Economic games provide models of real-world contexts in which researchers can probe dispositional and structural determinants of intergroup relations. Most intergroup games focus on determinants of aggression between groups and constrain the possibilities for peace. However, paradigms such as the intergroup parochial and universal cooperation game allow for peaceful intergroup relations and can be adapted for the study of peace.

The strategy method is a powerful method for eliciting conditional cooperation instrategic interactions. Theoretically, players’ cooperation conditionalon a specific level of others’ cooperation using the strategy methodshould be equal to their unconditional cooperation given an equivalent beliefabout others’ cooperation. However, using the Prisoner’s Dilemma,we show that decisions using the strategy method are more selfish than decisionsunder a simultaneous decision protocol predicted from players’ beliefs.This is driven entirely by lower cooperation among conditional cooperators withlow expectations about others’ cooperation. We further show that relativeto simultaneous choice, the strategy method shifts salient norms from anegalitarian fairness norm (‘give half’) to a reciprocity norm(‘match others’ behaviour’). This undermines cooperationamong players with low beliefs about others’ cooperation. These resultsthus show that the strategy method does not merely hold beliefs constant, butalso shifts which salient norms influence choice behaviour. This has importantimplications for the use of the strategy method in eliciting socialpreferences.