Of course I am not versed in any study of the brain and the mind.
I have no idea except to speculate and observe.
The compulsive liar and the pathological liar are identical.
They mean the same thing. You cannot stop lying out of habbit. You have no idea why you do it. You are in your head so much that you forget that reality may come back to bite you on the ass. You just keep lying.
And making SH_T up. That is pathological and compulsive.
Then there are the LIARS who are just deliberately lying. Those are not any less guilty than the pathological ones, but they can be even more terrifying. BECAUSE they are GOOD at it. NOT an imbecile like TRUMP is.