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Liar, liar, brain's on fire
Scripps Howard News Service

January 31, 2006

It takes more parts of the brain to lie than be truthful, according to a new report that suggests brain-imaging studies can do at least as well as polygraphs at detecting fibs.

Researchers from Temple University Hospital in Philadelphia describe their work with functional magnetic resonance imaging in the February issue of the journal Radiology, published Tuesday.




"We have detected areas of the brain activated by deception and truth-telling by using a method that is verifiable against the current gold-standard method of lie detection, the conventional polygraph," said Feroze Mohamed, the study's lead author and an associate professor of radiology at Temple.

"With fMRI, there were consistently unique areas of the brain, and more of them, that were activated during the deceptive process than during truth-telling."

Mohamed noted that the standard polygraph device hasn't produced consistently reliable results because it relies on the outward manifestations of emotions that people feel when lying - increased perspiration, heart rate, blood pressure, changing body positions and facial expressions.

But some people are able to suppress such physical responses when they lie, while others have so much anxiety just from being tested that they seem to be lying even when they're telling the truth, leaving polygraph results' accuracy and consistency in doubt.

A report from the National Research Council concluded that, in criminal cases when people are asked about specific events, polygraphs can tell the difference between lies and truth "at rates well above chance, although well below perfection." But the report, issued in 2002, found that conventional lie-detector tests are too unreliable to weed out spies or terrorists from admission to sensitive areas or jobs.

"Since brain activation is arguably less susceptible to being controlled by an individual, our research will hopefully eliminate the shortcomings of the conventional polygraph test and produce a new method of objective lie detection that can be used in a courtroom or other settings," Mohamed said.

The experiments involved 11 healthy volunteers. During each session, a mock shooting was staged, in which blank cartridges were fired in a testing room. Five of the volunteers were asked to tell the truth when asked about their involvement in the "shooting," and the other six were asked to deliberately lie.

Each volunteer was examined with fMRI while either lying or telling the truth. Each was then asked the same questions again while undergoing a conventional polygraph test.

The imaging studies revealed that 14 areas of the brain were active while the person was being deceptive, but only seven areas lit up when the subject answered truthfully.

Mohamed noted that in producing a deceptive response, a person seeks to inhibit or conceal the truth, which activates parts of the brain that are not required for truth-telling. In particular, the images showed increased activity in the frontal lobe - the part of the brain that handles planning, organizing, problem-solving, personality and emotions - when subjects were lying.

The polygraph tests matched well when the volunteers were asked to lie, accurately detecting the deception 92 percent of the time. But they were only 70 percent accurate when the subjects were asked to tell the truth.


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