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Brain imaging could replace lie detector

When people lie, they use different parts of their brains than when they tell the truth. These brain changes can be measured by brain scanners, researchers have found.

The technique, called functional magnetic resonance imaging (fMRI), may one day prove a more accurate lie-detector test than the standard test, called a polygraph, according to a study presented earlier this month at the annual meeting of the Radiological Society of North America.

fMRI scans create images of brain activity by measuring which parts of the brain are using up the most blood. This is believed to give an approximate representation of which brain areas are working hardest.

“There may be unique areas in the brain involved in deception that can be measured with fMRI,” said the study’s lead author, Scott H. Faro, of Temple University School of Medicine in Philadelphia.

Faro and colleagues conducted a study simulating a lie-and-detection situation for a group of 11 volunteers.

Six of the volunteers were asked to shoot a toy gun with blank bullets and then to lie about their participation. The non-shooters were asked to tell the truth about the situation. The researchers examined the individuals with fMRI, while simultaneously administering a polygraph exam.

The polygraph measures three physiologic responses: respiration, blood pressure and the skin’s ability to conduct electricity, which increases when a person sweats.

The volunteers were asked questions about the situation. In all cases, the polygraph and fMRI accurately distinguished truthful responses from deceptive ones. fMRI showed different patterns of brain activation depending on whether the response was truthful or false. And more brain areas were activated during deception than truth-telling.

The polygraph isn’t considered a totally reliable lie-detection method because the physiologic responses that it measures can vary among individuals, and some people can consciously control them. Faro said it’s too early to tell if fMRI can be “fooled” similarly. But the results are promising because they suggest a consistency in brain patterns that might be beyond conscious control, he added.

“We have just begun to understand the potential of fMRI in studying deceptive behavior,” Faro said. “We plan to investigate the potential of fMRI both as a stand-alone test and as a supplement to the polygraph with the goal of creating the most accurate test for deception.”

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