Promises, Expectations, and Social Cooperation

Promising serves as an important commitment mechanism by operating on a potential cheater's internal value system. We present experimental evidence on why people keep their promises, identifying three motives. First, people feel duty bound to keep their promises regardless of whether promisees expect them to do so (promising per se effect). Second, they care about not disappointing promisees' expectations regardless of whether those expectations were induced by the promise (expectations per se effect). Third, they are even more motivated to avoid disappointing promisees' expectations when those expectations were induced by a promise (interaction effect). Clear evidence of some of these effects has eluded the prior literature because of limitations inherent to the experimental methods employed. We sidestep those difficulties by using a novel between-subject vignette design. Our results suggest that promising may contribute to the self-reinforcing creation of trust as expectations of performance encourage promise keeping and vice versa.