Equality as a benchmark for third-party punishment and reward: The moderating role of uncertainty in social dilemmas

The present paper focuses on third-parties’ decisions to punish and reward in social dilemmas, and on the moderating role of environmental uncertainty (i.e., uncertainty about the size of the common resource). We argue and demonstrate that in social dilemmas third-parties use the equality rule as a strict benchmark to determine punishments (Study 1) as well as rewards (Study 2), but only under environmental certainty. Under environmental uncertainty, third-parties do not apply such a strict benchmark to distinguish cooperators from defectors. Instead, they appear to use the following rule: the more an individual group member has cooperated the less he/she should be punished (Study 1) and the more he/she should be rewarded (Study 2). As such, these findings are the first to demonstrate that third-party sanctioning decisions are moderated by environmental uncertainty.