Pledges and how social influence shapes their effectiveness

Pledges are used to signal the intention to act in a socially desirable way. In this study, we examine what role social influence plays in the decision to pledge. In a laboratory experiment, subjects can make a pledge to contribute to a public good in the socially optimal way. Across treatment conditions, we vary the way in which the pledges are elicited. Hence, the degree of social influence on pledge-making is manipulated and its impact can be examined. We find that when individuals are aware that the majority of other subjects decided to pledge, they are likely to conform and also make the pledge. The emergence of such a critical mass can be stimulated by (institutional) design, namely by determining the elicitation order on the basis of previous behavior. Overall, this commitment nudge is effective. Both socially-oriented and previously not socially-oriented subjects modify their behavior after the pledge.