Emergence of Cooperation in Adaptive Social Networks with Behavioral Diversity Sven Van Segbroeck 1,3 , Francisco C. Santos 2,3 , Tom Lenaerts 3 , and Jorge M. Pacheco 4 1 COMO, Vrije Universiteit Brussel, Brussels, Belgium 2 CoDE-IRIDIA, Universit´e Libre de Bruxelles, Brussels, Belgium 3 MLG, Universit´e Libre de Bruxelles, Brussels, Belgium 4 ATP-Group, CFTC & DF, University of Lisbon, Lisbon, Portugal Abstract. Whether by nature or nurture, humans often respond dif- ferently when facing the same situation. Yet, the role of behavioral differences between individuals when immersed in their social network remains largely ignored in most problems of natural and social sciences. Here, we investigate how diversity in the way individuals assess their adverse social partners affects the evolution of cooperation. We resort to evolutionary game theory (EGT) to describe the dynamics of pop- ulations in which individuals interact according to an adaptive social network and may respond differently to unwanted social interactions. We show that increasing the number of ways of responding to adverse ties in the population always promotes cooperation. As such, adaptive social dynamics and behavioral differences benefit the entire community even though myopic individuals still act in their own interest. As de- fectors are wiped out, surviving cooperators maintain the full diversity of behavioral types, providing the means to establish cooperation as a robust evolutionary strategy. Keywords: Evolutionary game theory, cooperation, collective behavior, complex networks. 1 Introduction Cooperative behavior constitutes the hallmark of human society [8]. We tend to help others, even if providing such help is costly. However, often it is advanta- geous to accept all help offered by others without ever giving anything in return, creating the famous paradox of cooperation. The framework of EGT [7] conve- niently formulates the problem by representing interactions between individuals in terms of simple games, like the two-person prisoner’s dilemma [13], where each individual has the choice to either cooperate or defect. Individuals receive a certain payoff upon interaction, whose value depends on their own action and on that of their partner. The payoff they accumulate after interacting with all their contacts measures their fitness and represents their social success. Those that do well will be imitated and their behavior spreads in the population. G. Kampis, I. Karsai, and E. Szathm´ary (Eds.): ECAL 2009, Part I, LNCS 5777, pp. 434–441, 2011. c  Springer-Verlag Berlin Heidelberg 2011