Vol. 12, No. 1, 2006 Page 7
The brains of people who are pathological liars differ structurally from the brains of normal individuals, according to a magnetic resonance imaging (MRI) study.
Yaling Yang and colleagues obtained their study subjects from a group of 108 volunteers in a temporary employment pool, using a series of psychological tests and interviews to identify 12 people with histories of repeated lying. The researchers compared MRI scans of these individuals to scans of 21 normal controls. Because pathological lying is often associated with antisocial personality disorder, the study included a second control group of 16 people with a history of antisocial personality disorder but no history of pathological lying. The researchers also controlled for age, ethnicity, verbal-performance IQ discrepancy scores, full-scale IQ, psychopathy, or a history of conduct disorder.
Normal individuals show increased bilateral activation in the prefrontal cortex when they tell lies. In this study, the researchers report, "Liars showed a 22 to 26% increase in prefrontal white matter and a 36 to 42% reduction in prefrontal gray/white ratios compared with both antisocial controls and normal controls." Liars exhibited a 14.2% decrease in prefrontal gray matter compared to normal controls.
Study co-author Adrian Raine notes that these differences may increase the ability to lie easily, while impairing brain processes involved in moral restraint. He explains, "Lying takes a lot of effort. It's almost mind reading. You have to be able to understand the mindset of the other person. You also have to suppress your emotions or regulate them because you don't want to appear nervous…. Our argument is that the more networking there is in the prefrontal cortex, the more the person has an upper hand in lying. Their verbal skills are higher. They've almost got a natural advantage." The coexisting deficit in prefrontal gray matter seen in pathological liars, he says, may mean that "they are less likely to care about moral issues or are less likely to be able to process moral issues."
The researchers note that autistic individuals typically are not good at lying, and they say, "intriguingly, brain neurodevelopmental studies of autism show the converse pattern of gray/white ratios to that shown by the liar group." They note, too, that as the brains of normal children develop a greater volume of white matter, the children become more adept at lying. These converging lines of evidence indicate, the researchers say, that "the prefrontal cortex is centrally involved in the capacity to lie."
"Prefrontal white matter in pathological liars," Yaling Yang, Adrian Raine, Todd Lencz, Susan Bihrle, Lori Lacasse and Patrick Colletti, British Journal of Psychiatry, Vol. 187, 2005, 320-5. Address: Yaling Yang, Department of Psychology, University of Southern California, Los Angeles, CA 90089-1061, yalingy@usc.edu.
"Liars' brains wired differently," news release, University of Southern California, August 29, 2005.