Hi. In this set of lectures, we're gonna talk about maybe the most famous game in game theory called the prisoner's dilemma. And the prisoner's dilemma is a very simple model of the two by two interaction in which each person has the possibility of being cooperative or defecting. Now the way you write that game is as follows. There's two players, Player one and player two and each has Two options, They can either cooperate, which we represent by C, or they can defect, which we represent by D. Now if they both cooperate, they both get payoffs of four. And if they both defect, they get payoffs of two. So collectively, they're better off if they cooperate. And their worse off if they defect. But what we'll see as we analyze this game, that there's always gonna be incentives for both players to defect, So collectively their better off if they cooperate, individual their better off if they defect, And that creates a tension. Now the prisoner's dilemma is interesting because you can apply it lots of settings. So what we have is a very simple model that gives us insight into a range of different real world phenomena. These include the following. They include arms races. It includes price competition among firms. It includes decisions about whether to adopt a new technology or not. It assumes situations in the political campaigns, whether you go negative, whether you stay positive. By going negative, I mean by attacking your opponent. It includes things like food sharing, do I cooperate by sharing food with someone else or do I just defect by hording it all to myself. And then finally it even includes things like [inaudible] treadmills, where I buy things just to keep up with my neighbor. In all these situations, what we get is that, collectively, we'd be better off if we cooperate. But individually, we have these incentives to deviate. That creates the dilemma. Now, after we study the prisoner's dilemma, we're gonna talk about, how do you overcome it? How do you get cooperation? And we're gonna talk about cooperation inaudibl say times seven. Talking about seven ways in which you can get cooperation in the prisoner's dilemma. Five of these are gonna come from the natural world. They're gonna be ways that different species and even parts of our own bodies learn to cooperate with one another. Two of them are gonna be human induced. They're gonna be ways that we figured out, that human society, Figured out to gain cooperation, to get cooperation in the prisoner's dilemma. After we study the prisoner's dilemma, we're gonna look at something called collective action problems. Now, you're gonna use sort of an extension of the prisoner's dilemma, instead of just involving two people, it's a game that involves a whole bunch of people. In a collective action problem, you gotta say, how much can you contribute to something? And it's like it's be incentive to free ride in that we're gonna see that some of the same tensions we saw in the prisoner's dilemma hold in collective action problems. After we study collective action problems, we're gonna look at something called the common pool resource problems. These are sort of like the inverse of collective action problems in the sense that here there's a resource like trees or water or something like that, maybe even lobster. And you could have said, how many of those do you pull out? Now the more you pull out, the more you're defecting. You're always better off if people pull out fewer lobster or, you know, cut down fewer trees, but individually you can't help yourself from doing it, So common police source problems are Another form of these collective dilemmas that we can see. Now we can think, how do we solve those? Well it turns out, for solving these, there's what we call no panacea. So, this is a picture of Elinor Ostrom, who's a Nobel Prize winner in Economics, even though she's a political scientist, and she spent her life figuring out, how do people around the world solve these collective action problems? And how do they solve these common poor resource problems? We'll talk a lit tle bit about some of the stuff that she's figured out. So that's an outline for what we are going to do. We are going to start out by talking about the prisoner's dilemma. We'll talk about ways in which people have figured out how to get cooperation in the prisoner's dilemma. And then we'll extend that to think about collective action problems, common [inaudible] problems, and we'll talk a little bit about how you can solve those as well. Okay. Thank you.