Right brain area linked to fairness.

The ability to control selfish impulses in order to reject an unfair deal depends on a specific right brain area, a new study finds.

A team led by Daria Knoch of the University of Zurich focused on a game in which one person makes an offer to another person on how to split a pot of money. The second person can either accept the offer and pocket the offered portion, or refuse it, leaving both players with nothing. Responders typically reject offers of less than 25 percent of the pot, preferring zilch to an unfair deal.

Knoch's group studied 52 adults who fielded offers in a series of such games, each with a pot of about $16. For 36 of the participants, the researchers used a special device to deliver magnetic pulses to either the right or left side of a frontal-brain region that's thought to mediate fairness decisions. This technique temporarily halts neural activity in a targeted area.

The rest of the volunteers received a sham magnetic treatment.

Almost half of the people with disabled right brain areas accepted offers of 20 percent of the pot, compared with about a tenth of people in the sham group and in the left-brain-disabled group. More than one-third of the right brain-disabled group accepted any unfair offer, whereas no one in the other groups proved so lenient, the researchers report in a study published online Oct. 5 for an upcoming Science.

Only volunteers in the disabled-right brain group spent little time deliberating over unfair offers. They recognized bad deals but found it hard to resist the temptation to make easy money, the researchers propose.