title: Mesoscopic structure conditions the emergence of cooperation on social networks.
abstract: BACKGROUND
  We study the evolutionary Prisoner's Dilemma on two social networks substrates obtained from actual relational data.
  
  
  RESULTS
  We find very different cooperation levels on each of them that cannot be easily understood in terms of global statistical properties of both networks. We claim that the result can be understood at the mesoscopic scale, by studying the community structure of the networks. We explain the dependence of the cooperation level on the temptation parameter in terms of the internal structure of the communities and their interconnections. We then test our results on community-structured, specifically designed artificial networks, finding a good agreement with the observations in both real substrates.
  
  
  CONCLUSIONS
  Our results support the conclusion that studies of evolutionary games on model networks and their interpretation in terms of global properties may not be sufficient to study specific, real social systems. Further, the study allows us to define new quantitative parameters that summarize the mesoscopic structure of any network. In addition, the community perspective may be helpful to interpret the origin and behavior of existing networks as well as to design structures that show resilient cooperative behavior.
authors.affiliation: ETH Zurich, Swiss Federal Institute of Technology, Zurich, Switzerland. slozano@ethz.ch
authors.forename: Sergi
authors.initials: S
authors.lastname: Lozano
authors.forename: Alex
authors.initials: A
authors.lastname: Arenas
authors.forename: Angel
authors.initials: A
authors.lastname: Sánchez
mesh_terms: D005075:Biological Evolution; D003198:Computer Simulation; D003299:Cooperative Behavior; D005716:Game Theory; D006801:Humans; D007398:Interpersonal Relations; D008954:Models, Biological; D012111:Residence Characteristics; D012931:Social Environment; D012944:Social Support