The rule of reciprocation applies to most relationships; however, in its purest form—an equivalent exchange of gift and favors—it is unnecessary and undesirable in certain long-term relationships such as families or established friendships. In these “communal” relationships, what is exchanged reciprocally is the willingness to provide what the other needs, when it is needed. Under this form of reciprocity, it is not necessary to calculate who has given more or less but only whether both parties are living up to the more general rule.10
