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Okay, last module, lecture four.This module's on game theory.Not often talked about in socialepidemiology, but I think it providessome important insights for socialepidemiologists trying to understand howsociety works.And then how these workings of societyproduce health of populations.Again, remember, no reading assignmentfor this week.Instead, what I want you to do is lookfor components of social theory and go tothe discussion boards, and we'll havesome group communication about this.As we're finishing up this week, a cou-,a quick reminder.Why are we doing theory at all?Remember, it tells us where to look, andwhat to focus on, provides a frameworkfor logic and inference, or drawingconclusions, it illuminates, and perhapsmitigates [SOUND] confirmation bias.

That is looking for data, to prove whatyou already know to be true.That's a bad thing in science.And finally, theory is an integral part,of the process of science, there's alwaysdebate whether, data or theory comesfirst, but there's no debate, that theoryis critically important for science.Now we're going to talk about somethingcalled game theory.And it's not about playing Monopoly perse, it's richer than that.And it's the study of strategic or

interactive decision making.And it tries to help us understand whatwe can expect as a social outcome.Given incentives for the individualactors were the rules of the game.It's used in evolutionary biology, ineconomics and other social sciences.And I'd encourage you to do some work onthe Web, Google game theory, maybe checkout Wikipedia.There's lots to go over.And I also want to emphasize, I'm justoffering you a little simplistic tidbit

of this, because that's all I can do inthis course format.I just want to get it going and get someideas in your head.Game theory helps us understand givenprivate or personal motivations.And the incentives, what result thesystem will yield.So that's important distinction.Individuals doing what's good for them

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individually, what happens at the groupor system level?That's why I like game theory, and Ithink it's helpful for socialepidimiology.And then critically we can image if wealtered the rules of the game or theincentives what might we expect thesystem to produce very concretely giventhe rules of the game what kind of healthdo we imagine for the population.If we alter the incentives for the game.What might the difference be in thehealth of the population?So that's what we're really after here.Lets start with a simplistic classic one.I'm just going to walk you through thesequickly, and it's just to illuminate someof these.Core aspects of game theory.The first is called the Prisoner'sDilemma, and the story is this: There'stwo criminals that get jailed.Their jailed and put in separate cells,

their not allowed to communicate at all.Their sort of by themselves and thesheriff, or the jailer comes to each ofthem independently and says If you tellme your partner was the actual criminal,you'll get to go free.He'll spend more time in jail.The critical piece here is that thesheriff or jailer says this to each ofthe criminals independently and theydon't know it.They cannot communicate with each other.So the dilemma, so called prisoners

dilemma, is what do the prisoners do, andthen what's the social or group outcome?This can all be translated into somesimple and complex math.We're going to keep it simple.So first, just imagine this scenario.We have one prisoner and he can either besilent, that is not speak about hisaccomplice, being the reason or theactual criminal.Or he can betray, or sometimes call itrat out, his accomplice.So prisoner one has a choice.

Be silent and not speak.Or betray or rat out his accomplice.If the prisoner is silent, doesn't ratout his accomplice, he might spend sometime in jail.Because the jailer says, well, you didn'tgive up your friend, you spend time injail and he might spend a year in jail.The numbers themselves don't matter, it'sthe differences in numbers.

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If he betrays, and says, oh yeah, theother guy did it.Then he gets to go free.Now the fun part, prisoner two gets thesame deal.If he's silent, he spends some time injail.If he rats out or betrays his friend.He gets to go free.Now remember, there two prisoners cannotcommunicate.How much trust do they have in oneanother?Because the scenario becomes this,prisoner one is silent, spends a year injail.Prisoner one betrays, spends no time injail, prisoner two, silent.One year in jail, betrays no time injail.But now, let's get more complicated.If prisoners one is silent, and prisonerstwo is silent.They both spend just one year in jail,

not optimal.So, if prisoner one betrays, rats out hiscolleague, and prisoner two remainssilent, prisoner one walks, and prisonertwo spends, say five years in jail.That's a bummer, prisoner one wins,prisoner two loses.On the other hand, if prisoner twobetrays and prisoner one remains silent,then prisoner two walks and prisoner onespends time in jail, so now it getsinteresting.We have this scenario, where both have

incentive to betray each other and walkfree.If they're both silent, they spend oneyear in jail which is more than walkingfree, but not as bad as if the other onebetrays.So what happens here is this lowerdiagonal box is where the system willyield.Both prisoners end up betraying eachother, because they're afraid the otherone will betray them.And so both spend three years in jail.

That's the expected outcome of thisprison's dilemma setup.And it's all a function of the rules ofthe game or the incentives for eachplayer and the fact that they cannotcommunicate.So what's the point?That the rules of the game or individualrationality people trying to maximizetheir own welfare yields collective

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disaster.So people try to do good things forthemselves, which can often yield goodoutcomes, can sometimes yield collectiveinferior or suboptimal outcomes.That's important to know when we thinkabout how society is working to improvehealth.Everyone doing what's good for them, canyield something that's bad for everybody.In other words, given the rules of thegame, we are compelled to do things thatsometimes even backfire against us.Recall the outcomes that when we try todo the right thing and save ourselves, weend up worse off.And there's all kinds away that math herecan be manipulated and show differentoutcomes.My point for this course at this time isto remind you that sometimes purposive,individual rationality can yieldcollective disaster.This also seen in the classic the story

of The Tragedy of the Commons.And there's various ways to tell thisstory.Here we see some cows, sometimes it'sdescribed as sheep.And the story is this, that there's acommons in the cow case there's a field,in the sheep it's a field, for health itmight be clean water or healthy places orexcellent health care.The point is there's some resource that'sscarce.In, in a tragedy of the commons,there are

farmers, cow herders, or sheep herders,who individually want to have more cowsin the field.They have more milk or more meat, andtherefore make more money.But the problem becomes when everyone,all the farmers or shepherds.When they all put the extra sheep orextra cow into the field what happens, ofcourse, is the grass, the field becomesdepleted and then everybody loses.Same thing can happen in these healthissues.

When everyone is trying to have cleanwater and you can't restrict everyone.Then the clean water resource can bedepleted.Healthy places, everyone wants a healthyplace, more production, you can lose itentirely and the same thing with healthcare.So the tragedy of the commons applies notonly for this sort of fictitious

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shepherds or cowherders but applies tohealth.And again the basic story is, individualsacting rationally, clearly, on their ownbehalf, can yield collective disaster.So what are the solutions to the tragedyof the commons?There's many, I'm going to give you a fewFirst, maybe people can change theirmotivation.Instead of being self interested, theycould be other regarding, altruists.Maybe there's more peace and love in theworld.Wouldn't that be nice?Another solution is to privatize thepasture.Give it to someone, or break it up intosections.And everyone has their own private part.When you own your own private part.You're less apt to over graze it, becausethen you undermine your own success.You'll only graze as many cows or sheep

as the pasture can tolerate.There could be some sort of cooperationwhere the other farmer grazes more sheepone year.You do more another year.All kinds of cooperation schemes canemerge.Finally, and interestingly, you couldcreate a government, a third body, thatsets the rules of the game.Who gets to graze their cows?Who doesn't, and what are the penaltiesfor overgrazing?

All related to this is the problem calledcollective action.Which I think is the core problem inimproving the public health.The classic text comes from 1965 byMancur Olson.And you here, here you see a picture ofthe book.Here's the story.How do a bunch of people get together toget something done.It's not easy.[COUGH] The first problem, of course, is

that people have to find one another.It might be easier in this age of theInternet.But still people who want to get stuffdone have to somehow get together.And then they have to decide Hm, do wehave the same interest or do wedivergence interests.Many people have divergent interest andeven if they're the same.

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Are they the same enough?So you gotta get together and find somecommon purpose.That's the first step to solving thecollective action problem.And that collective action problem mightbe providing healthcare for all, might bemitigating environmental pollution,abating lead paint in houses.Coming together to solve major healthproblems that have big impacts onpopulation health.The other part, though, of the collectionaction problem is called the free-riderIf everyone's going to spend their time,energy, and perhaps money, to solve aproblem, why should I do that?Why should I spend any of my time, money,or energy if all of you guys are going tosolve it.I can win or have more by notparticipating, by letting you solve it.So, this is called the free rider, and itcomes up all the time, and so one of the

key questions for social science,political science in particular, and nowfor social epidemiology is how do wesolve the big public health problemsthrough collective action, wherein firstwe've got to come together and findcommon interest.And then once we do, how do we deal withthe free-rider?Those who would rather not spend theirtime and energy.Now what's critical, is when, you don'twant to spend your time and energy, why

would I want to spend mine?And so the whole effort of collective[UNKNOWN] action or social movement canbreak down.So, why don't you think about, how todeal with the free-rider problem?