Perceptions of justice built into the brain

A new study suggests that our brains have a built-in mechanism that causes an automatic reaction when we deal with someone who refuses to share.

The study comes from the Karolinska Institute and Stockholm School of Economics and it will be published in the online open access journal PLoS Biology next week. In the research the subjects’ sense of justice was challenged in a two-player monetary fairness game (monetary fairness, in economics?), and then their brain activity was instantaneously measured using functional magnetic resonance imaging (fMRI).


When bidders in the game made unfair suggestions as to how to share the money, they were regularly punished by their partners even if it cost them. This reaction to unfairness could be reduced by targeting one particular brain region, the amygdala.


The justice study is based on the universal human behavior to react with immediate hostility when another person behaves unfairly and in a way that doesn’t put the best interests of the group first. The social researchers had 35 subjects participate in a money-based fairness game, where on player proposes to another how a fixed sum of cash is to be shared between them; the other player can either accept the suggestion and get the money, or say no, in which case neither player receives any money.


“If the sum to be shared is 100 SEK kronor and the suggestion is 50 each, everyone accepts it as it is seen as fair,” says Dr Katarina Gospic. “But if the suggestion is that you get 20 and I take 80, it’s seen as unfair. In roughly half the cases it ends up with the player receiving the smaller share rejecting the suggestion, even though it costs them 20 SEK.”


Earlier research has put forward the idea that the area controlling the ability to analyze and make financial decisions is located in the prefrontal cortex and insula. But, using fMRI, the researchers saw that the brain area that directs fast financial decisions was really located in the amygdala, an evolutionary old and hence more primitive part of the brain that regulates feelings of anger and fear.


To examine these results further, the test subjects were given the anti-anxiety tranquillizer Oxazepam or a placebo while playing the game. The research team found out that those who had received the drug showed smaller amygdala activity and a stronger tendency to accept an unfair distribution of the money –despite the fact that when asked, they still considered the suggestion unfair.

The control group showed the tendency to act aggressively and reprimand the player who had suggested the unfair distribution of money was directly linked to an increase in activity in the amygdala. A gender difference was also seen, where men responded more aggressively to imbalanced suggestions than women did by showing a consistently higher rate of amygdalic activity. This gender difference was not found in the group that was happily dosed with Oxazepam.

“This is an incredibly interesting result that shows that it isn’t just processes in the prefrontal cortex and insula that determine this kind of decision about financial equitability, as was previously thought,” says Professor Martin Ingvar. “Our findings, however, can also have ethical implications since the use of certain drugs can clearly affect our everyday decision-making processes.”



The concept of monetary fairness is pretty interesting when talking about a sense of justice that is built into the brain. While the results of this study are indeed interesting, there is also reason to believe that the way that it was constructed is flawed.


When dealing with economics it is important to understand that people have a lot of emotional feelings when talking about wealth distribution. Some people take a socialist perspective and some believe in free markets without government intervention.


I believe that fairness in money is open to interpretation from person to person and that this study may want to present their research in a way that eliminates the influence that emotions has on monetary fairness. Plus they doped the subjects up on what I like to call “happy pills”.


But hey what do I know; I’m just a graduate student who just took a class in research methods.


The good news is that the research article is in a journal that has no academic pay wall! So if this is a topic that interests or concerns you, you are free to access this information that was put together by the academic scholars. Open access journals are a step in the right direction. They allow the public more involvement in important fields of study. And these are fields of study that impact us all.