Brain scans show that the brains of people who are lying look very different from those of people who are telling the truth, U.S. researchers said on Monday.
The study, using functional magnetic resonance imaging, or fMRI, not only sheds light on what goes on when people lie but may also provide new technology for lie detecting, the researchers said.
There may be unique areas in the brain involved in deception that can be measured with fMRI," said Dr. Scott Faro, director of the Functional Brain Imaging Center at Temple University School of Medicine in Philadelphia.
"There may be unique areas in the brain involved in truth telling," Faro added at a news conference.
Faro and colleagues tested 10 volunteers. Six of them were asked to shoot a toy gun and then lie and say they didn't do it. Three others who watched told the truth about what happened. One volunteer dropped out of the study.
While giving their "testimony," the volunteers were hooked up to a conventional polygraph and also had their brain activity imaged using fMRI, which uses a strong magnet to provide a real-time picture of brain activity.
There were clear differences between the liars and the truth tellers, Faro's team told a meeting in Chicago of the Radiological Society of North America.
"We found a total of seven areas of activation in the deception (group)," he said. "We found four areas of activity in the truth-telling arm."
Overall, it seemed to take more brain effort to tell the lie than to tell the truth, Faro found.
Lying caused activity in the frontal part of the brain --- the medial inferior and pre-central areas, as well as the hippocampus and middle temporal regions and the limbic areas. Some of these are involved in emotional responses, Faro said.
During a truthful response, the fMRI showed activation of parts of the brain's frontal lobe, temporal lobe and cingulate gyrus.
Faro said the study was small and limited. Volunteers were not asked to try especially hard to deceive the equipment, he said -- noting that it has been documented that some people can fool a polygraph using various techniques.
Using fMRI as a lie detector is expensive, but it may be worthwhile in some cases -- such as trying to question a Terrorism suspect, or in a high-profile corporate crime case, Faro said.