What's more universal in culture than a "thumbs up"?

To our brains, whether we seem to have a cultural familiarity or not, it isn't familiar at all, says new research in Human Brain Mapping.

People seem to react quickly and intuitively to body language, tone of voice and gaze but gestures are different, at least when the gesturer offers no other cues.    Less surprisingly, the new study also found that same-race interaction leads to greater activity in the mirror neuron system, a region of the brain linked to subconscious imitation.

Neuroscientists at USC and Peking University asked 18 ethnically Chinese volunteers to interpret gestures made by Chinese and Caucasian actors trained to remain expressionless.  The gestures were either highly familiar (like the thumbs-up sign) or utterly foreign (words from American Sign Language), as confirmed by a separate group of Chinese volunteers.

Functional magnetic resonance imaging (fMRI) was used to observe the volunteers’ brains as they viewed video clips of the actors performing the gestures.   The “mentalizing” system - a part of the brain linked to reflective, non-intuitive reasoning - showed greater activity in response to familiar gestures. This was true regardless of the actor’s race.

Unfamiliar gestures were associated with greater activity in the more intuitive mirror neuron system.

They say the finding contradicts previous studies showing a relationship between familiar stimuli and mirror system activation.   The study’s senior author, Lisa Aziz-Zadeh assistant professor in the USC Brain and Creativity Institute, speculated that the mentalizing system is necessary to think about the meaning of a gesture.

Lisa Aziz-Zadeh
Lisa Aziz-Zadeh.  Credit: USC

“When you watch familiar gestures, you activate the mirror system … but you additionally recruit the mentalizing system,” Aziz-Zadeh said.   This suggests that humans size up each other not only by using their own motor representations but also through deliberate analysis of the other’s words and actions.

The research was funded by the National Natural Science Foundation of China, the National Basic Research Program of China, the Fundamental Research Funds for the Central Universities (China), the National Science Foundation East Asia and Pacific Summer Institutes, the National Science Foundation Graduate Research Fellowship, the USC Provost’s Ph.D. Fellowship, the USC Brain and Creativity Institute and the Division of Occupational Science and Occupational Therapy at the Ostrow School of Dentistry.

Citation: Sook-Lei Liew, Shihui Han, Lisa Aziz-Zadeh, 'Familiarity modulates mirror neuron and mentalizing regions during intention understanding', Human Brain Mapping, Article first published online : 29 SEP 2010, DOI: 10.1002/hbm.21164