We use more of our brain - and different parts of it - to deceive than we do to tell the truth, a new study has found. And the patterns of brain activity peculiar to lying can be observed using functional magnetic resonance imaging, which may prove to be a more effective method of lie detection than the polygraph.
"We're very excited about these findings," Dr. Scott Faro, director of the Functional Brain Imaging Center and Clinical MRI at Temple University School of Medicine in Philadelphia, and the study's lead author, told globeandmail.com. "We were able to create consistent and robust brain activation related to a real-life deception process."
Dr. Faro and his research team divided 12 volunteers into two groups: A cluster of seven people who were asked to shoot blank bullets from a toy gun and a cluster of five non-shooters.
All 12 subjects were hooked up to a polygraph machine, while simultaneously having their brain activity monitored by fMRI, then they were each put through two phases of questioning.
In the truth-only phase, subjects were told to truthfully answer questions relating to the shooting scenario, as well as general control questions, such as 'Is today Sunday?' In the lie-only phase they were asked to answer all of the questions deceptively. The questioners were kept blind as to whether or not each subject had actually shot the gun.
Pooling all the data related to lying together, and all the data related to truth-telling together, the researches found major differences in the way the brain was activated in each case. More specifically, seven parts of the brain were activated during deception, compared with only four parts during truth-telling.
"Overall, the brain is more active during deception," Dr. Faro said. "This increased activation probably relates to the greater emotional charge, and the higher levels of planning, judgment and inhibition involved in lying," he said.
The polygraph, meanwhile, gauged three physiological responses in the subjects: breathing, blood pressure and perspiration, the last one measured by the skin's increased ability to conduct electricity. While this method was also able to accurately distinguish truths from fibs, more variance was observed in the physiological responses of different individuals who were lying than was seen in the brains of different liars via fMRI.
Moreover, experienced liars can eventually learn to exert control over their physiology and outsmart the polygraph, rendering it a less reliable tool for lie detection.
"We don't know what will eventually turn out to be the gold-standard in lie detection," Dr. Faro said. "We hope to stimulate some major government funding - from the Department of Defence, the CIA and Homeland Security - that will allow us to answer this question.
Although Dr. Faro said it still too early to know if an fMRI can be "fooled" in the same way a polygraph can, he noted the fMRI results showed a consistency in brain patterns that suggest they are beyond conscious control.