Mythomania is a conition involving compulsive lying by a person with no obvious motivation. The affected person might believe their lies to be truth, and may have to create elaborate myths to reconcile them with other facts. A pathological liar is someone who often embellishes his or her stories in a way that he or she believes will impress people. It may be that a pathological liar is different from a normal liar in that a pathological liar believes the lie he or she is telling to be true—at least in public—and is "playing" the role..It could also be that pathological liars know precisely what they are doing. "Pathological liar" is a synonym for symptoms. Even though pathological lying is not recognized as a clinical disorder, legal court cases often require that the plaintiff prove that the defendant is aware that he or she is lying.[dubious – discuss] This proof is most important in cases of slander and/or liability.[clarify] Pathological liars often actually convince themselves that they are telling the truth, which in turn can alter polygraph tests and other questioning. Some[weasel words] have observed that when caught in a lie, pathological liars tend to become hostile or try to disregard the fact they lied; often playing it off as a joke.