Ambiguity and excuse-driven behavior in charitable giving

A donation may have ambiguous costs or ambiguous benefits. In a laboratory experiment, we show that individuals use this ambiguity strategically as a moral wiggle room to behave less generously without feeling guilty. Such excuse-driven behavior is more pronounced when the costs of a donation -rather than its benefits- are ambiguous. However, the importance of excuse-driven behavior is comparable under ambiguity and under risk. Individuals exploit any type of uncertainty as an excuse not to give, regardless of the nature of this uncertainty.