What Does It Take to Eliminate the Use of a Strategy Strictly Dominated by a Mixture?

This paper reports an experiment to determine whether subjects will learn to stop using a strictly dominated strategy that can be an above average reply. It is difficult to find an experimental design that eliminates the play of the strictly dominated strategy completely. The least effective treatment used money to motivate behavior directly. The most effective treatment uses a binary-lottery to induce preferences, but even this treatment requires giving subjects plenty of experience. Doing so reduced the play of the strictly dominated strategy to around 10 percent by the end of a session. There is no evidence for the explosive cycling needed to make the strictly dominated strategy an above average reply. The most surprising result was observing cycles in the frequency with which the strictly dominated action was played or spite cycles. Spite cycles appear using both evolutionary and fixed pairs protocols.