As the research on the Ultimatum Game (UG) has clearly demonstrated, the model of homo economicus fails to predict human behavior in a number of situations.. Many interpretations have been put forward in order to explain why players do not simply aim at maximizing their monetary payoff. For instance, models of social preferences (see e.g., Camerer, 2003) try to provide a formal explanation for the apparently irrational behavior of people facing a certain kind of interactive situation. In chapter 1, a more detailed description of these accounts will be given, focusing especially on the specific case of the UG in relation to negative reciprocity (Rabin, 1993) and inequity aversion (Fehr & Schmidt, 1999). From a psychological
viewpoint, negative emotions, such as anger and frustration, elicited by the unfair treatment, are accounted to cause rejections (Pillutla and Murnigham, 1996).
