LOS ANGELES, April 22 (UPI) -- Receiving a fair offer activates the same brain circuitry as when people eat chocolate, win money or see a pretty face, U.S. researchers said.

Lead author Golnaz Tabibnia, a postdoctoral scholar and Matthew D. Lieberman, an associate professor, both of University of California at Los Angeles, said that humans may be hard-wired to treat fairness as a reward.

Subjects were asked whether they would accept or decline another person's offer to divide money in a particular way. If they declined, neither they nor the person making the offer would receive anything. Some of the offers were fair, such as receiving $5 out of $10 or $12, while others were unfair, such as receiving $5 out of $23.

"In both cases, they were being offered the same amount of money, but in one case it's fair and in the other case it's not," Tabibnia said in a statement.

The study, published in the journal Psychological Science, found almost half the time, people agreed to accept offers of just 20 percent to 30 percent of the total money, but when they accepted these unfair offers, most of the brain's reward circuitry was not activated -- those brain regions were activated only for the fair offers.