Publisher Summary This chapter reviews and compares the significance of research utilizing a Prisoner's Dilemma game with reference to variables intrinsic to the Prisoner's Dilemma paradigm. Uncertainty about the meaning of the responses, the difficulty of assessing the motives behind particular strategies, the barriers against conveying or interpreting preferences or acceptable solutions, the lack of incentive for maximizing gains or perhaps even for taking the task seriously, and the absence of interaction with another human being all tend to make this a situation of possible irrelevance, certain ambiguity, and perhaps even incomprehensibility for the subject. Not only do these variables generally make concepts like reciprocity irrelevant, they tend to draw into question what is actually being studied in the Prisoner's Dilemma game. It appears that research on the Prisoner's Dilemma game may have little transferability to a naturally occurring bargaining situation. This is not because it is too simple or too minimal a situation to be relevant to the complex situations that one might wish to comprehend. Rather, the Prisoner's Dilemma game is not really a simulation of even a very simple bargaining situation. The chapter highlights the historical perspectives of the Prisoner's Dilemma.