Your social brain

Nerve cells notice mistakes and learn from others’ desires


Some nerve cells snicker at mistakes. Others compel a person to want someone else’s stuff. By studying these phenomena, scientists are learning more than just where schadenfreude and jealousy lie in the brain; they’re gaining an unprecedented view of how social influences can worm into a person’s head.

Such new results carry researchers beyond studying the brain in isolation to studying it as a social actor. Ultimately, this work could help forge a deeper understanding of how the brain learns by using the behavior of others as a guide.

Earlier this year, Japanese researchers uncovered a small group of nerve cells that fire when a macaque witnesses another monkey making a mistake. These cells, located in the front of the brain, remained silent when a monkey made an error itself, but howled when the monkey saw a partner screw up (SN: 9/8/12, p. 12). Humans probably have similar cells, says study coauthor Masaki Isoda, now at Kansai Medical University in Osaka, Japan.

Finding cells that respond to another animal’s error but not to the monkey’s own mistakes was a surprise, showing that the cells behave distinctly from those in the brain’s mirror neuron system. A collection of nerve cells that are active while a subject is both doing and observing another doing, the mirror neuron system has been proposed as a way for the brain to make sense of the actions of others. But these new results, and others like them, paint a more complex picture.

Other research reveals more about how the mirror neuron system helps the brain learn from others. In a different social setting, mirror neurons team up with another system in the brain — the bean-counting system — to make an object in someone else’s possession automatically more desirable (SN: 6/30/12, p. 12). French researchers found that candy, tools and clothes in someone else’s hands held more allure than an untouched object, a copycat phenomenon called “mimetic desire” by the philosopher René Girard.

This automatic upgrade happens in two steps, the researchers found: Initially, the mirror neuron system detects that someone else has something of interest. Then, that information gets sent to the brain’s value-assigning system, which adjusts the value of the object upward.

Although these traits — coveting possessions and nitpicking mistakes — are things parents teach their children not to do, they may serve an important function, researchers say. Watching what other people do wrong and what they acquire can yield valuable information about how to get along in this world.

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

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