Pointless vendettas

We introduce the experimental vendetta game. Two groups of four players each interact over ten identical rounds. In each round each player decides whether or not to reduce the payoff of each member of the other group, at an own cost. Reducing payoffs entails no material benefit for either the player or his group and is motivated by nastiness. Over the rounds, however, players can use reductions to avenge earlier transgressions. Fear of retaliation keeps destruction rates low (13%). The introduction of a symbolic reward, however, trebles the frequency of hostile acts (40%).