The Emergence of Commitments and Cooperation

Agents make commitments towards others in order to in ence others in a certain way, often by dismissing more prof- itable options. Most commitments depend on some incentive that is necessary to ensure that the action is in the agent's interest and thus, may be carried out to avoid eventual penalties. The capacity for using commitment strategies eectively is so important that natural selection may have shaped specialized capacities to make this possible. Evolu- tionary explanations for commitment, particularly its role in the evolution of cooperation, have been actively sought for and discussed in several elds, including Psychology and Philosophy. In this paper, using the tools of evolutionary game theory, we provide a new model showing that indi- viduals tend to engage in commitments, which leads to the emergence of cooperation even without assuming repeated interactions. The model is characterized by two key param- eters: the punishment cost of failing commitment imposed on either side of a commitment, and the cost of managing the commitment deal. Our analytical results and extensive computer simulations show that cooperation can emerge if the punishment cost is large enough compared to the man- agement cost.