But when the researchers actually put another group of people in this situation, more than three-quarters of them took the easy job. Then, under subsequent questioning, they gave themselves high marks for acting fairly. The researchers call this moral hypocrisy because the people were absolving themselves of violating a widely held standard of fairness (even though they themselves hadn’t explicitly endorsed that standard beforehand).

Image Credit... Viktor Koen

A double standard of morality also emerged when other people were arbitrarily divided in two groups and given differently colored wristbands. They watched as one person, either from their group or from the other group, went through the exercise and assigned himself the easy job.

Even though the observers had no personal stake in the outcome  they knew they would not be stuck with the boring job  they were still biased. On average, they judged it to be unfair for someone in the other group to give himself the easy job, but they considered it fair when someone in their own group did the same thing.

“Anyone who is on ‘our team’ is excused for moral transgressions,” said Dr. DeSteno, a psychologist at Northeastern University. “The importance of group cohesion, of any type, simply extends our moral radius for lenience. Basically, it’s a form of one person’s patriot is another’s terrorist.”

If a colored wristband is enough to skew your moral judgment, imagine how you are affected by the “D” or the “R” label on your voting registration. If you are a Democrat, you are more likely to think Mr. McCain hypocritically switched tax policies to pick up conservative votes, but Mr. Obama’s decision to abandon public financing probably looks more complicated. If you’re a Republican you’re likelier to figure Mr. Obama did it just so he could raise more money on his own, but you’re more willing to consider Mr. McCain’s economic rationales.

The more interesting question is how presidential candidates, and their supporters, turn into hypocrites. It has been demonstrated repeatedly in experiments that humans are remarkably sensitive to unfairness. We’ve survived as social animals because we are so good at spotting selfishness and punishing antisocial behavior.