14 DAY TRIAL // Racial distinction can be installed in the human brain at a very early age, as a mixed team from University of Southern California (USC), the Salk Institute for Biological Studies, and the University of California at San Diego (UCSD) has found.
Using a new technique, the researchers discovered unexpected brain regions that respond selectively to the cues of gender, ethnicity and identity in faces. "When looking at a face, its gender and ethnicity tends to be the first thing we notice," says Ione Fine, Ph.D., assistant professor of ophthalmology at the Keck School of Medicine of USC.
"We become sensitive to these cues remarkably early in life. If you look at how pre-school children classify faces you find that these very young children pay attention to gender, ethnicity and age. In contrast, small children barely notice if a person is wearing eyeglasses. We wanted to see what was happening in the brain."
For three minutes, the subjects were presented a series of male Mongoloid and female White face images. After that, they were presented occasional female Mongoloid and male White face images and the researchers measured how the appearance of these faces was altered by the previous presentation. The adaptation (the previous exposure) altered the appearance of faces: male faces appear more White and female faces appear more Mongoloid. Then functional magnetic resonance imaging assessed brain responses.
An active region was the fusiform gyrus, a brain area previously associated with face processing. But, surprisingly, very active was also the cingulate gyrus, a brain area not previously linked to face processing. These brain areas also seemed to be sensitive to the cues of identity, suggesting that they may also be involved in recognizing individuals. "A surprising percentage of the population -maybe 2 to 3% of the population- have a real inability to recognize faces or even tell if someone is a male or a female," says co-author Minna Ng, a graduate student at UCSD.
"In the most extreme cases it's a clinical condition called prosopagnosia. Until now, most people assumed that difficulties with face recognition were due to cortical deficits near the fusiform gyrus. These data suggest that other brain regions may be involved. The fact that the cingulate gyrus is involved has some interesting implications for conditions like autism spectrum disorders."
The capacity of recognizing gender and race seems to be an automatic process. "Adults show large variations in how good they are at recognizing faces, and if you are bad at it, it can be very stressful and embarrassing," says Fine. "Perhaps if we have a better understanding of how face categorization develops, we can eventually develop ways of helping people get better at it."