Research: Truth and deception—the brain tells all


Langleben in front of MRI scanner

Photo by Candace diCarlo

These days it’s becoming more difficult to get away with a lie.

In a study using functional magnetic resonance imaging machines, or MRIs, Penn researchers have found that the brain operates differently in cases of deception and honesty.

In experiments involving 18 volunteers, a team including Assistant Professor of Psychiatry Daniel Langleben and his colleagues Ruben Gur, Anna Rose Childress and Charles O’Brien were able to chart the brain activity involved in lying by using an interrogation method known as the Guilty Knowledge Test. In each situation, volunteers chose an envelope, which contained a five-of-clubs playing card and a cash incentive, and were told not to divulge what card they held.

They were then placed within an MRI scanner and interrogated by a computer. Every time volunteers responded, the MRI took a series of images of the brain, giving researchers the chance to connect each image with a response.

Using mathematical computations, Langleben and his co-

researchers were then able to make group comparisons. What they found, he said, were “relatively sizeable areas (left prefrontal and premotor cortex and the anterior cingulate gyrus) of the brain that were different between lie and truth.”

This discovery may signal the doomsday of polygraphs, today’s lie detector of choice. According to Langleben, polygraphs are “unreliable” because they try to uncover lies by measuring an individual’s anxiety response, which some individuals find easy to suppress.

“What about people that you often want to catch with polygraph? People who are criminal, people who are trained to work with polygraph(s)—they will not be detected,” said Langleben. He said that Robert Hanssen, the FBI counterintelligence specialist who passed the polygraph despite later being found guilty of treason, is a classic example.

Using MRIs also has advantages over other machines.

Langleben said that while other measures chart the pattern and intensity of brain signals, they fail to distinguish between different types of thoughts. For example, although brain signals may appear the same when lying as when thinking about an upcoming vacation, the two thoughts are dramatically different. Because MRIs offer spatial resolution, this problem is eliminated.

But Langleben said the MRI test is not suitable for all situations.

“This is not a police department thing. This is not something where you drag people arrested [from] the street with big blue and black eyes, handcuffed, and interrogate them with this thing,” he said. “This is for high-level, high-end, complicated situations where the accused needs to prove his innocence.”

Langleben is now focusing on how to convert his findings into practical use. Further studies will compare MRIs to polygraphs in real time and use instances of real deception instead of just simulated cases of deception.

“I think there is a high likelihood of this being a tool for training and calibration of other portable machines,” said Langleben. “It will allow us to really understand what we need to look at to detect deception.”

Originally published on April 11, 2002