WEBVTT 00:00:10.200 --> 00:00:12.750 NANCY KANWISHER: So we won't get through the whole attention 00:00:12.750 --> 00:00:13.110 lecture. 00:00:13.110 --> 00:00:13.860 I saw this coming. 00:00:13.860 --> 00:00:16.027 I just felt like that last bit was important enough. 00:00:16.027 --> 00:00:17.430 We'll cut as needed. 00:00:17.430 --> 00:00:19.380 But I do want to talk about attention. 00:00:19.380 --> 00:00:22.710 And let me start by sharing with you some 00:00:22.710 --> 00:00:26.430 of the key ideas about what attention is. 00:00:26.430 --> 00:00:29.580 OK, so to get into the mode of thinking about this, 00:00:29.580 --> 00:00:32.220 let's consider the following question. 00:00:32.220 --> 00:00:34.530 How do you feel about people driving while talking 00:00:34.530 --> 00:00:36.700 on their cell phones? 00:00:36.700 --> 00:00:39.540 Smart, not smart? 00:00:39.540 --> 00:00:42.990 And while you're thinking about that, also consider the case-- 00:00:42.990 --> 00:00:45.480 like let's suppose that you have had 00:00:45.480 --> 00:00:47.760 a hands-free setup, so you don't have 00:00:47.760 --> 00:00:50.190 to be looking down on your cell phone 00:00:50.190 --> 00:00:55.740 or typing away or holding your cell phone. 00:00:55.740 --> 00:00:57.360 Maybe that's OK. 00:00:57.360 --> 00:00:58.710 What do you think? 00:00:58.710 --> 00:01:01.740 Is there no problem with driving while talking on your cell 00:01:01.740 --> 00:01:03.570 phone, provided you're not looking down 00:01:03.570 --> 00:01:04.920 and pecking away at it? 00:01:09.440 --> 00:01:10.040 Yes? 00:01:10.040 --> 00:01:10.790 What do you think? 00:01:13.078 --> 00:01:14.620 I want to know what you really think. 00:01:14.620 --> 00:01:18.190 I know what all the PR says. 00:01:18.190 --> 00:01:19.840 Is it fine? 00:01:19.840 --> 00:01:20.980 Yes? 00:01:20.980 --> 00:01:23.950 AUDIENCE: I would say it depends on whether you're driving-- 00:01:23.950 --> 00:01:26.500 Like if the road is clear and it's like your usual path, 00:01:26.500 --> 00:01:28.600 like driving is pretty automatic at that point. 00:01:28.600 --> 00:01:30.820 But it it's like high traffic or a new area, 00:01:30.820 --> 00:01:33.050 then I think it would have a significant affects, 00:01:33.050 --> 00:01:34.510 so you shouldn't. 00:01:34.510 --> 00:01:35.650 NANCY KANWISHER: Totally. 00:01:35.650 --> 00:01:38.620 My rule is, if I am talking on my cell phone, 00:01:38.620 --> 00:01:41.380 certainly, if I'm turning left, I put the damn cell phone 00:01:41.380 --> 00:01:42.160 on my lap. 00:01:42.160 --> 00:01:45.430 And I tell whoever it is, I can't talk to you 00:01:45.430 --> 00:01:47.050 and turn left at the same time. 00:01:47.050 --> 00:01:49.240 All right, turning left is the hardest thing we do. 00:01:49.240 --> 00:01:51.113 Self-driving cars can't turn left. 00:01:51.113 --> 00:01:52.030 Have I mentioned this? 00:01:52.030 --> 00:01:53.800 How does a self-driving car turn left? 00:01:53.800 --> 00:01:55.780 It turns right three times. 00:01:55.780 --> 00:01:56.350 Why is that? 00:01:56.350 --> 00:01:58.840 Because turning left is social cognition. 00:01:58.840 --> 00:02:01.060 It's like, do they see me? 00:02:01.060 --> 00:02:02.145 Do they know I'm here? 00:02:02.145 --> 00:02:03.520 Are they looking at my indicator? 00:02:03.520 --> 00:02:05.145 Do they realize I'm going to turn left? 00:02:05.145 --> 00:02:05.710 This is hard. 00:02:05.710 --> 00:02:06.790 This is social cognition. 00:02:06.790 --> 00:02:08.380 Nobody's mastered that yet. 00:02:08.380 --> 00:02:11.110 Anyway, it's hard for us too. 00:02:11.110 --> 00:02:14.140 Anyway, the real question here is not 00:02:14.140 --> 00:02:17.410 for me to lecture you about driving but to think about, 00:02:17.410 --> 00:02:20.650 why is that a problem? 00:02:20.650 --> 00:02:24.700 Why can't you talk to a person and pay attention to driving? 00:02:24.700 --> 00:02:27.970 What is the big deal, right? 00:02:27.970 --> 00:02:32.260 And so the intuition is we have some kind of limited processing 00:02:32.260 --> 00:02:33.190 ability. 00:02:33.190 --> 00:02:36.430 OK, we're not like super supercomputers who can just 00:02:36.430 --> 00:02:38.230 do millions of things at once. 00:02:38.230 --> 00:02:41.150 We have some kind of limit in how much stuff we can handle, 00:02:41.150 --> 00:02:41.650 OK? 00:02:41.650 --> 00:02:46.210 And I think everybody will have this intuition. 00:02:46.210 --> 00:02:48.730 You can't think about lots of different things at once. 00:02:48.730 --> 00:02:52.780 I like to think of this as the toaster model of cognition. 00:02:52.780 --> 00:02:55.570 That is, you plug in the toaster, and the lights dim, 00:02:55.570 --> 00:02:56.260 right? 00:02:56.260 --> 00:02:58.030 So if everything's on the same circuit, 00:02:58.030 --> 00:03:01.810 there's some kind of unitary thing, resource that's limited. 00:03:01.810 --> 00:03:05.020 And if some more of it goes here, less if it goes here. 00:03:05.020 --> 00:03:07.272 OK, so obviously we don't have simple circuits 00:03:07.272 --> 00:03:08.230 like that in our brain. 00:03:08.230 --> 00:03:11.530 And the relevant scarce commodity 00:03:11.530 --> 00:03:13.150 isn't just electricity. 00:03:13.150 --> 00:03:14.080 It's not electrons. 00:03:14.080 --> 00:03:18.010 It's some other kind of thing we don't totally understand. 00:03:18.010 --> 00:03:22.960 But there's still some sense in which of our mental processes 00:03:22.960 --> 00:03:24.580 are on the same circuit. 00:03:24.580 --> 00:03:25.810 OK? 00:03:25.810 --> 00:03:29.120 I'm assuming everybody is sharing this intuition here. 00:03:29.120 --> 00:03:30.278 So think about this. 00:03:30.278 --> 00:03:32.320 How many people feel like you can listen to music 00:03:32.320 --> 00:03:34.458 and read difficult stuff at the same time? 00:03:34.458 --> 00:03:35.500 Raise your-- I'm curious. 00:03:35.500 --> 00:03:38.230 How many people feel like they can do that? 00:03:38.230 --> 00:03:40.090 Only a few. 00:03:40.090 --> 00:03:41.980 That's so interesting. 00:03:41.980 --> 00:03:42.730 Sort of. 00:03:42.730 --> 00:03:45.310 Yeah, I can't do it at all, like at all, 00:03:45.310 --> 00:03:47.740 like even background music that I don't even 00:03:47.740 --> 00:03:49.900 care that much about. 00:03:49.900 --> 00:03:51.730 Someday-- I mean, I think these are really 00:03:51.730 --> 00:03:53.090 stunning individual differences. 00:03:53.090 --> 00:03:54.830 I don't know if there's any good work on it. 00:03:54.830 --> 00:03:55.580 I haven't seen it. 00:03:55.580 --> 00:03:58.190 But I think it's really interesting. 00:03:58.190 --> 00:03:58.900 Some people can. 00:03:58.900 --> 00:03:59.650 Some people can't. 00:03:59.650 --> 00:04:02.740 I don't know what's up with that. 00:04:02.740 --> 00:04:07.343 How about recognizing faces and scenes at the same time? 00:04:07.343 --> 00:04:08.010 Can you do that? 00:04:08.010 --> 00:04:08.460 Yeah? 00:04:08.460 --> 00:04:10.543 How many people feel like you can recognize a face 00:04:10.543 --> 00:04:12.095 and a scene at the same time? 00:04:12.095 --> 00:04:15.210 All right. 00:04:15.210 --> 00:04:17.850 In fact, Michael Cohen, who gave that lecture 00:04:17.850 --> 00:04:21.990 on brain-computer interfaces a month ago or so, 00:04:21.990 --> 00:04:25.230 showed some beautiful work that, actually, you 00:04:25.230 --> 00:04:29.700 are better at recognizing a face and a scene presented 00:04:29.700 --> 00:04:35.550 simultaneously than two faces or two scenes. 00:04:35.550 --> 00:04:38.430 Can you think why that might be? 00:04:38.430 --> 00:04:39.720 Yeah, Isabelle? 00:04:39.720 --> 00:04:40.977 AUDIENCE: Context. 00:04:40.977 --> 00:04:42.060 NANCY KANWISHER: Say more. 00:04:44.880 --> 00:04:50.960 AUDIENCE: If you see somebody, even a familiar face, 00:04:50.960 --> 00:04:52.780 you can either-- 00:04:52.780 --> 00:04:55.970 it helps identify them as, oh, I know that person. 00:04:55.970 --> 00:04:57.412 Then, obviously, they're there. 00:04:57.412 --> 00:04:58.370 NANCY KANWISHER: Right. 00:04:58.370 --> 00:05:00.710 So they can go together into a thing, maybe chunk 00:05:00.710 --> 00:05:01.985 it as a thing or something. 00:05:01.985 --> 00:05:02.860 That's a good answer. 00:05:02.860 --> 00:05:05.210 It wasn't the one I was fishing for. 00:05:05.210 --> 00:05:07.250 Yeah, Jimmy? 00:05:07.250 --> 00:05:12.950 AUDIENCE: If people and places are separate things 00:05:12.950 --> 00:05:15.980 that your brain calculates, if it's two faces, 00:05:15.980 --> 00:05:19.250 you have to calculate this thing with a face number one 00:05:19.250 --> 00:05:21.230 before going to face number two. 00:05:21.230 --> 00:05:24.140 Whereas if it's [INAUDIBLE] 00:05:24.140 --> 00:05:25.640 NANCY KANWISHER: Exactly. 00:05:25.640 --> 00:05:26.360 Exactly. 00:05:26.360 --> 00:05:27.470 And you do, right? 00:05:27.470 --> 00:05:28.820 You have an FFA and a PPA. 00:05:28.820 --> 00:05:30.620 And they're friends, right? 00:05:30.620 --> 00:05:33.470 So what Michael showed is not just that you 00:05:33.470 --> 00:05:36.260 can recognize a face and hold it in working memory, 00:05:36.260 --> 00:05:39.710 a face and a scene better than two faces or two scenes, 00:05:39.710 --> 00:05:42.320 but the degree to which you have that cost 00:05:42.320 --> 00:05:44.000 of doing two things in one category 00:05:44.000 --> 00:05:46.220 rather than spreading over two categories 00:05:46.220 --> 00:05:50.210 is linearly proportional to how different the activation 00:05:50.210 --> 00:05:51.710 patterns are for those categories 00:05:51.710 --> 00:05:53.390 in the ventral visual pathway. 00:05:53.390 --> 00:05:56.040 So faces and scenes are totally different from each other. 00:05:56.040 --> 00:06:00.860 And so you get a big benefit for separating your two items 00:06:00.860 --> 00:06:03.530 across faces and scenes. 00:06:03.530 --> 00:06:05.660 Other things that are more similar in their pattern 00:06:05.660 --> 00:06:08.960 of response in the ventral pathway, like faces and bodies, 00:06:08.960 --> 00:06:10.620 you get a smaller benefit. 00:06:10.620 --> 00:06:11.120 OK? 00:06:11.120 --> 00:06:12.495 So it's consistent with this idea 00:06:12.495 --> 00:06:15.230 that, to the degree that we have separate processors, 00:06:15.230 --> 00:06:21.020 you can do, to some extent, processing in parallel, OK? 00:06:21.020 --> 00:06:25.127 It doesn't explain why not everybody can read and listen 00:06:25.127 --> 00:06:26.210 to music at the same time. 00:06:26.210 --> 00:06:27.752 Because, as I argued a few weeks ago, 00:06:27.752 --> 00:06:29.543 these things don't overlap at all. 00:06:29.543 --> 00:06:30.710 So there are many mysteries. 00:06:30.710 --> 00:06:33.660 But there's some intuition there. 00:06:33.660 --> 00:06:35.910 OK, to get a little more intuition 00:06:35.910 --> 00:06:38.533 about limited processing capacity, can you guys see? 00:06:38.533 --> 00:06:40.200 When I was sitting over there last time, 00:06:40.200 --> 00:06:42.100 I couldn't see the screen at all. 00:06:42.100 --> 00:06:43.360 Can you guys see it? 00:06:43.360 --> 00:06:43.860 It's OK? 00:06:43.860 --> 00:06:44.400 All right. 00:06:44.400 --> 00:06:45.185 Yeah? 00:06:45.185 --> 00:06:51.063 AUDIENCE: Do you think the problem is [INAUDIBLE] 00:06:51.063 --> 00:06:52.230 NANCY KANWISHER: Not for me. 00:06:52.230 --> 00:06:55.120 Instrumental music, no lyrics still a problem. 00:06:55.120 --> 00:06:55.833 So I don't know. 00:06:55.833 --> 00:06:57.750 I mean, I'm sure there's a literature on this. 00:06:57.750 --> 00:06:58.740 I just don't happen to know it. 00:06:58.740 --> 00:07:00.610 I'm just trying to share the intuition. 00:07:00.610 --> 00:07:03.240 So I don't-- it's not the only thing for me. 00:07:06.520 --> 00:07:09.220 OK, so what I'm going to do-- this is a super low-tech demo. 00:07:09.220 --> 00:07:11.613 I'm going to show you an array of colored letters. 00:07:11.613 --> 00:07:13.030 Grab a piece of paper or something 00:07:13.030 --> 00:07:14.800 where you can write down a few letters. 00:07:14.800 --> 00:07:17.350 And I'm just going to flash up one array very quickly. 00:07:17.350 --> 00:07:20.740 And I want you to write down as many of the blue letters 00:07:20.740 --> 00:07:21.820 as you can. 00:07:21.820 --> 00:07:22.510 OK, ready? 00:07:30.275 --> 00:07:31.400 There's only a few of them. 00:07:31.400 --> 00:07:32.380 So you can. 00:07:32.380 --> 00:07:32.980 OK, ready? 00:07:32.980 --> 00:07:33.550 Here we go. 00:07:36.277 --> 00:07:37.110 OK, write them down. 00:07:39.820 --> 00:07:41.320 Last year, everyone got all of them. 00:07:41.320 --> 00:07:43.560 So I tried to go a little faster this time. 00:07:43.560 --> 00:07:45.938 OK. 00:07:45.938 --> 00:07:47.230 OK, we're going to do it again. 00:07:47.230 --> 00:07:48.000 Ready? 00:07:48.000 --> 00:07:49.110 There's going to be another display, 00:07:49.110 --> 00:07:50.730 and you're going to write down all the blue letters. 00:07:50.730 --> 00:07:51.720 Everyone ready? 00:07:51.720 --> 00:07:52.230 Here we go. 00:07:58.520 --> 00:08:00.830 OK, just wanted to share the intuition. 00:08:00.830 --> 00:08:04.050 The probability-- did anyone miss the N here? 00:08:04.050 --> 00:08:06.755 OK, how many people got the N? 00:08:06.755 --> 00:08:07.880 Nobody's going to admit it. 00:08:10.780 --> 00:08:13.150 I wanted a few people to miss the N, right? 00:08:13.150 --> 00:08:14.210 I really did zip through. 00:08:14.210 --> 00:08:16.317 I probably cheated and made this one go faster. 00:08:16.317 --> 00:08:16.900 You missed it? 00:08:16.900 --> 00:08:17.647 OK, thank you. 00:08:17.647 --> 00:08:18.730 I'm sure a few others did. 00:08:18.730 --> 00:08:24.760 OK, anyway, the point is that, if you do this 00:08:24.760 --> 00:08:26.500 properly in a lab, the probability 00:08:26.500 --> 00:08:30.340 of detecting it here is much less than there, right? 00:08:30.340 --> 00:08:33.315 So what does this show? 00:08:33.315 --> 00:08:34.940 It shows that we have limited capacity. 00:08:34.940 --> 00:08:37.429 We can't process all of those blue letters 00:08:37.429 --> 00:08:39.770 in parallel, right? 00:08:39.770 --> 00:08:41.909 When there's a single one, you get it just fine. 00:08:41.909 --> 00:08:44.120 But when there's a bunch, you don't necessarily 00:08:44.120 --> 00:08:45.620 get it, right? 00:08:45.620 --> 00:08:47.090 OK. 00:08:47.090 --> 00:08:49.700 It also shows that we have ability to select 00:08:49.700 --> 00:08:51.530 the information, right? 00:08:51.530 --> 00:08:53.695 So you weren't bothered by the red letters. 00:08:53.695 --> 00:08:55.820 If I'd asked you right after about the red letters, 00:08:55.820 --> 00:08:58.970 you probably couldn't report any of them at all, right? 00:08:58.970 --> 00:09:00.800 It's a whole field that studies that. 00:09:00.800 --> 00:09:02.450 We won't get into that. 00:09:02.450 --> 00:09:04.310 OK. 00:09:04.310 --> 00:09:06.740 So in fact, the probability of reporting 00:09:06.740 --> 00:09:10.220 the N in these two displays is independent of the number 00:09:10.220 --> 00:09:11.420 of red letters. 00:09:11.420 --> 00:09:12.930 They just don't matter. 00:09:12.930 --> 00:09:16.040 They are not entering into that limitation, whatever it is. 00:09:16.040 --> 00:09:17.630 The limitation is only for the ones 00:09:17.630 --> 00:09:23.400 you're paying attention to, the blue ones, OK? 00:09:23.400 --> 00:09:29.370 OK, so why is our mental capacity limited? 00:09:29.370 --> 00:09:30.630 OK? 00:09:30.630 --> 00:09:32.100 Nobody really knows an answer. 00:09:32.100 --> 00:09:34.890 And I actually think this is a really unsatisfying part 00:09:34.890 --> 00:09:37.780 of attention research because it sort of seems obvious. 00:09:37.780 --> 00:09:39.120 But I think it's not. 00:09:39.120 --> 00:09:42.120 So sometime in the next 10 or 20 years, 00:09:42.120 --> 00:09:45.780 some smart computational person will analyze this well and get 00:09:45.780 --> 00:09:46.960 a more satisfying answer. 00:09:46.960 --> 00:09:48.418 But right now, here's where we are. 00:09:50.760 --> 00:09:55.290 The standard story is, well, we have only so many neurons 00:09:55.290 --> 00:09:56.370 and so much capacity. 00:09:56.370 --> 00:09:59.730 And you can't do everything at once, right? 00:09:59.730 --> 00:10:02.280 So we can't process everything in the whole visual field 00:10:02.280 --> 00:10:04.790 at once. 00:10:04.790 --> 00:10:06.920 That's the standard story. 00:10:06.920 --> 00:10:09.070 But the reason I find this unsatisfying is like, 00:10:09.070 --> 00:10:10.070 why the hell not, right? 00:10:10.070 --> 00:10:13.310 We have all this parallel stuff or the whole visual field, 00:10:13.310 --> 00:10:15.590 at least in the first few stages of processing. 00:10:15.590 --> 00:10:18.440 And we have quite a degree of parallelism after that. 00:10:18.440 --> 00:10:20.270 So I think that's the standard story. 00:10:20.270 --> 00:10:23.480 But I'm just marking that I don't find it very satisfying. 00:10:23.480 --> 00:10:26.090 Yeah? 00:10:26.090 --> 00:10:28.490 A second answer, which I think is also not 00:10:28.490 --> 00:10:31.970 totally satisfying but also a little bit right at least, 00:10:31.970 --> 00:10:35.310 is that, typically, you're only going to do one action. 00:10:35.310 --> 00:10:35.810 Right? 00:10:35.810 --> 00:10:37.185 You're going around in the world. 00:10:37.185 --> 00:10:40.080 Let's forget colored letters on a display in a lab. 00:10:40.080 --> 00:10:43.190 Let's think about a person walking around in a busy city 00:10:43.190 --> 00:10:45.150 street doing something, right? 00:10:45.150 --> 00:10:48.200 There's typically only one or a very small number 00:10:48.200 --> 00:10:50.450 of things you're going to do next, like walk down 00:10:50.450 --> 00:10:52.220 the sidewalk and not bump into people 00:10:52.220 --> 00:10:54.740 or pick up this object, right? 00:10:54.740 --> 00:10:58.430 You don't need to act towards all the things in your world. 00:10:58.430 --> 00:11:01.160 And in fact, if you had to, so given 00:11:01.160 --> 00:11:03.230 that you're only going to do one thing, why 00:11:03.230 --> 00:11:05.720 distract the whole rest of your motor-planning system 00:11:05.720 --> 00:11:07.970 by feeding it all this information that's is just 00:11:07.970 --> 00:11:09.470 going to clutter it with garbage? 00:11:09.470 --> 00:11:12.185 Why not give it just the information it needs? 00:11:12.185 --> 00:11:13.560 OK, so that's the standard story. 00:11:13.560 --> 00:11:18.410 It's very squishy and vague but hopefully intuitive. 00:11:18.410 --> 00:11:22.340 And there's some nice, compelling examples 00:11:22.340 --> 00:11:23.430 that illustrate this. 00:11:23.430 --> 00:11:25.730 So there's a fish called the pike fish 00:11:25.730 --> 00:11:28.460 that preys on smaller fish called sticklebacks. 00:11:28.460 --> 00:11:29.510 OK? 00:11:29.510 --> 00:11:34.640 And if you stick a pike fish in a tank with sticklebacks, 00:11:34.640 --> 00:11:36.500 it will catch the first stickleback 00:11:36.500 --> 00:11:39.620 faster if there's only one in the tank with it 00:11:39.620 --> 00:11:42.690 than if there are 10 in the tank with it. 00:11:42.690 --> 00:11:43.190 OK? 00:11:43.190 --> 00:11:45.710 You might think, you've got 10 to choose from. 00:11:45.710 --> 00:11:47.810 You'll get a fish faster. 00:11:47.810 --> 00:11:50.420 But 10 is more distracting, right? 00:11:50.420 --> 00:11:52.700 And so maybe our action-planning systems also 00:11:52.700 --> 00:11:55.430 prefer the single stickleback. 00:11:55.430 --> 00:11:57.440 Again, there's no computational precision. 00:11:57.440 --> 00:12:00.110 I'm just sharing intuitions with you. 00:12:00.110 --> 00:12:03.890 OK, so let me give you some more evidence that there really 00:12:03.890 --> 00:12:09.377 are significant capacity limits in perception 00:12:09.377 --> 00:12:11.960 and that, in fact, there's a lot of stuff right in front of us 00:12:11.960 --> 00:12:15.800 that comes right onto our retina that we don't see. 00:12:15.800 --> 00:12:17.000 OK? 00:12:17.000 --> 00:12:19.350 So I'm going to show you an example. 00:12:19.350 --> 00:12:21.740 I'm going to show you a picture for just a few seconds. 00:12:21.740 --> 00:12:22.970 And I want you to just look at it. 00:12:22.970 --> 00:12:24.770 And then I'm going to ask you some questions about it. 00:12:24.770 --> 00:12:25.070 OK? 00:12:25.070 --> 00:12:25.640 Here we go. 00:12:28.710 --> 00:12:33.300 OK, so how rich a percept did you get? 00:12:33.300 --> 00:12:37.335 Did you see lots of stuff and get lots of detail? 00:12:37.335 --> 00:12:38.710 Or do you just feel like you just 00:12:38.710 --> 00:12:42.400 have the vaguest sense of a few buildings, a street, that's it? 00:12:42.400 --> 00:12:47.450 How many feel like they got a lot of pretty good detail? 00:12:47.450 --> 00:12:48.222 No one does. 00:12:48.222 --> 00:12:49.055 Or everyone's bored. 00:12:49.055 --> 00:12:51.578 I don't know which. 00:12:51.578 --> 00:12:54.200 AUDIENCE: What do you mean good detail? 00:12:54.200 --> 00:12:56.450 NANCY KANWISHER: The colors of buildings, the presence 00:12:56.450 --> 00:12:59.840 of objects, details on the architectural styles, 00:12:59.840 --> 00:13:02.878 where an awning was, that kind of thing. 00:13:02.878 --> 00:13:08.228 AUDIENCE: I feel like I got [INAUDIBLE] 00:13:08.228 --> 00:13:10.520 NANCY KANWISHER: Well, most people looking at this feel 00:13:10.520 --> 00:13:10.760 like-- 00:13:10.760 --> 00:13:11.900 I mean, who knows what it means? 00:13:11.900 --> 00:13:13.692 I mean, we're just sharing intuitions here. 00:13:13.692 --> 00:13:15.495 But most feel like, that was pretty rich. 00:13:15.495 --> 00:13:16.370 I have a sense of it. 00:13:16.370 --> 00:13:18.162 I have a sense of maybe what country that's 00:13:18.162 --> 00:13:19.610 in and what kind of stuff is there 00:13:19.610 --> 00:13:21.482 and what kind the style is. 00:13:21.482 --> 00:13:23.690 You get a feel for the place, all that kind of thing. 00:13:23.690 --> 00:13:26.930 Maybe not every damn detail, but lots, right? 00:13:26.930 --> 00:13:28.880 So the general intuition most people have 00:13:28.880 --> 00:13:31.400 is a fair amount of detail. 00:13:31.400 --> 00:13:33.050 OK? 00:13:33.050 --> 00:13:34.550 Well, let's look at that some more. 00:13:34.550 --> 00:13:38.870 This is actually a very, very heated topic right now. 00:13:38.870 --> 00:13:41.600 Me and Michael Cohen published a paper a couple of years 00:13:41.600 --> 00:13:44.030 ago called The Bandwidth of Perception, which is an effort 00:13:44.030 --> 00:13:46.940 to grapple with this question of how much information is there 00:13:46.940 --> 00:13:48.710 in your current percept right now. 00:13:48.710 --> 00:13:51.360 And there are many different perspectives on this. 00:13:51.360 --> 00:13:54.810 Let's find out a little more with a further demo. 00:13:54.810 --> 00:13:57.380 So what I'm going to do is I'm going 00:13:57.380 --> 00:14:01.040 to show you that picture again. 00:14:01.040 --> 00:14:03.690 And it's going to flash on a number of times. 00:14:03.690 --> 00:14:05.150 And each time it flashes on, there 00:14:05.150 --> 00:14:07.050 might be something that's different. 00:14:07.050 --> 00:14:10.640 So take notes on any differences you might detect. 00:14:10.640 --> 00:14:12.685 OK? 00:14:12.685 --> 00:14:13.185 OK. 00:14:40.380 --> 00:14:42.280 OK, what things changed? 00:14:42.280 --> 00:14:42.780 Yeah? 00:14:42.780 --> 00:14:45.030 AUDIENCE: There was a woman walking down the sidewalk. 00:14:45.030 --> 00:14:46.290 NANCY KANWISHER: And? 00:14:46.290 --> 00:14:47.598 AUDIENCE: That's all I got. 00:14:47.598 --> 00:14:49.140 NANCY KANWISHER: OK, but she changed. 00:14:49.140 --> 00:14:51.840 What changed about her? 00:14:51.840 --> 00:14:54.793 AUDIENCE: Other than her clothes? 00:14:54.793 --> 00:14:55.710 NANCY KANWISHER: Yeah. 00:14:55.710 --> 00:14:57.450 Over the successive presentations, 00:14:57.450 --> 00:14:59.190 was she there sometimes and not others? 00:14:59.190 --> 00:14:59.820 Did she change? 00:14:59.820 --> 00:15:01.500 Yeah, she appeared or disappeared. 00:15:01.500 --> 00:15:02.010 OK, good. 00:15:02.010 --> 00:15:03.394 What else, Isabel? 00:15:03.394 --> 00:15:04.846 AUDIENCE: The awnings changed. 00:15:04.846 --> 00:15:06.835 The buildings changed colors. 00:15:06.835 --> 00:15:07.960 NANCY KANWISHER: Very good. 00:15:07.960 --> 00:15:08.710 Very good. 00:15:08.710 --> 00:15:12.790 How many people saw an awning change? 00:15:12.790 --> 00:15:14.560 Maybe half of you. 00:15:14.560 --> 00:15:15.370 OK. 00:15:15.370 --> 00:15:17.878 What else changed? 00:15:17.878 --> 00:15:19.238 AUDIENCE: The car. 00:15:19.238 --> 00:15:20.530 AUDIENCE: The model of the car. 00:15:20.530 --> 00:15:21.640 NANCY KANWISHER: The model of the car. 00:15:21.640 --> 00:15:22.390 Very good. 00:15:22.390 --> 00:15:22.900 Yeah? 00:15:22.900 --> 00:15:25.300 AUDIENCE: I feel like the shops changed. 00:15:25.300 --> 00:15:27.930 But I don't know when or how. 00:15:27.930 --> 00:15:30.590 NANCY KANWISHER: OK. 00:15:30.590 --> 00:15:31.090 OK. 00:15:31.090 --> 00:15:32.770 You want to see how they changed? 00:15:32.770 --> 00:15:34.600 OK, here's how it ended. 00:15:34.600 --> 00:15:36.460 Here's how it started. 00:15:36.460 --> 00:15:38.140 Are you surprised how much? 00:15:38.140 --> 00:15:40.600 Raise your hand if you're surprised how much changed. 00:15:40.600 --> 00:15:43.410 Yeah, a lot, right? 00:15:43.410 --> 00:15:45.910 OK, so what does that tell us? 00:15:45.910 --> 00:15:49.680 It tells us that either the sense 00:15:49.680 --> 00:15:52.950 we have that we really saw a lot of what's going on there 00:15:52.950 --> 00:15:53.460 was wrong. 00:15:53.460 --> 00:15:54.960 We didn't see as much as we thought. 00:15:54.960 --> 00:15:56.910 Because if we saw as much as we thought, 00:15:56.910 --> 00:15:59.343 we should notice massive changes like that. 00:15:59.343 --> 00:16:01.260 If you didn't see the awning, look over there. 00:16:01.260 --> 00:16:04.560 I mean, how could-- look at the color changes. 00:16:04.560 --> 00:16:06.630 Pretty major, right? 00:16:06.630 --> 00:16:09.360 Or we perceive all that stuff in the instant, 00:16:09.360 --> 00:16:12.255 and it just goes poof by the time the next one comes along. 00:16:12.255 --> 00:16:14.130 That's one of the things the field is finding 00:16:14.130 --> 00:16:16.088 about those things are very hard to tell apart, 00:16:16.088 --> 00:16:17.640 not impossible, but hard. 00:16:17.640 --> 00:16:19.710 Yeah. 00:16:19.710 --> 00:16:23.190 OK, so most people feel like, wow, much more changed 00:16:23.190 --> 00:16:24.450 than I thought. 00:16:24.450 --> 00:16:28.230 I can't resist one more hilarious demo. 00:16:28.230 --> 00:16:30.990 So have you already seen this like in 9.00? 00:16:30.990 --> 00:16:33.080 How many people have seen this before? 00:16:33.080 --> 00:16:34.503 Oh, I don't want to bore you. 00:16:34.503 --> 00:16:35.670 Do you mind seeing it again? 00:16:35.670 --> 00:16:36.690 We could skip it. 00:16:36.690 --> 00:16:38.110 It's kind of fun. 00:16:38.110 --> 00:16:38.610 Sorry? 00:16:38.610 --> 00:16:38.880 Do it? 00:16:38.880 --> 00:16:39.420 OK. 00:16:39.420 --> 00:16:41.440 OK. 00:16:41.440 --> 00:16:41.940 OK. 00:16:41.940 --> 00:16:44.310 So you're just going to watch this video and just 00:16:44.310 --> 00:16:45.905 track things because there may be 00:16:45.905 --> 00:16:47.280 changes happening here and there, 00:16:47.280 --> 00:16:49.090 and you want to notice them, OK? 00:16:49.090 --> 00:16:49.590 Here we go. 00:16:49.590 --> 00:16:53.173 [MUSIC PLAYING] 00:16:53.173 --> 00:16:53.840 [VIDEO PLAYBACK] 00:16:53.840 --> 00:16:57.350 - Clearly, somebody in this room murdered Lord Smythe, 00:16:57.350 --> 00:17:00.860 who, at precisely 3:34 this afternoon, 00:17:00.860 --> 00:17:04.770 was brutally bludgeoned to death with a blunt instrument. 00:17:04.770 --> 00:17:07.970 I want each of you to tell me your whereabouts 00:17:07.970 --> 00:17:13.290 at precisely the time that this dastardly deed took place. 00:17:13.290 --> 00:17:17.069 - I was polishing the brass in the master bedroom. 00:17:17.069 --> 00:17:21.380 - I was buttering his lordship's scones below stairs, sir. 00:17:21.380 --> 00:17:24.800 - I was planting my petunias in the potting shed. 00:17:24.800 --> 00:17:29.340 - Constable, arrest Lady Smythe. 00:17:29.340 --> 00:17:30.140 - How did you know? 00:17:30.140 --> 00:17:32.250 - Madam, as any horticulturist will tell you, 00:17:32.250 --> 00:17:35.060 one does not plant petunias until May is out. 00:17:35.060 --> 00:17:37.010 Take her away. 00:17:37.010 --> 00:17:39.080 It's just a matter of observation. 00:17:39.080 --> 00:17:42.440 The real question is, how observant were you? 00:17:51.380 --> 00:17:54.920 Clearly, somebody in this room murdered Lord Smythe, 00:17:54.920 --> 00:17:58.490 who at precisely 3:34 this afternoon, 00:17:58.490 --> 00:18:02.280 was brutally bludgeoned to death with a blunt instrument. 00:18:02.280 --> 00:18:05.540 I want each of you to tell me your whereabouts 00:18:05.540 --> 00:18:08.587 at precisely the time that this dastardly deed took place. 00:18:08.587 --> 00:18:09.170 [END PLAYBACK] 00:18:09.170 --> 00:18:10.070 NANCY KANWISHER: Totally different guy. 00:18:10.070 --> 00:18:10.737 [VIDEO PLAYBACK] 00:18:10.737 --> 00:18:14.510 - I was polishing the brass in the master bedroom. 00:18:14.510 --> 00:18:18.890 - I was buttering his lordship's scones below stairs, sir. 00:18:18.890 --> 00:18:22.280 - I was planting my petunias in the potting shed. 00:18:22.280 --> 00:18:25.520 - Constable, arrest Lady Smythe. 00:18:29.091 --> 00:18:29.674 [END PLAYBACK] 00:18:29.674 --> 00:18:31.216 NANCY KANWISHER: It's actually an ad. 00:18:31.216 --> 00:18:33.110 But it doesn't hurt to get its message. 00:18:36.480 --> 00:18:42.270 All right, it's a British ad with an important message. 00:18:42.270 --> 00:18:44.815 But it's a pretty impressive demo too, isn't it? 00:18:44.815 --> 00:18:46.440 How many people feel like lots of stuff 00:18:46.440 --> 00:18:48.720 changed that they didn't notice? 00:18:48.720 --> 00:18:50.940 Yeah, that's intuition. 00:18:50.940 --> 00:18:54.630 So the idea here is that all that stuff hits your retina. 00:18:54.630 --> 00:18:57.300 All of it kind of gets processed to some degree. 00:18:57.300 --> 00:19:00.810 But it's amazing how much of it goes unnoticed. 00:19:00.810 --> 00:19:02.060 OK? 00:19:02.060 --> 00:19:03.020 All right, oops. 00:19:03.020 --> 00:19:04.490 Sorry. 00:19:04.490 --> 00:19:08.050 OK, you might think, OK, is this something that only happens 00:19:08.050 --> 00:19:09.300 when it doesn't really matter? 00:19:09.300 --> 00:19:10.790 OK, you were looking for changes. 00:19:10.790 --> 00:19:12.740 But your life didn't depend on it. 00:19:12.740 --> 00:19:14.900 What about commercial pilots? 00:19:14.900 --> 00:19:16.610 So here's a classic study where they 00:19:16.610 --> 00:19:19.940 brought in actual real commercial pilots 00:19:19.940 --> 00:19:23.210 with thousands of hours of flying experience. 00:19:23.210 --> 00:19:25.910 And they had them fly in a flight simulator. 00:19:25.910 --> 00:19:30.860 They had them land a plane on a runway in the flight simulator 00:19:30.860 --> 00:19:33.080 under foggy conditions. 00:19:33.080 --> 00:19:34.850 And I forget what percent. 00:19:34.850 --> 00:19:37.045 I have to cheat and look at my notes. 00:19:37.045 --> 00:19:38.270 It doesn't say. 00:19:38.270 --> 00:19:38.810 It does. 00:19:38.810 --> 00:19:39.768 I'm just not seeing it. 00:19:39.768 --> 00:19:43.220 Some large percent of the pilots never 00:19:43.220 --> 00:19:46.880 saw this plane sitting right there on the runway. 00:19:46.880 --> 00:19:49.880 They landed the planes in the simulator right 00:19:49.880 --> 00:19:51.142 through that plane. 00:19:51.142 --> 00:19:52.850 And when they were shown it subsequently, 00:19:52.850 --> 00:19:54.433 they were shocked and couldn't believe 00:19:54.433 --> 00:19:55.820 they didn't see it, right? 00:19:55.820 --> 00:19:57.430 They were using a heads-up display 00:19:57.430 --> 00:19:58.805 that tells them their orientation 00:19:58.805 --> 00:19:59.900 to where the runway is. 00:19:59.900 --> 00:20:01.700 And they're paying attention to this stuff, 00:20:01.700 --> 00:20:02.720 landing on the runway. 00:20:02.720 --> 00:20:06.830 And they just do not even see that very relevant thing, OK? 00:20:06.830 --> 00:20:10.160 So it's not just something that happens in like weird psych 00:20:10.160 --> 00:20:12.440 demos and funny movies. 00:20:12.440 --> 00:20:17.480 Even for very important things, people miss absolutely major, 00:20:17.480 --> 00:20:19.600 important information. 00:20:19.600 --> 00:20:23.500 OK, so what all this tells us is attention 00:20:23.500 --> 00:20:28.060 is a filter that lets some information into our awareness 00:20:28.060 --> 00:20:30.760 but completely filters out of awareness 00:20:30.760 --> 00:20:32.890 a lot of other information that lands 00:20:32.890 --> 00:20:35.410 on your retina or your cochlea. 00:20:35.410 --> 00:20:37.660 OK? 00:20:37.660 --> 00:20:39.880 And there's two key properties of attention 00:20:39.880 --> 00:20:41.110 that go hand-in-hand. 00:20:41.110 --> 00:20:43.360 One, those capacity limits we've been talking about. 00:20:43.360 --> 00:20:45.290 You can't do everything at once. 00:20:45.290 --> 00:20:48.160 And two, selectivity, that is there's 00:20:48.160 --> 00:20:50.470 some way some subset of that information 00:20:50.470 --> 00:20:54.000 comes in some way to select it, OK? 00:20:54.000 --> 00:20:57.030 All right, so let's say a little bit more about attention. 00:20:57.030 --> 00:20:59.760 There's lots of different ways and forms of attention. 00:20:59.760 --> 00:21:04.420 So let me give you a few key distinctions about attention. 00:21:04.420 --> 00:21:06.420 So far, it's just kind of a vague word that gets 00:21:06.420 --> 00:21:08.860 used lots of different ways. 00:21:08.860 --> 00:21:13.620 So long ago, the great Helmholtz thought about attention 00:21:13.620 --> 00:21:16.650 and realized that there were two different kinds of attention. 00:21:16.650 --> 00:21:20.880 So he noted way back in 1860, our attention 00:21:20.880 --> 00:21:23.760 is quite independent of the position and accommodation 00:21:23.760 --> 00:21:27.840 of the eyes and of any known alteration in these organs 00:21:27.840 --> 00:21:31.860 and free to direct itself by a conscious and voluntary effort 00:21:31.860 --> 00:21:35.400 upon any selected portion of a dark and undifferentiated field 00:21:35.400 --> 00:21:36.460 of view. 00:21:36.460 --> 00:21:38.460 This is one of the most important observations 00:21:38.460 --> 00:21:40.890 for a future theory of attention. 00:21:40.890 --> 00:21:43.050 Indeed, it is, right? 00:21:43.050 --> 00:21:45.780 So his point-- I think we did this at some earlier lecture. 00:21:45.780 --> 00:21:49.350 His point is you can fixate on my nose right now. 00:21:49.350 --> 00:21:51.540 OK, everybody fixate on my nose. 00:21:51.540 --> 00:21:53.070 Not that it's that fabulous a nose. 00:21:53.070 --> 00:21:55.020 It'll just serve for the demo right now. 00:21:55.020 --> 00:21:58.860 And if I hold up different numbers of fingers out here-- 00:21:58.860 --> 00:22:00.120 keep fixating on my nose. 00:22:00.120 --> 00:22:01.530 No cheating. 00:22:01.530 --> 00:22:02.700 OK? 00:22:02.700 --> 00:22:06.570 How many fingers are off to the left side of my nose 00:22:06.570 --> 00:22:08.280 from your perspective? 00:22:08.280 --> 00:22:09.060 OK. 00:22:09.060 --> 00:22:11.250 How many fingers are off to the right side? 00:22:11.250 --> 00:22:12.060 OK. 00:22:12.060 --> 00:22:13.020 You can do that. 00:22:13.020 --> 00:22:15.750 You can pull up this information or pull up that information 00:22:15.750 --> 00:22:17.640 without moving your eyes. 00:22:17.640 --> 00:22:18.180 OK? 00:22:18.180 --> 00:22:22.380 That's called covert attention because the input is identical. 00:22:22.380 --> 00:22:24.240 And you are just somehow adjusting 00:22:24.240 --> 00:22:25.800 the dials on your perceptual system 00:22:25.800 --> 00:22:28.570 to pull up this or pull up that. 00:22:28.570 --> 00:22:29.080 OK? 00:22:29.080 --> 00:22:31.840 So that's called covert attention. 00:22:31.840 --> 00:22:34.150 To be unconfounded from overt attention, 00:22:34.150 --> 00:22:36.430 which is actually the most powerful kind of attention. 00:22:36.430 --> 00:22:38.890 Overt attention, you move your eyes from point 00:22:38.890 --> 00:22:41.830 to point to select different information. 00:22:41.830 --> 00:22:46.420 OK, so overt attention is a much more powerful filter. 00:22:46.420 --> 00:22:49.570 And we make about two to four eye movements a second. 00:22:49.570 --> 00:22:52.000 And it's very powerful because the center of gaze 00:22:52.000 --> 00:22:53.890 has very high resolution information. 00:22:53.890 --> 00:22:55.840 Remember high density of photoreceptors 00:22:55.840 --> 00:22:58.030 at the fovea in the center of gaze, 00:22:58.030 --> 00:23:01.070 and the density tails off in the periphery. 00:23:01.070 --> 00:23:04.060 So we have much better information in the fovea 00:23:04.060 --> 00:23:06.040 than in the periphery. 00:23:06.040 --> 00:23:07.990 OK, so it's both photoreceptor density, 00:23:07.990 --> 00:23:10.540 and it's also cortical area. 00:23:10.540 --> 00:23:12.910 So in retinotopic cortex, back here, 00:23:12.910 --> 00:23:16.300 primary visual cortex, V1, V2, those regions, 00:23:16.300 --> 00:23:20.260 you have about 20 square centimeters of cortex, 00:23:20.260 --> 00:23:22.000 like that area of cortex-- 00:23:22.000 --> 00:23:25.750 pretty big-- something like that processing the central two 00:23:25.750 --> 00:23:27.350 degrees of vision. 00:23:27.350 --> 00:23:27.850 OK? 00:23:27.850 --> 00:23:30.820 Huge cortical area devoted to a tiny little part 00:23:30.820 --> 00:23:32.120 of the visual world. 00:23:32.120 --> 00:23:36.340 And much less per degree for the periphery. 00:23:36.340 --> 00:23:38.230 OK, so both at the photoreceptor stage 00:23:38.230 --> 00:23:40.060 and at higher-level processing stages, 00:23:40.060 --> 00:23:43.180 we vastly over represent the center of gaze. 00:23:43.180 --> 00:23:43.930 OK? 00:23:43.930 --> 00:23:46.690 That's why if you have loss of foveal vision and macular 00:23:46.690 --> 00:23:48.190 degeneration, it's really awful. 00:23:48.190 --> 00:23:49.990 You can't read or recognize faces. 00:23:49.990 --> 00:23:52.000 That's where you need this fine-grained foveal 00:23:52.000 --> 00:23:53.260 information. 00:23:53.260 --> 00:23:56.860 OK, so that means that moving your fovea 00:23:56.860 --> 00:23:58.930 and parking it on different parts of the array 00:23:58.930 --> 00:24:01.360 is an extremely powerful way to select 00:24:01.360 --> 00:24:03.350 different kinds of information. 00:24:03.350 --> 00:24:06.340 So to give you a feel for how much people do this 00:24:06.340 --> 00:24:11.020 and how they select information, here's a video. 00:24:11.020 --> 00:24:12.820 This is taken from a head-mounted camera 00:24:12.820 --> 00:24:15.310 of a person who is watching these two people. 00:24:15.310 --> 00:24:18.130 And the yellow dot is where their fovea is. 00:24:18.130 --> 00:24:20.470 So they're talking to my former postdoc Matt. 00:24:20.470 --> 00:24:23.380 And they're fixating on his face as he talks. 00:24:23.380 --> 00:24:26.530 And sometimes they take a peek at the other person. 00:24:26.530 --> 00:24:29.380 And you can see there's very fine-grained adjustments 00:24:29.380 --> 00:24:31.198 of where they look as this goes on. 00:24:31.198 --> 00:24:33.490 And now they're walking down the hall in this building, 00:24:33.490 --> 00:24:34.915 and they're following her. 00:24:34.915 --> 00:24:36.790 Watch what happens when they turn the corner. 00:24:36.790 --> 00:24:38.110 Check out the signs. 00:24:38.110 --> 00:24:40.150 Read the little notices. 00:24:40.150 --> 00:24:41.240 Look down the hall. 00:24:41.240 --> 00:24:43.698 And then watch what happens when they go around the corner. 00:24:43.698 --> 00:24:44.500 Oh, new person. 00:24:44.500 --> 00:24:46.010 Look at the new person. 00:24:46.010 --> 00:24:46.510 Right? 00:24:49.310 --> 00:24:51.410 Sorry, it's too dark to see what's going on here. 00:24:51.410 --> 00:24:52.940 Oh, this is a little fixation patch 00:24:52.940 --> 00:24:56.420 where they're recalibrating the eye tracker to figure out 00:24:56.420 --> 00:24:57.700 to make sure it's working. 00:24:57.700 --> 00:24:58.700 Here comes a new person. 00:24:58.700 --> 00:25:00.110 They look at his face. 00:25:00.110 --> 00:25:03.890 Saccade back and forth between the two faces, right? 00:25:03.890 --> 00:25:05.690 Whoever's talking, you look at them. 00:25:05.690 --> 00:25:07.850 And you collect high-resolution information 00:25:07.850 --> 00:25:08.958 from that person's face. 00:25:08.958 --> 00:25:11.000 With both head turns, you can see their both head 00:25:11.000 --> 00:25:15.520 turns and eye movements. 00:25:15.520 --> 00:25:17.140 OK, you get the idea. 00:25:17.140 --> 00:25:18.250 I didn't totally explain. 00:25:18.250 --> 00:25:22.922 So this is a head-mounted camera and eye tracker, OK, 00:25:22.922 --> 00:25:24.880 of a person who was walking around the building 00:25:24.880 --> 00:25:25.770 encountering people. 00:25:25.770 --> 00:25:28.228 And it was showing you both what was in their field of view 00:25:28.228 --> 00:25:30.890 and where they were fixating their eyes in that view. 00:25:30.890 --> 00:25:33.700 So you can see there's really fine-grained, moment-to-moment 00:25:33.700 --> 00:25:35.620 sampling of visual information all 00:25:35.620 --> 00:25:38.800 the time with overt attention with eye movements, OK? 00:25:38.800 --> 00:25:40.120 Make sense? 00:25:40.120 --> 00:25:41.082 OK. 00:25:41.082 --> 00:25:43.540 OK, first, so that's the first distinction about attention, 00:25:43.540 --> 00:25:45.490 covert versus overt. 00:25:45.490 --> 00:25:46.780 OK? 00:25:46.780 --> 00:25:48.700 Now, you might say, why would we bother 00:25:48.700 --> 00:25:52.120 with this subtle, sophisticated covert attention when 00:25:52.120 --> 00:25:56.100 we can just move our eyes and do overt attention? 00:25:56.100 --> 00:25:58.100 And I think there's a bunch of reasons for that. 00:25:58.100 --> 00:26:01.720 One is other people can see where you're looking. 00:26:01.720 --> 00:26:04.690 And there's sometimes you want to attend to stuff over there 00:26:04.690 --> 00:26:07.390 and not let people know, right? 00:26:07.390 --> 00:26:11.620 So there are many examples of this from elevator eyes, people 00:26:11.620 --> 00:26:13.202 who look you up and down. 00:26:13.202 --> 00:26:14.410 It's not politically correct. 00:26:14.410 --> 00:26:15.250 It's not nice. 00:26:15.250 --> 00:26:16.480 It's not considerate. 00:26:16.480 --> 00:26:18.830 People notice if you do that. 00:26:18.830 --> 00:26:19.600 So don't do it. 00:26:19.600 --> 00:26:23.080 You can covertly attend below the face, if you like. 00:26:23.080 --> 00:26:25.450 But don't overtly move your eyes down there 00:26:25.450 --> 00:26:26.830 because they will know. 00:26:26.830 --> 00:26:27.400 OK? 00:26:27.400 --> 00:26:29.380 We primates are very, very attuned 00:26:29.380 --> 00:26:31.600 to where each other are looking. 00:26:31.600 --> 00:26:35.350 We are the only primate who has whites around the eyes. 00:26:35.350 --> 00:26:37.660 I just heard a talk last week by Michael Tomasello, 00:26:37.660 --> 00:26:40.000 who's one of the major primatologists. 00:26:40.000 --> 00:26:42.250 And he says that the fact that humans 00:26:42.250 --> 00:26:44.770 have whites of their eyes that make it so easy to tell where 00:26:44.770 --> 00:26:47.470 they're looking must mean that we mostly 00:26:47.470 --> 00:26:50.157 want to share information with each other about where 00:26:50.157 --> 00:26:50.740 we're looking. 00:26:50.740 --> 00:26:54.400 We're a very cooperative, communicative species. 00:26:54.400 --> 00:26:55.363 But not always. 00:26:55.363 --> 00:26:57.280 Sometimes we want to sneak a peek at something 00:26:57.280 --> 00:26:58.510 where people don't know. 00:26:58.510 --> 00:27:00.160 The case that I notice all the time is 00:27:00.160 --> 00:27:02.290 I'm at a conference and some very familiar face 00:27:02.290 --> 00:27:03.940 comes along and says, hey, Nancy. 00:27:03.940 --> 00:27:04.450 How are you? 00:27:04.450 --> 00:27:06.520 And I'm thinking, who the hell is this? 00:27:06.520 --> 00:27:09.460 And the whole time, I'm thinking I can see the name right there. 00:27:09.460 --> 00:27:10.600 I can't quite resolve it. 00:27:10.600 --> 00:27:13.480 I know that if saccade down for a half a second, 00:27:13.480 --> 00:27:14.200 they will see it. 00:27:14.200 --> 00:27:15.790 And I will be busted. 00:27:15.790 --> 00:27:18.310 And so I'm sitting there with a name right there racking 00:27:18.310 --> 00:27:20.290 my brain trying to think who the hell it is. 00:27:20.290 --> 00:27:22.623 Anyway, so there are many cases like this where we don't 00:27:22.623 --> 00:27:24.767 want to be caught looking. 00:27:24.767 --> 00:27:26.350 So those are all cases where you might 00:27:26.350 --> 00:27:28.870 want to use covert attention. 00:27:28.870 --> 00:27:30.670 Also, sometimes you want to track 00:27:30.670 --> 00:27:34.240 lots of things in parallel, and you can't foveate all of them. 00:27:34.240 --> 00:27:36.500 You can only foveate one thing. 00:27:36.500 --> 00:27:38.230 So I don't know anything about sports. 00:27:38.230 --> 00:27:40.480 But think of your favorite complicated sports example 00:27:40.480 --> 00:27:42.438 where there are multiple players moving at once 00:27:42.438 --> 00:27:44.270 and you need to keep track of all of them. 00:27:44.270 --> 00:27:46.270 That would be a classic case of covert attention 00:27:46.270 --> 00:27:48.400 because you could covertly attend to several of them 00:27:48.400 --> 00:27:48.900 at once. 00:27:48.900 --> 00:27:50.720 And you have only one fovea. 00:27:50.720 --> 00:27:53.860 Well, you have two, but they go to the same place. 00:27:53.860 --> 00:27:55.720 OK, so that's the second distinction overt 00:27:55.720 --> 00:27:58.150 versus covert-- 00:27:58.150 --> 00:27:58.930 or the first one. 00:27:58.930 --> 00:27:59.430 Right? 00:27:59.430 --> 00:28:03.100 So the next basic distinction of different kinds of attention 00:28:03.100 --> 00:28:05.350 are the kind where we decide where 00:28:05.350 --> 00:28:09.400 we want to look versus the kind where the stimulus draws 00:28:09.400 --> 00:28:11.230 our attention, OK? 00:28:11.230 --> 00:28:13.510 So there are lots of examples. 00:28:13.510 --> 00:28:15.880 Like web pop ups are all designed 00:28:15.880 --> 00:28:18.550 to pull your attention, overt and covert. 00:28:18.550 --> 00:28:20.710 Even you don't want to look at that damn thing. 00:28:20.710 --> 00:28:22.870 But the weird, little dancing figure, 00:28:22.870 --> 00:28:26.710 they're all optimized to pull your attention over and make 00:28:26.710 --> 00:28:28.652 you read the ad, right? 00:28:28.652 --> 00:28:29.860 And they're pretty effective. 00:28:29.860 --> 00:28:32.860 OK, so that's called stimulus-driven attention 00:28:32.860 --> 00:28:34.027 or exogenous attention. 00:28:34.027 --> 00:28:35.110 It comes from the outside. 00:28:35.110 --> 00:28:36.670 And it pulls you in. 00:28:36.670 --> 00:28:38.950 OK? 00:28:38.950 --> 00:28:41.080 Another classic example is pop-out. 00:28:41.080 --> 00:28:42.880 If you look at this display, it's very hard 00:28:42.880 --> 00:28:44.710 not to notice and have your attention drawn 00:28:44.710 --> 00:28:46.450 to that red thing. 00:28:46.450 --> 00:28:48.340 Certain properties of stimuli that just 00:28:48.340 --> 00:28:50.830 automatically capture your attention. 00:28:50.830 --> 00:28:53.200 OK, that is to be contrasted with 00:28:53.200 --> 00:28:54.713 voluntary controlled attention. 00:28:54.713 --> 00:28:56.380 That's like the case we did before where 00:28:56.380 --> 00:28:58.030 you were fixating on my nose. 00:28:58.030 --> 00:29:00.083 It was totally up to you whether attend-- 00:29:00.083 --> 00:29:01.000 I mean, I told you to. 00:29:01.000 --> 00:29:02.350 But you could have made up your own mind 00:29:02.350 --> 00:29:03.460 and attended to neither. 00:29:03.460 --> 00:29:05.350 And I wouldn't have known, right? 00:29:05.350 --> 00:29:07.910 So you can decide what you want to pay attention to. 00:29:07.910 --> 00:29:09.520 And as I think I mentioned in I don't 00:29:09.520 --> 00:29:12.040 know what context a few weeks ago, 00:29:12.040 --> 00:29:14.188 thank God we can decide what to pay attention to. 00:29:14.188 --> 00:29:16.480 Because there's lots of stuff that goes on in the world 00:29:16.480 --> 00:29:18.970 that we don't want to have dominate our mental life. 00:29:18.970 --> 00:29:22.390 And controlled or voluntary attention 00:29:22.390 --> 00:29:25.930 is one way that we can have our mental life dominated 00:29:25.930 --> 00:29:28.420 more by things we want it to be dominated by and less 00:29:28.420 --> 00:29:32.170 by things we don't, right? 00:29:32.170 --> 00:29:33.790 So that's that notion here. 00:29:33.790 --> 00:29:36.190 Like for example, you're sitting here. 00:29:36.190 --> 00:29:37.180 And it's like noon. 00:29:37.180 --> 00:29:38.860 And you're just thinking, OK, I'm really hungry. 00:29:38.860 --> 00:29:39.730 I'm really hungry. 00:29:39.730 --> 00:29:42.130 If you were my dog Charlie, your entire mental life 00:29:42.130 --> 00:29:44.080 for the whole next half an hour would be, I'm so hungry. 00:29:44.080 --> 00:29:44.663 I'm so hungry. 00:29:44.663 --> 00:29:45.760 I'm so hungry. 00:29:45.760 --> 00:29:47.000 But you're a person. 00:29:47.000 --> 00:29:49.235 And so that thought may impinge now and then, 00:29:49.235 --> 00:29:51.610 but you can drive it away and think about something else. 00:29:51.610 --> 00:29:53.620 Because it's not going to get you anywhere 00:29:53.620 --> 00:29:54.913 to focus on how hungry you are. 00:29:54.913 --> 00:29:56.080 I know I just made it worse. 00:29:56.080 --> 00:29:59.170 I'm sorry about that. 00:29:59.170 --> 00:30:00.840 OK. 00:30:00.840 --> 00:30:04.750 OK, the way that scientists have typically 00:30:04.750 --> 00:30:08.830 studied voluntary attention is they ask subjects to do this. 00:30:08.830 --> 00:30:10.300 And much like the case we just did, 00:30:10.300 --> 00:30:12.580 here's kind of very basic paradigm. 00:30:12.580 --> 00:30:14.380 You have subjects fixating on a cross. 00:30:14.380 --> 00:30:17.410 And typically, in covert attention experiments, 00:30:17.410 --> 00:30:19.960 you want to make sure there aren't overt eye movements. 00:30:19.960 --> 00:30:21.460 And so you'll have an eye tracker to make sure 00:30:21.460 --> 00:30:23.470 the subject is keeping their eye on that cross. 00:30:23.470 --> 00:30:24.472 OK? 00:30:24.472 --> 00:30:25.930 And then you give them a little cue 00:30:25.930 --> 00:30:28.030 that says pay attention off to the right, 00:30:28.030 --> 00:30:30.700 but don't move your eyes, OK? 00:30:30.700 --> 00:30:33.730 And then shortly thereafter, a little cue comes up. 00:30:33.730 --> 00:30:35.230 And you have to hit a button quickly 00:30:35.230 --> 00:30:36.580 that you detected the target. 00:30:36.580 --> 00:30:36.850 OK? 00:30:36.850 --> 00:30:38.183 It comes out at variable delays. 00:30:38.183 --> 00:30:40.450 So you can't just hit the button. 00:30:40.450 --> 00:30:43.060 OK, if you do that, you find that the reaction 00:30:43.060 --> 00:30:45.760 time to detect that target, if it's where you're attending, 00:30:45.760 --> 00:30:48.860 is really fast, not much more than 200 milliseconds, 00:30:48.860 --> 00:30:51.520 which is damned fast, right? 00:30:51.520 --> 00:30:54.765 Now consider a case where you're instructed to attend over here. 00:30:54.765 --> 00:30:56.640 And the way you get these experiments to work 00:30:56.640 --> 00:30:59.167 is that these cues are valid 80% of the time. 00:30:59.167 --> 00:31:01.000 So there's a reason for subject to-- there's 00:31:01.000 --> 00:31:03.120 a motivation for them to follow your instruction. 00:31:03.120 --> 00:31:04.380 So they're trying to answer quickly. 00:31:04.380 --> 00:31:05.340 And there's like, OK, they're ready. 00:31:05.340 --> 00:31:06.690 It's almost certainly going to be over here. 00:31:06.690 --> 00:31:07.260 But oops. 00:31:07.260 --> 00:31:08.160 It's not. 00:31:08.160 --> 00:31:09.180 OK? 00:31:09.180 --> 00:31:12.600 Then reaction time is almost 100 milliseconds slower, 00:31:12.600 --> 00:31:16.350 which is a huge effect in psychology, 100 milliseconds. 00:31:16.350 --> 00:31:17.310 OK? 00:31:17.310 --> 00:31:20.880 OK, so you're much slower to detect something 00:31:20.880 --> 00:31:23.320 if it's at an unattended location. 00:31:23.320 --> 00:31:23.820 OK? 00:31:23.820 --> 00:31:26.910 And if you have a neutral trial, you're somewhere in the middle. 00:31:26.910 --> 00:31:33.120 OK, so that is exogenous or voluntary attention. 00:31:33.120 --> 00:31:35.340 OK, and again, this is covert attention. 00:31:35.340 --> 00:31:37.410 No eye movements. 00:31:37.410 --> 00:31:41.460 All right, so third distinction, the example 00:31:41.460 --> 00:31:43.230 I just gave you was spatial attention. 00:31:43.230 --> 00:31:46.140 You're attending to this location or that location 00:31:46.140 --> 00:31:47.410 in space. 00:31:47.410 --> 00:31:47.910 OK? 00:31:47.910 --> 00:31:50.340 That's probably the most powerful and common kind 00:31:50.340 --> 00:31:52.432 of attention is usually the things 00:31:52.432 --> 00:31:54.390 you're interested in are in a particular place. 00:31:54.390 --> 00:31:55.598 And you attend to that place. 00:31:55.598 --> 00:31:57.360 And there you go. 00:31:57.360 --> 00:31:59.130 But it's not the only kind. 00:31:59.130 --> 00:32:01.360 You can have feature-based attention. 00:32:01.360 --> 00:32:04.680 So if your utensil drawer is a hell of a mess like mine 00:32:04.680 --> 00:32:09.540 is, like this, if your task is to find the black vegetable 00:32:09.540 --> 00:32:12.030 peeler, best of luck to you. 00:32:12.030 --> 00:32:13.710 It'll take quite a while. 00:32:13.710 --> 00:32:14.380 It's in there. 00:32:14.380 --> 00:32:15.088 It's right there. 00:32:15.088 --> 00:32:16.800 But it takes a while, right? 00:32:16.800 --> 00:32:21.660 In contrast, if the task is find the purple rubber spatula, duh, 00:32:21.660 --> 00:32:22.440 right? 00:32:22.440 --> 00:32:24.180 OK, so that's feature-based attention. 00:32:24.180 --> 00:32:25.950 You don't know the location in advance. 00:32:25.950 --> 00:32:28.283 You know something about the feature you're looking for, 00:32:28.283 --> 00:32:31.140 that it's black or that it's purple or round or square 00:32:31.140 --> 00:32:32.610 or whatever the feature is. 00:32:32.610 --> 00:32:35.070 OK, so different kinds of filters 00:32:35.070 --> 00:32:38.040 you can set on your attention system. 00:32:38.040 --> 00:32:39.810 OK, so that's just to give you some 00:32:39.810 --> 00:32:42.640 of the phenomenology of the different kinds of attention. 00:32:42.640 --> 00:32:44.245 How does all this work in the brain? 00:32:44.245 --> 00:32:45.870 I'm not going to tell you how it works. 00:32:45.870 --> 00:32:49.920 We'll just focus mostly on what the brain regions are. 00:32:49.920 --> 00:32:55.750 OK, so let's go back to this case here, voluntary attention. 00:32:55.750 --> 00:32:59.160 So now the question is, what happens when you get this cue? 00:32:59.160 --> 00:33:00.690 You're not going to move your eyes. 00:33:00.690 --> 00:33:03.900 But you're kind of cranking up that part of space. 00:33:03.900 --> 00:33:07.020 OK, what's going on in the brain right there 00:33:07.020 --> 00:33:09.150 before the stimulus comes on? 00:33:09.150 --> 00:33:10.860 Everybody get the question? 00:33:10.860 --> 00:33:12.900 OK, you can sort of feel it happening. 00:33:12.900 --> 00:33:14.830 But what does that mean? 00:33:14.830 --> 00:33:18.090 Well, this is very amenable to a simple functional MRI 00:33:18.090 --> 00:33:19.110 experiment. 00:33:19.110 --> 00:33:21.360 And in the early days of functional MRI, 00:33:21.360 --> 00:33:24.210 a whole bunch of people at once realize, oh, right, we 00:33:24.210 --> 00:33:26.190 can answer this longstanding question 00:33:26.190 --> 00:33:29.640 of whether early retinotopic parts of the visual system 00:33:29.640 --> 00:33:32.610 are affected just by a cue like that, 00:33:32.610 --> 00:33:36.150 even before the stimulus comes on, right? 00:33:36.150 --> 00:33:38.430 And I think it was 1998. 00:33:38.430 --> 00:33:40.980 A whole bunch of people started doing this in 1997. 00:33:40.980 --> 00:33:42.420 I was one of them. 00:33:42.420 --> 00:33:44.340 But a whole bunch did it once in 1998. 00:33:44.340 --> 00:33:46.647 I think like six papers were published 00:33:46.647 --> 00:33:48.480 all doing versions of this next thing, which 00:33:48.480 --> 00:33:51.150 is one of those obvious ideas. 00:33:51.150 --> 00:33:51.900 We got scooped. 00:33:51.900 --> 00:33:54.730 But anyway, everybody got the same result. 00:33:54.730 --> 00:33:57.070 So basically, if you just do a simple comparison-- 00:33:57.070 --> 00:33:58.320 this is the version they have. 00:33:58.320 --> 00:33:59.520 Subjects are fixating here. 00:33:59.520 --> 00:34:01.410 There's two stimuli. 00:34:01.410 --> 00:34:03.420 They're looking in V1 and V2. 00:34:03.420 --> 00:34:06.180 And if you just do a contrast of the case where you're 00:34:06.180 --> 00:34:08.639 looking here and you're attending, waiting for a target 00:34:08.639 --> 00:34:12.510 here versus waiting for a target there without moving your eyes, 00:34:12.510 --> 00:34:17.429 you get a big contralateral modulation in V1 and V2. 00:34:17.429 --> 00:34:19.750 This is a slice near the back of the head here. 00:34:19.750 --> 00:34:22.260 So this is a piece of calcarine sulcus 00:34:22.260 --> 00:34:24.929 or primary visual cortex, right? 00:34:24.929 --> 00:34:28.620 And so you can see, even before the target stimulus comes on, 00:34:28.620 --> 00:34:32.639 just attending over there gives you a big baseline increase 00:34:32.639 --> 00:34:33.570 in neural activity. 00:34:33.570 --> 00:34:35.580 Everybody clear what's going on here? 00:34:35.580 --> 00:34:37.480 And of course, you can do the opposite one 00:34:37.480 --> 00:34:40.409 and see that it shifts to the opposite side of space. 00:34:40.409 --> 00:34:41.750 OK? 00:34:41.750 --> 00:34:44.600 OK, so that's all before the stimulus comes on. 00:34:44.600 --> 00:34:47.360 You can think of it as priming the brain, kind of juicing up 00:34:47.360 --> 00:34:49.020 those neurons getting them ready to go, 00:34:49.020 --> 00:34:51.020 so that, when that stimulus comes through, boom. 00:34:51.020 --> 00:34:53.199 Your reaction time is faster. 00:34:53.199 --> 00:34:55.570 OK? 00:34:55.570 --> 00:34:59.920 OK, so that's modulating parts of visual cortex 00:34:59.920 --> 00:35:03.100 before a stimulus comes on to get it ready. 00:35:03.100 --> 00:35:05.020 But we can also look at, what is the effect 00:35:05.020 --> 00:35:07.000 on a stimulus once it comes through, 00:35:07.000 --> 00:35:09.665 an attended stimulus or an unattended stimulus? 00:35:09.665 --> 00:35:11.290 To show you that, I'm going to show you 00:35:11.290 --> 00:35:16.360 a kind of feature-based attention and an ancient-- this 00:35:16.360 --> 00:35:19.540 is a paper we published in 1998, I think. 00:35:19.540 --> 00:35:21.460 This is a nonspatial version. 00:35:21.460 --> 00:35:23.950 So we gave subjects-- guess what-- faces 00:35:23.950 --> 00:35:26.260 and houses and a little crosshair. 00:35:26.260 --> 00:35:28.750 And we had subjects in different blocks 00:35:28.750 --> 00:35:31.120 say whether the two arms of the cross 00:35:31.120 --> 00:35:34.330 were the same or different length, OK? 00:35:34.330 --> 00:35:35.855 So vertical one is different length. 00:35:35.855 --> 00:35:37.180 So that's a different case. 00:35:37.180 --> 00:35:40.420 Whether the two houses are same or different 00:35:40.420 --> 00:35:42.770 or whether the two faces are same or different. 00:35:42.770 --> 00:35:44.680 OK, so actually, it's spatial and feature, 00:35:44.680 --> 00:35:47.245 when you think of it, because they're in different places. 00:35:47.245 --> 00:35:48.100 OK? 00:35:48.100 --> 00:35:50.350 So we then looked in a bunch of regions. 00:35:50.350 --> 00:35:53.140 I'll show you the data from the fusiform face area. 00:35:53.140 --> 00:35:56.740 And the key thing about this is, in all three tasks, 00:35:56.740 --> 00:35:59.300 we had the identical stimuli. 00:35:59.300 --> 00:36:01.570 So there's always faces and houses 00:36:01.570 --> 00:36:04.330 and crosses in the same place in your visual field, 00:36:04.330 --> 00:36:05.830 in all of those blocks. 00:36:05.830 --> 00:36:07.690 It's just a matter of which of those things 00:36:07.690 --> 00:36:09.700 you're paying attention to. 00:36:09.700 --> 00:36:10.605 OK? 00:36:10.605 --> 00:36:12.730 So what do you think we'll see in the fusiform face 00:36:12.730 --> 00:36:16.240 area in this experiment? 00:36:16.240 --> 00:36:20.170 Is it going to care whether you're attending to faces 00:36:20.170 --> 00:36:23.590 or attending to houses or attending to the crosshair? 00:36:23.590 --> 00:36:25.195 Same stimulus all the time. 00:36:29.840 --> 00:36:31.200 Yeah, Jimmy? 00:36:31.200 --> 00:36:33.200 AUDIENCE: [INAUDIBLE] when you're not attending. 00:36:33.200 --> 00:36:36.040 But when you're attending, [INAUDIBLE] 00:36:36.040 --> 00:36:37.863 NANCY KANWISHER: Exactly what happens. 00:36:37.863 --> 00:36:39.280 OK, everybody hear the prediction? 00:36:39.280 --> 00:36:40.780 You'll still get something. 00:36:40.780 --> 00:36:43.840 But you'll get more when you're paying attention to it. 00:36:43.840 --> 00:36:47.690 OK, so here's the FFA response over time. 00:36:47.690 --> 00:36:49.120 Here's the time course. 00:36:49.120 --> 00:36:51.400 And these gray blocks are the blocks. 00:36:51.400 --> 00:36:53.560 These are the different attending to houses, faces, 00:36:53.560 --> 00:36:57.370 color, houses, faces, crosshair, houses, faces, crosshair. 00:36:57.370 --> 00:36:59.320 The gray bars are when the subjects 00:36:59.320 --> 00:37:02.170 are attending to faces. 00:37:02.170 --> 00:37:09.020 Now, here, I actually can't quite tell. 00:37:09.020 --> 00:37:10.480 Yeah, I can sort of tell. 00:37:10.480 --> 00:37:11.830 You can't see it on the screen. 00:37:11.830 --> 00:37:14.218 But there are little rest periods between those blocks. 00:37:14.218 --> 00:37:15.760 So I'm trying to figure out if you're 00:37:15.760 --> 00:37:19.630 right that there's some response greater than baseline. 00:37:19.630 --> 00:37:21.970 I think there's actually very little selective response 00:37:21.970 --> 00:37:23.290 greater than baseline. 00:37:23.290 --> 00:37:26.500 By design, we made this a whopping attentional 00:37:26.500 --> 00:37:29.943 manipulation, so that all of the tasks are really difficult. 00:37:29.943 --> 00:37:31.360 And when you're doing one of them, 00:37:31.360 --> 00:37:33.680 you just barely feel aware of anything else. 00:37:33.680 --> 00:37:36.100 In fact, I vividly remember the first time 00:37:36.100 --> 00:37:38.710 we ran this experiment, I was a subject in the scanner. 00:37:38.710 --> 00:37:40.720 And I did the first block. 00:37:40.720 --> 00:37:43.900 And I was doing just crosshairs. 00:37:43.900 --> 00:37:46.437 And I went through the whole crosshair thing. 00:37:46.437 --> 00:37:48.770 And it wasn't till the end of the experiment I realized, 00:37:48.770 --> 00:37:50.187 oh, right, there were faces there. 00:37:50.187 --> 00:37:51.860 I was just completely unaware of them. 00:37:51.860 --> 00:37:56.770 So we designed it to really so tie up your mental capacity 00:37:56.770 --> 00:37:59.230 that you just didn't have processing resources left 00:37:59.230 --> 00:38:00.200 for anything else. 00:38:00.200 --> 00:38:02.980 And so if there is a response to everything else here, 00:38:02.980 --> 00:38:03.890 it's really low. 00:38:03.890 --> 00:38:06.670 But you can see, certainly, the attended thing is much more. 00:38:06.670 --> 00:38:08.360 It's much stronger in the attended case 00:38:08.360 --> 00:38:09.880 than the unattended case. 00:38:09.880 --> 00:38:10.720 OK? 00:38:10.720 --> 00:38:12.400 So this is a general property. 00:38:12.400 --> 00:38:14.440 Like basically, all of the perceptual regions 00:38:14.440 --> 00:38:18.490 we've talked about are strongly modulable by attention, 00:38:18.490 --> 00:38:23.320 OK, from retinotopic regions on up. 00:38:23.320 --> 00:38:29.300 OK, including V1 and, in fact, even including the lateral 00:38:29.300 --> 00:38:31.680 geniculate nucleus. 00:38:31.680 --> 00:38:34.520 So one synapse up from the retina, 00:38:34.520 --> 00:38:38.390 you're already modulating activity there by attention. 00:38:38.390 --> 00:38:40.880 OK? 00:38:40.880 --> 00:38:43.670 I know I said this, but it maybe went by briefly. 00:38:43.670 --> 00:38:45.950 You have 10 times as many connections down 00:38:45.950 --> 00:38:50.190 from cortex down to the LGN as you have going forward. 00:38:50.190 --> 00:38:50.690 OK? 00:38:50.690 --> 00:38:52.790 One of the things they're doing is setting up 00:38:52.790 --> 00:38:56.660 selective filters, so that only the stuff you want to process 00:38:56.660 --> 00:38:59.250 makes it to higher stages. 00:38:59.250 --> 00:39:01.312 OK, Yes? 00:39:01.312 --> 00:39:03.020 AUDIENCE: So does this sort of phenomenon 00:39:03.020 --> 00:39:05.230 generalize across the brain areas? 00:39:05.230 --> 00:39:06.170 I mean, it's like-- 00:39:06.170 --> 00:39:08.295 NANCY KANWISHER: It's generally true of pretty much 00:39:08.295 --> 00:39:09.485 everywhere, yeah. 00:39:09.485 --> 00:39:11.280 AUDIENCE: It might be the intuitive physics 00:39:11.280 --> 00:39:12.580 thing is justified. 00:39:12.580 --> 00:39:15.608 So it's better to see the same stimulus. 00:39:15.608 --> 00:39:16.650 NANCY KANWISHER: Exactly. 00:39:16.650 --> 00:39:18.810 It's an instance of this, exactly right. 00:39:18.810 --> 00:39:19.560 Exactly right. 00:39:19.560 --> 00:39:22.110 It gives us one of our paradigms. 00:39:22.110 --> 00:39:24.660 In functional MRI studies, have the same stimulus, 00:39:24.660 --> 00:39:26.050 vary the task. 00:39:26.050 --> 00:39:27.128 OK? 00:39:27.128 --> 00:39:28.920 Some things don't work as well, things that 00:39:28.920 --> 00:39:31.030 are just very dominant stimuli. 00:39:31.030 --> 00:39:33.900 In this experiment, if we hadn't put the faces in the periphery 00:39:33.900 --> 00:39:36.900 and given subjects a damn difficult task, 00:39:36.900 --> 00:39:38.400 the modulation wouldn't have worked. 00:39:38.400 --> 00:39:39.900 Because faces are just so dominant, 00:39:39.900 --> 00:39:42.990 they're going to punch through even if you don't want to, OK? 00:39:42.990 --> 00:39:44.597 Like web pop ups. You also-- 00:39:44.597 --> 00:39:46.680 I'm going to skip this because we won't have time. 00:39:46.680 --> 00:39:48.180 You could get very similar things 00:39:48.180 --> 00:39:51.000 in primary auditory cortex listening to high frequencies 00:39:51.000 --> 00:39:52.140 or low frequencies. 00:39:52.140 --> 00:39:53.800 These are all the same stimuli. 00:39:53.800 --> 00:39:56.860 This is voxel selected for low frequencies, voxel 00:39:56.860 --> 00:39:58.110 selected for high frequencies. 00:39:58.110 --> 00:39:59.940 You have a high frequency input in one ear, 00:39:59.940 --> 00:40:01.080 low frequency in the other. 00:40:01.080 --> 00:40:05.210 As you switch between, those responses toggle. 00:40:05.210 --> 00:40:08.390 OK, so all of that tells you the effects of attention, 00:40:08.390 --> 00:40:11.010 how it modulates activity all over the brain. 00:40:11.010 --> 00:40:14.510 But what is the source of attention signals in the brain? 00:40:14.510 --> 00:40:16.370 And that source is a set of regions 00:40:16.370 --> 00:40:19.130 we have encountered before, sometimes called 00:40:19.130 --> 00:40:21.050 the frontal-parietal attention network, 00:40:21.050 --> 00:40:23.180 these blue and green bits up in here, 00:40:23.180 --> 00:40:26.840 back here in the parietal lobe, up here in the frontal lobe. 00:40:26.840 --> 00:40:29.360 And they are active when you shift attention 00:40:29.360 --> 00:40:32.420 from one location to another, from one feature to another, 00:40:32.420 --> 00:40:36.260 or when you do any difficult attention-demanding task. 00:40:36.260 --> 00:40:38.660 We've also talked about them in the other context 00:40:38.660 --> 00:40:40.070 of the multiple demand system. 00:40:40.070 --> 00:40:42.410 It's pretty much the same set of cortical regions. 00:40:42.410 --> 00:40:44.840 That pretty much any time you do a difficult task, 00:40:44.840 --> 00:40:48.240 almost no matter what the task is, these regions turn on. 00:40:48.240 --> 00:40:50.360 So they're not just about visual attention. 00:40:50.360 --> 00:40:54.890 They're kind of about basically controlling your mind, right, 00:40:54.890 --> 00:40:59.810 selecting information, making yourself do difficult things. 00:40:59.810 --> 00:41:01.910 Who knows what that is computationally. 00:41:01.910 --> 00:41:05.330 But these regions are very systematically engaged. 00:41:05.330 --> 00:41:07.550 And they're particularly systematically engaged 00:41:07.550 --> 00:41:10.970 when you're shifting attention over different locations. 00:41:10.970 --> 00:41:13.280 OK, so just to remind you in contrast, everything else 00:41:13.280 --> 00:41:16.610 we've talked about, face areas, music areas, language areas, 00:41:16.610 --> 00:41:18.980 they're very specific for one mental process, 00:41:18.980 --> 00:41:19.940 domain specific. 00:41:19.940 --> 00:41:21.000 These are the opposite. 00:41:21.000 --> 00:41:23.690 They're ludicrously domain general. 00:41:23.690 --> 00:41:25.280 OK? 00:41:25.280 --> 00:41:28.580 All right, I'm going to skip the video. 00:41:28.580 --> 00:41:30.500 When the system is damaged bilaterally, 00:41:30.500 --> 00:41:33.360 all kinds of weird stuff happens. 00:41:33.360 --> 00:41:33.860 OK? 00:41:33.860 --> 00:41:34.580 I'll post this. 00:41:34.580 --> 00:41:36.500 If you guys send me an email to remind me, 00:41:36.500 --> 00:41:37.610 I'll post this clip in. 00:41:37.610 --> 00:41:40.550 Balint's syndrome, where you have bilateral damage 00:41:40.550 --> 00:41:42.440 back there in these parietal regions, 00:41:42.440 --> 00:41:45.390 people can only see one object at a time. 00:41:45.390 --> 00:41:45.890 OK? 00:41:45.890 --> 00:41:48.230 They're looking at a complicated thing like this. 00:41:48.230 --> 00:41:50.450 And they would see, I see Shosh. 00:41:50.450 --> 00:41:51.320 See anything else? 00:41:51.320 --> 00:41:52.520 No just Shosh. 00:41:52.520 --> 00:41:53.390 Nothing else there? 00:41:53.390 --> 00:41:53.890 No. 00:41:53.890 --> 00:41:54.680 Just Shosh, right? 00:41:54.680 --> 00:41:55.340 Totally weird. 00:41:55.340 --> 00:41:57.170 Anyway, so they get locked on one thing. 00:41:57.170 --> 00:41:59.030 They can't shift attention. 00:41:59.030 --> 00:42:01.550 OK. 00:42:01.550 --> 00:42:05.220 OK, I want to talk at least briefly about awareness. 00:42:05.220 --> 00:42:09.780 So let's talk a little bit about neural correlates of awareness. 00:42:09.780 --> 00:42:13.220 And so first question is, if we want 00:42:13.220 --> 00:42:17.990 to study perceptual awareness and not just perception, 00:42:17.990 --> 00:42:20.570 how are we going to uncouple those things? 00:42:20.570 --> 00:42:23.720 We've sort of talked about a few examples with attention. 00:42:23.720 --> 00:42:25.940 With attention, the thing you're attending to 00:42:25.940 --> 00:42:28.220 is at least much more dominant in your awareness 00:42:28.220 --> 00:42:30.080 than the stuff you're not attending to, 00:42:30.080 --> 00:42:33.300 even if the other stuff seeps in a little bit. 00:42:33.300 --> 00:42:39.470 So that's one way, where you have the identical stimulus. 00:42:39.470 --> 00:42:42.140 But you were varying the degree of awareness. 00:42:42.140 --> 00:42:45.737 But another way-- oh, I need you guys to pass out the glasses. 00:42:45.737 --> 00:42:47.570 You want to both do that at different sides? 00:42:47.570 --> 00:42:49.517 OK, so I'm going to show you a stimulus. 00:42:49.517 --> 00:42:51.350 These guys are going to pass around glasses. 00:42:51.350 --> 00:42:52.940 And let me say in advance, I want them back. 00:42:52.940 --> 00:42:53.900 I use these every year. 00:42:53.900 --> 00:42:55.822 So drop them off here when you leave. 00:42:55.822 --> 00:42:58.280 OK, so what you're going to do, you put them on either way. 00:42:58.280 --> 00:42:59.750 Doesn't matter. 00:42:59.750 --> 00:43:01.700 OK, so first, we're going to do optics. 00:43:01.700 --> 00:43:03.260 Nothing interesting. 00:43:03.260 --> 00:43:07.430 So look at this stimulus and close one eye. 00:43:07.430 --> 00:43:09.410 OK, now look at it through the glasses. 00:43:09.410 --> 00:43:11.690 Look at it through the glasses, and close one eye. 00:43:11.690 --> 00:43:14.630 And you should see just a face or just a house. 00:43:14.630 --> 00:43:17.400 And if you close the other eye, you should see the opposite. 00:43:17.400 --> 00:43:18.680 Does everybody get that? 00:43:18.680 --> 00:43:19.910 OK, that's not psychology. 00:43:19.910 --> 00:43:20.750 That's optics. 00:43:20.750 --> 00:43:22.730 The glasses are just filtering one image 00:43:22.730 --> 00:43:26.385 into one eye and another image into the other eye, OK? 00:43:26.385 --> 00:43:28.760 This is all this is is a way to get different information 00:43:28.760 --> 00:43:30.110 to your two eyes. 00:43:30.110 --> 00:43:32.690 OK, now just look with both eyes. 00:43:32.690 --> 00:43:33.890 And don't do anything. 00:43:33.890 --> 00:43:35.270 Just kind of look. 00:43:35.270 --> 00:43:39.360 And if anything cool happens, you can kind of go, ooh, aah. 00:43:43.480 --> 00:43:45.160 Or you can tell me what's happening. 00:43:45.160 --> 00:43:45.910 Just watch. 00:43:45.910 --> 00:43:47.500 Doesn't always happen immediately. 00:43:47.500 --> 00:43:49.774 Yeah, Kwylie, what's happening? 00:43:49.774 --> 00:43:51.160 AUDIENCE: [INAUDIBLE] 00:43:51.160 --> 00:43:51.490 NANCY KANWISHER: Sorry. 00:43:51.490 --> 00:43:51.990 What's that? 00:43:51.990 --> 00:43:54.370 AUDIENCE: Every time I blink, it changes from the house 00:43:54.370 --> 00:43:54.870 to the face. 00:43:54.870 --> 00:43:55.920 NANCY KANWISHER: Aha. 00:43:55.920 --> 00:43:58.650 OK, it changes from the house to the face only when you blink. 00:43:58.650 --> 00:43:59.265 Yeah, Kwylie? 00:43:59.265 --> 00:44:01.140 AUDIENCE: So at first when I first put it on, 00:44:01.140 --> 00:44:05.010 I was like I saw the house and the face superimposed. 00:44:05.010 --> 00:44:06.690 And then you told us put one eye. 00:44:06.690 --> 00:44:09.945 And then I opened both eyes, and it went from the house 00:44:09.945 --> 00:44:11.090 to the face. 00:44:11.090 --> 00:44:12.090 NANCY KANWISHER: Uh huh. 00:44:12.090 --> 00:44:12.660 Uh huh. 00:44:12.660 --> 00:44:13.785 And then did it stay there? 00:44:13.785 --> 00:44:16.080 Or does it keep flipping? 00:44:16.080 --> 00:44:18.240 OK, if this is not working for you, don't panic. 00:44:18.240 --> 00:44:19.532 There's nothing wrong with you. 00:44:19.532 --> 00:44:22.570 It's hard to get everybody's red-green balance the same. 00:44:22.570 --> 00:44:23.070 Yeah. 00:44:23.070 --> 00:44:23.370 Sorry. 00:44:23.370 --> 00:44:24.040 Question? 00:44:24.040 --> 00:44:24.740 Shardul, yeah? 00:44:24.740 --> 00:44:27.390 AUDIENCE: [INAUDIBLE] 00:44:27.390 --> 00:44:29.550 NANCY KANWISHER: So I share your intuition. 00:44:29.550 --> 00:44:30.870 I think I can choose too. 00:44:30.870 --> 00:44:33.040 But there's actually a whole literature on that. 00:44:33.040 --> 00:44:35.760 And the guy I was collaborating with on this project, 00:44:35.760 --> 00:44:38.220 20 years ago, insists that, actually, that's 00:44:38.220 --> 00:44:39.070 a wrong intuition. 00:44:39.070 --> 00:44:39.780 You can't choose. 00:44:39.780 --> 00:44:40.890 And I said, oh, the hell. 00:44:40.890 --> 00:44:42.290 The hell I can't. 00:44:42.290 --> 00:44:44.040 I'm in the scanner being your best subject 00:44:44.040 --> 00:44:45.810 ever because I'm switching exactly when you 00:44:45.810 --> 00:44:46.440 want me to switch. 00:44:46.440 --> 00:44:47.400 Don't tell me I can't switch. 00:44:47.400 --> 00:44:48.840 He said, no, the literature says you don't. 00:44:48.840 --> 00:44:50.760 Anyway, I don't know the latest on that. 00:44:50.760 --> 00:44:51.530 Yeah? 00:44:51.530 --> 00:44:54.630 AUDIENCE: Kind of related, it feels a lot harder 00:44:54.630 --> 00:44:55.993 to see the house than the face. 00:44:55.993 --> 00:44:56.910 NANCY KANWISHER: Yeah. 00:44:56.910 --> 00:44:58.970 AUDIENCE: I can see the face a lot easier than switching. 00:44:58.970 --> 00:44:59.845 NANCY KANWISHER: Yes. 00:44:59.845 --> 00:45:03.150 It's not optimally set up, so that it's perfect for each. 00:45:03.150 --> 00:45:05.880 Really the reason I do this is to amuse myself looking 00:45:05.880 --> 00:45:09.030 at all of you with your-- 00:45:09.030 --> 00:45:10.680 thank you. 00:45:10.680 --> 00:45:12.262 OK, so you can keep looking or not, 00:45:12.262 --> 00:45:14.220 but I'm going to tell you what's going on here. 00:45:14.220 --> 00:45:16.290 The cool thing about this is when-- 00:45:16.290 --> 00:45:18.230 if it didn't switch for you, the person-- 00:45:18.230 --> 00:45:21.460 is there anybody for whom it didn't switch? 00:45:21.460 --> 00:45:21.960 One. 00:45:21.960 --> 00:45:25.150 OK, so maybe your color vision or who knows what. 00:45:25.150 --> 00:45:26.640 But anyway. 00:45:26.640 --> 00:45:29.610 OK, if it doesn't switch, there's nothing wrong with you. 00:45:29.610 --> 00:45:33.090 The percept everyone else has is it just flips every few seconds 00:45:33.090 --> 00:45:34.140 from one to the other. 00:45:34.140 --> 00:45:34.980 OK. 00:45:34.980 --> 00:45:38.130 So what's cool about this is, when it switches, 00:45:38.130 --> 00:45:40.350 nothing changes on your retina. 00:45:40.350 --> 00:45:42.630 Only your state of awareness changes. 00:45:42.630 --> 00:45:45.240 And that gives us a wonderful lever 00:45:45.240 --> 00:45:48.750 to study what goes on in the brain when awareness switches, 00:45:48.750 --> 00:45:51.690 unconfounded from the stimulus. 00:45:51.690 --> 00:45:52.680 OK? 00:45:52.680 --> 00:45:55.470 It's like varying attention, but it's more powerful. 00:45:55.470 --> 00:45:58.800 So of course, we put people in the scanner. 00:45:58.800 --> 00:46:00.610 We put mostly me and a few others. 00:46:00.610 --> 00:46:01.170 But anyway. 00:46:01.170 --> 00:46:03.030 We popped ourselves in the scanner. 00:46:03.030 --> 00:46:05.010 We just taped these things on our forehead, 00:46:05.010 --> 00:46:06.090 nice low-tech experiment. 00:46:06.090 --> 00:46:07.980 And we looked at that exact stimulus. 00:46:07.980 --> 00:46:09.030 OK? 00:46:09.030 --> 00:46:11.670 And we scanned the brain while people 00:46:11.670 --> 00:46:15.300 sat there watching the stimulus flip back and forth. 00:46:15.300 --> 00:46:15.960 OK? 00:46:15.960 --> 00:46:18.630 So this is a stimulus for the whole experiment. 00:46:18.630 --> 00:46:19.740 This is the percept. 00:46:19.740 --> 00:46:21.132 It switches back and forth. 00:46:21.132 --> 00:46:23.340 The subject has a little button box, so they can say, 00:46:23.340 --> 00:46:24.330 now I see the face. 00:46:24.330 --> 00:46:25.930 Now I see the house. 00:46:25.930 --> 00:46:27.930 Now, of course, the choice of a face and a house 00:46:27.930 --> 00:46:29.520 was not random. 00:46:29.520 --> 00:46:31.470 Why did we choose a face and a house? 00:46:31.470 --> 00:46:33.150 So that we could look at the response 00:46:33.150 --> 00:46:35.250 in the FFA and the PPA. 00:46:35.250 --> 00:46:37.080 FFA loves faces, hates houses. 00:46:37.080 --> 00:46:38.820 PPA loves houses, hates faces. 00:46:38.820 --> 00:46:40.020 Perfect. 00:46:40.020 --> 00:46:40.950 Right? 00:46:40.950 --> 00:46:42.540 So the question is, are they going 00:46:42.540 --> 00:46:45.450 to switch when your percept switches, even though nothing's 00:46:45.450 --> 00:46:47.040 changing on your retina? 00:46:47.040 --> 00:46:48.660 What do you guys think? 00:46:48.660 --> 00:46:49.480 Switch? 00:46:49.480 --> 00:46:49.980 Switch? 00:46:49.980 --> 00:46:52.140 How many people think it's going to switch? 00:46:52.140 --> 00:46:54.430 How many people think it's not going to switch? 00:46:54.430 --> 00:46:55.300 A few. 00:46:55.300 --> 00:46:58.420 OK, all right, so that's what we did. 00:46:58.420 --> 00:47:01.990 Here is now the raw MRI time course averaged over the FFA 00:47:01.990 --> 00:47:05.800 and averaged over the PPA for one five-minute experiment 00:47:05.800 --> 00:47:07.630 or three-minute experiment in one subject. 00:47:07.630 --> 00:47:08.170 Probably me. 00:47:08.170 --> 00:47:09.520 I forget. 00:47:09.520 --> 00:47:11.380 Again, stimulus is the same the whole time. 00:47:11.380 --> 00:47:15.340 The letters are the times when the subject pressed the button. 00:47:15.340 --> 00:47:17.320 And you can sort of get a sense that there's 00:47:17.320 --> 00:47:20.770 a little bit of maybe like here's a phase the FFA 00:47:20.770 --> 00:47:21.940 response goes up. 00:47:21.940 --> 00:47:24.430 Here again the house goes up. 00:47:24.430 --> 00:47:26.140 But it's kind of hard to tell. 00:47:26.140 --> 00:47:28.420 So really, the way to analyze these data 00:47:28.420 --> 00:47:33.250 is to take all the face to house flips, right, 00:47:33.250 --> 00:47:36.770 and align them and signal average to get rid of noise. 00:47:36.770 --> 00:47:37.270 OK? 00:47:37.270 --> 00:47:41.710 So we can look at, what happens before and after a switch 00:47:41.710 --> 00:47:42.910 from face to house? 00:47:42.910 --> 00:47:45.100 And what happens in the opposite direction switch? 00:47:45.100 --> 00:47:46.580 Everybody get the idea? 00:47:46.580 --> 00:47:49.090 It's just a way to clean up the noise here. 00:47:49.090 --> 00:47:50.410 And here's what happens. 00:47:50.410 --> 00:47:51.500 This is time zero. 00:47:51.500 --> 00:47:53.680 The subject presses a button saying 00:47:53.680 --> 00:47:57.280 that their percept has flipped between a house to a face. 00:47:57.280 --> 00:47:59.620 The response in the FFA shoots up. 00:47:59.620 --> 00:48:03.355 And the response in the PPA shoots down. 00:48:03.355 --> 00:48:05.430 Isn't that cool? 00:48:05.430 --> 00:48:10.860 OK, now why are these peaks and valleys after the button press? 00:48:14.280 --> 00:48:14.780 Yeah. 00:48:14.780 --> 00:48:15.320 Evan, right. 00:48:15.320 --> 00:48:17.450 There's a delayed signal, right? 00:48:17.450 --> 00:48:19.640 OK? 00:48:19.640 --> 00:48:20.630 This is harder. 00:48:20.630 --> 00:48:22.880 Why do they come back together out there? 00:48:27.060 --> 00:48:28.830 Yeah, because it flips back. 00:48:28.830 --> 00:48:30.300 It flips back. 00:48:30.300 --> 00:48:33.270 And all we've done is signal average to one button press. 00:48:33.270 --> 00:48:35.320 But there are different durations of percepts. 00:48:35.320 --> 00:48:36.900 Sometimes it lasts three seconds. 00:48:36.900 --> 00:48:39.480 Sometimes it lasts 10 seconds, everything in between. 00:48:39.480 --> 00:48:41.250 By the time you're 12 seconds out, 00:48:41.250 --> 00:48:42.750 most people have flipped again. 00:48:42.750 --> 00:48:44.550 That's why it goes back. 00:48:44.550 --> 00:48:45.435 OK, make sense? 00:48:48.420 --> 00:48:49.237 Yeah? 00:48:49.237 --> 00:49:05.040 AUDIENCE: [INAUDIBLE] 00:49:05.040 --> 00:49:06.290 NANCY KANWISHER: I don't know. 00:49:06.290 --> 00:49:09.050 And I'm not sure that that was generally true. 00:49:09.050 --> 00:49:10.670 I hadn't noticed that before. 00:49:10.670 --> 00:49:12.830 But we should scrutinize the images. 00:49:12.830 --> 00:49:16.040 I can't actually remember if this was averaged over subjects 00:49:16.040 --> 00:49:17.150 or if this is one subject. 00:49:17.150 --> 00:49:18.530 I suspect that's a fluke. 00:49:18.530 --> 00:49:21.640 But we could look at it and see. 00:49:21.640 --> 00:49:26.310 OK, so the point of all of this is that these regions, the face 00:49:26.310 --> 00:49:28.590 area and the place area, care about what you 00:49:28.590 --> 00:49:31.290 are experiencing, unconfounded from what's 00:49:31.290 --> 00:49:33.120 hitting your retina, right? 00:49:33.120 --> 00:49:35.620 They are reflecting the contents of your awareness, 00:49:35.620 --> 00:49:41.370 not just what's coming into your eyes, which is cool. 00:49:41.370 --> 00:49:45.430 OK, so that shows that these regions kind 00:49:45.430 --> 00:49:47.710 of track awareness. 00:49:47.710 --> 00:49:48.670 OK? 00:49:48.670 --> 00:49:52.330 But can we find any evidence for perception 00:49:52.330 --> 00:49:55.630 without awareness using neuroimaging? 00:49:55.630 --> 00:49:56.560 OK? 00:49:56.560 --> 00:49:59.230 So to make this point, I'm going to accelerate slightly, 00:49:59.230 --> 00:50:00.968 but I think there's just barely time. 00:50:00.968 --> 00:50:03.010 There are lots and lots of studies of this genre. 00:50:03.010 --> 00:50:04.750 And I'll tell you about one. 00:50:04.750 --> 00:50:05.800 So I'm going to show you. 00:50:05.800 --> 00:50:08.110 I'm going to flash up a very rapid series of digits. 00:50:08.110 --> 00:50:10.600 You have to get ready to write stuff down. 00:50:10.600 --> 00:50:15.610 Your task is to see if there are any letters in the digit. 00:50:15.610 --> 00:50:16.480 There might be zero. 00:50:16.480 --> 00:50:17.200 There might be one. 00:50:17.200 --> 00:50:17.920 There might be a few. 00:50:17.920 --> 00:50:19.330 Write down any letters you see. 00:50:19.330 --> 00:50:20.960 It's going to go by really fast. 00:50:20.960 --> 00:50:23.500 OK, everyone ready? 00:50:23.500 --> 00:50:25.930 OK. 00:50:25.930 --> 00:50:26.500 Here we go. 00:50:30.080 --> 00:50:33.320 OK, write down any letters you may have seen. 00:50:33.320 --> 00:50:35.180 OK? 00:50:35.180 --> 00:50:37.640 All right, let's do another one. 00:50:37.640 --> 00:50:38.390 Everyone ready? 00:50:43.630 --> 00:50:47.140 OK, write down any letters you may have seen. 00:50:47.140 --> 00:50:48.480 OK? 00:50:48.480 --> 00:50:52.560 OK, raise your hand if you saw both the A and the P 00:50:52.560 --> 00:50:55.030 in the first sequence. 00:50:55.030 --> 00:50:55.630 A few of you. 00:50:55.630 --> 00:50:57.130 Less than half. 00:50:57.130 --> 00:51:00.100 Raise your hand if you saw both the X and the H in the second. 00:51:00.100 --> 00:51:01.600 Almost everyone. 00:51:01.600 --> 00:51:03.670 All right, well, I cheated slightly. 00:51:03.670 --> 00:51:05.650 But never mind how I cheated. 00:51:05.650 --> 00:51:07.150 The way you cheat in demos-- 00:51:07.150 --> 00:51:08.950 you guys will be teaching someday. 00:51:08.950 --> 00:51:11.630 You have the one you want people to get wrong first. 00:51:11.630 --> 00:51:12.610 It's a total cheat. 00:51:12.610 --> 00:51:13.660 So it's slightly cheated. 00:51:13.660 --> 00:51:15.718 But if you do it right-- 00:51:15.718 --> 00:51:16.760 it didn't work last year. 00:51:16.760 --> 00:51:17.635 That's why I cheated. 00:51:17.635 --> 00:51:19.510 Anyway, even if you do it right in the lab, 00:51:19.510 --> 00:51:22.540 you get a really strong effect. 00:51:22.540 --> 00:51:24.910 There was only one digit between the A 00:51:24.910 --> 00:51:26.950 and the P in the first sequence. 00:51:26.950 --> 00:51:29.620 And it's like your brain is still dealing with the A 00:51:29.620 --> 00:51:30.983 when the P comes along. 00:51:30.983 --> 00:51:33.400 You just don't even see the P. You're looking for letters. 00:51:33.400 --> 00:51:34.750 You don't see it. 00:51:34.750 --> 00:51:36.910 Whereas there were three digits between the X 00:51:36.910 --> 00:51:39.370 and the H in the second sequence. 00:51:39.370 --> 00:51:41.930 And just to show you some real data. 00:51:41.930 --> 00:51:44.030 So this has been done lots of different ways. 00:51:44.030 --> 00:51:46.090 Here's an example of this experiment. 00:51:46.090 --> 00:51:50.738 And this is the time that people get the second letter when they 00:51:50.738 --> 00:51:52.030 don't have to report the first. 00:51:52.030 --> 00:51:53.350 Well, the first one's colored, right? 00:51:53.350 --> 00:51:55.480 So you either have to report the colored letter 00:51:55.480 --> 00:51:57.430 and detect the letter after it or just 00:51:57.430 --> 00:51:59.990 detect the letter after the colored thing. 00:51:59.990 --> 00:52:02.120 So if you don't have to report the first one, 00:52:02.120 --> 00:52:03.530 there's no dip in accuracy. 00:52:03.530 --> 00:52:04.030 Oh, sorry. 00:52:04.030 --> 00:52:06.340 This is a function of the distance between the two 00:52:06.340 --> 00:52:08.000 items in the sequence. 00:52:08.000 --> 00:52:10.570 But if you do, there's a big dip. 00:52:10.570 --> 00:52:13.810 That's maximal with one intervening item. 00:52:13.810 --> 00:52:15.470 Yeah? 00:52:15.470 --> 00:52:19.970 OK, well, here it says two or three. 00:52:19.970 --> 00:52:22.370 But anyway. 00:52:22.370 --> 00:52:24.525 OK, so that's called the attentional blink. 00:52:24.525 --> 00:52:26.900 And the idea is there isn't a physical blink of the eyes. 00:52:26.900 --> 00:52:28.793 But your attention system is tied up 00:52:28.793 --> 00:52:29.960 processing the first target. 00:52:29.960 --> 00:52:32.300 And it doesn't get the second one, OK? 00:52:32.300 --> 00:52:34.332 So there are dozens, probably hundreds 00:52:34.332 --> 00:52:35.540 of papers on this phenomenon. 00:52:35.540 --> 00:52:37.190 It's pretty cool. 00:52:37.190 --> 00:52:41.450 But for present purposes, we're going to use it to say, 00:52:41.450 --> 00:52:45.170 does that unseen second target get into the brain? 00:52:45.170 --> 00:52:46.610 Presumably, it lands on the retina 00:52:46.610 --> 00:52:47.808 because you didn't blink. 00:52:47.808 --> 00:52:49.100 So it could probably get there. 00:52:49.100 --> 00:52:50.210 Probably got to V1. 00:52:50.210 --> 00:52:53.930 How far up the system did it get? 00:52:53.930 --> 00:52:58.130 Can you think of how we might test this using functional MRI. 00:52:58.130 --> 00:53:02.090 How would we see how far those stimuli 00:53:02.090 --> 00:53:03.890 go in an experiment like this? 00:53:07.750 --> 00:53:08.500 What would we use? 00:53:08.500 --> 00:53:11.770 What would we measure the MRI response to? 00:53:11.770 --> 00:53:13.427 How could we design a version of this 00:53:13.427 --> 00:53:15.010 that you could do with functional MRI? 00:53:19.690 --> 00:53:24.040 We need some MRI response, where, if we get that response, 00:53:24.040 --> 00:53:26.455 we know that it's a response to a given stimulus. 00:53:29.560 --> 00:53:31.990 What would we measure? 00:53:31.990 --> 00:53:33.250 And what stimuli would we use? 00:53:35.830 --> 00:53:37.953 AUDIENCE: Well, we could use faces or something. 00:53:37.953 --> 00:53:38.870 NANCY KANWISHER: Yeah. 00:53:38.870 --> 00:53:39.920 It's always the same. 00:53:39.920 --> 00:53:40.460 Yeah. 00:53:40.460 --> 00:53:41.930 Faces and houses. 00:53:41.930 --> 00:53:43.190 Lots of ways to do this. 00:53:43.190 --> 00:53:46.987 But it's not even my experiment, and they used faces and houses. 00:53:46.987 --> 00:53:49.070 OK, so they did a version of that very same thing. 00:53:49.070 --> 00:53:51.230 This is a bunch of garbage flashing on. 00:53:51.230 --> 00:53:52.470 Early on, there's a face. 00:53:52.470 --> 00:53:54.345 The subjects have to say which of those three 00:53:54.345 --> 00:53:55.920 faces they've studied it is. 00:53:55.920 --> 00:53:58.520 And then after that, a scene comes on, 00:53:58.520 --> 00:54:00.290 or it doesn't come on. 00:54:00.290 --> 00:54:03.110 OK, they have to just say, was there a scene? 00:54:03.110 --> 00:54:04.790 First of all, which face was it? 00:54:04.790 --> 00:54:07.350 And was there a scene afterwards? 00:54:07.350 --> 00:54:10.000 OK, so it's a variant of the thing you just did. 00:54:10.000 --> 00:54:12.810 So here's the behavioral data. 00:54:12.810 --> 00:54:14.760 If you don't have to report the face, 00:54:14.760 --> 00:54:17.580 then you are very accurate reporting the scene. 00:54:17.580 --> 00:54:19.380 If you do have to report the face, 00:54:19.380 --> 00:54:22.980 then you're very bad at it if the scene comes right after. 00:54:22.980 --> 00:54:24.690 But if there's a big interval in between, 00:54:24.690 --> 00:54:25.740 you do OK with the scene. 00:54:25.740 --> 00:54:28.260 Same thing we saw before but now with faces and scenes. 00:54:28.260 --> 00:54:30.390 OK, that's the behavioral data. 00:54:30.390 --> 00:54:32.700 What do you see in the PPA, right? 00:54:32.700 --> 00:54:34.920 The second target is always a scene. 00:54:34.920 --> 00:54:37.500 So what you see in the PPA, here's 00:54:37.500 --> 00:54:42.090 a response in the PPA to that second scene if it's a hit. 00:54:42.090 --> 00:54:43.680 That is if you detect it, right? 00:54:43.680 --> 00:54:46.500 You correctly say, yes, there was a scene in that trial. 00:54:46.500 --> 00:54:48.490 Here's a response with a correct reject. 00:54:48.490 --> 00:54:49.950 There was no scene in that trial. 00:54:49.950 --> 00:54:52.290 And you correctly said there was not. 00:54:52.290 --> 00:54:55.110 OK, so that difference shows you the response 00:54:55.110 --> 00:54:58.320 in the PPA to a scene that you've seen, 00:54:58.320 --> 00:55:00.360 that you detected consciously. 00:55:00.360 --> 00:55:02.902 But here's a critical case. 00:55:02.902 --> 00:55:04.860 I don't know why there's a little pop up there. 00:55:04.860 --> 00:55:08.250 Anyway, this is a case where there was a scene, 00:55:08.250 --> 00:55:10.370 but you've said there wasn't. 00:55:10.370 --> 00:55:10.870 OK? 00:55:10.870 --> 00:55:11.745 That's called a miss. 00:55:11.745 --> 00:55:12.370 You missed it. 00:55:12.370 --> 00:55:14.710 It was there, and you didn't see it. 00:55:14.710 --> 00:55:17.830 And what it shows you is two cool things. 00:55:17.830 --> 00:55:21.490 Well, first of all, it tells you that the more aware you 00:55:21.490 --> 00:55:24.010 are of the stimulus, the stronger response. 00:55:24.010 --> 00:55:27.120 But the crucial thing it shows you 00:55:27.120 --> 00:55:29.880 is this difference right here, which is significant. 00:55:29.880 --> 00:55:33.030 This is a kind of perception without awareness. 00:55:33.030 --> 00:55:34.650 You did not detect the scene. 00:55:34.650 --> 00:55:36.000 You said there was no scene. 00:55:36.000 --> 00:55:38.850 But your PPA detected the difference. 00:55:38.850 --> 00:55:40.930 Everybody get that? 00:55:40.930 --> 00:55:42.900 So we have evidence for perception 00:55:42.900 --> 00:55:47.160 by the PPA at least of a scene without awareness. 00:55:47.160 --> 00:55:48.730 That make sense? 00:55:48.730 --> 00:55:51.650 So there are many, many studies like this that kind of 00:55:51.650 --> 00:55:52.650 take it every which way. 00:55:52.650 --> 00:55:54.630 This is just one little example of how 00:55:54.630 --> 00:55:58.200 you can use neuroimaging to ask, how far up the system 00:55:58.200 --> 00:56:01.110 does an unseen stimulus get? 00:56:01.110 --> 00:56:03.430 Make sense? 00:56:03.430 --> 00:56:05.800 OK, so we are about out of time. 00:56:05.800 --> 00:56:07.870 And I just gave you a little taste 00:56:07.870 --> 00:56:10.390 of some of the work on neural correlates of awareness, 00:56:10.390 --> 00:56:13.960 showed you, with binocular rivalry, a neural response 00:56:13.960 --> 00:56:17.410 that's correlated with awareness unconfounded from the stimulus, 00:56:17.410 --> 00:56:20.020 uncoupling, again, perceptual awareness from what's 00:56:20.020 --> 00:56:23.650 hitting your retina, and, in the case of the attentional blink, 00:56:23.650 --> 00:56:27.250 some evidence for perceptual representation 00:56:27.250 --> 00:56:29.150 without awareness. 00:56:29.150 --> 00:56:30.700 OK?