Social Context Games Itai Ashlagi 1 , Piotr Krysta 2 , and Moshe Tennenholtz 34 1 Harvard Business School, Harvard University, USA 2 CS Department, University of Liverpool, UK 3 Industrial Engineering & Management, Technion, Israel 4 Microsoft Israel R&D Center Abstract. We introduce the study of social context games. A social context game is defined by an underlying game in strategic form, and a social context consisting of an undirected graph of neighborhood among players and aggregation functions. The players and strategies in a social context game are as in the underlying game, while the players’ utilities in a social context game are computed from their payoffs in the underlying game based on the graph of neighborhood and the aggregation functions. Examples of social context games are ranking games and coalitional con- gestion games. A significant challenge is the study of how various social contexts affect various properties of the game. In this paper we con- sider resource selection games as the underlying games, and four basic social contexts. An important property of resource selection games is the existence of pure strategy equilibrium. We study the existence of pure strategy Nash equilibrium in the corresponding social context games. We also show that the social context games possessing pure strategy Nash equilibria are not potential games, and therefore are distinguished from congestion games. 1 Introduction Game theory has become a standard tool for the analysis of social interactions of self-motivated agents. 5 Naturally, social interactions may be complex and refer to issues such as competition, coordination, and collaboration among agents. The attitude of agents towards other agents is typically captured by their utility functions. However, it may be of interest to separate the payoff the agent receives, by means of e.g. delay, cost, etc., from his social attitude; this will allow to study the possible effects that various social contexts have. Consider for example several service providers who act on behalf of a set of customers. Each service provider suffers a cost, caused by the need for sharing resources with other service providers. This type of situations are typically modelled as a form of congestion game. Indeed, such congestion games have been a central topic of study in the interplay between computer science and game theory. However, while these games capture the underlying situation, they implicity assume a very particular social context, where the actual goals of each service provider is 5 We use the terms agents and players interchangeably.