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Neuroscientists at University College London believe they have found evidence in the brain which helps answer this question -- and may also explain a distinction between the sexes when it comes to the business of punishment. Men, they believe, are likely to take pleasure when they see someone punished for an unfair act... but women are likely to feel badly for the culprit. (Fig: A computer image mapping parts of the brain) In a clever two-phase experiment, the researchers recruited 32 male and female volunteers, as well as four others who were undercover actors hired to play the role of volunteers. In the first part of the experiment, the group played a game of mutual investment in which they had to give money to one of their number. The recipient could decide for himself how much to give back from the profits. He or she could hand back up to triple the investment, but at little reward to himself; or he could hand back little or nothing, thus maximising his own gains but at the investor's cost. One actor was cast in a generous role, always giving lots of money back to his partners, while another actor was cast as a meany, giving back very little and sometimes nothing at all. Body language by the volunteers, confirmed later in questionnaires, confirmed that they did not like the actors who had cheated on them. "Fair" players, in contrast, were rated as more agreeable, more likeable and, remarkably, more attractive. In the second phase, the same volunteers were each placed in a magnetic resonance imaging scanner, a device which shows blood flows within the brain. The volunteer was then given a demonstration of a mild shock -- the equivalent of short bee-sting -- and then watched as the actors, standing next to the scanner, got the same painful treatment. When a "fair" actor received a shock, the scanner showed empathy among all the volunteers. In males and females alike, the images showed activation of the anterior insula/fronto-insular cortex (AI/FI) and anterior cingulate cortex (ACC). Previous research has showed that these parts of the brain cause the feeling of distress when one sees someone else in pain. When an "unfair" actor got a shock, the AI/FI and ACC lit up again among most female volunteers. Amongst the men, however, these empathic areas showed no increase in activity. What was activated in a big way, though, was the nucleus accumbens, the part of the brain associated with the satisfaction of reward. This activation was not seen in most female volunteers. The study appears on Thursday in Nature, the British science weekly. Lead author Tania Singer said the results showed that fairness in social situations "shapes the nature of the emotional link we have to other people. "We empathise with others if they cooperate and act fairly. But in contrast, selfish and unfair behaviour compromises this empathic link," she said. These fundamental responses at individual level have played a key role in social evolution, believed Singer. They would explain for instance why communities everywhere draw up laws or codes to punish or sideline those who cheat and freeload on the majority. As for the gender difference about punishing a social offender, Singer said she could not rule out the possibility that the experiment favoured men as there was a physical rather than psychological or financial threat involved. Despite this limitation, she said, the results could explain the traditional job of men as society's enforcers. "This investigation would seem to indicate there is a predominant role for men in maintaining justice and issuing punishment," she said. Copyright 2006 The original Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.