April 24 (HealthDay News) -- Your brain may be telling you to be nice because it will pay off -- financially or socially, says a new study.

Japanese researchers using functional magnetic resonance imaging (fMRI) on people being enticed with either monetary or reputational rewards for good deeds done found that both flip on the striatum, the brain's reward system, in a similar fashion.

The study, published in the April 24 issue of Neuron, is consistent with a long-held social psychological theory that people do nice things to others to gain a good reputation or social approval just like they work for salary. It may provide a pivotal step toward a neural explanation for people's everyday social behaviors.

The researchers' study on 19 people showed that acquiring a good reputation sent reward-related brain areas, notably the striatum, into overdrive. Many of these areas were also activated when monetary rewards were offered, suggesting that the striatum processes the two in a similar manner.

"Our findings indicate that the social reward of a good reputation in the eyes of others is processed in an anatomically and functionally similar manner to monetary rewards, and these results represent an essential step toward a complete neural understanding of human social behaviors," the researchers wrote.

In a commentary appearing in the same issue of Neuron, authors Rebecca Saxe and Johannes Haushofer said the finding explains why drug treatments for such neurological disorders as Parkinson's disease can trigger abnormal money-related behaviors such as compulsive gambling.

One immediate implication of these results is for patients with dysfunction of these brain regions, Saxe and Haushofer wrote. The striatum is among the targets of some neurological disorders, such as Parkinson's disease. Overtreatment of Parkinson's with dopamine agonists is known to induce abnormal economic decision-making, including compulsive gambling. If the same brain structures are responsible for the reward-value of love and reputation, pharmacological manipulation of the striatum may also have social consequences, they said.

SOURCES: National Institute for Physiological Sciences, news release, April 23, 2008; Cell Press, news release, April 23, 2008