Understanding Mechanisms of Persistence in Prosocial Behavior: Evidence from a Large-Scale Field Experiment

We test whether asking individuals to donate blood leads to a persistent change in behavior, and examine the underlying mechanism. In a field experiment, we randomize a phone call, asking potential blood donors to turn out, and follow them over up to 18 months. We observe significant behavioral persistence for at least one year. Using naturally occurring adverse weather conditions as a second instrument for donor turnout allows us to distinguish between action-based persistence (or habit formation in Stigler and Becker, 1977) and motivation-based persistence. Our results strongly favor action-based persistence as the underlying mechanism.