Why do people Lie?

Is there someone out there who has never lied in their entire life? I doubt so, unless of course it happens to a baby. My nephew is 4yrs old, the other day when I went to pick him up from school, with a straight face he denied to the teacher that he knows me. That poor teacher was confused and had to call my mom to verify if I was really his aunt. As we walked out of the classroom, he goes "Hello Athay". I looked at him and didnt know what to say. To him it was just a harmless little joke he was playing on me. He was unaware of the embaressment that he had put me through. Well he is 4 yrs old and wasnt aware of the consequences of his actions.

How about adults who lie? They are aware of consequences of their actions arent they? In Liar Liar, Jim Carey lies to his son about why he needs his son to make a certain wish. Is it right to say a white lie, one that doesnt harm anyone and is only meant good? How about people who lie for their own gains and in that process hurt others? Most of us would forgive a person who tells a lie and later makes a confession, is remorseful and sincerely apologetic. How do we forgive or forget a person who lies through his teeth, disappears, gets self righteous, continues to lie and continues to be pompous?

I guess everyone lies for some reason but the extent to which they lie comes into question now. Why lie when you are aware you are hurting someone? Why continue to lie when your closet is in the open? Why boast about what you did and be self righteous about wht uve done? Do you think that such a person has a high possibility of a psychological disorder?