Brain’s mirror system loves the robot

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SAN FRANCISCO — The next time you watch that guy on the dance floor do the robot to Mr. Roboto, his automatonic, jerky moves will speak to a surprising part of your brain: a region scientists thought was reserved for making sense of actions by others that you too are able to perform.

New experiments challenge a common view of this “mirror system” by showing that it’s not just a copycat, but is able to respond to a much wider range of actions than what an observer can perform himself.

This broadened capacity of the brain system may help explain how humans are able to quickly and effortlessly understand other people’s (and robot’s) actions, study coauthor Emily Cross of Radboud University Nijmegen in the Netherlands said April 2 in a presentation at the annual meeting of the Cognitive Neuroscience Society.

“There are a lot of situations where you see actions that you can’t do with your own body,” Cross said. “If you think about watching a gymnast at the Olympics, watching a break dancer, or even watching Star Wars or Wall-E, we see all sorts of actions and agents that we can’t readily map onto our own motor systems.”

To see just how the mirror systems responded to unnatural movements, Cross and her colleagues scanned the brains of 22 people as they watched a video of a man performing a natural, fluid dance or a machinelike robot dance. Researchers thought that parts of the mirror system, which includes parts of the parietal lobe at the top back of the head and the premotor cortex just in front of that, would show higher activation in an fMRI scan when the subjects watched the natural dance. Instead, parts of the mirror system showed a very strong signal when subjects watched the robot dance, a result that was “quite a surprise,” Cross said.

She and her team next tested whether the identity of the dancer made a difference by recording a video of a Lego figurine named Gresh, who performed the same dances as the original human dancer. Again, contrary to what the researchers expected, the mirror system regions in 23 new participants were more strongly activated by the robotic dance moves regardless of who was dancing.

The find that a weird robot doing a weird dance can activate the mirror system runs contrary to the notion that it is able to respond only to things that a person can do himself. “This is a very seductive hypothesis—that we use our own motor systems to understand the actions of others,” Cross says. But her results suggest that the mirror system is far more flexible, helping us understand the actions of things that are very unlike us.

Nevertheless, the findings “do make a lot of sense,” said neuroscientist Lisa Aziz-Zadeh of the University of Southern California in Los Angeles. Finding that these brain regions may react to less familiar behaviors and actors “may indicate that the mirror system is not just modulated by expertise, but also perhaps by attention, novelty, and other factors,” she said.

Figuring out just how the mirror system works will be “important for understanding the way we process individuals who differ from ourselves,” Aziz-Zadeh said. Seeing what happens when the brain is confronted with different types of dissimilarity — including race, personality, religion or body type, for instance — will be important, she said.

The brain’s mirror system responds strongly to unnatural, robotic dances, a new study finds.

MAN DOES THE ROBOT from Science News on Vimeo.

Brain regions that were conventionally thought to respond to actions that an observer himself can do also respond to a man doing the robot. Credit: Emily Cross

ROBOT DOES THE ROBOT from Science News on Vimeo.

Similar mirror system brain regions also respond to a robot doing the same unnatural, robotic dance. Credit: Carmen Hause

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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