April 19, 2002
Volume XXXV, No. 16


In Memoriam

Of Note


Are they lying? Functional MRI holds the answer, scientists say


George Washington couldn't tell a lie, the old story goes. He admitted chopping down the cherry tree.

Oh George, where have you gone? Unlike our trustworthy first president, many who take modern lie detector tests are quite adept at masking their deception, and some have done more than ax a tree. That's why a new study conducted by San Antonio and Hong Kong researchers is so intriguing. It might be the start of a new science that could revolutionize court cases of the future.

Four regions of the brain are more strongly activated when a person is lying than when he is telling the truth, according to images captured at the Health Science Center's Research Imaging Center (RIC). The results are reported in the March issue of Human Brain Mapping.

"This study is the first to directly see how the brain responds to lying," said Dr. Jia-Hong Gao, associate professor at the RIC and director of the U.S. studies. "Previous studies have been behavioral in scope, without the brain scanning component."

The Hong Kong researchers laid groundwork by conducting two behavioral studies involving 133 Chinese university freshmen. Some of the students were asked to adopt a strategy of "malingering," or feigned memory impairment, when answering simple questions about numbers on cards and autobiographical data. The studies revealed patterns of calculated responses, especially among the most astute malingerers.

The San Antonio researchers designed a similar experiment to be conducted as six male subjects underwent functional magnetic resonance imaging (fMRI) at the RIC. In one test, subjects were given a three-digit number and another number 2.5 seconds later, and were asked whether the second number matched the first. In the other exercise, subjects were shown an autobiographic question such as "Where were you born?" and then an answer such as "London." Pressing an air pump connected to a bell in the fMRI console room indicated a yes response.

The subjects were asked to answer questions correctly during a control round as fMRI scans showed the brain's response. Then, before the second round of questions, the subjects were asked to feign a memory problem and deliberately do badly on the test. They were asked to imagine a scenario in which a bad result would lead to an attractive sum of money as compensation. "We asked them to fake skillfully to avoid detection," Dr. Gao said.

Brain scans again were recorded, and results showed the left and right cerebral hemispheres were engaged when memory impairment was feigned. The imaging data revealed four principle areas of brain activation — in the prefrontal and frontal, parietal, temporal and sub-cortical regions. The parietal region is the brain's calculation center.

"An extremely clever aspect of this study is that it is lie detection based on the difference in cognitive strategy between lying and telling the truth, rather than on an unreliable difference in emotional state," commented Dr. Peter T. Fox, director of the RIC and a co-author. "The polygraph — the most widely used method for lie detection — relies on heart rate, blood pressure and skin conductance (sweating) to detect increased anxiety. Polygraph fails in people who aren't anxious about lying. Lying skillfully requires mental calculations which are independent of emotional state; this is what was imaged here."

The researchers concluded that while "astute liars feign successfully in testing once they understand the design of the measure . . . it is also clearly evident that controlling one's cerebral activity to avoid detection is impossible. Taken together, this suggests that our work may have identified some extremely significant preliminary markers that have the promise to enhance the development of valid and sensitive methods for the detection of malingering. . . . Potentially significant applications of our findings for future investigations include research aiming at distinguishing different types of liars and different types of lying."

Dr. Gao said he believes the brain activation seen in simulated lying will strongly, if not perfectly, model the activation in non-simulated lying. "I believe fMRI will come to play a bigger role in lie detection," he said. "Eventually, it could help the FBI and police to establish the truth in many court cases."