Newswise — Men appear to get greater satisfaction than women when witnessing retribution, a brain imaging study funded by the Wellcome Trust biomedical research charity has revealed.

This evidence of male schadenfreude, or pleasure at seeing revenge exacted, was highlighted during an experiment, published online by Nature today (Jan 18th), undertaken to compare empathy in the brains of people watching someone they either liked, or disliked, suffering pain.

A series of tests was undertaken involving 32 male and female volunteers plus four 'confederates' who were actually actors, but this was kept secret from the rest of the group.

In the first part of the experiment volunteers played a monetary investment game giving cash to one of the actors who had to then decide how much to give back. During each "transaction" the amount was tripled, so it was beneficial for both volunteer and actor to send as much as possible.

The study was designed to allow one actor to behave fairly, by returning a similar amount, while the other, unfair actor, tended to send back very little, if anything at all.

In the second part of the experiment at the Wellcome Department of Imaging Neuroscience in London, at UCL (University College London)**, the volunteer was placed in a magnetic resonance imaging brain scanner, to allow researchers to measure empathic responses as he or she watched the actors receiving a mild electric shock. When the "fair" players received this stimulation "the equivalent of a short bee sting- both female and male volunteers showed empathy activation in pain related areas of the brain " the fronto-insular and anterior cingulate cortices.

When the unfair actor received a shock the women taking part in the experiment showed empathy with them. However brain images of the male volunteers showed no increased activity in the empathy-related pain areas, but did reveal a surge in the nucleus accumbens, the "reward" region of the brain.

This reward- related activity was not seen in the majority of female participants, who appeared to have empathy for both the fair and unfair actors suffering pain.

Dr Tania Singer, who led the study, said: "During breaks in the tests you could tell from the body language that both the male and female volunteers did not like the actors who had cheated them. They tried to stay away from them as much as possible.

"These emotional responses were later confirmed in questionnaires completed by the volunteers who were asked to judge the actors. They consistently rated the fair player as being more agreeable, more likeable and even more attractive than the unfair actor.

"These results suggest that fairness in social situations shapes the nature of the emotional link we have to other people. We empathize with others if they cooperate and act fairly. But, in contrast, selfish and unfair behaviour compromises this empathic link. So, when the unfair player received a painful shock there was, at most, very little sign of anything registering in the empathy-related region of the men as opposed to the reward-related area where there was activity. They expressed more desire for revenge and seemed to feel satisfaction when unfair people were given what they perceived as deserved physical punishment.

"This type of behaviour has probably been crucial in the evolution of society as the majority of people in a group are motivated to punish those who cheat on the rest. This altruistic behaviour means that people tend to protect each other against being exploited by society's free-loaders, and evolution has probably seeded this sense of justice and moral duty into our brains.

"We will need to confirm these gender differences in larger studies because it is possible the experimental design favoured men as there was a physical rather then psychological or financial threat involved. However this investigation would seem to indicate there is a predominant role for men in maintaining justice and issuing punishment."

Notes to Editors:

* "Empathic Neural Responses are Modulated by the Perceived Fairness of Others." Authors: Tania Singer. Ben Seymour. John P O'Doherty. Klaas E Stephan. Raymond J. Dolan. Chris Frith.

**Wellcome Department of Imaging Neuroscience and UCL Institute of Cognitive Neuroscience, University College London.

The Wellcome Trust is an independent research-funding charity established in 1936 under the will of tropical medicine pioneer Sir Henry Wellcome. The Trust's mission is to promote research with the aim of improving human and animal health and it currently spends more than £400m p.a.

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