Blushing betrays deception, a new study in today's issue of Nature suggests. The authors claim the finding could lead to improvements in lie-detecting technologies, but one expert says he doubts this is a valid way to catch an impostor.
Unlike standard polygraph tests, the new technique -- which uses remote, high-definition thermal imaging cameras -- would not require physical contact or a skilled staff.
The technology was developed to detect disguises, such as heavy makeup or wigs, which distort the normal heat energy patterns of the face and head. However, researchers at the Mayo Clinic and Honeywell International Inc. then hit upon the idea of using the device as a lie detector.
Norman L. Eberhardt, a consultant professor of medicine at the Mayo Clinic, enrolled 20 volunteers in an experiment performed at the U.S. Department of Defense Polygraph Institute.
Eight volunteers were randomly assigned to stab a mannequin, "steal" $20, and then testify they didn't commit the crime. Meanwhile, the other 12 people, who knew nothing about the crime, also testified to their own innocence.
During questioning, the volunteers took conventional polygraph tests. High-resolution thermal images were also taken of the area around their eyes, both before and after they were asked, "Did you steal the $20?"
The cameras took pictures at a rate of 30 frames per second, each capable of capturing temperature changes as small as 0.025 degrees Celsius. The camera could detect changes in blood flow and temperature around the eyes, although the effect was invisible to the naked eye.
"We've speculated that this response that's measured the blood rushing to the eyes could be part of a 'fight-or-flight' response," says Eberhardt. "It could be that the rush of blood to the eyes is part of an alert to allow the eye more essential nutrients to do its job."
The traditional polygraph tests determined that six of the eight "guilty" volunteers were lying, while eight of the 12 "innocent" volunteers were judged as truthful, giving the polygraph test an overall accuracy rate of 70 percent.
The thermal imaging system was more exacting: Six of the eight guilty volunteers were judged liars, and 11 of the 12 innocent volunteers were determined innocent, translating into an overall accuracy rate of 83 percent.
"With further testing and further confirmation, it could be a type of remote lie detector," says Eberhardt. Tests using the cameras to detect disguises have shown that a device mounted on a roof overlooking a parking garage could still pick up changes in thermal energy.
David T. Lykken, an expert in conventional polygraph technology, says the technology has the advantage of not requiring physical contact. In fact, he says, the cameras could watch someone surreptitiously. However, the device shares the same flaw as conventional lie-detection technology, he adds.
"If you're accused of a crime and you're guilty, and you're asked if you did it, then naturally you're going to show an autonomic nervous system response," says Lykken. "You're going to be disturbed, your heart rate will go up, your palms will sweat, your pupils will dilate." At the same time, he says, your face will tend to flush.
"The problem is that if you're innocent, you'll show the same reaction, and that's why the lie detector doesn't work," he says.
However, he anticipates that security concerns since the terrorist attacks of Sept. 11 could speed up development of technologies for detecting deception.
"There's going to be a lot of technology in this direction," Lykken says. "I hope it's not lie detection, though, because that's invalid."
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