A reciprocal action is an action meant to have a similar influence on another's payoff as another's action has on one's own. One hypothesis asserts that reciprocal action is triggered by the reciprocator's belief that another's action was good or ill intended. The other hypothesis says that the...

Bargaining and dilemma games have developed in experimental economics as fairly separate literatures. More than a few analysts are now persuaded that the patterns of behavior in these games are closely related, and considerable effort is being put into a search for models that bridge the gap...

We describe Bayes factor, an explicit measure of the strength of the evidence, the extent to which the data increase or decrease the odds a given hypothesis or model is true. Issues and techniques for deriving a Bayes factor are outlined. We illustrate the technique with data from an ultimatum...