Studies of abnormal brain function are sure to grow because 'for reasons of security, there is an interest in trying to identify when people are lying,'

Pathological liars have less gray matter and more white matter in their prefrontal cortex, according to a report in the October issue of the British Journal of Psychiatry. Gray matter consists of the cells that do the thinking, while white matter consists of the cells that connect them.

"Our argument is that the more networking there is in the prefrontal cortex, the more the person has an upper hand in lying," said study co-author Adrian Raine, a professor of psychology at the University of Southern California (USC). "Their verbal skills are higher. They almost have a natural advantage."

This is the first report on structural brain abnormalities in pathological liars, the USC researchers said.

More Tools to Lie

The study included 49 Los Angeles residents who were given psychological tests and interviews. The answers allowed the researchers to classify 12 as having a history of repeated lying, 16 who showed signs of antisocial personality disorder but not pathological lying, and 21 as average, usually honest people.

Differences in brain structure were recorded on magnetic resonance images. The liars had 25.7 percent more white matter than the antisocial people and 22 percent more than normal controls. Liars also had a 14.2 percent decrease in gray matter when compared to the controls.

That means that liars have more tools to lie and fewer moral restraints than normal people, Raine said, since this gray matter is also what experts believe controls moral behavior.

"The reduction in gray matter predisposes them to lie in the first place," he said. "The excess of white matter makes it easier for them to do it. If these liars have a 14 percent reduction in gray matter, that means they are less likely to care about moral issues or are less likely to be able to process moral issues."

The finding could eventually be used in making diagnoses of behavioral problems, and might have applications in the criminal justice system, the researchers said.

Psychopathic Behavior

The field in which the USC researchers are working is "rapidly growing," said Diane Fishbein, a research psychobiologist at the Research Triangle Institute in Raleigh-Durham, NC.

Fishbein has done work in "an area of research about deception in general and psychopathology in general," she said. "We are interested in what the substrates are for deception. It would be very interesting to know when someone is lying."

One of her studies found a major difference in the brain function of people who exhibited psychopathic behavior. "Most people process higher-order cognitive function with the front of the brain and emotions in the limbic system, which is lower down," she said. "Psychopaths treat emotional stimuli as if it was information, with their cognitive information processed in the limbic system."

Studies of abnormal brain function are sure to grow because "for reasons of security, there is an interest in trying to identify when people are lying," Fishbein said.

More information: The basics of brain structure and function are described by Serendipity.