Revenge actually is sweet: it stimulates the same types of reward centers in the brain that desserts, desire and drugs do. Ernst Fehr, an economist at the University of Zurich in Switzerland, and his colleagues have shown that the dorsal striatum--the part of the brain that processes rewards--lights up when we punish those who have betrayed our trust.
Fehr's study paired male subjects in a game. Each player began with 10 money units. If A gave his 10 to B, then B received an extra 30 from a bank. If B shared his windfall with A, both players came out ahead. During the experiment, Player A almost always gave up his 10, but Player B often kept the extra money. In those cases, the researchers told A he could punish B by taking two to 40 money units from B's pot. Fehr scanned the brains of the As as they decided whether to exact revenge.
This article was originally published with the title The Pleasure of Revenge.