An underlying norm of reciprocity is by itself a powerful engine for motivating, creating, sustaining, and regulating the cooperative behavior required for self-sustaining social organizations, controlling the damage done by the unscrupulous, and contributing to social system stability. See the discussions in tit for tat and reciprocity (social psychology). The power and ubiquity of the norm of reciprocity can be used against the unwary, however, and is the basis for the success of many malicious confidence games. Minor, usually less malicious examples are techniques used in advertising and other propaganda whereby a small gift of some kind is proffered with the expectation of producing a desire on the part of the recipient to reciprocate in some way, for example by purchasing a product, making a donation, or becoming more receptive to a line of argument.