Abstract
Conditional cooperation of selfish and rational actors is feasible in repeated encounters. We stress an important alternative for conditional cooperation: credible commitments that can be incurred via voluntary hostage posting (in the sense of pledging a bond). Hostages may facilitate cooperation in different ways. First, they reduce incentives to behave uncooperatively. Second, by offering some compensation for losses, hostages reduce the costs of suffering from uncooperative behavior of the partner. Finally, hostages may serve as signals about characteristics of the partner that are related to his opportunities and incentives to behave uncooperatively. We show that signalling hostages may have lasting effects in durable relations.