reciprocity (social psychology)

In social psychology, reciprocity is a social rule that says we should repay, in kind, what another person has provided us. That is, people give back the kind of treatment they have received from you. By virtue of the rule of reciprocity, we are obligated to repay favors, gifts, invitations, etc. in the future. If someone remembers us on our birthday with a gift, a reciprocal expectation may influence us to do the same on their birthday. This sense of future obligation associated with reciprocity makes it possible to build continuing relationships and exchanges. Reciprocal actions of this nature are important to social psychology as they can help explain the maintenance of social norms.