1 00:00:00,530 --> 00:00:02,960 The following content is provided under a Creative 2 00:00:02,960 --> 00:00:04,370 Commons license. 3 00:00:04,370 --> 00:00:07,410 Your support will help MIT OpenCourseWare continue to 4 00:00:07,410 --> 00:00:11,060 offer high quality educational resources for free. 5 00:00:11,060 --> 00:00:13,960 To make a donation or view additional materials from 6 00:00:13,960 --> 00:00:16,680 hundreds of MIT courses, visit mitopencourseware@ocw.mit.edu. 7 00:00:34,810 --> 00:00:36,870 PROFESSOR: So last week Melissa told you-- 8 00:00:36,870 --> 00:00:38,140 or a couple days ago-- 9 00:00:38,140 --> 00:00:39,510 about vision. 10 00:00:39,510 --> 00:00:42,780 And if there's two huge messages, I think, out of that 11 00:00:42,780 --> 00:00:46,210 lecture, it's first that even the most simple aspects of 12 00:00:46,210 --> 00:00:50,150 perception are based on a synthesis between what's out 13 00:00:50,150 --> 00:00:53,000 there and the rules by which your mind 14 00:00:53,000 --> 00:00:55,130 interprets the world. 15 00:00:55,130 --> 00:00:58,510 And what you ultimately see is that interaction, that 16 00:00:58,510 --> 00:01:02,010 synthesis, that dialogue, that construction between what's 17 00:01:02,010 --> 00:01:05,620 out there and how your mind chooses to interpret it. 18 00:01:05,620 --> 00:01:07,990 The second big point is there's a lot of organization 19 00:01:07,990 --> 00:01:09,890 of the visual system in our brain. 20 00:01:09,890 --> 00:01:13,240 And we can track its organization from the first 21 00:01:13,240 --> 00:01:17,460 moment that photons enter your eyes all the way through until 22 00:01:17,460 --> 00:01:22,940 you recognize a loved one, a word, or an object out there. 23 00:01:22,940 --> 00:01:27,040 And we said that in the neocortex, the world is 24 00:01:27,040 --> 00:01:31,190 divided into two big channels of visual processing, which 25 00:01:31,190 --> 00:01:34,990 are what things are and where things are. 26 00:01:34,990 --> 00:01:38,220 So now I'm going to pick up on that a little bit today. 27 00:01:38,220 --> 00:01:41,370 As you go around and see things all the time, what is 28 00:01:41,370 --> 00:01:43,850 it that you mostly see? 29 00:01:43,850 --> 00:01:46,430 On an average day, you wake up in the morning. 30 00:01:50,795 --> 00:01:54,910 I know you're all like, what's he looking for? 31 00:01:54,910 --> 00:01:56,140 What's the answer? 32 00:01:56,140 --> 00:01:57,260 But just in everything. 33 00:01:57,260 --> 00:02:00,740 You see people a lot. 34 00:02:00,740 --> 00:02:02,070 So faces, we'll talk about that. 35 00:02:02,070 --> 00:02:04,790 You see objects, chairs, tables in the morning. 36 00:02:04,790 --> 00:02:06,690 A toothbrush and soap is useful, right? 37 00:02:06,690 --> 00:02:07,980 You see objects. 38 00:02:07,980 --> 00:02:11,070 And another huge use of your visual system is reading. 39 00:02:11,070 --> 00:02:14,040 You see words, right, on books, on computers. 40 00:02:14,040 --> 00:02:18,050 So we're going to talk a little bit about how we see 41 00:02:18,050 --> 00:02:21,310 what things are, objects in the world, faces in the world, 42 00:02:21,310 --> 00:02:23,790 and words so that we can read. 43 00:02:23,790 --> 00:02:26,480 And we'll talk about both some processes that go on in our 44 00:02:26,480 --> 00:02:29,610 mind and brain that let us become terrific at recognizing 45 00:02:29,610 --> 00:02:33,080 what's out there and knowing who we're talking to, what 46 00:02:33,080 --> 00:02:36,110 we're reading, what we're holding, and so on, and then 47 00:02:36,110 --> 00:02:38,540 about disorders in the brain that illuminate, I think, a 48 00:02:38,540 --> 00:02:40,990 little bit about those processes. 49 00:02:40,990 --> 00:02:46,970 So let me start with objects and agnosia. 50 00:02:46,970 --> 00:02:50,110 Agnosia means not knowing. 51 00:02:50,110 --> 00:02:52,680 So we're going to talk about two ways in which people seen 52 00:02:52,680 --> 00:02:53,440 to not know. 53 00:02:53,440 --> 00:02:54,910 And that gives us a hint, then, about how 54 00:02:54,910 --> 00:02:56,980 we actually do know. 55 00:02:56,980 --> 00:02:58,630 And they've been called apperceptive 56 00:02:58,630 --> 00:02:59,990 and associative agnosias. 57 00:02:59,990 --> 00:03:02,400 Apperceptive seems to be people see the parts, but they 58 00:03:02,400 --> 00:03:03,640 don't pull it together. 59 00:03:03,640 --> 00:03:05,500 Associative agnosia, they see the whole 60 00:03:05,500 --> 00:03:06,830 thing pretty decently. 61 00:03:06,830 --> 00:03:10,390 But they can't figure out what it means, what it is in a 62 00:03:10,390 --> 00:03:11,640 practical sense. 63 00:03:11,640 --> 00:03:13,880 And, lastly, I'll talk to you about a very surprising 64 00:03:13,880 --> 00:03:17,070 finding where people lose knowledge of some kinds of 65 00:03:17,070 --> 00:03:20,180 objects in the world but not others, and sort of give us a 66 00:03:20,180 --> 00:03:24,170 new insight into how our brain organizes knowledge. 67 00:03:24,170 --> 00:03:26,400 So agnosia is a modality-specific inability. 68 00:03:26,400 --> 00:03:27,840 So we'll talk today about vision. 69 00:03:27,840 --> 00:03:32,050 There's agnosias in audition, and in touch, and so on. 70 00:03:32,050 --> 00:03:34,210 But I'll focus just on vision, modality-specific. 71 00:03:34,210 --> 00:03:35,880 These people are fine if they hold 72 00:03:35,880 --> 00:03:37,730 something or hear something. 73 00:03:37,730 --> 00:03:39,520 And it's not explained by things like you don't see so 74 00:03:39,520 --> 00:03:42,600 well, or you're not paying attention, or you can't speak. 75 00:03:42,600 --> 00:03:45,640 It seems to be just that you lose the ability to recognize 76 00:03:45,640 --> 00:03:48,960 by sight what something is. 77 00:03:48,960 --> 00:03:51,510 So again, apperceptive agnosia, will link it to the 78 00:03:51,510 --> 00:03:54,460 right hemisphere and associative agnosia to the 79 00:03:54,460 --> 00:03:55,555 left hemisphere. 80 00:03:55,555 --> 00:03:58,400 And let me show you examples of what these patients do. 81 00:03:58,400 --> 00:04:00,620 So here's patients with right hemisphere damage. 82 00:04:00,620 --> 00:04:04,430 We're attempting, simply, to copy this triangle or copy 83 00:04:04,430 --> 00:04:04,930 these things. 84 00:04:04,930 --> 00:04:05,760 It's right in front of them. 85 00:04:05,760 --> 00:04:06,830 They're copying it. 86 00:04:06,830 --> 00:04:09,040 And you can see that it's as if they have almost no 87 00:04:09,040 --> 00:04:10,660 appreciation for what the thing is out there. 88 00:04:10,660 --> 00:04:13,620 This is a pretty miserable 3. 89 00:04:13,620 --> 00:04:16,740 Right in front of you, it's as if the whole thing weren't 90 00:04:16,740 --> 00:04:17,899 cohering for anything. 91 00:04:17,899 --> 00:04:22,680 Even a shape is just a mysterious bundle of stuff. 92 00:04:22,680 --> 00:04:24,010 Or we can make it multiple choice. 93 00:04:24,010 --> 00:04:26,210 Well multiple choice, we know it's easier. 94 00:04:26,210 --> 00:04:29,400 So all they have to do is cross out which of these four 95 00:04:29,400 --> 00:04:31,770 things looks like this. 96 00:04:31,770 --> 00:04:33,360 And they picked the circle here. 97 00:04:33,360 --> 00:04:35,610 Or instead of the x, they picked the o. 98 00:04:35,610 --> 00:04:38,010 They're really not getting almost anything about the 99 00:04:38,010 --> 00:04:39,140 quality of the shape. 100 00:04:39,140 --> 00:04:41,790 They're really not recognizing what they're looking at. 101 00:04:41,790 --> 00:04:48,920 Or they'll see this. 102 00:04:48,920 --> 00:04:52,120 But they'll read it as, when they get this, 7415. 103 00:04:52,120 --> 00:04:54,420 They won't take the first interpretation, but will come 104 00:04:54,420 --> 00:04:55,670 up with some other. 105 00:04:58,250 --> 00:05:01,170 When these patients copy something, they see, right in 106 00:05:01,170 --> 00:05:03,780 front of them, that elephant. 107 00:05:03,780 --> 00:05:04,920 You can label things. 108 00:05:04,920 --> 00:05:06,780 But it's a pretty bad copy. 109 00:05:06,780 --> 00:05:09,120 It's not just bad artistry. 110 00:05:09,120 --> 00:05:13,100 It's a bad sense of what the coherent shape is right in 111 00:05:13,100 --> 00:05:13,600 front of them. 112 00:05:13,600 --> 00:05:15,510 And their vision is basically fine. 113 00:05:15,510 --> 00:05:17,920 It's just the shape of it doesn't make any sense. 114 00:05:21,710 --> 00:05:24,000 Not surprisingly then, maybe these patients also struggle 115 00:05:24,000 --> 00:05:25,510 when you make things a little harder. 116 00:05:25,510 --> 00:05:27,640 So what letter is this? 117 00:05:27,640 --> 00:05:28,400 You can get that. 118 00:05:28,400 --> 00:05:29,590 You'd have to look a little bit harder. 119 00:05:29,590 --> 00:05:32,340 Or you might get that this is a cow, or this is a car. 120 00:05:32,340 --> 00:05:34,610 These patients are terrible at those things. 121 00:05:34,610 --> 00:05:35,630 As soon as you make it a little bit 122 00:05:35,630 --> 00:05:39,120 hard, they're finished. 123 00:05:39,120 --> 00:05:41,400 They're also bad if they have damage in the right 124 00:05:41,400 --> 00:05:43,460 hemisphere, posteriorly, at what they 125 00:05:43,460 --> 00:05:44,770 call an unusual view. 126 00:05:44,770 --> 00:05:49,760 So often we see something like a stapler from this view. 127 00:05:49,760 --> 00:05:51,770 We rarely quite see it this way. 128 00:05:51,770 --> 00:05:53,720 But if I showed you this, you could probably make it out. 129 00:05:53,720 --> 00:05:55,560 It might take you a moment by itself. 130 00:05:55,560 --> 00:05:58,520 An unusual view of an object that you see, psychologists 131 00:05:58,520 --> 00:06:01,280 call it a canonical view, which is the usual one. 132 00:06:01,280 --> 00:06:03,130 And what happens to patients who have damage in the right 133 00:06:03,130 --> 00:06:04,060 posterior cortex? 134 00:06:04,060 --> 00:06:08,680 They're terrible at making this unusual perception of a 135 00:06:08,680 --> 00:06:10,090 common object. 136 00:06:10,090 --> 00:06:13,300 They're also terrible if they have to see something that's a 137 00:06:13,300 --> 00:06:14,160 little bit challenging. 138 00:06:14,160 --> 00:06:17,280 Again, like here's some hats but with shadows. 139 00:06:17,280 --> 00:06:19,090 Now normally, we don't think about 140 00:06:19,090 --> 00:06:20,770 shadows as a big problem. 141 00:06:20,770 --> 00:06:23,590 It is for computers that are meant to see. 142 00:06:23,590 --> 00:06:26,535 And it is also a big problem for patients with damage to 143 00:06:26,535 --> 00:06:27,970 the right posterior cortex. 144 00:06:27,970 --> 00:06:30,590 It's as if they can't pull out the object from the shadow. 145 00:06:30,590 --> 00:06:34,570 It's all one big glob to them. 146 00:06:34,570 --> 00:06:37,920 Compare that difficulty just getting basically what's there 147 00:06:37,920 --> 00:06:40,180 to patients with left hemisphere damage who can't 148 00:06:40,180 --> 00:06:41,750 recognize an object. 149 00:06:41,750 --> 00:06:45,160 So here's a patient who was shown pictures of a key, a 150 00:06:45,160 --> 00:06:48,980 pig, a bird, a train, and was asked to copy them. 151 00:06:48,980 --> 00:06:50,590 And the copies are actually excellent. 152 00:06:50,590 --> 00:06:51,970 I mean, they're much better than I would do. 153 00:06:51,970 --> 00:06:55,050 They're excellent copies, right? 154 00:06:55,050 --> 00:06:57,100 But even after the patient has made that excellent copy of 155 00:06:57,100 --> 00:06:58,530 the key, he's asked what is that? 156 00:06:58,530 --> 00:07:00,970 And the patient says, I don't know. 157 00:07:00,970 --> 00:07:04,130 Good copy of a pig, "Could be a dog or any other animal." 158 00:07:04,130 --> 00:07:06,680 That's a dog, but that's it. 159 00:07:06,680 --> 00:07:08,120 The bird is kind of interesting. 160 00:07:08,120 --> 00:07:10,050 He draws a pretty good bird, his copy, right? 161 00:07:10,050 --> 00:07:13,540 But then he says, "It could be a beach stump." And when you 162 00:07:13,540 --> 00:07:14,630 say that, you can see that. 163 00:07:14,630 --> 00:07:17,990 But you and I would never come to that conclusion. 164 00:07:17,990 --> 00:07:19,860 And the train, he gets a little bit of wagon 165 00:07:19,860 --> 00:07:20,840 or car of some kind. 166 00:07:20,840 --> 00:07:24,260 It's a larger being pulled by a smaller. 167 00:07:24,260 --> 00:07:25,670 He vaguely knows it's something. 168 00:07:25,670 --> 00:07:27,070 But it's not quite right either. 169 00:07:27,070 --> 00:07:30,910 But he really gets what it is, the shape. 170 00:07:30,910 --> 00:07:33,350 But it's as if it's stripped of meaning. 171 00:07:33,350 --> 00:07:37,170 It just doesn't mean anything to him. 172 00:07:37,170 --> 00:07:39,035 Now we're going to do a video in a moment. 173 00:07:39,035 --> 00:07:41,320 All right, Tyler? 174 00:07:41,320 --> 00:07:42,580 I'm going to show you some videos today. 175 00:07:42,580 --> 00:07:46,640 The problem is that these videos are sort of grainy. 176 00:07:46,640 --> 00:07:49,650 And there's not really high quality Alan Alda talking on 177 00:07:49,650 --> 00:07:52,550 Scientific American videos of these patients. 178 00:07:52,550 --> 00:07:55,100 So the unfortunate thing is in a visual disorders 179 00:07:55,100 --> 00:07:58,010 demonstration, it's almost as if I'm forcing upon you that 180 00:07:58,010 --> 00:07:58,950 same visual disorder. 181 00:07:58,950 --> 00:07:59,140 OK? 182 00:07:59,140 --> 00:08:01,580 Because you're looking at it, and you go, like, gee. 183 00:08:01,580 --> 00:08:02,840 No wonder he can't recognize it. 184 00:08:02,840 --> 00:08:03,650 I can't recognize it. 185 00:08:03,650 --> 00:08:04,750 So let me tell you. 186 00:08:04,750 --> 00:08:07,110 In a couple moments he's going to look at a 187 00:08:07,110 --> 00:08:08,930 picture of a clarinet. 188 00:08:08,930 --> 00:08:11,060 And if it were a really good video, you 189 00:08:11,060 --> 00:08:11,800 would see it clearly. 190 00:08:11,800 --> 00:08:13,820 But there's just not many of these around. 191 00:08:13,820 --> 00:08:15,870 And these patients are rare that are this perfect. 192 00:08:15,870 --> 00:08:18,770 So I'm going to make this dark. 193 00:08:18,770 --> 00:08:21,030 And we'll see-- thank you, Tyler-- 194 00:08:21,030 --> 00:08:24,060 a patient with visual agnosia. 195 00:08:24,060 --> 00:08:25,770 And you should be impressed by two things. 196 00:08:25,770 --> 00:08:26,600 First, he's very verbal. 197 00:08:26,600 --> 00:08:27,280 He's speaking. 198 00:08:27,280 --> 00:08:28,350 He's smart. 199 00:08:28,350 --> 00:08:31,000 A lot of his brain is working just fine. 200 00:08:31,000 --> 00:08:34,590 And second, you're going to see something kind of 201 00:08:34,590 --> 00:08:36,940 interesting, which is we talked about the 202 00:08:36,940 --> 00:08:38,580 where system last time. 203 00:08:38,580 --> 00:08:41,130 And sometimes people call the where system, 204 00:08:41,130 --> 00:08:43,169 the system for action. 205 00:08:43,169 --> 00:08:45,580 Because pretty much like where you grab something, where you 206 00:08:45,580 --> 00:08:48,060 move, that has a lot to do with the action, the physical 207 00:08:48,060 --> 00:08:49,030 action in the world. 208 00:08:49,030 --> 00:08:52,050 So you're going to can see this man unable to recognize 209 00:08:52,050 --> 00:08:55,120 by his what system, what he's looking at. 210 00:08:55,120 --> 00:08:57,150 But a little bit of information is going to sneak 211 00:08:57,150 --> 00:09:00,850 into his where system, and move his hands in a way that 212 00:09:00,850 --> 00:09:01,600 you'll see appropriate. 213 00:09:01,600 --> 00:09:02,850 So thanks. 214 00:09:08,440 --> 00:09:11,240 So it's so funny if you work in-- 215 00:09:11,240 --> 00:09:14,250 this idea that we only use 10% of our brain. 216 00:09:14,250 --> 00:09:19,010 I can assure you this man has 95%, 98% of his brain. 217 00:09:19,010 --> 00:09:19,615 He can speak. 218 00:09:19,615 --> 00:09:21,145 He can move. 219 00:09:21,145 --> 00:09:22,610 He can make jokes. 220 00:09:22,610 --> 00:09:24,230 He can curse at the end there a little bit. 221 00:09:24,230 --> 00:09:26,810 He can do almost everything that everybody can do. 222 00:09:26,810 --> 00:09:31,980 But he cannot identify what an object is by vision. 223 00:09:31,980 --> 00:09:33,700 Because the injury has occurred in the part of the 224 00:09:33,700 --> 00:09:36,120 brain that's essential for that final step of figuring 225 00:09:36,120 --> 00:09:38,310 out what you're looking for. 226 00:09:38,310 --> 00:09:40,670 It's a very specific part of the brain. 227 00:09:40,670 --> 00:09:44,490 And without it, the rest of his brain can't figure out 228 00:09:44,490 --> 00:09:45,970 what it's looking at. 229 00:09:45,970 --> 00:09:47,260 So his sensation is fine. 230 00:09:47,260 --> 00:09:48,525 He sees where it is. 231 00:09:48,525 --> 00:09:51,020 And he gets the shape even roughly. 232 00:09:51,020 --> 00:09:52,530 He thought it was a pen. 233 00:09:52,530 --> 00:09:55,290 There's something vaguely about the shape. 234 00:09:55,290 --> 00:09:57,020 His naming is fine. 235 00:09:57,020 --> 00:10:01,060 But it's as if, again, this idea of a perfect example of 236 00:10:01,060 --> 00:10:02,840 what we call associative agnosia. 237 00:10:02,840 --> 00:10:04,990 He has all the shape information it seems like you 238 00:10:04,990 --> 00:10:07,270 ought to have, all the language information you have. 239 00:10:07,270 --> 00:10:10,170 But he can't make that move from piecing together what 240 00:10:10,170 --> 00:10:12,350 something is to knowing what it means. 241 00:10:12,350 --> 00:10:14,380 And if he doesn't know what it means, he can't 242 00:10:14,380 --> 00:10:16,710 come up with the name. 243 00:10:16,710 --> 00:10:20,400 If he smells it or holds it, he says, apple or pipe. 244 00:10:20,400 --> 00:10:21,640 He knows the name. 245 00:10:21,640 --> 00:10:24,450 But if he has to look at something and then know what 246 00:10:24,450 --> 00:10:29,450 it is to name it, if I show you a piece of paper and ask 247 00:10:29,450 --> 00:10:31,920 you to name it, you have to say, what is it? 248 00:10:31,920 --> 00:10:33,640 Then I name it. 249 00:10:33,640 --> 00:10:38,140 He can't make that move in vision to what it is. 250 00:10:38,140 --> 00:10:40,100 Because so much processing has to occur in your 251 00:10:40,100 --> 00:10:41,030 brain to get there. 252 00:10:41,030 --> 00:10:42,590 Even though it seems instantaneous 253 00:10:42,590 --> 00:10:43,840 and trivial to you. 254 00:10:46,380 --> 00:10:48,400 It's instantaneous and trivial to you because your brain is 255 00:10:48,400 --> 00:10:52,050 so brilliant that it accomplishes it. 256 00:10:55,570 --> 00:10:58,170 Now, there are things out there in the world like 257 00:10:58,170 --> 00:11:00,130 animals that occur naturally. 258 00:11:00,130 --> 00:11:02,440 Because they're from an evolutionary tree, they share 259 00:11:02,440 --> 00:11:03,960 a lot of shapes. 260 00:11:03,960 --> 00:11:06,660 And there's things out there that are not living, either 261 00:11:06,660 --> 00:11:08,790 that occur like the moon and the mountain-- they're out 262 00:11:08,790 --> 00:11:09,800 there sitting-- 263 00:11:09,800 --> 00:11:12,700 or what we call manufactured objects, things like locks, 264 00:11:12,700 --> 00:11:17,330 pencils, motorcycles, bulbs, things that humans have made. 265 00:11:17,330 --> 00:11:20,620 And, of course, humans make shapes as they need to 266 00:11:20,620 --> 00:11:21,730 construct things. 267 00:11:21,730 --> 00:11:24,920 They're not constrained by evolutionary forces about what 268 00:11:24,920 --> 00:11:25,960 shape something is. 269 00:11:25,960 --> 00:11:29,610 We make a shape as we need it. 270 00:11:29,610 --> 00:11:32,220 But it was still an amazing discovery in the 1980s that 271 00:11:32,220 --> 00:11:35,020 they found individual patients who lost the ability to 272 00:11:35,020 --> 00:11:38,640 recognize things and various specific categories. 273 00:11:38,640 --> 00:11:42,220 This seems so much like old style, silly phrenology. 274 00:11:42,220 --> 00:11:45,450 That I can tell you, my colleagues sort of make fun of 275 00:11:45,450 --> 00:11:48,990 me when I told them people in my field were following this. 276 00:11:48,990 --> 00:11:53,190 So they found patients who could define by pictures 277 00:11:53,190 --> 00:11:56,350 manufactured objects, things like pencils, or typewriters, 278 00:11:56,350 --> 00:11:57,290 or computers. 279 00:11:57,290 --> 00:12:01,350 But they couldn't identify foods or animals. 280 00:12:01,350 --> 00:12:03,700 And then they found patients just the opposite who could 281 00:12:03,700 --> 00:12:07,870 identify foods and animals but not manufactured objects. 282 00:12:07,870 --> 00:12:09,200 So that's really weird. 283 00:12:09,200 --> 00:12:12,870 That's as if you had organized in your brain the manufactured 284 00:12:12,870 --> 00:12:14,380 section here like in a supermarket. 285 00:12:14,380 --> 00:12:15,520 And here's the animal section. 286 00:12:15,520 --> 00:12:17,560 And here's the fruit section. 287 00:12:17,560 --> 00:12:19,660 Really, is that how our mind is organized, like a 288 00:12:19,660 --> 00:12:21,690 supermarket? 289 00:12:21,690 --> 00:12:24,390 But then there were some exceptions to these. 290 00:12:24,390 --> 00:12:25,740 And there are the exceptions that helped us 291 00:12:25,740 --> 00:12:26,650 inform us on the rules. 292 00:12:26,650 --> 00:12:29,740 So here's some patients who are really good at identifying 293 00:12:29,740 --> 00:12:32,740 manufactured things-- again, pencils, things like that-- 294 00:12:32,740 --> 00:12:35,126 bad at foods and animals. 295 00:12:35,126 --> 00:12:36,230 But now think about this. 296 00:12:36,230 --> 00:12:39,030 They were good on body parts. 297 00:12:39,030 --> 00:12:41,290 How were they good on body parts when they were bad at 298 00:12:41,290 --> 00:12:41,830 foods and animals? 299 00:12:41,830 --> 00:12:44,950 Body parts are natural, right? 300 00:12:44,950 --> 00:12:47,750 And they were bad a musical instruments even though they 301 00:12:47,750 --> 00:12:50,310 were good on other manufactured things like 302 00:12:50,310 --> 00:12:52,850 pencils and computers. 303 00:12:52,850 --> 00:12:54,910 So these were two wrong things. 304 00:12:54,910 --> 00:12:57,270 And I'm going to try to convince in a moment that the 305 00:12:57,270 --> 00:13:00,270 way we now understand this is they're good at body parts 306 00:13:00,270 --> 00:13:02,750 because we know how to use our body. 307 00:13:02,750 --> 00:13:06,160 And they're bad at musical instruments because musical 308 00:13:06,160 --> 00:13:10,500 instruments look an awful lot like one another just like 309 00:13:10,500 --> 00:13:13,280 four-legged animals look a lot like one another. 310 00:13:13,280 --> 00:13:15,810 That's a funny category for us if we start to divide up 311 00:13:15,810 --> 00:13:17,330 instruments. 312 00:13:17,330 --> 00:13:23,260 So the problem is not so much one of natural versus 313 00:13:23,260 --> 00:13:24,610 unnatural things. 314 00:13:24,610 --> 00:13:27,960 It's things that we know through vision versus things 315 00:13:27,960 --> 00:13:30,690 that we know through physical action and use. 316 00:13:30,690 --> 00:13:31,640 And here's another example. 317 00:13:31,640 --> 00:13:37,970 The patients who are bad at objects that we use every day, 318 00:13:37,970 --> 00:13:40,420 like pencils and stuff like that, were pretty good on 319 00:13:40,420 --> 00:13:43,320 things like billboards and mountains. 320 00:13:43,320 --> 00:13:47,140 Now only in science fiction movies do you have creatures 321 00:13:47,140 --> 00:13:48,770 big enough that they're picking up billboards and 322 00:13:48,770 --> 00:13:50,400 throwing it at helicopters from the military. 323 00:13:50,400 --> 00:13:51,940 You see that all the time. 324 00:13:51,940 --> 00:13:52,530 You have the big creature. 325 00:13:52,530 --> 00:13:53,800 And they pick it up, and they hurl it. 326 00:13:53,800 --> 00:13:54,410 OK. 327 00:13:54,410 --> 00:14:00,110 So we don't mostly pick up huge things like mountains and 328 00:14:00,110 --> 00:14:02,380 large outdoor objects like flag poles. 329 00:14:02,380 --> 00:14:06,240 They're not things that we pick up and use. 330 00:14:06,240 --> 00:14:09,320 So it seems like the principle of what's good or bad is more 331 00:14:09,320 --> 00:14:13,080 about how we experience things through sight or through 332 00:14:13,080 --> 00:14:14,940 physical action. 333 00:14:14,940 --> 00:14:17,280 So how do we know things in the world through visual 334 00:14:17,280 --> 00:14:19,410 experience? 335 00:14:19,410 --> 00:14:21,160 Unless we're alligator wrestlers, we don't get that 336 00:14:21,160 --> 00:14:23,540 near that many animals. 337 00:14:23,540 --> 00:14:26,660 And most of us have other things that we use all the 338 00:14:26,660 --> 00:14:29,860 time, like bulbs, and pencils, and things like that. 339 00:14:29,860 --> 00:14:31,350 And evidence for that was this. 340 00:14:31,350 --> 00:14:34,190 They put humans inside a scanner and looked at their 341 00:14:34,190 --> 00:14:37,440 brains as they named either line drawings or words. 342 00:14:37,440 --> 00:14:38,960 So let's think of words. 343 00:14:38,960 --> 00:14:42,730 So it's just words, and you're naming things like elephant 344 00:14:42,730 --> 00:14:43,540 and tiger-- 345 00:14:43,540 --> 00:14:44,600 that's the animal-- 346 00:14:44,600 --> 00:14:47,670 or tools that you use, like pliers or hammer. 347 00:14:47,670 --> 00:14:49,330 Visually, they're words. 348 00:14:49,330 --> 00:14:52,130 But what happens in the brain as you're naming animals? 349 00:14:52,130 --> 00:14:54,090 It seems like you turn on the visual parts of 350 00:14:54,090 --> 00:14:54,800 your brain a lot. 351 00:14:54,800 --> 00:14:56,170 There's no animal in there. 352 00:14:56,170 --> 00:14:56,980 There's not even a picture of an animal. 353 00:14:56,980 --> 00:15:00,630 It's just the word elephant or the word cat. 354 00:15:00,630 --> 00:15:02,860 What happens when you're naming tools? 355 00:15:02,860 --> 00:15:05,820 In the left hemisphere, we see turned on an area here that's 356 00:15:05,820 --> 00:15:11,240 involved in visual motion, and here, in physical action of 357 00:15:11,240 --> 00:15:13,740 moving things in the world. 358 00:15:13,740 --> 00:15:15,900 All you're doing is naming words. 359 00:15:15,900 --> 00:15:20,050 But it's as if the knowledge for naming them is located in 360 00:15:20,050 --> 00:15:23,560 the part of your brain that uses that information. 361 00:15:23,560 --> 00:15:27,410 If there's things I recognize by sight, the abstract 362 00:15:27,410 --> 00:15:30,350 knowledge about those things is near my visual system. 363 00:15:30,350 --> 00:15:34,360 If there's things I recognize by action, using them, the 364 00:15:34,360 --> 00:15:37,100 abstract knowledge of that is located in your brain near 365 00:15:37,100 --> 00:15:39,710 parts of your brain that move things and pick up things. 366 00:15:39,710 --> 00:15:41,760 So all of a sudden, it makes sense that you can get 367 00:15:41,760 --> 00:15:43,360 separation in these forms of knowledge. 368 00:15:43,360 --> 00:15:46,310 Because they reside in your brain near the parts of your 369 00:15:46,310 --> 00:15:49,400 brain that use them and communicate with them. 370 00:15:49,400 --> 00:15:51,160 So again, this idea that if it's a [INAUDIBLE] like a 371 00:15:51,160 --> 00:15:54,775 scissors, your knowledge about scissors will reside in the 372 00:15:54,775 --> 00:15:57,300 parts of the brain that act upon scissors. 373 00:15:57,300 --> 00:16:01,540 If it's something like a bird that you mostly see, knowledge 374 00:16:01,540 --> 00:16:04,540 about that bird, not just how it looks, but everything, will 375 00:16:04,540 --> 00:16:08,120 reside in parts of the brain that are focused on vision. 376 00:16:08,120 --> 00:16:09,940 So it's as if your knowledge is moved to the part of the 377 00:16:09,940 --> 00:16:14,040 brain that interacts with the form of knowledge. 378 00:16:14,040 --> 00:16:15,360 So now let's talk about faces. 379 00:16:15,360 --> 00:16:19,170 Faces are a huge thing for us. 380 00:16:19,170 --> 00:16:22,370 There's at least two huge things we do with faces. 381 00:16:22,370 --> 00:16:26,140 We recognize who people are and what their moods are, 382 00:16:26,140 --> 00:16:29,760 angry, happy, nice, and so on. 383 00:16:29,760 --> 00:16:31,500 So here's one person. 384 00:16:31,500 --> 00:16:32,660 Here's another person. 385 00:16:32,660 --> 00:16:34,870 When I first used this picture, he wasn't a governor. 386 00:16:34,870 --> 00:16:35,570 He was a movie star. 387 00:16:35,570 --> 00:16:37,690 And now he's an ex-governor. 388 00:16:37,690 --> 00:16:39,250 And you have the problem that you have to 389 00:16:39,250 --> 00:16:40,630 recognize a lot of people. 390 00:16:40,630 --> 00:16:42,440 Because you have all your classmates, and friends, and 391 00:16:42,440 --> 00:16:44,930 family members, and a lot of people out there. 392 00:16:44,930 --> 00:16:46,670 And not only that, you have to recognize the various 393 00:16:46,670 --> 00:16:48,940 expressions they have, which are terribly important for how 394 00:16:48,940 --> 00:16:53,900 we communicate with people moment to moment all the time. 395 00:16:53,900 --> 00:16:56,120 So we could say with faces, our big job is who are we 396 00:16:56,120 --> 00:16:57,260 looking at. 397 00:16:57,260 --> 00:17:01,420 A friend, or foe, somebody loved, somebody we don't know. 398 00:17:01,420 --> 00:17:02,600 Who is that person? 399 00:17:02,600 --> 00:17:04,609 And then what's the expression that we can 400 00:17:04,609 --> 00:17:05,470 read from their face? 401 00:17:05,470 --> 00:17:08,140 That's a huge part of our lives as social animals, as 402 00:17:08,140 --> 00:17:11,300 people who interact with other people. 403 00:17:11,300 --> 00:17:16,460 So you saw a film last time of a patient with prosopagnosia. 404 00:17:16,460 --> 00:17:18,940 Your book, this time, talks about a Dr. P. He's the man 405 00:17:18,940 --> 00:17:20,829 who mistook his wife for a hat. 406 00:17:20,829 --> 00:17:23,810 So he has bigger problems in vision than simply faces. 407 00:17:23,810 --> 00:17:25,500 But faces are very impressive. 408 00:17:25,500 --> 00:17:28,120 He fails to recognize his students by their face. 409 00:17:28,120 --> 00:17:30,020 But he can recognize them by their voice, 410 00:17:30,020 --> 00:17:31,450 modality-specific. 411 00:17:31,450 --> 00:17:34,080 His general vision is OK. 412 00:17:34,080 --> 00:17:37,840 When Oliver Sacks visited him in his house, he tries to 413 00:17:37,840 --> 00:17:40,950 reach out his hand and took hold of his wife's head, tried 414 00:17:40,950 --> 00:17:42,585 to lift it off to put it on. 415 00:17:42,585 --> 00:17:46,880 He had apparently mistaken his wife for a hat. 416 00:17:46,880 --> 00:17:49,440 His wife looked as if she was used to such things. 417 00:17:49,440 --> 00:17:51,260 You can see the head and the hat, they're kind of close. 418 00:17:51,260 --> 00:17:53,560 But not if you have typical vision. 419 00:17:53,560 --> 00:17:56,490 He might pat the head of water hydrants and parking meters 420 00:17:56,490 --> 00:17:59,740 mistaking them for the heads of children. 421 00:17:59,740 --> 00:18:01,190 There's a little bit of logic. 422 00:18:01,190 --> 00:18:03,315 But it's pretty wrong what he sees. 423 00:18:03,315 --> 00:18:04,765 And it's pretty meaningless to him. 424 00:18:07,380 --> 00:18:09,850 So let me show you a film of an example. 425 00:18:09,850 --> 00:18:11,100 You saw one last time. 426 00:18:13,810 --> 00:18:14,750 So let me say a word about this. 427 00:18:14,750 --> 00:18:16,920 Imagine that if you couldn't recognize people 428 00:18:16,920 --> 00:18:17,770 as you walked up. 429 00:18:17,770 --> 00:18:20,960 So much of how we recognize people-- we don't think about 430 00:18:20,960 --> 00:18:22,930 this, because we instantly, easily recognize 431 00:18:22,930 --> 00:18:24,050 those we know well-- 432 00:18:24,050 --> 00:18:26,040 is by their faces. 433 00:18:26,040 --> 00:18:28,390 So I want to say a couple of things. 434 00:18:28,390 --> 00:18:29,990 Usually there's posterior cortical lesions 435 00:18:29,990 --> 00:18:31,710 like in this woman. 436 00:18:31,710 --> 00:18:34,800 I knew one man who was a Unitarian minister, who I 437 00:18:34,800 --> 00:18:36,760 worked with, actually, a couple blocks away here, 438 00:18:36,760 --> 00:18:39,120 He went up to Dartmouth for the winter carnival. 439 00:18:39,120 --> 00:18:40,960 He came back in a small Volkswagen. 440 00:18:40,960 --> 00:18:41,870 It turned over turned over on the ice. 441 00:18:41,870 --> 00:18:45,505 He had a huge brain injury and became prosopagnosic. 442 00:18:45,505 --> 00:18:47,900 He could only recognize his wife by asking her to wear a 443 00:18:47,900 --> 00:18:49,700 yellow bow in her hair. 444 00:18:49,700 --> 00:18:50,660 Because otherwise he couldn't pick her 445 00:18:50,660 --> 00:18:52,370 out from other people. 446 00:18:52,370 --> 00:18:55,740 When he went down the street and passed his brother, he 447 00:18:55,740 --> 00:18:57,410 completely failed to recognize him. 448 00:18:57,410 --> 00:18:58,510 Then the brother spoke. 449 00:18:58,510 --> 00:18:59,420 Then he recognized him. 450 00:18:59,420 --> 00:19:01,740 And he said-- and this was his subjective experience-- 451 00:19:01,740 --> 00:19:03,400 because you wonder what do these people 452 00:19:03,400 --> 00:19:05,670 feel like they see. 453 00:19:05,670 --> 00:19:08,810 He said that what it felt like for his brother was, do you 454 00:19:08,810 --> 00:19:11,340 when somebody has some bad handwriting, and you can't 455 00:19:11,340 --> 00:19:12,480 make it out at all? 456 00:19:12,480 --> 00:19:13,830 And then somebody tells you what it is. 457 00:19:13,830 --> 00:19:15,280 And you go, oh yes. 458 00:19:15,280 --> 00:19:16,260 That's that word. 459 00:19:16,260 --> 00:19:17,730 Any now you see it. 460 00:19:17,730 --> 00:19:20,120 He said, that's what it felt like as he heard his brother's 461 00:19:20,120 --> 00:19:22,990 voice and realized it was his brother. 462 00:19:22,990 --> 00:19:24,320 It's hard to know how to relate these things. 463 00:19:24,320 --> 00:19:27,180 But the ability to recognize a person is completely wiped out 464 00:19:27,180 --> 00:19:28,610 of these individuals. 465 00:19:28,610 --> 00:19:32,270 In the last six or seven years, something else has been 466 00:19:32,270 --> 00:19:32,570 discovered. 467 00:19:32,570 --> 00:19:34,570 Now let me tell you a word about this. 468 00:19:34,570 --> 00:19:37,560 Instead of people with acute lesions that they got because 469 00:19:37,560 --> 00:19:38,810 of a brain injury. 470 00:19:38,810 --> 00:19:42,440 It turns out there's a couple percent of our population 471 00:19:42,440 --> 00:19:45,590 that's really bad at recognizing faces, not the 472 00:19:45,590 --> 00:19:47,630 occasional social embarrassment that many of us 473 00:19:47,630 --> 00:19:50,880 have when we see somebody, we know we should know them, but 474 00:19:50,880 --> 00:19:53,560 they're really, really, really bad. 475 00:19:53,560 --> 00:19:56,250 There's websites you can go to that let you test yourself. 476 00:19:56,250 --> 00:19:58,570 Because researchers want you to work with them if you're 477 00:19:58,570 --> 00:19:59,800 one of them. 478 00:19:59,800 --> 00:20:02,500 It's about 1% of the population. 479 00:20:02,500 --> 00:20:05,200 They're really, really, really bad. 480 00:20:05,200 --> 00:20:06,480 There was one woman described as, she says, 481 00:20:06,480 --> 00:20:07,690 they can't watch movies. 482 00:20:07,690 --> 00:20:09,070 Because all the characters look pretty 483 00:20:09,070 --> 00:20:12,320 much the same to them. 484 00:20:12,320 --> 00:20:13,570 You can imagine that. 485 00:20:16,050 --> 00:20:19,600 One parent who has this problem, really terrible at 486 00:20:19,600 --> 00:20:22,480 faces by formal testing, says that when her kid comes out of 487 00:20:22,480 --> 00:20:26,800 school, her own kid, if he is not wearing the clothes that 488 00:20:26,800 --> 00:20:29,270 she knows he's wearing, she can't pick him out from the 489 00:20:29,270 --> 00:20:31,300 other children very easily. 490 00:20:31,300 --> 00:20:33,390 And these are not people with big brain injuries. 491 00:20:33,390 --> 00:20:35,820 These are people who have some unusual difficulty in 492 00:20:35,820 --> 00:20:36,870 recognizing faces. 493 00:20:36,870 --> 00:20:40,440 So in a classroom this size, there easily 494 00:20:40,440 --> 00:20:43,200 could be one of you. 495 00:20:43,200 --> 00:20:44,640 We don't understand what that is. 496 00:20:44,640 --> 00:20:46,740 It's not a brain injury. 497 00:20:46,740 --> 00:20:49,490 Just like some of us can't carry a tune, some individuals 498 00:20:49,490 --> 00:20:54,390 are really terrible at recognizing faces, really bad. 499 00:20:54,390 --> 00:20:56,560 So there's a lot of research into that to understand what 500 00:20:56,560 --> 00:20:57,740 that reflects. 501 00:20:57,740 --> 00:20:59,870 So let me tell you what we do understand about the neural 502 00:20:59,870 --> 00:21:02,680 circuitry in the typical brain for recognizing a face of a 503 00:21:02,680 --> 00:21:04,820 loved one, a person that you care about. 504 00:21:04,820 --> 00:21:06,960 So this is the fusiform gyrus. 505 00:21:06,960 --> 00:21:09,060 It's a structure in the back of the brain that extends from 506 00:21:09,060 --> 00:21:11,170 the occipital into the temporal lobes. 507 00:21:11,170 --> 00:21:13,620 And that's an anatomical description of this region. 508 00:21:13,620 --> 00:21:18,540 Within that region, there's a functional area that seems 509 00:21:18,540 --> 00:21:20,660 very important for face perception. 510 00:21:20,660 --> 00:21:22,930 And Nancy Kanwisher, who's in our department, pretty much 511 00:21:22,930 --> 00:21:25,900 discovered this specific functional area in the typical 512 00:21:25,900 --> 00:21:27,250 human brain. 513 00:21:27,250 --> 00:21:30,340 And so she did experiments where she would present things 514 00:21:30,340 --> 00:21:32,110 like faces or objects. 515 00:21:35,700 --> 00:21:37,870 In this picture, left is right, and right is left. 516 00:21:37,870 --> 00:21:40,270 There's a spot in the fusiform cortex that has 517 00:21:40,270 --> 00:21:41,580 this following property. 518 00:21:41,580 --> 00:21:42,280 Here's faces. 519 00:21:42,280 --> 00:21:43,070 That turns on. 520 00:21:43,070 --> 00:21:45,065 Here's objects which have similar properties. 521 00:21:45,065 --> 00:21:47,530 It has a lot of visual information like a face. 522 00:21:47,530 --> 00:21:48,740 But it's not a face. 523 00:21:48,740 --> 00:21:51,420 It's part of the brain region not so interested, faces, 524 00:21:51,420 --> 00:21:53,310 objects, faces, objects. 525 00:21:53,310 --> 00:21:54,970 So whenever faces come on-- 526 00:21:54,970 --> 00:21:56,860 this is, by our understanding-- the first part 527 00:21:56,860 --> 00:21:59,630 of your brain that says, I'm looking at a face. 528 00:21:59,630 --> 00:22:02,130 Up until then, it's just treated like other stuff. 529 00:22:02,130 --> 00:22:04,710 This is the first part of your brain that recognizes, I'm 530 00:22:04,710 --> 00:22:05,870 looking at a face. 531 00:22:05,870 --> 00:22:08,890 I'm starting to identify who I'm looking at and what 532 00:22:08,890 --> 00:22:11,950 feelings they might have by their expression. 533 00:22:11,950 --> 00:22:14,970 And Nancy and her colleagues did all kinds of very clever 534 00:22:14,970 --> 00:22:18,450 experiments to show the properties of this. 535 00:22:18,450 --> 00:22:19,450 Let me pick one. 536 00:22:19,450 --> 00:22:21,970 You could say, well, it's not about faces. 537 00:22:21,970 --> 00:22:23,420 But faces are about humans. 538 00:22:23,420 --> 00:22:25,550 Maybe it's a part of the brain that tells you when there's a 539 00:22:25,550 --> 00:22:26,970 human around you. 540 00:22:26,970 --> 00:22:29,870 So they compared faces versus hands. 541 00:22:29,870 --> 00:22:30,670 Here's hands. 542 00:22:30,670 --> 00:22:32,060 This part of the brain is not that interested. 543 00:22:32,060 --> 00:22:33,900 Faces, hands, faces, hands. 544 00:22:33,900 --> 00:22:35,770 You see every time it moves to faces, this part of the brain 545 00:22:35,770 --> 00:22:37,280 gets very strongly engaged. 546 00:22:37,280 --> 00:22:42,330 It's very much about faces by many research studies. 547 00:22:42,330 --> 00:22:44,030 So let me tell you a little bit about what we understand 548 00:22:44,030 --> 00:22:45,750 about faces in terms of development 549 00:22:45,750 --> 00:22:46,430 and things like that. 550 00:22:46,430 --> 00:22:48,920 Because faces are such a big part of our lives from the 551 00:22:48,920 --> 00:22:50,420 first few moments we're born. 552 00:22:50,420 --> 00:22:55,870 In fact, a colleague of mine, Pawan Sinha, did a kind of a 553 00:22:55,870 --> 00:22:58,760 biographical research study that was on the front page of 554 00:22:58,760 --> 00:23:02,030 The New York Times and earned MIT faculty the continuing 555 00:23:02,030 --> 00:23:03,560 names of being Frankenstein faculty. 556 00:23:03,560 --> 00:23:05,240 There was a number of faculty. 557 00:23:05,240 --> 00:23:08,400 And what he did, kind of very cleverly, was he put on his 558 00:23:08,400 --> 00:23:12,360 newborn infant's head a little camera. 559 00:23:12,360 --> 00:23:14,150 And he said, if I leave it on there and 560 00:23:14,150 --> 00:23:15,240 record it all the time-- 561 00:23:15,240 --> 00:23:16,950 and apparently there was some debate with his wife whether 562 00:23:16,950 --> 00:23:17,770 he was allowed to do this. 563 00:23:17,770 --> 00:23:18,410 But they checked it out. 564 00:23:18,410 --> 00:23:21,640 It seemed OK by the pediatrician. 565 00:23:21,640 --> 00:23:24,020 He said, if I have the camera on the infant's head, I can 566 00:23:24,020 --> 00:23:27,050 see what the infant's experience is like moment to 567 00:23:27,050 --> 00:23:30,180 moment in the first months of its life. 568 00:23:30,180 --> 00:23:34,350 And I can also play with the video so that it has, roughly 569 00:23:34,350 --> 00:23:39,540 speaking, the properties of the infant's visual system, 570 00:23:39,540 --> 00:23:42,955 which is it can't see very far after its birth. 571 00:23:42,955 --> 00:23:45,070 They can only see very close by, and not that well. 572 00:23:45,070 --> 00:23:46,333 Over the next several months-- we'll talk about 573 00:23:46,333 --> 00:23:46,910 this later in class-- 574 00:23:46,910 --> 00:23:49,860 he gets better and better at seeing at a distance. 575 00:23:49,860 --> 00:23:53,230 So here's the infant sitting in his or her crib. 576 00:23:53,230 --> 00:23:56,000 And this video makes incredibly clear, beautifully 577 00:23:56,000 --> 00:23:58,900 and fascinatingly clear, something that I never thought 578 00:23:58,900 --> 00:24:02,140 of until Pawan did this study, this examination. 579 00:24:02,140 --> 00:24:04,800 So the infant sitting there, it can't move very much. 580 00:24:04,800 --> 00:24:07,480 It can't go very many places as a newborn infant. 581 00:24:07,480 --> 00:24:08,410 So what does it see? 582 00:24:08,410 --> 00:24:12,630 What gets close enough to it to be visible to the infant? 583 00:24:12,630 --> 00:24:14,430 People's faces. 584 00:24:14,430 --> 00:24:16,825 Because all the other cute things in the nursery, all the 585 00:24:16,825 --> 00:24:19,070 other things that are there, they are too far or too blurry 586 00:24:19,070 --> 00:24:21,410 for the infant to process almost at all. 587 00:24:21,410 --> 00:24:24,290 Almost the only thing that happens is the parent, the 588 00:24:24,290 --> 00:24:27,430 grandparent, the siblings, the friends that come over and go, 589 00:24:27,430 --> 00:24:28,610 what a cute baby. 590 00:24:28,610 --> 00:24:29,870 Baby, baby, baby, baby. 591 00:24:29,870 --> 00:24:32,190 The face comes in. 592 00:24:32,190 --> 00:24:34,430 The person's done, gone. 593 00:24:34,430 --> 00:24:36,350 Now you're just sitting in a world of blur. 594 00:24:36,350 --> 00:24:38,790 Here comes another face. 595 00:24:38,790 --> 00:24:41,090 So besides certain issues related to perhaps the 596 00:24:41,090 --> 00:24:43,430 feeding, the only thing the infant sees are 597 00:24:43,430 --> 00:24:45,660 faces all the time. 598 00:24:45,660 --> 00:24:49,460 So it's a very important social cue of who it's 599 00:24:49,460 --> 00:24:50,600 interacting with and what's out there. 600 00:24:50,600 --> 00:24:52,680 And it's almost the only one available to it. 601 00:24:52,680 --> 00:24:56,330 So psychologists have known for some time that if you show 602 00:24:56,330 --> 00:24:59,850 a very young infant a face versus something like an 603 00:24:59,850 --> 00:25:02,430 object, like a car or anything like that, they're much more 604 00:25:02,430 --> 00:25:04,980 interested in faces if you put them next to each other where 605 00:25:04,980 --> 00:25:06,440 the infant can see them. 606 00:25:06,440 --> 00:25:08,330 And they've been saying, well, is the brain 607 00:25:08,330 --> 00:25:10,130 born to process faces? 608 00:25:10,130 --> 00:25:10,770 And it might be. 609 00:25:10,770 --> 00:25:12,100 And I'll show you evidence to suggest in some 610 00:25:12,100 --> 00:25:13,510 general sense it is. 611 00:25:13,510 --> 00:25:16,290 What is that infant's brain drawn to? 612 00:25:16,290 --> 00:25:19,100 What does it find fascinating to learn about in the world? 613 00:25:19,100 --> 00:25:22,370 And so they notice that one thing about a face is in terms 614 00:25:22,370 --> 00:25:27,720 of features, eyes, nose, mouth, top-heavy. 615 00:25:27,720 --> 00:25:29,800 Because we have two eyes, and everything else is one and 616 00:25:29,800 --> 00:25:31,470 one, the nose and the mouth. 617 00:25:31,470 --> 00:25:33,750 So here you can move the features like this. 618 00:25:33,750 --> 00:25:36,020 And it turns out not only are infants more interested in 619 00:25:36,020 --> 00:25:38,300 this kind of face than this-- and they know that because 620 00:25:38,300 --> 00:25:40,390 they'll put the two up, and they'll measure how long the 621 00:25:40,390 --> 00:25:43,760 infant looks at one versus the other, which is interesting. 622 00:25:43,760 --> 00:25:44,730 And the infant picks this one. 623 00:25:44,730 --> 00:25:45,590 But get a load of this? 624 00:25:45,590 --> 00:25:48,540 The infant also picks this one versus this, this one versus 625 00:25:48,540 --> 00:25:50,200 this, and this one versus this. 626 00:25:50,200 --> 00:25:52,710 Now these look very little like a face. 627 00:25:52,710 --> 00:25:55,490 But they're top-heavy. 628 00:25:55,490 --> 00:25:59,500 It's as if maybe the infant's brain to start with, maybe, 629 00:25:59,500 --> 00:26:02,380 looks for some interesting, top-heavy things and that 630 00:26:02,380 --> 00:26:04,640 pulls it into the world of faces. 631 00:26:04,640 --> 00:26:06,500 Here's some more experiments like that. 632 00:26:06,500 --> 00:26:12,040 So here's an upside down, right-side up. 633 00:26:12,040 --> 00:26:13,960 Baby looks more at this kind of face. 634 00:26:13,960 --> 00:26:14,240 OK. 635 00:26:14,240 --> 00:26:15,790 You could say, well, that's a normal face. 636 00:26:15,790 --> 00:26:17,840 But it's also top-heavy. 637 00:26:17,840 --> 00:26:21,900 Then they'd make these kind of scary-looking faces. 638 00:26:21,900 --> 00:26:24,860 And now the baby, even though these are nothing like a face 639 00:26:24,860 --> 00:26:28,540 the baby ever sees, it still likes this one 640 00:26:28,540 --> 00:26:31,260 because it's top-heavy. 641 00:26:31,260 --> 00:26:32,740 Now how about this one? 642 00:26:32,740 --> 00:26:33,930 This is like a face they see. 643 00:26:33,930 --> 00:26:36,110 This is a really weird face. 644 00:26:36,110 --> 00:26:36,490 Right? 645 00:26:36,490 --> 00:26:38,020 They'll never see a face like this except in this 646 00:26:38,020 --> 00:26:39,160 experiment. 647 00:26:39,160 --> 00:26:40,150 Top-heavy. 648 00:26:40,150 --> 00:26:41,180 Top-heavy. 649 00:26:41,180 --> 00:26:43,700 And now the infant looks at both of them with equal 650 00:26:43,700 --> 00:26:45,970 interest and delight. 651 00:26:45,970 --> 00:26:49,860 So that's a very clever experiment to suggest that the 652 00:26:49,860 --> 00:26:53,500 infant's mind is looking for top-heavy things. 653 00:26:53,500 --> 00:26:55,040 And you could say, is it really top-heavy? 654 00:26:55,040 --> 00:26:58,260 Or Is that what the infant's mind and brain can look for? 655 00:26:58,260 --> 00:26:59,480 And it goes with faces. 656 00:26:59,480 --> 00:27:01,830 And evolution picked that. 657 00:27:01,830 --> 00:27:03,850 It's hard to know how to think about these things. 658 00:27:03,850 --> 00:27:06,500 But it looks like the top-heaviness draws an infant 659 00:27:06,500 --> 00:27:08,960 to be fascinated by faces. 660 00:27:08,960 --> 00:27:12,880 And luckily, you don't get many faces like this to 661 00:27:12,880 --> 00:27:16,920 confuse you in the real world. 662 00:27:16,920 --> 00:27:18,120 Another thing that people have studied a lot 663 00:27:18,120 --> 00:27:21,590 about faces is this. 664 00:27:21,590 --> 00:27:23,040 They use the word configural. 665 00:27:23,040 --> 00:27:25,230 The relations among the parts are more important than the 666 00:27:25,230 --> 00:27:26,230 parts themselves. 667 00:27:26,230 --> 00:27:27,540 So I need a volunteer in their seat. 668 00:27:27,540 --> 00:27:29,850 And this is going to be really easy if you know the alphabet. 669 00:27:32,380 --> 00:27:35,270 You have to put up your hand and help me out. 670 00:27:35,270 --> 00:27:35,490 OK. 671 00:27:35,490 --> 00:27:36,240 Thank you very much. 672 00:27:36,240 --> 00:27:38,410 I'm going to describe to you a letter by its features. 673 00:27:38,410 --> 00:27:39,190 OK? 674 00:27:39,190 --> 00:27:41,470 It has a big line at the top. 675 00:27:41,470 --> 00:27:42,510 And in the middle, there's a line that 676 00:27:42,510 --> 00:27:44,150 goes down to the bottom. 677 00:27:44,150 --> 00:27:45,140 What's the letter? 678 00:27:45,140 --> 00:27:45,610 AUDIENCE: T. 679 00:27:45,610 --> 00:27:45,980 PROFESSOR: Awesome. 680 00:27:45,980 --> 00:27:46,430 OK. 681 00:27:46,430 --> 00:27:47,490 Featural description. 682 00:27:47,490 --> 00:27:50,600 Now I'm going to describe to you a super famous movie star. 683 00:27:50,600 --> 00:27:53,790 And this person has two eyes to the left and to the right, 684 00:27:53,790 --> 00:27:56,150 a nose right below that, and a mouth right below that. 685 00:27:56,150 --> 00:27:59,450 And who is it? 686 00:27:59,450 --> 00:28:02,290 Angelina Jolie. 687 00:28:02,290 --> 00:28:03,390 So what's my point here? 688 00:28:03,390 --> 00:28:06,210 It's the stuff that helps us in many things, like the 689 00:28:06,210 --> 00:28:06,770 letters-- thank you. 690 00:28:06,770 --> 00:28:09,240 That was excellent. 691 00:28:09,240 --> 00:28:11,010 We can describe those by the parts. 692 00:28:11,010 --> 00:28:12,560 And the parts pretty much define the whole. 693 00:28:12,560 --> 00:28:13,640 That's not true for faces. 694 00:28:13,640 --> 00:28:15,930 It really is the precise relations between eyes, and 695 00:28:15,930 --> 00:28:17,210 nose, and mouth that tell us. 696 00:28:17,210 --> 00:28:20,120 And there's an experiment that shows this in a very empirical 697 00:28:20,120 --> 00:28:21,030 direct way. 698 00:28:21,030 --> 00:28:22,870 So they would show people a face like this with a 699 00:28:22,870 --> 00:28:25,420 particular nose or a house like this with 700 00:28:25,420 --> 00:28:27,440 a particular door. 701 00:28:27,440 --> 00:28:30,000 And then they would test your memory for that nose or that 702 00:28:30,000 --> 00:28:35,910 door by itself as features or with the whole face or a whole 703 00:28:35,910 --> 00:28:37,840 house present. 704 00:28:37,840 --> 00:28:40,920 And here's what happens for people's performance. 705 00:28:40,920 --> 00:28:44,570 The nose by itself, the door by itself, the nose when you 706 00:28:44,570 --> 00:28:46,370 see the whole picture, which could be his nose. 707 00:28:46,370 --> 00:28:47,650 It could be another nose. 708 00:28:47,650 --> 00:28:48,290 Here's the door. 709 00:28:48,290 --> 00:28:50,310 It could be that door or a different door. 710 00:28:50,310 --> 00:28:52,520 And here's what happens in performance. 711 00:28:52,520 --> 00:28:56,560 If it's houses, people are good for doors, about the same 712 00:28:56,560 --> 00:28:59,880 whether they've identified the door by itself or the door in 713 00:28:59,880 --> 00:29:01,980 the context of the house. 714 00:29:01,980 --> 00:29:04,540 If it's noses, they were a lot better off 715 00:29:04,540 --> 00:29:06,100 seeing the entire face. 716 00:29:06,100 --> 00:29:10,080 It's as if how we analyzed even the parts of the face are 717 00:29:10,080 --> 00:29:13,110 really integrated immediately into the other 718 00:29:13,110 --> 00:29:13,890 aspects of the face. 719 00:29:13,890 --> 00:29:15,250 They don't stand alone. 720 00:29:15,250 --> 00:29:19,230 They're a part of a context all interacting together. 721 00:29:19,230 --> 00:29:22,080 Now here's something pretty striking and interesting. 722 00:29:22,080 --> 00:29:24,430 And we'll talk about some social implications of this at 723 00:29:24,430 --> 00:29:27,230 the end of the lecture. 724 00:29:27,230 --> 00:29:28,920 You can't ask infants many things. 725 00:29:28,920 --> 00:29:32,070 But you can record their behavior and learn some things 726 00:29:32,070 --> 00:29:34,360 about what their minds are representing and thinking. 727 00:29:34,360 --> 00:29:37,480 And here's how they test an infant at say six months of 728 00:29:37,480 --> 00:29:41,180 age, can't talk, can't walk, can't be instructed to push 729 00:29:41,180 --> 00:29:43,130 buttons or fill out surveys. 730 00:29:43,130 --> 00:29:45,720 How do they get inside the mind of what an infant knows? 731 00:29:45,720 --> 00:29:46,960 What they'll do is they'll show a face. 732 00:29:46,960 --> 00:29:51,080 And pretend they show this face all by itself. 733 00:29:51,080 --> 00:29:52,680 Infant looks for a little bit. 734 00:29:52,680 --> 00:29:55,240 Face disappears, and then they see the face they just saw and 735 00:29:55,240 --> 00:29:56,910 a new face. 736 00:29:56,910 --> 00:29:59,940 And infants who saw this face a few moments ago will spend 737 00:29:59,940 --> 00:30:04,580 more time looking at the new face than the old face. 738 00:30:04,580 --> 00:30:06,690 You can track where their eyes are. 739 00:30:06,690 --> 00:30:09,140 And that's the evidence they remember the face they saw 740 00:30:09,140 --> 00:30:11,580 before, because they selectively spend more time on 741 00:30:11,580 --> 00:30:12,830 the new face. 742 00:30:12,830 --> 00:30:15,230 And also they're hungry to look at the new face. 743 00:30:15,230 --> 00:30:17,350 I've seen this face, been there, done that. 744 00:30:17,350 --> 00:30:20,310 New face, check out this person. 745 00:30:20,310 --> 00:30:22,700 If you test them at six months, they'll have a 746 00:30:22,700 --> 00:30:26,360 preference for the new face. 747 00:30:26,360 --> 00:30:29,810 But if you show them two different monkeys-- 748 00:30:29,810 --> 00:30:32,110 and this might feel hard for you to tell these apart-- 749 00:30:32,110 --> 00:30:34,895 if you show them two different monkeys, they'll behave the 750 00:30:34,895 --> 00:30:38,440 same with monkey faces as they do with human faces. 751 00:30:38,440 --> 00:30:41,720 They'll prefer the novel face, which shows you they remember 752 00:30:41,720 --> 00:30:44,710 what face they saw before and want to look at the new face. 753 00:30:44,710 --> 00:30:49,330 And at six months, it's the same for humans and monkeys. 754 00:30:49,330 --> 00:30:51,070 And don't forget, most of these people are interacting a 755 00:30:51,070 --> 00:30:53,600 lot with adults, and siblings, and caretakers. 756 00:30:53,600 --> 00:30:57,330 Not many of them are hanging out with monkeys. 757 00:30:57,330 --> 00:31:01,520 They start to get much more accurate for human faces. 758 00:31:01,520 --> 00:31:04,420 The experience they have with human faces starts to make 759 00:31:04,420 --> 00:31:05,920 them much better that. 760 00:31:05,920 --> 00:31:08,490 At birth, faces from one species 761 00:31:08,490 --> 00:31:09,700 are as good as another. 762 00:31:09,700 --> 00:31:12,240 But with practice and experience, they become human 763 00:31:12,240 --> 00:31:14,030 face specialists. 764 00:31:14,030 --> 00:31:16,130 And they become much better at that. 765 00:31:16,130 --> 00:31:19,810 So it's not in our genes to be awesome at human faces. 766 00:31:19,810 --> 00:31:21,430 But there's something about faces. 767 00:31:21,430 --> 00:31:24,790 And then a lot depends on what we see. 768 00:31:24,790 --> 00:31:27,140 And we grow that part of our mind and brain. 769 00:31:27,140 --> 00:31:29,070 So here's a remarkable experiment, that you couldn't 770 00:31:29,070 --> 00:31:32,860 do with people, that was done with infant monkeys. 771 00:31:32,860 --> 00:31:36,030 These monkeys, after they were born, were given no exposure 772 00:31:36,030 --> 00:31:38,890 to faces, depending on the monkey, for six to 24 months. 773 00:31:38,890 --> 00:31:41,120 That's not quite completely true. 774 00:31:41,120 --> 00:31:43,430 Because at their birth, they saw some faces. 775 00:31:43,430 --> 00:31:45,090 So they couldn't start this experiment at the 776 00:31:45,090 --> 00:31:45,980 first moment of birth. 777 00:31:45,980 --> 00:31:49,650 But as soon as they could from birth, for six to 24 months. 778 00:31:49,650 --> 00:31:53,350 So when they were being fed, this is what they saw. 779 00:31:53,350 --> 00:31:55,010 They were given an interesting environment 780 00:31:55,010 --> 00:31:56,550 to see lots of stuff. 781 00:31:56,550 --> 00:31:57,730 And they would live in something like this. 782 00:31:57,730 --> 00:31:59,660 So they could not see another monkey. 783 00:31:59,660 --> 00:32:00,610 They could not see a human. 784 00:32:00,610 --> 00:32:02,710 They never saw a face except for the 785 00:32:02,710 --> 00:32:03,960 first moments of birth. 786 00:32:07,640 --> 00:32:11,790 Before they saw any living face on a monkey or a human, 787 00:32:11,790 --> 00:32:13,680 they would do these kinds of experiments that you just 788 00:32:13,680 --> 00:32:14,590 heard with infants. 789 00:32:14,590 --> 00:32:18,030 And they would show that these monkeys would preferentially 790 00:32:18,030 --> 00:32:21,040 look at faces, both human faces and monkeys. 791 00:32:21,040 --> 00:32:23,110 And they had no preference between them. 792 00:32:23,110 --> 00:32:25,830 They would always go for a face compared to an object, a 793 00:32:25,830 --> 00:32:28,120 monkey face or a human face. 794 00:32:28,120 --> 00:32:29,900 And they could do these kinds of discrimination. 795 00:32:29,900 --> 00:32:32,730 The first moment before they had ever-- except for whatever 796 00:32:32,730 --> 00:32:35,020 happens right a birth-- seen one. 797 00:32:35,020 --> 00:32:38,640 So they never practiced on anything. 798 00:32:38,640 --> 00:32:40,540 Because they had not been allowed to see a face. 799 00:32:40,540 --> 00:32:44,480 But the first moment before they saw any living face, they 800 00:32:44,480 --> 00:32:48,040 already had this preference for faces for both humans and 801 00:32:48,040 --> 00:32:52,230 monkeys, as if it's in our genes to be drawn to faces. 802 00:32:52,230 --> 00:32:55,040 And what the mechanism is, the top-heavy, something else, we 803 00:32:55,040 --> 00:32:56,040 don't quite know. 804 00:32:56,040 --> 00:32:58,440 But it's in our brain to go for faces. 805 00:32:58,440 --> 00:33:00,220 They're so important for us. 806 00:33:00,220 --> 00:33:03,410 Then some monkeys hung around people. 807 00:33:03,410 --> 00:33:06,180 And some monkeys hung around monkeys. 808 00:33:06,180 --> 00:33:09,650 And what happened is really quite striking. 809 00:33:09,650 --> 00:33:13,440 They got better at the species they hung around. 810 00:33:13,440 --> 00:33:16,320 So if you did these kinds of tests, the monkeys who hung 811 00:33:16,320 --> 00:33:18,970 around monkeys got better and better at monkeys. 812 00:33:18,970 --> 00:33:20,830 And the monkeys that hung around people got better and 813 00:33:20,830 --> 00:33:22,740 better at people. 814 00:33:22,740 --> 00:33:24,150 So what does that mean? 815 00:33:24,150 --> 00:33:26,440 That means it looks like there's a genetic preparation. 816 00:33:26,440 --> 00:33:29,080 The first face that they see with the slight asterisk of 817 00:33:29,080 --> 00:33:31,700 the moment of birth, they are already preferring faces. 818 00:33:31,700 --> 00:33:33,800 The very first one they see, even though they've gone six 819 00:33:33,800 --> 00:33:38,020 months to two years without seeing any face at all. 820 00:33:38,020 --> 00:33:40,390 And then they get better selectively on the species 821 00:33:40,390 --> 00:33:41,900 they're exposed to. 822 00:33:41,900 --> 00:33:44,200 So there's a genetic preparation and then kind of a 823 00:33:44,200 --> 00:33:46,940 sensitive period where you build up a representation of 824 00:33:46,940 --> 00:33:49,980 the species that you're living with. 825 00:33:49,980 --> 00:33:54,840 So let me slide there for a moment to now writing. 826 00:33:54,840 --> 00:33:56,830 As long as there's been mammals, as long as there's 827 00:33:56,830 --> 00:34:00,535 been people, we've been born to things around us with faces 828 00:34:00,535 --> 00:34:03,960 and interacted with people who have faces. 829 00:34:03,960 --> 00:34:05,960 So that's deep in our evolutionary history. 830 00:34:05,960 --> 00:34:07,890 Not deep in our evolutionary history 831 00:34:07,890 --> 00:34:09,730 is writing and reading. 832 00:34:09,730 --> 00:34:11,909 The first visual language of any kind is 833 00:34:11,909 --> 00:34:14,620 about 4,000 years ago. 834 00:34:14,620 --> 00:34:17,409 Not until the Gutenberg Bible-- 835 00:34:17,409 --> 00:34:21,159 and that's about 600 years ago-- 836 00:34:21,159 --> 00:34:23,739 did large numbers of people read. 837 00:34:23,739 --> 00:34:26,860 So unlike faces and objects which have been around 838 00:34:26,860 --> 00:34:31,510 forever, not only for us, but for other species, writing and 839 00:34:31,510 --> 00:34:34,080 reading have been around only for a few hundred years. 840 00:34:34,080 --> 00:34:36,320 Our brains are not evolved to be reading brains. 841 00:34:36,320 --> 00:34:40,880 It's just an unbelievably powerful cultural invention. 842 00:34:40,880 --> 00:34:42,610 And people can read fast. 843 00:34:42,610 --> 00:34:44,550 A typical reader can do this. 844 00:34:44,550 --> 00:34:47,199 This is kind of amazing. 845 00:34:47,199 --> 00:34:48,370 Most of us know somewhere between 846 00:34:48,370 --> 00:34:51,580 50,000 and 100,000 words. 847 00:34:51,580 --> 00:34:52,610 We don't know all of them well. 848 00:34:52,610 --> 00:34:53,850 We can't spell all of them correctly. 849 00:34:53,850 --> 00:34:55,690 But we kind of can get them if we see them. 850 00:34:55,690 --> 00:34:59,750 And if we show you one word in 50,000ths of a second, you can 851 00:34:59,750 --> 00:35:02,210 recognize which word you saw. 852 00:35:02,210 --> 00:35:03,720 It's kind of amazing. 853 00:35:03,720 --> 00:35:06,830 People read about 200 to 250 words per minute, a typical 854 00:35:06,830 --> 00:35:10,000 reader cruising along when they're focused. 855 00:35:10,000 --> 00:35:11,980 These things can be measured relatively simply. 856 00:35:11,980 --> 00:35:13,020 Here's one that's a little trickier. 857 00:35:13,020 --> 00:35:13,560 But let me tell you. 858 00:35:13,560 --> 00:35:15,480 Again, it shows you how experiments can tell us 859 00:35:15,480 --> 00:35:16,960 something we could not have guessed without the 860 00:35:16,960 --> 00:35:20,210 experiment, about how you read every moment you've read 861 00:35:20,210 --> 00:35:21,730 throughout your life. 862 00:35:21,730 --> 00:35:24,450 So I'm going to tell you now that you read about 12 863 00:35:24,450 --> 00:35:25,470 letters at a time. 864 00:35:25,470 --> 00:35:26,680 And then you move your eyes. 865 00:35:26,680 --> 00:35:29,320 Whatever you're reading, a book, on the computer, you'll 866 00:35:29,320 --> 00:35:30,970 read about 12 letters. 867 00:35:30,970 --> 00:35:33,300 That's where you're fixated. 868 00:35:33,300 --> 00:35:36,820 Those will only be visible to you, and then you'll move your 869 00:35:36,820 --> 00:35:40,890 eyes to get the next set of letters you need to read. 870 00:35:40,890 --> 00:35:42,260 Now you go, no. 871 00:35:42,260 --> 00:35:44,030 There's text there. 872 00:35:44,030 --> 00:35:45,320 I'll give you, I move my eyes. 873 00:35:45,320 --> 00:35:48,660 But what's really happening, let me show you how blind you 874 00:35:48,660 --> 00:35:52,080 are to everything but 12 letters at a time. 875 00:35:52,080 --> 00:35:54,590 So here's the experiment from McConkie & Raynor. 876 00:35:54,590 --> 00:35:56,390 And many people have found this since. 877 00:35:56,390 --> 00:35:58,200 They tracked people's eye movements. 878 00:35:58,200 --> 00:35:59,620 You can have a machine that tracks where your eyes are 879 00:35:59,620 --> 00:36:01,890 fixated, where you're looking. 880 00:36:01,890 --> 00:36:04,970 Every time you moved, what they did is they took the text 881 00:36:04,970 --> 00:36:08,640 that was written across a monitor, they kept about 12 882 00:36:08,640 --> 00:36:09,900 letters where you're looking. 883 00:36:09,900 --> 00:36:13,690 And they made everything else on the monitor x's. 884 00:36:13,690 --> 00:36:14,460 You don't know this. 885 00:36:14,460 --> 00:36:16,140 You're just reading. 886 00:36:16,140 --> 00:36:20,460 So you're reading "people of." This is where your eyes are. 887 00:36:20,460 --> 00:36:22,010 The computer makes everything else an x. 888 00:36:22,010 --> 00:36:23,870 You move your eyes. 889 00:36:23,870 --> 00:36:24,910 Now this becomes x's. 890 00:36:24,910 --> 00:36:26,030 And these are x's. 891 00:36:26,030 --> 00:36:27,800 You move your eye. 892 00:36:27,800 --> 00:36:28,990 These become x's. 893 00:36:28,990 --> 00:36:30,210 You move your eyes. 894 00:36:30,210 --> 00:36:31,015 These become x's. 895 00:36:31,015 --> 00:36:32,260 Does hat make sense? 896 00:36:32,260 --> 00:36:34,970 Every time you move, where you land, they give you the words 897 00:36:34,970 --> 00:36:35,740 and letters. 898 00:36:35,740 --> 00:36:38,400 But everything to the left and right are all x's. 899 00:36:38,400 --> 00:36:42,980 And the astounding thing is nobody ever says hey, why are 900 00:36:42,980 --> 00:36:45,540 there all the x's. 901 00:36:45,540 --> 00:36:48,570 Because when you're reading, unbeknownst to you, you only 902 00:36:48,570 --> 00:36:52,300 see with good acuity 12 letters at a time. 903 00:36:52,300 --> 00:36:55,350 And everything else, you barely notice it's there. 904 00:36:55,350 --> 00:36:57,160 You notice something is there. 905 00:36:57,160 --> 00:36:59,410 If there's nothing there, you would notice it. 906 00:36:59,410 --> 00:37:03,190 But your mind is not really seeing it at all. 907 00:37:03,190 --> 00:37:06,700 And so people have tried to represent this. 908 00:37:06,700 --> 00:37:09,320 This, when you read, is something like this. 909 00:37:09,320 --> 00:37:11,780 Where you look, in your fovea, or your high acuity, you see 910 00:37:11,780 --> 00:37:13,030 about 12 letters. 911 00:37:13,030 --> 00:37:16,320 Everything else is like this. 912 00:37:16,320 --> 00:37:19,670 And that's why if I flip it to x's, you don't even notice. 913 00:37:19,670 --> 00:37:21,730 Because it's all pretty crummy how you see it. 914 00:37:21,730 --> 00:37:22,885 You notice something is there. 915 00:37:22,885 --> 00:37:26,420 But it's pretty crummy. 916 00:37:26,420 --> 00:37:27,560 You can say, I don't believe it. 917 00:37:27,560 --> 00:37:28,520 But people have done this experiment 918 00:37:28,520 --> 00:37:29,530 over and over again. 919 00:37:29,530 --> 00:37:31,650 And when they flip everything to x's to the left and right 920 00:37:31,650 --> 00:37:33,800 of about 12 letters that you're looking at, people just 921 00:37:33,800 --> 00:37:34,550 don't know. 922 00:37:34,550 --> 00:37:37,490 Because they don't really see it as they read anymore. 923 00:37:37,490 --> 00:37:38,510 Does that make sense? 924 00:37:38,510 --> 00:37:40,980 12 letters at a time. 925 00:37:40,980 --> 00:37:43,440 So again, we're trying to understand some of these 926 00:37:43,440 --> 00:37:46,560 things in regards to difficulties people have. 927 00:37:46,560 --> 00:37:49,710 So it turns out there's a part of the brain that's also 928 00:37:49,710 --> 00:37:52,880 involved in reading where, if you damage, you get what's 929 00:37:52,880 --> 00:37:54,020 called word blindness. 930 00:37:54,020 --> 00:37:55,330 So these are adults who are good 931 00:37:55,330 --> 00:37:56,860 readers, no problem reading. 932 00:37:56,860 --> 00:37:59,690 They get a stroke Hts left visual cortex around here. 933 00:37:59,690 --> 00:38:03,470 The most famous original case, in 1887, all of a sudden one 934 00:38:03,470 --> 00:38:06,020 day after a headache, this man was unable to read. 935 00:38:06,020 --> 00:38:08,310 His vision was otherwise perfectly good. 936 00:38:08,310 --> 00:38:10,240 He could hear words and speak words. 937 00:38:10,240 --> 00:38:12,030 He could see numbers. 938 00:38:12,030 --> 00:38:13,720 He could write down words. 939 00:38:13,720 --> 00:38:15,490 His writing was kind of slow and laborious. 940 00:38:15,490 --> 00:38:17,230 It wasn't typical writing. 941 00:38:17,230 --> 00:38:19,610 But then you could show him a few moments later what he had 942 00:38:19,610 --> 00:38:22,570 written, and he would not be able to read it aloud. 943 00:38:22,570 --> 00:38:26,740 So here's a pathway where stuff out there in the world 944 00:38:26,740 --> 00:38:28,670 in vision meets how we read. 945 00:38:36,820 --> 00:38:37,200 Amazing. 946 00:38:37,200 --> 00:38:39,920 Now it turns out, just like there's a spot in your brain 947 00:38:39,920 --> 00:38:43,020 that's the first moment where something you see is a face. 948 00:38:43,020 --> 00:38:48,240 There's a part that's shown here in red that's near that. 949 00:38:48,240 --> 00:38:50,150 It's bigger in the left hemisphere, the language 950 00:38:50,150 --> 00:38:50,950 hemisphere. 951 00:38:50,950 --> 00:38:53,330 It's pretty specific relatively specific for words 952 00:38:53,330 --> 00:38:56,240 compared to other things. 953 00:38:56,240 --> 00:38:58,690 And so we end up with a picture like this with 954 00:38:58,690 --> 00:39:02,070 relatively specific areas in the back of our brain that are 955 00:39:02,070 --> 00:39:06,800 highly specialized for recognizing where things are. 956 00:39:06,800 --> 00:39:08,020 I didn't talk too much about that. 957 00:39:08,020 --> 00:39:12,350 But there's that area, faces, words, and objects. 958 00:39:12,350 --> 00:39:15,300 And if you have damage to any of these pathways, for 959 00:39:15,300 --> 00:39:17,740 whatever reason, the rest of our brain can't compensate. 960 00:39:17,740 --> 00:39:20,106 And it's all a big mystery, who am I looking at, what word 961 00:39:20,106 --> 00:39:23,540 am I looking at, what object do I see? 962 00:39:23,540 --> 00:39:27,340 Now, you might imagine that for things like faces or 963 00:39:27,340 --> 00:39:29,880 locations, we've had evolutionary pressure for 964 00:39:29,880 --> 00:39:31,270 forever to be good at that. 965 00:39:31,270 --> 00:39:32,110 Where are we? 966 00:39:32,110 --> 00:39:33,630 Who are we with? 967 00:39:33,630 --> 00:39:37,960 Whereas things like words, or nonsense words, and letters, 968 00:39:37,960 --> 00:39:39,080 or chairs-- 969 00:39:39,080 --> 00:39:40,950 which are a recent cultural invention-- 970 00:39:40,950 --> 00:39:44,040 our brains are not genetically predisposed to those specific 971 00:39:44,040 --> 00:39:44,460 categories. 972 00:39:44,460 --> 00:39:47,310 So there's a very clever study from Ted Polk in Michigan. 973 00:39:47,310 --> 00:39:48,270 So we took twins. 974 00:39:48,270 --> 00:39:49,350 And we'll talk more about this. 975 00:39:49,350 --> 00:39:52,370 But the way people try to get at until we know the real 976 00:39:52,370 --> 00:39:55,410 genes involved in things, they'll compare twins who are 977 00:39:55,410 --> 00:39:58,695 identical twins with the identical genes and twins 978 00:39:58,695 --> 00:40:02,160 which are so-called fraternal twins who are born to the same 979 00:40:02,160 --> 00:40:04,870 family but don't have the identical genes. 980 00:40:04,870 --> 00:40:06,990 And to the extent the identical twins are more 981 00:40:06,990 --> 00:40:10,290 similar to each other than the fraternal twins, that's a 982 00:40:10,290 --> 00:40:13,420 suggestion there's genetic influences on whatever you're 983 00:40:13,420 --> 00:40:14,680 looking at. 984 00:40:14,680 --> 00:40:17,210 So what they did is they had these people look at faces, 985 00:40:17,210 --> 00:40:20,760 places, letter strings, and chairs. 986 00:40:20,760 --> 00:40:23,630 And they calculated how similar was one twin to 987 00:40:23,630 --> 00:40:28,140 another, either identically genetic or not. 988 00:40:28,140 --> 00:40:32,200 And what they found was that for the faces and the places, 989 00:40:32,200 --> 00:40:35,100 there was much more similar, significantly more similarly 990 00:40:35,100 --> 00:40:38,110 between identical twins than fraternal twins. 991 00:40:38,110 --> 00:40:40,910 That's the genetic predisposition, in some way, 992 00:40:40,910 --> 00:40:44,600 of how you will see a face or know where you are. 993 00:40:44,600 --> 00:40:46,640 If they compare reading nonsense words, letter 994 00:40:46,640 --> 00:40:49,540 strings, or chairs, the two kinds of twins 995 00:40:49,540 --> 00:40:51,110 were just the same. 996 00:40:51,110 --> 00:40:54,990 It's as if there's no genetic predisposition in you to know 997 00:40:54,990 --> 00:40:55,960 where in your brain you're going to 998 00:40:55,960 --> 00:40:57,360 process words or chairs. 999 00:40:57,360 --> 00:40:58,370 But that makes sense. 1000 00:40:58,370 --> 00:41:03,770 Because a couple thousand years ago there were no words. 1001 00:41:03,770 --> 00:41:05,020 And a few more thousand years than that, 1002 00:41:05,020 --> 00:41:06,330 there were no chairs. 1003 00:41:06,330 --> 00:41:08,870 So that's we don't have the genes for recent 1004 00:41:08,870 --> 00:41:10,140 inventions in the world. 1005 00:41:10,140 --> 00:41:12,340 But our brain is brilliant at becoming good at things like 1006 00:41:12,340 --> 00:41:15,425 reading as we invent them. 1007 00:41:15,425 --> 00:41:17,930 For the last part of the talk, I want to talk about face 1008 00:41:17,930 --> 00:41:18,470 recognition. 1009 00:41:18,470 --> 00:41:22,090 So all of us know that when we learn to read it was 1010 00:41:22,090 --> 00:41:22,900 a pretty big deal. 1011 00:41:22,900 --> 00:41:24,300 It was a while ago. 1012 00:41:24,300 --> 00:41:26,360 If you are a typical reader, you're passionate. 1013 00:41:26,360 --> 00:41:27,550 If you're a struggling reader, that can be 1014 00:41:27,550 --> 00:41:28,600 a persistent problem. 1015 00:41:28,600 --> 00:41:30,520 But you got through it, and you're a reader. 1016 00:41:30,520 --> 00:41:33,210 None of us went to third grade and said, today is the day 1017 00:41:33,210 --> 00:41:35,346 that we study faces. 1018 00:41:35,346 --> 00:41:37,810 And your parents are going, I hope you're going at faces. 1019 00:41:37,810 --> 00:41:40,390 Because we really want you to go to MIT someday. 1020 00:41:40,390 --> 00:41:43,270 This is the moment to get ready for the face SAT. 1021 00:41:43,270 --> 00:41:45,250 But what I'm going to show you is that in fact, through 1022 00:41:45,250 --> 00:41:48,040 experience, you're educated for faces. 1023 00:41:48,040 --> 00:41:50,750 And there's some social consequences for the faces 1024 00:41:50,750 --> 00:41:53,340 you're not educated on, on average. 1025 00:41:53,340 --> 00:41:55,170 So let's talk about that. 1026 00:41:55,170 --> 00:41:59,210 So one way we see faces is we see faces that are right-side 1027 00:41:59,210 --> 00:42:01,580 up, overwhelmingly. 1028 00:42:01,580 --> 00:42:04,210 So I'm going to show you this upside down face. 1029 00:42:04,210 --> 00:42:05,380 I'm going to reverse it. 1030 00:42:05,380 --> 00:42:07,070 And that's what it is. 1031 00:42:07,070 --> 00:42:08,840 That's gruesome, right? 1032 00:42:08,840 --> 00:42:11,220 But can you tell that when that turns, 1033 00:42:11,220 --> 00:42:12,800 it's going to be this? 1034 00:42:12,800 --> 00:42:15,930 So the way that we interpret the weirdness of face 1035 00:42:15,930 --> 00:42:18,780 inversion, the fact that we process upside 1036 00:42:18,780 --> 00:42:22,030 down faces so badly-- 1037 00:42:22,030 --> 00:42:24,230 we don't have any hint of what's really there-- 1038 00:42:24,230 --> 00:42:26,800 it's because we didn't practice on them. 1039 00:42:26,800 --> 00:42:29,310 It's as if I gave you a test in a language that you never 1040 00:42:29,310 --> 00:42:31,030 spoke or read. 1041 00:42:31,030 --> 00:42:32,920 Well you can do badly. 1042 00:42:32,920 --> 00:42:34,845 So that shows you that faces, it's a 1043 00:42:34,845 --> 00:42:36,510 so experienced dependent. 1044 00:42:36,510 --> 00:42:38,520 It's because you see upright faces you get 1045 00:42:38,520 --> 00:42:39,470 good at upright faces. 1046 00:42:39,470 --> 00:42:41,000 All we have to do is turn it upside down. 1047 00:42:41,000 --> 00:42:44,230 And all the knowledge and skill you have, it's as if I 1048 00:42:44,230 --> 00:42:45,920 tested you in a different language. 1049 00:42:45,920 --> 00:42:48,530 It's that specific. 1050 00:42:48,530 --> 00:42:51,450 Here's another example, side by side, looks pretty similar. 1051 00:42:51,450 --> 00:42:52,700 But that's what you're really seeing. 1052 00:42:57,390 --> 00:42:59,220 It's unbelievable. 1053 00:42:59,220 --> 00:43:03,400 Turn your head to believe me in case you're suspicious. 1054 00:43:03,400 --> 00:43:04,650 This is legit. 1055 00:43:06,560 --> 00:43:09,830 We're so bad at upside down faces because we don't 1056 00:43:09,830 --> 00:43:12,270 practice on them. 1057 00:43:12,270 --> 00:43:15,640 So what we are good at in faces is so much dependent on 1058 00:43:15,640 --> 00:43:17,930 what we practice. 1059 00:43:17,930 --> 00:43:19,240 You may recognize this person or not. 1060 00:43:24,440 --> 00:43:25,690 These are less dramatic. 1061 00:43:28,930 --> 00:43:30,670 People don't become as good as they get at faces 1062 00:43:30,670 --> 00:43:32,870 until about age 16. 1063 00:43:32,870 --> 00:43:34,680 We don't consciously practice it. 1064 00:43:34,680 --> 00:43:36,890 But the social experience we have is practicing, 1065 00:43:36,890 --> 00:43:40,240 practicing, practicing how you perceive a face. 1066 00:43:43,670 --> 00:43:46,530 One fun study from a Susan Carey now at Harvard is she 1067 00:43:46,530 --> 00:43:48,580 took dog show judges. 1068 00:43:48,580 --> 00:43:50,300 Now, I don't know too much about dog shows. 1069 00:43:50,300 --> 00:43:51,850 Some of you might know something. 1070 00:43:51,850 --> 00:43:53,510 But a little bit of what I know is this. 1071 00:43:53,510 --> 00:43:56,670 Sort of like in sports, you have judges who work their way 1072 00:43:56,670 --> 00:44:00,260 up a ladder of experience and reputation. 1073 00:44:00,260 --> 00:44:02,620 So in sports things, you have the local judges. 1074 00:44:02,620 --> 00:44:03,940 And the really good ones become the ones 1075 00:44:03,940 --> 00:44:04,810 for the bigger leagues. 1076 00:44:04,810 --> 00:44:06,660 And the big ones get to go to the Super Bowl and World 1077 00:44:06,660 --> 00:44:09,620 Series who are really skilled and thought to be excellent. 1078 00:44:09,620 --> 00:44:11,120 Dog show judges, similarly, start locally. 1079 00:44:11,120 --> 00:44:13,420 The ones who seem pretty good and persistent at it then 1080 00:44:13,420 --> 00:44:14,480 become the state judge show. 1081 00:44:14,480 --> 00:44:16,940 And then they go to the big one in New York. 1082 00:44:16,940 --> 00:44:21,870 And so they did these face inversion experiments on dog 1083 00:44:21,870 --> 00:44:24,970 show judges, people who were just beginning to be a dog 1084 00:44:24,970 --> 00:44:27,300 show judge, people who have done it for a while, people 1085 00:44:27,300 --> 00:44:28,790 who've done it for a lot of years. 1086 00:44:28,790 --> 00:44:32,320 And they asked, when do you get so much better at a 1087 00:44:32,320 --> 00:44:35,270 right-side up dog face than an upside down dog face? 1088 00:44:35,270 --> 00:44:38,350 Now, most people are about the same to start with. 1089 00:44:38,350 --> 00:44:40,830 Because we're not that good at dog faces. 1090 00:44:40,830 --> 00:44:41,990 You might know a dog or two. 1091 00:44:41,990 --> 00:44:45,060 But you don't know hundreds of dollars. 1092 00:44:45,060 --> 00:44:48,660 It took eight years for dog show judges-- and they were 1093 00:44:48,660 --> 00:44:50,910 dog enthusiasts for many years before they 1094 00:44:50,910 --> 00:44:52,490 became a dog show judge-- 1095 00:44:52,490 --> 00:44:56,480 eight years of seeing many, many dogs at dog show 1096 00:44:56,480 --> 00:45:00,600 competitions to develop the upright face expertise that we 1097 00:45:00,600 --> 00:45:02,720 all have for faces as adults. 1098 00:45:02,720 --> 00:45:05,750 So for an adult, you have to practice eight years to get 1099 00:45:05,750 --> 00:45:08,140 this kind of expertise. 1100 00:45:08,140 --> 00:45:09,930 You can't just do it by cramming. 1101 00:45:09,930 --> 00:45:12,430 It's practice, practice, practice in the most brutal 1102 00:45:12,430 --> 00:45:13,680 fundamental sense. 1103 00:45:15,810 --> 00:45:18,410 Now I'll say one last thing about this then 1104 00:45:18,410 --> 00:45:19,850 go to the last topic. 1105 00:45:19,850 --> 00:45:21,940 The other thing is that we understand also-- and we've 1106 00:45:21,940 --> 00:45:24,312 mentioned this before, but I'll say it one more time-- 1107 00:45:24,312 --> 00:45:28,700 that imagination and perception use the same neural 1108 00:45:28,700 --> 00:45:30,170 territory in your mind. 1109 00:45:30,170 --> 00:45:32,610 So here's a study from Nancy Kanwisher again. 1110 00:45:32,610 --> 00:45:35,760 Here's a part of the brain that responds to faces, seeing 1111 00:45:35,760 --> 00:45:39,600 a face, seeing a house, seeing a face, seeing a house. 1112 00:45:39,600 --> 00:45:43,380 Now, imagining a face, imagining a house, imagining a 1113 00:45:43,380 --> 00:45:45,720 face, imagining a house. 1114 00:45:45,720 --> 00:45:49,460 So seeing one drives the brain more strongly 1115 00:45:49,460 --> 00:45:50,910 than imagining it. 1116 00:45:50,910 --> 00:45:54,030 But when you imagine a face, you seem to use the same brain 1117 00:45:54,030 --> 00:45:56,600 network as when you see it. 1118 00:45:56,600 --> 00:45:59,230 It's just not as vivid and powerful. 1119 00:45:59,230 --> 00:46:02,280 So perception is the stuff literally in your mind of 1120 00:46:02,280 --> 00:46:03,000 imagination. 1121 00:46:03,000 --> 00:46:05,870 You can imagine things, because you've seen them 1122 00:46:05,870 --> 00:46:08,450 before, literally in your brain It's the 1123 00:46:08,450 --> 00:46:11,090 same part of the brain. 1124 00:46:11,090 --> 00:46:13,620 So the last topic I want to talk about is a sensitive and 1125 00:46:13,620 --> 00:46:14,370 difficult one. 1126 00:46:14,370 --> 00:46:17,220 So I'm going to do it right, I hope. 1127 00:46:17,220 --> 00:46:19,250 But it's one that's a practical one, and a 1128 00:46:19,250 --> 00:46:23,240 consequence, we believe, of the fact that you're good at 1129 00:46:23,240 --> 00:46:25,120 faces that you practice. 1130 00:46:25,120 --> 00:46:28,600 So we're going to talk about in these studies people 1131 00:46:28,600 --> 00:46:31,950 perceiving faces of European Americans, or white Americans, 1132 00:46:31,950 --> 00:46:33,940 or African Americans. 1133 00:46:33,940 --> 00:46:37,630 And there's a huge amount of research 1134 00:46:37,630 --> 00:46:39,120 that shows the following. 1135 00:46:39,120 --> 00:46:44,920 That whatever racial group you see a lot of, you're pretty 1136 00:46:44,920 --> 00:46:46,240 good at remembering those faces. 1137 00:46:46,240 --> 00:46:50,790 At whatever group you see less, you're far worse. 1138 00:46:50,790 --> 00:46:53,950 We interpret this as a consequence of the practice 1139 00:46:53,950 --> 00:46:55,720 that you have. 1140 00:46:55,720 --> 00:46:58,900 But social psychologists worry it has a second consequence. 1141 00:46:58,900 --> 00:47:01,150 Let me tell you the practice story. 1142 00:47:01,150 --> 00:47:02,540 So we did a study. 1143 00:47:02,540 --> 00:47:03,120 This is from us. 1144 00:47:03,120 --> 00:47:04,800 But it's very similar to other people in terms of the 1145 00:47:04,800 --> 00:47:05,500 conclusion. 1146 00:47:05,500 --> 00:47:08,500 There's literally like 1,000 of these studies that show 1147 00:47:08,500 --> 00:47:11,480 that people are superior at recognizing in an experiment 1148 00:47:11,480 --> 00:47:14,950 faces from their own group than from other groups. 1149 00:47:14,950 --> 00:47:17,300 And here, an experiment that was done with Stanford 1150 00:47:17,300 --> 00:47:19,850 students, a look in their mind and then in their brain. 1151 00:47:19,850 --> 00:47:21,930 So these are Stanford students just some years ago, maybe a 1152 00:47:21,930 --> 00:47:23,180 lot like you in many ways. 1153 00:47:25,820 --> 00:47:28,550 They saw some faces, and then they got a memory test. 1154 00:47:28,550 --> 00:47:30,790 This is their performance on the memory test. 1155 00:47:30,790 --> 00:47:35,050 So we had both European American and African American 1156 00:47:35,050 --> 00:47:37,650 faces that they viewed. 1157 00:47:37,650 --> 00:47:40,410 And the participants in the research were both African 1158 00:47:40,410 --> 00:47:42,470 American and European American. 1159 00:47:42,470 --> 00:47:46,370 OK so there were white faces, white subjects, black faces, 1160 00:47:46,370 --> 00:47:48,070 black subjects. 1161 00:47:48,070 --> 00:47:49,800 And what you can see is this. 1162 00:47:49,800 --> 00:47:51,820 The higher the bar, the better the memory. 1163 00:47:51,820 --> 00:47:55,440 In both groups, they're better in performance at remembering 1164 00:47:55,440 --> 00:48:00,420 faces from their own group. 1165 00:48:00,420 --> 00:48:02,350 But there's more to it than that. 1166 00:48:02,350 --> 00:48:05,590 If you look at these bars, these are the memory for the 1167 00:48:05,590 --> 00:48:06,695 white faces. 1168 00:48:06,695 --> 00:48:09,240 And it's about the same in the two groups. 1169 00:48:09,240 --> 00:48:11,120 And look at the big difference for the 1170 00:48:11,120 --> 00:48:13,190 African American faces. 1171 00:48:13,190 --> 00:48:15,360 So two things are happening here. 1172 00:48:15,360 --> 00:48:18,610 One of them is there's superior memory from faces 1173 00:48:18,610 --> 00:48:20,630 from your own group. 1174 00:48:20,630 --> 00:48:25,480 And the second story is that for what we believed, and from 1175 00:48:25,480 --> 00:48:27,740 other research as well, is this. 1176 00:48:27,740 --> 00:48:30,670 If you're a minority group, you're still pretty good at 1177 00:48:30,670 --> 00:48:32,420 the majority faces. 1178 00:48:32,420 --> 00:48:34,460 If you're a majority group, you're not so good at the 1179 00:48:34,460 --> 00:48:35,790 minority faces. 1180 00:48:35,790 --> 00:48:38,580 So these are European American Stanford students. 1181 00:48:38,580 --> 00:48:41,990 And look how a miserable their memory is for these African 1182 00:48:41,990 --> 00:48:43,240 American faces. 1183 00:48:46,140 --> 00:48:48,920 This is a difficult topic for us, in part, because race is a 1184 00:48:48,920 --> 00:48:51,980 different topic for good reasons. 1185 00:48:51,980 --> 00:48:56,560 But social psychologists worry that the lack of practice that 1186 00:48:56,560 --> 00:49:00,170 many of us have on other groups growing up at home, in 1187 00:49:00,170 --> 00:49:01,370 our community, and schools-- 1188 00:49:01,370 --> 00:49:03,410 and it varies for people, but on average-- 1189 00:49:03,410 --> 00:49:06,710 makes us less able to individuate in our memory one 1190 00:49:06,710 --> 00:49:09,420 person from another in other groups. 1191 00:49:09,420 --> 00:49:13,460 And now this is not about racial attitudes. 1192 00:49:13,460 --> 00:49:17,280 This is simple, objective recognition of faces. 1193 00:49:17,280 --> 00:49:20,880 But it could certainly support consideration of other groups 1194 00:49:20,880 --> 00:49:22,670 as if they were all the same. 1195 00:49:22,670 --> 00:49:24,490 Because they look all the same. 1196 00:49:24,490 --> 00:49:26,430 I remember I had an African American 1197 00:49:26,430 --> 00:49:28,690 colleague at Stanford. 1198 00:49:28,690 --> 00:49:29,680 And he was a dean. 1199 00:49:29,680 --> 00:49:33,190 And he went to China with a Nobel laureate who is now the 1200 00:49:33,190 --> 00:49:37,140 Secretary of Energy in the Obama 1201 00:49:37,140 --> 00:49:39,230 administration, Steve Chu. 1202 00:49:39,230 --> 00:49:41,980 And, of course, Nobel laureates are a pretty big. 1203 00:49:41,980 --> 00:49:45,540 So this dean went to this Nobel laureate all the time. 1204 00:49:45,540 --> 00:49:48,610 We're meeting Stanford donors and other things. 1205 00:49:48,610 --> 00:49:49,710 He said they got on the plane. 1206 00:49:49,710 --> 00:49:52,570 They went to China, the two of them. 1207 00:49:52,570 --> 00:49:54,390 And he went into a reception. 1208 00:49:54,390 --> 00:49:57,870 And he knew Steve Chu was in there. 1209 00:49:57,870 --> 00:50:00,500 The African American dean said, I could not pick him out 1210 00:50:00,500 --> 00:50:01,700 for my life. 1211 00:50:01,700 --> 00:50:05,540 When I saw him now, not with other people I know, but with 1212 00:50:05,540 --> 00:50:08,790 a 500 other Chinese people in a large reception. 1213 00:50:08,790 --> 00:50:12,180 So it's not about bad attitudes in this case. 1214 00:50:12,180 --> 00:50:14,610 It's just literally the experience you have. 1215 00:50:14,610 --> 00:50:19,960 And in the brain, this part of this FFA, responds more to 1216 00:50:19,960 --> 00:50:21,600 groups from your own-- 1217 00:50:21,600 --> 00:50:22,350 on average-- 1218 00:50:22,350 --> 00:50:24,390 from your own racial group than the other racial group. 1219 00:50:24,390 --> 00:50:26,600 And we think that's promoting the ease with which to 1220 00:50:26,600 --> 00:50:31,130 identify individuals in your group and the difficulty with 1221 00:50:31,130 --> 00:50:34,340 which you can identify I individuals in another group. 1222 00:50:34,340 --> 00:50:36,650 And so we have strong reason to think that this is all 1223 00:50:36,650 --> 00:50:38,910 about this particular phenomenon about your 1224 00:50:38,910 --> 00:50:40,340 experience. 1225 00:50:40,340 --> 00:50:41,810 So let me tell you why. 1226 00:50:41,810 --> 00:50:44,400 One thing is we know that this is not present at birth. 1227 00:50:44,400 --> 00:50:47,040 People have done these kinds of experiments with infants. 1228 00:50:47,040 --> 00:50:51,300 These racial biases in what kinds of faces we can remember 1229 00:50:51,300 --> 00:50:52,390 are not present at birth. 1230 00:50:52,390 --> 00:50:54,100 So they're not in our genes. 1231 00:50:54,100 --> 00:50:55,850 They're from our experience. 1232 00:50:55,850 --> 00:50:57,510 But they are present by three months. 1233 00:50:57,510 --> 00:51:01,180 But by then you've seen a lot of people in your family. 1234 00:51:01,180 --> 00:51:03,840 And the kind of experiment that's very telling for this 1235 00:51:03,840 --> 00:51:05,980 is a study where there were Korean children. 1236 00:51:05,980 --> 00:51:07,230 They were three to nine years old. 1237 00:51:07,230 --> 00:51:10,850 They were adopted by European Caucasian families, so, in the 1238 00:51:10,850 --> 00:51:12,950 sense, a cross-racial adoption. 1239 00:51:12,950 --> 00:51:15,290 And then they tested their memory for faces. 1240 00:51:15,290 --> 00:51:17,960 And for these Korean children adopted by European Caucasian 1241 00:51:17,960 --> 00:51:20,900 families, they had better memory for the Caucasian 1242 00:51:20,900 --> 00:51:26,370 faces, because that's who they saw around them all the time. 1243 00:51:26,370 --> 00:51:31,810 And they were just like their French peers who also saw 1244 00:51:31,810 --> 00:51:33,530 Caucasian faces all the time. 1245 00:51:33,530 --> 00:51:35,680 And the opposite of the findings that you've got with 1246 00:51:35,680 --> 00:51:39,780 Korean children in South Korea. 1247 00:51:39,780 --> 00:51:43,820 The inversion one is kind of funny, amazing. 1248 00:51:43,820 --> 00:51:48,250 The fact that we can struggle to individuate in memory one 1249 00:51:48,250 --> 00:51:51,130 African American from another, or one Asian American from 1250 00:51:51,130 --> 00:51:53,530 another, or one Caucasian American from another 1251 00:51:53,530 --> 00:51:55,970 depending on the environment that we grew up in and were 1252 00:51:55,970 --> 00:52:01,180 exposed to, that could be facilitating stereotyping and 1253 00:52:01,180 --> 00:52:04,750 lack of individuation of people in other groups. 1254 00:52:04,750 --> 00:52:06,160 So the very last thing I want to do-- and this is just a 1255 00:52:06,160 --> 00:52:06,910 couple minutes-- 1256 00:52:06,910 --> 00:52:09,270 is talk about expression in faces. 1257 00:52:09,270 --> 00:52:10,150 And I'll come back to this in detail. 1258 00:52:10,150 --> 00:52:16,730 I just want to give you one last example of recognition in 1259 00:52:16,730 --> 00:52:18,130 the amygdala and fear. 1260 00:52:18,130 --> 00:52:20,050 So we'll come back to this in some detail later on. 1261 00:52:20,050 --> 00:52:23,680 But most researchers argue there's about six basic 1262 00:52:23,680 --> 00:52:27,040 emotions that people around the world transmit with their 1263 00:52:27,040 --> 00:52:32,060 facial expressions, happiness, sadness, fear, anger, 1264 00:52:32,060 --> 00:52:33,620 surprise, and disgust. 1265 00:52:33,620 --> 00:52:36,470 You can show these pictures to people around the world, and 1266 00:52:36,470 --> 00:52:39,610 they'll be, to some degree, consensus about what they are, 1267 00:52:39,610 --> 00:52:43,220 universal expressions of feelings transmitted by facial 1268 00:52:43,220 --> 00:52:45,240 expressions. 1269 00:52:45,240 --> 00:52:46,950 Now let's talk about fear faces. 1270 00:52:46,950 --> 00:52:48,310 I'll just talk about fear today. 1271 00:52:48,310 --> 00:52:49,560 And we'll talk about the amygdala. 1272 00:52:49,560 --> 00:52:51,280 So we have one on the left and one on the right, it's a very 1273 00:52:51,280 --> 00:52:54,730 small structure, almond shaped, one inside each of the 1274 00:52:54,730 --> 00:52:58,050 temporal lobes right next to the hippocampus. 1275 00:52:58,050 --> 00:53:00,610 So that's a view from the side of where that's located, one 1276 00:53:00,610 --> 00:53:02,540 on the left and one on the right. 1277 00:53:02,540 --> 00:53:04,360 And we know from a lot of animal research-- and I'll 1278 00:53:04,360 --> 00:53:06,490 come back to this again-- 1279 00:53:06,490 --> 00:53:09,270 the amygdala is essential for learned 1280 00:53:09,270 --> 00:53:11,590 fear, for learned fear. 1281 00:53:11,590 --> 00:53:14,520 So here's an experiment that shows you that. 1282 00:53:14,520 --> 00:53:17,430 One thing that mice know is cats are bad news. 1283 00:53:17,430 --> 00:53:18,930 It's survival. 1284 00:53:18,930 --> 00:53:20,290 What they did in this experiment is they 1285 00:53:20,290 --> 00:53:21,660 anesthetized the cat. 1286 00:53:21,660 --> 00:53:24,690 That's why the cat looks glassy-eyed. 1287 00:53:24,690 --> 00:53:29,220 Obviously the experiment would end too quickly for the mouse, 1288 00:53:29,220 --> 00:53:32,200 if the mouse had to come out and play with the cat. 1289 00:53:32,200 --> 00:53:33,660 The experiment would be brutal, and ugly, 1290 00:53:33,660 --> 00:53:35,360 and over too quickly. 1291 00:53:35,360 --> 00:53:38,150 But if the cat is breathing, the cat's eyes are open, it's 1292 00:53:38,150 --> 00:53:38,510 anesthetized. 1293 00:53:38,510 --> 00:53:40,070 But it can't move. 1294 00:53:40,070 --> 00:53:44,550 Now a typical rat or mouse will typically 1295 00:53:44,550 --> 00:53:45,670 still avoid the cat. 1296 00:53:45,670 --> 00:53:47,110 It's not worth figuring out exactly what's 1297 00:53:47,110 --> 00:53:47,910 going on with the cat. 1298 00:53:47,910 --> 00:53:48,970 Are they faking me out? 1299 00:53:48,970 --> 00:53:51,620 I'll just go that way. 1300 00:53:51,620 --> 00:53:55,775 But this is not the mouse who has the amygdala removed. 1301 00:53:58,500 --> 00:54:00,980 It's not fearful of what it ought to be fearful of 1302 00:54:00,980 --> 00:54:04,260 anymore, even survival. 1303 00:54:04,260 --> 00:54:07,670 What we believe the most important role of fear is not 1304 00:54:07,670 --> 00:54:09,530 fear of SATs or midterms. 1305 00:54:09,530 --> 00:54:11,600 Although we live in that world. 1306 00:54:11,600 --> 00:54:13,950 It's fear of what injure you and kill you. 1307 00:54:13,950 --> 00:54:14,960 Those are the things to learn. 1308 00:54:14,960 --> 00:54:16,940 Be fearful of what can kill you. 1309 00:54:16,940 --> 00:54:18,740 Be fearful of what can injure you. 1310 00:54:18,740 --> 00:54:21,490 Without the amygdala, you lose that fear. 1311 00:54:21,490 --> 00:54:24,390 But here's the other-- this is my last slide-- amazing thing. 1312 00:54:24,390 --> 00:54:26,610 There are humans who have injuries selectively to the 1313 00:54:26,610 --> 00:54:27,620 amygdala, very few. 1314 00:54:27,620 --> 00:54:29,190 But there's a few. 1315 00:54:29,190 --> 00:54:32,550 And not only do they have some problems with fear learning. 1316 00:54:32,550 --> 00:54:35,640 But they can't recognize fearful 1317 00:54:35,640 --> 00:54:37,195 facial expressions anymore. 1318 00:54:39,970 --> 00:54:42,350 If they ask them to say, what is this, without the word 1319 00:54:42,350 --> 00:54:44,440 present, they're very bad at telling you 1320 00:54:44,440 --> 00:54:45,820 that's a fearful face. 1321 00:54:45,820 --> 00:54:48,180 They can recognize all the other expressions pretty well 1322 00:54:48,180 --> 00:54:51,680 but not the fearful ones. 1323 00:54:51,680 --> 00:54:53,160 also 1324 00:54:53,160 --> 00:54:54,480 They're good of faces. 1325 00:54:54,480 --> 00:54:55,360 They're not prosopagnosia. 1326 00:54:55,360 --> 00:54:56,160 They're fine at faces. 1327 00:54:56,160 --> 00:54:57,030 They recognize their family. 1328 00:54:57,030 --> 00:54:59,360 But they can't recognize fearful expressions 1329 00:54:59,360 --> 00:55:01,970 selectively. 1330 00:55:01,970 --> 00:55:05,440 This is actually a very good drawing happy, sad, surprised, 1331 00:55:05,440 --> 00:55:07,400 disgusted, angry. 1332 00:55:07,400 --> 00:55:09,875 When she's asked to draw a fearful facial expression, 1333 00:55:09,875 --> 00:55:12,140 this patient draws this, a baby being afraid. 1334 00:55:12,140 --> 00:55:14,210 She understands the concept. 1335 00:55:14,210 --> 00:55:16,430 But it's not only that she can't recognize it. 1336 00:55:16,430 --> 00:55:20,020 She can't imagine what a fearful face looks like. 1337 00:55:20,020 --> 00:55:23,410 And we saw this over and over again. 1338 00:55:23,410 --> 00:55:25,060 And there's one last message in this. 1339 00:55:25,060 --> 00:55:27,850 Somehow our knowledge about what a fearful face looks 1340 00:55:27,850 --> 00:55:29,550 like, we're not scared of this. 1341 00:55:29,550 --> 00:55:31,130 You don't look at this and go, oh my gosh. 1342 00:55:31,130 --> 00:55:33,030 I can't believe he showed that in class. 1343 00:55:33,030 --> 00:55:37,250 I'll never sleep for 48 hours. 1344 00:55:37,250 --> 00:55:39,530 That's a social signal for somebody telling you, whoa. 1345 00:55:39,530 --> 00:55:41,000 There's something terrible happening here. 1346 00:55:41,000 --> 00:55:41,670 Look around you. 1347 00:55:41,670 --> 00:55:42,200 We better run. 1348 00:55:42,200 --> 00:55:43,550 It's a social signal. 1349 00:55:43,550 --> 00:55:46,780 And the part of your brain that learns what can kill you 1350 00:55:46,780 --> 00:55:51,160 also is where the knowledge is stored to recognize a social 1351 00:55:51,160 --> 00:55:54,160 signal about something that could be very dangerous. 1352 00:55:54,160 --> 00:55:56,560 The same idea that we put our knowledge in the parts of 1353 00:55:56,560 --> 00:55:58,180 their brain that act upon the world.