Neuroscientists and developmental psychologists have teamed up to show, for the first time, that infants’ motor-system brain activity is directly linked to their social behavior.
The study, published April 12, 2016 in Psychological Science, tracked brain responses and choices made by infants to identify how observing others’ actions relates to infants’ own interactive behavior.
Researchers tested thirty-six 7-month-old infants while recording brain activity with an electroencephalography (EEG) cap. In each trial an actor reached for one of two toys while the infant watched, and immediately afterward the infant was allowed to select one of the same toys. This sequence was repeated across 12 trials for each baby.
The key finding was a clear predictive link between neural activity in the infants’ motor system during observation and their subsequent behavior. When an infant’s EEG showed engagement of the motor system while watching the actor reach for and grasp a toy, that infant was likely to imitate the actor by choosing the same toy. Conversely, when the motor system did not show measurable engagement while watching the action, the infant typically did not imitate.
Lead author Courtney Filippi, a doctoral candidate in developmental psychology at the University of Chicago, summarized the result: “Our research provides initial evidence that motor system recruitment is contingently linked to infants’ social interactive behavior. It provides initial evidence that recruiting the motor system during action encoding predicts infants’ subsequent social interactive behavior.”
Untested possibility
To measure motor-system engagement, the team focused on desynchronization in the mu frequency band of the EEG signal, a pattern previously associated with motor cortex activity in adults. Like adults, infants display mu desynchronization both when they act themselves and when they observe others acting. Prior to this study, the connection between that neural signal and real social behavior in infants had not been directly demonstrated.
Helen Tager-Flusberg, professor of psychological and brain sciences at Boston University who was not involved in the study, explained the developmental significance: “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. 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.”
By linking motor-system activation to imitation and apparent goal understanding, the researchers identified neural processes that contribute to intelligent social behavior early in life. “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,” said co-author Amanda Woodward, the William S. Gray Professor of Psychology at the University of Chicago.
Proof of concept
The experimental approach also represents an important methodological advance. Recording reliable brain activity from infants while synchronizing those signals with moment-to-moment behavior poses many practical challenges. “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 noted. “Our methodology represents a breakthrough and a proof of concept.”
Nathan Fox, Distinguished University Professor at the University of Maryland, College Park and co-author on the paper, added: “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. The current research reflects our ability to synchronize brain and behavior in infants during the first year of life.”
Although the findings do not immediately produce new clinical treatments, they deepen basic scientific understanding of brain and social development. Woodward pointed out that studying early social cognition, social behavior, and motor-system development is important because these processes are essential for human development and can be disrupted in developmental disabilities, including autism.
Funding: This research was supported by the National Institutes of Health under grants NS081490, HD078703, and 5T32CA967334; and by the American Cancer Society and the Murray Foundation.
Source: Steve Koppes – University of Chicago
Image Credit: The image is in the public domain.
Original Research: The study was published in Psychological Science on April 12, 2016.