Social Dilemmas, International Journal of Psychology
In social dilemma situations, each individual always receives a higher payoff for defecting than for cooperating, but all are better off if all cooperate than if all defect. Often, however, people in social dilemmas attend more to the group's payoffs than to their own, either automatically or to behave "appropriately". But whereas social identity elicits cooperative behaviour in dilemmas, it is generally only for the benefit of an "in-group". Dilemmas between groups (requiring selfsacrificial behaviour within) are often the most extreme. Consequently, the framing and manipulation of group identity is critical to cooperation rate as demonstrated by careful laboratory experimentation.
Robyn M Dawes, David Messick
Dawes, M Robyn, and David Messick. 2000. Social Dilemmas. International Journal of Psychology. 35(2): 111-116.