Beyond the information given: The power of the belief in self-interest.

How do we interpret other's behavior when we lack important pieces of information? Do we give the other the benefit of the doubt, believing that the other behaves in a fair manner? Or do we "fill in the blanks" with self-interest? To address these questions, we designed a new method-the dice-rolling paradigm-in which participants observed another person assigning outcomes by rolling two dice and allocating one of them to the participant, who only had information about one of the two dice. Using different baselines, the results revealed that participants underestimated the outcomes the other allocated to the participants, and overestimated the outcomes the other allocated to self, indicating that people assume self-interest from others when information is incomplete. © 2009 John Wiley & Sons, Ltd.