How does the human brain respond to injustice? Wednesday, 11 July 2018
People are very sensitive to injustice. They usually have a very strong emotional response if they become victims of it, but also if they witness someone else becoming a victim. Injustice is a major cause of arguments, from bickering at the dinner table to major conflicts between nations.
Despite people’s sensitivity to it, relatively little is known about how the human brain processes injustice. Dr Mirre Stallen, a former PhD student at RSM and currently assistant professor at Leiden University, and Prof. Ale Smidts of Rotterdam School of Management, Erasmus University (RSM) plus colleagues from Radboud University in Nijmegen researched how the brain responds to social injustice. They discovered that people prefer to punish violators rather than compensate victims. And people who have higher levels of the hormone and neurotransmitter oxytocin (also known as the ‘cuddle hormone’) in their brains punish less severely, but surprisingly, more often.
Stallen and Smidts, and their colleagues Prof. Carsten De Dreu of Leiden University and Prof. Alan Sanfey of Radboud University Nijmegen, wanted to gain a better understanding of the brain processes involved in the perception of injustice and the consequent decision to punish violators or to compensate victims. They conducted an experiment in which they took 55 men, gave 28 of them oxytocin, put them in an MRI scanner in which they could see a monitor and had a controller in their hand, and let them play three variants of a justice game.
In each variant of this game, the participant called ‘the partner’ received 200 gambling chips. Another, ‘the taker’ also got 200 chips. Both participants were told they could exchange the chips for real money after the experiment but were not told for how much.
In the first variant of the game, the partner – whose brain activity was being observed via an MRI scanner – was the victim. The taker could steal a maximum of 100 chips from the partner. The partner could punish the taker by giving up a maximum of 100 chips. For every chip the partner gave up, the taker lost three chips. For example, if the taker took 25 chips from the partner, the partner might consider penalising him 90 chips; that would cost the partner himself 30 chips but would cost the taker 90 chips.
In the second variant, another player took on the role of ‘the observer’ and was scanned in the MRI scanner as he played the game. The observer received 200 chips, then witnessed the taker deciding whether or not to take chips from the partner. If the taker took the partner’s chips, the observer could punish the taker by giving up a maximum of 100 chips. For each chip the partner gave up, the taker lost three chips. Observers did not know if partners had also punished takers.
In the third variant, the observer couldn’t punish the taker, but they could compensate the partner. For each of the 100 potential chips the observer was willing to give up, the partner gained three chips in compensation.
The results of the experiment showed that people will forego money to punish perpetrators or to compensate victims, but they are more prepared to punish a perpetrator than to compensate his or her victim.
People finding themselves victimised are prepared to give up more chips – with real monetary value – than when they observe someone else becoming a victim. The more that is taken from the victim, the more chips people are prepared to give up to punish the perpetrator or to compensate the victim.
Stallen, Smidts and colleagues observed that the MRI scans revealed the decision to punish was related to heightened activity in the ventral striatum region of the brain, the part that is associated with experiencing rewards. The ventral striatum showed more activity when participants decided to punish the perpetrator than when they decided to compensate the victim. Stallen and Smidts concluded: “This finding suggests that punishment may have been preferred over compensation, because punishment was experienced as more rewarding.”
The decision not to punish was related to heightened activity in the temporal parietal junction of the brain. This area is associated with information processing, self-awareness and a sense of perspective.
The 28 of the 50 participants who had been given the hormone oxytocin before taking part in the justice game chose to administer milder punishments more often than other participants who had been given a placebo. This occurred when they became victims themselves and when they observed someone else becoming a victim. Oxytocin had no effect on the decision to compensate victims. So, the commonly held idea that oxytocin generally enhances empathy and pro-social, altruistic decisions was not supported by this study.
Stallen and Smidts suspect that oxytocin makes people more sensitive to violations of the norm. Those who were given the hormone seem to have higher expectations about fairness. As a result, when fairness norms are violated, they are more likely to give violators a ‘slap on the wrist’ for behaving badly. “Our results provide evidence for the hypothesis that oxytocin shifts the focus from self-interest to overarching, normative, group interests.”
Regarding the practical implications of this study for organisations, Stallen and Smidts say: “The most important message for management is probably to understand that people typically respond strongly to violations of fairness, and that they might be eager to punish a norm violator if the context allows.”
Read the paper: Neurobiological Mechanisms of Responding to Injustice, Mirre Stallen, Filippo Rossi, Amber Heijne, Ale Smidts, Carsten K.W. De Dreu and Alan G. Sanfey, Journal of Neuroscience 19 February 2018,1242-17
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