Strategy Choice in the Infinitely Repeated Prisoners’ Dilemma

We use a novel experimental design to identify subjects’ strategies in an infinitely repeated prisoners’ dilemma experiment. We ask subjects to design strategies that will play in their place. We find no clear evidence that eliciting strategies affected subjects’ behavior, supporting the validity of this method. We find the chosen strategies include some well-known ones such as Always Defect, Tit-For-Tat and Grim trigger. However, other strategies that are considered to have desirable properties, such as Win-Stay-Lose-Shift, are not prevalent. A majority of subjects use simple strategies that only condition on the previous period’s outcome. We also find that the strategies used to support cooperation change with the parameters of the game. We use the elicited strategies to test our ability to recover strategies using observed cooperate-defect choices and find that we can do so under certain conditions