John Whitfield in New Scientist:
Around the time of the G20 summit in London on 2 April, the streets of cities across the world were filled with people protesting against the excesses of the banking bosses, among other things. Chances are you agreed with the sentiment. Chances are too that if you had been asked to put your hand in your pocket to fund a campaign to seize their bonuses, even if you wouldn't see any of the money, you'd have been sorely tempted.
If so, congratulations: you have just confounded classical economics, which says that no rational person should ever reduce their own income just to slash someone else's. And yet that's exactly what we do. Classical economics, it turns out, is a pretty terrible predictor of how we actually behave.
But why do we inflict pain for no gain? On the face of it, it is rather a perverse way of going about things. Does spitefulness stem from an affronted sense of fairness? Or something altogether darker: envy, lust for revenge – or perhaps even pure sadism?
It might be all those things. Economists, anthropologists and evolutionary biologists have been teasing out how, used judiciously, spiteful behaviour can be one of our best weapons in maintaining a fair and ordered society. But intentions that are noble in one situation can be malicious in another – making spite a weapon that can all too easily backfire.