The joker effect: Cooperation driven by destructive agents

Alex Arenas, Juan Camacho, José A. Cuesta, Rubén J. Requejo

Research output: Contribution to journalArticleResearchpeer-review

40 Citations (Scopus)


Understanding the emergence of cooperation is a central issue in evolutionary game theory. The hardest setup for the attainment of cooperation in a population of individuals is the Public Goods game in which cooperative agents generate a common good at their own expenses, while defectors "free-ride" this good. Eventually this causes the exhaustion of the good, a situation which is bad for everybody. Previous results have shown that introducing reputation, allowing for volunteer participation, punishing defectors, rewarding cooperators or structuring agents, can enhance cooperation. Here we present a model which shows how the introduction of rare, malicious agents - that we term jokers - performing just destructive actions on the other agents induce bursts of cooperation. The appearance of jokers promotes a rock-paper-scissors dynamics, where jokers outbeat defectors and cooperators outperform jokers, which are subsequently invaded by defectors. Thus, paradoxically, the existence of destructive agents acting indiscriminately promotes cooperation. © 2011 Elsevier Ltd.
Original languageEnglish
Pages (from-to)113-119
JournalJournal of Theoretical Biology
Publication statusPublished - 21 Jun 2011


  • Cooperation
  • Cycles
  • Destructive agents
  • Public goods


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