Chapter 50 Fairness in Ultimatum Bargaining Although fairness concerns may be relevant they appear to be too simple an explanation for why game theorys strong predictions for ultimatum games are so rarely supported. Self interested offerers want to avoid rejections; unpredicted non equilibrium behavior is more valuable and effective than equilibrium behavior. Previous ultimatum bargaining researchers tended to conclude that unpredicted outcomes resulted from fairness concerns. In a series of studies we operationally defined fairness and tested its effects. The accumulated data from our projects document quite clearly that concerns for fairness provide little explanatory value for offerers and only a small part of the explanation for respondents rejections: the simple cognitive reactions associated with fairness concerns may explain some idiosyncratic rejections; additional emotional reactions make wounded pride and spite a more compelling explanation for unexpected rejections.