Studies back it up: Revenge is sweet

By Michael Stroh: The Baltimore Sun

September 12, 2004

You're crawling down the interstate one morning when a black Porsche blows past on the shoulder. A few moments later, you spot the jerk again--only now he's stuck and shamelessly trying to muscle back into your lane.

Do you let him? Or do you punish the Porsche by driving dangerously close to the car in front of you? It isn't an act that necessarily inspires pride--but, boy, does it feel good.

Now a team of Swiss scientists has figured out why.

Call it the science of schadenfreude. By scanning the brains of research subjects contemplating acts of economic revenge, researchers discovered that it triggered a region of the brain associated with cocaine, money, a lover's face, good food and other potentially pleasant stimuli.

"We have the proverb `Revenge is sweet,"' said Ernst Fehr of the University of Zurich, a co-author of the study, which appeared in the journal Science.

Fehr and others say this is the first neurological evidence to back up the old saw. But the revenge study is just the latest in a broad, continuing effort to unravel the neurological underpinnings of squishy social and moral notions such as fairness and cooperation.

Like Fehr, some researchers pursuing these questions are economists trying to develop more realistic models of spending and other monetary habits.

Others are examining revenge from an evolutionary standpoint. Why, they ask, would humans go out of their way to get even, especially in cases where it might be costly?

Bad behavior

To find out, Fehr and his colleagues recruited male volunteers to play an elaborate laboratory game, with rules designed to encourage double-crossing and revenge.

Playing for Swiss francs, volunteers were paired up and given small stakes. Then one member of the pair was given the option of handing over his money or hoarding it.

If the subject chose to give away his holdings, experimenters quadrupled the amount before awarding it to his partner, who then had to make a decision of his own: Either return half the cash or keep it all.

The game was structured so that participants would earn the most if they trusted their partners and parted with their money.

As a twist, experimenters offered players the option of seeking revenge by fining double-crossers, but they warned that doing so would cost them cash.

While the players deliberated, scientists scanned their brains using positron emission tomography, a technology that detects subtle changes in neural circuitry.

They discovered that the mere act of contemplating revenge caused a region called the dorsal striatum to perk up. Just above the spine, the striatum is linked to feelings of pleasure and anticipated reward.

The scientists even found that striatum activity could presage the possibility of revenge taking: The more active the striatum became, the more money players would usually be willing to spend to get even.

"In the end, what we have shown is that reward circuits in the brain are activated when people can punish the other person," Fehr said. "People don't gain something in economic terms--they get something in psychological terms."

Fehr said the study likely explains why people get a thrill from seeing powerful public figures such as Martha Stewart and former Enron chief Kenneth Lay get their comeuppance when they are suspected of wrongdoing.

Brian Knutson, a Stanford University psychologist who studies the neural basis of emotion, said the Swiss report is the first to make the neurological link between fairness and the striatum.

"Instead of cold, calculated reason, it is passion that may plant the seeds of revenge," he noted in an accompanying commentary.

The study also reveals that revenge seekers are blinded by passion, Fehr points out. As volunteers considered whether to pay up to get payback, researchers noted that the medial prefrontal cortex became active. In previous studies, this area of the brain has been linked to weighing the costs and benefits of taking action.

Wired for fairness?

Sarah Brosnan, an Emory University anthropologist, said an important question is whether a sense of fairness is something people pick up in school, home or church, or whether it's a concept that has been hardwired into the human brain through the eons.

In continuing work with capuchin monkeys, Brosnan and her colleague Frans de Waal of Emory have found compelling evidence of an evolutionary origin. The monkeys, it turns out, know a raw deal when they see one.

In a study published last year, researchers trained the monkeys to barter small pebbles for slices of cucumber. Initially the capuchins, a small tree-dwelling species known for their smarts and discriminating tastes, were satisfied with the trade.

But that quickly changed when researchers placed pairs of capuchins in adjoining cages that enabled them to observe the deal making.

When scientists handed one monkey a plump grape for its pebble but offered the other only a cucumber slice, it balked. When one capuchin was handed a grape without being asked for payment in return, its cagemate became even more incensed--sometimes hurling its pebble or cucumber slice at experimenters.

What made these protests so surprising, Brosnan and de Waal noted, is that the animals rarely refuse food.

In two years of one-on-one bartering, capuchins turned down a trade in less than 5 percent of trials.

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