Human cooperation is so spectacularly different relative to cooperation in other species because humans exhibit unique patterns of altruism such as the altruistic punishment of norm violations that helps sustain cooperation enhancing social norms. Experimental evidence indicates that cooperation flourishes if altruistic punishment is possible, and breaks down if it is ruled out.

Altruistic punishment means that individuals punish unfair and non-cooperative behaviour although the punishment is costly for them and yields no material gain. This raises the big question of why individuals are willing to incur the cost of punishing norm violations.

A Swiss research team under the direction of Ernst Fehr (University of Zurich) studied this question by scanning subjects' brains with Positron Emission Tomography (PET) while subjects decided whether to punish a person who had previously abused their trust by violating a fairness norm. The study shows that a crucial part of the brain’s reward circuit – the caudate nucleus – is activated while subjects are deciding whether to punish. Previous research has shown that the caudate nucleus is also activated if subjects receive money, if they view beautiful faces or consume cocaine, or if individuals in love view pictures of their loved ones.

Feelings of reward associated with the punishment of norm violators may be an evolutionary adaptation that helped maintain group solidarity and cooperation in human societies. As a next step, the members of the Swiss team plan to study the neural basis of important moral emotions like guilt, shame, or gratitude. The scientists believe that their research will contribute to a better understanding of the force behind pro- and antisocial behavior. >from *Scientists from the University of Zurich have discovered the neural basis of altruistic punishment*. August 26, 2004

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> cooperation evolution: symbiotic organisms, social animals and inequity aversion. october 8, 2003
> revenge motivates tribal warfare. february 14, 2003
> human cooperation: biological basis revealed. july 19, 2002
> cooperation and affiliation: primary social behavior in primates. february 25, 2002
> vengeance rocket anniversary: first man-made object out of the earth. october 3, 2001

imago
> the ballad of altruism