Falk, Armin; Fehr, Ernst; Fischbacher, Urs - 2005
theories of fairness and reciprocity capture these forces. We find that cooperators' punishment is almost exclusively targeted … towards the defectors but the latter also impose a considerable amount of spiteful punishment on the cooperators. However …, spiteful punishment vanishes if the punishers can no longer affect the payoff differences between themselves and the punished …