Effects of time on the norm of reciprocity

The norm of reciprocity is a widely accepted social rule that requires us to return favors to those who do something nice for us. We conducted two experiments to test the hypothesis that the obligation to return favors diminishes as the amount of time between the initial favor and the opportunity to reciprocate grows. Participants in the first experiment were given an opportunity to return a favor either 5 min or 1 week after receiving a free soft drink from a confederate. Participants in the 5-min condition agreed to the confederate's request to deliver an envelope across campus more often than control group participants receiving only the request. However, participants in the 1-week condition showed no significant reciprocity effect. Participants in the second experiment indicated in hypothetical scenarios that they would be less likely to return a favor as the length of time since the favor increased. We interpret the findings to mean that the norm of reciprocity does not mandate an open-ended obligati...