Stable Cooperation in the N-Player Prisoner’s Dilemma: The Importance of Community Structure

  • Colm O’Riordan
  • Humphrey Sorensen
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4865)


N-player prisoner dilemma games have been adopted and studied as a representation of many social dilemmas. They capture a larger class of social dilemmas than the traditional two-player prisoner’s dilemma. In N-player games, defection is the individually rational strategy and normally emerges as the dominant strategy in evolutionary simulations of agents playing the game.

In this paper, we discuss the effect of a specific type of spatial constraint on a population of learning agents by placing agents on a graph structure which exhibits a community structure. We show that, by organising agents on a graph with a community structure, cooperation can exist despite the presence of defectors. Furthermore, we show that, by allowing agents learn from agents in neighbouring communities, cooperation can actually spread and become the dominant robust strategy.

Moreover, we show that the spread of cooperation is robust to the introduction of noise into the system.


Cooperation N-Player Prisoner’s dilemma Community structure 


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Copyright information

© Springer-Verlag Berlin Heidelberg 2008

Authors and Affiliations

  • Colm O’Riordan
    • 1
  • Humphrey Sorensen
    • 2
  1. 1.Dept. of Information TechnologyNUIGalwayIreland
  2. 2.Dept. of Computer ScienceUniversity College CorkIreland

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