Deceivers have less grey matter

A study appearing in the British Journal of Psychiatry documents evidence of structural brain abnormalities in people who habitually lie, cheat and manipulate others.

The researchers, from the University of Southern California, built on previous research that showed there is heightened activity in the prefrontal cortex - the area of the brain that enables most people to feel remorse or learn moral behaviour - when normal people lie.

The new study provides evidence of structural differences in that area among pathological liars.

The subjects for the study were taken from a Los Angeles' temporary employment pool. The researchers conducted a series of psychological tests and interviews that categorized the subjects according to their propensity for mistruth.

"We looked for things like inconsistencies in their stories about occupation, education, crimes and family background," said Adrian Raine, co-author of the study. After categorisation, Raine and co-researcher Yaling Yang used Magnetic Resonance Imaging (MRI) to explore structural brain differences between the groups.

What the researchers found was that the liars had significantly more "white matter" - the wiring in the brain - and slightly less "gray matter", than the truthful subjects. The researchers explained that white matter is the "networking" tissue that holds together and links the grey matter.

Apparently, pathological liars have a surplus of white matter and a deficit of gray matter, meaning they have more tools to lie, coupled with fewer moral restraints. When compared to the normal control subjects, liars had a 22 percent increase in white matter and a 14 percent decrease in prefrontal gray matter.