To secure cooperative opportunities people align their beliefs with the normative expectations of their social environment. These expectations are continuously managed by interactive reasoning, a process that results in dynamical pools of reasons. When people are more concerned about their social standing and reputation than truth, pools of reasons give rise to collective irrationalities. They determine what people should believe if they want to be known as a reliable group member. This account has implications for our understanding of human irrationality (...) and how to deal with it. (shrink)