The science behind reading faces

PHILADELPHIA, Feb. 16 (UPI) -- When someone rolls his eyes at your off-color joke, your brain begins to recognize the implied criticism within two-tenths of a second, a Duke University neuroscientist says.

Gregory McCarthy said today he's found the swiftness of the response depends on a special brain mechanism that only recognizes motions of the eyes and mouth.

He speculated that the mechanism may have evolved to help us communicate.

``The brain may need a dedicated region to process facial movements,'' McCarthy said, ``because eye and mouth movements convey a lot of information, including important social signals.''

He added that we unconsciously get clues about what people are saying by watching their lips move.

McCarthy said the mechanism has been located, using a technique called functional magnetic resonance imaging, on the side of the brain in an area known as the lateral temporal region.

It's near -- but separated from -- regions of the brain already known to process other kinds of motion, like the path of a thrown ball or the fall of a leaf, he said.

Details of the experiment are to be published next month, he told reporters at the annual meeting of the American Association for the Advancement of Science in Philadelphia.

McCarthy also said he has found that people begin to recognize faces within two-tenths of a second -- again using a special dedicated brain mechanism -- but not other kinds of objects, such as flowers.

He speculated that this mechanism evolved because it's important for humans to recongize faces quickly.

``There's survival value in being able to recognize faces,'' he said, especially if the face belongs to your worst enemy.