Brain Scans May Beat Polygraphs at Lie Detection
Study found 14 areas of brain lit up when lying; only seven did during truth-telling
TUESDAY, Jan. 31, 2006 (HealthDay News) -- The polygraph test, used for decades to detect when someone is lying, may soon have some stiff competition.
Fueling the debate over whether the polygraph is the most accurate way to uncover deception is a new study in the February issue of Radiology that suggests functional magnetic resonance imaging (fMRI) of the brain might be a better way to separate fact from fiction.
"The polygraph is the traditional gold standard and has been around for some 30 or 40 years now. But even though it's the best we have today, it's not an accurate method of detecting deception, which is a great danger," said study author Feroze B. Mohamed, an associate director with the Functional Brain Imaging Center at Temple University in Philadelphia.
"We think the source of forming deception or truthful answers lies in the brain, and that MR imaging is a better technology, available now, to detect deception," he added.
According to the American Polygraph Association (APA), a polygraph examination typically measures data stemming from a minimum of three physiological systems, including respiratory activity, sweat gland activity and cardiovascular activity.
On its Web site, the organization acknowledges that, "when administered by a competent examiner, the polygraph test is one of the most accurate means available to determine truth and deception."
But the organization adds, "while the polygraph technique is highly accurate, it is not infallible and errors do occur."
The study authors noted that, among clinical efforts to uncover deception, a polygraph is currently the most widely used technique, with an estimated accuracy rate of between 80 percent and 90 percent.
They nevertheless highlighted several drawbacks to the procedure that can stem from the failure to properly conduct a pre-test; misinterpretation of the collected data; and the subjectivity inherent in the questioning itself.
As well, the researchers noted that a polygraph collects data based solely on an individual's outward nervous system response to questioning rather than looking at the inner workings of the brain when engaged in deception.
This means the polygraph gauges bodily reactions, including perspiration, fidgeting and facial expression, which may, in fact, be provoked by emotional states that may have nothing to do with lying -- such as anger, excitement and guilt.
By contrast, fMRI directly measures neuronal activity in the brain by assessing changes that take place across multiple cranial regions while a person proffers either the real deal or a cover-up.
In the hope that fMRI might uncover evidence that is more narrowly linked directly to deception, Mohamed and his colleagues tested the alternate technique on 11 people -- five women and six men.
The participants -- with an average age of almost 29 -- underwent both a polygraph test and a fMRI exam.
Both techniques were administered following participation in a role-play situation in which the participants were divided into two groups, one of which was chosen to fire a gun loaded with blanks inside a testing room located in the study hospital.
The scenario was designed to elicit a natural reaction to a crime event, involving an emotional response (including fear, anxiety and apprehension), as well as stimulating all five senses.
Individuals who fired the gun -- the "guilty" group -- were told to try to fool the test administrator into believing they were not the shooter, after being told they were suspected as being the culprit.
Those who didn't fire the gun -- the "innocent" group -- were told to be honest and cooperative about their innocence, despite being similarly told they were the subject of an investigation.
All gave "yes" or "no" answers to the posed questions, which were asked by the same questioner -- using the same phrasing -- for both the fMRI and polygraph tests.
The polygraph testing was 92 percent accurate in detecting deception among the "guilty" group.
However, polygraph accuracy dropped to between 60 percent and 80 percent in determining the honesty of the "innocent" group.
The fMRI imaging, on the other hand, revealed that twice as many regions of the brain became activated when a person lied than when he told the truth.
In all, 14 areas of the brain activated when deception was in play, including regions responsible for controlling language, sentence structure, social interactions, motor control, memory and emotions.
Only seven brain regions were activated when the person told the truth. Accuracy percentages for fMRI imaging were not reported in the study.
Mohamed and his team concluded that it appears likely that lying always activates the 14 identified areas and that truth-telling never activates those same areas.
Furthermore, they suggested that a person would not be able to mask this activation in the way he or she might be able to fudge the nervous system expression measured by a polygraph.
While finding that fMRI does appear useful in separating truths from lies, they said the jury is still out on whether it could ultimately paint a better portrait of deception that the standard polygraph.
"I think we're probably two to three years away from coming up with a technique where we might be able to put an individual in an MRI scanner and say whether an individual is telling the truth or telling a lie," said Mohamed. "But I think we have the technology. I cannot say with a 100 percent certainty, but I'm cautiously optimistic."
Dr. Daniel D. Langleben, an assistant professor of psychiatry at the University of Pennsylvania's School of Medicine in Philadelphia, is, on the other hand, cautiously pessimistic about the study's findings and methodology.
"This study doesn't really provide any information on the accuracy of the MR imaging," he said. "To do this, one needs to either invent or adapt cutting-edge statistical analysis methods that the authors seem to not be aware of."
"There is a place for a polygraph and MRI comparison," he added, "but this isn't it."
For more on polygraph tests, go to the American Polygraph Association.