Friday, February 09, 2007

Do Men Enjoy Revenge?

Today I happened upon a year old article at the New Scientist website, which describes an experiment investigating gender differences using the prisoner's dilemma. First, Wikipedia on what the prisoner's dilemma is:

Two suspects, A and B, are arrested by the police. The police have insufficient evidence for a conviction, and, having separated both prisoners, visit each of them to offer the same deal: if one testifies for the prosecution against the other and the other remains silent, the betrayer goes free and the silent accomplice receives the full 10-year sentence. If both stay silent, both prisoners are sentenced to only six months in jail for a minor charge. If each betrays the other, each receives a two-year sentence. Each prisoner must make the choice of whether to betray the other or to remain silent. However, neither prisoner knows for sure what choice the other prisoner will make. So this dilemma poses the question: How should the prisoners act?

The dilemma arises when one assumes that both prisoners only care about minimizing their own jail terms. Each prisoner has two options: to cooperate with his accomplice and stay quiet, or to defect from their implied pact and betray his accomplice in return for a lighter sentence. The outcome of each choice depends on the choice of the accomplice, but each prisoner must choose without knowing what his accomplice has chosen to do. Let's assume the protagonist prisoner is working out his best move. If his partner stays quiet, his best move is to betray as he then walks free instead of receiving the minor sentence. If his partner betrays, his best move is still to betray, as by doing it he receives a relatively lesser sentence than staying silent. At the same time, the other prisoner's thinking would also have arrived at the same conclusion and would therefore also betray. If reasoned from the perspective of the optimal outcome for the group (of two prisoners), the correct choice would be for both prisoners to cooperate with each other, as this would reduce the total jail time served by the group to one year total. Any other decision would be worse for the two prisoners considered together. When the prisoners both betray each other, each prisoner achieves a worse outcome than if they had cooperated.

Researchers at UCL scanned players' brains after they had played the game and had them watch other players get a small electric shock. From the new scientist article:
The scans showed that both sexes experienced increased brain activity in the fronto-singular and anterior cingulate cortices – areas that the associated with the direct experience of pain – when watching other players receive a jolt of electricity. Researchers have previously shown that so-called mirror neurons will sometimes fire in empathy with another person's experience.

Both men and women also experienced slightly less activity in these areas when cheaters were given a shock, which suggests the feeling of empathy was dependent on social behaviour.

But tellingly, activity dropped much more in men when watching cheaters being buzzed. In addition, several other regions of male participants' brains "lit up" instead – areas linked to the experience of reward known as the ventral striatum/nucleus accumbens and orbito-frontal cortex.

What does this tell us then? It could represent an innate difference between men and women, whereby men may just have evolved to find revenge pleasurable (perhaps as some kind of encouragement to ensure that punishment is followed through). But it could also be a consequence of learning, where perhaps boys are encouraged to find revenge enjoyable and girls may not receive the same pressure.

Interesting though, and I wonder how this relates to the deviant behaviour of murderers like the Dusseldorf vampire (who got pleasure not from mere revenge, but from horrible and violent crime against innocents).