’s own motor system, which is recruited when he or she chooses the same toy.”

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The researchers’ methodology also broke new ground. “This is the first attempt to combine the assessment of infants’ behavior—in this case, imitating the actions of another person—with measuring brain activity in infants,” Tager-Flusberg says.

“Probably the hardest place to study the relation between brain activity and behavior is with infants, due to limitations in the methods that can be used, and the fact that infants are infants,” Woodward notes. “Our methodology represents a breakthrough and a proof of concept.”

“We’ve worked hard over the years to develop the methods that allow us to record brain activity from infants while they are engaged in the social world,” says coauthor Nathan Fox, a professor at the University of Maryland, College Park. “The current research reflects our ability to synchronize brain and behavior in infants during the first year of life.”

Although this research will not translate directly into new medical treatments or therapies, it could contribute to medical advances down the road by helping to illuminate how the human brain functions and develops, Woodward adds.

“One reason to engage in basic science is to better understand the development of the brain and mind. Here we looked at the development of social cognition, social behavior, and the motor system, all of which are critical for human development and are often disrupted in developmental disabilities, including autism.”

The Eunice Kennedy Shriver National Institute of Child Heath and Human Development funded the study, which appears in the journal Psychological Science.