for National Geographic News
How do we recognize fear in another person?
Scientists have long known that the amygdala, an almond-shaped part of the brain, is critical for the perception of fear. But exactly what role it plays in recognizing facial expressions has remained a mystery.
A new study shows that the amygdala actively seeks out potentially important information in the face of another person. In particular, it focuses our attention on a person's eyes, the facial features most likely to register fear.
"These findings provide a much more abstract and general account of what the amygdala does," Ralph Adolphs said. Adolphs is a professor of psychology and neuroscience at Caltech University in Pasadena, California, and the University of Iowa in Iowa City.
Adolphs's study focuses on a 38-year-old woman with an amygdala that is damaged from a rare genetic disease. As a result, she is unable to recognize fear in people's facial expressions.
However, the scientists have found that she is able to recognize fear if instructed to concentrate her attention on a person's eyes.
Adolphs says the research could help those who suffer from other disorders such as autism, which can dull some people's ability to discern important facial signals.
The study is published in this week's issue of the science journal Nature.
Adolphs and his colleagues have studied the woman, known as SM, for more than a decade. She has a brain lesion in the amygdala. Not only can she not recognize fear, but she also fails to judge how trustworthy people look.
To find out how a person perceives fear in other people, the scientists had study participants look at photographs of fearful and happy faces through holes that revealed only small parts of the images.
People with normal brains always looked immediately at the eye region of a faceeven more so when the face was fearful.
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