Brain Activity Reflects Complexity of Responses to Faces of Other Races
A region of the brain associated with emotional responses, the amygdala, is linked to a measure of unconscious race bias, especially when responding to faces presented subliminally, according to a study by researchers at Yale.
The study in the journal Psychological Science also indicates that other areas of the brain involved in deliberative thought processes can moderate the amygdala activity, suggesting that the conscious brain can compensate for unconscious prejudices.
The researchers assessed reactions of 13 white participants to faces displayed either subliminally, for three-hundredths of a second, or supraliminally, for slightly more than half a second. They found that amygdala activity was greater in response to black faces than to white faces in subliminal viewings. Also, the difference in amygdala activity to black versus white faces was greater among individuals who displayed higher degrees of racial bias on a subsequent and different test.
However, all of the participants expressed a personal interest in egalitarian behavior and disagreed with prejudiced statements. Consistent with these conscious beliefs, when faces were viewed for longer periods of time during the fMRI phase of the study, areas of the brain’s frontal cortex that are involved in inhibition and control took over and amygdala activity displayed less bias.
“These results suggest that even for nonprejudiced individuals, early perceptual processing may result in an automatic emotional response that may direct attention toward people of different groups,” said William Cunningham, lead author, former graduate student at Yale, and now professor of psychology at the University of Toronto. “Yet, with the opportunity to change or modify this initial impulse, they have the ability to do so.”
Mahzarin Banaji, professor of psychology at Harvard and co-author, said physical properties that make up a person cannot be disregarded in face-to-face interactions, and the imprint of culture is what is reflected in the response to a 30-millisecond subliminal exposure. “However, seeing the face consciously, for as little as a half second, allows a more reasoned response to the face in view.”
Marcia Johnson, psychology professor at Yale and co-author, said they also found greater amygdala response to black than white faces was associated with less activity to black than white faces in the fusiform gyrus, a brain area associated with face processing. Thus lack of “expertise” about other race faces may trigger an early emotional response than can be modulated by more conscious processing.
Co-authors include J. Chris Gatenby and John Gore of Vanderbilt University.
The National Institutes of Health, the National Institute of Mental Health, and the National Science Foundation supported the research.
Citation: Psychological Science, Vol. 15: pp 806-813 (December 2004)