By one account, the first lie in the history of the world came when Cain invented the "who, me?" defense and denied knowing anything about the murder of his brother, Abel. Ever since then, people have been trying to figure out how to detect when someone -- a spouse, a criminal, a president -- isn't telling the truth.
Now, about a century into the scientific exploration of lying, American researchers are exploring lie-detection technologies that may banish polygraph machines to the history books.
At the University of Houston, a computer scientist is trying to uncover lies by measuring heat levels in the face. In South Carolina, a professor hopes she has found the key to deception in brain waves. Elsewhere, researchers are looking at everything from speech patterns to eye movements to "brain fingerprints."
Success remains elusive, however, and no newfangled lie-detection machines appear ready for prime time. Skeptics, meanwhile, doubt that any technology will improve much on the mixed record of polygraph machines, which are often used in the United States to screen employees and test the truthfulness of criminal suspects.
"A lot of people believe there is some particular reaction that you give when you're lying but not when you're telling the truth, but that's false," said David Lykken, professor emeritus of psychology at the University of Minnesota. Studies show that polygraphs do a fairly effective job of detecting liars by picking up on stress levels, but they also produce "false positives" -- suggesting that a truth teller is lying -- and appear to be susceptible to manipulation by subjects.
Enter the polygraph alternatives. According to Lykken, the most effective lie-detection technique isn't a traditional polygraph examination but instead a "guilty knowledge" test, in which a polygraph machine measures the reactions of people when they see several items. If they glimpse an item that's familiar -- like a knife or gun -- their bodies should respond differently as recognition dawns on them.
The problem with this technique is that it requires interrogators to have special knowledge, such as details of a crime that haven't shown up in the media, said Jennifer Vendemia, professor of psychology at the University of South Carolina. She's turned instead to the study of brain waves.
"When you tell a lie, it's a cognitive behavior like any other, like doing an interesting math problem," she said. "You have to engage in a certain number of cognitive activities -- you have to pull the truthful information from your memory, inhibit that information, create a deceptive response and make a decision to deliver that response. You have to engage in these steps to tell a lie, a complicated process involving different parts of the brain."
Vendemia is developing ways to measure these different steps in the brain. She says her brain-wave tracking system can detect 94 percent of lies in laboratory tests.
Others are looking elsewhere for clues to deception, from eye movement to verbal giveaways. Some, like Vendemia, think the answer lies under the skin. Using a thermal-scanning device whose hardware alone cost more than $200,000, two researchers say they've found a way to detect stress by measuring blood flow in the face.
In 2002, University of Texas computer science professor Ioannis Pavlidis and Mayo Clinic endocrinologist James Levine reported (.pdf) that heat around the eyes -- a sign of increased blood flow -- appeared to uncover six of eight lying subjects. The scanner identified 11 of 12 truth tellers as honest.
The trick is to figure out which signs of stress in the face reveal deception, Pavlidis said. (Polygraph examiners face a similar challenge, according to Lykken, who said the problem with lie detectors is that "all you get from measuring any of the responses is that a subject is emotionally aroused, disturbed or surprised by this question, but you don't know what that means.")
According to Pavlidis, whose goal is a "more reliable, more user-friendly, more automated" lie detector, a new study on thermal facial scanning should appear in mid-2005.
But when will a better lie detector show up? Vendemia predicts it might be as soon as 2010, perhaps using elements of thermal facial scans, brain scans and other technology.
Don't hold your breath, said Thomas O'Connor, an associate professor of justice studies at North Carolina Wesleyan College who teaches about lie detection.
"You'll have a situation where you're pitting human nature up against machines, and human nature is going to win this particular battle," he said. "I think lying is here to stay."
Polygraphs Don't Give True Story
