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Better Lie Detectors
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Pants on Fire?
One of the memorable moments in the film "Meet the Parents" was Ben Stiller's profusely sweating brow as he sat strapped into a polygraph during his soon-to-be father-in-law's invasive questioning. Sweating, along with blood pressure, respiration, and heart rate are all physiologic conditions measured by polygraphs, with the idea being that they might reveal deception-induced anxiety.
Now, rather than focusing on the potential end-result of lying, Temple University scientists Scott Faro and Feroze Mohamed are developing a way to detect deception by looking directly at people's brain activity using MRI brain scanners.
"We are going to the source, we are going to the region of the brain which is actually formulating a response," says Mohamed, the MRI physicist on the team.
As Faro and Mohamed point out, because polygraphs only measure end-result changes in the sympathetic nervous system, tricking a polygraph might be achieved by simple relaxation. On the flipside, just being anxious about the test can generate a false positive.
In fact, say the researchers, false positives are common. "About 25 percent of the time, if you're innocent, the polygraph is going to say that you're either guilty or it's indeterminate," says Faro, professor and vice-chairman of radiology at Temple.
In this preliminary study, the researchers wanted to see whether brain scans can even pick up a significant difference between brain activity during lying versus when telling the truth. The researchers had six of eleven volunteers fire a gun, then lie and say they didn't. The other five could truthfully say they didn't fire the gun. All the volunteers were then given functional MRI and polygraph tests during which they denied having fired the gun.
As they reported in The Journal of Radiology, the brain scans revealed unique areas that only lit up during lying. However, the researchers point out that there is never going to be one telltale spot in the brain that automatically indicates a lie. "There really is no one lying center," says Faro. "There are multiple areas in the brain that activate because there's a lot of processes that have to take place."
Instead, Faro and Mohamed say that developing this method into a viable lie-detection system will depend on discovering complex patterns of brain behavior linked to lying. One of the most important of these is that the brain has to work much harder to lie than to tell the truth.
"In the group that lied there were two times the number of areas throughout the brain that showed activation compared to the group that was telling the truth," says Faro. He explains that this is caused by the fact that to lie you have to actively suppress memories that are triggered by the question. That takes more effort than simply asserting the truth.
Mohamed says that one of the most interesting parts of the study was coming up with "an ecologically valid design, as close to true life as possible." The researchers reasoned that lying about a real activity might produce a host of different responses in the brain, rather than just lying about known facts (such as falsely responding to questions like, "What is your name?").
"Because you actually had not just the memory of a gun firing, but you also had the tactile sense of feeling the gun, of hearing the explosion of the bullet, of smelling the gun powder. So we tried to really create a true-life scenario of memory, of reaction, of awareness that would correlate with a true criminal-type event," says Faro.
Faro and Mohamed say a lot more research is needed, but they believe this method could one day be more accurate than a polygraph. Although they're not yet certain whether it will be possible to trick the MRI, they say it's harder to change what your brain is doing than suppress your nervous responses.
"I think it will be very, very hard for somebody to cheat," says Mohamed.
In fact, Faro hopes that this technology will usher in a new era of accuracy in lie detection, which could be applied in areas from preventing insurance fraud to freeing falsely-accused prisoners.
"We have a lot of research that needs to be performed, but I think that in the near future - the next year or two, there will be some very positive results, and I'm very confident that this or a form of this test will be the new gold standard," says Faro.
Because when you're a liar, it's your brain that's on fire.
Faro and Mohamed's research was published in the February 2006 volume of the Journal of Radiology and was internally funded by Temple and Drexel Universities.
Interviewee: Scott Faro, Temple University; Feroze Mohamed, Temple University
Length: 1 min 23 sec
Produced by Eva Gladek
Edited by Eva Gladek/James Eagan
For Further Research in AccessScience:
Brain imaging of deception
Lie detector
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