Why promises and threats need each other

Despite the pervasive use of promises and threats in social life, very little research has been devoted to examining the effectiveness of these interpersonal tactics in promoting cooperation in social dilemmas. Based on the Goal-Prescribes-Rationality principle, we hypothesized that cooperation should be most strongly enhanced when promises and threats are communicated in combination, rather than in isolation. Also, we hypothesized that the combination of promises and threats should be especially effective among individuals with prosocial rather than proself orientations. Two studies provided good evidence for the latter hypothesis, in that the combination of promises and threats was only effective in people with prosocial orientations, people who are concerned with equality and collective interest. Copyright (c) 2006 John Wiley & Sons, Ltd.