Behavioral Conformity in Games with Many Players

In the literature of psychology and economics it is frequently observed that individuals tend to conform in their behavior to the behavior of similar individuals. A fundamental question is whether the outcome of such behavior can be consistent with self-interest. We propose that this consistency requires the existence of a Nash or approximate Nash equilibrium that induces a partition of the player set into relatively few societies, each consisting of similar individuals playing the same or similar strategies. In this paper we introduce a notion of a society and characterize a family of games admitting the existence of such an equilibrium. We also introduce the concept of 'crowding types' into our description of players and distinguish between the crowding type of a player -- those characteristics of a player that have direct effects on others -- and his tastes, taken to directly affect only that player. With the assumptions of 'within crowding type anonymity' and 'linearity of taste-types' we show that the number of groups can be uniformly bounded.