Brain scan to tell truth from lie

The finding, in Human Brain Mapping and discussed in an article in Nature, advances the science of detecting deception.

Brain imaging offers the possibility of a more exact way to tell whether an individual is telling the truth. The standard today is the polygraph, which measures cardiovascular and sweat gland activity. In many states, polygraph results are not admissible in court.

A more accurate device might change those laws. Dr Daniel Langleben, an assistant professor of psychiatry, found that a functional MRI scan could discriminate between a lie and a truth, and scientists can actually see where the signal is coming from in the brain.

Testing an act of deception is tricky, Langleben said. His first study involved instructing participants to lie. But he realized that wasn’t really lying. He needed to create a test that added secrecy to the mix. “Otherwise it’s more like theater than deception.”

In his latest study, volunteers were given two playing cards and Langleben told them to pick one card and deny having it once inside the scanner. He offered them money to carry out his request. Moments later, in another room, the scientist hooking them up to the scanner told them to tell the truth. Then, the volunteer, independently choosing between two conflicting instructions, answered questions about the two cards while brain activity was recorded.

Other studies using brain mapping have made a strong case for its potential usefulness in criminal investigations, but the brain differences were gathered using group data. The Penn researchers devised a study documenting changes in the brain. This brings the technology that much closer to the courtroom door.

“If it will be of practical significance is still unproven. Considering what to say when lying is a complicated process. There may be other things going on that we just don’t know about,” said Dr Monte Buchsbaum, a professor of psychiatry at Mount Sinai.

The frontal lobe changes are indicative not of lying but a person’s mental activity when thinking about and telling a lie. The frontal lobe is not as metabolically challenged when telling the truth.

Some scanning applications have already excited intelligence agencies, Buchsbaum said. MRI scans have been used to study truth-telling among spies trying to fool investigators into believing that English is their native language. Brain areas activated by speaking one’s native language are different from those seen when speaking a second language.

The Penn scientists said they were accurate in deciding if the volunteers were lying anywhere from 85-90 per cent of the time.

Langleben said it’s still not known if the test results will fall apart when those tested are actively trying to defeat the system. But he said the scanning tests are ready for field testing in criminals. “It might work,” he said. “At this point, it is not for sale.”

LAT-WP