A compulsive liar can be defined as as someone who lies completely out of habit. For a compulsive liar, lying is the normal way of responding to questions coming acting almost as a reflex.  Compulsive liars bend the truth about everything and anything no matter how important the issue actually is. Telling the truth as a compulsive liar feels wrong and awkward. For the most part, compulsive liars are not very manipulative. Lying comes out of habit and is not done in order to harm anyone. Lying is a behavior which provides comfort and an escape from discomfort very similar to drugs or alcohol. Lying can become addictive and hard to stop.  For a compulsive liar, it feels safe and that is why they start to lie even more. Compulsive lying is often a symptom of a much larger personality disorder which is why it is hard to stop this behavior.

In 2005, A USC study found the first proof of structural brain abnormalities in people who lie and cheat out of habit. The study was conducted by Yaling Yang and Adrian Raine. They are both of the USC College of Letters, Arts and Sciences. A sample of on hundred and eight volunteers were taken from from Los Angeles’ temporary employment pool. After many interviews and psychological tests, they were placed into three separate categories. The first category consisted of twelve people who had a history of repeated lying. The next category consisted of 16 who exhibited signs of antisocial personality disorder but not pathological lying.
There was also a third category of twenty one normal controls.After they were categorized, the researchers used Magnetic Resonance Imaging to explore structural brain differences between the groups. “The liars had significantly more “white matter” and slightly less “gray matter” than those they were measured against,” Raine said.

When a human makes a moral decisions, they are using their prefrontal cortex. The liars were observed to have a 25.7 percent increase in prefrontal white matter of their brains compared to the antisocial controls and a 22 percent increase compared to the normal controls. Liars had a 14.2 percent decrease in prefrontal gray matter compared to normal controls. “When people ask normal people to make moral decisions, we see activation in the front of the brain,” Raine explained, “If these liars have a 14 percent reduction in gray 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.” Brain scans of autistic people, who have difficulty telling lies, show the exact opposite profile of Yang’s and Raine’s liars: They have less white matter than other people. In autistic children, white matter doesn’t develop at a normal rate which can possibly explain as to why they have trouble telling lies. The researchers also were able to observe that there are 15 percent fewer or less gray matter in liars versus normal subjects. This study acts as a starting point for understanding the connection between lying and white matter in the brain.

Sources:

http://www.truthaboutdeception.com/lying-and-deception/confronting-a-partner/compulsive-lying/types-of-liars.html

http://seedmagazine.com/content/article/pathological_liars_brains_physically_different/
http://www.npr.org/templates/story/story.php?storyId=87922568
http://www.newscientist.com/article/dn8075-liars-brains-make-fibbing-come-naturally.html#.VEUr_lZH3lI
http://www.truthaboutdeception.com/lying-and-deception/confronting-a-partner/compulsive-lying/types-of-liars.html