WEBVTT 00:00:00.857 --> 00:00:03.230 I'm going to talk about the strategizing brain. 00:00:03.254 --> 00:00:05.640 We're going to use an unusual combination of tools 00:00:05.664 --> 00:00:07.254 from game theory and neuroscience 00:00:07.278 --> 00:00:10.548 to understand how people interact socially when value is on the line. NOTE Paragraph 00:00:10.572 --> 00:00:14.044 So game theory is a branch of, originally, applied mathematics, 00:00:14.068 --> 00:00:17.496 used mostly in economics and political science, a little bit in biology, 00:00:17.520 --> 00:00:20.363 that gives us a mathematical taxonomy of social life, 00:00:20.387 --> 00:00:22.706 and it predicts what people are likely to do 00:00:22.730 --> 00:00:24.046 and believe others will do 00:00:24.070 --> 00:00:27.043 in cases where everyone's actions affect everyone else. 00:00:27.067 --> 00:00:30.752 That's a lot of things: competition, cooperation, bargaining, 00:00:30.776 --> 00:00:33.128 games like hide-and-seek and poker. NOTE Paragraph 00:00:33.954 --> 00:00:35.887 Here's a simple game to get us started. 00:00:35.911 --> 00:00:38.375 Everyone chooses a number from zero to 100. 00:00:38.399 --> 00:00:40.859 We're going to compute the average of those numbers, 00:00:40.883 --> 00:00:44.922 and whoever's closest to two-thirds of the average wins a fixed prize. 00:00:44.946 --> 00:00:47.692 So you want to be a little bit below the average number 00:00:47.716 --> 00:00:48.868 but not too far below, 00:00:48.892 --> 00:00:52.513 and everyone else wants to be a little bit below the average number as well. 00:00:52.537 --> 00:00:54.084 Think about what you might pick. 00:00:54.108 --> 00:00:55.269 As you're thinking, 00:00:55.293 --> 00:00:58.347 this is a toy model of something like selling in the stock market 00:00:58.371 --> 00:00:59.989 during a rising market: 00:01:00.013 --> 00:01:03.123 You don't want to sell too early, because you miss out on profits, 00:01:03.147 --> 00:01:06.195 but you don't want to wait too late, to when everyone else sells, 00:01:06.219 --> 00:01:07.444 triggering a crash. 00:01:07.468 --> 00:01:11.048 You want to be a little bit ahead of the competition, but not too far ahead. NOTE Paragraph 00:01:11.072 --> 00:01:14.157 OK, here's two theories about how people might think about this, 00:01:14.181 --> 00:01:15.381 then we'll see some data. 00:01:15.405 --> 00:01:17.001 Some of these will sound familiar 00:01:17.025 --> 00:01:19.084 because you probably are thinking that way. 00:01:19.108 --> 00:01:20.760 I'm using my brain theory to see. 00:01:20.784 --> 00:01:24.198 A lot of people say, "I really don't know what people are going to pick, 00:01:24.222 --> 00:01:27.749 so I think the average will be 50" -- they're not being strategic at all -- 00:01:27.773 --> 00:01:29.835 and "I'll pick two-thirds of 50, that's 33." 00:01:29.859 --> 00:01:31.013 That's a start. 00:01:31.037 --> 00:01:33.426 Other people, who are a little more sophisticated, 00:01:33.450 --> 00:01:34.691 using more working memory, 00:01:34.715 --> 00:01:36.344 say, "I think people will pick 33, 00:01:36.368 --> 00:01:38.579 because they're going to pick a response to 50, 00:01:38.603 --> 00:01:40.901 and so I'll pick 22, which is two-thirds of 33." 00:01:40.925 --> 00:01:43.492 They're doing one extra step of thinking, two steps. 00:01:43.913 --> 00:01:45.117 That's better. 00:01:45.141 --> 00:01:47.868 Of course, in principle, you could do three, four or more, 00:01:47.892 --> 00:01:49.838 but it starts to get very difficult. 00:01:49.862 --> 00:01:51.793 Just like in language and other domains, 00:01:51.817 --> 00:01:54.882 we know that it's hard for people to parse very complex sentences 00:01:54.906 --> 00:01:56.197 with a recursive structure. 00:01:56.221 --> 00:01:58.370 This is called the cognitive hierarchy theory, 00:01:58.394 --> 00:02:00.643 something I've worked on and a few other people, 00:02:00.667 --> 00:02:02.437 and it indicates a kind of hierarchy, 00:02:02.461 --> 00:02:05.900 along with some assumptions about how many people stop at different steps 00:02:05.924 --> 00:02:07.931 and how the steps of thinking are affected 00:02:07.955 --> 00:02:10.399 by lots of interesting variables and variant people, 00:02:10.423 --> 00:02:11.623 as we'll see in a minute. NOTE Paragraph 00:02:11.647 --> 00:02:14.785 A very different theory, a much more popular one and an older one, 00:02:14.809 --> 00:02:17.288 due largely to John Nash of "A Beautiful Mind" fame, 00:02:17.312 --> 00:02:19.397 is what's called "equilibrium analysis." 00:02:19.421 --> 00:02:22.234 So if you've ever taken a game theory course at any level, 00:02:22.258 --> 00:02:24.035 you'll have learned a bit about this. 00:02:24.059 --> 00:02:25.887 An equilibrium is a mathematical state 00:02:25.911 --> 00:02:29.211 in which everybody has figured out exactly what everyone else will do. 00:02:29.235 --> 00:02:30.579 It is a very useful concept, 00:02:30.603 --> 00:02:32.657 but behaviorally, it may not exactly explain 00:02:32.681 --> 00:02:35.955 what people do the first time they play these types of economic games 00:02:35.979 --> 00:02:37.900 or in situations in the outside world. 00:02:37.924 --> 00:02:40.725 In this case, the equilibrium makes a very bold prediction, 00:02:40.749 --> 00:02:43.458 which is: everyone wants to be below everyone else, 00:02:43.482 --> 00:02:45.183 therefore, they'll play zero. NOTE Paragraph 00:02:45.723 --> 00:02:46.880 Let's see what happens. 00:02:46.904 --> 00:02:49.011 This experiment's been done many, many times. 00:02:49.035 --> 00:02:51.237 Some of the earliest ones were done in the '90s 00:02:51.261 --> 00:02:53.067 by me and Rosemarie Nagel and others. 00:02:53.091 --> 00:02:55.611 This is a beautiful data set of 9,000 people 00:02:55.635 --> 00:02:58.856 who wrote in to three newspapers and magazines that had a contest. 00:02:58.880 --> 00:03:00.923 The contest said, send in your numbers, 00:03:00.947 --> 00:03:04.281 and whoever is close to two-thirds of the average will win a big prize. 00:03:04.305 --> 00:03:08.038 As you can see, there's so much data here, you can see the spikes very visibly. 00:03:08.062 --> 00:03:10.776 There's a spike at 33 -- those are people doing one step. 00:03:10.800 --> 00:03:13.019 There is another spike visible at 22. 00:03:13.043 --> 00:03:16.059 Notice, by the way, most people pick numbers right around there; 00:03:16.083 --> 00:03:18.241 they don't necessarily pick exactly 33 and 22. 00:03:18.265 --> 00:03:20.181 There's something a bit noisy around it. 00:03:20.205 --> 00:03:22.173 But you can see those spikes on that end. 00:03:22.197 --> 00:03:23.682 There's another group of people 00:03:23.706 --> 00:03:26.193 who seem to have a firm grip on equilibrium analysis, 00:03:26.217 --> 00:03:27.953 because they're picking zero or one. 00:03:27.977 --> 00:03:29.624 But they lose, right? 00:03:29.648 --> 00:03:33.032 Because picking a number that low is actually a bad choice 00:03:33.056 --> 00:03:35.795 if other people aren't doing equilibrium analysis as well. 00:03:35.819 --> 00:03:37.494 So they're smart, but poor. NOTE Paragraph 00:03:37.518 --> 00:03:39.582 (Laughter) NOTE Paragraph 00:03:39.606 --> 00:03:42.073 Where are these things happening in the brain? 00:03:42.097 --> 00:03:45.790 One study by Coricelli and Nagel gives a really sharp, interesting answer. 00:03:45.814 --> 00:03:49.626 They had people play this game while they were being scanned in an fMRI, 00:03:49.650 --> 00:03:50.807 and two conditions: 00:03:50.831 --> 00:03:52.217 in some trials, they're told, 00:03:52.241 --> 00:03:54.838 "You're playing another person who's playing right now. 00:03:54.862 --> 00:03:57.865 We'll match up your behavior at the end and pay you if you win." 00:03:57.889 --> 00:04:00.617 In other trials, they're told, "You're playing a computer, 00:04:00.641 --> 00:04:02.165 they're just choosing randomly." 00:04:02.189 --> 00:04:04.351 So what you see here is a subtraction of areas 00:04:04.375 --> 00:04:07.334 in which there's more brain activity when you're playing people 00:04:07.358 --> 00:04:08.936 compared to playing the computer. 00:04:08.960 --> 00:04:11.496 And you see activity in some regions we've seen today, 00:04:11.520 --> 00:04:13.769 medial prefrontal cortex, dorsomedial, up here, 00:04:13.793 --> 00:04:16.185 ventromedial prefrontal cortex, anterior cingulate, 00:04:16.209 --> 00:04:19.224 an area that's involved in lots of types of conflict resolution, 00:04:19.248 --> 00:04:20.984 like if you're playing "Simon Says," 00:04:21.008 --> 00:04:24.181 and also the right and left temporoparietal junction. 00:04:24.205 --> 00:04:27.080 And these are all areas which are fairly reliably known to be 00:04:27.104 --> 00:04:29.355 part of what's called a "theory of mind" circuit 00:04:29.379 --> 00:04:30.905 or "mentalizing circuit." 00:04:30.929 --> 00:04:34.436 That is, it's a circuit that's used to imagine what other people might do. 00:04:34.460 --> 00:04:38.367 These were some of the first studies to see this tied in to game theory. NOTE Paragraph 00:04:38.778 --> 00:04:41.024 What happens with these one- and two-step types? 00:04:41.048 --> 00:04:43.299 So, we classify people by what they picked, 00:04:43.323 --> 00:04:46.853 and then we look at the difference between playing humans versus computers, 00:04:46.877 --> 00:04:48.942 which brain areas are differentially active. 00:04:48.966 --> 00:04:50.934 On the top, you see the one-step players. 00:04:50.958 --> 00:04:52.343 There's almost no difference. 00:04:52.367 --> 00:04:55.244 The reason is, they're treating other people like a computer, 00:04:55.268 --> 00:04:56.419 and the brain is too. 00:04:56.443 --> 00:04:59.466 The bottom players, you see all the activity in dorsomedial PFC. 00:04:59.490 --> 00:05:02.497 So we know the two-step players are doing something differently. NOTE Paragraph 00:05:02.521 --> 00:05:04.522 Now, what can we do with this information? 00:05:04.546 --> 00:05:06.987 You might be able to look at brain activity and say, 00:05:07.011 --> 00:05:10.654 "This person will be a good poker player," or "This person's socially naive." 00:05:10.678 --> 00:05:14.213 We might also be able to study things like development of adolescent brains 00:05:14.237 --> 00:05:16.674 once we have an idea of where this circuitry exists. NOTE Paragraph 00:05:16.698 --> 00:05:17.850 OK. Get ready. 00:05:17.874 --> 00:05:19.974 I'm saving you some brain activity, 00:05:19.998 --> 00:05:22.735 because you don't need to use your hair detector cells. 00:05:22.759 --> 00:05:26.021 You should use those cells to think carefully about this game. 00:05:26.045 --> 00:05:27.558 This is a bargaining game. 00:05:27.582 --> 00:05:30.599 Two players who are being scanned using EEG electrodes 00:05:30.623 --> 00:05:33.401 are going to bargain over one to six dollars. 00:05:33.425 --> 00:05:36.108 If they can do it in 10 seconds, they'll earn that money. 00:05:36.132 --> 00:05:39.281 If 10 seconds go by and they haven't made a deal, they get nothing. 00:05:39.305 --> 00:05:40.928 That's kind of a mistake together. 00:05:40.952 --> 00:05:43.568 The twist is that one player, on the left, 00:05:43.592 --> 00:05:45.941 is informed about how much on each trial there is. 00:05:45.965 --> 00:05:48.683 They play lots of trials with different amounts each time. 00:05:48.707 --> 00:05:50.804 In this case, they know there's four dollars. 00:05:50.828 --> 00:05:54.428 The uninformed player doesn't know, but they know the informed player knows. 00:05:54.452 --> 00:05:56.647 So the uninformed player's challenge is to say, 00:05:56.671 --> 00:05:57.822 "Is this guy being fair, 00:05:57.846 --> 00:05:59.775 or are they giving me a very low offer 00:05:59.799 --> 00:06:03.572 in order to get me to think there's only one or two dollars available to split?" 00:06:03.596 --> 00:06:06.315 in which case they might reject it and not come to a deal. 00:06:06.339 --> 00:06:09.392 So there's some tension here between trying to get the most money 00:06:09.416 --> 00:06:12.091 but trying to goad the other player into giving you more. 00:06:12.115 --> 00:06:14.593 And the way they bargain is to point on a number line 00:06:14.617 --> 00:06:16.296 that goes from zero to six dollars. 00:06:16.320 --> 00:06:19.154 They're bargaining over how much the uninformed player gets, 00:06:19.178 --> 00:06:21.179 and the informed player will get the rest. 00:06:21.203 --> 00:06:23.347 So this is like a management-labor negotiation 00:06:23.371 --> 00:06:25.101 in which the workers don't know 00:06:25.125 --> 00:06:28.331 how much profits the privately held company has, 00:06:28.355 --> 00:06:30.790 and they want to maybe hold out for more money, 00:06:30.814 --> 00:06:33.210 but the company might want to create the impression 00:06:33.234 --> 00:06:36.194 that there's very little to split: "I'm giving the most I can." NOTE Paragraph 00:06:36.218 --> 00:06:39.622 First, some behavior: a bunch of the subject pairs play face-to-face. 00:06:39.646 --> 00:06:42.086 We have other data where they play across computers. 00:06:42.110 --> 00:06:44.684 That's an interesting difference, as you might imagine. 00:06:44.708 --> 00:06:46.482 But a bunch of the face-to-face pairs 00:06:46.506 --> 00:06:49.233 agree to divide the money evenly every single time. 00:06:49.257 --> 00:06:51.919 Boring. It's just not interesting neurally. 00:06:52.308 --> 00:06:54.532 It's good for them -- they make a lot of money. 00:06:54.556 --> 00:06:56.096 But we're interested in: 00:06:56.120 --> 00:06:59.873 Can we say something about when disagreements occur versus don't occur? NOTE Paragraph 00:06:59.897 --> 00:07:02.659 So this is the other group of subjects, who often disagree. 00:07:02.683 --> 00:07:06.160 They bicker and disagree and end up with less money. 00:07:06.184 --> 00:07:09.147 They might be eligible to be on "Real Housewives," the TV show. NOTE Paragraph 00:07:09.171 --> 00:07:10.259 (Laughter) NOTE Paragraph 00:07:10.283 --> 00:07:11.966 You see on the left, 00:07:11.990 --> 00:07:14.624 when the amount to divide is one, two or three dollars, 00:07:14.648 --> 00:07:16.270 they disagree about half the time; 00:07:16.294 --> 00:07:18.645 when it's four, five, six, they agree quite often. 00:07:18.669 --> 00:07:20.868 This turns out to be something that's predicted 00:07:20.892 --> 00:07:22.853 by a very complicated type of game theory 00:07:22.877 --> 00:07:25.984 you should come to graduate school at CalTech and learn about. 00:07:26.008 --> 00:07:28.396 It's a little too complicated to explain right now, 00:07:28.420 --> 00:07:31.063 but the theory tells you that this shape should occur. 00:07:31.087 --> 00:07:33.149 Your intuition might tell you that, too. NOTE Paragraph 00:07:33.173 --> 00:07:36.040 Now I'm going to show you the results from the EEG recording. 00:07:36.064 --> 00:07:37.215 Very complicated. 00:07:37.239 --> 00:07:39.631 The right brain schematic is the uninformed person, 00:07:39.655 --> 00:07:41.055 and the left is the informed. 00:07:41.079 --> 00:07:43.825 Remember that we scanned both brains at the same time, 00:07:43.849 --> 00:07:46.118 so we can ask about time-synced activity 00:07:46.142 --> 00:07:49.158 in similar or different areas simultaneously, 00:07:49.182 --> 00:07:51.447 just like if you wanted to study a conversation, 00:07:51.471 --> 00:07:54.049 and you were scanning two people talking to each other. 00:07:54.073 --> 00:07:56.331 You'd expect common activity in language regions 00:07:56.355 --> 00:07:58.316 when they're listening and communicating. 00:07:58.340 --> 00:08:02.171 So the arrows connect regions that are active at the same time. 00:08:02.195 --> 00:08:03.517 The direction of the arrows 00:08:03.541 --> 00:08:06.307 flows from the region that's active first in time, 00:08:06.331 --> 00:08:10.126 and the arrowhead goes to the region that's active later. 00:08:10.150 --> 00:08:12.197 So in this case, if you look carefully, 00:08:12.221 --> 00:08:14.244 most of the arrows flow from right to left. 00:08:14.268 --> 00:08:17.552 That is, it looks as if the uninformed brain activity 00:08:17.576 --> 00:08:19.187 is happening first, 00:08:19.211 --> 00:08:23.063 and then it's followed by activity in the informed brain. 00:08:23.087 --> 00:08:26.538 And by the way, these are trials where their deals were made. 00:08:26.562 --> 00:08:28.319 This is from the first two seconds. 00:08:28.343 --> 00:08:31.499 We haven't finished analyzing this data, so we're still peeking in, 00:08:31.523 --> 00:08:34.931 but the hope is that we can say something in the first couple of seconds 00:08:34.955 --> 00:08:36.918 about whether they'll make a deal or not, 00:08:36.942 --> 00:08:39.947 which could be very useful in thinking about avoiding litigation 00:08:39.971 --> 00:08:41.835 and ugly divorces and things like that. 00:08:41.859 --> 00:08:45.936 Those are all cases in which a lot of value is lost by delay and strikes. NOTE Paragraph 00:08:46.630 --> 00:08:48.794 Here's the case where the disagreements occur. 00:08:48.818 --> 00:08:51.212 You can see it looks different than the one before. 00:08:51.236 --> 00:08:52.577 There's a lot more arrows. 00:08:52.601 --> 00:08:55.252 That means that the brains are synced up more closely 00:08:55.276 --> 00:08:56.896 in terms of simultaneous activity, 00:08:56.920 --> 00:08:59.123 and the arrows flow clearly from left to right. 00:08:59.147 --> 00:09:01.435 That is, the informed brain seems to be deciding, 00:09:01.459 --> 00:09:03.651 "We're probably not going to make a deal here." 00:09:03.675 --> 00:09:06.418 And then later, there's activity in the uninformed brain. NOTE Paragraph 00:09:06.799 --> 00:09:09.203 Next, I'm going to introduce you to some relatives. 00:09:09.227 --> 00:09:11.388 They're hairy, smelly, fast and strong. 00:09:11.412 --> 00:09:13.906 You might be thinking back to your last Thanksgiving. NOTE Paragraph 00:09:13.930 --> 00:09:14.946 (Laughter) NOTE Paragraph 00:09:14.970 --> 00:09:17.446 Maybe, if you had a chimpanzee with you. 00:09:17.470 --> 00:09:21.476 Charles Darwin and I and you broke off from the family tree from chimpanzees 00:09:21.500 --> 00:09:22.900 about five million years ago. 00:09:22.924 --> 00:09:24.735 They're still our closest genetic kin. 00:09:24.759 --> 00:09:26.478 We share 98.8 percent of the genes. 00:09:26.502 --> 00:09:29.463 We share more genes with them than zebras do with horses. 00:09:29.487 --> 00:09:31.397 And we're also their closest cousin. 00:09:31.421 --> 00:09:34.042 They have more genetic relation to us than to gorillas. 00:09:34.066 --> 00:09:36.805 So, how humans and chimpanzees behave differently 00:09:36.829 --> 00:09:38.923 might tell us a lot about brain evolution. NOTE Paragraph 00:09:39.326 --> 00:09:41.626 This is an amazing memory test 00:09:41.650 --> 00:09:44.442 from [Kyoto], Japan, the Primate Research Institute, 00:09:44.466 --> 00:09:46.469 where they've done a lot of this research. 00:09:46.493 --> 00:09:49.317 This goes back a ways. They're interested in working memory. 00:09:49.341 --> 00:09:51.057 The chimp will see, watch carefully, 00:09:51.081 --> 00:09:54.665 they'll see 200 milliseconds' exposure -- that's fast, eight movie frames -- 00:09:54.689 --> 00:09:56.666 of numbers one, two, three, four, five. 00:09:56.690 --> 00:09:58.935 Then they disappear and are replaced by squares, 00:09:58.959 --> 00:10:00.586 and they have to press the squares 00:10:00.610 --> 00:10:02.810 that correspond to the numbers from low to high 00:10:02.834 --> 00:10:04.137 to get an apple reward. 00:10:04.161 --> 00:10:05.658 Let's see how they can do it. NOTE Paragraph 00:10:16.478 --> 00:10:17.640 This is a young chimp. 00:10:17.664 --> 00:10:20.581 The young ones are better than the old ones, just like humans. NOTE Paragraph 00:10:20.605 --> 00:10:21.607 (Laughter) NOTE Paragraph 00:10:21.631 --> 00:10:23.109 And they're highly experienced, 00:10:23.133 --> 00:10:25.456 they've done this thousands of times. 00:10:25.480 --> 00:10:28.366 Obviously there's a big training effect, as you can imagine. NOTE Paragraph 00:10:28.390 --> 00:10:29.402 (Laughter) NOTE Paragraph 00:10:29.426 --> 00:10:31.574 You can see they're very blasé and effortless. 00:10:31.598 --> 00:10:34.809 Not only can they do it very well, they do it in a sort of lazy way. NOTE Paragraph 00:10:34.833 --> 00:10:35.837 (Laughter) NOTE Paragraph 00:10:35.861 --> 00:10:37.623 Who thinks you could beat the chimps? NOTE Paragraph 00:10:37.647 --> 00:10:38.707 (Laughter) NOTE Paragraph 00:10:38.731 --> 00:10:40.266 Wrong. (Laughter) NOTE Paragraph 00:10:40.290 --> 00:10:42.875 We can try. We'll try. Maybe we'll try. NOTE Paragraph 00:10:42.899 --> 00:10:46.893 OK, so the next part of the study I'm going to go quickly through 00:10:46.917 --> 00:10:49.893 is based on an idea of Tetsuro Matsuzawa. 00:10:49.917 --> 00:10:53.037 He had a bold idea he called the "cognitive trade-off hypothesis." 00:10:53.061 --> 00:10:56.543 We know chimps are faster and stronger; they're also obsessed with status. 00:10:56.567 --> 00:10:59.248 His thought was, maybe they've preserved brain activities 00:10:59.272 --> 00:11:00.875 and practice them in development 00:11:00.899 --> 00:11:04.714 that are really, really important to them to negotiate status and to win, 00:11:04.738 --> 00:11:07.730 which is something like strategic thinking during competition. 00:11:07.754 --> 00:11:09.290 So we're going to check that out 00:11:09.314 --> 00:11:11.941 by having the chimps actually play a game 00:11:11.965 --> 00:11:14.475 by touching two touch screens. NOTE Paragraph 00:11:14.499 --> 00:11:17.559 The chimps are interacting with each other through the computers. 00:11:17.583 --> 00:11:18.932 They'll press left or right. 00:11:18.956 --> 00:11:22.434 One chimp is called a matcher; they win if they press left-left, 00:11:22.458 --> 00:11:25.603 like a seeker finding someone in hide-and-seek, or right-right. 00:11:25.627 --> 00:11:27.232 The mismatcher wants to mismatch; 00:11:27.256 --> 00:11:29.955 they want to press the opposite screen of the chimp. 00:11:29.979 --> 00:11:32.451 And the rewards are apple cube rewards. 00:11:32.475 --> 00:11:34.802 So here's how game theorists look at these data. 00:11:34.826 --> 00:11:36.848 This is a graph of the percentage of times 00:11:36.872 --> 00:11:39.078 the matcher picked right on the x-axis 00:11:39.102 --> 00:11:41.256 and the percentage of times they picked right 00:11:41.280 --> 00:11:43.485 by the mismatcher on the y-axis. 00:11:43.509 --> 00:11:46.838 So a point here is the behavior by a pair of players, 00:11:46.862 --> 00:11:49.058 one trying to match, one trying to mismatch. 00:11:49.082 --> 00:11:52.399 The NE square in the middle -- actually, NE, CH and QRE -- 00:11:52.423 --> 00:11:55.547 those are three different theories of Nash equilibrium and others, 00:11:55.571 --> 00:11:57.254 tells you what the theory predicts, 00:11:57.278 --> 00:11:59.403 which is that they should match 50-50, 00:11:59.427 --> 00:12:01.854 because if you play left too much, for example, 00:12:01.878 --> 00:12:04.844 I can exploit that if I'm the mismatcher by then playing right. 00:12:04.868 --> 00:12:07.840 And as you can see, the chimps -- each chimp is one triangle -- 00:12:07.864 --> 00:12:10.523 are circled around, hovering around that prediction. NOTE Paragraph 00:12:11.205 --> 00:12:12.911 Now we move the payoffs. 00:12:12.935 --> 00:12:16.422 We're going to make the left-left payoff for the matcher a little higher. 00:12:16.446 --> 00:12:17.941 Now they get three apple cubes. 00:12:17.965 --> 00:12:21.240 Game theoretically, that should make the mismatcher's behavior shift: 00:12:21.264 --> 00:12:24.771 the mismatcher will think, "Oh, this guy's going to go for the big reward, 00:12:24.795 --> 00:12:27.323 so I'll go to the right, make sure he doesn't get it." 00:12:27.347 --> 00:12:29.375 And as you can see, their behavior moves up 00:12:29.399 --> 00:12:32.097 in the direction of this change in the Nash equilibrium. 00:12:32.121 --> 00:12:34.367 Finally, we changed the payoffs one more time. 00:12:34.391 --> 00:12:35.639 Now it's four apple cubes, 00:12:35.663 --> 00:12:38.496 and their behavior again moves towards the Nash equilibrium. 00:12:38.520 --> 00:12:41.194 It's sprinkled around, but if you average the chimps out, 00:12:41.218 --> 00:12:42.792 they're really close, within .01. 00:12:42.816 --> 00:12:45.444 They're actually closer than any species we've observed. NOTE Paragraph 00:12:45.468 --> 00:12:48.566 What about humans? You think you're smarter than a chimpanzee? 00:12:49.350 --> 00:12:52.651 Here's two human groups in green and blue. 00:12:52.675 --> 00:12:55.968 They're closer to 50-50; they're not responding to payoffs as closely. 00:12:55.992 --> 00:12:58.288 And also if you study their learning in the game, 00:12:58.312 --> 00:13:00.413 they aren't as sensitive to previous rewards. 00:13:00.437 --> 00:13:04.022 The chimps play better than the humans, in terms of adhering to game theory. 00:13:04.046 --> 00:13:07.247 And these are two different groups of humans, from Japan and Africa; 00:13:07.271 --> 00:13:08.611 they replicate quite nicely. 00:13:08.635 --> 00:13:11.180 None of them are close to where the chimps are. NOTE Paragraph 00:13:11.670 --> 00:13:12.964 So, some things we learned: 00:13:12.988 --> 00:13:16.734 people seem to do a limited amount of strategic thinking using theory of mind. 00:13:16.758 --> 00:13:18.852 We have preliminary evidence from bargaining 00:13:18.876 --> 00:13:21.791 that early warning signs in the brain might be used to predict 00:13:21.815 --> 00:13:24.446 whether there'll be a bad disagreement that costs money, 00:13:24.470 --> 00:13:26.709 and chimps are "better" competitors than humans, 00:13:26.733 --> 00:13:27.975 as judged by game theory. NOTE Paragraph 00:13:27.999 --> 00:13:29.150 Thank you. NOTE Paragraph 00:13:29.174 --> 00:13:32.293 (Applause)