A new brain imaging study shows that when people tell the truth and lie, they use different parts of their brains.  Scientists are exploiting these brain changes to develop an imaging technique as a more accurate replacement for polygraphs or lie detectors. 

Apparently lying requires more work of the brain than telling the truth.

"Deception and truth telling are very complicated.  There are multiple areas in the brain that are involved," says Temple University physician Scott Faro. 

He adds that more brain regions are involved in lying than truth telling, based on studies of people using a technique called functional magnetic resonance imaging. This is a non-invasive method that visually detects increases in blood flow to active parts of the brain. 

"When we look at the differences, there were areas that were unique to the lie condition, and we found that there were actually five areas that were unique," he notes.  "We found in the truth condition, there were two areas that were unique."

Dr. Faro says that when a person answers a question with a lie, not only does the person's brain have to hear and understand the question, but it must also inhibit a truthful response and then deal with the subsequent emotional consequences of lying: guilt, apprehension, fear, and anxiety.

Dr. Faro bases his conclusions on a test of 11 volunteers. Six were asked to fire a toy gun loaded with blank bullets and lie about doing it. The five other non-shooters were asked to tell the truth about the situation. All were connected to standard lie detectors as well as functional magnetic resonance imaging apparatus. In all cases, both techniques distinguished truthful responses from deceptive ones.

Dr. Faro told the annual meeting of the Radiological Society of North America in Chicago Monday that discovering what brain regions were active in the experiment means functional magnetic resonance imaging might someday be used to detect lying in place of the polygraph.

"It has tremendous potential application in a time of increased terrorism, in a time of corporate corruption being at a maximum. I think the use of this test as a possible forensic test would be very helpful," he adds.

The traditional polygraph measures breathing, sweating, heart rate, and blood pressure. But because these physiological responses can vary among individuals and can be controlled in some cases, the polygraph is not considered completely reliable. It is inadmissible as evidence in courts in many U.S. jurisdictions.

Dr. Faro says it is too early to determine if people can fool functional magnetic resonance imaging, too but he says his preliminary results were promising because they suggest a consistency in brain patterns that might be beyond conscious control.

"The polygraph has problems. It has subjectivity to looking at the physiologic data, which is the end of the chain. We need to look at the beginning of the chain and at the central areas of that brain that are causing this behavior. So I think it will be more accurate," he says.

Dr. Faro says functional magnetic resonance imaging must be refined in tests of hundreds more people before becoming a standard for determining deception.