The research shows that being on the receiving end of fair treatment is inherently rewarding, activating the portion of the brain associated with happiness.
Being treated unfairly was shown to activate a region of the brain previously linked to negative emotions, such as moral disgust.
UCLA researchers combined brain imaging with an established psychological test of fairness called the "ultimatum game" to visualize the brain's reaction to fairness.
"The same parts of the brain that get activated in response to very basic rewards get activated in response to fairness," researcher and UCLA psychologist Golnaz Tabibnia, PhD, tells WebMD.
Fairness and the Brain
The game involves two players who have to agree on how to share a specific amount of money, with one player -- the proposer -- deciding on the amount each will get and the other player -- the responder -- determining if the offer is fair and will be accepted.
If the responder finds the offer too unfair to accept, neither player gets anything.
In the UCLA experiment, the game was fixed to present the responder with a range of very fair and unfair offers. The idea was to see how the brain responded to different fairness scenarios.
When the responder received a fair offer of $5 out of $10, the imaging showed the areas of the brain most closely tied to happiness to be highly activated.
When the responders were offered the same amount of money but in a less fair scenario -- $5 out of $23, for example -- the region of the brain closely linked to negative emotion was usually activated, Tabibnia says.
The study appears in the April issue of the journal Psychological Science.
The findings confirm and expand on earlier research showing that fairness is often more important to people than monetary reward.
"When an offer is pretty unfair -- say 20% of the total -- about half the time responders will reject it," Tabibnia says.
The study also shows fairness processing to be "relatively automatic and intuitive," the researchers note.
Not all of the study participants rejected the unfair offers, and when this happened the monetary gain did not usually activate the regions of the brain linked to happiness and reward.
The imaging did show increased activity in the part of the brain associated with emotion control when unfair offers were accepted, which appeared to have tempered the activity of the disgust response, Tabibnia says.
"When people accepted these offers, essentially swallowing their pride, we could see a down regulating of the indignity response in the brain," she says.
'Seeing' the Mind-Brain Connection
The study joins a growing body of research employing functional brain imaging to show the connection between the brain and the mind, says Joy Hirsch, PhD, who directs the Program for Imaging and Cognitive Sciences at New York's Columbia University.
"Science is about seeing, and that is what this lets us do," she says. "We are now able to show not just the structure of the brain, but the structure of the brain in action -- its reaction to emotions like happiness, sadness, and even fairness."
The ability to visualize in real time the brain's response to social interactions should advance the understanding of how the mind works, she says.
"We had never thought of things like ethics or fairness as being tied to neurons, but they are," Hirsch says.
By Salynn Boyles
Reviewed by Louise Chang
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