SCIENCE: Swiss researchers' study ties revenge with satisfaction

WASHINGTON -- Dirty Harry had it right: Brain scans show revenge really might make your day.

Planning revenge sparks enough satisfaction to motivate getting even -- and the amount of satisfaction actually predicts who will go to greater lengths to do so, report Swiss researchers who monitored people's brain activity during an elaborate game of double-cross.

That might not sound too surprising. Just consider the old saying, "Revenge is sweet."

But beyond helping to unravel how the brain makes social and moral decisions, the study illustrates growing interest in the interaction between emotion and cognition -- which in turn influences other fields such as how to better model the economy.

The new study chips "yet another sliver from the rational model of economic man," said Stanford University psychologist Brian Knutson, who reviewed the Swiss research. "Instead of cold, calculated reason, it is passion that may plant the seeds of revenge," he said.

People often are eager to punish wrongdoers even if the revenge brings them no personal gain or actually costs them something. From a practical standpoint, that might seem irrational.

In research reported in today's edition of the journal Science, University of Zurich scientists used PET scans to monitor the brain activity of game players to determine what motivates that type of revenge.

Two players could either trust and cooperate with each other so they both earned money or one could double-cross the other and keep an unfair share. Sometimes the double-cross was deliberate; other times, rules of the game dictated it. The victim could retaliate by fining the double-crosser different amounts, but sometimes had to spend his own money to impose that fine.

All 14 players chose revenge whenever the double-cross was deliberate and the retaliation free. Only three retaliated when the double-cross wasn't deliberate.