When Do People Find Cooperation Most Justified? The Effect of Trust and Self–Other Merging in Social Dilemmas

On the basis of goal/expectation theory, it was predicted that just as in interpersonal relationships, cooperation in social dilemma groups would increase only if both trust was high and group members had a common goal of cooperation. Introducing new measures of both these two processes to the social dilemma arena, the goal of mutual cooperation was assessed by the process of self–other merging (the IOS scale), and trust by assessing the extent to which one trusted others and one believed one was perceived as trustworthy by the others. The results showed that when both self–other merging and trust was high, cooperation was indeed highest. Implications for the specific functions of trust and self–other merging in social dilemmas are discussed.