For human beings, our faces are our calling cards. They tell the world who we are and often how we are feeling. The youngest infants have a special affinity for faces, and the human brain devotes some of its most basic structures to recognizing faces and the subtleties of facial expression. Now a study using sophisticated imaging technology has shown that how a key part of the brain reacts to faces can differ depending on whether individuals are looking at faces from their own racial group or from another racial group. The report from researchers at the Massachusetts General Hospital (MGH), Amherst College, and other institutions appears in the August 2000 issue of NeuroReport.
"One of the most exciting things about this study is how it shows the potential of applying powerful imaging techniques to questions of social psychology," says Scott Rauch, MD, director of psychiatric neuroimaging research at MGH, who is the paper's senior author.
Allen Hart, PhD, chair of the Department of Psychology at Amherst, the paper's first author, adds, "As long as scientists are very careful about how they interpret the results of studies like this, this represents a major new tool to help advance the field."
Located deep within the brain, the amygdala acts as a sort of administrator for the brain, receiving sensory signals and flagging those that need extra attention. While fundamental studies of the amygdala have identified its role in recognizing fear and other strong emotions, recent information points to a more complex situation. Study co-author Paul Whalen, PhD, has theorized that increased activity in the amygdala is a sign of vigilance, a way for the brain to send out a request for more information. Whalen was formerly at the MGH and is now at the University of Wisconsin.
Much current understanding of the role of the amygdala has come from studies using functional magnetic resonance imaging (fMRI), a technique that reveals brain activity as well as structure. In numerous earlier investigations, researchers at several centers have measured the amygdala's response by scanning volunteers as they viewed photos of faces with a variety of standardized emotional expressions. However, the faces used in such studies usually have been Caucasian. Although psychological research from several groups has shown that people more readily recognize previously viewed faces from their own race, no one had examined whether or not amygdala reaction might differ depending on whether people are viewing faces from their own race (ingroup) or another race (outgroup).
In the current study, conducted at the MGH NMR Center, eight volunteers were briefly shown a series of faces while undergoing fMRI scans. The volunteers - four white people, four black people, with two men and two women in each group - were asked to indicate whether the faces were male or female. The facial images presented all were neutral in facial expression and evenly divided among black and white. Two sets of scanned brain images were taken several minutes apart.
The results showed differences in response to ingroup and outgroup faces for both black and white participants. While amygdala response to all faces was elevated in the first scans, during the second scans there was a reduced response to the ingroup faces only.
Rauch says: "These findings could suggest that people become familiar with elements of ingroup faces more quickly than they do for outgroup faces." But the researchers caution against drawing premature conclusions from the results of this small study.
"There are a lot more questions we need to answer," says Hart. "Whether the difference in response would diminish with greater exposure to outgroup faces; whether the same types of responses would be seen with other racial groups than the ones we tested; and whether the amount of personal contact study participants have with outgroups makes a difference. And we're hoping to investigate these questions in future studies."
The researchers say that one practical implication of the study is illustrating the need to account for ingroup/outgroup differences in future amygdala studies.
Other co-authors of the paper are Lisa Shin, PhD, of Tufts University; Sean McInerney of the MGH, and Hεkan Fischer, PhD, of Uppsala University in Sweden. The study was supported by an Amherst College Faculty Research Grant.
The above story is based on materials provided by Massachusetts General Hospital. Note: Materials may be edited for content and length.
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