Hugh Pickens writes "People deal with cognitive dissonance — the clashing of conflicting thoughts — by eliminating one of the thoughts. Psychologists have suggested we hone our skills of rationalization in order to impress others, reaffirm our "moral integrity" and protect our "self-concept" and feeling of "global self-worth." Now experimenters at Yale have demonstrated that other primates employ the same psychological mechanism. In one experiment, a monkey was observed to show an equal preference for three colors of M&M's and was given a choice between two of them. If he chose red over blue, his preference changed and he downgraded blue. When he was subsequently given a choice between blue and green, it was no longer an even contest — he was now much more likely to reject the blue. Rationalization is thought to have an evolutionary utility; once a decision has been made, second-guessing may just interfere with more important business. "We tend to think people have an explicit agenda to rewrite history to make themselves look right, but that's an outsider's perspective. This experiment shows that there isn't always much conscious thought going on," said one researcher."