title: Dynamical organization of cooperation in complex topologies.
abstract: In this Letter, we study how cooperation is organized in complex topologies by analyzing the evolutionary (replicator) dynamics of the prisoner's dilemma, a two-player game with two available strategies, defection and cooperation, whose payoff matrix favors defection. We show that, asymptotically, the population is partitioned into three subsets: individuals that always cooperate (pure cooperators), always defect (pure defectors), and those that intermittently change their strategy. In fact, the size of the later set is the biggest for a wide range of the "stimulus to defect" parameter. While in homogeneous random graphs pure cooperators are grouped into several clusters, in heterogeneous scale-free (SF) networks they always form a single cluster containing the most connected individuals (hubs). Our results give further insights into why cooperation in SF networks is enhanced.
authors.affiliation: Institute for Biocomputation and Physics of Complex Systems (BIFI), University of Zaragoza, Zaragoza 50009, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Gómez-Gardeñes
authors.forename: M
authors.initials: M
authors.lastname: Campillo
authors.forename: L M
authors.initials: LM
authors.lastname: Floría
authors.forename: Y
authors.initials: Y
authors.lastname: Moreno
mesh_terms: D000465:Algorithms; D005717:Games, Experimental; D006801:Humans; D007398:Interpersonal Relations; D008606:Mental Processes; D009415:Nerve Net