Home > News

THURSDAY, Aug. 26 (HealthDayNews) -- Scientists have discovered that the sweetness of revenge may have a neurological basis.

A Swiss brain imaging study shows that punishing people when they behave unfairly activates the same reward circuitry of the brain that is fired up when sniffing cocaine or seeing a beautiful face.

The findings, which appear in the Aug. 27 issue of Science, may partly explain the phenomenon of "altruistic punishment," which is exacting revenge on behalf of a stranger.

"A lot of theoretical work in evolutionary biology and our previous experimental work suggest that altruistic punishment has been crucial for the evolution of cooperation in human societies," said Ernst Fehr, the senior author of the study who is director of the Institute for Empirical Research in Economics at the University of Zurich. "Our previous experiments show that if altruistic punishment is possible, cooperation flourishes. If we rule out altruistic punishment, cooperation breaks down."

Added John Hibbing, a professor of political science at the University of Nebraska in Lincoln: "It [the new study] fits with research that has been done in recent years on the importance of punishment, not just that we cooperate automatically. The notion that a bad guy is going to get it is really important to humans."

According to the study, cooperation among humans is both unique and essential to human societies. The question is, why have people been willing to engage in altruistic punishment even if it can be costly to them personally?

The study is one of the first to use brain imaging to investigate the phenomenon.

As Fehr explained his research, the male participants were each given $10. Person A could either keep his $10 or give it to Person B. If he gave it to B, B would actually receive $40 for a total of $50. Person B could now either reciprocate by giving the money back to A, or giving back just half the amount.

If B acted selfishly by choosing not to reciprocate, then A could decide to punish him. Most players chose to impose punishment, even though it cost them some of their own money.

Using Positron Emission Tomography (PET), the researchers scanned the brain activity of the volunteers while they were making the decision to punish or not.

As it turned out, the decision to punish activated the caudate nucleus, a region of the brain involved in experiencing pleasure or satisfaction, Fehr said. Although the study volunteers were engaging in "regular" revenge, the authors think the findings could be extrapolated to altruistic punishment.

There are a number of implications to the findings.

One is a more constructive way of viewing revenge.

"The twist is a positive sense of punishing someone, as opposed to a negative sense of 'I've been screwed.' That's new," Hibbing said.

"Emotions are not just reactive. They can be proactive," said Brian Knutson, assistant professor of psychology and neuroscience at Stanford University, and author of an accompanying perspective piece in the journal. "They can actually focus and drive behavior. People don't often think about emotions that way."

The very idea that emotions, not cold-calculated reason, are driving revenge is a novel one, Knutson said.

Finally, the anticipation of exacting revenge can be motivating.

Just think about Dirty Harry, the screen cop made famous by Clint Eastwood.

"Go ahead, make my day," Dirty Harry says to a hostage-taker in the 1983 film "Sudden Impact."

"Clint could walk out of there and be fine. He's informing us that he will derive satisfaction from punishing them," Knutson explained.

The guy drops his weapon. Dirty Harry is shipped out of town for playing too fast and too loose. But that's another story.

More information

Learn more about brain structure from Bryn Mawr College.

(SOURCES: Ernst Fehr, Ph.D., director, Institute for Empirical Research in Economics, University of Zurich, Switzerland; Brian Knutson, Ph.D., assistant professor of psychology and neuroscience, Stanford University, Palo Alto, Calif.; John Hibbing, Ph.D., professor of political science, University of Nebraska, Lincoln; Aug. 27, 2004, Science)

Copyright © 2004 ScoutNews, LLC. All rights reserved.