Don't think about Wall Street.

Did you think about Wall Street? Of course you did. You can't stop yourself from thinking about something you're told not to think about. But I didn't just conjure images of stocks, suits, and a bronze bull. I primed you to be more selfish. It's science.

If you've ever watched Law and Order, you're well-acquainted with the Prisoner's Dilemma. Many episodes end with the detectives questioning two suspected partners-in-crime in two separate rooms. The cops tell each that the other is about to give them up, and that the first one to talk gets a deal. The other gets a full prison sentence.

This is the dilemma. Each suspect would (1) get off if they both cooperate, (2) get some time if he betrays without getting betrayed, or (3) get more time if he gets betrayed or they both betray. The dilemma, then, is whether to trust their partner to do what's best for both, or to rat their partner out and at least not be a patsy. So, will people work together or not?

Well, it depends on what you call it. At least that's what a 2004 paper by Varda Liberman, Steven Samuels, and Lee Ross found when they tested Stanford undergraduates. These researchers set up a simple Prisoner's Dilemma with money prizes, but added a wrinkle. They told half the students it was called "Community Game" and the other half that it was called "Wall Street Game." And that was all it took to turn these undergrads from team players into Gordon Gekkos. Fully 67 percent of the students cooperated when they were told they were playing "Community Game," but only 33 percent cooperated when they were told they were playing "Wall Street Game."