Pathological liars can't always tell truth from falsehood and contradict themselves in an interview. They are manipulative and they admit they prey on people. They are very brazen in terms of their manner, but very cool when talking about this.
White matter may provide liars with the tools necessary to master the complex art of deceit.
If these liars have a 14 percent reduction in grey matter, that means that they are less likely to care about moral issues or are less likely to be able to process moral issues. Having more gray matter would keep a check on these activities.