Does positive feedback of social impact motivate prosocial behavior? A field experiment with blood donors

Positive feedback about the outcome of volunteers’ prosocial actions is often thought to help motivate continued volunteers’ engagement. In the context of blood donations, various collection systems have begun to provide blood donors feedback on successful utilization of their blood donation. An experiment conducted by the main NGO that supports the collection of blood in Italy studies how such feedback affects subsequent blood donations. From a sample of over 8’000 blood donors, we find that providing feedback of successful utilization decreases donations. Though surprising, these results are consistent with theoretical models in which individuals engage in prosocial behavior to sustain a positive self-image: feedback about the outcome of a recent donation can act as reminders that boost self-image and reduce the need for re-engaging soon in prosocial activities. Interestingly for policy, we also show that combining the feedback with an explicit request to sign up for a new donation can eliminate, but not overturn, the negative effect of the feedback.