WEBVTT 00:00:00.562 --> 00:00:02.815 I'm going to talk about the strategizing brain. 00:00:02.815 --> 00:00:05.053 We're going to use an unusual combination of tools 00:00:05.053 --> 00:00:07.066 from game theory and neuroscience 00:00:07.066 --> 00:00:10.033 to understand how people interact socially when value is on the line. NOTE Paragraph 00:00:10.033 --> 00:00:14.004 So game theory is a branch of, originally, applied mathematics, 00:00:14.004 --> 00:00:16.990 used mostly in economics and political science, a little bit in biology, 00:00:16.990 --> 00:00:20.279 that gives us a mathematical taxonomy of social life 00:00:20.279 --> 00:00:22.410 and it predicts what people are likely to do 00:00:22.410 --> 00:00:23.604 and believe others will do 00:00:23.604 --> 00:00:26.994 in cases where everyone's actions affect everyone else. 00:00:26.994 --> 00:00:30.472 That's a lot of things: competition, cooperation, bargaining, 00:00:30.472 --> 00:00:33.763 games like hide-and-seek, and poker. NOTE Paragraph 00:00:33.763 --> 00:00:36.002 Here's a simple game to get us started. 00:00:36.002 --> 00:00:38.164 Everyone chooses a number from zero to 100, 00:00:38.164 --> 00:00:40.610 we're going to compute the average of those numbers, 00:00:40.610 --> 00:00:44.804 and whoever's closest to two-thirds of the average wins a fixed prize. 00:00:44.804 --> 00:00:47.073 So you want to be a little bit below the average number, 00:00:47.073 --> 00:00:49.309 but not too far below, and everyone else wants to be 00:00:49.309 --> 00:00:51.254 a little bit below the average number as well. 00:00:51.254 --> 00:00:53.833 Think about what you might pick. 00:00:53.833 --> 00:00:57.104 As you're thinking, this is a toy model of something like 00:00:57.104 --> 00:00:59.916 selling in the stock market during a rising market. Right? 00:00:59.916 --> 00:01:02.141 You don't want to sell too early, because you miss out on profits, 00:01:02.141 --> 00:01:04.321 but you don't want to wait too late 00:01:04.321 --> 00:01:06.722 to when everyone else sells, triggering a crash. 00:01:06.722 --> 00:01:09.601 You want to be a little bit ahead of the competition, but not too far ahead. 00:01:09.601 --> 00:01:13.214 Okay, here's two theories about how people might think about this, 00:01:13.214 --> 00:01:14.610 and then we'll see some data. 00:01:14.610 --> 00:01:16.801 Some of these will sound familiar because you probably are 00:01:16.801 --> 00:01:20.600 thinking that way. I'm using my brain theory to see. 00:01:20.600 --> 00:01:23.710 A lot of people say, "I really don't know what people are going to pick, 00:01:23.710 --> 00:01:25.383 so I think the average will be 50." 00:01:25.383 --> 00:01:27.294 They're not being really strategic at all. 00:01:27.294 --> 00:01:30.646 "And I'll pick two-thirds of 50. That's 33." That's a start. 00:01:30.646 --> 00:01:32.538 Other people who are a little more sophisticated, 00:01:32.538 --> 00:01:34.014 using more working memory, 00:01:34.014 --> 00:01:37.918 say, "I think people will pick 33 because they're going to pick a response to 50, 00:01:37.918 --> 00:01:40.886 and so I'll pick 22, which is two-thirds of 33." 00:01:40.886 --> 00:01:43.365 They're doing one extra step of thinking, two steps. 00:01:43.365 --> 00:01:45.982 That's better. And of course, in principle, 00:01:45.982 --> 00:01:47.809 you could do three, four or more, 00:01:47.809 --> 00:01:49.678 but it starts to get very difficult. 00:01:49.678 --> 00:01:52.270 Just like in language and other domains, we know that it's hard for people to parse 00:01:52.270 --> 00:01:55.904 very complex sentences with a kind of recursive structure. 00:01:55.904 --> 00:01:57.638 This is called a cognitive hierarchy theory, by the way. 00:01:57.638 --> 00:02:00.194 It's something that I've worked on and a few other people, 00:02:00.194 --> 00:02:02.414 and it indicates a kind of hierarchy along with 00:02:02.414 --> 00:02:04.668 some assumptions about how many people stop at different steps 00:02:04.668 --> 00:02:06.552 and how the steps of thinking are affected 00:02:06.552 --> 00:02:10.248 by lots of interesting variables and variant people, as we'll see in a minute. 00:02:10.248 --> 00:02:13.634 A very different theory, a much more popular one, and an older one, 00:02:13.634 --> 00:02:17.174 due largely to John Nash of "A Beautiful Mind" fame, 00:02:17.174 --> 00:02:19.414 is what's called equilibrium analysis. 00:02:19.414 --> 00:02:21.868 So if you've ever taken a game theory course at any level, 00:02:21.868 --> 00:02:23.581 you will have learned a little bit about this. 00:02:23.581 --> 00:02:26.436 An equilibrium is a mathematical state in which everybody 00:02:26.436 --> 00:02:28.885 has figured out exactly what everyone else will do. 00:02:28.885 --> 00:02:30.892 It is a very useful concept, but behaviorally, 00:02:30.892 --> 00:02:32.895 it may not exactly explain what people do 00:02:32.895 --> 00:02:35.630 the first time they play these types of economic games 00:02:35.630 --> 00:02:37.963 or in situations in the outside world. 00:02:37.963 --> 00:02:40.301 In this case, the equilibrium makes a very bold prediction, 00:02:40.301 --> 00:02:43.161 which is everyone wants to be below everyone else, 00:02:43.161 --> 00:02:45.452 therefore they'll play zero. NOTE Paragraph 00:02:45.452 --> 00:02:48.461 Let's see what happens. This experiment's been done many, many times. 00:02:48.461 --> 00:02:50.344 Some of the earliest ones were done in the '90s 00:02:50.344 --> 00:02:52.989 by me and Rosemarie Nagel and others. 00:02:52.989 --> 00:02:55.974 This is a beautiful data set of 9,000 people who wrote in 00:02:55.974 --> 00:02:58.854 to three newspapers and magazines that had a contest. 00:02:58.854 --> 00:03:00.668 The contest said, send in your numbers 00:03:00.668 --> 00:03:03.823 and whoever is close to two-thirds of the average will win a big prize. 00:03:03.823 --> 00:03:06.911 And as you can see, there's so much data here, you can see the spikes very visibly. 00:03:06.911 --> 00:03:10.292 There's a spike at 33. Those are people doing one step. 00:03:10.292 --> 00:03:12.789 There is another spike visible at 22. 00:03:12.789 --> 00:03:15.081 And notice, by the way, that most people pick numbers right around there. 00:03:15.081 --> 00:03:17.591 They don't necessarily pick exactly 33 and 22. 00:03:17.591 --> 00:03:19.647 There's something a little bit noisy around it. 00:03:19.647 --> 00:03:21.125 But you can see those spikes, and they're there. 00:03:21.125 --> 00:03:22.835 There's another group of people who seem to have 00:03:22.835 --> 00:03:24.910 a firm grip on equilibrium analysis, 00:03:24.910 --> 00:03:27.305 because they're picking zero or one. 00:03:27.305 --> 00:03:29.394 But they lose, right? 00:03:29.394 --> 00:03:32.586 Because picking a number that low is actually a bad choice 00:03:32.586 --> 00:03:35.406 if other people aren't doing equilibrium analysis as well. 00:03:35.406 --> 00:03:37.518 So they're smart, but poor. NOTE Paragraph 00:03:37.518 --> 00:03:39.606 (Laughter) NOTE Paragraph 00:03:39.606 --> 00:03:41.575 Where are these things happening in the brain? 00:03:41.575 --> 00:03:45.450 One study by Coricelli and Nagel gives a really sharp, interesting answer. 00:03:45.450 --> 00:03:46.958 So they had people play this game 00:03:46.958 --> 00:03:49.175 while they were being scanned in an fMRI, 00:03:49.175 --> 00:03:51.446 and two conditions: in some trials, 00:03:51.446 --> 00:03:52.961 they're told you're playing another person 00:03:52.961 --> 00:03:54.549 who's playing right now and we're going to match up 00:03:54.549 --> 00:03:56.753 your behavior at the end and pay you if you win. 00:03:56.753 --> 00:03:58.731 In the other trials, they're told, you're playing a computer. 00:03:58.731 --> 00:04:00.365 They're just choosing randomly. 00:04:00.365 --> 00:04:02.442 So what you see here is a subtraction 00:04:02.442 --> 00:04:05.192 of areas in which there's more brain activity 00:04:05.192 --> 00:04:08.168 when you're playing people compared to playing the computer. 00:04:08.168 --> 00:04:10.159 And you see activity in some regions we've seen today, 00:04:10.159 --> 00:04:13.396 medial prefrontal cortex, dorsomedial, however, up here, 00:04:13.396 --> 00:04:15.247 ventromedial prefrontal cortex, 00:04:15.247 --> 00:04:16.601 anterior cingulate, an area that's involved 00:04:16.601 --> 00:04:20.238 in lots of types of conflict resolution, like if you're playing "Simon Says," 00:04:20.238 --> 00:04:24.052 and also the right and left temporoparietal junction. 00:04:24.052 --> 00:04:26.518 And these are all areas which are fairly reliably known 00:04:26.518 --> 00:04:28.839 to be part of what's called a "theory of mind" circuit, 00:04:28.839 --> 00:04:30.740 or "mentalizing circuit." 00:04:30.740 --> 00:04:34.118 That is, it's a circuit that's used to imagine what other people might do. 00:04:34.118 --> 00:04:36.358 So these were some of the first studies to see this 00:04:36.358 --> 00:04:38.391 tied in to game theory. NOTE Paragraph 00:04:38.391 --> 00:04:40.631 What happens with these one- and two-step types? 00:04:40.631 --> 00:04:42.702 So we classify people by what they picked, 00:04:42.702 --> 00:04:44.369 and then we look at the difference between 00:04:44.369 --> 00:04:46.344 playing humans versus playing computers, 00:04:46.344 --> 00:04:48.235 which brain areas are differentially active. 00:04:48.235 --> 00:04:49.987 On the top you see the one-step players. 00:04:49.987 --> 00:04:51.507 There's almost no difference. 00:04:51.507 --> 00:04:54.447 The reason is, they're treating other people like a computer, and the brain is too. 00:04:54.447 --> 00:04:58.588 The bottom players, you see all the activity in dorsomedial PFC. 00:04:58.588 --> 00:05:00.639 So we know that those two-step players are doing something differently. NOTE Paragraph 00:05:00.639 --> 00:05:03.735 Now if you were to step back and say, "What can we do with this information?" 00:05:03.735 --> 00:05:05.556 you might be able to look at brain activity and say, 00:05:05.556 --> 00:05:07.055 "This person's going to be a good poker player," 00:05:07.055 --> 00:05:08.984 or, "This person's socially naive," 00:05:08.984 --> 00:05:10.262 and we might also be able to study things 00:05:10.262 --> 00:05:11.860 like development of adolescent brains 00:05:11.860 --> 00:05:15.214 once we have an idea of where this circuitry exists. NOTE Paragraph 00:05:15.214 --> 00:05:17.826 Okay. Get ready. 00:05:17.826 --> 00:05:19.949 I'm saving you some brain activity, 00:05:19.949 --> 00:05:22.759 because you don't need to use your hair detector cells. 00:05:22.759 --> 00:05:25.647 You should use those cells to think carefully about this game. 00:05:25.647 --> 00:05:27.582 This is a bargaining game. 00:05:27.582 --> 00:05:30.138 Two players who are being scanned using EEG electrodes 00:05:30.138 --> 00:05:33.015 are going to bargain over one to six dollars. 00:05:33.015 --> 00:05:35.679 If they can do it in 10 seconds, they're going to actually earn that money. 00:05:35.679 --> 00:05:38.719 If 10 seconds goes by and they haven't made a deal, they get nothing. 00:05:38.719 --> 00:05:40.402 That's kind of a mistake together. 00:05:40.402 --> 00:05:43.219 The twist is that one player, on the left, 00:05:43.219 --> 00:05:45.907 is informed about how much on each trial there is. 00:05:45.907 --> 00:05:48.139 They play lots of trials with different amounts each time. 00:05:48.139 --> 00:05:50.380 In this case, they know there's four dollars. 00:05:50.380 --> 00:05:52.257 The uninformed player doesn't know, 00:05:52.257 --> 00:05:54.311 but they know that the informed player knows. 00:05:54.311 --> 00:05:56.370 So the uninformed player's challenge is to say, 00:05:56.370 --> 00:05:57.840 "Is this guy really being fair 00:05:57.840 --> 00:05:59.694 or are they giving me a very low offer 00:05:59.694 --> 00:06:02.772 in order to get me to think that there's only one or two dollars available to split?" 00:06:02.772 --> 00:06:05.926 in which case they might reject it and not come to a deal. 00:06:05.926 --> 00:06:08.876 So there's some tension here between trying to get the most money 00:06:08.876 --> 00:06:11.449 but trying to goad the other player into giving you more. 00:06:11.449 --> 00:06:13.779 And the way they bargain is to point on a number line 00:06:13.779 --> 00:06:15.585 that goes from zero to six dollars, 00:06:15.585 --> 00:06:18.563 and they're bargaining over how much the uninformed player gets, 00:06:18.563 --> 00:06:20.148 and the informed player's going to get the rest. 00:06:20.148 --> 00:06:22.723 So this is like a management-labor negotiation 00:06:22.723 --> 00:06:25.456 in which the workers don't know how much profits 00:06:25.456 --> 00:06:28.123 the privately held company has, right, 00:06:28.123 --> 00:06:30.491 and they want to maybe hold out for more money, 00:06:30.491 --> 00:06:32.327 but the company might want to create the impression 00:06:32.327 --> 00:06:35.259 that there's very little to split: "I'm giving you the most that I can." NOTE Paragraph 00:06:35.259 --> 00:06:39.490 First some behavior. So a bunch of the subject pairs, they play face to face. 00:06:39.490 --> 00:06:41.326 We have some other data where they play across computers. 00:06:41.326 --> 00:06:43.064 That's an interesting difference, as you might imagine. 00:06:43.064 --> 00:06:45.266 But a bunch of the face-to-face pairs 00:06:45.266 --> 00:06:48.959 agree to divide the money evenly every single time. 00:06:48.959 --> 00:06:51.865 Boring. It's just not interesting neurally. 00:06:51.865 --> 00:06:54.379 It's good for them. They make a lot of money. 00:06:54.379 --> 00:06:57.051 But we're interested in, can we say something about 00:06:57.051 --> 00:06:59.587 when disagreements occur versus don't occur? NOTE Paragraph 00:06:59.587 --> 00:07:01.944 So this is the other group of subjects who often disagree. 00:07:01.944 --> 00:07:04.712 So they have a chance of -- they bicker and disagree 00:07:04.712 --> 00:07:06.019 and end up with less money. 00:07:06.019 --> 00:07:09.936 They might be eligible to be on "Real Housewives," the TV show. 00:07:09.936 --> 00:07:11.872 You see on the left, 00:07:11.872 --> 00:07:14.536 when the amount to divide is one, two or three dollars, 00:07:14.536 --> 00:07:16.184 they disagree about half the time, 00:07:16.184 --> 00:07:18.376 and when the amount is four, five, six, they agree quite often. 00:07:18.376 --> 00:07:20.250 This turns out to be something that's predicted 00:07:20.250 --> 00:07:22.454 by a very complicated type of game theory 00:07:22.454 --> 00:07:25.263 you should come to graduate school at CalTech and learn about. 00:07:25.263 --> 00:07:27.435 It's a little too complicated to explain right now, 00:07:27.435 --> 00:07:30.851 but the theory tells you that this shape kind of should occur. 00:07:30.851 --> 00:07:33.067 Your intuition might tell you that too. NOTE Paragraph 00:07:33.067 --> 00:07:35.307 Now I'm going to show you the results from the EEG recording. 00:07:35.307 --> 00:07:37.660 Very complicated. The right brain schematic 00:07:37.660 --> 00:07:40.523 is the uninformed person, and the left is the informed. 00:07:40.523 --> 00:07:43.323 Remember that we scanned both brains at the same time, 00:07:43.323 --> 00:07:45.715 so we can ask about time-synced activity 00:07:45.715 --> 00:07:48.939 in similar or different areas simultaneously, 00:07:48.939 --> 00:07:51.203 just like if you wanted to study a conversation 00:07:51.203 --> 00:07:53.139 and you were scanning two people talking to each other 00:07:53.139 --> 00:07:55.499 and you'd expect common activity in language regions 00:07:55.499 --> 00:07:57.884 when they're actually kind of listening and communicating. 00:07:57.884 --> 00:08:01.811 So the arrows connect regions that are active at the same time, 00:08:01.811 --> 00:08:03.851 and the direction of the arrows flows 00:08:03.851 --> 00:08:06.331 from the region that's active first in time, 00:08:06.331 --> 00:08:09.899 and the arrowhead goes to the region that's active later. 00:08:09.899 --> 00:08:12.115 So in this case, if you look carefully, 00:08:12.115 --> 00:08:13.972 most of the arrows flow from right to left. 00:08:13.972 --> 00:08:17.252 That is, it looks as if the uninformed brain activity 00:08:17.252 --> 00:08:19.211 is happening first, 00:08:19.211 --> 00:08:22.726 and then it's followed by activity in the informed brain. 00:08:22.726 --> 00:08:26.418 And by the way, these were trials where their deals were made. 00:08:26.418 --> 00:08:28.198 This is from the first two seconds. 00:08:28.198 --> 00:08:30.178 We haven't finished analyzing this data, 00:08:30.178 --> 00:08:32.078 so we're still peeking in, but the hope is 00:08:32.078 --> 00:08:34.642 that we can say something in the first couple of seconds 00:08:34.642 --> 00:08:36.365 about whether they'll make a deal or not, 00:08:36.365 --> 00:08:38.408 which could be very useful in thinking about avoiding litigation 00:08:38.408 --> 00:08:40.336 and ugly divorces and things like that. 00:08:40.336 --> 00:08:43.219 Those are all cases in which a lot of value is lost 00:08:43.219 --> 00:08:46.195 by delay and strikes. NOTE Paragraph 00:08:46.195 --> 00:08:48.225 Here's the case where the disagreements occur. 00:08:48.225 --> 00:08:50.398 You can see it looks different than the one before. 00:08:50.398 --> 00:08:52.647 There's a lot more arrows. 00:08:52.647 --> 00:08:54.158 That means that the brains are synced up 00:08:54.158 --> 00:08:56.710 more closely in terms of simultaneous activity, 00:08:56.710 --> 00:08:58.720 and the arrows flow clearly from left to right. 00:08:58.720 --> 00:09:00.962 That is, the informed brain seems to be deciding, 00:09:00.962 --> 00:09:03.250 "We're probably not going to make a deal here." 00:09:03.250 --> 00:09:06.475 And then later there's activity in the uninformed brain. NOTE Paragraph 00:09:06.475 --> 00:09:08.978 Next I'm going to introduce you to some relatives. 00:09:08.978 --> 00:09:11.239 They're hairy, smelly, fast and strong. 00:09:11.239 --> 00:09:14.429 You might be thinking back to your last Thanksgiving. 00:09:14.429 --> 00:09:17.122 Maybe if you had a chimpanzee with you. 00:09:17.122 --> 00:09:20.583 Charles Darwin and I and you broke off from the family tree 00:09:20.583 --> 00:09:22.842 from chimpanzees about five million years ago. 00:09:22.842 --> 00:09:24.810 They're still our closest genetic kin. 00:09:24.810 --> 00:09:26.547 We share 98.8 percent of the genes. 00:09:26.547 --> 00:09:29.347 We share more genes with them than zebras do with horses. 00:09:29.347 --> 00:09:31.064 And we're also their closest cousin. 00:09:31.064 --> 00:09:34.066 They have more genetic relation to us than to gorillas. 00:09:34.066 --> 00:09:36.594 So how humans and chimpanzees behave differently 00:09:36.594 --> 00:09:39.049 might tell us a lot about brain evolution. NOTE Paragraph 00:09:39.049 --> 00:09:41.650 So this is an amazing memory test 00:09:41.650 --> 00:09:44.466 from Nagoya, Japan, Primate Research Institute, 00:09:44.466 --> 00:09:46.244 where they've done a lot of this research. 00:09:46.244 --> 00:09:48.584 This goes back quite a ways. They're interested in working memory. 00:09:48.584 --> 00:09:50.356 The chimp is going to see, watch carefully, 00:09:50.356 --> 00:09:52.558 they're going to see 200 milliseconds' exposure 00:09:52.558 --> 00:09:54.552 — that's fast, that's eight movie frames — 00:09:54.552 --> 00:09:56.503 of numbers one, two, three, four, five. 00:09:56.503 --> 00:09:58.501 Then they disappear and they're replaced by squares, 00:09:58.501 --> 00:10:00.256 and they have to press the squares 00:10:00.256 --> 00:10:02.577 that correspond to the numbers from low to high 00:10:02.577 --> 00:10:03.916 to get an apple reward. 00:10:03.916 --> 00:10:08.687 Let's see how they can do it. 00:10:16.391 --> 00:10:17.884 This is a young chimp. The young ones 00:10:17.884 --> 00:10:20.667 are better than the old ones, just like humans. 00:10:20.667 --> 00:10:22.259 And they're highly experienced, so they've done this 00:10:22.259 --> 00:10:23.691 thousands and thousands of time. 00:10:23.691 --> 00:10:26.575 Obviously there's a big training effect, as you can imagine. 00:10:27.928 --> 00:10:29.272 (Laughter) 00:10:29.272 --> 00:10:31.207 You can see they're very blasé and kind of effortless. 00:10:31.207 --> 00:10:35.135 Not only can they do it very well, they do it in a sort of lazy way. 00:10:35.135 --> 00:10:38.570 Right? Who thinks you could beat the chimps? 00:10:38.570 --> 00:10:40.166 Wrong. (Laughter) 00:10:40.166 --> 00:10:42.604 We can try. We'll try. Maybe we'll try. NOTE Paragraph 00:10:42.604 --> 00:10:45.194 Okay, so the next part of this study 00:10:45.194 --> 00:10:46.790 I'm going to go quickly through 00:10:46.790 --> 00:10:49.482 is based on an idea of Tetsuro Matsuzawa. 00:10:49.482 --> 00:10:52.511 He had a bold idea that what he called the cognitive trade-off hypothesis. 00:10:52.511 --> 00:10:53.803 We know chimps are faster and stronger. 00:10:53.803 --> 00:10:55.483 They're also very obsessed with status. 00:10:55.483 --> 00:10:58.439 His thought was, maybe they've preserved brain activities 00:10:58.439 --> 00:11:00.607 and they practice them in development 00:11:00.607 --> 00:11:02.458 that are really, really important to them 00:11:02.458 --> 00:11:04.668 to negotiate status and to win, 00:11:04.668 --> 00:11:07.666 which is something like strategic thinking during competition. 00:11:07.666 --> 00:11:09.246 So we're going to check that out 00:11:09.246 --> 00:11:11.676 by having the chimps actually play a game 00:11:11.676 --> 00:11:14.314 by touching two touch screens. 00:11:14.314 --> 00:11:16.754 The chimps are actually interacting with each other through the computers. 00:11:16.754 --> 00:11:18.362 They're going to press left or right. 00:11:18.362 --> 00:11:20.475 One chimp is called a matcher. 00:11:20.475 --> 00:11:22.458 They win if they press left, left, 00:11:22.458 --> 00:11:25.627 like a seeker finding someone in hide-and-seek, or right, right. 00:11:25.627 --> 00:11:26.855 The mismatcher wants to mismatch. 00:11:26.855 --> 00:11:29.931 They want to press the opposite screen of the chimp. 00:11:29.931 --> 00:11:32.475 And the rewards are apple cube rewards. 00:11:32.475 --> 00:11:35.003 So here's how game theorists look at these data. 00:11:35.003 --> 00:11:36.617 This is a graph of the percentage of times 00:11:36.617 --> 00:11:39.235 the matcher picked right on the x-axis, 00:11:39.235 --> 00:11:40.751 and the percentage of times they predicted right 00:11:40.751 --> 00:11:43.619 by the mismatcher on the y-axis. 00:11:43.619 --> 00:11:46.819 So a point here is the behavior by a pair of players, 00:11:46.819 --> 00:11:49.035 one trying to match, one trying to mismatch. 00:11:49.035 --> 00:11:52.315 The NE square in the middle -- actually NE, CH and QRE -- 00:11:52.315 --> 00:11:54.771 those are three different theories of Nash equilibrium, and others, 00:11:54.771 --> 00:11:57.195 tells you what the theory predicts, 00:11:57.195 --> 00:11:59.467 which is that they should match 50-50, 00:11:59.467 --> 00:12:01.635 because if you play left too much, for example, 00:12:01.635 --> 00:12:04.351 I can exploit that if I'm the mismatcher by then playing right. 00:12:04.351 --> 00:12:07.115 And as you can see, the chimps, each chimp is one triangle, 00:12:07.115 --> 00:12:10.962 are circled around, hovering around that prediction. NOTE Paragraph 00:12:10.962 --> 00:12:12.736 Now we move the payoffs. 00:12:12.736 --> 00:12:16.179 We're actually going to make the left, left payoff for the matcher a little bit higher. 00:12:16.179 --> 00:12:17.699 Now they get three apple cubes. 00:12:17.699 --> 00:12:20.499 Game theoretically, that should actually make the mismatcher's behavior shift, 00:12:20.499 --> 00:12:22.089 because what happens is, the mismatcher will think, 00:12:22.089 --> 00:12:23.899 oh, this guy's going to go for the big reward, 00:12:23.899 --> 00:12:26.964 and so I'm going to go to the right, make sure he doesn't get it. 00:12:26.964 --> 00:12:28.629 And as you can see, their behavior moves up 00:12:28.629 --> 00:12:32.077 in the direction of this change in the Nash equilibrium. 00:12:32.077 --> 00:12:34.391 Finally, we changed the payoffs one more time. 00:12:34.391 --> 00:12:35.583 Now it's four apple cubes, 00:12:35.583 --> 00:12:37.755 and their behavior again moves towards the Nash equilibrium. 00:12:37.755 --> 00:12:39.790 It's sprinkled around, but if you average the chimps out, 00:12:39.790 --> 00:12:41.980 they're really, really close, within .01. 00:12:41.980 --> 00:12:45.179 They're actually closer than any species we've observed. NOTE Paragraph 00:12:45.179 --> 00:12:48.372 What about humans? You think you're smarter than a chimpanzee? 00:12:48.372 --> 00:12:51.939 Here's two human groups in green and blue. 00:12:51.939 --> 00:12:55.683 They're closer to 50-50. They're not responding to payoffs as closely, 00:12:55.683 --> 00:12:57.133 and also if you study their learning in the game, 00:12:57.133 --> 00:12:59.118 they aren't as sensitive to previous rewards. 00:12:59.118 --> 00:13:00.482 The chimps are playing better than the humans, 00:13:00.482 --> 00:13:02.905 better in the sense of adhering to game theory. 00:13:02.905 --> 00:13:04.324 And these are two different groups of humans 00:13:04.324 --> 00:13:07.520 from Japan and Africa. They replicate quite nicely. 00:13:07.520 --> 00:13:10.755 None of them are close to where the chimps are. NOTE Paragraph 00:13:10.755 --> 00:13:12.510 So here are some things we learned today. 00:13:12.510 --> 00:13:14.448 People seem to do a limited amount of strategic thinking 00:13:14.448 --> 00:13:16.259 using theory of mind. 00:13:16.259 --> 00:13:18.176 We have some preliminary evidence from bargaining 00:13:18.176 --> 00:13:20.668 that early warning signs in the brain might be used to predict 00:13:20.668 --> 00:13:22.894 whether there will be a bad disagreement that costs money, 00:13:22.894 --> 00:13:24.734 and chimps are better competitors than humans, 00:13:24.734 --> 00:13:27.198 as judged by game theory. 00:13:27.198 --> 00:13:29.055 Thank you. 00:13:29.055 --> 00:13:32.628 (Applause)