While previous research has shownthat there is heightened activity in the prefrontal cortex – the areaof the brain that enables most people to feel remorse or learn moralbehavior – when normal people lie, this is the first study to provideevidence of structural differences in that area among pathologicalliars.
The research – led by Yaling Yang and Adrian Raine, bothof the USC College of Letters, Arts and Sciences – is published in theOctober issue of the British Journal of Psychiatry.
The subjectswere taken from a sample of 108 volunteers pulled from Los Angeles'temporary employment pool. A series of psychological tests andinterviews placed 12 in the category of people who had a history ofrepeated lying (11 men, one woman); 16 who exhibited signs ofantisocial personality disorder but not pathological lying (15 men, onewoman); and 21 who were normal controls (15 men, six women).
"Welooked for things like inconsistencies in their stories aboutoccupation, education, crimes and family background," said Raine, apsychology professor at USC and co-author of the study.
"Pathologicalliars can't always tell truth from falsehood and contradict themselvesin an interview. They are manipulative and they admit they prey onpeople. They are very brazen in terms of their manner, but very coolwhen talking about this."
Aside from having histories of conningothers or using aliases, the habitual liars also admitted tomalingering, or telling falsehoods to obtain sickness benefits, Rainesaid.
After they were categorized, the researchers used MagneticResonance Imaging to explore structural brain differences between thegroups. The liars had significantly more "white matter" and slightlyless "gray matter" than those they were measured against, Raine said.
Specifically,liars had a 25.7 percent increase in prefrontal white matter comparedto the antisocial controls and a 22 percent increase compared to thenormal controls. Liars had a 14.2 percent decrease in prefrontal graymatter compared to normal controls.
More white matter – thewiring in the brain – may provide liars with the tools necessary tomaster the complex art of deceit, Raine said.
"Lying takes a lot of effort," he said.
"It'salmost mind reading. You have to be able to understand the mindset ofthe other person. You also have to suppress your emotions or regulatethem because you don't want to appear nervous. There's quite a lot todo there. You've got to suppress the truth.
"Our argument is thatthe more networking there is in the prefrontal cortex, the more theperson has an upper hand in lying. Their verbal skills are higher.They've almost got a natural advantage."
But in normal people,it's the gray matter – or the brain cells connected by the white matter– that helps keep the impulse to lie in check.
Pathological liarshave a surplus of white matter, the study found, and a deficit of graymatter. That means they have more tools to lie coupled with fewer moralrestraints than normal people, Raine said.
"They've got theequipment to lie, and they don't have the disinhibition that the restof us have in telling the big whoppers," he said.
"When peoplemake moral decisions, they are relying on the prefrontal cortex. Whenpeople ask normal people to make moral decisions, we see activation inthe front of the brain," he explained. "If these liars have a 14percent reduction in gray matter, that means that they are less likelyto care about moral issues or are less likely to be able to processmoral issues. Having more gray matter would keep a check on theseactivities."
The researchers stopped short of asserting that these structural differences account for all lying.
"This is one of the components," Raine said.
"The findings need to be replicated and extended to other parts of the brain. What are the other neurobiological processes?
"Wehaven't had studies like this. It's exciting to us because it's abeginning study, but we need a lot more to flesh out this discovery."
Yang,the study's lead author, said the findings eventually could be used inmaking clinical diagnoses and may have applications in the criminaljustice system and the business world.
"If [the findings] can bereplicated and extended, they may have long-term implications in anumber of areas," said Yang, a doctoral student in the USC departmentof psychology's brain and cognitive science program.
"Forexample, in the legal system they could potentially be used to helppolice work out which suspects are lying. In terms of clinicalpractice, they could help clinicians diagnose who is malingering –making up disability for financial gain. "And also in business, theycould assist in pre-employment screening, working out which individualsmay not be suitable for hiring.
"But, right now, I have to emphasize that there are no direct practical applications," she said.
Intheir journal article, the authors mention that separate studies ofautistic children – who typically have trouble lying – have showed theconverse pattern of gray matter/white matter ratios.
"The factsthat autistic children have difficulty lying and also show reducedprefrontal white matter constitutes the opposite but complementarypattern of the results compared to adults with increased prefrontalwhite matter who find it easy to lie," the researchers wrote.
"Althoughautism is a complex condition and cannot be taken as a model for lying,these results … converge with current findings on adult liars insuggesting that the prefrontal cortex is centrally involved in thecapacity to lie."
The other researchers were SusanBihrle and Lori LaCasse, also of the USC College's psychologydepartment, Patrick Colletti of the Keck School of Medicine of USC'sdepartment of radiology and Todd Lencz of Hillside Hospital'sdepartment of research.
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