Evidence is increasing that revenge in fact brings pleasure. In a study at the University of  Zurich, players who were unfairly treated in a game involving money, trust and cooperation got a measurable kick out of punishing their partners. The study was published in the Aug. 27 issue of Science. In the game, two male participants who did not know each other were each given 10 units of money. 　　Player A could either give his money to Player B, or keep it. If he gave it away, the amount would be quadrupled, so Player B would end up with 50 units (his own units plus the 40 from Player A). Then Player B had to decide whether to share his bounty with Player A. 　　In almost all trials, Player A gave away his money, trusting Player B to share. But often Player B did not share, in which case Player A was given time to decide how to react―by doing nothing or reducing Player B's payoff by anywhere from 2 to 40 units. Using positron emission tomography scans, the researchers saw that as players came to a decision to punish greedy partners, the striatum, a part of the brain involved in processing rewards, was activated.  　　The striatum is activated, for example, when a person is in love and sees a photograph of his beloved, when someone thinks he will soon be paid money or when someone takes cocaine, said Ernst Fehr, an economist and coauthor of the study. 　　Sometimes, Player A had to pay for the privilege of exacting revenge, giving up one unit of money for every two he took from Player B. The more activated Player A's striatum had been when he punished for free, the more he was willing to pay to punish later on. “Our results indicate why revenge is deeply entrenched in many societies,” Fehr said.