The Prisoner’s Dilemma is a problem studied in game theory that shows how two people might not cooperate even if it's in both their best interests to do so.
Our topic this week is Cooperation and Conflict. Cooperation is found in many species of animals. Take dolphins, wolves, and chimpanzees. They’re all amazingly successful hunters. Why? Because they’re highly cooperative hunters. And there’s no doubt that human beings have taken the art of cooperation to levels that our animal friends can’t begin to match. Take money. Money makes possible the kind of co-operation and coordination required to make a sprawling economic system work. But it’s not just in the domain of the economy that humans cooperate. Politics, education, science---- all of them are domains in shaped by highly complex forms of cooperation. Cooperation is so pervasive among human beings that it doesn’t seem all that far-fetched to think that natural selection has specifically designed human beings to cooperate. At any rate, cooperation clearly has been and will be the key to our survival. Indeed, we need more of it than ever. 21st century humans have to cooperate on a massive scale. Otherwise the earth might burn to a crisp.
Unfortunately, I’m not altogether optimistic that we’re going to pull that level of cooperation off. Humans cooperate, but they also fight. There is as much conflict among humans as cooperation --- or more. We construct complex, cooperative social realities like nations, only to have them engage in insanely destructive wars. We start out promising to love, honor, and obey, only to see many marriages devolve into contested divorces. At a minimum, that shows that it’s way too simple to say that humans are specifically designed for cooperation.
But that’s not really all that’s surprising, though, is it? Sometimes, cooperation is for suckers. To see why that’s so, consider an example adapted from David Hume.
Imagine two farmers -- Duncan and Ethan. Each of them has a field to plow. Each field is too large for one man to plow easily or quickly. Time is running out to get our fields plowed and our crops in. So Ducan makes Ethan an offer. He says to Ethan that he, Duncan, will help him, Ethan, plow Ethan’s field tomorrow, if Ethan will help him, Duncan, plow Duncan’s field today. Would Ethan accept the offer? Should he accept it, if his is rational?
The answer? That depends. In particular, it depends on whether Ethan can be sure that Duncan will follow through and help him once he has already gotten Ethan’s help. If he could be sure of that, it would make perfect sense for Ethan to accept Duncan’s offer.
But can Ethan really be sure that Duncan will follow through? I mean, if I’m Duncan and I'm purely self-interested and not altruistic, then it won’t take long to dawn on me that helping Ethan, once I’ve already got my field plowed, isn’t going to do me any particular good. So why should I follow through? Why would I?
On the other hand, if I am Ethan, and I can see in advance that Duncan is just another self-interested S-O-B, then maybe I won’t accept his offer. Probably I shouldn’t accept his offer. I’d have to be a sucker to do so. But then neither of us will get our fields plowed. And what good as that?
So maybe the right thing to conclude is that Duncan really shouldn’t be such a self-interested S-O-B after all. It’s not in his self-interest to be.
On the other hand, you could make a case that it’s not a matter of selfishness, it’s a matter of rationality. When you’re rational, you do what gives the greatest benefit for the least cost. Once Ethan has helped Duncan plow his field, Duncan should do a cost benefit analysis. Helping Ethan tomorrow is a cost – a pure cost. Duncan already got his field plowed, so there is no additional benefit in plowing Ethan’s field. So if Duncan is rational, he’ll say ``screw Ethan” once tomorrow comes.
Of course, by the same token, if Ethan is rational, and realizes that Duncan is rational, it seems that he won’t help Duncan plow his field today because doing so would be a pure cost to him, with no compensating benefit to be delivered tomorrow.
But now we’re in something of a quandary. Rationality and cooperation are supposed to be hallmarks of being human. How do they fit together? How can they fit together, if cooperation always requires someone to be an irrational sucker? That’s one of our main questions for this week.
Now Hume’s Farmer’s Dilemma IS really a special case of the Prisoner’s Dilemma, which plays an important role in modern social science. We asked our roving philosophical reporter, Caitlin Esch, to explain the prisoner’s dilemma and look at it in real life --- or at least in a reality show. After that we turn to our guest, Cristina Bicchieri, who is a professor of Social Thought and Comparative Ethics at the University of Pennsylvania. She’s also the author of The Grammar of Society: the Nature and Dynamics of Social Norms.