337 | Kevin Zollman on Game Theory, Signals, and Meaning

Game theory is a way of quantitatively describing what happens any time one thing interacts with another thing, when both things have goals and potential rewards. That's a pretty broad class of interesting events, so it is unsurprising that game theory is a useful way of thinking about everything from international relations to the evolution of peacock feathers. I talk with philosopher Kevin Zollman about what game theory is and how it gets used in biology and human interactions. We discuss how thinking in game-theoretic terms can help understand the origin of meaning and intentionality in human language. Blog post with transcript: https://www.preposterousuniverse.com/podcast/2025/12/01/337-kevin-zollman-on-game-theory-signals-and-meaning/ Support Mindscape on Patreon https://www.patreon.com/seanmcarroll. Kevin Zollman received his Ph. D. in philosophy from the University of California, Irvine. He is currently the Herbert A. Simon Professor of Philosophy and Social and Decision Sciences in the Department of Philosophy at Carnegie Mellon University. He is also an associate fellow at the Center for Philosophy of Science at the University of Pittsburgh, and a visiting professor at the Munich Center for Mathematical Philosophy. He serves as the Director of the Institute for Complex Social Dynamics https://www.cmu.edu/dietrich/social-dynamics/ at CMU. He is the co-author, with Paul Raeburn, of The Game Theorist's Guide to Parenting https://www.amazon.com/Game-Theorists-Guide-Parenting-Negotiators-ebook/dp/B015CLB53M/. Web site https://www.kevinzollman.com/ CMU web page https://www.cmu.edu/dietrich/philosophy/people/faculty/kevin-zollman.html Google Scholar publications https://scholar.google.com/citations?user=XMu62aQAAAAJ&hl=en&oi=ao PhilPeople profile https://philpeople.org/profiles/kevin-zollman

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

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• 0:55Sean Carroll?

  Hello, everyone, and welcome to the Mindscape Podcast. I'm your host, Sean Carroll. You might have noticed that human beings tend to have this thing that happens where one person will interact with another person, bumping into them, talking to them, perhaps exchanging goods or services, or maybe just exchanging pleasantries. Who knows? Very often, one is tempted to say always, you can judge how well such interactions went from the point of view of Person A or Person B. If you wanted to try to quantify it, you could assign points or value to how well you did on the basis of the choices you made during the interaction. Indeed, you could think of it as kind of a game where there was a score,

• 1:39Sean Carroll?

  even if the score is not completely manifest and quantitative. We have a feeling that, oh, that interaction went well or this other interaction didn't. And you know, it's not just human beings that we're talking about here. Animals interact with each other. In a more broader sense, if you want to be forgiving about the term, species interact with each other. Plants interact with each other. Maybe even singled-celled organisms. Maybe even genes in your body. Interact with each other, maybe companies or countries interact with each other and also have a feeling of reward or preference that they can quantify and say, yes, that interaction went well, maybe even I won that interaction or I lost that interaction.

• 2:23Sean Carroll?

  There should be a theory, some sort of general principles that enabled us to talk about all of these games all at once. I mean, of course, there is, you read the title of the podcast, you know what we're talking about here. The idea is game theory. Game theory has an interesting reputation out there in academic circles widely. Many people swear by it. They use it all the time. They develop it. They prove theorems. You know, it goes back to the mid 20th century, Oscar Morgenstern and John von Neumann and others thinking about both economics, but also games of chance, playing poker and things like that. In other corners, game theory has gone too far, as far as some people are concerned.

• 3:03Sean Carroll?

  It is an expression of a sort of natural but resistible urge that human beings have to overly quantify everything and turn everything into numbers. Don't think about it as a competition or a game. Just think about the warm human interactions that you have with people. I don't, I think that those latter people are a little bit off base. I mean, sure, you should not quantify everything in life. Sometimes you should just enjoy things as they go. But the fact that someone else wants to quantify things doesn't get in the way of you having the warm human interaction with another person. The question is, as far as scientific understanding is concerned, can this idea of seeing interactions as

• 3:46Sean Carroll?

  games with payoffs help us? Can it help provide an understanding of why certain people act certain ways, or certain animals, or species, or whatever? And I think there the answer is yes. So as we'll talk about with today's guest, Kevin Zollman, in a certain sense, game theory can't be right or wrong. Game theory is a mathematical tool. It's like arithmetic or calculus, right? It can be useful or not useful to a certain situation, as we will discuss. So Kevin Zollman is a philosopher. Carnegie Mellon University. He's thought a lot about game theory. He's on the pro game theory side of things. He's even written a book, as we'll discuss, The Game Theorist's Guide to Parenting, which has an ironic twist that we'll get to at the very end of this

• 4:30Sean Carroll?

  conversation. And I think we have a wide-ranging kind of fun conversation, both about what game theory is, that'll be super familiar to some of you and less so to others, but then some of the applications for it in thinking about biology, in human relations, and especially, I think, at the end, we talk about the origin of things like meaning, and intentionality, and language, and convention. Given that, game theory, despite the sort of quantitative nature of it, is quite broad in application and conception, it shouldn't be surprising that, in principle, you can explain a lot of human life, the reasons why we act certain

• 5:11Sean Carroll?

  ways and not other ways, by thinking about it in game theoretic terms. So, it's always possible, of course, in anything in science, to think that you have an explanation that works, even though it ends up not being the right one. That's when you go too far, that's what's to be guarded against. But in the meantime, I think that we're really learning a lot, using these tools, especially coupled with computer simulations, things like that. New light is being shed on a lot of the reasons why we behave the way we do. That's what we're all about here at Mindscape, so, let's go.

• 5:57Sean Carroll?

  Kevin Zollman, welcome to the Mindscape Podcast. Oh, thank you so much for having me. So, we're going to talk about game theory. We've talked about game theory a little bit before on the podcast. Herb Gintis was our guest back in the day. But it's sort of an evergreen topic to me, because it's so applicable. I know you like to make the point that it can't be disproven, because it's more like math than it is like, like, science. But, so what is it? What is this game theory of which you speak?

• 6:25Speaker 03

  Yeah, so game theory, I like to call it the science of strategic thinking. So it's the, a broad set of mathematical tools that are used for a bunch of different purposes to understand what we call strategic situations. So this is any time that two individuals are interacting where each of them stands to gain or benefit from the actions of the other. So most commonly, it's used to study humans, but it can also be used to study corporations or countries moving up in scale, and it can also, moving down in scale, be used to study animals and plants and single cellular organisms. So it studies social interaction all across the biological kingdom, from us up and from us down.

• 7:09Sean Carroll?

  Well, yeah, so is there any situation where agents are interacting with goals that couldn't, in principle, be modeled by game theory? Are there lacunae there?

• 7:21Speaker 03

  I think almost anything could be. I think one of the places where it's more and less applicable, the more aware agents are of their situation, the options they have available to them, the options that other people have available to them. So at the far extreme, if I'm engaged in this strategic interaction where I don't even know that I have options available to me, or something like that, I think game theory is sort of least applicable in that setting. Although evolutionary game theory is okay, because they're the decision maker, is sort of evolution who is sense aware. But I think that with the exception of cases where people really just don't even understand that they're in such a setting, game theory can be applicable.

• 8:05Speaker 03

  That doesn't necessarily mean that it's always going to be the most helpful in understanding, but I think that it's at least giving it a shot to see what it can say could be a very valuable way to approach a problem.

• 8:15Sean Carroll?

  Do I recall correctly, or am I making this up, that game theory was in part invented because John von Neumann wanted to beat his friends at poker?

• 8:23Speaker 03

  He was an avid poker player. I don't know all of the details. I do have a friend who has been forever writing a book about the poker game that was going on at the time. There actually was a very small literature about poker that all the famous game theorists contributed to. So John von Neumann, John Nash, there's a bunch of really interesting papers that demonstrated some theoretically really interesting things. The story I've heard, which may be entirely hypocritical, is that Oscar Morgenstern went to John von Neumann with this problem about what utilities were, because economists had used them and then they decided they were hokum and so gave up on them. But you really needed them to do game theory. And then von Neumann said, oh, I know how to solve this. And hence,

• 9:07Speaker 03

  this book, Games and Economic Behavior, was born, which is really the sort of formal beginning of game theory. You can find bits and pieces, of course, that existed long before it, but that's really the moment that it coalesced into a single theory.

• 9:18Sean Carroll?

  And so what are utilities? That's a good question.

• 9:21Speaker 03

  It's a very good question. And in fact, that one of the interesting things is it gets used differently depending on the applications of game theory. So in the classic economic sense, a utility is just a mathematical way of representing what your preferences are. So I like tea more than coffee. So we would say that my utility for tea is higher than my utility for coffee because I prefer it. And that's very weak. You know, you could use any two numbers there. You could you could assign t100 and coffee 1, or you could assign t10 million and coffee negative 2, or whatever. And so then the question is, how do we measure things in more complicated ways to get a little bit more meaningful representation here? So where maybe, you know, doubling utility might mean something,

• 10:06Speaker 03

  or adding 7 might mean something, something like that. And there are a couple of different ways to do it, but John von Neumann and Oscar Morgenstern invented one of them, which is asking people to compare gambles. So if you say, ah, we know that you like coffee more than tea, we need a third thing, so let's add in water. So I like, I said coffee more than tea. I like tea more than coffee. We need a third thing, so let's add in water. So I like tea more than water, more than coffee. And now we can ask, what? Lottery ticket that gives me tea with some probability and coffee with some other probability do I regard as equivalent to water. So it's like, how much risk of getting the thing I hate, coffee? Am I willing to give up in order to get the thing I might, I love, tea?

• 10:50Speaker 03

  And then that allows you to kind of get a scale of like, how much more do I like something? That was, that was von Neumann and Morgenstern's real insight.

• 10:57Sean Carroll?

  So I think that it, it makes it seem very compelling when you say that utilities are a way of just sort of formalizing or quantifying our preferences. And then it spawns a whole back and forth literature about, do we even have preferences? Are people rational? You know, all, all of these questions. Can, can we expand the formalism enough to account for the fact that usually I personally like coffee more than tea, but sometimes I want a cup of tea and I can't even tell you why. It's just like, not always the preference.

• 11:27Speaker 03

  Yeah. And that's a really, really thorny one because, you know, economists love this idea of, well, we don't have to know what's going on in your head. We just need to observe your choices and then we infer your preferences from those. So it's, you know, economists can sort of be psychological, you know, they don't have to worry about the details of psychology. But exactly the question you ask is a really, really thorny one because now there's this question of like, well, when I observe your choices, what exactly is your choice? Is it that you're just making the choice of coffee over tea completely in absence? Or is it that sometimes you want tea because it's later at night? Or is it that sometimes you want tea because you've had coffee seven days in a row and so now you need tea?

• 12:08Speaker 03

  And so one of these questions about how much economics really can divorce itself from psychology has to do with like, how much of that psychology do we have to let back in in order to, in order to discuss it? There's a philosopher of economics, Joanna Tama, gives this really great example. She says, you go to a sushi restaurant and you watch somebody reach out and take the whole thing of wasabi and pop it in their mouth all at once. And now, now, how do you explain what they just did? One is they love wasabi, right? They really, really like wasabi. Another one is they mistakenly thought that was guacamole, or they didn't know what it was, or something like that.

• 12:49Speaker 03

  And, and you, you as an outside observer, without at least asking a few questions, can't answer that at all, because you don't know why they did what they did. And so she argues that this idea that economics can completely divorce itself from the way people think about problems is just the wrong way to think about it. But she thinks you can kind of get away with just letting a little bit back in. And she uses that. It's a great example that, that I really like.

• 13:11Sean Carroll?

  Is there something like a theorem, some kind of representation theorem, that says, under the following reasonable sounding circumstances, any set of preferences can be represented by attaching utility to different outcomes?

• 13:24Speaker 03

  Absolutely. And in fact, there's a, there's a whole collection of them. So there's a big cottage industry in economics, philosophy, statistics, actually, is kind of where it lives in, in the academy, about trying to think about what are the minimal conditions under which you can represent somebody as if they're sort of got a mathematical, you know, utility in their heads and they're making their decisions so as to try and maximize it. All of them are controversial. There are examples that make you suspicious of them as being absolutely correct in, in every sense, but, but they are broadly applicable. They seem pretty reasonable and they certainly do seem to work in a lot of different settings.

• 14:05Speaker 03

  So people's behavior is broadly consistent with maximizing utility, but there are a lot of very famous examples where people do fail. So it's one of these cases where it's a, you know, a mathematical idealization. So it's like, I mean, the debate is, is it like ignoring friction when you calculate the motion of the planets? Like, you know it's wrong, but it's not that bad because there's not that much friction out there. And then the question here is, you know it's wrong, but how bad is it? And that's part of what, there's a big research area in behavioral economics right now, trying to figure out like, how bad is it exactly?

• 14:37Sean Carroll?

  Okay, let's help focus our minds a little bit by giving some examples of some games. I mean, the prisoner's dilemma is one everyone knows, but maybe not everyone knows. But I'll let you pick your favorite game or two, just to give people a sense of how this kind of thing plays out.

• 14:52Speaker 03

  Yeah, so one that's been studied a lot and that I think gives rise to a lot of the intuitions, both about what game theory can do and its problems, is called the ultimatum game. So the ultimatum game is a simple model of fairness. So we imagine that, you know, maybe you get some windfall, you get a hundred dollars, but you have to divide that hundred dollars with me because we own a corporation together or you're just a nice guy or whatever. And so you make a proposal to me of how we're going to split that hundred dollars. So you might say, you'll keep seventy for yourself and you'll give me thirty. Then I have the option of either accepting that, in which case I get what you propose

• 15:32Speaker 03

  and you get what you proposed, or I reject it, in which case we both get nothing. So the idea here is you're giving me a take it or leave it offer and my options are to take it or leave it. The interesting thing about this game is it provides a nice testbed in order to study how people feel about fairness. So if you offer to keep seventy for yourself and give me thirty, do I accept it? Well, I don't know, you know, you could have offered me fifty, right? And you didn't. So there's a sense in which maybe I find that unfair. But also, you could have offered me one dollar and you didn't, so maybe I find it more fair. And we can manipulate that situation in a lot of different ways. We could make it so that you deserved it more, or at least we feel like you deserved

• 16:15Speaker 03

  it more, or that I deserved it more, or, you know, maybe you paid money to be in that position, or maybe you worked harder. And so we can do all of these subtle variations to try and understand how people conceptualize fairness and when it is they're willing to sacrifice money in exchange to get back at somebody who they think treated them unfairly.

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• 17:32Sean Carroll?

  So I love the ultimatum game. I know very, I can see why it is beloved among people who've studied these things. But in a sense, it's a little uncharacteristic to me. I mean, you're saying Alice can give some fraction of her money to Bob, and Bob can either accept it or reject it for both. There's a clear prediction from like perfectly bloodless, Spock-like rationality that says that Alice should give all but a penny, or whatever it is, and Bob should always say yes. And so this game is telling us something, but it's not telling us something about bloodless rationality. It's telling us something about how much human beings deviate from bloodless rationality.

• 18:13Speaker 03

  Absolutely. And the way I put it is, you know, the prediction that you just described is exactly the prediction that we would get to if we assumed that people only cared about their own monetary payoffs. That's the bloodless rationality that you have in mind. But of course, that's not how people actually feel about these things, right? We oftentimes sacrifice money for all sorts of other things. And so, and so as a result, this provides a testbed for us to try and figure out what are those other things? And how can we quantify them and think about them in more detail? So how much am I willing to pay to get back at you for unfairness? So if you offer 30 out of 100 to me, I might say, no, that's unfair. You know, take your offer and go.

• 18:56Speaker 03

  But if it was 300 out of 1,000, or 3,000 out of 10,000, or 3 million out of 10 million, I might grumble, but, but I might accept your $3 million offer because...

• 19:11Speaker 03

  You know, getting back at you isn't worth $3 million, it might be worth 30. And so, you know, these are exactly the kinds of studies that help us to understand what people's preferences really are. Not just, not just about money, but of course, money is part of our preferences. And so trying to figure out how that interacts with other things that we care about, like fairness, revenge, kindness, those sorts of things.

• 19:36Sean Carroll?

  And also, this might be like too, I don't know, nitpicky or inside baseball, but these studies where people actually play these games in front of psychologists and whatever, you know, they have to deal with the fact that in the real world, you're going to have to play games over and over again, right? It will be a repeated game, whether you like it or not. And the psychologist can say to the subjects all they want, no, no, no, pretend you're only going to do this once, pretend it's just money. It's hard for we as human beings to actually do that.

• 20:05Speaker 03

  Oh, for sure. One of my favorite examples of exactly this kind of phenomena is they tried to take this game and go to really small scale societies, like hunter gatherer societies, you know, societies that are way off the grid, and see how they would behave. Because of course, mostly these studies were done on like undergraduates in developed countries and things like that. So they were trying to figure out how to study them there. And one of the big problems was the, the ideal experiment here is one where you're going to interact with this person anonymously, you don't know who they are, there's no way for you to figure that out. But in a small scale society, first of all, it's pretty hard to keep things secret.

• 20:41Sean Carroll?

  There you go.

• 20:42Speaker 03

  If you're, if you suddenly got 30 more dollars, your neighbor might figure it out. But also, in some of these cultures, they're, they have religions that, that make them believe that if you do something wrong, God will punish you, or karma will, will, will come back to you, or something like that. So in a certain sense, you know, God means that all games are repeated, right? There's no, there's no way that, that you can ensure that somebody's action is completely isolated from its consequences way down the road. And so this idea of trying to take games and analyzing them in these complete isolations, that works in some contexts, but doesn't work in others, especially in situations where people think that there may be some deity that might punish them for misbehavior or something.

• 21:26Sean Carroll?

  But just to get it, just to make sure I understand, there nevertheless is a feeling that even whatever cultural baggage one takes along, or whatever impression people have that they might see this person again, or whatever. All of it could, in principle, be modeled by a utility function and a game.

• 21:45Speaker 03

  That's the ideal.

• 21:46Sean Carroll?

  Yeah.

• 21:47Speaker 03

  Is that if you really understand the way the person themselves conceives of the decision, then you can model it. Now, it may not be one of these cute little simple games, because, you know, if God's going to punish you, then you've got to think about God as another player who's going to do something and the consequences of that. But in theory, all of this is modelable. And so the hope is that by really understanding how people conceive of the situations, we can design more accurate and more representative games to try and really conceive of how they view the world and how they conceive of a particular problem to help understand and predict their behavior in those situations.

• 22:23Sean Carroll?

  Do you want to offer up any other examples of games? Because, I mean, the variety, even in just the two-person world with two choices, is pretty impressive.

• 22:33Speaker 03

  It's huge, yeah. I mean, there are so many interesting ones. One that gets used in biology a lot is something that gets called chicken or hawk-dove. One of the problems is there's two names for everything, because game theory gets used in two different fields. So the chicken story comes from the old 1950s greaser movies. So you've got, you know, two guys driving their cars straight at each other, and they have the choice of either stay straight or swerve. And the ideal for you as a 1950s greaser dude is you want to go straight while the other guy swerves, because now you're the hero, the other guy's the chicken, you get the girl, and everything's great forever after, I guess.

• 23:15Speaker 03

  But, of course, you don't want both of you to go head-on, because if you both go head-on, you're both dead and the movie ends very differently. So it's an interesting example where the best outcomes are one person stays straight and the other swerves, because one person gets to be the hero and the other one doesn't. But there's a conflict. Who gets to be the hero and who gets to be the chicken? And so that's a game that gets used both in human interactions, like I just described, but it's also an example in animal contests, because you have a lot of times... Or two animals stumble into a fight with each other, or a potential fight with each other, and they have to decide, do I really want to go through on the fight, potentially

• 23:57Speaker 03

  injuring myself and the other one, or do I want to sort of puff up and act like I'm going to fight to get the other one to run away? And so it was used in the 1970s by Maynard Smith and Price to model animal fights, and has been used a lot in biology since then. Very simple game, but it captures this really fundamental problem, which is like, do you just threaten, but eventually give up? Or do you threaten and really follow through?

• 24:21Sean Carroll?

  So the very simple paradigm is there are two players, they each have two choices, and so there's four possibilities, and they each get a payoff for those four possibilities, and they're each trying to maximize theirs, and we'll see what happens. So what, but there's a bunch of like, results, even from that simple world, about, you know, there is always an equilibrium and things like that.

• 24:43Speaker 03

  Exactly. So in that simple, in that simple game, there are actually what are called three equilibria. So one of them is, I always stay straight, you always swerve, I always get to be the hero, you always are the chicken. And then the other one, vice versa, you always stay straight, and I'm always the chicken, that's another equilibrium. But there's a third, which involves us flipping coins. So I flip a coin to decide whether to stay straight, or, or, or swerve, and you flip a coin to decide whether to stay straight, or swerve. And these are, that one's really interesting, because that one is what's called symmetric. So that one is, we both can flip the same kind of coin, and so you and I are, can be

• 25:27Speaker 03

  otherwise identical, but that's the sort of best you can do when we have to be identical, because if we both stay straight, we crash, that's not good. If we both swerve, we're both chickens, that's not good. So, so that third equilibrium is actually predicted to come about in certain settings, where you might imagine, we're in a big population, we're all the same in some respects, and we're just picked out to play the game against each other, as you might have in like, an animal population.

• 25:52Sean Carroll?

  And this leads right into the real world examples of poker or even sports games, where you have to try to be unpredictable. The idea that there are games for which you can prove mathematically the best strategy has a probability component to it.

• 26:07Speaker 03

  Yeah, and that's really interesting. And it happens in a lot of cases. Sports is the easiest one. So like penalty kicks in soccer, you don't want to always kick to the right or always kick to the left, or serves in tennis, or whether you do the run or the pass in football. There are lots and lots of situations where randomization is the best thing. You mentioned in poker, also true in poker, proven by some of those early folks we talked about earlier, von Neumann and Nash, who showed that randomization in poker is ideal. And so this is really interesting because it gives a role for something, randomization, which feels in a certain sense irrational, or at least outside of rational decision making.

• 26:52Speaker 03

  You flip a coin because you don't know what to do, but here the idea is that in some games at least, flipping a coin is in a certain sense the correct thing to do or the best thing to do.

• 27:01Sean Carroll?

  Yeah, my favorite example there is rock, paper, scissors, right? Where if you just go to play the same thing every time, it's pretty easy to have the other guy figure you out.

• 27:09Speaker 03

  Yeah, and rock, paper, scissors is weirdly a very important game in biology game theory. So there are a couple of interesting examples. One is with lizards. So there's a lizards that have three different kinds of mating strategies. Males can form a harem. Males can be monogamous for a mating season, or males can just run around and mate with whomever they happen to stumble across. And it turns out that if you're in a population of harem-forming lizards, it's best to be the random one, where you just run around and mate with whomever you find. If it's a population of people that just run around and mate with whomever they want to, it's better to be monogamous. And if you're in a population of monogamous, it's better to form a harem.

• 27:54Speaker 03

  So you have that same rock beats scissors and scissors cuts paper and paper beats rock structure. And so you actually have animals that sort of unconsciously, of course, are playing rock, paper, scissors in their mating strategies.

• 28:07Sean Carroll?

  And do they in fact come close to some kind of randomization?

• 28:12Speaker 03

  It's a little hard to tell. It looks like what might be happening is that they're randomized or that that that evolution is randomizing, which is a little bit different in that each individual is definitely doing one of these things. But if any of them gets too much of the population, then evolution sort of pushes back and then the other one takes over. So evolution randomizes in the sense that it makes sure that they're equal proportions so that when you come across one, you're from your perspective, they're randomizing, even though each no individual is like the lizards don't have little lizard coins that they're flipping.

• 28:48Sean Carroll?

  That does actually make sense. Human beings have difficulty randomizing things. I would presume that the lizards are no better than we are.

• 28:55Speaker 03

  Probably not.

• 28:56Sean Carroll?

  Evolution as the game player makes perfect sense.

• 28:58Speaker 03

  Yeah.

• 28:59Sean Carroll?

  So we mentioned that there are always equilibrium, which I think are defined as, you know, you can't just, no one player can improve things just by themselves. Is there always a best strategy to use in these games or is that slippery?

• 29:15Speaker 03

  No, that's actually very slippery. So best strategy is in the language of game theory called a dominant strategy. That is the thing that's like best no matter what the other person does. Some games have them, but not all games. And in fact, there's a real sense in which I would say most games don't. And so there are a lot of times what's best for you to do depends on what you think the other person is going to do. So like in the game of chicken, which we just mentioned, what's best for you to do depends on what you think the other person is going to do. Randomization is okay, but it's not necessarily the best. If I knew for sure that you were going to swerve, then I would rather stay straight rather than randomize. So there's no one strategy that's best.

• 29:57Speaker 03

  Rather, these equilibrium are a prediction about what we think the whole system would do. If the system were sufficiently sophisticated cognitively to reason itself there, like two people thinking through it, or if it's subject to something like evolution or learning where people would play this game repeatedly, figure out what the best strategy is to do and then do that.

• 30:16Sean Carroll?

  I'll have to confess that I don't know in my own brain which jargon terms come from actual game theory and which just come from playing poker. So I know that there are people who talk about playing a dominant strategy versus playing an exploitative strategy. Is that the lingo that's used in game theory?

• 30:33Speaker 03

  We don't use that terminology. I do know it from poker myself as well. So, so one of the things that in zero-sum games in particular, so poker is a zero-sum game because one person's win is always somebody else's loss. So that's what makes it a zero-sum game. In zero-sum games, the equilibrium has this extra special property called minimax, which is not a very informative term. But what that means is it's sort of a safe strategy. That is, even if your opponent is smarter than you and can outthink you and can figure out exactly what you're going to do, if you play the minimax strategy, they, that guarantees they can't take advantage of you. So it's a kind of safety. But the down, the flip side of that is they can't take advantage

• 31:16Speaker 03

  of you, but if they're playing badly, you're not really taking advantage of them either. You're not like doing the best you can. So in poker, when people talk about exploitative strategies, they mean I'm deviating from what is the equilibrium strategy in a way that if you knew I was doing it would be exploitable by you, but I'm doing it because I think I can do that to exploit you, so to speak.

• 31:38Sean Carroll?

  Good. Yeah. And so the best poker players will be able to do both, depending on the situation, presumably the best animals or lizards or, or whatever. But of course poker is one of these examples where you do play hand after hand, right? You're playing many iterations, you're doing this repetitive thing. How good is game theory at studying those things? Not just a single-shot game, but you know ahead of time you're going to be doing it over and over.

• 32:03Speaker 03

  Yeah. And, and, and there is a big area of game theory that studies exactly this. So they have this distinction between what they call one-shot games, which is like you and I sit down, play hand of poker, whatever the winnings are, we take, we leave, that's it. Boring evening of fun, I suppose.

• 32:19Sean Carroll?

  The winner is happy.

• 32:20Speaker 03

  Yeah, yeah, exactly. Exactly. Right. Or what are called repeated games. And repeated games are games where there's, there's a particular interaction that gets, that happens over and over and over again. And then you adopt a strategy. Now that strategy can be super complex because it could be, I'll do one thing early in the night and something else later. I could wait and see how you do and respond to that by changing. My own play and and so repeated games are incredibly complicated, but also incredibly rich. So there's a lot of study. You mentioned the prisoner's dilemma before. This was one of the first famous games that was studied using repeated structure. And there's this very famous infamous strategy called tit for tat,

• 33:02Speaker 03

  which does really well in the repeated prisoner's dilemma, even though it's totally worthless in the one-shot prisoner's dilemma.

• 33:08Sean Carroll?

  Tell us what it is.

• 33:09Speaker 03

  Yeah, sure. So so the prisoners, do you want me to describe the prisoner's dilemma?

• 33:13Sean Carroll?

  Yeah, why not?

• 33:14Speaker 03

  Okay, so the prisoner's dilemma is a game that's used a lot to kind of illustrate the conflict between what's good for a group and what's good for an individual. The story that always goes along with this is you've got, you know, it's like a cop show in the eighties. You've got two people, they're accused of committing a crime, they get put in separate cells. The cops come in and they say, we've got you dead to rights on jaywalking. You're definitely getting a ticket for jaywalking, but we also think you're guilty of a more serious crime with the other guy we've got in the other cell. You've got two options, you can confess or you can stay silent. If you confess, we're letting you off on the jaywalking charge.

• 33:53Speaker 03

  And if you confess and the other guy stays silent, then we're letting you off scot-free because we'll need your testimony against him. If you both confess, however, we don't need your testimony, you've just confessed to a serious crime, so you're going to jail for that. If you stay silent and the other guy confesses, you're in real trouble because you're getting the jaywalking ticket and you're going to jail for the more serious crime.

• 34:19Speaker 03

  But if you both stay silent, all we can do is is get you on jaywalking. So that's the basic story. And the idea here is that each prisoner should reason. Well, regardless of what the other guy does, I do better by confessing. Because if the other guy stays silent and I confess, I get off scot-free. If the other guy's already confessing, well, I'm going to jail no matter what. At least by confessing, I get off on the jaywalking charge. So I should confess no matter what the other guy does. The other guy thinks the same thing and you both confess to a crime and you go to jail for a long time. Where if you just stayed silent, you would have just had to pay for a ticket for jaywalking. So that's the idea is that like there's this like self-interest which drives you to confess. But if both people do that, then they both make themselves worse off.

• 35:04Speaker 03

  So one shot, there's kind of nothing to say here. Like if that's really what the circumstance is, people should confess and it's really just bad. But if it's repeated now, now I can adopt a strategy that, you know, I can say, well, look, if, if you stay silent on this round, I'll stay silent on the next round. And we can kind of have a deal where we'll stay silent so long as the other guy does too. And tit for tat is this strategy that says, I'm going to start out by staying silent. I'm going to cooperate with you. And then on the next round, I'm going to do whatever you did to me on the last round. So if we both stay silent on the first round, then I stay silent on the second, and on the third, and the fourth, and the fifth. And the thing that made this really famous is, uh, uh, Robert

• 35:48Speaker 03

  Axelrod ran a tournament, uh, where he had people submit computer programs in order to try out different strategies. And tit for tat did really, really well in this tournament. So it was sort of regarded as this kind of like, good strategy in the repeated prisoner's dilemma. It's good in some respects and not others. It's actually still somewhat controversial, like how much we really can learn from this particular example. But it's one of the sort of most famous examples of how repeated games can change things. Because what was impossible before, the rationality of staying silent, becomes possible now. Because the threat of punishment, if you confess on me today, then I'll confess on you tomorrow. And maybe we'll confess on each other for forever. The threat of that is sufficient to keep the

• 36:33Speaker 03

  cooperation sustained.

• 36:35Sean Carroll?

  And one of the, I remember that story myself. I forget where I read it years ago, but probably from Douglas Hofstadter or something like that. But one of the interesting things was just the tit for tat was such a short program. And everyone else was trying to write these complicated, sophisticated things with like, no, just do whatever that your opponent did last time.

• 36:54Speaker 03

  Yeah, and that's one of the things that's really, that's really impressive about it is that it's like this balance between immensely simple, like it's not complicated to implement. You don't need a computer scientist to help you figure out the algorithm. But on the other hand, it seems to do so very well. And I think that that part is not controversial. Depending on the weird structures of the tournament, you can actually design things that are really complicated and do even better. And there have been a couple of famous examples. And, and you know, there's a question of like, it does require that you know who you're playing against, which maybe doesn't always work in the animal kingdom. Like if I'm a bacterium interacting with another bacterium, it's not like I recognize them, you know? So, so there, there are some respects in which it's not as applicable as one might

• 37:38Speaker 03

  like, but I, but absolutely that's, it's simplicity is really remarkable, given how well it does. And that's something which I think is, is, is uncontroversial.

• 37:46Speaker 05

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• 38:16Sean Carroll?

  And we won't dwell on the prisoner's dilemma for too long, but I just did want to bring up the idea that people kind of struggle with the moral implications of the prisoner's dilemma. They, they really just resist thinking that, at least in the one-shot version, you should defect, you should be the, the bad person. Like there's, there's no other way out of it. And, and sometimes they try to twist it into saying, well, that's why cooperation in society matters is because it saves us from this issue, which is maybe arguably true, but it's a math problem. You know, it doesn't really necessarily have any moral implications.

• 38:52Speaker 03

  And I think that this is one of the things where people sometimes, uh, this is where the way that we describe the problem can sometimes, uh, not do us any favors. Because the, built into the problem is the assumption that the individual prisoners only care about like the fines or the jail times and they don't care about the other guy, right? They're, these are criminals, right? They don't, they don't, they don't, they have no loyalty, right? Um, but, but maybe we have loyalty or maybe criminals have loyalty too. And if there was that, if I really did care about what happened to the other person, then we need to build that into the game. And so just like we were talking about with the ultimatum game before, the, you know, the prediction of the ultimatum game if, is one thing if we think people only care about money. But if we think they

• 39:36Speaker 03

  care about, you know, other things, then we need to build that in. Same thing is true with the prisoner's dilemma. So a lot of things that people describe as prisoner's dilemmas, a game theorist would actually say, no, that's not a prisoner's dilemma. Like if I care, if I don't want you to go to jail either, we're not playing a prisoner's dilemma, we're playing a different game. And there's a name for the other game and we can talk about that. It's called a stag hunt probably, depending on how much I care. Uh, and, uh, and those have a different analysis. And so oftentimes when people object like, oh, game theorists, they're telling you to be evil and pollute and do all of these other things. Game theorists aren't telling you to do anything. They're just saying, if you care about this, this is what you should do. And so if you care about other people, which I definitely do

• 40:19Speaker 03

  as a game theorist, then I'm often not playing prisoner's dilemmas. I actually think they're quite rare in the world because a lot of times we care about others.

• 40:28Sean Carroll?

  Well, game theorists do have this charming proclivity for telling nice stories about their payoff matrices. And maybe if we could just give people a payoff matrix and say, what is your strategy going to be? Uh, the psychology test results will be a little bit different.

• 40:42Speaker 03

  I think so. And one of the things with the prisoner's dilemma that's really funny is people oftentimes get exactly the moralism that you described, like, hey, shouldn't I do the good thing and stay silent? And I sometimes remind people when they say that, like, remember, we're talking about criminals here. Like, is it good for them to stay silent? Like, sometimes the prisoner's dilemma is good for us. Like, that's what competition is about. Like, two gas stations, if they could cooperate, they could keep the gas prices high in their little town.

• 41:12Sean Carroll?

  There you go.

• 41:12Speaker 03

  Right? And we want them competing with each other. We don't want them to collude, because we, as consumers, benefit, you know, when prices are lower. I mean, maybe gas prices shouldn't be lower because of climate change, but, okay, think about something else, right? You know, and so, you know, the prisoner's dilemma is, sometimes, we, the moral thing, is for people to stay silent, and sometimes the moral thing is for people to confess. And, you know, what's the moral thing here depends on what the, you know, what our example is. And it's funny how moralized people are about criminals staying silent and getting out scot-free on crimes that they committed.

• 41:48Sean Carroll?

  Well, you've given us a couple of examples already of thinking about evolution and animal behavior in game theoretic terms. Is that a accepted thing? Do evolutionary biologists love this kind of thing?

• 42:02Speaker 03

  I would say yes and no. It's definitely a serious methodology in evolutionary game theory. You'll find it in textbooks, you find it in the journals. It's definitely something they do. It can be controversial. There are some ecologists who absolutely hate it. There are some who are more skeptical. So I think it's still something which is a little bit debated. But there's no question that it's got a serious foothold in biology, and it is used pretty regularly, and has been for at least 50 years now, a kind of normal operating theory that gets used in evolutionary theory.

• 42:41Sean Carroll?

  For the ones who hate it, is there any positive spin we could put on why they would do that? Or are they just grumpy old men?

• 42:48Speaker 03

  There are definitely some grumpy old men. Most of them men somehow. But to also, I mean, there are some legitimate questions here, which are, it doesn't, it doesn't answer every question. And there are some interesting examples in biology where there's a kind of game theory answer and there's a non-game theory answer. And it's, I think, genuinely an open question as to which answer is correct. And, and I've worked on, you know, some of the game theory sides of this. And so there are people that just think, well, the game theory answer isn't right and game theory has kind of misled us. And then there are also, you know, biology is a really diverse field. There are some people that just don't like mathematization in general. They don't, they don't think that's a helpful way to understand animal interaction. And so game theory is an example of mathematization.

• 43:33Speaker 03

  So, you know, it's, it, so it, it can be unpopular for lots of reasons. And I've definitely met people who I think, I disagree with them, but I understand where they're coming from. I don't think they're just grumpy or they're just anti, anti-math or something like that. So I don't want to make it out to be those are the only reasons.

• 43:48Sean Carroll?

  So what's an example of an observed behavior in the animal kingdom that there is a quote unquote game theory explanation for and a non-game theory explanation for? I mean, I thought that anything could be a game theory explanation.

• 44:02Speaker 03

  In a sense, and you know, well, let me give you the example and then I'll say something about that. So the, the popular example here is with signaling between potential mates. So here the idea is you've got two individuals who are potentially going to mate with one another. And one of them sends a signal or potentially many signals to the other one. So birds do dances, they have special songs, they, they have brilliant coloration. You know, this happens with humans too, as, as many of us are aware.

• 44:36Sean Carroll?

  We know, yeah, we know.

• 44:37Speaker 03

  We have very elaborate, very elaborate dances that we do as well. And so there are kind of two theories about what's going on here. There are actually more, but there are two like big ones. One is what's called sexual selection, or sometimes called the sexy sons hypothesis. And here the idea is that the, the song or the dance or the... brightly colored feathers doesn't do anything it's just that's what it means to be attractive if you're a bird it's just pretty and it just being pretty and it's being and so males do it or usually males are the are the ones displaying it not always though so

• 45:14Speaker 03

  I'll use males but that's not actually universally true but males that are say do doing the dance are doing it because it will attract potential mates and females who are observing the dance want to mate with the the males who do it because then their sons will do it and their sons will be more attractive and so they'll have more grandchildren so that's the sexy sons hypothesis this can be put in the language of game theory but you have to shoehorn it in a little bit it ends up being a little complicated so that's the kind of non game theory story the game theory story is what's called signaling so here the idea is there is actually something that the mate is demonstrating with its song or its dance or its coloration

• 45:56Speaker 03

  and it's something that's unobservable like how strong are they or how how much resources do they have access to or how you know how much parasites do they have on them at a given time or something like that and so the dance or the song is displaying something is signaling to the other of how much they have like in humans we do this all the time right if I have a super expensive watch I'm signaling to to you how much money I have because I at least had to have enough money to afford that expensive watch

• 46:30Speaker 03

  and so that's the other hypothesis that you and that one is completely game theory like the way that that hypothesis has been spelled out is in terms of game theory so that's one of those cases where there's a kind of game theory story there's another story which you could put in the language of game theory but isn't really naturally said in that way and they're both live hypotheses and and look they both could be true different species could have different explanations for their behaviors and even in one species they could actually both operate they actually are consistent with each other and so it's possible that that they kind of both were true in a certain sense

• 47:03Sean Carroll?

  Under the signaling hypothesis, what is to stop? So, the signaling hypothesis is not just being pretty. That's saying, "I am letting potential mates know that I have some other desirable trait."

• 47:17Speaker 03

  Exactly, yeah.

• 47:18Sean Carroll?

  What is to stop people without that desirable trait from nevertheless sending the same signal?

• 47:23Speaker 03

  Lying, yeah, yeah. Why don't they buy a knockoff Rolex or something? Right. And that's the big question. So, the idea here is that in order to make it so that you're communicating something, that communication has to be un-fakeable, or at least difficult to fake. Otherwise, it would go away. Like, you know, why? If I could just, you know, say, "Hey, I'm worth a billion dollars," you know, and people believed me, well, then maybe I'd just say it all the time, right? But people know not to believe you when you just say that. They demand that you prove it in some way. And so, the question is, how do you make it un-fakeable? That's the big topic.

• 48:04Speaker 03

  And actually, this is a big source of theoretical debate in biology right now. The original story is called the handicap principle. And the idea there is that you have to have some sort of cost that you're spending when you send the signal. So, in order to prove that I have a billion dollars, I have to have something that shows it. So, that's why the Rolex, which is presumably hard to knock off, is what shows it, right? It's like, only somebody who spent that much money on a Rolex could have a genuine Rolex. And so, that's the thought in biology. That was the going theory for a very long time. The idea is, the dance is really hard. It requires a lot of energy to do.

• 48:48Speaker 03

  And so, only those mates that had a lot of excess energy that they could spend doing this complicated dance would be able to, would be willing to spend that cost in order to do it, something like that. It turns out, though, that when ecologists went out and started measuring costs, they didn't find them as much as the theory predicted that they should. And so, biology is kind of an interesting moment right now, where people have gone On back to the drawing board and I've come up with a huge litany of alternative theories. And I'm one of the people who've I've got my names in there a few places coming up with alternative theories. Although I don't want to make myself out to be the most important person, but um. And and now we've got this big menu of game theory theories.

• 49:31Speaker 03

  That all need to be tested because they make slightly different predictions and they demand slightly different experiments. And so people are starting to go back and and do it. So one of the theories that um I worked on with Carl Berkstrom and Simon Hudegger is called the hybrid equilibrium. It's one of these coin flipping examples, kind of a little bit like the the story of chicken from before. And we actually just found what we think is the first wild example of this in hummingbirds. Where hummingbirds are signaling whether they're male or female. But sometimes the females adopt the males colors, uh even though even though they're females. And it's a really interesting example and we did a bunch of uh tests or well, actually I we I I don't do this stuff.

• 50:14Speaker 03

  I collaborate with people who do this stuff. The people that did the hard work uh uh went off and and did some. Some experiments where they showed that we think that this really is an example of this this theoretical prediction of the hybrid equilibrium. And so this is part of like, I think this is where we are right now is. The original theory was really dominant, but it looks like it doesn't quite match the facts. People went back, generated a bunch of new theories, and so now we're in the process of trying to figure out like. Which of these theories fit the facts? How do we design new experiments to figure out which one fit the facts? And some progress is being made, but you know, it's science is hard, so it it takes a while.

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• 51:49Sean Carroll?

  Is this another example where it's evolution flipping the coin, not the individual hummingbirds?

• 51:53Speaker 03

  Yeah, yeah, it's evolution flipping the coin. So, so it's, it's, it's, it's, they don't know what's the biochemical mechanism that decides whether a female becomes a male-looking, brightly colored female or a drab-colored female. And, you know, that's, that's further research that needs to be done. And I think is, you know, really, really interesting question. Because it doesn't seem to be something like you inherit it from your parents. At least, that's what I'm told. But, but they don't, but they don't know. They genuinely don't know what the mechanism is.

• 52:23Sean Carroll?

  This might be an unfair question, but is there any sense in which, knowing what you know now, this theory should have been proposed even before? Did you have a chance of, you know, coming up with it before they had the negative evidence against the?

• 52:36Speaker 03

  Yeah. You know, I mean, maybe this is hindsight is 2020, but I do think that this is a case where the sociology of science kind of went a little awry. The, the first theory came out, it first was expressed verbally. In fact, the person Zahavi, the Zahavis, is a husband and wife couple that proposed it, just, just expressed it verbally. In fact, they hated game theory, but I think that's one of these grumpy, grumpy old people that hate game theory for no good reason. And, and, and initially, people were somewhat skeptical of it, but then it got put in the language of game theory by Alan Graffin and John Maynard Smith. And then, because it was this mystery for so long, and then here was a potential solution,

• 53:20Speaker 03

  everybody just said, that's gotta be it.

• 53:22Sean Carroll?

  Yeah.

• 53:23Speaker 03

  And so, everybody just flocked the first solution that anyone came up with that worked mathematically and just... Decided that's got to be the story. And then it wasn't until we started, you know, finding these examples that didn't fit the theory that anybody thought, hey, wait. Should we come up with some alternative theories? And then, you know, pioneering work of of my collaborator Carl Bergstrom and a bunch of others in the late 90s, early 2000s. Really explore started exploring this wider space of possible explanations. But I think if people had been a little bit more open minded, they might have been able to come up with these, you know, a couple of decades earlier.

• 54:00Sean Carroll?

  So I think this was implicit in what you said, but I just want to be like very down to earth about. What the game is that the peacock is playing like what the choices are what?

• 54:12Speaker 03

  Yeah, so the the the one creature has like, let's say it's the peacock and the peahen. So the peacock's the male, peahen is the female. The peacock's choices are they get to observe something about themselves. Are they a good mate or a bad mate, whatever that means? And then they get to decide conditional on that. Do I grow a big tail or do I not grow a big tail? Okay, so they they they have two options, but they can condition those on their underlying qualities. So they could grow a big tail when they're a good mate and they could grow a big tail when they're a bad mate. So they in a certain sense, they have four options, what to do when I'm good and what to do when I'm bad. The female, the peahen can observe the tail.

• 54:55Speaker 03

  But it can't observe whether the person is a good, whether the peacock is a good good mate or not. So then she observes, does he have a long tail? Does he not have a long tail? And she decides, do I mate with him? Yes, or do I not mate with him? No. So again, she also has four strategies because she can mate with ones with a long tail or not. And she can mate or not with ones that have a short tail. So it's strictly speaking, a four four strategy game. Because each player has four strategies. You could express it. Obviously, you can make these things way more complicated. So you could think about it's not just whether to grow a tail or not, but how long and then the female, you know, so you can make it more complex. But in its simplest form, that's what it is. And the technical term for this is it's a signaling game.

• 55:39Speaker 03

  Or the biologists also call it an action response game.

• 55:44Sean Carroll?

  And presumably in that explanation, the choices being made by the peacock and the peahen are metaphorical. It's really evolution doing that?

• 55:52Speaker 03

  Yeah, absolutely. Yeah, no, most of game theory and biology, the idea here is that they're programmed in with whatever their strategy is. That's in their genes or whatever. And that's not something that an individual peacock or peahen is deciding. But evolution is deciding because if a peacock who has a particular programmed strategy does better than the other peacocks, there'll be more of that type in the next generation, which means that strategy is more prevalent, which means that, and if it continues to do better, it continues to grow. And so evolution is sort of the stand-in for something like the rational actor model. So now it's just evolution is blindly, but still nonetheless,

• 56:34Speaker 03

  guiding animals towards smarter and smarter strategies. And so in the long run, they end up looking like they had decided all of this rationally, even though, of course, we don't think any of them. We're thinking through the decision.

• 56:46Sean Carroll?

  And that sort of way of thinking about it opens up the door to say that game theory is operating at the level of single-celled organisms, or even, you know, genes in organisms.

• 56:56Speaker 03

  Exactly, exactly. Because they're, you know, obviously bacterium are definitely not thinking about what they're doing. Maybe we could hold out some hope for the peacock, but definitely not bacteria. But nonetheless, evolution is leading bacteria towards strategies that are better for the individual. And so as a result, could make it look as if the bacteria are engaging in rational behavior.

• 57:17Sean Carroll?

  So let's take advantage of the fact that you're a professional philosopher in a philosophy department, doing philosophy, and be a little philosophical here. What does that say about the origin and nature and emergence of things like meaning or intentionality or rationality?

• 57:37Speaker 03

  This is a big topic and one that I think is really interesting because these games, these signaling games, like the ones between the peacocks and the peahens, give rise to all sorts of questions. These things start to sound very human-like. You want to say, "The tail means that I'm a good male." And "A bad mate that has a long tail is lying by growing a long tail." And all of these terms that we tend to use in human language suddenly start to look like maybe they apply to animal language as well. And so, we can start to ask these questions of like, "Is it right to say that the peacock's tail means that he's a good mate?" Or that the peacock who's a bad mate with a long tail is lying, or deceiving, or something

• 58:22Speaker 03

  like that. And so, a lot of these human language terms, we can put into game theoretic language. We can say, "Ah, here's how we're going to define lying in terms of game theory. Here's how we're going to define deception in terms of game theory. Here's how we're going to define meaning in terms of game theory." Okay. And by doing that, we can actually start to make these terms, which are notoriously difficult for philosophers, a little bit more precise in that mathematical language. And this is a project I've worked on and several other philosophers have worked on, where we're really trying to come up with theories that make sense of a lot of these terms. And one of the things I've argued is that, once you start doing that, once you start

• 59:04Speaker 03

  defining meaning in a way that's entirely just mathematical in terms of the language of games, it's not so clear that you need a lot of these higher cognitive capacities that we often use. So, if the peacock's tail can mean that that peacock is a good mate, then you don't really need to have an intention or a plan to be able to mean something, because the peacocks aren't planning in that way. And so, a lot of these terms that we use in human language, that really feel very, very completely steeped in notions of intentionality, maybe don't have anything to do with intentionality. Or, maybe there's a core of them that doesn't have anything to do with intentionality. So, we can think about the really sophisticated line, where I'm thinking through how it's

• 59:47Speaker 03

  going to affect, but that there's maybe a core of deception which doesn't require intentionality, something like that.

• 59:54Sean Carroll?

  It's interesting because Alex Rosenberg, who was a former Mindscape guest and a philosopher of science, has brought up meaning, not in the sense of like the meaning of life, but like what a word means.

• 1:00:05Speaker 03

  Yeah.

• 1:00:05Sean Carroll?

  Meaning and intentionality as, in his mind, the biggest challenges for naturalism. And he's a very gung ho naturalist. Might we guess or hope that game theory offers some kind of account about why we start talking about meaning and intentionality?

• 1:00:25Speaker 03

  Absolutely. And I actually do think that a lot of what we, you know, a lot of what meaning is can be captured in game theory. Can we capture absolutely all of it? I don't know yet. I think there's still a lot of open questions. But, you know, there's this idea, there's this kind of fundamental core to what meaning for words is, you know, what, what, and that, I actually think that we can, we can capture in terms of game theory, that this idea of like, what a word means can be captured in terms of its fundamental coordinating aspect. So when I say to you, you know, fetch, fetch me a glass of tea, really, all we care about

• 1:01:08Speaker 03

  is that, you know, you go get me the tea. I'm assuming you also want to do what I ask you to do, right? So if we, if we don't have any conflict, like, I'm saying a bunch of words at you, and what I want is for you to do the thing that I would like you to do, and what you want to do is the thing I want you to do. And so the words are sort of superfluous. They're just this, this grease that we use, or this mechanism that we use to make sure that our behavior coordinates. And so if, if we can think about meaning as, as just like the, in, in that terminology, like, what is it to words having that kind of arbitrary function? Then we can start to define meaning in, in terms of that. This is a philosophical project started a long time ago with, with David Lewis and

• 1:01:52Speaker 03

  Ruth Milliken and a bunch of other people who started to think about this. And, and it's, and it's, Lewis was the first one to put it in the language of game theory. He didn't have a lot of game theory when he was writing in the seventies, but we have a lot more now. And so there are a lot of modern philosophers, myself, Brian Skirms, Kaelin O'Connor, and a bunch of others, who are all trying to figure out how to Think about language using the term, using game theory in a way that allows us to remove a lot of this like non-natural stuff from it and do it in a fully naturalistic way.

• 1:02:27Sean Carroll?

  Yeah, I've heard Caitlin O'Connor, who was another former Mindscape guest, talk about the origin of conventions, like we all drive on the right side of the road and things like that. These are, even I can imagine setting this as a game theory kind of problem, so that makes perfect sense to me. But it, it sounds, and I'm very much in favor of it, but it sounds like there's a much bigger ambition going on here. It reminds me of David Lewis, the philosopher who we just mentioned, and his possible worlds. And he had this idea that a proposition, like snow is white, literally is defined as a set of possible worlds. And ex post facto, we say, yes, it's the possible worlds where snow is white.

• 1:03:10Sean Carroll?

  And there's other possible worlds where snow is blue and just picking out the worlds. Okay, and there's some problems with that and there's some benefits to that, but on the one hand, maybe that's true, and maybe that's a like super explanation for something. But on the other hand, it doesn't sound like what I meant when I said a proposition. And maybe this doesn't, so you're kind of saying, well, you know, via game theory dynamics, a bunch of conventions come to be, and that is meaning. Like, when I say, pick up the phone, you know that those sounds mean you should pick up the phone.

• 1:03:46Speaker 03

  Yep, yep. And that's, and, and look, it does have a counterintuitive flavor to it, exactly the one you described, because now, instead of thinking about it as possible worlds and, and all of that, we're thinking about it fundamentally as about coordinating our action. So, you know, when I tell you something that, that feels like, you know, ultimately, that's about coordinating action. When it's something like, get me the tea, or pick up the phone, or something like that, it makes sense, right? What's the purpose of the phrase, pick up the phone? It's to get you to pick up the phone. When I tell you, you know, Einstein revolutionized physics by overturning Newtonian mechanics, what's the action I'm trying? Trying to get you to do like, you know, like that sentence is meaningful and it's communicate something.

• 1:04:30Speaker 03

  I didn't tell you anything you didn't already know, but you know, like how, you know, what, what's the action that I'm trying to get you to do? And I think that's really what the state of, the state of the field right now. It's like, we can 100% I think we're just right about those very simple sentences, like pick up the phone. And we've got a full theory of those and we've started to develop a theory of slightly more complicated sentences. Um, and, but then the question is like, language is complicated. It's multifaceted, it's used for lots of different purposes and we're sort of chipping away at its different purposes, trying to explain different parts of it. And, uh, you know, the jury's out, I, I have faith, but, uh, but I appreciate why not everyone does.

• 1:05:10Speaker 03

  Uh, I think we'll ultimately be successful at making sense of all of language in these, in these terms, but it's complicated because language is so complicated. And gets used for so many things, especially human language, that there are so many potential, you know, trip hazards everywhere and, and, and things that we have to account for. So that's kind of, I think the, you know, I don't want to say like, we've got it all nailed down. It's completely finished. No questions are left, but I think we've made some real progress in terms of making sense of like things that might be kind of difficult. Like the difference between a command and a statement, or the difference between, uh, you know, uh, uh, different kinds of logical operations. Like if then and stuff like that. So, you know, we're starting to make progress, but, but it's, it's, it's, it's got a ways to go too.

• 1:05:53Sean Carroll?

  So just to make sure that I'm clear on what it would be to succeed. You're, you're hoping to sort of use game theory and some kind of evolutionary dynamics to account for all of the features of human language.

• 1:06:06Speaker 03

  Yeah, that would be the, that would be the great ideal would be that at the end of the day, you know, you come to me with any sentence and you say, why does this sentence mean what it does? And it might be a really complicated game that I put up on the chalkboard, but eventually I put up on the chalkboard, some complicated game. And I point to some part of it and I say, that, that's what, that's what, that's the account of meeting.

• 1:06:26Sean Carroll?

  Right. And this is supposed to hopefully explain things like why there's sometimes a mismatch, and this is the great source of humor, right, between a mismatch between the literal meaning of things you say and their implications.

• 1:06:40Speaker 03

  Yep, absolutely. So this is a topic, I've done some work with a colleague of mine who's a linguist, Mandy Simons, who studies exactly that. Now, she doesn't study it from a game theoretic perspective, but she studies exactly what's called implicature in linguistics, which is this idea that there's the literal thing you say, and then there's what you really mean. The example that we worked on, we worked on, it's a big example, but the simplest illustration of it is the question, can you pass the salt? Because literally, can you pass the salt is a question about your ability to which you literally should answer, yes, I can, right?

• 1:07:17Sean Carroll?

  And there's a time when you're eight years old, when this seems hilarious, that you can say this.

• 1:07:23Speaker 03

  Oh, boy, you love it, right? Exactly. But of course, you know, you and I are adults, at least I am sometimes, and I know, you always are, I am sometimes, all right, that sounded bad. And, you know, and, and so we know that when somebody asks, can you pass the salt, that means, will you please pass the salt? And, and the explanation for that is something like a kind of game theoretic-like reasoning. Well, why would you care whether or not I'm able to pass the salt? The only reason you would care is if you wanted me to pass it. So I should be able to kind of guess that ahead of time and go ahead and pass you the salt.

• 1:08:03Speaker 03

  And so this, this idea was originally put, put together in game theoretic-like language, although not exactly in the language of game theory, and is now, game theory is used quite a bit in understanding pragmatics. And so that's, you know, that's one of those areas where we're starting to try and use game theory in order to understand why it is that, for instance, in this case, the question, can you pass the salt, come, eventually comes to stand in for, are you able to pass the salt?

• 1:08:33Sean Carroll?

  And is this an example where there's a competing theory that is less game theoretic?

• 1:08:38Speaker 03

  That's a good question. I mean, there's, I think that, I think that the answer is really the same answer in both cases, but it's just, some people like putting it in the language of game theory and others find it a little less helpful. I don't know if that's, I'm worried, I'm worried that I may be speaking a little out of turn here. There definitely are more than one answer to that question. And our paper is sort of trying to set apart our answer from another. We put our answer in terms of game theory. I feel like the other one could also be put in terms of game theory. So maybe this is one of those cases where it's just more about what language you feel comfortable speaking, so to speak, than, than whether it is about game theory is, is only, is one of the available answers, but not,

• 1:09:23Speaker 03

  not the other one.

• 1:09:24Sean Carroll?

  Is one of the potential advantages of the game theory approach that I could imagine building a giant computer simulation filled with agent-based models and see whether or not these things actually do come to pass?

• 1:09:35Speaker 03

  Yeah. And that's one of the things we really, really want to know is that, you know, a lot of our history of language is, is buried in the deep past and we're never going to access it, access it. Because, you know, language doesn't get fossilized. Records weren't kept in the early days of human language. So we just don't know how human language originated. And so the ability to use computer simulation models where we try to, you know, try to put together the circumstances that were approximately the circumstances when human language was first emerging or something like that, and then see what emerges in our computer simulations and use that to help us to understand how that particular bit of history went is really important. Because there's just no other

• 1:10:19Speaker 03

  way. Like, if we want to know the answers to these questions, we're not going to figure it out anyway, other than trying to simulate it in one way or the other, whether that's on a computer, or by trying to artificially create it and have humans interact in some kind of like, large-scale game or something like that. There's no other way to, to do it, because it's just, the, the data is long gone.

• 1:10:38Sean Carroll?

  This all makes a lot of sense to me, and I really kind of like it. And I want to, I have two more things to bring up, and you can sort of respond to them in as much length or brevity as you want. One is, you mentioned, as an example that sort of provoked me a little bit, the scientist flocking to an explanation because it all, you know, there's one explanation that seems so good. I presume there is a game theoretic explanation for such flocking and other kind of scientific displays of signals and things like that. We're not, we're not any different, are we?

• 1:11:12Speaker 03

  No, sadly, no. In fact, game theory has been a really powerful tool in trying to understand science in general. And there's a, there's a group of researchers, I'm one of them, trying to take game theory and, and understand scientific behavior in that way. Because, you know, as you exactly like, like you say, scientists are, are people like everyone else, who are driven by a, a, a whole collection of different motivations. Some good, like truth and, and, and justice, and others that are a little bit more, you know, pecuniary, like selfish, you know, like citations and promotions and, and fame and Nobel prizes and the like. And so one thing that's been really interesting here

• 1:11:55Speaker 03

  is if you put this in the language of game theory, you can start to ask questions of, how would science work if it were different? What if we got rid of Nobel prizes? Or what if we got rid of grants? Or what if we changed the way that science works? So you, you know, you, you don't have to send your papers through peer review, or whatever. And just like that, what I was just saying about the origins of human language, we can experiment on what if science were different. We can't do that at a large scale. You know, science is a global enterprise. You can't just all of a sudden get rid of all the grants everywhere and see what happens. But with a game theoretic model, you can at least approximate it. And so people are starting to use game theory to understand the social dynamics of science

• 1:12:37Speaker 03

  and how people's motivations and the structures that they work within affect scientific progress, either for good or for ill. And I think that the answer is almost certainly, some of it's both. And so figuring out what are the good parts and what are the bad parts that we could do better to reform is, is part of that project.

• 1:12:55Sean Carroll?

  And we've seen, this is still part of the same follow-up thing. We've seen public attitudes towards science in flux in terms of trust of experts.

• 1:13:04Speaker 03

  Yeah.

• 1:13:05Sean Carroll?

  Misinformation, things like that. I'm betting there's a game theory explanation for all these things.

• 1:13:10Speaker 03

  Oh, for sure. There always is. There's a game theory explanation for everything.

• 1:13:15Speaker 03

  At least, I think so. But yeah, no, I definitely, misinformation has been a big subject of research. Distrust in science has been a big subject of research. And, you know, it actually connects back to a very old philosophical problem called the novice-to-expert problem, which is you've got this fundamental problem of, you know, you don't know anything about a domain. You've got two people who both claim to be experts. They tell you opposite things. How do you decide who to trust? And solutions to that puzzle can be put in the language of game theory. Like, what would the effect of having, you know, some kind of certification process where experts had to take tests in order to certify themselves? I had a graduate student who worked on the game theory behind those

• 1:13:59Speaker 03

  and whether that solves this problem, conditions under which it would solve this problem. And, you know, there are lots of these variations where we try to use game theory to understand different potential solutions to problems of misinformation. And also, we need to kind of understand the motivations of people who are perpetuating misinformation. Like, what are they trying to achieve? How can we design systems that might lower their incentives? Because a lot of people who, you know, there's the big names, the people who have a vested interest, like the fossil fuels industry doesn't want us to believe in climate change. But, but there are lots of people who are, you know, party to misinformation, but not because they have any particular interest in it.

• 1:14:44Speaker 03

  And so the question is like, what's their motivation? Why are they signing on to and spreading misinformation? And what can be done to either just tell them that they're not, you know, that what they're doing is misinformation? Or think about changing their motivation so that they're less inclined to do that?

• 1:15:00Sean Carroll?

  There are absolutely examples of, I see a person spreading scientific misinformation with potentially damaging real-world consequences, and I honestly can't figure out what the motivation is.

• 1:15:11Speaker 03

  Yeah.

• 1:15:11Sean Carroll?

  Other than some... Tribal partisan signaling, maybe, but otherwise, like, why are you doing this?

• 1:15:18Speaker 03

  Yeah, and that is, I think, a big part of it. I think tribal partisan signaling is a big part of it. And the thing is, that's a huge part of our lives. And I think that that's one of the things that it's, when you see somebody else doing it and you think, oh, my God, why are they doing that? But actually, we're constantly signaling group membership to one another. From the way we cut our hair, to the clothes we wear, to the, to the language that we choose to use. Signaling who's our in-group and who's our out-group is something that humans do quite often, animals do all the time, too. And so I think it's a very kind of basic function of society. And so, understanding that that is that, but then also trying to think about how in these cases can we maybe reduce it?

• 1:15:59Speaker 03

  And I think, you know, how do we make it so that science doesn't become something that's part, that's part of this game that we play? You know, it's fine that I wear a certain kind of shirt to signal the kind of person I am, but maybe not good that I deny science to signal what kind of person I am. You know, these are hard questions, and I'm not going to pretend to have the answer to it. But thinking about it in these, in these terms, I think, does help, because it does help us to understand, like, what could their motivation possibly be? Why are they doing it? And also to kind of, maybe to a certain extent, reduce that, that degree of polarization that those of us that love science might have, where it's like, yeah, it really is bad that they're using science to do this, but it's not like they're doing something that I'm not doing. Exactly. You know, at a fundamental level, we're always signaling our group membership to each other.

• 1:16:45Sean Carroll?

  And the other thing I wanted to bring up was that you have written a book, co-authored a book, I guess, on the game theorist's guide to parenting, which I would not have guessed. What is that about? And what do your kids think about this?

• 1:16:58Speaker 03

  Well, the funniest part of the book is I have no kids, so my kids have no thoughts about it. But the joke that, that my co-author, Paul Raeburn, and I used to always tell is he had enough kids for both of us. So he's the parent, popular science writer, and has written several books on the science of parenting. So the idea was, you know, game theory is this, this tool for interaction and for- You know, strategic situations and actually, parents and kids are in strategic situations all the time. Parents want to get their kids to be quiet during the movie, or parents want to get their kids to do their homework, or parents want to get their kids to stop fighting with each other, or whatever. And game theory has tools for all of these things. And game

• 1:17:42Speaker 03

  theory can help you to think about what is the strategic situation that say, a brother and a sister are having if they're fighting over who gets control of the TV, or something like that. And trying to use game theory techniques for solving these problems can actually help to make life as a parent a little bit easier. I mean, we're definitely not one of these books where we're going to claim that, you know, this one theory is going to solve all your problems, you know, this one weird trick will, will, will, will make it easy to be a parent. But we can help smooth over some of those bumpier parts. Like, we can help to deal with, like, when siblings are fighting with each other, when the kids won't clean up the room, or things like that. And so each, each chapter is about both a different kind of problem, and a different kind of game, and, and a different solution

• 1:18:25Speaker 03

  to it. And we use the game and common solutions to illustrate how solutions that you might have to one little problem might actually be broader solutions. So, for example, you know, every parent knows the "I cut, you pick" trick. So you've got a piece of cake, the kids have to divide the piece of cake between them, so you have one kid cut the cake in half, and then the other kid choose which piece they want. Game theorists have proven that this, this does what you want it to do, it makes them divide it fairly. There's a huge literature about this, actually, it's really interesting. It's amazing how simple problems can get really interesting. Most parents know this, so this isn't news.

• 1:19:05Speaker 03

  But we show that actually, this solution is way broader than you might realize. So, for instance, if the kids are fighting over who gets control of the TV, you can say, "Okay, well, you both have an hour's worth of TV you can watch. One of you decides, one person is going to get the first 15 minutes, and somebody else will get the second 45 minutes." They cut the time that you have in half, and then the other gets to choose, "Do I want the first 15 minutes, or the second 45 minutes?" Or you can do it with... Time with the parent, right? So if two kids are fighting over attention for the parent, you can say, okay, one of you divide my time into two blocks and the other one choose which block they want. Kids have to be a little sophisticated. You're not going to get this to work with your two-year-old, but you might be able to get this to work with your six or

• 1:19:48Speaker 03

  seven-year-old. And so, you know, we go through this and we go through some of the psychology of like when these things are going to start to work for kids. And it's a fun book. I had a, I had a blast writing it. And, and, and my co-author Paul and my editor Amanda Moon were both really, really wonderful. I really had a great time.

• 1:20:03Sean Carroll?

  Can I express a hope for a sequel, The Game Theorist's Guide to Faculty Meetings?

• 1:20:08Speaker 03

  Oh, boy. Yeah.

• 1:20:10Sean Carroll?

  Implicit in the parenting book, I'm not sure.

• 1:20:11Speaker 03

  Yeah, yeah, yeah. Those, those, those are somehow worse fights somehow.

• 1:20:17Speaker 03

  Even more unruly participants than in the house. Yeah. I, I wish I could say I was better at implementing these solutions with faculty meetings.

• 1:20:26Sean Carroll?

  The practical reasoning is a whole nother thing, but we can all aspire to that. This has been super enlightening. Kevin Zollman, thanks very much for being on the Mindscape Podcast.

• 1:20:35Speaker 03

  Great. Thank you so much for having me.

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