Active decisions and pro-social behavior : a field experiment on blood donation

In this paper, we propose a decision framework where people are individually asked to either actively consent or dissent to some pro-social behavior. We hypothesize that confronting individuals with the choice of engaging in a specific pro-social behavior contributes to the formation of issue-specific altruistic preferences while simultaneously involving a commitment. The hypothesis is tested in a large-scale field experiment on blood donation. We find that this ''active-decision'' intervention substantially increases the actual donation behavior of people who have not fully formed preferences beforehand.