Free An Introduction to Evolutionary Ethics by Scott M. James Page A

first developed in the 1950s by Merrill Flood and Melvin Dresher of the Rand Corporation. The game itself can be played with money, M&Ms, mating partners, whatever – so long as there is some benefit each participant desires. In the original example, Jack and Jill are arrested (for looting a store, let's say) and placed in separate holding cells. Although Jack and Jill were jointly participating in the looting, Jack and Jill do not know each other. The police make the following offer to Jack:
    If you identify Jill as the perpetrator of the crime and Jill refuses to talk, I will release you right now and, with your eye-witness testimony, charge Jill with the maximum penalty (ten years behind bars). If you refuse to talk and Jill identifies you as the perpetrator, I will charge you with the maximum penalty and I'll release Jill right now. If you identify Jill as the perpetrator and Jill identifies you as the perpetrator, I'll see to it that each of you receives five years behind bars. If both of you refuse to talk, I can only charge each of you with the minimum penalty (two years behind bars). You think about what you want to do while I go down the hall and make the same offer to Jill.
    Figure 2.1 illustrates the various “payoffs” for Jack and Jill.
    Figure 2.1 A Prisoner's Dilemma payoff schedule for Jack and Jill
    If we assume that Jack wants to avoid as much jail time as possible and Jill wants to avoid as much jail time as possible, what should Jack do? Well, let's think about this. If (unbeknownst to Jack) Jill decides to STAY SILENT, then Jack would do better to IDENTIFY JILL, since going free beats two years in jail. If Jill IDENTIFIES JACK, then – again – Jack would do better to IDENTIFY JILL, since five years in jail beats ten years in jail. In other words, whatever Jill decides to do, Jack does better DEFECTING . According to game theorists, DEFECTING is said to “strictly dominate” under these conditions; that is, under all conditions, DEFECTING maximizes an individual's interests. So what makes the Prisoner's Dilemma a dilemma ? This comes into focus when we turn our attention to Jill.
    We're assuming that Jill is just like Jack in that she wants to avoid as much jail time as possible. And, by hypothesis, Jill is offered the same deal as Jack. If Jill goes through the same deliberative processes as Jack, then she, too, will recognize that DEFECTING strictly dominates as a strategy: whatever Jack does, she does better DEFECTING. But if Jill acts on this strategy and Jack acts on this strategy, then both end up worse than if they had both STAYED SILENT. For surely Jack and Jill would each rank two years in jail ahead of five years in jail. The dilemma that the Prisoner's Dilemma so elegantly raises is this: rational calculation recommends DEFECTING, but when everyone calculates in this way, when everyone DEFECTS, everyone does worse than he or she could have done . When everyone goes for the top, everyone ends up near the bottom.
    Putting the point more generally, we can see that from the perspective of any thoughtful individual, defection will always be the most tempting option. By defecting, you at least have the chance of exploiting your neighbors' help; by cooperating, you give up that chance. Moreover, by defecting, you protect yourself from being exploited by others (I mean, who can you trust?). Cooperation, by contrast, almost always comes with the risk of giving without getting in return. And in an unforgiving environment, where resources are scarce and time is limited, giving without getting in return can exact a heavy price. But this way of thinking, when adopted by all, drives everyone down: a group of strictly rational individuals who all appreciate the payoffs of defecting and act accordingly are going to be considerably worse off than a group of individuals who are, by some means, committed to cooperating. In other words, such social environments appear open to invasion by individuals capable