We all lie, all the time. It causes problems, to say the least. So why do we do it? It boils down to the shifting sands of the self and trying to look good both to ourselves and others, experts say.

"It's tied in with self-esteem," says University of Massachusetts psychologist Robert Feldman. "We find that as soon as people feel that their self-esteem is threatened, they immediately begin to lie at higher levels."

Not all lies are harmful. In fact, sometimes lying is the best approach for protecting privacy and ourselves and others from malice, some researchers say. Some deception, such as boasting and lies in the name of tact and politeness, can be classified as less than serious. But bald-faced lies (whether they involve leaving out the truth or putting in something false), are harmful, as they corrode trust and intimacy -- the glue of society.

Kidding Yourself

Many animals engage in deception, or deliberately misleading another, but only humans are wired to deceive both themselves and others, researchers say. People are so engaged in managing how others perceive them that they are often unable to separate truth from fiction in their own minds, Feldman's research shows. For instance, In one experiment, Feldman put two strangers in a room together. They were videotaped while they conversed. Later, independently, each was asked to view the tape and identify anything they had said that was not entirely accurate.

Rather than defining what counts as a lie and to avoid the moral tone of the word "lie," Feldman's experimenters simply asked subjects after the fact to identify anything they had said in the video that was "not entirely accurate."

Initially, "Each subject said, 'Oh, I was entirely accurate,'" Feldman told LiveScience. Upon watching themselves on video, subjects were genuinely surprised to discover they had said something inaccurate. The lies ranged from pretending to like someone they actually disliked to falsely claiming to be the star of a rock band.

The study, published in the Journal of Basic and Applied Psychology, found that 60 percent of people had lied at least once during the 10-minute conversation, saying an average of 2.92 inaccurate things.

"People almost lie reflexively," Feldman says. "They don't think about it as part of their normal social discourse." But it is, the research showed.

"We're trying not so much to impress other people but to maintain a view of ourselves that is consistent with the way they would like us to be," Feldman said. We want to be agreeable, to make the social situation smoother or easier, and to avoid insulting others through disagreement or discord.

Men lie no more than women, but they tend to lie to make themselves look better, while women are more likely to lie to make the other person feel better.

Extroverts tend to lie more than introverts, Feldman found in similar research involving a job-interview situation.

Workplace Lies

Other research has delved into prevarication in the workplace.

Self-esteem and threats to our sense of self are also drivers when it comes to lying to co-workers, rather than strangers, says Jennifer Argo of the University of Alberta. A study she co-authored showed that people are even more willing to lie to coworkers than they are to strangers.

"We want to both look good when we are in the company of others (especially people we care about), and we want to protect our self-worth," Argo told LiveScience.