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Finding fear in the whites of the eyes

Brain imaging studies in volunteers indicated that the amygdala, shown as a red and yellow spot, responded specifically to the wide-eyed image that was interspersed with images of neutral faces. Image Science
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It's pretty easy to recognize when someone is making a face that says "Holy Cow! This is really scary!" But what part of the face communicates this message? Is it the nose? The mouth? The eyebrows? The eyes?

By looking at the whites of your eyes, someone can tell if you're scared or surprised, new research suggests.

Paul Whalen, a scientist at the University of Wisconsin, Madison, and his colleagues think our eyes are the most important part of our faces for expressing fear. In particular, it's because our eyes widen when we're afraid or surprised, showing more of our eye-whites.

If you see a fearful expression on someone's face, your brain will start reacting to that expression in a flash -- even before you're consciously aware of what that person is feeling.

The part of the brain that reacts automatically like this is called the "amygdala." Its ultrafast reaction is probably helpful in dangerous situations, because it allows you to react automatically without taking the time to think about what's happening.

"When you see a fearful face, you don't know exactly what that person is dealing with. But, if they're afraid, maybe you should be too," Whalen said.

Imagine that you're looking at someone's face as they see an object flying toward your head. Before you have time to consciously think about what he or she is seeing, your brain can already be telling your body to get out of the way.

"You don't need to know whether it's a brick or a tennis ball," Whalen said. The important thing is that you duck your head.

Using special technology, Whalen's research team monitored the brain activity of volunteers who were shown a series of faces. In between each face, a pair of wide eyes appeared for a tiny fraction of a second -- too fast for the volunteers to be aware of what they were seeing. The researchers also included split-second images of eyes with smaller whites, indicating a happy expression.

The results showed that volunteers' amygdalae were responding only to the wide eyes. Whalen and his colleagues therefore concluded that large eye-whites are enough to send an "I'm afraid" message to someone's amygdala.

The authors describe their findings in the 17 December 2004 issue of the journal Science.


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