Effects of controllable facilitators on social media: simulation analysis using Generalized Metanorms Games Fujio TORIUMI Graduate School of Engineering The University of Tokyo Tokyo, Japan Email: tori@sys.t.u-tokyo.ac.jp Hitoshi YAMAMOTO Faculty of Business Administration Rissho University Tokyo, Japan Email: hitoshi.yamamoto@mbm.nifty.com Isamu OKADA Faculty of Business Administration Soka University Tokyo, Japan Email: okada@soka.ac.jp Abstract—Do we have options to encourage users to continue participating in social media? Users can retrieve information in social media without posting articles and/or comments. Thus, information on the media is regarded as a public good, and media managers must be concerned with the free-riding problem. By installing controllable agents, we analyze the evolution of cooperation in an extended version of the Metanorms Game that describes the communication carried out in specific social media and issues both rewards for cooperation and punishments for non- cooperation. From the results of our agent-based simulation, the rewards for cooperation and the rewards for rewards given by others clearly encourage cooperation. Consequently, we clarify that cooperative behaviors are dominant when the benefits of cooperation exceed the costs of rewarding other users. The effects of controllable agents on the evolution of cooperation depend on their types. Whereas the existence of agents who are always coop- erating and rewarding cooperators promotes cooperation, agents who are rewarding cooperators without cooperating discourages cooperation. We believe that understanding such mechanisms will be very beneficial when managers make social media policies and decide how to encourage such media. I. I NTRODUCTION Many types of social media, such as Facebook and Twitter, have become incredibly popular over recent years. In social media, many users voluntarily provide information and create many kinds of values. Since costs are incurred when creating and posting information, non-contributors have incentives to engage in“ free-ride ”behavior. To avoid this problem, many social media provide feedback systems to enhance voluntary participation, such as comments and the Like! button on Facebook. What type of mechanism can social media use to encourage the continuous participation of users, even though they pay certain costs for generating content? What operating policy is effective for social media managers to activate users? Our paper focuses on the effects of controllable facilitators installed by managers. Much information is submitted, and many participants share it in social media. Information in social media resembles a public good because it is available to anyone with the proper permission. One of the schemes proposed to enhance user contributions to such public goods centers on the norms and metanorms games created by Axelrod [1]. In these games, non- cooperators receive punishment from other players. However, it is nearly impossible to punish non-participants in social media. Another scheme rewards contributors; however, it remains debatable whether this approach is effective. For example, some studies ([2], [3]) reported that a punishment system is more effective than a reward system. In this study, we clarify the necessary conditions to moti- vate users to voluntarily provide information in social media and use the framework of a public goods game to describe such user behaviors as posting articles and comments. Finally, we clarify what types of agents must be installed to promote cooperation in a game of a specific social media. This paper, which is an extended version of [4], argues that installing con- trollable agents promotes the cooperative strategies of users. Based on our analysis, managers can decide which approach encourages the use of their social media. II. LITERATURE Some studies on social media have focused on their insti- tutional design. Toriumi [5] used an agent-based approach to examine the methodology for promoting an effective system utilization for activating social network services. The objective of each of these studies was an institutional design for a specific social medium. On the other hand, few studies have analyzed the mechanism of voluntary participation in general social media. Studies on what motivates users to provide information in social media usually adopt a social psychological approach using questionnaire surveys. Miura [6] investigated surveys given to bloggers to clarify the psychological and social processes associated with why they continue their blogs. Self- satisfaction, relationships with others, and skill in handling information significantly and positively affected their intention to continue blogging. Qian [7] found that bloggers who target audiences of friends and family are more likely to post identifying information. These studies imply that the chains of communication, such as reciprocal motivation or utility for maintaining relationships with others, are important for sustaining the motivation to participate. However, since it seems unrealistic to enhance a