The norm of reciprocity as an internalized social norm: Returning favors even when no one finds out

We examined whether individuals return favors even when the initial favor giver will never know of their behavior. A confederate gave undergraduate participants in one condition an unexpected bottle of water, whereas other participants received no favor. Later the confederate asked participants to take a survey home with them and return it to a specified place during a specified time 2 or 3 days later. Half the participants believed the confederate herself would be present to receive the survey, and half were told to return the survey to a drop‐off box. Participants who received a favor were more likely to return the survey than those who received no favor. Moreover, this reciprocity effect was found regardless of whether the requester would know of the participant's behavior. The results lend support to an internalized social norm explanation for the reciprocity effect.