for National Geographic News
Revenge is sweet. Many of us have felt that way, and now scientists say they know why.
A new brain-imaging study suggests we feel satisfaction when we punish others for bad behavior. In fact, anticipation of this pleasure drives us to crack the whip, according to scientists behind the new research.
The findings, reported in today's issue of the journal Science, may partly explain a behavior known as altruistic punishment: Why do we reprimand people who have abused our trust or broken other social rules, even when we get no direct practical benefits in return?
"A person who has been cheated is [left] in a bad situationwith bad feelings," said study co-author Ernst Fehr, director of the Institute for Empirical Research in Economics at the University of Zurich in Switzerland. "The person would feel even worse if the cheater does not get her or his just punishment."
Human societies are an anomaly in the animal world. Ours are based on a detailed division of labor and cooperation between genetically unrelated individuals in large groups.
Fehr and his colleagues suggest that the feeling of satisfaction people get from meting out altruistic punishment may be the glue that keeps societies together.
"Theory and experimental evidence shows that cooperation among strangers is greatly enhanced by altruistic punishment," Fehr said. "Cooperation among strangers breaks down in experiments if altruistic punishment is ruled out. Cooperation flourishes if punishment of defectors is possible."
Writing in an accompanying Science commentary, Brian Knutson, a psychologist at Stanford University in Palo Alto, California, described as "elegant" the experiment the Swiss team used to show "this complex emotional dynamic of schadenfreude"the pleasure felt over someone else's misfortune.
The scientists measured blood flow in the test subjects' brains using a technology called positron emission tomography (PET). The researchers injected water with a unique signature into the bloodstream of each volunteer, then scanned the person's brain when the water, carried via blood, reached the brain.
"Increased cerebral blood flow in a certain brain region means more oxygen consumption and more brain activity in this region," said study co-author Dominique de Quervain, a neuroscientist at the University of Zurich.
The team scanned the brain activity of male volunteers participating in a game of exchanging money back and forth. If one player made a selfish choice instead of a mutually beneficial one, another player could penalize him.
SOURCES AND RELATED WEB SITES