WEBVTT 00:12.990 --> 00:17.030 Professor Paul Bloom: We're going to begin the class 00:17.027 --> 00:20.647 proper, Introduction to Psychology, with a discussion 00:20.647 --> 00:23.817 about the brain. And, in particular, 00:23.821 --> 00:28.981 I want to lead off the class with an idea that the Nobel 00:28.978 --> 00:32.838 Prize winning biologist, Francis Crick, 00:32.841 --> 00:36.931 described as "The Astonishing Hypothesis." 00:36.930 --> 00:42.410 And The Astonishing Hypothesis is summarized like this. 00:42.410 --> 00:44.610 As he writes, The Astonishing Hypothesis is 00:44.610 --> 00:46.600 that: You, your joys and your 00:46.597 --> 00:49.567 sorrows, your memories and your ambitions, your sense of 00:49.570 --> 00:52.760 personal identity and free will are in fact no more than the 00:52.759 --> 00:56.109 behavior of a vast assembly of nerve cells and their associated 00:56.111 --> 00:59.271 molecules. As Lewis Carroll's Alice might 00:59.271 --> 01:02.631 have phrased it, "you're nothing but a pack of 01:02.634 --> 01:05.854 neurons." It is fair to describe this as 01:05.849 --> 01:09.089 astonishing. It is an odd and unnatural view 01:09.091 --> 01:13.721 and I don't actually expect people to believe it at first. 01:13.719 --> 01:17.469 It's an open question whether you'll believe it when this 01:17.474 --> 01:21.034 class comes to an end, but I'd be surprised if many of 01:21.027 --> 01:22.567 you believe it now. 01:22.570 --> 01:23.970 Most people don't. 01:23.970 --> 01:28.010 Most people, in fact, hold a different view. 01:28.010 --> 01:30.580 Most people are dualists. 01:30.580 --> 01:34.420 Now, dualism is a very different doctrine. 01:34.420 --> 01:38.340 It's a doctrine that can be found in every religion and in 01:38.339 --> 01:41.639 most philosophical systems throughout history. 01:41.640 --> 01:44.460 It was very explicit in Plato, for instance. 01:44.459 --> 01:49.059 But the most articulate and well-known defender of dualism 01:49.062 --> 01:51.972 is the philosopher Rene Descartes, 01:51.970 --> 01:56.780 and Rene Descartes explicitly asked a question, 01:56.781 --> 02:00.861 "Are humans merely physical machines, 02:00.860 --> 02:01.990 merely physical things?" 02:01.990 --> 02:03.610 And he answered, "no." 02:03.609 --> 02:07.369 He agreed that animals are machines. 02:07.370 --> 02:11.620 In fact, he called them "beast machines" and said animals, 02:11.616 --> 02:15.266 nonhuman animals are merely robots, but people are 02:15.266 --> 02:17.746 different. There's a duality of people. 02:17.750 --> 02:21.710 Like animals, we possess physical material 02:21.705 --> 02:27.295 bodies, but unlike animals, what we are is not physical. 02:27.300 --> 02:31.140 We are immaterial souls that possess physical bodies, 02:31.140 --> 02:35.350 that have physical bodies, that reside in physical bodies, 02:35.350 --> 02:38.010 that connect to physical bodies. 02:38.009 --> 02:40.929 So, this is known as dualism because the claim is, 02:40.925 --> 02:44.075 for humans at least, there are two separate things; 02:44.080 --> 02:48.360 there's our material bodies and there's our immaterial minds. 02:48.360 --> 02:52.500 Now, Descartes made two arguments for dualism. 02:52.500 --> 02:58.740 One argument involved observations of a human action. 02:58.740 --> 03:02.380 So, Descartes lived in a fairly sophisticated time, 03:02.375 --> 03:04.625 and his time did have robots. 03:04.629 --> 03:06.469 These were not electrical robots, of course. 03:06.469 --> 03:09.769 They were robots powered by hydraulics. 03:09.770 --> 03:13.490 So, Descartes would walk around the French Royal Gardens and the 03:13.485 --> 03:16.905 French Royal Gardens were set up like a seventeenth-century 03:16.905 --> 03:19.625 Disneyland. They had these characters that 03:19.628 --> 03:23.488 would operate according to water flow and so if you stepped on a 03:23.488 --> 03:26.778 certain panel, a swordsman would jump out with 03:26.777 --> 03:29.247 a sword. If you stepped somewhere else, 03:29.250 --> 03:32.890 a bathing beauty would cover herself up behind some bushes. 03:32.889 --> 03:36.749 And Descartes said, "Boy, these machines respond in 03:36.750 --> 03:41.150 certain ways to certain actions so machines can do certain 03:41.151 --> 03:43.081 things and, in fact," he says, 03:43.081 --> 03:44.411 "our bodies work that way too. 03:44.410 --> 03:47.320 If you tap somebody on the knee, your leg will jump out. 03:47.320 --> 03:49.770 Well, maybe that's what we are." 03:49.770 --> 03:53.900 But Descartes said that can't be because there are things that 03:53.897 --> 03:56.737 humans do that no machine could ever do. 03:56.740 --> 04:00.390 Humans are not limited to reflexive action. 04:00.389 --> 04:04.699 Rather, humans are capable of coordinated, creative, 04:04.696 --> 04:06.466 spontaneous things. 04:06.469 --> 04:08.529 We can use language, for instance, 04:08.527 --> 04:11.767 and sometimes my use of language can be reflexive. 04:11.770 --> 04:13.020 Somebody says, "How are you?" 04:13.020 --> 04:14.080 And I say, "I am fine. 04:14.080 --> 04:18.000 How are you?" But sometimes I could say what 04:18.002 --> 04:20.332 I choose to be, "How are you?" 04:20.330 --> 04:21.130 "Pretty damn good." 04:21.130 --> 04:23.010 I can just choose. 04:23.009 --> 04:24.749 And machines, Descartes argued, 04:24.749 --> 04:27.009 are incapable of that sort of choice. 04:27.010 --> 04:30.930 Hence, we are not mere machines. 04:30.930 --> 04:34.350 The second argument is, of course, quite famous and 04:34.353 --> 04:35.863 this was the method. 04:35.860 --> 04:39.030 This he came to using the method of doubt. 04:39.029 --> 04:41.759 So, he started asking himself the question, 04:41.759 --> 04:43.449 "What can I be sure of?" 04:43.449 --> 04:46.649 And he said, "Well, I believe there's a God, 04:46.653 --> 04:50.083 but honestly, I can't be sure there's a God. 04:50.079 --> 04:53.439 I believe I live in a rich country but maybe I've been 04:53.436 --> 04:55.166 fooled." He even said, 04:55.170 --> 05:00.250 "I believe I have had friends and family but maybe I am being 05:00.248 --> 05:02.548 tricked. Maybe an evil demon, 05:02.554 --> 05:04.484 for instance, has tricked me, 05:04.478 --> 05:08.458 has deluded me into thinking I have experiences that aren't 05:08.464 --> 05:10.204 real." And, of course, 05:10.198 --> 05:12.938 the modern version of this is The Matrix. 05:12.939 --> 05:15.489 The idea of The Matrix is explicitly built upon 05:15.488 --> 05:18.368 Cartesian--Descartes' worries about an evil demon. 05:18.370 --> 05:21.880 Maybe everything you're now experiencing is not real, 05:21.879 --> 05:25.859 but rather is the product of some other, perhaps malevolent, 05:25.862 --> 05:28.782 creature. Descartes, similarly, 05:28.778 --> 05:31.398 could doubt he has a body. 05:31.399 --> 05:34.409 In fact, he noticed that madmen sometimes believe they have 05:34.411 --> 05:37.371 extra limbs or they believe they're of different sizes and 05:37.371 --> 05:40.021 shapes than they really are and Descartes said, 05:40.020 --> 05:41.740 "How do I know I'm not crazy? 05:41.740 --> 05:44.740 Crazy people don't think they're crazy so the fact that I 05:44.738 --> 05:47.468 don't think I'm crazy doesn't mean I'm not crazy. 05:47.470 --> 05:51.550 How do I know," Descartes said, "I'm not dreaming right now?" 05:51.550 --> 05:54.160 But there is one thing, Descartes concluded, 05:54.163 --> 05:57.083 that he cannot doubt, and the answer is he cannot 05:57.080 --> 05:59.390 doubt that he is himself thinking. 05:59.390 --> 06:01.370 That would be self-refuting. 06:01.370 --> 06:06.120 And so, Descartes used the method of doubt to say there's 06:06.118 --> 06:11.118 something really different about having a body that's always 06:11.121 --> 06:13.921 uncertain from having a mind. 06:13.920 --> 06:18.820 And he used this argument as a way to support dualism, 06:18.823 --> 06:23.733 as a way to support the idea that bodies and minds are 06:23.727 --> 06:26.077 separate. And so he concluded, 06:26.077 --> 06:29.577 "I knew that I was a substance, the whole essence or nature of 06:29.575 --> 06:32.465 which is to think, and that for its existence, 06:32.470 --> 06:35.850 there is no need of any place nor does it depend on any 06:35.852 --> 06:38.402 material thing. That is to say, 06:38.404 --> 06:43.534 the soul by which I am, when I am, is entirely distinct 06:43.530 --> 06:46.700 from body." Now, I said before that this is 06:46.698 --> 06:49.838 common sense and I want to illustrate the common sense 06:49.842 --> 06:51.742 nature of this in a few ways. 06:51.740 --> 06:55.970 One thing is our dualism is enmeshed in our language. 06:55.970 --> 06:59.640 So, we have a certain mode of talking about things that we own 06:59.635 --> 07:02.275 or things that are close to us – my arm, 07:02.279 --> 07:05.729 my heart, my child, my car – but we also extend 07:05.725 --> 07:07.945 that to my body and my brain. 07:07.949 --> 07:12.249 We talk about owning our brains as if we're somehow separate 07:12.246 --> 07:14.726 from them. Our dualism shows up in 07:14.733 --> 07:17.263 intuitions about personal identity. 07:17.259 --> 07:21.389 And what this means is that common sense tells us that 07:21.394 --> 07:26.004 somebody can be the same person even if their body undergoes 07:25.995 --> 07:28.565 radical and profound changes. 07:28.569 --> 07:32.599 The best examples of this are fictional. 07:32.600 --> 07:36.230 So, we have no problem understanding a movie where 07:36.226 --> 07:39.996 somebody goes to sleep as a teenager and wakes up as 07:40.000 --> 07:42.960 Jennifer Garner, as an older person. 07:42.959 --> 07:46.429 Now, nobody says, "Oh, that's a documentary. 07:46.430 --> 07:51.080 I believe that thoroughly true" but at the same time nobody, 07:51.078 --> 07:54.568 no adult, no teenager, no child ever leaves and says, 07:54.572 --> 07:56.552 "I'm totally conceptually confused." 07:56.550 --> 08:01.390 Rather, we follow the story. 08:01.389 --> 08:05.549 We can also follow stories which involve more profound 08:05.551 --> 08:10.341 transformations as when a man dies and is reborn into the body 08:10.342 --> 08:13.202 of a child. Now, you might have different 08:13.198 --> 08:16.788 views around--People around this room will have different views 08:16.785 --> 08:19.385 as to whether reincarnation really exists, 08:19.390 --> 08:21.010 but we can imagine it. 08:21.009 --> 08:24.469 We could imagine a person dying and then reemerging in another 08:24.472 --> 08:27.292 body. This is not Hollywood invention. 08:27.290 --> 08:30.540 One of the great short stories of the last century begins with 08:30.544 --> 08:33.274 a sentence by Franz Kafka: "As Gregor Samsa woke one 08:33.265 --> 08:36.635 morning from uneasy dreams, he found himself transformed in 08:36.639 --> 08:38.469 his bed into a gigantic insect." 08:38.470 --> 08:43.520 And again, Kafka invites us to imagine waking up into a body of 08:43.515 --> 08:45.545 a cockroach and we can. 08:45.550 --> 08:47.410 This is also not modern. 08:47.409 --> 08:51.359 Hundreds of years before the birth of Christ, 08:51.360 --> 08:56.930 Homer described the fate of the companions of Odysseus who were 08:56.927 --> 09:00.247 transformed by a witch into pigs. 09:00.250 --> 09:01.690 Actually, that's not quite right. 09:01.690 --> 09:04.120 She didn't turn them into pigs. 09:04.120 --> 09:05.620 She did something worse. 09:05.620 --> 09:08.810 She stuck them in the bodies of pigs. 09:08.809 --> 09:11.829 They had the head and voice and bristles and body of swine but 09:11.833 --> 09:14.813 their minds remained unchanged as before, so they were penned 09:14.807 --> 09:17.567 there weeping. And we are invited to imagine 09:17.572 --> 09:21.252 the fate of again finding ourselves in the bodies of other 09:21.252 --> 09:24.172 creatures and, if you can imagine this, 09:24.169 --> 09:27.809 this is because you are imagining what you are as 09:27.808 --> 09:31.218 separate from the body that you reside in. 09:31.220 --> 09:34.630 We allow for the notion that many people can occupy one body. 09:34.629 --> 09:37.649 This is a mainstay of some slapstick humor including the 09:37.651 --> 09:40.071 classic movie, All of Me--Steve Martin 09:40.068 --> 09:42.428 and Lily Tomlin – highly recommended. 09:42.429 --> 09:46.359 But many people think this sort of thing really happens. 09:46.360 --> 09:50.300 One analysis of multiple personality disorder is that you 09:50.298 --> 09:54.238 have many people inside a single body fighting it out for 09:54.236 --> 09:56.626 control. Now, we will discuss multiple 09:56.632 --> 10:00.062 personality disorder towards the end of the semester and it turns 10:00.058 --> 10:03.108 out things are a good deal more complicated than this, 10:03.110 --> 10:06.300 but still my point isn't about how it really is but how we 10:06.298 --> 10:09.118 think about it. Common sense tells us you could 10:09.121 --> 10:12.021 have more than one person inside a single body. 10:12.019 --> 10:15.839 This shows up in a different context involving exorcisms 10:15.843 --> 10:19.813 where many belief systems allow for the idea that people's 10:19.806 --> 10:22.416 behavior, particularly their evil or 10:22.419 --> 10:25.769 irrational behavior, could be because something else 10:25.772 --> 10:27.812 has taken over their bodies. 10:27.809 --> 10:35.369 Finally, most people around the world, all religions and most 10:35.366 --> 10:40.526 people in most countries at most times, 10:40.529 --> 10:44.659 believe that people can survive the destruction of their bodies. 10:44.659 --> 10:49.909 Now, cultures differ according to the fate of the body. 10:49.909 --> 10:53.199 Some cultures have the body going to--sorry--the fate of the 10:53.199 --> 10:55.329 soul. Some cultures have you going to 10:55.328 --> 10:57.008 Heaven or descending to Hell. 10:57.009 --> 10:59.279 Others have you occupying another body. 10:59.279 --> 11:02.629 Still, others have you occupying an amorphous spirit 11:02.625 --> 11:04.965 world. But what they share is the idea 11:04.974 --> 11:08.394 that what you are is separable from this physical thing you 11:08.388 --> 11:12.738 carry around. And the physical thing that you 11:12.740 --> 11:18.130 carry around can be destroyed while you live on. 11:18.129 --> 11:22.029 These views are particularly common in the United States. 11:22.029 --> 11:25.039 In one survey done in Chicago a few years ago, 11:25.042 --> 11:28.462 people were asked their religion and then were asked 11:28.457 --> 11:31.467 what would happen to them when they died. 11:31.470 --> 11:35.260 Most people in the sample were Christian and about 96% of 11:35.257 --> 11:38.367 Christians said, "When I die I'm going to go to 11:38.368 --> 11:40.998 Heaven." Some of the sample was Jewish. 11:41.000 --> 11:44.830 Now, Judaism is actually a religion with a less than clear 11:44.829 --> 11:46.709 story about the afterlife. 11:46.710 --> 11:50.780 Still, most of the subjects who identified themselves as Jewish 11:50.775 --> 11:53.655 said when they die they will go to Heaven. 11:53.659 --> 11:56.679 Some of the sampled denied having any religion at all--said 11:56.683 --> 11:58.303 they have no religion at all. 11:58.299 --> 12:02.059 Still, when these people were asked what would happen when 12:02.063 --> 12:04.513 they would die, most of them answered, 12:04.506 --> 12:06.616 "I'm going to go to Heaven." 12:06.620 --> 12:09.210 So, dualism is emmeshed. 12:09.210 --> 12:12.980 A lot rests on it but, as Crick points out; 12:12.980 --> 12:18.080 the scientific consensus now is that dualism is wrong. 12:18.080 --> 12:24.270 There is no "you" separable or separate from your body. 12:24.269 --> 12:27.519 In particular, there is no "you" separable 12:27.522 --> 12:30.852 from your brain. To put it the way cognitive 12:30.852 --> 12:35.292 scientists and psychologists and neuroscientists like to put it, 12:35.292 --> 12:37.902 "the mind is what the brain does." 12:37.899 --> 12:42.099 The mind reflects the workings of the brain just like 12:42.096 --> 12:46.046 computation reflects the working of a computer. 12:46.049 --> 12:49.569 Now, why would you hold such an outrageous view? 12:49.570 --> 12:52.610 Why would you reject dualism in favor of this alternative? 12:52.610 --> 12:54.260 Well, a few reasons. 12:54.259 --> 12:57.699 One reason is dualism has always had its problems. 12:57.700 --> 13:00.230 For one thing, it's a profoundly unscientific 13:00.227 --> 13:02.837 doctrine. We want to know as curious 13:02.844 --> 13:06.434 people how children learn language, what we find 13:06.431 --> 13:10.861 attractive or unattractive, and what's the basis for mental 13:10.857 --> 13:13.587 illness. And dualism simply says, 13:13.592 --> 13:17.222 "it's all nonphysical, it's part of the ether," and 13:17.223 --> 13:19.333 hence fails to explain it. 13:19.330 --> 13:22.950 More specifically, dualists like Descartes 13:22.951 --> 13:27.631 struggle to explain how a physical body connects to an 13:27.633 --> 13:30.753 immaterial soul. What's the conduit? 13:30.750 --> 13:32.370 How could this connection be made? 13:32.370 --> 13:35.950 After all, Descartes knew full well that there is such a 13:35.953 --> 13:39.563 connection. Your body obeys your commands. 13:39.559 --> 13:43.419 If you bang your toe or stub your toe you feel pain. 13:43.419 --> 13:46.399 If you drink alcohol it affects your reasoning, 13:46.401 --> 13:49.971 but he could only wave his hands as to how this physical 13:49.966 --> 13:53.786 thing in the world could connect to an immaterial mind. 13:53.790 --> 13:57.410 13:57.409 --> 14:02.019 Descartes, when he was alive, was reasonable enough 14:02.023 --> 14:07.563 concluding that physical objects cannot do certain things. 14:07.559 --> 14:10.799 He was reasonable enough in concluding, for instance, 14:10.797 --> 14:14.527 as he did, that there's no way a merely physical object could 14:14.532 --> 14:17.582 ever play a game of chess because--and that such a 14:17.583 --> 14:21.443 capacity is beyond the capacity of the physical world and hence 14:21.443 --> 14:25.053 you have to apply--you have to extend the explanation to an 14:25.054 --> 14:28.484 immaterial soul but now we know--we have what scientists 14:28.478 --> 14:30.718 call an existence proof. 14:30.720 --> 14:34.550 We know physical objects can do complicated and interesting 14:34.554 --> 14:36.854 things. We know, for instance, 14:36.849 --> 14:38.779 machines can play chess. 14:38.779 --> 14:40.949 We know machines can manipulate symbols. 14:40.950 --> 14:45.130 We know machines have limited capacities to engage in 14:45.133 --> 14:48.113 mathematical and logical reasoning, 14:48.110 --> 14:51.840 to recognize things, to do various forms of 14:51.837 --> 14:55.297 computations, and this makes it at least 14:55.298 --> 14:58.758 possible that we are such machines. 14:58.760 --> 15:01.030 So you can no longer say, "Look. 15:01.029 --> 15:04.649 Physical things just can't do that" because we know physical 15:04.650 --> 15:08.150 things can do a lot and this opens up the possibility that 15:08.147 --> 15:11.167 humans are physical things, in particular, 15:11.166 --> 15:13.076 that humans are brains. 15:13.080 --> 15:18.410 Finally, there is strong evidence that the brain is 15:18.408 --> 15:21.178 involved in mental life. 15:21.179 --> 15:24.639 Somebody who hold a--held a dualist view that said that what 15:24.644 --> 15:28.054 we do and what we decide and what we think and what we want 15:28.050 --> 15:31.280 are all have nothing to do with the physical world, 15:31.279 --> 15:35.369 would be embarrassed by the fact that the brain seems to 15:35.365 --> 15:39.445 correspond in intricate and elaborate ways to our mental 15:39.451 --> 15:42.991 life. Now, this has been known for a 15:42.988 --> 15:45.838 long time. Philosophers and psychologists 15:45.837 --> 15:48.947 knew for a long time that getting smacked in the head 15:48.953 --> 15:51.233 could change your mental faculties; 15:51.230 --> 15:54.810 that diseases like syphilis could make you deranged; 15:54.809 --> 15:59.699 that chemicals like caffeine and alcohol can affect how you 15:59.696 --> 16:02.196 think. But what's new is we can now in 16:02.197 --> 16:05.377 different ways see the direct effects of mental life. 16:05.379 --> 16:10.349 Somebody with a severe and profound loss of mental 16:10.351 --> 16:16.241 faculties--the deficit will be shown correspondingly in her 16:16.235 --> 16:18.975 brain. Studies using imaging 16:18.984 --> 16:22.294 techniques like CAT scans, PET, and fMRI, 16:22.288 --> 16:27.328 illustrate that different parts of the brain are active during 16:27.326 --> 16:30.296 different parts of mental life. 16:30.299 --> 16:32.929 For instance, the difference between seeing 16:32.931 --> 16:36.001 words, hearing words, reading words and generating 16:36.000 --> 16:39.320 words can correspond to different aspects of what part 16:39.320 --> 16:41.200 of your brain is active. 16:41.200 --> 16:43.960 To some extent, if we put you in an fMRI 16:43.959 --> 16:47.779 scanner and observed what you're doing in real time, 16:47.779 --> 16:51.929 by looking at the activity patterns in your brain we can 16:51.929 --> 16:56.309 tell whether you are thinking about music or thinking about 16:56.306 --> 16:58.806 sex. To some extent we can tell 16:58.806 --> 17:03.326 whether you're solving a moral dilemma versus something else. 17:03.330 --> 17:07.800 And this is no surprise if what we are is the workings of our 17:07.795 --> 17:11.135 physical brains, but it is extremely difficult 17:11.144 --> 17:13.754 to explain if one is a dualist. 17:13.750 --> 17:18.510 Now, so what you have is--the scientific consensus is that all 17:18.505 --> 17:22.705 of mental life including consciousness and emotions and 17:22.714 --> 17:27.474 choice and morality are the products of brain activities. 17:27.470 --> 17:32.560 So, you would expect that when you rip open the skull and look 17:32.558 --> 17:35.868 at the brain; you'd see something glorious, 17:35.873 --> 17:40.073 you'd see – I don't know – a big, shiny thing with glass 17:40.070 --> 17:44.410 tubes and blinding lights and sparks and wonderful colors. 17:44.410 --> 17:47.820 And actually though, the brain is just disgusting. 17:47.820 --> 17:51.110 It looks like an old meat loaf. 17:51.109 --> 17:55.329 It's gray when you take it out of the head. 17:55.329 --> 17:58.499 It's called gray matter but that's just because it's out of 17:58.498 --> 18:01.128 the head. Inside the head it's bright red 18:01.134 --> 18:03.304 because it's pulsing with blood. 18:03.300 --> 18:06.720 It doesn't even taste good. 18:06.720 --> 18:09.460 Well, has anybody here ever eaten brain? 18:09.460 --> 18:12.960 18:12.960 --> 18:16.430 It's good with cream sauce but everything's good with cream 18:16.431 --> 18:19.521 sauce. So, the question is, 18:19.521 --> 18:25.661 "How can something like this give rise to us?" 18:25.660 --> 18:29.070 And you have to have some sympathy for Descartes. 18:29.069 --> 18:31.489 There's another argument Descartes could have made that's 18:31.485 --> 18:33.465 a lot less subtle than the ones he did make, 18:33.470 --> 18:37.580 which is "That thing responsible for free will and 18:37.582 --> 18:39.682 love and consciousness? 18:39.680 --> 18:42.470 Ridiculous." What I want to do, 18:42.471 --> 18:45.311 and what the goal of neuroscience is, 18:45.314 --> 18:50.524 is to make it less ridiculous, to try to explain how the brain 18:50.515 --> 18:54.445 works, how the brain can give rise to thought, 18:54.450 --> 18:57.890 and what I want to do today is take a first stab at this 18:57.891 --> 19:01.141 question but it's something we'll continue to discuss 19:01.144 --> 19:04.774 throughout the course as we talk about different aspects of 19:04.773 --> 19:07.703 mental life. What I want to do though now is 19:07.696 --> 19:09.026 provide a big picture. 19:09.029 --> 19:12.539 So, what I want to do is start off small, with the smallest 19:12.542 --> 19:16.122 interesting part of the brain and then get bigger and bigger 19:16.115 --> 19:19.865 and bigger – talk about how the small part of the brain, 19:19.869 --> 19:22.159 the neurons, the basic building blocks of 19:22.161 --> 19:25.661 thought, combine to other mental structures and into different 19:25.655 --> 19:28.915 subparts of the brain and finally to the whole thing. 19:28.920 --> 19:35.170 So, one of the discoveries of psychology is that the basic 19:35.167 --> 19:40.097 unit of the brain appears to be the neuron. 19:40.099 --> 19:44.429 The neuron is a specific sort of cell and the neuron has three 19:44.431 --> 19:47.911 major parts, as you could see illustrated here. 19:47.910 --> 19:50.880 Neurons actually look quite different from one another but 19:50.879 --> 19:52.129 this is a typical one. 19:52.130 --> 19:57.380 There are the dendrites – these little tentacles here. 19:57.380 --> 20:01.760 And the dendrites get signals from other neurons. 20:01.759 --> 20:04.429 Now, these signals can be either excitatory, 20:04.425 --> 20:08.325 which is that they raise the likelihood the neuron will fire, 20:08.329 --> 20:12.019 or inhibitory in that they lower the likelihood that the 20:12.023 --> 20:13.303 neuron will fire. 20:13.299 --> 20:16.029 The cell body sums it up and you could view it 20:16.029 --> 20:19.709 arithmetically. The excitatory signals are 20:19.706 --> 20:23.876 pluses, the inhibitory ones are minuses. 20:23.880 --> 20:27.660 And then if you get a certain number, plus 60 or something, 20:27.660 --> 20:30.790 the neuron will fire and it fires along the axon, 20:30.789 --> 20:32.549 the thing to the right. 20:32.549 --> 20:35.999 The axon is much longer than the dendrites and, 20:36.002 --> 20:39.082 in fact, some axons are many feet long. 20:39.079 --> 20:44.589 There's an axon leading from your spinal cord to your big toe 20:44.592 --> 20:49.532 for instance. It is so shocking the lights go 20:49.526 --> 20:52.076 out. Surrounded--Surrounding--To 20:52.084 --> 20:56.644 complete a mechanical metaphor that would have led Descartes to 20:56.641 --> 20:58.921 despair-- Thank you, Koleen. 20:58.920 --> 21:02.120 Surrounding the axon is a myelin sheath, 21:02.117 --> 21:05.067 which is actually just insulation. 21:05.069 --> 21:07.409 It helps the firing work quicker. 21:07.410 --> 21:10.050 So, here are some facts about neurons. 21:10.049 --> 21:14.349 There are a lot of them – about one thousand billion of 21:14.347 --> 21:19.257 them – and each neuron can be connected to around thousands, 21:19.259 --> 21:21.769 perhaps tens of thousands, other neurons. 21:21.769 --> 21:26.649 So, it's an extraordinarily complicated computing device. 21:26.650 --> 21:29.140 Neurons come in three flavors. 21:29.140 --> 21:32.130 There are sensory neurons, which take information from the 21:32.129 --> 21:34.349 world so as you see me, for instance, 21:34.354 --> 21:38.514 there are neurons firing from your retina sending signals to 21:38.505 --> 21:41.115 your brain. There are motor neurons. 21:41.119 --> 21:45.049 If you decide to raise your hand, those are motor neurons 21:45.046 --> 21:47.356 telling the muscles what to do. 21:47.359 --> 21:51.689 And there are interneurons which connect the two. 21:51.690 --> 21:53.930 And basically, the interneurons do the 21:53.925 --> 21:56.435 thinking. They make the connection 21:56.443 --> 21:58.763 between sensation and action. 21:58.759 --> 22:02.179 It used to be believed, and it's the sort of thing I 22:02.182 --> 22:06.342 would--when I taught this course many years ago I would lecture 22:06.344 --> 22:10.174 on--that neurons do not grow back once you lose them. 22:10.170 --> 22:11.530 You never get them back. 22:11.530 --> 22:13.680 This is actually not true. 22:13.680 --> 22:17.940 There are parts of the brain in which neurons can re-grow. 22:17.940 --> 22:22.540 One interesting thing about neurons is a neuron is like a 22:22.537 --> 22:25.447 gun. It either fires or it doesn't. 22:25.450 --> 22:27.330 It's all or nothing. 22:27.329 --> 22:31.299 If you squeeze the trigger of a gun really hard and really fast, 22:31.301 --> 22:35.151 it doesn't fire any faster or harder than if you just squeezed 22:35.147 --> 22:39.497 it gently. Now, this seems to be strange. 22:39.500 --> 22:44.260 How could neurons be all or nothing when sensation is very 22:44.258 --> 22:47.128 graded? If somebody next to you pushed 22:47.125 --> 22:51.285 on your hand--the degree of pushing--you'd be able to notice 22:51.286 --> 22:52.826 it. It's not either pushing or not 22:52.825 --> 22:55.365 pushing. You can--Degrees of pushing, 22:55.371 --> 22:58.531 degrees of heat, degrees of brightness. 22:58.529 --> 23:00.909 And the answer is, although neurons are all or 23:00.911 --> 23:03.241 nothing, there are ways to code intensity. 23:03.240 --> 23:06.370 So, one simple way to code intensity is the number of 23:06.367 --> 23:10.487 neurons firing; the more neurons the more 23:10.492 --> 23:14.542 intense. Another way to increase 23:14.543 --> 23:19.393 intensity is the frequency of firing. 23:19.390 --> 23:23.650 So, I'll just use those two. 23:23.650 --> 23:25.260 The first one is the number of neurons firing. 23:25.259 --> 23:29.749 The second one is the frequency of firing in that something is 23:29.753 --> 23:33.003 more intense if it's "bang, bang, bang, bang, 23:32.995 --> 23:36.825 bang, bang" then "bang, bang, bang" and these are two 23:36.826 --> 23:40.506 ways through which neurons encode intensity. 23:40.509 --> 23:45.319 Now, neurons are connected and they talk to one another and it 23:45.323 --> 23:49.583 used to be thought they were tied to one another like a 23:49.584 --> 23:52.044 computer, like you take wires and you 23:52.042 --> 23:54.802 connect wires to each other, you wrap them around and 23:54.801 --> 23:57.651 connect them. It turns out this isn't the 23:57.646 --> 23:59.516 case. It turns out that neurons 23:59.518 --> 24:03.118 relate to one another chemically in a kind of interesting way. 24:03.119 --> 24:06.829 Between any neurons, between the axon of one neuron 24:06.825 --> 24:10.525 and the dendrite of another, there's a tiny gap. 24:10.529 --> 24:14.069 The gap could be about one ten-thousandths of a millimeter 24:14.065 --> 24:16.485 wide. This infinitesimal gap--and 24:16.489 --> 24:20.169 this gap is known as a synapse--and what happens is 24:20.172 --> 24:23.342 when a neuron fires, an axon sends chemicals 24:23.339 --> 24:25.549 shooting through the gap. 24:25.549 --> 24:29.109 These chemicals are known as neurotransmitters and they 24:29.105 --> 24:30.615 affect the dendrites. 24:30.619 --> 24:33.959 So, neurons communicate to one another chemically. 24:33.960 --> 24:37.570 These--Again, the chemicals could excite the 24:37.569 --> 24:42.519 other neuron (excitatory) bring up the chances it will fire, 24:42.522 --> 24:46.302 or inhibit the other neuron (inhibitory). 24:46.299 --> 24:52.149 Now, neurotransmitters become interesting because a lot of 24:52.146 --> 24:56.436 psychopharmacology, both of the medical sort and 24:56.442 --> 25:00.042 the recreational sort, consists of fiddling with 25:00.039 --> 25:04.249 neurotransmitters and so you could see this through some 25:04.248 --> 25:07.608 examples. There are two sorts of ways you 25:07.607 --> 25:10.187 could fiddle with neurotransmitters, 25:10.190 --> 25:13.290 and correspondingly two sorts of drugs. 25:13.290 --> 25:15.010 There are agonists. 25:15.009 --> 25:18.569 And what an agonist does is increases the effect of 25:18.567 --> 25:21.337 neurotransmitters, either by making more 25:21.342 --> 25:24.402 neurotransmitters or stopping the cleanup of 25:24.402 --> 25:27.732 neurotransmitters, or in some cases by faking a 25:27.727 --> 25:30.267 neurotransmitter, by mimicking its effects. 25:30.269 --> 25:33.619 Then, there are antagonists that slow down the amount of 25:33.615 --> 25:36.345 neurotransmitters, either because they destroy 25:36.352 --> 25:39.882 neurotransmitters or they make it hard to create more. 25:39.880 --> 25:43.500 Or in some cases they go to the dendrite of the neuron and they 25:43.499 --> 25:47.119 kind of put a paste over it so that the neurotransmitters can't 25:47.119 --> 25:49.809 connect. And it's through these clever 25:49.808 --> 25:53.028 ways that neurons can affect your mental life. 25:53.030 --> 25:56.180 25:56.180 --> 26:03.790 So, for instance, there is a drug known as Curare 26:03.786 --> 26:08.536 and Curare is an antagonist. 26:08.539 --> 26:11.139 It's a very particular sort of antagonist. 26:11.140 --> 26:16.690 It blocks motor neurons from affecting muscle fibers. 26:16.690 --> 26:20.620 What this does then is it paralyzes you because your motor 26:20.623 --> 26:24.073 neurons--You send the command to your arm to stand, 26:24.074 --> 26:26.344 to lift up. It doesn't work. 26:26.339 --> 26:28.419 You send the command to your leg to move. 26:28.420 --> 26:31.410 It doesn't work. The motor neurons are 26:31.409 --> 26:35.779 deactivated and then, because the way you breathe is 26:35.778 --> 26:39.118 through motor neurons, you then die. 26:39.120 --> 26:43.150 There's alcohol. Alcohol is inhibitory. 26:43.150 --> 26:45.380 Now, this may be puzzling to people. 26:45.380 --> 26:48.550 It's mildly paradoxical because you may be thinking, 26:48.554 --> 26:50.364 "alcohol is not inhibitory. 26:50.359 --> 26:53.289 On the contrary, when I drink a lot of alcohol I 26:53.285 --> 26:56.455 lose my inhibitions and become a more fun person. 26:56.460 --> 27:01.340 I become more aggressive and more sexually vibrant and simply 27:01.337 --> 27:06.497 more beautiful. And so in what way is alcohol 27:06.496 --> 27:11.386 inhibitory?" Well, the answer is it inhibits 27:11.391 --> 27:15.111 the inhibitory parts of your brain. 27:15.109 --> 27:17.679 So, you have parts of your brain that are basically telling 27:17.677 --> 27:20.197 you now, largely in the frontal lobes, that are--"Okay. 27:20.200 --> 27:21.960 Keep your pants on. 27:21.960 --> 27:23.790 Don't hit me, buddy. 27:23.790 --> 27:25.460 Don't use bad words." 27:25.460 --> 27:29.560 Alcohol relaxes, shuts down those parts of the 27:29.560 --> 27:32.020 brain. If you take enough alcohol, 27:32.023 --> 27:35.623 it then goes down to inhibit the excitatory parts of your 27:35.617 --> 27:39.017 brain and then you fall on the floor and pass out. 27:39.019 --> 27:44.169 Amphetamines increase the amount of arousal. 27:44.170 --> 27:47.390 In particular, they increase the amount of 27:47.392 --> 27:50.542 norepinephrine, a neurotransmitter that's 27:50.537 --> 27:53.757 responsible for just general arousal. 27:53.759 --> 27:59.059 And so, amphetamines include drugs like "speed" and "coke." 27:59.059 --> 28:06.869 There are--Prozac works on serotonin. 28:06.869 --> 28:10.469 When we discuss clinical psychology and depression we'll 28:10.472 --> 28:14.072 learn the extent to which neurotransmitter disorders are 28:14.074 --> 28:17.484 implicated in certain disorders like depression. 28:17.480 --> 28:22.800 And one problem is that – for depression – is that there's 28:22.800 --> 28:27.510 too little of a neurotransmitter known as serotonin. 28:27.509 --> 28:32.879 Prozac makes serotonin more prevalent and so in some extent 28:32.881 --> 28:36.031 might help alleviate depression. 28:36.029 --> 28:40.059 Parkinson's disease is a disease involving destruction of 28:40.055 --> 28:44.435 motor control and loss of motor control, difficulty moving. 28:44.440 --> 28:47.890 And one factor in Parkinson's is too little of a 28:47.892 --> 28:50.612 neurotransmitter known as dopamine. 28:50.609 --> 28:54.649 The drug L-DOPA increases the supply of dopamine and so there 28:54.645 --> 28:57.805 is something to alleviate, at least temporarily, 28:57.807 --> 28:59.957 the symptoms of Parkinson's. 28:59.960 --> 29:03.020 So, you have neurons and they're clustered together and 29:03.019 --> 29:05.739 they fire and they communicate to one another. 29:05.740 --> 29:09.860 So, how does this all work to give rise to creatures who could 29:09.864 --> 29:12.844 do interesting things like talk and think? 29:12.839 --> 29:15.719 Well, again, it used to be believed that the 29:15.719 --> 29:18.129 brain is wired up like a computer, 29:18.130 --> 29:21.990 like a PC or a Mac or something like that, but we know this 29:21.994 --> 29:24.734 can't be true. It can't be true because 29:24.734 --> 29:29.134 there's two ways in which the brain is better than a computer. 29:29.130 --> 29:34.170 For one thing, the brain is highly resistant 29:34.172 --> 29:37.772 to damage. If you have a laptop and I 29:37.770 --> 29:42.660 persuade you to open it up for me and I take the pliers and 29:42.656 --> 29:45.686 kind of snip just about anywhere, 29:45.690 --> 29:49.460 your laptop will be destroyed but the brain is actually more 29:49.462 --> 29:52.042 resilient. You can take a lot of brain 29:52.036 --> 29:55.446 damage and still preserve some mental functioning. 29:55.450 --> 29:58.710 To some interesting sense, there's some sort of damage 29:58.708 --> 30:02.518 resistance built in to the brain that allows different parts of 30:02.521 --> 30:05.781 the brain to take over if some parts are damaged. 30:05.779 --> 30:10.119 A second consideration is the brain is extremely fast. 30:10.119 --> 30:16.009 Your computer works on wires and electricity but your brain 30:16.011 --> 30:20.381 uses tissue and tissue is extremely slow. 30:20.380 --> 30:24.220 The paradox then is how do you create such a fast computer with 30:24.216 --> 30:26.646 such slow stuff? And you can't. 30:26.650 --> 30:29.940 If the brain was wired up like a personal computer, 30:29.935 --> 30:33.545 it would take you four hours to recognize a face but, 30:33.549 --> 30:36.089 in fact, we could do things extremely quickly. 30:36.089 --> 30:40.369 So, the question then is how is the brain wired up? 30:40.369 --> 30:42.689 And the answer is, unlike manys, 30:42.694 --> 30:46.824 unlike commercially generated computers, the brain works 30:46.819 --> 30:51.549 through parallel processing, massively parallel distributed 30:51.548 --> 30:54.198 processing. There's a whole lot of research 30:54.203 --> 30:56.763 and this is research, some of which takes place 30:56.761 --> 31:00.101 outside psychology departments and in engineering departments 31:00.097 --> 31:02.207 and computer science departments, 31:02.210 --> 31:07.920 trying to figure out how a computer can do the same things 31:07.917 --> 31:11.537 brains can do. And one way people do this is 31:11.541 --> 31:15.931 they take a hint from nature and they try to construct massively 31:15.934 --> 31:19.494 distributed networks to do aspects of reasoning. 31:19.490 --> 31:23.180 So, there's a very simple computational network. 31:23.180 --> 31:26.970 That is interesting because it kind of looks to some extent 31:26.965 --> 31:30.745 like the way neurons look and this is often known as neural 31:30.751 --> 31:33.701 networks. And people who study this often 31:33.704 --> 31:37.714 claim to be studying neural network modeling to try to build 31:37.710 --> 31:40.970 smart machines by modeling them after brains. 31:40.970 --> 31:44.610 And in the last 20 years or so, this has been a huge and 31:44.612 --> 31:48.262 vibrant area of study where people are trying to wire up 31:48.255 --> 31:52.425 machines that can do brain-like things from components that look 31:52.428 --> 31:56.798 a lot like neurons and are wired up together as neurons are. 31:56.799 --> 32:00.929 One consideration in all of this is that this is a very 32:00.934 --> 32:04.614 young field and nobody knows how to do it yet. 32:04.609 --> 32:09.009 There is no machine yet that can recognize faces or 32:09.014 --> 32:14.304 understand sentences at the level of a two-year-old human. 32:14.299 --> 32:16.819 There is no machine yet that can do just about anything 32:16.818 --> 32:18.588 people can do in an interesting way. 32:18.589 --> 32:20.849 And this is, in part, because the human 32:20.851 --> 32:24.121 brain is wired up in an extraordinarily more complicated 32:24.123 --> 32:26.923 way than any sort of simple neural network. 32:26.920 --> 32:30.860 This is a sort of schematic diagram – you're not 32:30.863 --> 32:35.453 responsible for this – of parts of the visual cortex, 32:35.450 --> 32:39.370 and the thing to realize about this is it's extraordinarily 32:39.371 --> 32:42.891 simplified. So, the brain is a complicated 32:42.886 --> 32:45.906 system. Now, so, we've talked a little 32:45.905 --> 32:50.685 bit about the basic building blocks of the brain – neurons. 32:50.690 --> 32:54.020 We've then talked about how neurons can communicate to one 32:54.016 --> 32:57.396 another; then, turned to how neurons are 32:57.396 --> 32:59.106 wired up together. 32:59.109 --> 33:02.109 Now let's talk a little bit about different parts of the 33:02.113 --> 33:04.553 brain. Now, there's some things you 33:04.548 --> 33:07.258 don't actually need your brain to do. 33:07.259 --> 33:10.719 The study of what you don't need your brain to do has often 33:10.721 --> 33:13.591 drawn upon this weird methodology where--This was 33:13.585 --> 33:16.925 actually done in France a lot where they would decapitate 33:16.927 --> 33:20.087 people and when--After they decapitated people, 33:20.089 --> 33:23.569 psychologists would rush to the body of the headless person and 33:23.572 --> 33:26.552 sort of just test out reflexes and stuff like that. 33:26.549 --> 33:29.439 It's kind of gruesome but we know there are some things you 33:29.443 --> 33:30.843 don't need your brain for. 33:30.839 --> 33:34.819 You don't need your brain for newborn sucking, 33:34.816 --> 33:38.436 limb flexation in withdrawal from pain. 33:38.440 --> 33:41.870 Your limbs will pull back even if your head is gone. 33:41.869 --> 33:45.249 Erection of the penis can be done without a brain. 33:45.250 --> 33:47.130 Vomiting also is done without a brain. 33:47.126 --> 33:51.006 Oh. I need a volunteer. 33:51.010 --> 33:53.310 Very simple. This will not involve any 33:53.312 --> 33:54.942 of--excellent--any of the above. 33:54.940 --> 33:57.970 Could you stand up just--Okay. 33:57.970 --> 33:59.800 This is a new shirt so I want to stay away. 33:59.800 --> 34:03.030 Just--No. This is--If you'll hold out 34:03.026 --> 34:05.496 your hand and--one hand flat. 34:05.504 --> 34:07.644 Excellent. That's the textbook, 34:07.639 --> 34:10.369 5th edition. Now. 34:10.370 --> 34:13.420 Perfect. What you'll notice is--Thank 34:13.423 --> 34:16.103 you very much. What you'll notice is this hit 34:16.099 --> 34:17.909 and this hand went back up. 34:17.909 --> 34:21.029 This is something automatic, instinctive, 34:21.028 --> 34:23.678 and does not require your brain. 34:23.679 --> 34:26.149 So your brain isn't needed for everything. 34:26.150 --> 34:28.310 What does your brain do? 34:28.309 --> 34:31.489 Well, some things that your brain does involve very 34:31.486 --> 34:33.516 low-level internal structures. 34:33.519 --> 34:36.969 And these are called subcortical structures because 34:36.974 --> 34:38.844 they're below the cortex. 34:38.840 --> 34:40.910 They're underneath the cortex. 34:40.909 --> 34:43.919 So, for instance, what we have here is a diagram 34:43.919 --> 34:46.589 of the brain. The way to read this diagram is 34:46.594 --> 34:49.584 it's as if it were my brain and I am facing this way. 34:49.579 --> 34:55.399 My head gets cut in half down here and then you could see the 34:55.403 --> 34:58.313 brain. So, this is the front over here. 34:58.310 --> 35:02.420 That's the back. Some key parts are illustrated 35:02.418 --> 35:03.988 here. The medulla, 35:03.993 --> 35:08.103 for instance, is responsible for heart rate 35:08.101 --> 35:11.771 and respiration. It's very deep within the brain 35:11.770 --> 35:15.100 and if it gets damaged you could--you are likely to die. 35:15.099 --> 35:19.829 The cerebellum is responsible for body balance and muscular 35:19.827 --> 35:22.087 coordination. And to give you, 35:22.086 --> 35:25.446 again, a feeling for the complexity of these systems, 35:25.454 --> 35:28.504 the cerebellum contains approximately 30 billion 35:28.498 --> 35:32.168 neurons. The hypothalamus is responsible 35:32.167 --> 35:35.087 here for feeding, hunger, thirst, 35:35.086 --> 35:37.636 and to some extent sleep. 35:37.639 --> 35:41.889 And here is the same brain parts in close-up. 35:41.889 --> 35:46.999 Now, all of these parts of the brains are essential and many of 35:47.000 --> 35:50.870 them are implicated in interesting psychological 35:50.874 --> 35:55.164 processes but where the action is is the cortex. 35:55.160 --> 35:57.670 Isn't this beautiful? 35:57.670 --> 36:01.890 The cortex is the outer layer and the outer layer is all 36:01.886 --> 36:04.256 crumpled up. Do you ever wonder why your 36:04.260 --> 36:05.320 brain looks wrinkled? 36:05.320 --> 36:08.670 That's because it's all crumpled. 36:08.670 --> 36:12.980 If you took out somebody's cortex and flattened it out, 36:12.976 --> 36:17.356 it would be two feet square, sort of like a nice--like a 36:17.362 --> 36:21.522 rug. And the cortex is where all the 36:21.517 --> 36:24.237 neat stuff takes place. 36:24.239 --> 36:27.609 Fish don't have any of that, so no offense to fish but 36:27.612 --> 36:30.542 it's--fish don't have much of a mental life. 36:30.539 --> 36:34.379 Reptiles and birds have a little bit about it--of it--and 36:34.380 --> 36:37.740 primates have a lot and humans have a real lot. 36:37.739 --> 36:41.689 Eighty percent of the volume of our brain, about, 36:41.692 --> 36:46.732 is cortex. And the cortex can be broken up 36:46.730 --> 36:50.780 into different parts or lobes. 36:50.780 --> 36:53.570 There is the--And, again, this is facing in 36:53.572 --> 36:56.182 profile forward. There is the frontal lobe, 36:56.176 --> 36:57.146 easy to remember. 36:57.150 --> 37:01.330 This part in front, the parietal lobe, 37:01.334 --> 37:06.314 the occipital lobe, and the temporal lobe. 37:06.309 --> 37:09.939 And one theme we're going to return to is--this is half the 37:09.939 --> 37:12.369 brain. This is, in fact, 37:12.374 --> 37:15.564 the left half of the brain. 37:15.559 --> 37:17.679 On the other half, the right half, 37:17.676 --> 37:20.876 everything's duplicated with some slight and subtle 37:20.883 --> 37:24.553 differences. What's really weird--One really 37:24.551 --> 37:29.921 weird finding about these lobes is that they include topological 37:29.918 --> 37:33.028 maps. They include maps of your body. 37:33.030 --> 37:36.780 There is a cartoon which actually illustrates a classic 37:36.778 --> 37:41.148 experiment by some physiologists who for some reason had a dog's 37:41.151 --> 37:45.181 brain opened up and started shocking different parts of the 37:45.177 --> 37:47.457 brain. You could do brain surgery 37:47.463 --> 37:50.713 while fully conscious because the brain itself has no sense 37:50.705 --> 37:53.015 organs to it. And it turns out that the 37:53.021 --> 37:56.321 dog--When they zapped part of its brain, its leg would kick 37:56.318 --> 37:57.968 up. And it took Dr. 37:57.973 --> 38:02.703 Penfield at McGill University to do the same thing with 38:02.704 --> 38:04.834 people. So, they were doing some brain 38:04.833 --> 38:06.613 surgery. He had a little electrical 38:06.609 --> 38:09.569 thing just on--I don't know how he thought to do this. 38:09.570 --> 38:11.970 He started zapping it and "boom." 38:11.969 --> 38:14.749 The person--Parts of their body would move. 38:14.750 --> 38:17.810 More than that, when he zapped other parts of 38:17.810 --> 38:21.010 the brain, people would claim to see colors. 38:21.010 --> 38:22.840 And he zapped other parts of the brain; 38:22.840 --> 38:25.390 people would claim to hear sounds; 38:25.389 --> 38:29.839 and other parts of the brain, people would claim to 38:29.839 --> 38:31.529 experience touch. 38:31.530 --> 38:34.880 And through his research and other research, 38:34.882 --> 38:39.562 it was found that there are maps in the brain of the body. 38:39.559 --> 38:42.819 There is a map in the motor part of the brain, 38:42.817 --> 38:46.217 the motor cortex, of the sort up on the left and 38:46.219 --> 38:50.629 the sensory cortex of the sort that you could see on the right 38:50.634 --> 38:54.914 and if you--and you could tell what's what by opening up the 38:54.905 --> 38:58.885 brain and shocking different parts and those parts would 38:58.886 --> 39:04.166 correspond to the parts of the body shown in the diagram there. 39:04.170 --> 39:07.760 Now, two things to notice about these maps. 39:07.760 --> 39:11.140 The first is they're topographical and what this 39:11.140 --> 39:14.950 means is that if two parts of the--two parts are close 39:14.952 --> 39:18.702 together on the body, they'll be close together on 39:18.702 --> 39:22.412 the brain. So, your tongue is closer to 39:22.411 --> 39:27.141 your jaw than it is to your hip in the body; 39:27.139 --> 39:32.419 so too in both the motor cortex and the somatosensory cortex. 39:32.420 --> 39:35.710 Also, you'll notice that the size of the body part 39:35.709 --> 39:39.599 represented in the brain does not correspond to the size of 39:39.603 --> 39:42.023 the body part in the real world. 39:42.019 --> 39:46.789 Rather, what determines the size in the brain is the extent 39:46.792 --> 39:51.482 to which either they have motor command over it or sensory 39:51.482 --> 39:53.772 control. So, there's a whole lot of 39:53.766 --> 39:55.156 sensory organs, for instance, 39:55.163 --> 39:58.583 focused along your tongue, and that's why that's so big, 39:58.575 --> 40:02.505 and an enormous amount on your face but your shoulder isn't 40:02.505 --> 40:05.685 even--doesn't even make it on there because, 40:05.690 --> 40:07.820 although your shoulder might be bigger than your tongue, 40:07.823 --> 40:08.913 there's not much going on. 40:08.909 --> 40:13.829 In fact, if you draw a diagram of a person, what their body is 40:13.832 --> 40:17.952 corresponding to the amount of somatosensory cortex, 40:17.947 --> 40:20.527 you get something like that. 40:20.530 --> 40:22.320 That's your sensory body. 40:22.320 --> 40:28.590 40:28.590 --> 40:32.350 Now, so, you have these maps in your head but the thing to 40:32.351 --> 40:35.851 realize is--And these maps are part of your cortex, 40:35.849 --> 40:40.489 but the things to realize is that's an important part of what 40:40.489 --> 40:45.129 goes on in your brain but less than one quarter of the cortex 40:45.128 --> 40:48.528 contains these maps or projection areas. 40:48.530 --> 40:53.080 The rest is involved in language and reasoning and moral 40:53.076 --> 40:54.726 thought and so on. 40:54.730 --> 40:57.370 And, in fact, the proportion as you go from 40:57.366 --> 41:00.566 rat, cat, and monkey, humans--less and less of it is 41:00.568 --> 41:04.078 devoted to projection and there is more and more to other 41:04.083 --> 41:07.903 things. So, how do we figure out what 41:07.902 --> 41:11.322 the other parts of the brain do? 41:11.320 --> 41:12.980 Well, there's all sorts of methods. 41:12.980 --> 41:18.240 Typically, these are recent imaging methods like CAT scan 41:18.239 --> 41:22.469 and PET scan and fMRI which, as I said before, 41:22.465 --> 41:25.935 show parts of your brain at work. 41:25.940 --> 41:30.960 If you want to know which part of your brain is responsible for 41:30.964 --> 41:35.834 language, you could put somebody into a scanner and have them 41:35.826 --> 41:40.116 exposed to language or do a linguistic task or talk or 41:40.121 --> 41:45.471 something and then see what parts of their brain are active. 41:45.469 --> 41:49.839 Another way to explore what the brain does is to consider what 41:49.838 --> 41:54.348 happens to people when very bad things happen to their brain. 41:54.349 --> 41:58.159 And these bad things could happen through lesions, 41:58.156 --> 42:00.556 through tumors, through strokes, 42:00.564 --> 42:03.234 through injury. For the most part, 42:03.229 --> 42:06.069 neuropsychologists don't like helmet laws. 42:06.070 --> 42:09.260 Neuropsychologists love when motorcyclists drive without 42:09.259 --> 42:12.799 helmets because through their horrible accidents we gain great 42:12.796 --> 42:14.996 insights into how the brain works. 42:15.000 --> 42:18.060 And the logic is if you find somebody--Crudely, 42:18.064 --> 42:21.864 if you find somebody with damage to this part of the brain 42:21.862 --> 42:26.262 right here and that person can't recognize faces for instance, 42:26.260 --> 42:29.710 there's some reason to believe that this part of the brain is 42:29.713 --> 42:31.443 related to face recognition. 42:31.440 --> 42:36.190 And so, from the study of brain damage and the study of--we can 42:36.191 --> 42:41.251 gain some understanding of what different parts of the brain do. 42:41.250 --> 42:45.860 And so, people study brain damages--brain damage that 42:45.858 --> 42:49.668 implicates motor control such as apraxia. 42:49.670 --> 42:53.350 And what's interesting about apraxia is it's not paralysis. 42:53.349 --> 42:57.009 Somebody with apraxia can move, do simple movements just fine 42:57.007 --> 42:59.687 but they can't coordinate their movements. 42:59.690 --> 43:02.950 They can't do something like wave goodbye or light a 43:02.952 --> 43:05.582 cigarette. There is agnosia and agnosia is 43:05.579 --> 43:09.299 a disorder which isn't blindness because the person could still 43:09.300 --> 43:10.620 see perfectly well. 43:10.619 --> 43:15.489 Their eyes are intact but rather what happens in agnosia 43:15.485 --> 43:20.345 is they lose the ability to recognize certain things. 43:20.349 --> 43:23.419 Sometimes this is described as psychic blindness. 43:23.420 --> 43:26.990 And so, they may get visual agnosia and lose the ability to 43:26.989 --> 43:28.219 recognize objects. 43:28.219 --> 43:33.399 They may get prosopagnosia and lose the ability to recognize 43:33.397 --> 43:36.607 faces. There are disorders of sensory 43:36.606 --> 43:39.276 neglect, some famous disorders. 43:39.280 --> 43:41.950 Again, it's not paralysis, it's not blindness, 43:41.947 --> 43:45.327 but due to certain parts of your--of damaged parts of your 43:45.327 --> 43:46.967 brain, you might lose, 43:46.972 --> 43:49.852 for instance, the idea that there's a left 43:49.850 --> 43:53.290 side of your body or a left side of the world. 43:53.289 --> 43:55.999 And these cases are so interesting I want to devote 43:56.003 --> 43:59.043 some chunk to a class in the next few weeks to discussing 43:59.041 --> 44:02.531 them. There are disorders of language 44:02.533 --> 44:06.613 like aphasia. The classic case was discovered 44:06.605 --> 44:08.615 by Paul Broca in 1861. 44:08.619 --> 44:13.589 A patient who had damage to part of his brain and can only 44:13.591 --> 44:15.511 say one word, "tan," 44:15.510 --> 44:19.360 and the person would say, "tan, tan, tan, 44:19.364 --> 44:22.934 tan," and everything else was gone. 44:22.929 --> 44:26.259 There's other disorders of language such as receptive 44:26.264 --> 44:29.924 aphasia where the person could speak very fluently but the 44:29.920 --> 44:33.700 words don't make any sense and they can't understand anybody 44:33.704 --> 44:35.924 else. Other disorders that we'll 44:35.918 --> 44:38.528 discuss later on include acquired psychopathy, 44:38.527 --> 44:40.787 where damage to parts of your brain, 44:40.789 --> 44:44.039 particularly related to the frontal lobes, 44:44.042 --> 44:48.012 rob you of the ability to tell right from wrong. 44:48.010 --> 44:51.130 The final--I want to end--We're talking about neurons, 44:51.125 --> 44:54.085 connection between neurons, how neurons are wired up, 44:54.089 --> 44:56.759 the parts of the brain, what the different parts do. 44:56.760 --> 45:01.060 I want to end by talking about the two halves of the brain and 45:01.057 --> 45:04.507 ask the question, "How many minds do you have?" 45:04.510 --> 45:08.070 Now, if you look at the brain--If you took the brain out 45:08.072 --> 45:10.342 and held it up, it would look pretty 45:10.339 --> 45:12.929 symmetrical, but it actually is not. 45:12.929 --> 45:16.979 There are actual differences between the right hemisphere and 45:16.983 --> 45:18.473 the left hemisphere. 45:18.469 --> 45:23.969 How many people here are right-handed? 45:23.969 --> 45:28.369 How many people here are left-handed? 45:28.369 --> 45:31.459 How many people here are sort of complicated, 45:31.461 --> 45:34.481 ambidextrous, don't know, "bit of the right, 45:34.483 --> 45:36.173 bit of left" people? 45:36.170 --> 45:38.500 Okay. Those of you who are 45:38.500 --> 45:41.980 right-handed, which comprises about nine out 45:41.983 --> 45:45.223 of ten people, have language in your left 45:45.223 --> 45:47.183 hemisphere. And, in fact, 45:47.181 --> 45:50.391 we're going to be talking about right-handed people for the most 45:50.387 --> 45:53.437 part, making generalizations in what I'll talk about now. 45:53.440 --> 45:56.230 Those of you who are left-handed are more 45:56.232 --> 45:58.672 complicated. Some of you have language in 45:58.669 --> 46:01.329 your right hemisphere, some in your left hemisphere, 46:01.328 --> 46:02.578 some God knows where. 46:02.580 --> 46:03.700 It's complicated. 46:03.699 --> 46:08.019 Now, the idea is that some things are duplicated. 46:08.019 --> 46:11.519 So, if you were to lose half your brain, the other half can 46:11.520 --> 46:14.840 actually do a lot but some things are more prevalent and 46:14.839 --> 46:18.339 more powerful in one part of the brain than the other. 46:18.340 --> 46:21.150 And I want to show you a brief film clip from "Scientific 46:21.148 --> 46:23.808 American" that illustrates the differences between the 46:23.807 --> 46:26.007 hemispheres, but before doing that, 46:26.011 --> 46:28.751 I want to provide some introductory facts. 46:28.750 --> 46:30.910 Some functions are lateralized. 46:30.909 --> 46:32.519 So, typically, language in the left. 46:32.519 --> 46:36.209 Again, this is a right-handed centric thing but if you're 46:36.207 --> 46:40.087 right-handed – language on the left, math and music on the 46:40.091 --> 46:42.301 right. There is a crossover and this 46:42.302 --> 46:45.732 is important when we think about the studies that will follow but 46:45.727 --> 46:49.147 the crossover is that everything you see in the left visual field 46:49.152 --> 46:51.402 goes to the right side of your brain; 46:51.400 --> 46:54.880 everything in the right visual field goes to the left side of 46:54.877 --> 46:58.237 the brain, and similarly, there's a crossover in action. 46:58.239 --> 47:00.289 So, your right hemisphere controls the left side of the 47:00.293 --> 47:02.273 body. Your left hemisphere controls 47:02.274 --> 47:03.934 the right side of the body. 47:03.929 --> 47:09.369 Now, finally, the two halves are connected. 47:09.369 --> 47:16.679 They're connected by this huge web called the corpus callosum. 47:16.679 --> 47:21.349 And I'm just going to skip this because the movie illustration 47:21.354 --> 47:23.734 will go through some of this. 47:23.730 --> 47:26.500 47:26.500 --> 47:30.510 This illustrates certain themes that are discussed in detail in 47:30.506 --> 47:33.726 the Gray book, concerning the lateralization 47:33.725 --> 47:37.565 of different parts of different mental capacities, 47:37.570 --> 47:39.970 some in the left hemisphere, some in the right hemisphere. 47:39.969 --> 47:45.179 But it also serves as a useful methodological development, 47:45.183 --> 47:50.953 which is a nice illustration as to how looking at people who are 47:50.946 --> 47:54.636 incredibly unusual, such as this man who had his 47:54.641 --> 47:57.481 brain bisected so his left hemisphere and his right 47:57.483 --> 48:00.893 hemisphere don't communicate with one another--how looking at 48:00.893 --> 48:03.233 such people, such extreme cases, 48:03.231 --> 48:07.271 can provide us with some understanding of how we normally 48:07.271 --> 48:09.231 do things. And this, again, 48:09.225 --> 48:12.395 is a theme we'll return to throughout the course. 48:12.400 --> 48:16.630 This is generally the general introduction of the brain that I 48:16.632 --> 48:19.632 wanted to provide, giving the framework for what 48:19.631 --> 48:23.021 I'll be talking about later on throughout the course so that I 48:23.020 --> 48:26.520 might later on make reference to neurons or neurotransmitters or 48:26.520 --> 48:29.350 the cortex or the left hemisphere and you'll sort of 48:29.354 --> 48:32.084 have the background to understand what I'm talking 48:32.076 --> 48:35.916 about. But I want to end this first 48:35.917 --> 48:40.537 real class with a bit of humility as to what 48:40.535 --> 48:44.505 psychologists know and don't know. 48:44.510 --> 48:47.400 So, the idea behind a lot of psychology – particularly a 48:47.396 --> 48:50.076 lot of neuroscience and cognitive psychology – is to 48:50.080 --> 48:52.460 treat the mind as an information processor, 48:52.460 --> 48:55.150 as an elaborate computer. 48:55.150 --> 49:00.300 And so, we study different problems like recognizing faces 49:00.297 --> 49:03.907 or language or motor control or logic. 49:03.909 --> 49:07.229 The strategy then often is to figure out how, 49:07.226 --> 49:11.896 what sort of program can solve these problems and then we go on 49:11.900 --> 49:15.370 to ask, "How could this program be 49:15.367 --> 49:19.117 instantiated in the physical brain?" 49:19.119 --> 49:22.919 So, we would solve--We study people much as we'd study a 49:22.920 --> 49:26.030 computer from an alien planet or something. 49:26.030 --> 49:30.580 And I think--This strategy is one I'm very enthusiastic about 49:30.581 --> 49:34.831 but there still remains what's sometimes called the "hard 49:34.829 --> 49:38.849 problem" of consciousness and this involves subjective 49:38.850 --> 49:41.940 experience. What's it like? 49:41.940 --> 49:46.410 So, my computer can play chess. 49:46.409 --> 49:50.029 My computer can recognize numbers. 49:50.030 --> 49:53.490 It can do math. And maybe it does it kind of 49:53.493 --> 49:58.173 the same way that I do it but my computer doesn't have feelings 49:58.174 --> 49:59.764 in the same sense. 49:59.760 --> 50:03.010 These are two classic illustrations. 50:03.010 --> 50:05.090 This is from a very old "Star Trek" episode. 50:05.090 --> 50:06.750 It illustrates angst. 50:06.750 --> 50:09.590 I think a starship's about to go into the sun or something. 50:09.590 --> 50:14.660 And that's my older kid, Max, who's happy. 50:14.659 --> 50:18.019 And so the question is, "How does a thing like that 50:18.018 --> 50:21.778 give rise to consciousness and subjective experience?" 50:21.780 --> 50:23.370 And this is a deep puzzle. 50:23.369 --> 50:27.109 And although some psychologists and philosophers think they've 50:27.113 --> 50:30.123 solved it, most of us are a lot more skeptical. 50:30.119 --> 50:34.019 Most of us think we have so far to go before we can answer 50:34.023 --> 50:36.423 questions like Huxley's question. 50:36.420 --> 50:38.950 Huxley points out, "How it is that anything so 50:38.954 --> 50:42.004 remarkable as a state of consciousness comes about as a 50:41.996 --> 50:44.246 result of irritating nervous tissue, 50:44.250 --> 50:47.490 is just as unaccountable as the appearance of the Djinn…" – 50:47.487 --> 50:50.147 of the genie – "…when Aladdin rubs his lamp." 50:50.150 --> 50:53.690 It seems like magic that a fleshy lump of gray, 50:53.691 --> 50:57.541 disgusting meat can give rise to these feelings. 50:57.539 --> 51:00.809 The second bit of humility we'll end the class on is I am 51:00.808 --> 51:03.028 presenting here, and I'll be presenting 51:03.027 --> 51:06.677 throughout this semester, what you can call a mechanistic 51:06.676 --> 51:08.376 conception of mental life. 51:08.380 --> 51:10.390 I'm not going to be talking about how beautiful it is and 51:10.391 --> 51:12.081 how wonderful it is and how mysterious it is. 51:12.079 --> 51:14.429 Rather, I'm going to be trying to explain it. 51:14.429 --> 51:17.649 I'm going to be trying to explain fundamental aspects of 51:17.654 --> 51:21.294 ourselves including questions like how do we make decisions, 51:21.289 --> 51:25.159 why do we love our children, what happens when we fall in 51:25.164 --> 51:29.404 love, and so on. Now, you might find this sort 51:29.403 --> 51:33.433 of project in the end to be repellant. 51:33.429 --> 51:38.409 You might worry about how this, well, this meshes with humanist 51:38.407 --> 51:39.907 values. For instance, 51:39.905 --> 51:43.485 when we deal with one another in a legal and a moral setting, 51:43.486 --> 51:46.646 we think in terms of free will and responsibility. 51:46.650 --> 51:50.540 If we're driving and you cut me off, you chose to do that. 51:50.540 --> 51:52.790 It reflects badly on you. 51:52.789 --> 51:56.309 If you save a life at risk to your own, you're--you deserve 51:56.313 --> 51:59.893 praise. You did something wonderful. 51:59.889 --> 52:03.409 It might be hard to mesh this with the conception in which all 52:03.405 --> 52:06.105 actions are the result of neurochemical physical 52:06.113 --> 52:08.993 processes. It might also be hard to mesh a 52:08.986 --> 52:12.716 notion such as the purported intrinsic value of people. 52:12.719 --> 52:15.699 And finally, it might be hard to mesh the 52:15.696 --> 52:20.156 mechanistic notion of the mind with the idea that people have 52:20.161 --> 52:23.281 spiritual value. Faced with this tension, 52:23.277 --> 52:25.377 there are three possibilities. 52:25.380 --> 52:28.510 You might choose to reject the scientific conception of the 52:28.512 --> 52:30.582 mind. Many people do. 52:30.579 --> 52:33.799 You may choose to embrace dualism, reject the idea that 52:33.801 --> 52:37.081 the brain is responsible for mental life, and reject the 52:37.083 --> 52:39.413 promise of a scientific psychology. 52:39.409 --> 52:42.449 Alternatively, you might choose to embrace the 52:42.452 --> 52:46.512 scientific worldview and reject all these humanist values. 52:46.510 --> 52:49.910 And there are some philosophers and psychologists who do just 52:49.912 --> 52:53.432 that, who claim that free will and responsibility and spiritual 52:53.428 --> 52:56.148 value and intrinsic value are all illusions; 52:56.150 --> 53:00.640 they're pre-scientific notions that get washed away in modern 53:00.635 --> 53:03.995 science or you could try to reconcile them. 53:04.000 --> 53:08.300 You could try to figure out how to mesh your scientific view of 53:08.296 --> 53:11.896 the mind with these humanist values you might want to 53:11.899 --> 53:13.859 preserve. And this is an issue which 53:13.857 --> 53:15.807 we're going to return to throughout the course. 53:15.810 --> 53:18.000 Okay. I'll see you on Wednesday.