WEBVTT 00:00:00.530 --> 00:00:02.960 The following content is provided under a Creative 00:00:02.960 --> 00:00:04.370 Commons license. 00:00:04.370 --> 00:00:07.410 Your support will help MIT OpenCourseWare continue to 00:00:07.410 --> 00:00:11.060 offer high quality educational resources for free. 00:00:11.060 --> 00:00:13.960 To make a donation or view additional materials from 00:00:13.960 --> 00:00:16.680 hundreds of MIT courses, visit mitopencourseware@ocw.mit.edu. 00:00:34.810 --> 00:00:36.870 PROFESSOR: So last week Melissa told you-- 00:00:36.870 --> 00:00:38.140 or a couple days ago-- 00:00:38.140 --> 00:00:39.510 about vision. 00:00:39.510 --> 00:00:42.780 And if there's two huge messages, I think, out of that 00:00:42.780 --> 00:00:46.210 lecture, it's first that even the most simple aspects of 00:00:46.210 --> 00:00:50.150 perception are based on a synthesis between what's out 00:00:50.150 --> 00:00:53.000 there and the rules by which your mind 00:00:53.000 --> 00:00:55.130 interprets the world. 00:00:55.130 --> 00:00:58.510 And what you ultimately see is that interaction, that 00:00:58.510 --> 00:01:02.010 synthesis, that dialogue, that construction between what's 00:01:02.010 --> 00:01:05.620 out there and how your mind chooses to interpret it. 00:01:05.620 --> 00:01:07.990 The second big point is there's a lot of organization 00:01:07.990 --> 00:01:09.890 of the visual system in our brain. 00:01:09.890 --> 00:01:13.240 And we can track its organization from the first 00:01:13.240 --> 00:01:17.460 moment that photons enter your eyes all the way through until 00:01:17.460 --> 00:01:22.940 you recognize a loved one, a word, or an object out there. 00:01:22.940 --> 00:01:27.040 And we said that in the neocortex, the world is 00:01:27.040 --> 00:01:31.190 divided into two big channels of visual processing, which 00:01:31.190 --> 00:01:34.990 are what things are and where things are. 00:01:34.990 --> 00:01:38.220 So now I'm going to pick up on that a little bit today. 00:01:38.220 --> 00:01:41.370 As you go around and see things all the time, what is 00:01:41.370 --> 00:01:43.850 it that you mostly see? 00:01:43.850 --> 00:01:46.430 On an average day, you wake up in the morning. 00:01:50.795 --> 00:01:54.910 I know you're all like, what's he looking for? 00:01:54.910 --> 00:01:56.140 What's the answer? 00:01:56.140 --> 00:01:57.260 But just in everything. 00:01:57.260 --> 00:02:00.740 You see people a lot. 00:02:00.740 --> 00:02:02.070 So faces, we'll talk about that. 00:02:02.070 --> 00:02:04.790 You see objects, chairs, tables in the morning. 00:02:04.790 --> 00:02:06.690 A toothbrush and soap is useful, right? 00:02:06.690 --> 00:02:07.980 You see objects. 00:02:07.980 --> 00:02:11.070 And another huge use of your visual system is reading. 00:02:11.070 --> 00:02:14.040 You see words, right, on books, on computers. 00:02:14.040 --> 00:02:18.050 So we're going to talk a little bit about how we see 00:02:18.050 --> 00:02:21.310 what things are, objects in the world, faces in the world, 00:02:21.310 --> 00:02:23.790 and words so that we can read. 00:02:23.790 --> 00:02:26.480 And we'll talk about both some processes that go on in our 00:02:26.480 --> 00:02:29.610 mind and brain that let us become terrific at recognizing 00:02:29.610 --> 00:02:33.080 what's out there and knowing who we're talking to, what 00:02:33.080 --> 00:02:36.110 we're reading, what we're holding, and so on, and then 00:02:36.110 --> 00:02:38.540 about disorders in the brain that illuminate, I think, a 00:02:38.540 --> 00:02:40.990 little bit about those processes. 00:02:40.990 --> 00:02:46.970 So let me start with objects and agnosia. 00:02:46.970 --> 00:02:50.110 Agnosia means not knowing. 00:02:50.110 --> 00:02:52.680 So we're going to talk about two ways in which people seen 00:02:52.680 --> 00:02:53.440 to not know. 00:02:53.440 --> 00:02:54.910 And that gives us a hint, then, about how 00:02:54.910 --> 00:02:56.980 we actually do know. 00:02:56.980 --> 00:02:58.630 And they've been called apperceptive 00:02:58.630 --> 00:02:59.990 and associative agnosias. 00:02:59.990 --> 00:03:02.400 Apperceptive seems to be people see the parts, but they 00:03:02.400 --> 00:03:03.640 don't pull it together. 00:03:03.640 --> 00:03:05.500 Associative agnosia, they see the whole 00:03:05.500 --> 00:03:06.830 thing pretty decently. 00:03:06.830 --> 00:03:10.390 But they can't figure out what it means, what it is in a 00:03:10.390 --> 00:03:11.640 practical sense. 00:03:11.640 --> 00:03:13.880 And, lastly, I'll talk to you about a very surprising 00:03:13.880 --> 00:03:17.070 finding where people lose knowledge of some kinds of 00:03:17.070 --> 00:03:20.180 objects in the world but not others, and sort of give us a 00:03:20.180 --> 00:03:24.170 new insight into how our brain organizes knowledge. 00:03:24.170 --> 00:03:26.400 So agnosia is a modality-specific inability. 00:03:26.400 --> 00:03:27.840 So we'll talk today about vision. 00:03:27.840 --> 00:03:32.050 There's agnosias in audition, and in touch, and so on. 00:03:32.050 --> 00:03:34.210 But I'll focus just on vision, modality-specific. 00:03:34.210 --> 00:03:35.880 These people are fine if they hold 00:03:35.880 --> 00:03:37.730 something or hear something. 00:03:37.730 --> 00:03:39.520 And it's not explained by things like you don't see so 00:03:39.520 --> 00:03:42.600 well, or you're not paying attention, or you can't speak. 00:03:42.600 --> 00:03:45.640 It seems to be just that you lose the ability to recognize 00:03:45.640 --> 00:03:48.960 by sight what something is. 00:03:48.960 --> 00:03:51.510 So again, apperceptive agnosia, will link it to the 00:03:51.510 --> 00:03:54.460 right hemisphere and associative agnosia to the 00:03:54.460 --> 00:03:55.555 left hemisphere. 00:03:55.555 --> 00:03:58.400 And let me show you examples of what these patients do. 00:03:58.400 --> 00:04:00.620 So here's patients with right hemisphere damage. 00:04:00.620 --> 00:04:04.430 We're attempting, simply, to copy this triangle or copy 00:04:04.430 --> 00:04:04.930 these things. 00:04:04.930 --> 00:04:05.760 It's right in front of them. 00:04:05.760 --> 00:04:06.830 They're copying it. 00:04:06.830 --> 00:04:09.040 And you can see that it's as if they have almost no 00:04:09.040 --> 00:04:10.660 appreciation for what the thing is out there. 00:04:10.660 --> 00:04:13.620 This is a pretty miserable 3. 00:04:13.620 --> 00:04:16.740 Right in front of you, it's as if the whole thing weren't 00:04:16.740 --> 00:04:17.899 cohering for anything. 00:04:17.899 --> 00:04:22.680 Even a shape is just a mysterious bundle of stuff. 00:04:22.680 --> 00:04:24.010 Or we can make it multiple choice. 00:04:24.010 --> 00:04:26.210 Well multiple choice, we know it's easier. 00:04:26.210 --> 00:04:29.400 So all they have to do is cross out which of these four 00:04:29.400 --> 00:04:31.770 things looks like this. 00:04:31.770 --> 00:04:33.360 And they picked the circle here. 00:04:33.360 --> 00:04:35.610 Or instead of the x, they picked the o. 00:04:35.610 --> 00:04:38.010 They're really not getting almost anything about the 00:04:38.010 --> 00:04:39.140 quality of the shape. 00:04:39.140 --> 00:04:41.790 They're really not recognizing what they're looking at. 00:04:41.790 --> 00:04:48.920 Or they'll see this. 00:04:48.920 --> 00:04:52.120 But they'll read it as, when they get this, 7415. 00:04:52.120 --> 00:04:54.420 They won't take the first interpretation, but will come 00:04:54.420 --> 00:04:55.670 up with some other. 00:04:58.250 --> 00:05:01.170 When these patients copy something, they see, right in 00:05:01.170 --> 00:05:03.780 front of them, that elephant. 00:05:03.780 --> 00:05:04.920 You can label things. 00:05:04.920 --> 00:05:06.780 But it's a pretty bad copy. 00:05:06.780 --> 00:05:09.120 It's not just bad artistry. 00:05:09.120 --> 00:05:13.100 It's a bad sense of what the coherent shape is right in 00:05:13.100 --> 00:05:13.600 front of them. 00:05:13.600 --> 00:05:15.510 And their vision is basically fine. 00:05:15.510 --> 00:05:17.920 It's just the shape of it doesn't make any sense. 00:05:21.710 --> 00:05:24.000 Not surprisingly then, maybe these patients also struggle 00:05:24.000 --> 00:05:25.510 when you make things a little harder. 00:05:25.510 --> 00:05:27.640 So what letter is this? 00:05:27.640 --> 00:05:28.400 You can get that. 00:05:28.400 --> 00:05:29.590 You'd have to look a little bit harder. 00:05:29.590 --> 00:05:32.340 Or you might get that this is a cow, or this is a car. 00:05:32.340 --> 00:05:34.610 These patients are terrible at those things. 00:05:34.610 --> 00:05:35.630 As soon as you make it a little bit 00:05:35.630 --> 00:05:39.120 hard, they're finished. 00:05:39.120 --> 00:05:41.400 They're also bad if they have damage in the right 00:05:41.400 --> 00:05:43.460 hemisphere, posteriorly, at what they 00:05:43.460 --> 00:05:44.770 call an unusual view. 00:05:44.770 --> 00:05:49.760 So often we see something like a stapler from this view. 00:05:49.760 --> 00:05:51.770 We rarely quite see it this way. 00:05:51.770 --> 00:05:53.720 But if I showed you this, you could probably make it out. 00:05:53.720 --> 00:05:55.560 It might take you a moment by itself. 00:05:55.560 --> 00:05:58.520 An unusual view of an object that you see, psychologists 00:05:58.520 --> 00:06:01.280 call it a canonical view, which is the usual one. 00:06:01.280 --> 00:06:03.130 And what happens to patients who have damage in the right 00:06:03.130 --> 00:06:04.060 posterior cortex? 00:06:04.060 --> 00:06:08.680 They're terrible at making this unusual perception of a 00:06:08.680 --> 00:06:10.090 common object. 00:06:10.090 --> 00:06:13.300 They're also terrible if they have to see something that's a 00:06:13.300 --> 00:06:14.160 little bit challenging. 00:06:14.160 --> 00:06:17.280 Again, like here's some hats but with shadows. 00:06:17.280 --> 00:06:19.090 Now normally, we don't think about 00:06:19.090 --> 00:06:20.770 shadows as a big problem. 00:06:20.770 --> 00:06:23.590 It is for computers that are meant to see. 00:06:23.590 --> 00:06:26.535 And it is also a big problem for patients with damage to 00:06:26.535 --> 00:06:27.970 the right posterior cortex. 00:06:27.970 --> 00:06:30.590 It's as if they can't pull out the object from the shadow. 00:06:30.590 --> 00:06:34.570 It's all one big glob to them. 00:06:34.570 --> 00:06:37.920 Compare that difficulty just getting basically what's there 00:06:37.920 --> 00:06:40.180 to patients with left hemisphere damage who can't 00:06:40.180 --> 00:06:41.750 recognize an object. 00:06:41.750 --> 00:06:45.160 So here's a patient who was shown pictures of a key, a 00:06:45.160 --> 00:06:48.980 pig, a bird, a train, and was asked to copy them. 00:06:48.980 --> 00:06:50.590 And the copies are actually excellent. 00:06:50.590 --> 00:06:51.970 I mean, they're much better than I would do. 00:06:51.970 --> 00:06:55.050 They're excellent copies, right? 00:06:55.050 --> 00:06:57.100 But even after the patient has made that excellent copy of 00:06:57.100 --> 00:06:58.530 the key, he's asked what is that? 00:06:58.530 --> 00:07:00.970 And the patient says, I don't know. 00:07:00.970 --> 00:07:04.130 Good copy of a pig, "Could be a dog or any other animal." 00:07:04.130 --> 00:07:06.680 That's a dog, but that's it. 00:07:06.680 --> 00:07:08.120 The bird is kind of interesting. 00:07:08.120 --> 00:07:10.050 He draws a pretty good bird, his copy, right? 00:07:10.050 --> 00:07:13.540 But then he says, "It could be a beach stump." And when you 00:07:13.540 --> 00:07:14.630 say that, you can see that. 00:07:14.630 --> 00:07:17.990 But you and I would never come to that conclusion. 00:07:17.990 --> 00:07:19.860 And the train, he gets a little bit of wagon 00:07:19.860 --> 00:07:20.840 or car of some kind. 00:07:20.840 --> 00:07:24.260 It's a larger being pulled by a smaller. 00:07:24.260 --> 00:07:25.670 He vaguely knows it's something. 00:07:25.670 --> 00:07:27.070 But it's not quite right either. 00:07:27.070 --> 00:07:30.910 But he really gets what it is, the shape. 00:07:30.910 --> 00:07:33.350 But it's as if it's stripped of meaning. 00:07:33.350 --> 00:07:37.170 It just doesn't mean anything to him. 00:07:37.170 --> 00:07:39.035 Now we're going to do a video in a moment. 00:07:39.035 --> 00:07:41.320 All right, Tyler? 00:07:41.320 --> 00:07:42.580 I'm going to show you some videos today. 00:07:42.580 --> 00:07:46.640 The problem is that these videos are sort of grainy. 00:07:46.640 --> 00:07:49.650 And there's not really high quality Alan Alda talking on 00:07:49.650 --> 00:07:52.550 Scientific American videos of these patients. 00:07:52.550 --> 00:07:55.100 So the unfortunate thing is in a visual disorders 00:07:55.100 --> 00:07:58.010 demonstration, it's almost as if I'm forcing upon you that 00:07:58.010 --> 00:07:58.950 same visual disorder. 00:07:58.950 --> 00:07:59.140 OK? 00:07:59.140 --> 00:08:01.580 Because you're looking at it, and you go, like, gee. 00:08:01.580 --> 00:08:02.840 No wonder he can't recognize it. 00:08:02.840 --> 00:08:03.650 I can't recognize it. 00:08:03.650 --> 00:08:04.750 So let me tell you. 00:08:04.750 --> 00:08:07.110 In a couple moments he's going to look at a 00:08:07.110 --> 00:08:08.930 picture of a clarinet. 00:08:08.930 --> 00:08:11.060 And if it were a really good video, you 00:08:11.060 --> 00:08:11.800 would see it clearly. 00:08:11.800 --> 00:08:13.820 But there's just not many of these around. 00:08:13.820 --> 00:08:15.870 And these patients are rare that are this perfect. 00:08:15.870 --> 00:08:18.770 So I'm going to make this dark. 00:08:18.770 --> 00:08:21.030 And we'll see-- thank you, Tyler-- 00:08:21.030 --> 00:08:24.060 a patient with visual agnosia. 00:08:24.060 --> 00:08:25.770 And you should be impressed by two things. 00:08:25.770 --> 00:08:26.600 First, he's very verbal. 00:08:26.600 --> 00:08:27.280 He's speaking. 00:08:27.280 --> 00:08:28.350 He's smart. 00:08:28.350 --> 00:08:31.000 A lot of his brain is working just fine. 00:08:31.000 --> 00:08:34.590 And second, you're going to see something kind of 00:08:34.590 --> 00:08:36.940 interesting, which is we talked about the 00:08:36.940 --> 00:08:38.580 where system last time. 00:08:38.580 --> 00:08:41.130 And sometimes people call the where system, 00:08:41.130 --> 00:08:43.169 the system for action. 00:08:43.169 --> 00:08:45.580 Because pretty much like where you grab something, where you 00:08:45.580 --> 00:08:48.060 move, that has a lot to do with the action, the physical 00:08:48.060 --> 00:08:49.030 action in the world. 00:08:49.030 --> 00:08:52.050 So you're going to can see this man unable to recognize 00:08:52.050 --> 00:08:55.120 by his what system, what he's looking at. 00:08:55.120 --> 00:08:57.150 But a little bit of information is going to sneak 00:08:57.150 --> 00:09:00.850 into his where system, and move his hands in a way that 00:09:00.850 --> 00:09:01.600 you'll see appropriate. 00:09:01.600 --> 00:09:02.850 So thanks. 00:09:08.440 --> 00:09:11.240 So it's so funny if you work in-- 00:09:11.240 --> 00:09:14.250 this idea that we only use 10% of our brain. 00:09:14.250 --> 00:09:19.010 I can assure you this man has 95%, 98% of his brain. 00:09:19.010 --> 00:09:19.615 He can speak. 00:09:19.615 --> 00:09:21.145 He can move. 00:09:21.145 --> 00:09:22.610 He can make jokes. 00:09:22.610 --> 00:09:24.230 He can curse at the end there a little bit. 00:09:24.230 --> 00:09:26.810 He can do almost everything that everybody can do. 00:09:26.810 --> 00:09:31.980 But he cannot identify what an object is by vision. 00:09:31.980 --> 00:09:33.700 Because the injury has occurred in the part of the 00:09:33.700 --> 00:09:36.120 brain that's essential for that final step of figuring 00:09:36.120 --> 00:09:38.310 out what you're looking for. 00:09:38.310 --> 00:09:40.670 It's a very specific part of the brain. 00:09:40.670 --> 00:09:44.490 And without it, the rest of his brain can't figure out 00:09:44.490 --> 00:09:45.970 what it's looking at. 00:09:45.970 --> 00:09:47.260 So his sensation is fine. 00:09:47.260 --> 00:09:48.525 He sees where it is. 00:09:48.525 --> 00:09:51.020 And he gets the shape even roughly. 00:09:51.020 --> 00:09:52.530 He thought it was a pen. 00:09:52.530 --> 00:09:55.290 There's something vaguely about the shape. 00:09:55.290 --> 00:09:57.020 His naming is fine. 00:09:57.020 --> 00:10:01.060 But it's as if, again, this idea of a perfect example of 00:10:01.060 --> 00:10:02.840 what we call associative agnosia. 00:10:02.840 --> 00:10:04.990 He has all the shape information it seems like you 00:10:04.990 --> 00:10:07.270 ought to have, all the language information you have. 00:10:07.270 --> 00:10:10.170 But he can't make that move from piecing together what 00:10:10.170 --> 00:10:12.350 something is to knowing what it means. 00:10:12.350 --> 00:10:14.380 And if he doesn't know what it means, he can't 00:10:14.380 --> 00:10:16.710 come up with the name. 00:10:16.710 --> 00:10:20.400 If he smells it or holds it, he says, apple or pipe. 00:10:20.400 --> 00:10:21.640 He knows the name. 00:10:21.640 --> 00:10:24.450 But if he has to look at something and then know what 00:10:24.450 --> 00:10:29.450 it is to name it, if I show you a piece of paper and ask 00:10:29.450 --> 00:10:31.920 you to name it, you have to say, what is it? 00:10:31.920 --> 00:10:33.640 Then I name it. 00:10:33.640 --> 00:10:38.140 He can't make that move in vision to what it is. 00:10:38.140 --> 00:10:40.100 Because so much processing has to occur in your 00:10:40.100 --> 00:10:41.030 brain to get there. 00:10:41.030 --> 00:10:42.590 Even though it seems instantaneous 00:10:42.590 --> 00:10:43.840 and trivial to you. 00:10:46.380 --> 00:10:48.400 It's instantaneous and trivial to you because your brain is 00:10:48.400 --> 00:10:52.050 so brilliant that it accomplishes it. 00:10:55.570 --> 00:10:58.170 Now, there are things out there in the world like 00:10:58.170 --> 00:11:00.130 animals that occur naturally. 00:11:00.130 --> 00:11:02.440 Because they're from an evolutionary tree, they share 00:11:02.440 --> 00:11:03.960 a lot of shapes. 00:11:03.960 --> 00:11:06.660 And there's things out there that are not living, either 00:11:06.660 --> 00:11:08.790 that occur like the moon and the mountain-- they're out 00:11:08.790 --> 00:11:09.800 there sitting-- 00:11:09.800 --> 00:11:12.700 or what we call manufactured objects, things like locks, 00:11:12.700 --> 00:11:17.330 pencils, motorcycles, bulbs, things that humans have made. 00:11:17.330 --> 00:11:20.620 And, of course, humans make shapes as they need to 00:11:20.620 --> 00:11:21.730 construct things. 00:11:21.730 --> 00:11:24.920 They're not constrained by evolutionary forces about what 00:11:24.920 --> 00:11:25.960 shape something is. 00:11:25.960 --> 00:11:29.610 We make a shape as we need it. 00:11:29.610 --> 00:11:32.220 But it was still an amazing discovery in the 1980s that 00:11:32.220 --> 00:11:35.020 they found individual patients who lost the ability to 00:11:35.020 --> 00:11:38.640 recognize things and various specific categories. 00:11:38.640 --> 00:11:42.220 This seems so much like old style, silly phrenology. 00:11:42.220 --> 00:11:45.450 That I can tell you, my colleagues sort of make fun of 00:11:45.450 --> 00:11:48.990 me when I told them people in my field were following this. 00:11:48.990 --> 00:11:53.190 So they found patients who could define by pictures 00:11:53.190 --> 00:11:56.350 manufactured objects, things like pencils, or typewriters, 00:11:56.350 --> 00:11:57.290 or computers. 00:11:57.290 --> 00:12:01.350 But they couldn't identify foods or animals. 00:12:01.350 --> 00:12:03.700 And then they found patients just the opposite who could 00:12:03.700 --> 00:12:07.870 identify foods and animals but not manufactured objects. 00:12:07.870 --> 00:12:09.200 So that's really weird. 00:12:09.200 --> 00:12:12.870 That's as if you had organized in your brain the manufactured 00:12:12.870 --> 00:12:14.380 section here like in a supermarket. 00:12:14.380 --> 00:12:15.520 And here's the animal section. 00:12:15.520 --> 00:12:17.560 And here's the fruit section. 00:12:17.560 --> 00:12:19.660 Really, is that how our mind is organized, like a 00:12:19.660 --> 00:12:21.690 supermarket? 00:12:21.690 --> 00:12:24.390 But then there were some exceptions to these. 00:12:24.390 --> 00:12:25.740 And there are the exceptions that helped us 00:12:25.740 --> 00:12:26.650 inform us on the rules. 00:12:26.650 --> 00:12:29.740 So here's some patients who are really good at identifying 00:12:29.740 --> 00:12:32.740 manufactured things-- again, pencils, things like that-- 00:12:32.740 --> 00:12:35.126 bad at foods and animals. 00:12:35.126 --> 00:12:36.230 But now think about this. 00:12:36.230 --> 00:12:39.030 They were good on body parts. 00:12:39.030 --> 00:12:41.290 How were they good on body parts when they were bad at 00:12:41.290 --> 00:12:41.830 foods and animals? 00:12:41.830 --> 00:12:44.950 Body parts are natural, right? 00:12:44.950 --> 00:12:47.750 And they were bad a musical instruments even though they 00:12:47.750 --> 00:12:50.310 were good on other manufactured things like 00:12:50.310 --> 00:12:52.850 pencils and computers. 00:12:52.850 --> 00:12:54.910 So these were two wrong things. 00:12:54.910 --> 00:12:57.270 And I'm going to try to convince in a moment that the 00:12:57.270 --> 00:13:00.270 way we now understand this is they're good at body parts 00:13:00.270 --> 00:13:02.750 because we know how to use our body. 00:13:02.750 --> 00:13:06.160 And they're bad at musical instruments because musical 00:13:06.160 --> 00:13:10.500 instruments look an awful lot like one another just like 00:13:10.500 --> 00:13:13.280 four-legged animals look a lot like one another. 00:13:13.280 --> 00:13:15.810 That's a funny category for us if we start to divide up 00:13:15.810 --> 00:13:17.330 instruments. 00:13:17.330 --> 00:13:23.260 So the problem is not so much one of natural versus 00:13:23.260 --> 00:13:24.610 unnatural things. 00:13:24.610 --> 00:13:27.960 It's things that we know through vision versus things 00:13:27.960 --> 00:13:30.690 that we know through physical action and use. 00:13:30.690 --> 00:13:31.640 And here's another example. 00:13:31.640 --> 00:13:37.970 The patients who are bad at objects that we use every day, 00:13:37.970 --> 00:13:40.420 like pencils and stuff like that, were pretty good on 00:13:40.420 --> 00:13:43.320 things like billboards and mountains. 00:13:43.320 --> 00:13:47.140 Now only in science fiction movies do you have creatures 00:13:47.140 --> 00:13:48.770 big enough that they're picking up billboards and 00:13:48.770 --> 00:13:50.400 throwing it at helicopters from the military. 00:13:50.400 --> 00:13:51.940 You see that all the time. 00:13:51.940 --> 00:13:52.530 You have the big creature. 00:13:52.530 --> 00:13:53.800 And they pick it up, and they hurl it. 00:13:53.800 --> 00:13:54.410 OK. 00:13:54.410 --> 00:14:00.110 So we don't mostly pick up huge things like mountains and 00:14:00.110 --> 00:14:02.380 large outdoor objects like flag poles. 00:14:02.380 --> 00:14:06.240 They're not things that we pick up and use. 00:14:06.240 --> 00:14:09.320 So it seems like the principle of what's good or bad is more 00:14:09.320 --> 00:14:13.080 about how we experience things through sight or through 00:14:13.080 --> 00:14:14.940 physical action. 00:14:14.940 --> 00:14:17.280 So how do we know things in the world through visual 00:14:17.280 --> 00:14:19.410 experience? 00:14:19.410 --> 00:14:21.160 Unless we're alligator wrestlers, we don't get that 00:14:21.160 --> 00:14:23.540 near that many animals. 00:14:23.540 --> 00:14:26.660 And most of us have other things that we use all the 00:14:26.660 --> 00:14:29.860 time, like bulbs, and pencils, and things like that. 00:14:29.860 --> 00:14:31.350 And evidence for that was this. 00:14:31.350 --> 00:14:34.190 They put humans inside a scanner and looked at their 00:14:34.190 --> 00:14:37.440 brains as they named either line drawings or words. 00:14:37.440 --> 00:14:38.960 So let's think of words. 00:14:38.960 --> 00:14:42.730 So it's just words, and you're naming things like elephant 00:14:42.730 --> 00:14:43.540 and tiger-- 00:14:43.540 --> 00:14:44.600 that's the animal-- 00:14:44.600 --> 00:14:47.670 or tools that you use, like pliers or hammer. 00:14:47.670 --> 00:14:49.330 Visually, they're words. 00:14:49.330 --> 00:14:52.130 But what happens in the brain as you're naming animals? 00:14:52.130 --> 00:14:54.090 It seems like you turn on the visual parts of 00:14:54.090 --> 00:14:54.800 your brain a lot. 00:14:54.800 --> 00:14:56.170 There's no animal in there. 00:14:56.170 --> 00:14:56.980 There's not even a picture of an animal. 00:14:56.980 --> 00:15:00.630 It's just the word elephant or the word cat. 00:15:00.630 --> 00:15:02.860 What happens when you're naming tools? 00:15:02.860 --> 00:15:05.820 In the left hemisphere, we see turned on an area here that's 00:15:05.820 --> 00:15:11.240 involved in visual motion, and here, in physical action of 00:15:11.240 --> 00:15:13.740 moving things in the world. 00:15:13.740 --> 00:15:15.900 All you're doing is naming words. 00:15:15.900 --> 00:15:20.050 But it's as if the knowledge for naming them is located in 00:15:20.050 --> 00:15:23.560 the part of your brain that uses that information. 00:15:23.560 --> 00:15:27.410 If there's things I recognize by sight, the abstract 00:15:27.410 --> 00:15:30.350 knowledge about those things is near my visual system. 00:15:30.350 --> 00:15:34.360 If there's things I recognize by action, using them, the 00:15:34.360 --> 00:15:37.100 abstract knowledge of that is located in your brain near 00:15:37.100 --> 00:15:39.710 parts of your brain that move things and pick up things. 00:15:39.710 --> 00:15:41.760 So all of a sudden, it makes sense that you can get 00:15:41.760 --> 00:15:43.360 separation in these forms of knowledge. 00:15:43.360 --> 00:15:46.310 Because they reside in your brain near the parts of your 00:15:46.310 --> 00:15:49.400 brain that use them and communicate with them. 00:15:49.400 --> 00:15:51.160 So again, this idea that if it's a [INAUDIBLE] like a 00:15:51.160 --> 00:15:54.775 scissors, your knowledge about scissors will reside in the 00:15:54.775 --> 00:15:57.300 parts of the brain that act upon scissors. 00:15:57.300 --> 00:16:01.540 If it's something like a bird that you mostly see, knowledge 00:16:01.540 --> 00:16:04.540 about that bird, not just how it looks, but everything, will 00:16:04.540 --> 00:16:08.120 reside in parts of the brain that are focused on vision. 00:16:08.120 --> 00:16:09.940 So it's as if your knowledge is moved to the part of the 00:16:09.940 --> 00:16:14.040 brain that interacts with the form of knowledge. 00:16:14.040 --> 00:16:15.360 So now let's talk about faces. 00:16:15.360 --> 00:16:19.170 Faces are a huge thing for us. 00:16:19.170 --> 00:16:22.370 There's at least two huge things we do with faces. 00:16:22.370 --> 00:16:26.140 We recognize who people are and what their moods are, 00:16:26.140 --> 00:16:29.760 angry, happy, nice, and so on. 00:16:29.760 --> 00:16:31.500 So here's one person. 00:16:31.500 --> 00:16:32.660 Here's another person. 00:16:32.660 --> 00:16:34.870 When I first used this picture, he wasn't a governor. 00:16:34.870 --> 00:16:35.570 He was a movie star. 00:16:35.570 --> 00:16:37.690 And now he's an ex-governor. 00:16:37.690 --> 00:16:39.250 And you have the problem that you have to 00:16:39.250 --> 00:16:40.630 recognize a lot of people. 00:16:40.630 --> 00:16:42.440 Because you have all your classmates, and friends, and 00:16:42.440 --> 00:16:44.930 family members, and a lot of people out there. 00:16:44.930 --> 00:16:46.670 And not only that, you have to recognize the various 00:16:46.670 --> 00:16:48.940 expressions they have, which are terribly important for how 00:16:48.940 --> 00:16:53.900 we communicate with people moment to moment all the time. 00:16:53.900 --> 00:16:56.120 So we could say with faces, our big job is who are we 00:16:56.120 --> 00:16:57.260 looking at. 00:16:57.260 --> 00:17:01.420 A friend, or foe, somebody loved, somebody we don't know. 00:17:01.420 --> 00:17:02.600 Who is that person? 00:17:02.600 --> 00:17:04.609 And then what's the expression that we can 00:17:04.609 --> 00:17:05.470 read from their face? 00:17:05.470 --> 00:17:08.140 That's a huge part of our lives as social animals, as 00:17:08.140 --> 00:17:11.300 people who interact with other people. 00:17:11.300 --> 00:17:16.460 So you saw a film last time of a patient with prosopagnosia. 00:17:16.460 --> 00:17:18.940 Your book, this time, talks about a Dr. P. He's the man 00:17:18.940 --> 00:17:20.829 who mistook his wife for a hat. 00:17:20.829 --> 00:17:23.810 So he has bigger problems in vision than simply faces. 00:17:23.810 --> 00:17:25.500 But faces are very impressive. 00:17:25.500 --> 00:17:28.120 He fails to recognize his students by their face. 00:17:28.120 --> 00:17:30.020 But he can recognize them by their voice, 00:17:30.020 --> 00:17:31.450 modality-specific. 00:17:31.450 --> 00:17:34.080 His general vision is OK. 00:17:34.080 --> 00:17:37.840 When Oliver Sacks visited him in his house, he tries to 00:17:37.840 --> 00:17:40.950 reach out his hand and took hold of his wife's head, tried 00:17:40.950 --> 00:17:42.585 to lift it off to put it on. 00:17:42.585 --> 00:17:46.880 He had apparently mistaken his wife for a hat. 00:17:46.880 --> 00:17:49.440 His wife looked as if she was used to such things. 00:17:49.440 --> 00:17:51.260 You can see the head and the hat, they're kind of close. 00:17:51.260 --> 00:17:53.560 But not if you have typical vision. 00:17:53.560 --> 00:17:56.490 He might pat the head of water hydrants and parking meters 00:17:56.490 --> 00:17:59.740 mistaking them for the heads of children. 00:17:59.740 --> 00:18:01.190 There's a little bit of logic. 00:18:01.190 --> 00:18:03.315 But it's pretty wrong what he sees. 00:18:03.315 --> 00:18:04.765 And it's pretty meaningless to him. 00:18:07.380 --> 00:18:09.850 So let me show you a film of an example. 00:18:09.850 --> 00:18:11.100 You saw one last time. 00:18:13.810 --> 00:18:14.750 So let me say a word about this. 00:18:14.750 --> 00:18:16.920 Imagine that if you couldn't recognize people 00:18:16.920 --> 00:18:17.770 as you walked up. 00:18:17.770 --> 00:18:20.960 So much of how we recognize people-- we don't think about 00:18:20.960 --> 00:18:22.930 this, because we instantly, easily recognize 00:18:22.930 --> 00:18:24.050 those we know well-- 00:18:24.050 --> 00:18:26.040 is by their faces. 00:18:26.040 --> 00:18:28.390 So I want to say a couple of things. 00:18:28.390 --> 00:18:29.990 Usually there's posterior cortical lesions 00:18:29.990 --> 00:18:31.710 like in this woman. 00:18:31.710 --> 00:18:34.800 I knew one man who was a Unitarian minister, who I 00:18:34.800 --> 00:18:36.760 worked with, actually, a couple blocks away here, 00:18:36.760 --> 00:18:39.120 He went up to Dartmouth for the winter carnival. 00:18:39.120 --> 00:18:40.960 He came back in a small Volkswagen. 00:18:40.960 --> 00:18:41.870 It turned over turned over on the ice. 00:18:41.870 --> 00:18:45.505 He had a huge brain injury and became prosopagnosic. 00:18:45.505 --> 00:18:47.900 He could only recognize his wife by asking her to wear a 00:18:47.900 --> 00:18:49.700 yellow bow in her hair. 00:18:49.700 --> 00:18:50.660 Because otherwise he couldn't pick her 00:18:50.660 --> 00:18:52.370 out from other people. 00:18:52.370 --> 00:18:55.740 When he went down the street and passed his brother, he 00:18:55.740 --> 00:18:57.410 completely failed to recognize him. 00:18:57.410 --> 00:18:58.510 Then the brother spoke. 00:18:58.510 --> 00:18:59.420 Then he recognized him. 00:18:59.420 --> 00:19:01.740 And he said-- and this was his subjective experience-- 00:19:01.740 --> 00:19:03.400 because you wonder what do these people 00:19:03.400 --> 00:19:05.670 feel like they see. 00:19:05.670 --> 00:19:08.810 He said that what it felt like for his brother was, do you 00:19:08.810 --> 00:19:11.340 when somebody has some bad handwriting, and you can't 00:19:11.340 --> 00:19:12.480 make it out at all? 00:19:12.480 --> 00:19:13.830 And then somebody tells you what it is. 00:19:13.830 --> 00:19:15.280 And you go, oh yes. 00:19:15.280 --> 00:19:16.260 That's that word. 00:19:16.260 --> 00:19:17.730 Any now you see it. 00:19:17.730 --> 00:19:20.120 He said, that's what it felt like as he heard his brother's 00:19:20.120 --> 00:19:22.990 voice and realized it was his brother. 00:19:22.990 --> 00:19:24.320 It's hard to know how to relate these things. 00:19:24.320 --> 00:19:27.180 But the ability to recognize a person is completely wiped out 00:19:27.180 --> 00:19:28.610 of these individuals. 00:19:28.610 --> 00:19:32.270 In the last six or seven years, something else has been 00:19:32.270 --> 00:19:32.570 discovered. 00:19:32.570 --> 00:19:34.570 Now let me tell you a word about this. 00:19:34.570 --> 00:19:37.560 Instead of people with acute lesions that they got because 00:19:37.560 --> 00:19:38.810 of a brain injury. 00:19:38.810 --> 00:19:42.440 It turns out there's a couple percent of our population 00:19:42.440 --> 00:19:45.590 that's really bad at recognizing faces, not the 00:19:45.590 --> 00:19:47.630 occasional social embarrassment that many of us 00:19:47.630 --> 00:19:50.880 have when we see somebody, we know we should know them, but 00:19:50.880 --> 00:19:53.560 they're really, really, really bad. 00:19:53.560 --> 00:19:56.250 There's websites you can go to that let you test yourself. 00:19:56.250 --> 00:19:58.570 Because researchers want you to work with them if you're 00:19:58.570 --> 00:19:59.800 one of them. 00:19:59.800 --> 00:20:02.500 It's about 1% of the population. 00:20:02.500 --> 00:20:05.200 They're really, really, really bad. 00:20:05.200 --> 00:20:06.480 There was one woman described as, she says, 00:20:06.480 --> 00:20:07.690 they can't watch movies. 00:20:07.690 --> 00:20:09.070 Because all the characters look pretty 00:20:09.070 --> 00:20:12.320 much the same to them. 00:20:12.320 --> 00:20:13.570 You can imagine that. 00:20:16.050 --> 00:20:19.600 One parent who has this problem, really terrible at 00:20:19.600 --> 00:20:22.480 faces by formal testing, says that when her kid comes out of 00:20:22.480 --> 00:20:26.800 school, her own kid, if he is not wearing the clothes that 00:20:26.800 --> 00:20:29.270 she knows he's wearing, she can't pick him out from the 00:20:29.270 --> 00:20:31.300 other children very easily. 00:20:31.300 --> 00:20:33.390 And these are not people with big brain injuries. 00:20:33.390 --> 00:20:35.820 These are people who have some unusual difficulty in 00:20:35.820 --> 00:20:36.870 recognizing faces. 00:20:36.870 --> 00:20:40.440 So in a classroom this size, there easily 00:20:40.440 --> 00:20:43.200 could be one of you. 00:20:43.200 --> 00:20:44.640 We don't understand what that is. 00:20:44.640 --> 00:20:46.740 It's not a brain injury. 00:20:46.740 --> 00:20:49.490 Just like some of us can't carry a tune, some individuals 00:20:49.490 --> 00:20:54.390 are really terrible at recognizing faces, really bad. 00:20:54.390 --> 00:20:56.560 So there's a lot of research into that to understand what 00:20:56.560 --> 00:20:57.740 that reflects. 00:20:57.740 --> 00:20:59.870 So let me tell you what we do understand about the neural 00:20:59.870 --> 00:21:02.680 circuitry in the typical brain for recognizing a face of a 00:21:02.680 --> 00:21:04.820 loved one, a person that you care about. 00:21:04.820 --> 00:21:06.960 So this is the fusiform gyrus. 00:21:06.960 --> 00:21:09.060 It's a structure in the back of the brain that extends from 00:21:09.060 --> 00:21:11.170 the occipital into the temporal lobes. 00:21:11.170 --> 00:21:13.620 And that's an anatomical description of this region. 00:21:13.620 --> 00:21:18.540 Within that region, there's a functional area that seems 00:21:18.540 --> 00:21:20.660 very important for face perception. 00:21:20.660 --> 00:21:22.930 And Nancy Kanwisher, who's in our department, pretty much 00:21:22.930 --> 00:21:25.900 discovered this specific functional area in the typical 00:21:25.900 --> 00:21:27.250 human brain. 00:21:27.250 --> 00:21:30.340 And so she did experiments where she would present things 00:21:30.340 --> 00:21:32.110 like faces or objects. 00:21:35.700 --> 00:21:37.870 In this picture, left is right, and right is left. 00:21:37.870 --> 00:21:40.270 There's a spot in the fusiform cortex that has 00:21:40.270 --> 00:21:41.580 this following property. 00:21:41.580 --> 00:21:42.280 Here's faces. 00:21:42.280 --> 00:21:43.070 That turns on. 00:21:43.070 --> 00:21:45.065 Here's objects which have similar properties. 00:21:45.065 --> 00:21:47.530 It has a lot of visual information like a face. 00:21:47.530 --> 00:21:48.740 But it's not a face. 00:21:48.740 --> 00:21:51.420 It's part of the brain region not so interested, faces, 00:21:51.420 --> 00:21:53.310 objects, faces, objects. 00:21:53.310 --> 00:21:54.970 So whenever faces come on-- 00:21:54.970 --> 00:21:56.860 this is, by our understanding-- the first part 00:21:56.860 --> 00:21:59.630 of your brain that says, I'm looking at a face. 00:21:59.630 --> 00:22:02.130 Up until then, it's just treated like other stuff. 00:22:02.130 --> 00:22:04.710 This is the first part of your brain that recognizes, I'm 00:22:04.710 --> 00:22:05.870 looking at a face. 00:22:05.870 --> 00:22:08.890 I'm starting to identify who I'm looking at and what 00:22:08.890 --> 00:22:11.950 feelings they might have by their expression. 00:22:11.950 --> 00:22:14.970 And Nancy and her colleagues did all kinds of very clever 00:22:14.970 --> 00:22:18.450 experiments to show the properties of this. 00:22:18.450 --> 00:22:19.450 Let me pick one. 00:22:19.450 --> 00:22:21.970 You could say, well, it's not about faces. 00:22:21.970 --> 00:22:23.420 But faces are about humans. 00:22:23.420 --> 00:22:25.550 Maybe it's a part of the brain that tells you when there's a 00:22:25.550 --> 00:22:26.970 human around you. 00:22:26.970 --> 00:22:29.870 So they compared faces versus hands. 00:22:29.870 --> 00:22:30.670 Here's hands. 00:22:30.670 --> 00:22:32.060 This part of the brain is not that interested. 00:22:32.060 --> 00:22:33.900 Faces, hands, faces, hands. 00:22:33.900 --> 00:22:35.770 You see every time it moves to faces, this part of the brain 00:22:35.770 --> 00:22:37.280 gets very strongly engaged. 00:22:37.280 --> 00:22:42.330 It's very much about faces by many research studies. 00:22:42.330 --> 00:22:44.030 So let me tell you a little bit about what we understand 00:22:44.030 --> 00:22:45.750 about faces in terms of development 00:22:45.750 --> 00:22:46.430 and things like that. 00:22:46.430 --> 00:22:48.920 Because faces are such a big part of our lives from the 00:22:48.920 --> 00:22:50.420 first few moments we're born. 00:22:50.420 --> 00:22:55.870 In fact, a colleague of mine, Pawan Sinha, did a kind of a 00:22:55.870 --> 00:22:58.760 biographical research study that was on the front page of 00:22:58.760 --> 00:23:02.030 The New York Times and earned MIT faculty the continuing 00:23:02.030 --> 00:23:03.560 names of being Frankenstein faculty. 00:23:03.560 --> 00:23:05.240 There was a number of faculty. 00:23:05.240 --> 00:23:08.400 And what he did, kind of very cleverly, was he put on his 00:23:08.400 --> 00:23:12.360 newborn infant's head a little camera. 00:23:12.360 --> 00:23:14.150 And he said, if I leave it on there and 00:23:14.150 --> 00:23:15.240 record it all the time-- 00:23:15.240 --> 00:23:16.950 and apparently there was some debate with his wife whether 00:23:16.950 --> 00:23:17.770 he was allowed to do this. 00:23:17.770 --> 00:23:18.410 But they checked it out. 00:23:18.410 --> 00:23:21.640 It seemed OK by the pediatrician. 00:23:21.640 --> 00:23:24.020 He said, if I have the camera on the infant's head, I can 00:23:24.020 --> 00:23:27.050 see what the infant's experience is like moment to 00:23:27.050 --> 00:23:30.180 moment in the first months of its life. 00:23:30.180 --> 00:23:34.350 And I can also play with the video so that it has, roughly 00:23:34.350 --> 00:23:39.540 speaking, the properties of the infant's visual system, 00:23:39.540 --> 00:23:42.955 which is it can't see very far after its birth. 00:23:42.955 --> 00:23:45.070 They can only see very close by, and not that well. 00:23:45.070 --> 00:23:46.333 Over the next several months-- we'll talk about 00:23:46.333 --> 00:23:46.910 this later in class-- 00:23:46.910 --> 00:23:49.860 he gets better and better at seeing at a distance. 00:23:49.860 --> 00:23:53.230 So here's the infant sitting in his or her crib. 00:23:53.230 --> 00:23:56.000 And this video makes incredibly clear, beautifully 00:23:56.000 --> 00:23:58.900 and fascinatingly clear, something that I never thought 00:23:58.900 --> 00:24:02.140 of until Pawan did this study, this examination. 00:24:02.140 --> 00:24:04.800 So the infant sitting there, it can't move very much. 00:24:04.800 --> 00:24:07.480 It can't go very many places as a newborn infant. 00:24:07.480 --> 00:24:08.410 So what does it see? 00:24:08.410 --> 00:24:12.630 What gets close enough to it to be visible to the infant? 00:24:12.630 --> 00:24:14.430 People's faces. 00:24:14.430 --> 00:24:16.825 Because all the other cute things in the nursery, all the 00:24:16.825 --> 00:24:19.070 other things that are there, they are too far or too blurry 00:24:19.070 --> 00:24:21.410 for the infant to process almost at all. 00:24:21.410 --> 00:24:24.290 Almost the only thing that happens is the parent, the 00:24:24.290 --> 00:24:27.430 grandparent, the siblings, the friends that come over and go, 00:24:27.430 --> 00:24:28.610 what a cute baby. 00:24:28.610 --> 00:24:29.870 Baby, baby, baby, baby. 00:24:29.870 --> 00:24:32.190 The face comes in. 00:24:32.190 --> 00:24:34.430 The person's done, gone. 00:24:34.430 --> 00:24:36.350 Now you're just sitting in a world of blur. 00:24:36.350 --> 00:24:38.790 Here comes another face. 00:24:38.790 --> 00:24:41.090 So besides certain issues related to perhaps the 00:24:41.090 --> 00:24:43.430 feeding, the only thing the infant sees are 00:24:43.430 --> 00:24:45.660 faces all the time. 00:24:45.660 --> 00:24:49.460 So it's a very important social cue of who it's 00:24:49.460 --> 00:24:50.600 interacting with and what's out there. 00:24:50.600 --> 00:24:52.680 And it's almost the only one available to it. 00:24:52.680 --> 00:24:56.330 So psychologists have known for some time that if you show 00:24:56.330 --> 00:24:59.850 a very young infant a face versus something like an 00:24:59.850 --> 00:25:02.430 object, like a car or anything like that, they're much more 00:25:02.430 --> 00:25:04.980 interested in faces if you put them next to each other where 00:25:04.980 --> 00:25:06.440 the infant can see them. 00:25:06.440 --> 00:25:08.330 And they've been saying, well, is the brain 00:25:08.330 --> 00:25:10.130 born to process faces? 00:25:10.130 --> 00:25:10.770 And it might be. 00:25:10.770 --> 00:25:12.100 And I'll show you evidence to suggest in some 00:25:12.100 --> 00:25:13.510 general sense it is. 00:25:13.510 --> 00:25:16.290 What is that infant's brain drawn to? 00:25:16.290 --> 00:25:19.100 What does it find fascinating to learn about in the world? 00:25:19.100 --> 00:25:22.370 And so they notice that one thing about a face is in terms 00:25:22.370 --> 00:25:27.720 of features, eyes, nose, mouth, top-heavy. 00:25:27.720 --> 00:25:29.800 Because we have two eyes, and everything else is one and 00:25:29.800 --> 00:25:31.470 one, the nose and the mouth. 00:25:31.470 --> 00:25:33.750 So here you can move the features like this. 00:25:33.750 --> 00:25:36.020 And it turns out not only are infants more interested in 00:25:36.020 --> 00:25:38.300 this kind of face than this-- and they know that because 00:25:38.300 --> 00:25:40.390 they'll put the two up, and they'll measure how long the 00:25:40.390 --> 00:25:43.760 infant looks at one versus the other, which is interesting. 00:25:43.760 --> 00:25:44.730 And the infant picks this one. 00:25:44.730 --> 00:25:45.590 But get a load of this? 00:25:45.590 --> 00:25:48.540 The infant also picks this one versus this, this one versus 00:25:48.540 --> 00:25:50.200 this, and this one versus this. 00:25:50.200 --> 00:25:52.710 Now these look very little like a face. 00:25:52.710 --> 00:25:55.490 But they're top-heavy. 00:25:55.490 --> 00:25:59.500 It's as if maybe the infant's brain to start with, maybe, 00:25:59.500 --> 00:26:02.380 looks for some interesting, top-heavy things and that 00:26:02.380 --> 00:26:04.640 pulls it into the world of faces. 00:26:04.640 --> 00:26:06.500 Here's some more experiments like that. 00:26:06.500 --> 00:26:12.040 So here's an upside down, right-side up. 00:26:12.040 --> 00:26:13.960 Baby looks more at this kind of face. 00:26:13.960 --> 00:26:14.240 OK. 00:26:14.240 --> 00:26:15.790 You could say, well, that's a normal face. 00:26:15.790 --> 00:26:17.840 But it's also top-heavy. 00:26:17.840 --> 00:26:21.900 Then they'd make these kind of scary-looking faces. 00:26:21.900 --> 00:26:24.860 And now the baby, even though these are nothing like a face 00:26:24.860 --> 00:26:28.540 the baby ever sees, it still likes this one 00:26:28.540 --> 00:26:31.260 because it's top-heavy. 00:26:31.260 --> 00:26:32.740 Now how about this one? 00:26:32.740 --> 00:26:33.930 This is like a face they see. 00:26:33.930 --> 00:26:36.110 This is a really weird face. 00:26:36.110 --> 00:26:36.490 Right? 00:26:36.490 --> 00:26:38.020 They'll never see a face like this except in this 00:26:38.020 --> 00:26:39.160 experiment. 00:26:39.160 --> 00:26:40.150 Top-heavy. 00:26:40.150 --> 00:26:41.180 Top-heavy. 00:26:41.180 --> 00:26:43.700 And now the infant looks at both of them with equal 00:26:43.700 --> 00:26:45.970 interest and delight. 00:26:45.970 --> 00:26:49.860 So that's a very clever experiment to suggest that the 00:26:49.860 --> 00:26:53.500 infant's mind is looking for top-heavy things. 00:26:53.500 --> 00:26:55.040 And you could say, is it really top-heavy? 00:26:55.040 --> 00:26:58.260 Or Is that what the infant's mind and brain can look for? 00:26:58.260 --> 00:26:59.480 And it goes with faces. 00:26:59.480 --> 00:27:01.830 And evolution picked that. 00:27:01.830 --> 00:27:03.850 It's hard to know how to think about these things. 00:27:03.850 --> 00:27:06.500 But it looks like the top-heaviness draws an infant 00:27:06.500 --> 00:27:08.960 to be fascinated by faces. 00:27:08.960 --> 00:27:12.880 And luckily, you don't get many faces like this to 00:27:12.880 --> 00:27:16.920 confuse you in the real world. 00:27:16.920 --> 00:27:18.120 Another thing that people have studied a lot 00:27:18.120 --> 00:27:21.590 about faces is this. 00:27:21.590 --> 00:27:23.040 They use the word configural. 00:27:23.040 --> 00:27:25.230 The relations among the parts are more important than the 00:27:25.230 --> 00:27:26.230 parts themselves. 00:27:26.230 --> 00:27:27.540 So I need a volunteer in their seat. 00:27:27.540 --> 00:27:29.850 And this is going to be really easy if you know the alphabet. 00:27:32.380 --> 00:27:35.270 You have to put up your hand and help me out. 00:27:35.270 --> 00:27:35.490 OK. 00:27:35.490 --> 00:27:36.240 Thank you very much. 00:27:36.240 --> 00:27:38.410 I'm going to describe to you a letter by its features. 00:27:38.410 --> 00:27:39.190 OK? 00:27:39.190 --> 00:27:41.470 It has a big line at the top. 00:27:41.470 --> 00:27:42.510 And in the middle, there's a line that 00:27:42.510 --> 00:27:44.150 goes down to the bottom. 00:27:44.150 --> 00:27:45.140 What's the letter? 00:27:45.140 --> 00:27:45.610 AUDIENCE: T. 00:27:45.610 --> 00:27:45.980 PROFESSOR: Awesome. 00:27:45.980 --> 00:27:46.430 OK. 00:27:46.430 --> 00:27:47.490 Featural description. 00:27:47.490 --> 00:27:50.600 Now I'm going to describe to you a super famous movie star. 00:27:50.600 --> 00:27:53.790 And this person has two eyes to the left and to the right, 00:27:53.790 --> 00:27:56.150 a nose right below that, and a mouth right below that. 00:27:56.150 --> 00:27:59.450 And who is it? 00:27:59.450 --> 00:28:02.290 Angelina Jolie. 00:28:02.290 --> 00:28:03.390 So what's my point here? 00:28:03.390 --> 00:28:06.210 It's the stuff that helps us in many things, like the 00:28:06.210 --> 00:28:06.770 letters-- thank you. 00:28:06.770 --> 00:28:09.240 That was excellent. 00:28:09.240 --> 00:28:11.010 We can describe those by the parts. 00:28:11.010 --> 00:28:12.560 And the parts pretty much define the whole. 00:28:12.560 --> 00:28:13.640 That's not true for faces. 00:28:13.640 --> 00:28:15.930 It really is the precise relations between eyes, and 00:28:15.930 --> 00:28:17.210 nose, and mouth that tell us. 00:28:17.210 --> 00:28:20.120 And there's an experiment that shows this in a very empirical 00:28:20.120 --> 00:28:21.030 direct way. 00:28:21.030 --> 00:28:22.870 So they would show people a face like this with a 00:28:22.870 --> 00:28:25.420 particular nose or a house like this with 00:28:25.420 --> 00:28:27.440 a particular door. 00:28:27.440 --> 00:28:30.000 And then they would test your memory for that nose or that 00:28:30.000 --> 00:28:35.910 door by itself as features or with the whole face or a whole 00:28:35.910 --> 00:28:37.840 house present. 00:28:37.840 --> 00:28:40.920 And here's what happens for people's performance. 00:28:40.920 --> 00:28:44.570 The nose by itself, the door by itself, the nose when you 00:28:44.570 --> 00:28:46.370 see the whole picture, which could be his nose. 00:28:46.370 --> 00:28:47.650 It could be another nose. 00:28:47.650 --> 00:28:48.290 Here's the door. 00:28:48.290 --> 00:28:50.310 It could be that door or a different door. 00:28:50.310 --> 00:28:52.520 And here's what happens in performance. 00:28:52.520 --> 00:28:56.560 If it's houses, people are good for doors, about the same 00:28:56.560 --> 00:28:59.880 whether they've identified the door by itself or the door in 00:28:59.880 --> 00:29:01.980 the context of the house. 00:29:01.980 --> 00:29:04.540 If it's noses, they were a lot better off 00:29:04.540 --> 00:29:06.100 seeing the entire face. 00:29:06.100 --> 00:29:10.080 It's as if how we analyzed even the parts of the face are 00:29:10.080 --> 00:29:13.110 really integrated immediately into the other 00:29:13.110 --> 00:29:13.890 aspects of the face. 00:29:13.890 --> 00:29:15.250 They don't stand alone. 00:29:15.250 --> 00:29:19.230 They're a part of a context all interacting together. 00:29:19.230 --> 00:29:22.080 Now here's something pretty striking and interesting. 00:29:22.080 --> 00:29:24.430 And we'll talk about some social implications of this at 00:29:24.430 --> 00:29:27.230 the end of the lecture. 00:29:27.230 --> 00:29:28.920 You can't ask infants many things. 00:29:28.920 --> 00:29:32.070 But you can record their behavior and learn some things 00:29:32.070 --> 00:29:34.360 about what their minds are representing and thinking. 00:29:34.360 --> 00:29:37.480 And here's how they test an infant at say six months of 00:29:37.480 --> 00:29:41.180 age, can't talk, can't walk, can't be instructed to push 00:29:41.180 --> 00:29:43.130 buttons or fill out surveys. 00:29:43.130 --> 00:29:45.720 How do they get inside the mind of what an infant knows? 00:29:45.720 --> 00:29:46.960 What they'll do is they'll show a face. 00:29:46.960 --> 00:29:51.080 And pretend they show this face all by itself. 00:29:51.080 --> 00:29:52.680 Infant looks for a little bit. 00:29:52.680 --> 00:29:55.240 Face disappears, and then they see the face they just saw and 00:29:55.240 --> 00:29:56.910 a new face. 00:29:56.910 --> 00:29:59.940 And infants who saw this face a few moments ago will spend 00:29:59.940 --> 00:30:04.580 more time looking at the new face than the old face. 00:30:04.580 --> 00:30:06.690 You can track where their eyes are. 00:30:06.690 --> 00:30:09.140 And that's the evidence they remember the face they saw 00:30:09.140 --> 00:30:11.580 before, because they selectively spend more time on 00:30:11.580 --> 00:30:12.830 the new face. 00:30:12.830 --> 00:30:15.230 And also they're hungry to look at the new face. 00:30:15.230 --> 00:30:17.350 I've seen this face, been there, done that. 00:30:17.350 --> 00:30:20.310 New face, check out this person. 00:30:20.310 --> 00:30:22.700 If you test them at six months, they'll have a 00:30:22.700 --> 00:30:26.360 preference for the new face. 00:30:26.360 --> 00:30:29.810 But if you show them two different monkeys-- 00:30:29.810 --> 00:30:32.110 and this might feel hard for you to tell these apart-- 00:30:32.110 --> 00:30:34.895 if you show them two different monkeys, they'll behave the 00:30:34.895 --> 00:30:38.440 same with monkey faces as they do with human faces. 00:30:38.440 --> 00:30:41.720 They'll prefer the novel face, which shows you they remember 00:30:41.720 --> 00:30:44.710 what face they saw before and want to look at the new face. 00:30:44.710 --> 00:30:49.330 And at six months, it's the same for humans and monkeys. 00:30:49.330 --> 00:30:51.070 And don't forget, most of these people are interacting a 00:30:51.070 --> 00:30:53.600 lot with adults, and siblings, and caretakers. 00:30:53.600 --> 00:30:57.330 Not many of them are hanging out with monkeys. 00:30:57.330 --> 00:31:01.520 They start to get much more accurate for human faces. 00:31:01.520 --> 00:31:04.420 The experience they have with human faces starts to make 00:31:04.420 --> 00:31:05.920 them much better that. 00:31:05.920 --> 00:31:08.490 At birth, faces from one species 00:31:08.490 --> 00:31:09.700 are as good as another. 00:31:09.700 --> 00:31:12.240 But with practice and experience, they become human 00:31:12.240 --> 00:31:14.030 face specialists. 00:31:14.030 --> 00:31:16.130 And they become much better at that. 00:31:16.130 --> 00:31:19.810 So it's not in our genes to be awesome at human faces. 00:31:19.810 --> 00:31:21.430 But there's something about faces. 00:31:21.430 --> 00:31:24.790 And then a lot depends on what we see. 00:31:24.790 --> 00:31:27.140 And we grow that part of our mind and brain. 00:31:27.140 --> 00:31:29.070 So here's a remarkable experiment, that you couldn't 00:31:29.070 --> 00:31:32.860 do with people, that was done with infant monkeys. 00:31:32.860 --> 00:31:36.030 These monkeys, after they were born, were given no exposure 00:31:36.030 --> 00:31:38.890 to faces, depending on the monkey, for six to 24 months. 00:31:38.890 --> 00:31:41.120 That's not quite completely true. 00:31:41.120 --> 00:31:43.430 Because at their birth, they saw some faces. 00:31:43.430 --> 00:31:45.090 So they couldn't start this experiment at the 00:31:45.090 --> 00:31:45.980 first moment of birth. 00:31:45.980 --> 00:31:49.650 But as soon as they could from birth, for six to 24 months. 00:31:49.650 --> 00:31:53.350 So when they were being fed, this is what they saw. 00:31:53.350 --> 00:31:55.010 They were given an interesting environment 00:31:55.010 --> 00:31:56.550 to see lots of stuff. 00:31:56.550 --> 00:31:57.730 And they would live in something like this. 00:31:57.730 --> 00:31:59.660 So they could not see another monkey. 00:31:59.660 --> 00:32:00.610 They could not see a human. 00:32:00.610 --> 00:32:02.710 They never saw a face except for the 00:32:02.710 --> 00:32:03.960 first moments of birth. 00:32:07.640 --> 00:32:11.790 Before they saw any living face on a monkey or a human, 00:32:11.790 --> 00:32:13.680 they would do these kinds of experiments that you just 00:32:13.680 --> 00:32:14.590 heard with infants. 00:32:14.590 --> 00:32:18.030 And they would show that these monkeys would preferentially 00:32:18.030 --> 00:32:21.040 look at faces, both human faces and monkeys. 00:32:21.040 --> 00:32:23.110 And they had no preference between them. 00:32:23.110 --> 00:32:25.830 They would always go for a face compared to an object, a 00:32:25.830 --> 00:32:28.120 monkey face or a human face. 00:32:28.120 --> 00:32:29.900 And they could do these kinds of discrimination. 00:32:29.900 --> 00:32:32.730 The first moment before they had ever-- except for whatever 00:32:32.730 --> 00:32:35.020 happens right a birth-- seen one. 00:32:35.020 --> 00:32:38.640 So they never practiced on anything. 00:32:38.640 --> 00:32:40.540 Because they had not been allowed to see a face. 00:32:40.540 --> 00:32:44.480 But the first moment before they saw any living face, they 00:32:44.480 --> 00:32:48.040 already had this preference for faces for both humans and 00:32:48.040 --> 00:32:52.230 monkeys, as if it's in our genes to be drawn to faces. 00:32:52.230 --> 00:32:55.040 And what the mechanism is, the top-heavy, something else, we 00:32:55.040 --> 00:32:56.040 don't quite know. 00:32:56.040 --> 00:32:58.440 But it's in our brain to go for faces. 00:32:58.440 --> 00:33:00.220 They're so important for us. 00:33:00.220 --> 00:33:03.410 Then some monkeys hung around people. 00:33:03.410 --> 00:33:06.180 And some monkeys hung around monkeys. 00:33:06.180 --> 00:33:09.650 And what happened is really quite striking. 00:33:09.650 --> 00:33:13.440 They got better at the species they hung around. 00:33:13.440 --> 00:33:16.320 So if you did these kinds of tests, the monkeys who hung 00:33:16.320 --> 00:33:18.970 around monkeys got better and better at monkeys. 00:33:18.970 --> 00:33:20.830 And the monkeys that hung around people got better and 00:33:20.830 --> 00:33:22.740 better at people. 00:33:22.740 --> 00:33:24.150 So what does that mean? 00:33:24.150 --> 00:33:26.440 That means it looks like there's a genetic preparation. 00:33:26.440 --> 00:33:29.080 The first face that they see with the slight asterisk of 00:33:29.080 --> 00:33:31.700 the moment of birth, they are already preferring faces. 00:33:31.700 --> 00:33:33.800 The very first one they see, even though they've gone six 00:33:33.800 --> 00:33:38.020 months to two years without seeing any face at all. 00:33:38.020 --> 00:33:40.390 And then they get better selectively on the species 00:33:40.390 --> 00:33:41.900 they're exposed to. 00:33:41.900 --> 00:33:44.200 So there's a genetic preparation and then kind of a 00:33:44.200 --> 00:33:46.940 sensitive period where you build up a representation of 00:33:46.940 --> 00:33:49.980 the species that you're living with. 00:33:49.980 --> 00:33:54.840 So let me slide there for a moment to now writing. 00:33:54.840 --> 00:33:56.830 As long as there's been mammals, as long as there's 00:33:56.830 --> 00:34:00.535 been people, we've been born to things around us with faces 00:34:00.535 --> 00:34:03.960 and interacted with people who have faces. 00:34:03.960 --> 00:34:05.960 So that's deep in our evolutionary history. 00:34:05.960 --> 00:34:07.890 Not deep in our evolutionary history 00:34:07.890 --> 00:34:09.730 is writing and reading. 00:34:09.730 --> 00:34:11.909 The first visual language of any kind is 00:34:11.909 --> 00:34:14.620 about 4,000 years ago. 00:34:14.620 --> 00:34:17.409 Not until the Gutenberg Bible-- 00:34:17.409 --> 00:34:21.159 and that's about 600 years ago-- 00:34:21.159 --> 00:34:23.739 did large numbers of people read. 00:34:23.739 --> 00:34:26.860 So unlike faces and objects which have been around 00:34:26.860 --> 00:34:31.510 forever, not only for us, but for other species, writing and 00:34:31.510 --> 00:34:34.080 reading have been around only for a few hundred years. 00:34:34.080 --> 00:34:36.320 Our brains are not evolved to be reading brains. 00:34:36.320 --> 00:34:40.880 It's just an unbelievably powerful cultural invention. 00:34:40.880 --> 00:34:42.610 And people can read fast. 00:34:42.610 --> 00:34:44.550 A typical reader can do this. 00:34:44.550 --> 00:34:47.199 This is kind of amazing. 00:34:47.199 --> 00:34:48.370 Most of us know somewhere between 00:34:48.370 --> 00:34:51.580 50,000 and 100,000 words. 00:34:51.580 --> 00:34:52.610 We don't know all of them well. 00:34:52.610 --> 00:34:53.850 We can't spell all of them correctly. 00:34:53.850 --> 00:34:55.690 But we kind of can get them if we see them. 00:34:55.690 --> 00:34:59.750 And if we show you one word in 50,000ths of a second, you can 00:34:59.750 --> 00:35:02.210 recognize which word you saw. 00:35:02.210 --> 00:35:03.720 It's kind of amazing. 00:35:03.720 --> 00:35:06.830 People read about 200 to 250 words per minute, a typical 00:35:06.830 --> 00:35:10.000 reader cruising along when they're focused. 00:35:10.000 --> 00:35:11.980 These things can be measured relatively simply. 00:35:11.980 --> 00:35:13.020 Here's one that's a little trickier. 00:35:13.020 --> 00:35:13.560 But let me tell you. 00:35:13.560 --> 00:35:15.480 Again, it shows you how experiments can tell us 00:35:15.480 --> 00:35:16.960 something we could not have guessed without the 00:35:16.960 --> 00:35:20.210 experiment, about how you read every moment you've read 00:35:20.210 --> 00:35:21.730 throughout your life. 00:35:21.730 --> 00:35:24.450 So I'm going to tell you now that you read about 12 00:35:24.450 --> 00:35:25.470 letters at a time. 00:35:25.470 --> 00:35:26.680 And then you move your eyes. 00:35:26.680 --> 00:35:29.320 Whatever you're reading, a book, on the computer, you'll 00:35:29.320 --> 00:35:30.970 read about 12 letters. 00:35:30.970 --> 00:35:33.300 That's where you're fixated. 00:35:33.300 --> 00:35:36.820 Those will only be visible to you, and then you'll move your 00:35:36.820 --> 00:35:40.890 eyes to get the next set of letters you need to read. 00:35:40.890 --> 00:35:42.260 Now you go, no. 00:35:42.260 --> 00:35:44.030 There's text there. 00:35:44.030 --> 00:35:45.320 I'll give you, I move my eyes. 00:35:45.320 --> 00:35:48.660 But what's really happening, let me show you how blind you 00:35:48.660 --> 00:35:52.080 are to everything but 12 letters at a time. 00:35:52.080 --> 00:35:54.590 So here's the experiment from McConkie & Raynor. 00:35:54.590 --> 00:35:56.390 And many people have found this since. 00:35:56.390 --> 00:35:58.200 They tracked people's eye movements. 00:35:58.200 --> 00:35:59.620 You can have a machine that tracks where your eyes are 00:35:59.620 --> 00:36:01.890 fixated, where you're looking. 00:36:01.890 --> 00:36:04.970 Every time you moved, what they did is they took the text 00:36:04.970 --> 00:36:08.640 that was written across a monitor, they kept about 12 00:36:08.640 --> 00:36:09.900 letters where you're looking. 00:36:09.900 --> 00:36:13.690 And they made everything else on the monitor x's. 00:36:13.690 --> 00:36:14.460 You don't know this. 00:36:14.460 --> 00:36:16.140 You're just reading. 00:36:16.140 --> 00:36:20.460 So you're reading "people of." This is where your eyes are. 00:36:20.460 --> 00:36:22.010 The computer makes everything else an x. 00:36:22.010 --> 00:36:23.870 You move your eyes. 00:36:23.870 --> 00:36:24.910 Now this becomes x's. 00:36:24.910 --> 00:36:26.030 And these are x's. 00:36:26.030 --> 00:36:27.800 You move your eye. 00:36:27.800 --> 00:36:28.990 These become x's. 00:36:28.990 --> 00:36:30.210 You move your eyes. 00:36:30.210 --> 00:36:31.015 These become x's. 00:36:31.015 --> 00:36:32.260 Does hat make sense? 00:36:32.260 --> 00:36:34.970 Every time you move, where you land, they give you the words 00:36:34.970 --> 00:36:35.740 and letters. 00:36:35.740 --> 00:36:38.400 But everything to the left and right are all x's. 00:36:38.400 --> 00:36:42.980 And the astounding thing is nobody ever says hey, why are 00:36:42.980 --> 00:36:45.540 there all the x's. 00:36:45.540 --> 00:36:48.570 Because when you're reading, unbeknownst to you, you only 00:36:48.570 --> 00:36:52.300 see with good acuity 12 letters at a time. 00:36:52.300 --> 00:36:55.350 And everything else, you barely notice it's there. 00:36:55.350 --> 00:36:57.160 You notice something is there. 00:36:57.160 --> 00:36:59.410 If there's nothing there, you would notice it. 00:36:59.410 --> 00:37:03.190 But your mind is not really seeing it at all. 00:37:03.190 --> 00:37:06.700 And so people have tried to represent this. 00:37:06.700 --> 00:37:09.320 This, when you read, is something like this. 00:37:09.320 --> 00:37:11.780 Where you look, in your fovea, or your high acuity, you see 00:37:11.780 --> 00:37:13.030 about 12 letters. 00:37:13.030 --> 00:37:16.320 Everything else is like this. 00:37:16.320 --> 00:37:19.670 And that's why if I flip it to x's, you don't even notice. 00:37:19.670 --> 00:37:21.730 Because it's all pretty crummy how you see it. 00:37:21.730 --> 00:37:22.885 You notice something is there. 00:37:22.885 --> 00:37:26.420 But it's pretty crummy. 00:37:26.420 --> 00:37:27.560 You can say, I don't believe it. 00:37:27.560 --> 00:37:28.520 But people have done this experiment 00:37:28.520 --> 00:37:29.530 over and over again. 00:37:29.530 --> 00:37:31.650 And when they flip everything to x's to the left and right 00:37:31.650 --> 00:37:33.800 of about 12 letters that you're looking at, people just 00:37:33.800 --> 00:37:34.550 don't know. 00:37:34.550 --> 00:37:37.490 Because they don't really see it as they read anymore. 00:37:37.490 --> 00:37:38.510 Does that make sense? 00:37:38.510 --> 00:37:40.980 12 letters at a time. 00:37:40.980 --> 00:37:43.440 So again, we're trying to understand some of these 00:37:43.440 --> 00:37:46.560 things in regards to difficulties people have. 00:37:46.560 --> 00:37:49.710 So it turns out there's a part of the brain that's also 00:37:49.710 --> 00:37:52.880 involved in reading where, if you damage, you get what's 00:37:52.880 --> 00:37:54.020 called word blindness. 00:37:54.020 --> 00:37:55.330 So these are adults who are good 00:37:55.330 --> 00:37:56.860 readers, no problem reading. 00:37:56.860 --> 00:37:59.690 They get a stroke Hts left visual cortex around here. 00:37:59.690 --> 00:38:03.470 The most famous original case, in 1887, all of a sudden one 00:38:03.470 --> 00:38:06.020 day after a headache, this man was unable to read. 00:38:06.020 --> 00:38:08.310 His vision was otherwise perfectly good. 00:38:08.310 --> 00:38:10.240 He could hear words and speak words. 00:38:10.240 --> 00:38:12.030 He could see numbers. 00:38:12.030 --> 00:38:13.720 He could write down words. 00:38:13.720 --> 00:38:15.490 His writing was kind of slow and laborious. 00:38:15.490 --> 00:38:17.230 It wasn't typical writing. 00:38:17.230 --> 00:38:19.610 But then you could show him a few moments later what he had 00:38:19.610 --> 00:38:22.570 written, and he would not be able to read it aloud. 00:38:22.570 --> 00:38:26.740 So here's a pathway where stuff out there in the world 00:38:26.740 --> 00:38:28.670 in vision meets how we read. 00:38:36.820 --> 00:38:37.200 Amazing. 00:38:37.200 --> 00:38:39.920 Now it turns out, just like there's a spot in your brain 00:38:39.920 --> 00:38:43.020 that's the first moment where something you see is a face. 00:38:43.020 --> 00:38:48.240 There's a part that's shown here in red that's near that. 00:38:48.240 --> 00:38:50.150 It's bigger in the left hemisphere, the language 00:38:50.150 --> 00:38:50.950 hemisphere. 00:38:50.950 --> 00:38:53.330 It's pretty specific relatively specific for words 00:38:53.330 --> 00:38:56.240 compared to other things. 00:38:56.240 --> 00:38:58.690 And so we end up with a picture like this with 00:38:58.690 --> 00:39:02.070 relatively specific areas in the back of our brain that are 00:39:02.070 --> 00:39:06.800 highly specialized for recognizing where things are. 00:39:06.800 --> 00:39:08.020 I didn't talk too much about that. 00:39:08.020 --> 00:39:12.350 But there's that area, faces, words, and objects. 00:39:12.350 --> 00:39:15.300 And if you have damage to any of these pathways, for 00:39:15.300 --> 00:39:17.740 whatever reason, the rest of our brain can't compensate. 00:39:17.740 --> 00:39:20.106 And it's all a big mystery, who am I looking at, what word 00:39:20.106 --> 00:39:23.540 am I looking at, what object do I see? 00:39:23.540 --> 00:39:27.340 Now, you might imagine that for things like faces or 00:39:27.340 --> 00:39:29.880 locations, we've had evolutionary pressure for 00:39:29.880 --> 00:39:31.270 forever to be good at that. 00:39:31.270 --> 00:39:32.110 Where are we? 00:39:32.110 --> 00:39:33.630 Who are we with? 00:39:33.630 --> 00:39:37.960 Whereas things like words, or nonsense words, and letters, 00:39:37.960 --> 00:39:39.080 or chairs-- 00:39:39.080 --> 00:39:40.950 which are a recent cultural invention-- 00:39:40.950 --> 00:39:44.040 our brains are not genetically predisposed to those specific 00:39:44.040 --> 00:39:44.460 categories. 00:39:44.460 --> 00:39:47.310 So there's a very clever study from Ted Polk in Michigan. 00:39:47.310 --> 00:39:48.270 So we took twins. 00:39:48.270 --> 00:39:49.350 And we'll talk more about this. 00:39:49.350 --> 00:39:52.370 But the way people try to get at until we know the real 00:39:52.370 --> 00:39:55.410 genes involved in things, they'll compare twins who are 00:39:55.410 --> 00:39:58.695 identical twins with the identical genes and twins 00:39:58.695 --> 00:40:02.160 which are so-called fraternal twins who are born to the same 00:40:02.160 --> 00:40:04.870 family but don't have the identical genes. 00:40:04.870 --> 00:40:06.990 And to the extent the identical twins are more 00:40:06.990 --> 00:40:10.290 similar to each other than the fraternal twins, that's a 00:40:10.290 --> 00:40:13.420 suggestion there's genetic influences on whatever you're 00:40:13.420 --> 00:40:14.680 looking at. 00:40:14.680 --> 00:40:17.210 So what they did is they had these people look at faces, 00:40:17.210 --> 00:40:20.760 places, letter strings, and chairs. 00:40:20.760 --> 00:40:23.630 And they calculated how similar was one twin to 00:40:23.630 --> 00:40:28.140 another, either identically genetic or not. 00:40:28.140 --> 00:40:32.200 And what they found was that for the faces and the places, 00:40:32.200 --> 00:40:35.100 there was much more similar, significantly more similarly 00:40:35.100 --> 00:40:38.110 between identical twins than fraternal twins. 00:40:38.110 --> 00:40:40.910 That's the genetic predisposition, in some way, 00:40:40.910 --> 00:40:44.600 of how you will see a face or know where you are. 00:40:44.600 --> 00:40:46.640 If they compare reading nonsense words, letter 00:40:46.640 --> 00:40:49.540 strings, or chairs, the two kinds of twins 00:40:49.540 --> 00:40:51.110 were just the same. 00:40:51.110 --> 00:40:54.990 It's as if there's no genetic predisposition in you to know 00:40:54.990 --> 00:40:55.960 where in your brain you're going to 00:40:55.960 --> 00:40:57.360 process words or chairs. 00:40:57.360 --> 00:40:58.370 But that makes sense. 00:40:58.370 --> 00:41:03.770 Because a couple thousand years ago there were no words. 00:41:03.770 --> 00:41:05.020 And a few more thousand years than that, 00:41:05.020 --> 00:41:06.330 there were no chairs. 00:41:06.330 --> 00:41:08.870 So that's we don't have the genes for recent 00:41:08.870 --> 00:41:10.140 inventions in the world. 00:41:10.140 --> 00:41:12.340 But our brain is brilliant at becoming good at things like 00:41:12.340 --> 00:41:15.425 reading as we invent them. 00:41:15.425 --> 00:41:17.930 For the last part of the talk, I want to talk about face 00:41:17.930 --> 00:41:18.470 recognition. 00:41:18.470 --> 00:41:22.090 So all of us know that when we learn to read it was 00:41:22.090 --> 00:41:22.900 a pretty big deal. 00:41:22.900 --> 00:41:24.300 It was a while ago. 00:41:24.300 --> 00:41:26.360 If you are a typical reader, you're passionate. 00:41:26.360 --> 00:41:27.550 If you're a struggling reader, that can be 00:41:27.550 --> 00:41:28.600 a persistent problem. 00:41:28.600 --> 00:41:30.520 But you got through it, and you're a reader. 00:41:30.520 --> 00:41:33.210 None of us went to third grade and said, today is the day 00:41:33.210 --> 00:41:35.346 that we study faces. 00:41:35.346 --> 00:41:37.810 And your parents are going, I hope you're going at faces. 00:41:37.810 --> 00:41:40.390 Because we really want you to go to MIT someday. 00:41:40.390 --> 00:41:43.270 This is the moment to get ready for the face SAT. 00:41:43.270 --> 00:41:45.250 But what I'm going to show you is that in fact, through 00:41:45.250 --> 00:41:48.040 experience, you're educated for faces. 00:41:48.040 --> 00:41:50.750 And there's some social consequences for the faces 00:41:50.750 --> 00:41:53.340 you're not educated on, on average. 00:41:53.340 --> 00:41:55.170 So let's talk about that. 00:41:55.170 --> 00:41:59.210 So one way we see faces is we see faces that are right-side 00:41:59.210 --> 00:42:01.580 up, overwhelmingly. 00:42:01.580 --> 00:42:04.210 So I'm going to show you this upside down face. 00:42:04.210 --> 00:42:05.380 I'm going to reverse it. 00:42:05.380 --> 00:42:07.070 And that's what it is. 00:42:07.070 --> 00:42:08.840 That's gruesome, right? 00:42:08.840 --> 00:42:11.220 But can you tell that when that turns, 00:42:11.220 --> 00:42:12.800 it's going to be this? 00:42:12.800 --> 00:42:15.930 So the way that we interpret the weirdness of face 00:42:15.930 --> 00:42:18.780 inversion, the fact that we process upside 00:42:18.780 --> 00:42:22.030 down faces so badly-- 00:42:22.030 --> 00:42:24.230 we don't have any hint of what's really there-- 00:42:24.230 --> 00:42:26.800 it's because we didn't practice on them. 00:42:26.800 --> 00:42:29.310 It's as if I gave you a test in a language that you never 00:42:29.310 --> 00:42:31.030 spoke or read. 00:42:31.030 --> 00:42:32.920 Well you can do badly. 00:42:32.920 --> 00:42:34.845 So that shows you that faces, it's a 00:42:34.845 --> 00:42:36.510 so experienced dependent. 00:42:36.510 --> 00:42:38.520 It's because you see upright faces you get 00:42:38.520 --> 00:42:39.470 good at upright faces. 00:42:39.470 --> 00:42:41.000 All we have to do is turn it upside down. 00:42:41.000 --> 00:42:44.230 And all the knowledge and skill you have, it's as if I 00:42:44.230 --> 00:42:45.920 tested you in a different language. 00:42:45.920 --> 00:42:48.530 It's that specific. 00:42:48.530 --> 00:42:51.450 Here's another example, side by side, looks pretty similar. 00:42:51.450 --> 00:42:52.700 But that's what you're really seeing. 00:42:57.390 --> 00:42:59.220 It's unbelievable. 00:42:59.220 --> 00:43:03.400 Turn your head to believe me in case you're suspicious. 00:43:03.400 --> 00:43:04.650 This is legit. 00:43:06.560 --> 00:43:09.830 We're so bad at upside down faces because we don't 00:43:09.830 --> 00:43:12.270 practice on them. 00:43:12.270 --> 00:43:15.640 So what we are good at in faces is so much dependent on 00:43:15.640 --> 00:43:17.930 what we practice. 00:43:17.930 --> 00:43:19.240 You may recognize this person or not. 00:43:24.440 --> 00:43:25.690 These are less dramatic. 00:43:28.930 --> 00:43:30.670 People don't become as good as they get at faces 00:43:30.670 --> 00:43:32.870 until about age 16. 00:43:32.870 --> 00:43:34.680 We don't consciously practice it. 00:43:34.680 --> 00:43:36.890 But the social experience we have is practicing, 00:43:36.890 --> 00:43:40.240 practicing, practicing how you perceive a face. 00:43:43.670 --> 00:43:46.530 One fun study from a Susan Carey now at Harvard is she 00:43:46.530 --> 00:43:48.580 took dog show judges. 00:43:48.580 --> 00:43:50.300 Now, I don't know too much about dog shows. 00:43:50.300 --> 00:43:51.850 Some of you might know something. 00:43:51.850 --> 00:43:53.510 But a little bit of what I know is this. 00:43:53.510 --> 00:43:56.670 Sort of like in sports, you have judges who work their way 00:43:56.670 --> 00:44:00.260 up a ladder of experience and reputation. 00:44:00.260 --> 00:44:02.620 So in sports things, you have the local judges. 00:44:02.620 --> 00:44:03.940 And the really good ones become the ones 00:44:03.940 --> 00:44:04.810 for the bigger leagues. 00:44:04.810 --> 00:44:06.660 And the big ones get to go to the Super Bowl and World 00:44:06.660 --> 00:44:09.620 Series who are really skilled and thought to be excellent. 00:44:09.620 --> 00:44:11.120 Dog show judges, similarly, start locally. 00:44:11.120 --> 00:44:13.420 The ones who seem pretty good and persistent at it then 00:44:13.420 --> 00:44:14.480 become the state judge show. 00:44:14.480 --> 00:44:16.940 And then they go to the big one in New York. 00:44:16.940 --> 00:44:21.870 And so they did these face inversion experiments on dog 00:44:21.870 --> 00:44:24.970 show judges, people who were just beginning to be a dog 00:44:24.970 --> 00:44:27.300 show judge, people who have done it for a while, people 00:44:27.300 --> 00:44:28.790 who've done it for a lot of years. 00:44:28.790 --> 00:44:32.320 And they asked, when do you get so much better at a 00:44:32.320 --> 00:44:35.270 right-side up dog face than an upside down dog face? 00:44:35.270 --> 00:44:38.350 Now, most people are about the same to start with. 00:44:38.350 --> 00:44:40.830 Because we're not that good at dog faces. 00:44:40.830 --> 00:44:41.990 You might know a dog or two. 00:44:41.990 --> 00:44:45.060 But you don't know hundreds of dollars. 00:44:45.060 --> 00:44:48.660 It took eight years for dog show judges-- and they were 00:44:48.660 --> 00:44:50.910 dog enthusiasts for many years before they 00:44:50.910 --> 00:44:52.490 became a dog show judge-- 00:44:52.490 --> 00:44:56.480 eight years of seeing many, many dogs at dog show 00:44:56.480 --> 00:45:00.600 competitions to develop the upright face expertise that we 00:45:00.600 --> 00:45:02.720 all have for faces as adults. 00:45:02.720 --> 00:45:05.750 So for an adult, you have to practice eight years to get 00:45:05.750 --> 00:45:08.140 this kind of expertise. 00:45:08.140 --> 00:45:09.930 You can't just do it by cramming. 00:45:09.930 --> 00:45:12.430 It's practice, practice, practice in the most brutal 00:45:12.430 --> 00:45:13.680 fundamental sense. 00:45:15.810 --> 00:45:18.410 Now I'll say one last thing about this then 00:45:18.410 --> 00:45:19.850 go to the last topic. 00:45:19.850 --> 00:45:21.940 The other thing is that we understand also-- and we've 00:45:21.940 --> 00:45:24.312 mentioned this before, but I'll say it one more time-- 00:45:24.312 --> 00:45:28.700 that imagination and perception use the same neural 00:45:28.700 --> 00:45:30.170 territory in your mind. 00:45:30.170 --> 00:45:32.610 So here's a study from Nancy Kanwisher again. 00:45:32.610 --> 00:45:35.760 Here's a part of the brain that responds to faces, seeing 00:45:35.760 --> 00:45:39.600 a face, seeing a house, seeing a face, seeing a house. 00:45:39.600 --> 00:45:43.380 Now, imagining a face, imagining a house, imagining a 00:45:43.380 --> 00:45:45.720 face, imagining a house. 00:45:45.720 --> 00:45:49.460 So seeing one drives the brain more strongly 00:45:49.460 --> 00:45:50.910 than imagining it. 00:45:50.910 --> 00:45:54.030 But when you imagine a face, you seem to use the same brain 00:45:54.030 --> 00:45:56.600 network as when you see it. 00:45:56.600 --> 00:45:59.230 It's just not as vivid and powerful. 00:45:59.230 --> 00:46:02.280 So perception is the stuff literally in your mind of 00:46:02.280 --> 00:46:03.000 imagination. 00:46:03.000 --> 00:46:05.870 You can imagine things, because you've seen them 00:46:05.870 --> 00:46:08.450 before, literally in your brain It's the 00:46:08.450 --> 00:46:11.090 same part of the brain. 00:46:11.090 --> 00:46:13.620 So the last topic I want to talk about is a sensitive and 00:46:13.620 --> 00:46:14.370 difficult one. 00:46:14.370 --> 00:46:17.220 So I'm going to do it right, I hope. 00:46:17.220 --> 00:46:19.250 But it's one that's a practical one, and a 00:46:19.250 --> 00:46:23.240 consequence, we believe, of the fact that you're good at 00:46:23.240 --> 00:46:25.120 faces that you practice. 00:46:25.120 --> 00:46:28.600 So we're going to talk about in these studies people 00:46:28.600 --> 00:46:31.950 perceiving faces of European Americans, or white Americans, 00:46:31.950 --> 00:46:33.940 or African Americans. 00:46:33.940 --> 00:46:37.630 And there's a huge amount of research 00:46:37.630 --> 00:46:39.120 that shows the following. 00:46:39.120 --> 00:46:44.920 That whatever racial group you see a lot of, you're pretty 00:46:44.920 --> 00:46:46.240 good at remembering those faces. 00:46:46.240 --> 00:46:50.790 At whatever group you see less, you're far worse. 00:46:50.790 --> 00:46:53.950 We interpret this as a consequence of the practice 00:46:53.950 --> 00:46:55.720 that you have. 00:46:55.720 --> 00:46:58.900 But social psychologists worry it has a second consequence. 00:46:58.900 --> 00:47:01.150 Let me tell you the practice story. 00:47:01.150 --> 00:47:02.540 So we did a study. 00:47:02.540 --> 00:47:03.120 This is from us. 00:47:03.120 --> 00:47:04.800 But it's very similar to other people in terms of the 00:47:04.800 --> 00:47:05.500 conclusion. 00:47:05.500 --> 00:47:08.500 There's literally like 1,000 of these studies that show 00:47:08.500 --> 00:47:11.480 that people are superior at recognizing in an experiment 00:47:11.480 --> 00:47:14.950 faces from their own group than from other groups. 00:47:14.950 --> 00:47:17.300 And here, an experiment that was done with Stanford 00:47:17.300 --> 00:47:19.850 students, a look in their mind and then in their brain. 00:47:19.850 --> 00:47:21.930 So these are Stanford students just some years ago, maybe a 00:47:21.930 --> 00:47:23.180 lot like you in many ways. 00:47:25.820 --> 00:47:28.550 They saw some faces, and then they got a memory test. 00:47:28.550 --> 00:47:30.790 This is their performance on the memory test. 00:47:30.790 --> 00:47:35.050 So we had both European American and African American 00:47:35.050 --> 00:47:37.650 faces that they viewed. 00:47:37.650 --> 00:47:40.410 And the participants in the research were both African 00:47:40.410 --> 00:47:42.470 American and European American. 00:47:42.470 --> 00:47:46.370 OK so there were white faces, white subjects, black faces, 00:47:46.370 --> 00:47:48.070 black subjects. 00:47:48.070 --> 00:47:49.800 And what you can see is this. 00:47:49.800 --> 00:47:51.820 The higher the bar, the better the memory. 00:47:51.820 --> 00:47:55.440 In both groups, they're better in performance at remembering 00:47:55.440 --> 00:48:00.420 faces from their own group. 00:48:00.420 --> 00:48:02.350 But there's more to it than that. 00:48:02.350 --> 00:48:05.590 If you look at these bars, these are the memory for the 00:48:05.590 --> 00:48:06.695 white faces. 00:48:06.695 --> 00:48:09.240 And it's about the same in the two groups. 00:48:09.240 --> 00:48:11.120 And look at the big difference for the 00:48:11.120 --> 00:48:13.190 African American faces. 00:48:13.190 --> 00:48:15.360 So two things are happening here. 00:48:15.360 --> 00:48:18.610 One of them is there's superior memory from faces 00:48:18.610 --> 00:48:20.630 from your own group. 00:48:20.630 --> 00:48:25.480 And the second story is that for what we believed, and from 00:48:25.480 --> 00:48:27.740 other research as well, is this. 00:48:27.740 --> 00:48:30.670 If you're a minority group, you're still pretty good at 00:48:30.670 --> 00:48:32.420 the majority faces. 00:48:32.420 --> 00:48:34.460 If you're a majority group, you're not so good at the 00:48:34.460 --> 00:48:35.790 minority faces. 00:48:35.790 --> 00:48:38.580 So these are European American Stanford students. 00:48:38.580 --> 00:48:41.990 And look how a miserable their memory is for these African 00:48:41.990 --> 00:48:43.240 American faces. 00:48:46.140 --> 00:48:48.920 This is a difficult topic for us, in part, because race is a 00:48:48.920 --> 00:48:51.980 different topic for good reasons. 00:48:51.980 --> 00:48:56.560 But social psychologists worry that the lack of practice that 00:48:56.560 --> 00:49:00.170 many of us have on other groups growing up at home, in 00:49:00.170 --> 00:49:01.370 our community, and schools-- 00:49:01.370 --> 00:49:03.410 and it varies for people, but on average-- 00:49:03.410 --> 00:49:06.710 makes us less able to individuate in our memory one 00:49:06.710 --> 00:49:09.420 person from another in other groups. 00:49:09.420 --> 00:49:13.460 And now this is not about racial attitudes. 00:49:13.460 --> 00:49:17.280 This is simple, objective recognition of faces. 00:49:17.280 --> 00:49:20.880 But it could certainly support consideration of other groups 00:49:20.880 --> 00:49:22.670 as if they were all the same. 00:49:22.670 --> 00:49:24.490 Because they look all the same. 00:49:24.490 --> 00:49:26.430 I remember I had an African American 00:49:26.430 --> 00:49:28.690 colleague at Stanford. 00:49:28.690 --> 00:49:29.680 And he was a dean. 00:49:29.680 --> 00:49:33.190 And he went to China with a Nobel laureate who is now the 00:49:33.190 --> 00:49:37.140 Secretary of Energy in the Obama 00:49:37.140 --> 00:49:39.230 administration, Steve Chu. 00:49:39.230 --> 00:49:41.980 And, of course, Nobel laureates are a pretty big. 00:49:41.980 --> 00:49:45.540 So this dean went to this Nobel laureate all the time. 00:49:45.540 --> 00:49:48.610 We're meeting Stanford donors and other things. 00:49:48.610 --> 00:49:49.710 He said they got on the plane. 00:49:49.710 --> 00:49:52.570 They went to China, the two of them. 00:49:52.570 --> 00:49:54.390 And he went into a reception. 00:49:54.390 --> 00:49:57.870 And he knew Steve Chu was in there. 00:49:57.870 --> 00:50:00.500 The African American dean said, I could not pick him out 00:50:00.500 --> 00:50:01.700 for my life. 00:50:01.700 --> 00:50:05.540 When I saw him now, not with other people I know, but with 00:50:05.540 --> 00:50:08.790 a 500 other Chinese people in a large reception. 00:50:08.790 --> 00:50:12.180 So it's not about bad attitudes in this case. 00:50:12.180 --> 00:50:14.610 It's just literally the experience you have. 00:50:14.610 --> 00:50:19.960 And in the brain, this part of this FFA, responds more to 00:50:19.960 --> 00:50:21.600 groups from your own-- 00:50:21.600 --> 00:50:22.350 on average-- 00:50:22.350 --> 00:50:24.390 from your own racial group than the other racial group. 00:50:24.390 --> 00:50:26.600 And we think that's promoting the ease with which to 00:50:26.600 --> 00:50:31.130 identify individuals in your group and the difficulty with 00:50:31.130 --> 00:50:34.340 which you can identify I individuals in another group. 00:50:34.340 --> 00:50:36.650 And so we have strong reason to think that this is all 00:50:36.650 --> 00:50:38.910 about this particular phenomenon about your 00:50:38.910 --> 00:50:40.340 experience. 00:50:40.340 --> 00:50:41.810 So let me tell you why. 00:50:41.810 --> 00:50:44.400 One thing is we know that this is not present at birth. 00:50:44.400 --> 00:50:47.040 People have done these kinds of experiments with infants. 00:50:47.040 --> 00:50:51.300 These racial biases in what kinds of faces we can remember 00:50:51.300 --> 00:50:52.390 are not present at birth. 00:50:52.390 --> 00:50:54.100 So they're not in our genes. 00:50:54.100 --> 00:50:55.850 They're from our experience. 00:50:55.850 --> 00:50:57.510 But they are present by three months. 00:50:57.510 --> 00:51:01.180 But by then you've seen a lot of people in your family. 00:51:01.180 --> 00:51:03.840 And the kind of experiment that's very telling for this 00:51:03.840 --> 00:51:05.980 is a study where there were Korean children. 00:51:05.980 --> 00:51:07.230 They were three to nine years old. 00:51:07.230 --> 00:51:10.850 They were adopted by European Caucasian families, so, in the 00:51:10.850 --> 00:51:12.950 sense, a cross-racial adoption. 00:51:12.950 --> 00:51:15.290 And then they tested their memory for faces. 00:51:15.290 --> 00:51:17.960 And for these Korean children adopted by European Caucasian 00:51:17.960 --> 00:51:20.900 families, they had better memory for the Caucasian 00:51:20.900 --> 00:51:26.370 faces, because that's who they saw around them all the time. 00:51:26.370 --> 00:51:31.810 And they were just like their French peers who also saw 00:51:31.810 --> 00:51:33.530 Caucasian faces all the time. 00:51:33.530 --> 00:51:35.680 And the opposite of the findings that you've got with 00:51:35.680 --> 00:51:39.780 Korean children in South Korea. 00:51:39.780 --> 00:51:43.820 The inversion one is kind of funny, amazing. 00:51:43.820 --> 00:51:48.250 The fact that we can struggle to individuate in memory one 00:51:48.250 --> 00:51:51.130 African American from another, or one Asian American from 00:51:51.130 --> 00:51:53.530 another, or one Caucasian American from another 00:51:53.530 --> 00:51:55.970 depending on the environment that we grew up in and were 00:51:55.970 --> 00:52:01.180 exposed to, that could be facilitating stereotyping and 00:52:01.180 --> 00:52:04.750 lack of individuation of people in other groups. 00:52:04.750 --> 00:52:06.160 So the very last thing I want to do-- and this is just a 00:52:06.160 --> 00:52:06.910 couple minutes-- 00:52:06.910 --> 00:52:09.270 is talk about expression in faces. 00:52:09.270 --> 00:52:10.150 And I'll come back to this in detail. 00:52:10.150 --> 00:52:16.730 I just want to give you one last example of recognition in 00:52:16.730 --> 00:52:18.130 the amygdala and fear. 00:52:18.130 --> 00:52:20.050 So we'll come back to this in some detail later on. 00:52:20.050 --> 00:52:23.680 But most researchers argue there's about six basic 00:52:23.680 --> 00:52:27.040 emotions that people around the world transmit with their 00:52:27.040 --> 00:52:32.060 facial expressions, happiness, sadness, fear, anger, 00:52:32.060 --> 00:52:33.620 surprise, and disgust. 00:52:33.620 --> 00:52:36.470 You can show these pictures to people around the world, and 00:52:36.470 --> 00:52:39.610 they'll be, to some degree, consensus about what they are, 00:52:39.610 --> 00:52:43.220 universal expressions of feelings transmitted by facial 00:52:43.220 --> 00:52:45.240 expressions. 00:52:45.240 --> 00:52:46.950 Now let's talk about fear faces. 00:52:46.950 --> 00:52:48.310 I'll just talk about fear today. 00:52:48.310 --> 00:52:49.560 And we'll talk about the amygdala. 00:52:49.560 --> 00:52:51.280 So we have one on the left and one on the right, it's a very 00:52:51.280 --> 00:52:54.730 small structure, almond shaped, one inside each of the 00:52:54.730 --> 00:52:58.050 temporal lobes right next to the hippocampus. 00:52:58.050 --> 00:53:00.610 So that's a view from the side of where that's located, one 00:53:00.610 --> 00:53:02.540 on the left and one on the right. 00:53:02.540 --> 00:53:04.360 And we know from a lot of animal research-- and I'll 00:53:04.360 --> 00:53:06.490 come back to this again-- 00:53:06.490 --> 00:53:09.270 the amygdala is essential for learned 00:53:09.270 --> 00:53:11.590 fear, for learned fear. 00:53:11.590 --> 00:53:14.520 So here's an experiment that shows you that. 00:53:14.520 --> 00:53:17.430 One thing that mice know is cats are bad news. 00:53:17.430 --> 00:53:18.930 It's survival. 00:53:18.930 --> 00:53:20.290 What they did in this experiment is they 00:53:20.290 --> 00:53:21.660 anesthetized the cat. 00:53:21.660 --> 00:53:24.690 That's why the cat looks glassy-eyed. 00:53:24.690 --> 00:53:29.220 Obviously the experiment would end too quickly for the mouse, 00:53:29.220 --> 00:53:32.200 if the mouse had to come out and play with the cat. 00:53:32.200 --> 00:53:33.660 The experiment would be brutal, and ugly, 00:53:33.660 --> 00:53:35.360 and over too quickly. 00:53:35.360 --> 00:53:38.150 But if the cat is breathing, the cat's eyes are open, it's 00:53:38.150 --> 00:53:38.510 anesthetized. 00:53:38.510 --> 00:53:40.070 But it can't move. 00:53:40.070 --> 00:53:44.550 Now a typical rat or mouse will typically 00:53:44.550 --> 00:53:45.670 still avoid the cat. 00:53:45.670 --> 00:53:47.110 It's not worth figuring out exactly what's 00:53:47.110 --> 00:53:47.910 going on with the cat. 00:53:47.910 --> 00:53:48.970 Are they faking me out? 00:53:48.970 --> 00:53:51.620 I'll just go that way. 00:53:51.620 --> 00:53:55.775 But this is not the mouse who has the amygdala removed. 00:53:58.500 --> 00:54:00.980 It's not fearful of what it ought to be fearful of 00:54:00.980 --> 00:54:04.260 anymore, even survival. 00:54:04.260 --> 00:54:07.670 What we believe the most important role of fear is not 00:54:07.670 --> 00:54:09.530 fear of SATs or midterms. 00:54:09.530 --> 00:54:11.600 Although we live in that world. 00:54:11.600 --> 00:54:13.950 It's fear of what injure you and kill you. 00:54:13.950 --> 00:54:14.960 Those are the things to learn. 00:54:14.960 --> 00:54:16.940 Be fearful of what can kill you. 00:54:16.940 --> 00:54:18.740 Be fearful of what can injure you. 00:54:18.740 --> 00:54:21.490 Without the amygdala, you lose that fear. 00:54:21.490 --> 00:54:24.390 But here's the other-- this is my last slide-- amazing thing. 00:54:24.390 --> 00:54:26.610 There are humans who have injuries selectively to the 00:54:26.610 --> 00:54:27.620 amygdala, very few. 00:54:27.620 --> 00:54:29.190 But there's a few. 00:54:29.190 --> 00:54:32.550 And not only do they have some problems with fear learning. 00:54:32.550 --> 00:54:35.640 But they can't recognize fearful 00:54:35.640 --> 00:54:37.195 facial expressions anymore. 00:54:39.970 --> 00:54:42.350 If they ask them to say, what is this, without the word 00:54:42.350 --> 00:54:44.440 present, they're very bad at telling you 00:54:44.440 --> 00:54:45.820 that's a fearful face. 00:54:45.820 --> 00:54:48.180 They can recognize all the other expressions pretty well 00:54:48.180 --> 00:54:51.680 but not the fearful ones. 00:54:51.680 --> 00:54:53.160 also 00:54:53.160 --> 00:54:54.480 They're good of faces. 00:54:54.480 --> 00:54:55.360 They're not prosopagnosia. 00:54:55.360 --> 00:54:56.160 They're fine at faces. 00:54:56.160 --> 00:54:57.030 They recognize their family. 00:54:57.030 --> 00:54:59.360 But they can't recognize fearful expressions 00:54:59.360 --> 00:55:01.970 selectively. 00:55:01.970 --> 00:55:05.440 This is actually a very good drawing happy, sad, surprised, 00:55:05.440 --> 00:55:07.400 disgusted, angry. 00:55:07.400 --> 00:55:09.875 When she's asked to draw a fearful facial expression, 00:55:09.875 --> 00:55:12.140 this patient draws this, a baby being afraid. 00:55:12.140 --> 00:55:14.210 She understands the concept. 00:55:14.210 --> 00:55:16.430 But it's not only that she can't recognize it. 00:55:16.430 --> 00:55:20.020 She can't imagine what a fearful face looks like. 00:55:20.020 --> 00:55:23.410 And we saw this over and over again. 00:55:23.410 --> 00:55:25.060 And there's one last message in this. 00:55:25.060 --> 00:55:27.850 Somehow our knowledge about what a fearful face looks 00:55:27.850 --> 00:55:29.550 like, we're not scared of this. 00:55:29.550 --> 00:55:31.130 You don't look at this and go, oh my gosh. 00:55:31.130 --> 00:55:33.030 I can't believe he showed that in class. 00:55:33.030 --> 00:55:37.250 I'll never sleep for 48 hours. 00:55:37.250 --> 00:55:39.530 That's a social signal for somebody telling you, whoa. 00:55:39.530 --> 00:55:41.000 There's something terrible happening here. 00:55:41.000 --> 00:55:41.670 Look around you. 00:55:41.670 --> 00:55:42.200 We better run. 00:55:42.200 --> 00:55:43.550 It's a social signal. 00:55:43.550 --> 00:55:46.780 And the part of your brain that learns what can kill you 00:55:46.780 --> 00:55:51.160 also is where the knowledge is stored to recognize a social 00:55:51.160 --> 00:55:54.160 signal about something that could be very dangerous. 00:55:54.160 --> 00:55:56.560 The same idea that we put our knowledge in the parts of 00:55:56.560 --> 00:55:58.180 their brain that act upon the world.