Cuesta, José A.Jiménez Recaredo, Raúl JoséSánchez, AngelLugo, Haydeé2010-03-092010-03-092008-03-21Journal of Theoretical Biology, 2008, vol. 251, n. 2, p. 253-2630022-5193https://hdl.handle.net/10016/719911 pages, 5 figures.-- ArXiv pre-print available at: http://arxiv.org/abs/0707.2587Final publisher version available Open Access at: http://gisc.uc3m.es/~cuesta/papers-year.htmlOne of the most direct human mechanisms of promoting cooperation is rewarding it. We study the effect of sharing a reward among cooperators in the most stringent form of social dilemma, namely the prisoner's dilemma (PD). Specifically, for a group of players that collect payoffs by playing a pairwise PD game with their partners, we consider an external entity that distributes a fixed reward equally among all cooperators. Thus, individuals confront a new dilemma: on the one hand, they may be inclined to choose the shared reward despite the possibility of being exploited by defectors; on the other hand, if too many players do that, cooperators will obtain a poor reward and defectors will outperform them. By appropriately tuning the amount to be shared a vast variety of scenarios arises, including the traditional ones in the study of cooperation as well as more complex situations where unexpected behavior can occur. We provide a complete classification of the equilibria of the n-player game as well as of its evolutionary dynamics.application/pdfengRewardSocial dilemmaPrisoner's dilemman-Player gameCooperationEvolutionary dynamicsNash equilibriaresearch articleMatemáticas10.1016/j.jtbi.2007.11.022open access