Previous research has suggested that communication and especially promises increase cooperation in laboratory experiments. This has been taken as evidence for internal motivations such as guilt aversion or preference for promise keeping. The goal of this paper was to examine messages under a...

Previous research on gender differences in behavior has led to seemingly contradictory findings about generosity. From data generated by 290 subject pairs, we find that women are more sensitive than men to the costs of generous actions when deciding whether to be generous. The factors that...

Charness and Dufwenberg (2006) find that promises increase cooperation and suggest that the behavior of subjects in their experiment is driven by guilt aversion. By modifying the procedures to include a double blind social distance protocol we test an alternative explanation that promise keeping...