This is your brain on hand gestures


Published Jul 18, 2007 3:24 PM

How your brain responds to a "thumbs up" and other hand gestures depends on who you are and who's doing the gesturing. Culture and ethnicity play a part in whether or not the brain's neurons fire in response to a gesture, say UCLA brain researchers Istvan Molnar-Szakacs and Dr. Marco Iacoboni.

The "I'm good" of a thumbs-up is readily recognized in American society, as is the infamous middle-finger salute. But to someone from a foreign country, they may be incomprehensible. Likewise, an American in a foreign land may be clueless as to that culture's gestures.

For UCLA's brain scientists, this raises a provocative question: Does culture influence the brain?

Yes, say Molnar-Szakacs, a researcher at the UCLA Tennenbaum Center for the Biology of Creativity, and Iacoboni, director of the Transcranial Magnetic Stimulation Lab at the Ahmanson-Lovelace Brain Mapping Center at UCLA’s Semel Institute for Neuroscience and Human Behavior.

Your mirror neuron network is watching

The researchers wanted to investigate the imprint of culture on the so-called mirror neuron network. Mirror neurons in the brain fire not only when a person performs a particular action but also when he or she watches another person perform that same action.

Neuroscientists believe this "mirroring" explains how we can "read the minds" of others and empathize with them.

The mirror neuron network responds differently depending on whether or not a person is looking at someone who shares his culture, the researchers discovered.

In the study, two actors — one American, the other Nicaraguan — perform a series of American, Nicaraguan and meaningless hand gestures for a group of American subjects. A procedure called transcranial magnetic stimulation was used to measure the observers' levels of corticospinal excitability, which scientists use to gauge the activity of mirror neurons.(See a streaming video of the gesturers.)

The American observers demonstrated higher mirror neuron activity when observing the American making the gestures — whether the gestures were American, Nicaraguan or meaningless — than when viewing the Nicaraguan. Even when the Nicaraguan actor performed American gestures, the observers' mirror neuron activity dropped.

Culture-specific stimuli turns neurons on

"We believe these are some of the first data to show neurobiological responses to culture-specific stimuli," said Molnar-Szakacs. "Our data show that both ethnicity and culture interact to influence activity in the brain, specifically within the mirror neuron network involved in social communication and interaction."

"We are the heirs of communal but local traditions," said Iacoboni. "Mirror neurons are the brain cells that help us in shaping our own culture. However, the neural mechanisms of mirroring that shape our assimilation of local traditions could also reveal other cultures, as long as such cross-cultural encounters are truly possible.

"All in all, our research suggests that with mirror neurons, our brain mirrors people, not simply actions."

Neural systems supporting memory, empathy and general cognition encode information differently depending on who's giving the information — a member of one's own cultural or ethnic in-group or a member of an out-group. Ethnic in-group membership and a culturally learned motor repertoire more strongly influence the brain's responses to observed actions, specifically actions used in social communication.

"An important conclusion from these results is that culture has a measurable influence on our brain and, as a result, our behavior. Researchers need to take this into consideration when drawing conclusions about brain function and human behavior," said Molnar-Szakacs.

The findings, the researchers note, may also have implications for motor-skill acquisition,language learning and intergroup communication, as well as for the study of intergroup attitudes toward other cultures.

Other study authors include Allan D. Wu and Francisco J. Robles, both of UCLA. Molnar-Szakacs and Iacoboni are members of the Foundation for Psychocultural Research–UCLA Center for Culture, Brain and Development, which provided funding for the study.

A paper on their research appears in the current issue of the journal PLoS ONE .



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