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A fearful expression can heighten senses

June 21, 2008|Denise Gellene | Times Staff Writer

The look of fear is unmistakable: wide eyes, raised brows, a dropped jaw. But is it more than a social signal?

In this week's journal Nature Neuroscience, University of Toronto researchers reported that fearful expressions evolved to heighten the senses and improve detection of physical threats.

Scientists asked 20 college students to assume fearful and neutral faces and measured their field of vision each time.

Fearful expressions enlarged the vision field by 7.6% compared with a neutral expression, presumably making it easier to spot an attacker. Scientists also measured eye movements and found that increased scanning took place when students' expressions mimicked fear.

"When you're fearful, you need to gather as much information as possible," said lead author Joshua M. Susskind, a graduate student in psychology.

In another experiment, scientists found that squinting the eyes in an expression of disgust narrowed the field of vision from a neutral facial position by 8.9%. In addition, eye movements slowed.

"Disgust is a protective mechanism to withdraw from the environment," Susskind said.

The facial reactions were useful to primitive humans, who faced continual danger from the environment. However, they can be counterproductive in the modern world, where social threats have largely replaced physical ones, Susskind said.

"Let's say you have a fear of public speaking," Susskind said. Enlarging the field of vision "wouldn't be adaptive in a case like that."

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denise.gellene@latimes.com

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