So we can see a trend here (Roth 1995; Pillutla and Murnighan 1995: 1424, 2003: 250). Initial hypotheses about participants in ultimatum games relied on relatively simple egoistic motives. Those hypotheses were allegedly disconfirmed by the evidence. New hypotheses were offered which appealed to the role of fairness motives. But then these hypotheses also were allegedly disconfirmed by additional evidence. So even newer hypotheses have now been offered that involve more elaborate egoistic motives. Future work will have to establish whether these proposals turn out to be any more plausible in the long run.