The rejection rate in modified ultimatum games in which the offer is generated randomly is about half as large as the rejection rate in standard ultimatum games. This effect has been interpreted as supportive evidence for "intentionality". We propose a different explanation based on the idea that people care about procedural fairness. We test both hypotheses against each other. Procedural fairness predicts that rejection rates systematically depend on the extent to which the random process that determines the offer is skewed while intentionality suggests no effect. Our experiments support the fairness-based explanation.

Co-authors Gary Bolton and Jordi Brandts