Shocking Makes the Brain More Selfish

Oct. 5, 2006 — -- Scientists can temporarily "turn off" part of the brain and make people more selfish, according to new research published in today's issue of the journal Science.

Most brains are wired for "reciprocal fairness" in which, for example, Dick punishes Jane for being unfair, even if that punishment costs Dick a cookie.

Under the reciprocal principle, fair behavior is more important than Dick's cookie.

But Swiss researchers have found a way to switch the reciprocal principle off so that Dick chooses his own cookie over universal fairness.By zapping a certain part of the brain called the dorsolateral prefrontal cortex, or DLPFC, scientists can make Dick act in his own self-interest in situations where he might otherwise ignore his own needs.

Psychologists say reciprocal fairness is at the core of every civilized society.

A civilized society functions on strong social norms, such as fairness, cooperation, politeness, punctuality and honesty. Most people are actually wired to protect these norms and fight against the people who violate them.

People are "programmed" to keep a social society running smoothly by sometimes protecting what is fair instead of what serves them best. Psychologists sometimes use the Ultimatum Game to illustrate this balancing act.

The Ultimatum Game involves two people: a proposer (P) and a responder (R).

P and R have to agree to divide a given amount of money, say $20, according to the following rules: P can make only one suggestion on how that $20 should be divided, and R can say yes or no.

If R says no, both players get nothing. If R says yes, both players get their share of the money.

So here's the reciprocal fairness idea: Psychologists have found in the past that R is likely to say no to an unfair offer -- such as $1 for R and $19 for P -- even though R will get nothing after rejecting the offer.

If R was only after the money, R would say yes to that offer, because $1 is better than nothing.

"The desire for accruing money is a basic human motivation," said Daria Knoch, the author of the study and a human behavior researcher at the University of Zurich in Switzerland.

And that desire has to be suppressed for people to act according to reciprocal fairness.

Knoch and her colleagues have figured out how to zap the brain and suppress reciprocal fairness.

Scientists used a technique called repetitive transcranial magnetic stimulation, which entails passing weak pulses of electrical current through the brain, on a set of volunteers playing the Ultimate Game.

The technique temporarily disrupts the activity of either the right or left dorsolateral prefontal cortex, the brain region that controls R's decision-making during the game, according to previous studies.

By stopping activity in the right side of this region, researchers made volunteers more likely to accept unfair offers instead of rejecting them. So R was more likely to go for P's unfair offer and was less likely to try to punish P for not sharing more equally.

The study's authors concluded that the prefontal brain region is normally involved in overriding selfish impulses.

That conclusion is especially interesting in view of the brain development in young adults, said Knoch.

"In teenagers, the dorsolateral prefontal cortex is not fully developed and has not yet attained its full ability to function in youths and teenagers, which could explain teens' typically impulsive and selfish behavior."

But scientists still can't say for sure exactly what the dorsolateral prefontal cortex, or the DLPFC, does in the brain. While this finding is interesting, it does not mean scientists can zap people around to control all behaviors.

"It is true that the DLPFC is a major component in problem solving, planning and organization," said Ernest Bryant, a clinical neuropsychologist in Corte Madera, Calif.

"That specific region of the brain is not just one single functional unit," said Bryant.

But that one unit seems to play a part in some very social behaviors.