Lips can lie, but your brain will spill the beans
New MRI study finds your mind is an open book
Behind a liar's straight face is a brain neuroscientists believe they can read as easily as a signed confession.By Ronald Kotulak
November 30, 2004
Behind the straight face of a liar is a brain busily spinning a falsehood that Temple University neuroscientists believe they can read as easily as a signed confession.
With brain imaging technology, they can see how a lie sparks activity deep in the limbic system, the center of emotion and self-preservation. The lie gathers support from the memory banks in the left and right temporal lobes and then makes a dash to the frontal cortex, where a decision is made to suppress what the brain knows to be true.
Measuring this pattern of activity potentially could result in a much more accurate lie detector than a polygraph machine, according to Dr. Scott H. Faro, director of Temple's Functional Brain Imaging Center--though he cautioned that years of study would be needed to build a brain machine that can tell a lie from the truth.
Preliminary research with functional magnetic resonance imaging, or fMRI, shows that the brain activity that occurs when a lie is being told is dramatically different than the pattern that appears with the truth, Faro reported Monday at the annual meeting of the Radiological Society of North America in Chicago's McCormick Place.
"Lying is a complex behavior," he said. "There is not just one lie center in the brain; multiple areas are interacting. There's more activity and more interactions that occur during a lie than in truth telling."
MRI has been a boon to neuroscientists because it not only provides views of the brain's structures, but it also allows scientists to study how the brain functions when it's healthy and when mental disorders alter its activity. For example, MRI is revealing areas in the brain that are involved in depression and how antidepressive medications correct some of the malfunctioning.
Faro and his colleagues are trying to see what the brain looks like when lying in order to develop devices that can be used in criminal investigations, airport security and other areas.
"The government is interested in deception, and it is looking to get a portable, user-friendly technique to detect it," Faro said. "fMRI imaging has the potential to be more accurate than the polygraph test, or it can be used with the polygraph to improve accuracy."
Dr. Todd Parrish, director of neuroimaging research at Northwestern University Feinberg School of Medicine, said the findings were promising but further studies are needed to validate the results.
"That's getting closer to the real meat of what parts of the brain are involved in lying, the areas involved in emotion, thought and memory," he said.
The polygraph measures changes in breathing, blood pressure and sweating to determine if a person is lying. But these responses can vary among individuals, and some people--such as pathological liars--can fool the machine, which reduces its accuracy rate to about 90 percent. These individuals can control their breathing and heartbeat so they appear normal even when they are lying.
Imaging, on the other hand, measures changes in the brain that are much more difficult to conceal, Faro said. Although a pathological liar may suppress the body's physiological changes, his brain still has to make decisions about lying and these may be observable in MRI images, he said.
The study reported Monday involved 11 normal subjects. All fired blanks from a toy gun; six subjects were told to lie about it and five were told to tell the truth.
Active areas in brain
The researchers found that the brain of the liars showed three active areas in the decision-making frontal lobe, two in the temporal lobes on either side that deal with memory and emotion and two in the limbic system where positive and negative emotions reside.
When people told the truth, their brains were far less active: two regions of activity in the frontal lobe and one each in the temporal lobes and the limbic area.
"When they're lying, they've got to think of the positive and negative consequences," Faro said. "`Did you shoot the gun?' Their first response is of course `I did.' So they have to actively inhibit that response in the thinking centers and they have to inhibit that response in their vocalization centers."
To show a pattern of images of the brain as it lied, the researchers devised a technique of asking a series of questions related to the same subject, such as "Did you shoot the gun? Were you involved in shooting the gun? Were you responsible for shooting the gun?"
"The group of truth-telling individuals had a pattern that differed from the group of lying subjects," Faro said. "We're trying to define the normal brain activation in truth telling and deception."
While the volunteers were having their brain images taken, they were also hooked up to polygraph machines. Both techniques were able to pick out the liars.
But among the five truth tellers, the polygraph results were equivocal for one, indicating they could have been interpreted as the person lying when in fact he was telling the truth, Faro said.
Much more research is needed to determine the accuracy of brain imaging as a lie detector, but the next step will be to expand the study if adequate funding can be obtained, he said.
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