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Fairness 'can evolve through spite'

Fairness origin Fairness may have darker evolutionary roots than expected, a new study suggests.

Rather than evolving from the development of morality, fairness can evolve from the antisocial behaviour of spite, according to findings published today in the journal Proceedings of the Royal Society B.

"A lot of biologists these days think that fairness and the evolution of fairness is tied up with the evolution of morality. Fair behaviour is usually associated with altruism and co-operation," says lead author Associate Professor Patrick Forber, a philosopher of science at Tufts University.

"What we found was something strange. In one setting ... if you introduce spite, and the conditions that favour spite, you actually get fairness."

Forber and philosopher colleague Dr Rory Smead from Northeastern University used the Ultimatum Game, as an evolutionary model to study how fairness can arise in situations where spite thrives.

In this game, Player 1 has some cash and offers either a fair split (around 50 per cent) or an unfair split to Player 2. If the split is rejected, then neither player gets any money. Player 2 either accepts or rejects the ultimatum.

Four strategies have been identified as being used in the Ultimatum Game. Either the player makes only unfair offers but rejects unfair offers (Spiteful); the player makes only fair offers but accepts whatever offers are made (Easy rider); the player makes only fair offers and rejects unfair offers (Fair man); orthe player makes only unfair offers and accepts anything (Games man).

Fairness has been known to evolve in the Ultimatum Game despite the presence of spite and Forber and Smead were interested in exploring how this could happen.

Spite is "the shady relative" of altruism, says Forber.

"Whereas altruism involves paying a cost to confer benefit on another, spite involves paying a cost to inflict cost or harm on someone else."

He and Smead studied the interaction of the four strategies in the game and found spite flourished when players using this strategy interacted mainly with players who used different strategies to them.

Under these conditions all but the 'easy riders' were killed off due to the costs inflicted on them by the spiteful types.

The easy riders coexisted most successfully with the spiteful types because their strategy was the most complementary.

"Part of the reason why they persist is because they can get along with just about anybody and they're going to get some payoff from all their interactions," says Forber.

"Under certain conditions when these spiteful guys are around you see some fair behaviour in the population just as a kind of defence against this antisocial spiteful strategy."

Maximising the interaction between spiteful strategists and people who used different strategies to them can occur in human societies, says Forber.

"It's like the con man strategy. You show up at a new location, you take advantage of people who are different from you and then you move on."

The new findings show fairness does not need co-operation, altruism and morality to evolve, says Forber.

"The idea here is that we are fair not because we are being co-operative and want to be nice to our fellow man," he says. "We're fair because we're worried that our fellow man is a vicious spiteful bastard that might exploit us and this is the best way to defend against it."