The least effective treatments 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.
The PDF file size is 449k. In all treatments we observe persistent play of a strictly dominated strategy, D . This phenomena, while predicted by the discrete replicator dynamics, can not be explained by it, because the explosive cycles through R, S, P , which make D an above average reply, never occur. D is almost never an above average reply. In other work, we have found the replicator dynamic to be a useful selection dynamic.