Conformity versus manipulation in reputation systems

In this paper, we consider a reputation system, where a number of individuals express their opinions, modeled by discrete scalars in the interval [0,1], about an object and the object's score (reputation) is determined as the arithmetic mean of all expressed opinions. An individual's expressed opinion may or may not be consistent with her actual opinion, a continuous scalar in [0,1], for a variety of reasons. In this paper, we address in a unified, game-theoretic framework the influence of two opposing social behaviors, namely conformity and manipulation, on the outcome of a reputation system. For the purposes of this paper, conformity as a social behavior refers to the tendency of an individual to express an opinion that matches the public opinion, whereas manipulation refers to the tendency of an individual to express an opinion so as to manipulate the public opinion toward her actual opinion.