Evolution of Cooperation in SNS-norms Game on Complex Networks and Real Social Networks Yuki Hirahara 1 , Fujio Toriumi 2 , and Toshiharu Sugawara 1 1 Department of Computer Science and Engineering, Waseda University, Tokyo 169-8555, Japan y.hirahara@toki.waseda.jp, sugawara@waseda.jp 2 Department of Systems Innovation, The University of Tokyo, Tokyo 113-8656, Japan tori@sys.t.u-tokyo.ac.jp Abstract. Social networking services (SNSs) such as Facebook and Google+ are indispensable social media for a variety of social communications, but we do not yet fully understand whether these currently popular social media will remain in the future. A number of studies have attempted to understand the mechanisms that keep social media thriving by using a meta-rewards game that is the dual form of a public goods game. However, the meta-rewards game does not take into account the unique characteristics of current SNSs. Hence, in this work we propose an SNS-norms game that is an extension of Axelrod’s metanorms game, similar to meta-rewards games, but that considers the cost of commenting on an article and who is most likely to respond to it. We then experimentally investigated the conditions for a cooperation-dominant situation in which many users continuing to post articles. Our results indicate that relatively large rewards compared to the cost of posting articles and comments are required, but optional responses with lower cost, such as “Like!” buttons, play an important role in cooperation dominance. This phenomenon is of interest because it is quite different from those shown in previous studies using meta-rewards games. Keywords: SNS, Agent-based simulation, Facebook, Metanorms game 1 Introduction Social media are now an almost indispensable infrastructure for a variety of social ac- tivities such as personal information and opinion exchange, advertising, marketing, and political participation/campaigns [9]. Providers of social media merely set up the plat- forms for information exchange on the Internet and the actual content is mostly created and published by individual users. Because users expend personal effort and time in writing articles and comments, incentives or psychological rewards for doing so should be provided for users to keep social media active. These incentives can be achieved, for example, by providing comments on posted articles and responses to these comments; such interactions can provide users with feelings of connection to other people. Thus, the incentives themselves are also provided by SNS users, which means that users incur some cost for giving the incentives. Obviously, there is a trade-off between cost and