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Interpreting Intent

Studying the neural basis of human social interaction

Two Dartmouth researchers have learned more about how the human brain interprets the actions and intentions of others. Scott Grafton, professor of psychological and brain sciences, and Antonia Hamilton, a post-doctoral fellow, have learned that the brain's parietal cortex handles how we understand the goals of other people's actions. Their study was published on January 25 in the Journal of Neuroscience.

Antonia Hamilton
Post-Doctoral Fellow Antonia Hamilton is investigating how the human brain understands the motives of others. (photo by Joseph Mehling '69)

"We were able to find the part of the brain involved in interpreting the goal of another person, even if no words are spoken," says Hamilton. "When you see another person reach for an object that they want, like a cookie, a bit of the brain called the anterior intraparietal sulcus, which is found in the parietal lobe, is strongly activated."

Hamilton explains that the result is surprising because many would have predicted that the frontal cortex, normally associated with language and understanding, would be activated in this situation, not the parietal cortex, usually thought to be involved with space and movement. Also, Hamilton says that with this study, they have shown it's possible to localize abstract things, like goals, in the brain.

"So, as we learn more about how the brain responds to seeing other people do things, we can start to understand the neural basis of human social interactions. This may help us understand what goes wrong in impaired social interactions, like those of children with autism, who sometimes fail to interpret actions correctly," she explains.

The study involved twenty participants who watched a series of short movies, shown in a random order, while their brain activity was measured by functional magnetic resonance imaging (fMRI). The movies depicted a hand reaching, grasping, and taking one of two objects. For example, a hand took a cookie or a computer disk. The participants then answered "yes" or "no" questions that elicited their understanding of the goals involved in the actions represented in the movies.

The study was funded by the James S. McDonnell Foundation and the National Institutes of Health.

By SUSAN KNAPP

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Last Updated: 12/17/08