Here's the link for the following post. I have only included the last section that seems to explain why "Self-deception is advantageous because it helps us lie to others more convincingly. Concealing the truth from ourselves conceals it from others."
http://www.sciammind.com/print_version.cfm?articleID=0007B7A0-49D6-128A-89D683414B7F0000
Solving the Pinocchio Problem
But why would we filter information? Considered from a biological perspective, this notion presents a problem. The idea that we have an evolved tendency to deprive ourselves of information sounds wildly implausible, self-defeating and biologically disadvantageous. But once again we can find a clue from Mark Twain, who bequeathed to us an amazingly insightful explanation. "When a person cannot deceive himself," he wrote, "the chances are against his being able to deceive other people." Self-deception is advantageous because it helps us lie to others more convincingly. Concealing the truth from ourselves conceals it from others.
In the early 1970s biologist Robert L. Trivers, now at Rutgers University, put scientific flesh on Twain's insight. Trivers made the case that our flair for self-deception might be a solution to an adaptive problem that repeatedly faced ancestral humans when they attempted to deceive one another. Deception can be a risky business. In the tribal, hunter-gatherer bands that were presumably the standard social environment in which our hominid ancestors lived, being caught red-handed in an act of deception could result in social ostracism or banishment from the community, to become hyena bait. Because our ancestors were socially savvy, highly intelligent primates, there came a point when they became aware of these dangers and learned to be self-conscious liars.
This awareness created a brand-new problem. Uncomfortable, jittery liars are bad liars. Like Pinocchio, they give themselves away by involuntary, nonverbal behaviors. A good deal of experimental evidence indicates that humans are remarkably adept at making inferences about one another's mental states on the basis of even minimal exposure to nonverbal information. As Freud once commented, "No mortal can keep a secret. If his lips are silent, he chatters with his fingertips; betrayal oozes out of him at every pore." In an effort to quell our rising anxiety, we may automatically raise the pitch of our voice, blush, break out into the proverbial cold sweat, scratch our nose or make small movements with our feet as though barely squelching an impulse to flee.
Alternatively, we may attempt to rigidly control the tone of our voice and, in an effort to suppress telltale stray movements, raise suspicion by our stiff, wooden bearing. In any case, we sabotage our own efforts to deceive. Nowadays a used-car salesman can hide his shifty eyes behind dark sunglasses, but this cover was not available during the Pleistocene epoch. Some other solution was required.
Natural selection appears to have cracked the Pinocchio problem by endowing us with the ability to lie to ourselves. Fooling ourselves allows us to selfishly manipulate others around us while remaining conveniently innocent of our own shady agendas.
If this is right, self-deception took root in the human mind as a tool for social manipulation. As Trivers noted, biologists propose that the overriding function of self-deception is the more fluid deception of others. Self-deception helps us ensnare other people more effectively. It enables us to lie sincerely, to lie without knowing that we are lying. There is no longer any need to put on an act, to pretend that we are telling the truth. Indeed, a self-deceived person is actually telling the truth to the best of his or her knowledge, and believing one's own story makes it all the more persuasive.
Although Trivers's thesis is difficult to test, it has gained wide currency as the only biologically realistic explanation of self-deception as an adaptive feature of the human mind. The view also fits very well with a good deal of work on the evolutionary roots of social behavior that has been supported empirically.
Of course, self-deception is not always so absolute. We are sometimes aware that we are willing dupes in our own con game, stubbornly refusing to explicitly articulate to ourselves just what we are up to. We know that the stories we tell ourselves do not jibe with our behavior, or they fail to mesh with physical signs such as a thumping heart or sweaty palms that betray our emotional states. For example, the students described earlier, who admitted their lies when watching themselves on videotape, knew they were lying at times, and most likely they did not stop themselves because they were not disturbed by this behavior.
At other times, however, we are happily unaware that we are pulling the wool over our own eyes. A biological perspective helps us understand why the cognitive gears of self-deception engage so smoothly and silently. They cleverly and imperceptibly embroil us in performances that are so skillfully crafted that the act gives every indication of complete sincerity, even to the actors themselves.
