Brain structure acclimates more quickly to same-race pictures

People’s brains respond differently to pictures of faces representing their own race compared with those of another race, according to an initial study appearing in the current issue (Aug. 3, 2000) of the journal NeuroReport.

UW brain imager and amygdala neuroscientist Paul Whalen is a co-author of the study, which took place while he was a faculty member at Harvard Medical School. The study was conducted in collaboration with neuroimager Scott Rauch of Massachusetts General Hospital and social psychologist Allen Hart of Amherst College.

Adults who identified themselves as black or white were shown photographs of white and black faces. Researchers measured activity in an area of the brain known as the amygdala with functional magnetic resonance imaging (fMRI). Two scans approximately two minutes apart were taken as subjects viewed the same 20 pictures.

In the first scan, the amygdala responded similarly to faces of the same race (called ingroup) and different race (the outgroup). In the second scan, however, the amygdala responded significantly less strongly to ingroup faces while maintaining a greater response to outgroup faces.

“The amygdala is habituating to, or becoming familiar with, ingroup faces more quickly than to outgroup faces,” explained Whalen, assistant professor of psychiatry and psychology, and a member of the UW HealthEmotions Research Institute‘s new Keck Neural Imaging Center.

The finding supports evidence from prior studies showing that the amygdala is sensitive to biologically relevant and socially important stimuli, such as facial expressions of emotion.

“This complex structure is usually thought of as an emotional center in the brain, but we’ve also shown that it can have a more continuous influence over a person’s moment-to-moment level of vigilance,” Whalen said. “When the amygdala encounters a stimulus that it would like more information about, it alerts other brain systems, which respond with additional information about what is going on in the environment.”

The fact that the different amygdala responses seen in the study developed over time implies that the responses were not related to an emotional reaction, noted Whalen. “Indeed, our study subjects reported no noticeable emotional reaction to either the ingroup or outgroup faces.”

Basic research on the amygdala suggests that this brain area will continue to respond to stimuli with which it has less experience, he said.

“In our study, we assume that amygdala response was maintained to outgroup faces because subjects had less experience with these faces,” he said. “In this way, amygdala response has less to do with skin color, and may have more to do with what your eyes have seen throughout your life.”

It will be important that future studies measure variables such as experience, assess the contribution of other brain regions in processing socially significant stimuli, and determine the applicability of these findings to other racial groups, he said. Researchers at New York University and Stanford are also currently studying brain responses to race.