WEBVTT - Ep17 "What is consciousness?" 0:00:04.640 --> 0:00:08.280 How do your billions of tiny brain cells with their 0:00:08.320 --> 0:00:14.159 electrical spikes build consciousness? And why is your laptop, with 0:00:14.240 --> 0:00:19.280 its billions of parts and tiny electrical signals, presumably not conscious? 0:00:19.920 --> 0:00:23.600 Could other large systems like a city be conscious? And 0:00:23.640 --> 0:00:25.840 what does any of this have to do with ant 0:00:25.880 --> 0:00:30.080 hills or bluebirds or your memory of your first kiss? 0:00:33.920 --> 0:00:37.000 Welcome to Inner Cosmos with me David Eagleman. I'm a 0:00:37.000 --> 0:00:40.920 neuroscientist and an author at Stanford University, and I've spent 0:00:40.960 --> 0:00:45.200 my whole career studying the intersection between how the brain 0:00:45.280 --> 0:00:49.479 works and how we experience life. And there's hardly a 0:00:49.479 --> 0:00:55.920 better example of this intersection than consciousness. Your feeling of 0:00:55.960 --> 0:01:00.240 being aware of your surroundings and your own existence, your 0:01:00.280 --> 0:01:05.880 ability to experience and feel things. This somehow emerges from 0:01:05.920 --> 0:01:10.480 the activity of our brains, and it is our experience 0:01:10.520 --> 0:01:14.880 of life. So today we're going to dive deep into 0:01:14.959 --> 0:01:20.000 a big question, possibly the central question of neurobiology. What 0:01:20.640 --> 0:01:24.679 is consciousness. We'll talk about how we can define it, 0:01:24.920 --> 0:01:28.040 why it's a challenge for our science to capture it, 0:01:28.560 --> 0:01:32.399 and whether other things could be conscious. So think back 0:01:32.440 --> 0:01:36.600 to your first kiss. The memory of it pops back 0:01:36.640 --> 0:01:40.360 into your head in an instant, But where was that 0:01:40.600 --> 0:01:45.160 image before you became conscious of it, that feeling, the 0:01:45.319 --> 0:01:48.320 name of the person, How is it represented in your 0:01:48.360 --> 0:01:52.800 brain before and after I ask you to think about it. 0:01:53.040 --> 0:01:56.760 What's the difference between those two states? In other words, 0:01:56.800 --> 0:02:04.560 what events in the brain constitute awareness or consciousness. I 0:02:04.640 --> 0:02:07.640 made an earlier episode about all the things going on 0:02:07.720 --> 0:02:12.440 in your head unconsciously without any access or awareness on 0:02:12.480 --> 0:02:16.720 your part, and the upshot there was that at any moment, 0:02:16.880 --> 0:02:20.320 there's an enormous amount of activity going on in your brain, 0:02:21.040 --> 0:02:25.639 one hundred billion cells having little electrical spikes tens or 0:02:25.720 --> 0:02:29.680 hundreds of times per second, and you are not consciously 0:02:29.720 --> 0:02:33.000 aware of almost any of that activity in your brain. 0:02:33.760 --> 0:02:38.280 But a tiny, tiny bit of that activity is conscious. 0:02:39.720 --> 0:02:42.560 And so for this episode we're turning to that tiny 0:02:42.680 --> 0:02:46.280 tiny bit and the question of what is different about 0:02:46.720 --> 0:02:49.680 that activity than all the other activity in your brain, 0:02:50.160 --> 0:02:52.560 and why it's such a challenge for us to figure 0:02:52.560 --> 0:02:56.840 out how to translate that activity in your brain into 0:02:57.000 --> 0:03:03.240 your private, colorful experience of the world. The explanation of 0:03:03.320 --> 0:03:08.280 consciousness is one of the major unsolved problems of modern neuroscience, 0:03:08.400 --> 0:03:13.520 and possibly the most important. So first, what is consciousness. 0:03:13.760 --> 0:03:17.160 Defining it is the first step to the problem. So 0:03:17.280 --> 0:03:19.440 there are lots of ways to try to wrap our 0:03:19.560 --> 0:03:22.040 arms around it. But the definition that I think will 0:03:22.040 --> 0:03:26.800 get us started the fastest is to say consciousness is 0:03:26.840 --> 0:03:29.480 the thing that flickers to life when you wake up 0:03:29.520 --> 0:03:32.920 in the morning. I mean, think about how wacky this is. 0:03:33.000 --> 0:03:36.200 You have the same brain the moment before you wake 0:03:36.280 --> 0:03:39.400 up in the moment after, but something just changed a 0:03:39.440 --> 0:03:42.200 little bit about the activity, the way the signals are 0:03:42.240 --> 0:03:46.600 moving around, and suddenly you're conscious. Whereas a moment ago 0:03:47.040 --> 0:03:49.680 you were just lying there like a sack of potatoes. 0:03:50.120 --> 0:03:52.920 You had the same brain, but you weren't aware of anything. 0:03:53.680 --> 0:03:57.000 But now your brain cells start to run a slightly 0:03:57.040 --> 0:04:01.920 different algorithm, and suddenly you're aware of your existence, of 0:04:01.960 --> 0:04:06.800 your name, of your history, and your bedroom and the 0:04:06.840 --> 0:04:09.920 smell of coffee and the feel of your sheets and 0:04:10.000 --> 0:04:11.040 the details of. 0:04:11.000 --> 0:04:11.960 The room around you. 0:04:12.200 --> 0:04:17.680 Now, weirdly, what you're experiencing is a private experience. It's 0:04:17.680 --> 0:04:22.480 what we call a subjective experience. It's not objective, which 0:04:22.480 --> 0:04:26.480 is something we can measure and agree on a shared reality. Instead, 0:04:26.600 --> 0:04:30.520 only you are experiencing it. So if there's someone else 0:04:30.560 --> 0:04:32.680 in the bedroom when you wake up and that person 0:04:32.800 --> 0:04:36.120 is looking around, there are different things going on in 0:04:36.160 --> 0:04:42.119 that head, different thoughts, different feelings, a different subjective experience. Okay, 0:04:42.160 --> 0:04:45.359 so imagine you're there and you roll over and you 0:04:45.400 --> 0:04:47.559 look at a painting on your wall and you see 0:04:47.560 --> 0:04:53.240 the colors. Now, what's happening inside your brain is that 0:04:53.360 --> 0:04:57.680 different wavelengths of light are bouncing off the painting and 0:04:57.680 --> 0:05:02.600 they're activating particular color photoreceptors in the back of your eyes, 0:05:04.480 --> 0:05:07.640 which sends signals back to your brain through the optic nerve, 0:05:08.200 --> 0:05:12.440 and in the brain, cells in the visual cortex start activating. 0:05:13.040 --> 0:05:15.960 And if you had a magical microscope by which you 0:05:16.000 --> 0:05:18.560 could view what was happening in the brain, you'd see 0:05:18.560 --> 0:05:22.359 that you have a vast pattern of cells in the 0:05:22.400 --> 0:05:25.480 back of the brain that activate when you look at 0:05:25.720 --> 0:05:29.200 one painting color, and a different pattern of cells that 0:05:29.240 --> 0:05:32.320 activate when you look at a different color. But the 0:05:32.440 --> 0:05:36.280 question is why do you perceive the red in the 0:05:36.279 --> 0:05:41.240 painting as red? There's just a particular wavelength of light 0:05:41.440 --> 0:05:45.360 associated with your private subjective experience of seeing red. 0:05:45.760 --> 0:05:48.120 But the redness is something made. 0:05:47.920 --> 0:05:50.479 Up by the brain and could just as easily be 0:05:50.600 --> 0:05:54.039 perceived by you as blue or green or anything else. 0:05:54.920 --> 0:05:58.680 So why does this particular pattern of cells equally a 0:05:58.760 --> 0:06:03.920 particular color. These are called qualia. Qualia are the features 0:06:03.960 --> 0:06:08.120 of our experience, the internal experiences that are associated with 0:06:08.440 --> 0:06:12.359 conscious states. The redness of red in this case, or 0:06:12.440 --> 0:06:16.520 the sweetness of sugar, or the pain of a headache, 0:06:16.760 --> 0:06:21.000 these are called qualia. Now, these are irreducible, which means 0:06:21.000 --> 0:06:24.960 they can't be described in terms of something else. And 0:06:25.000 --> 0:06:28.040 by the way, they're also ineffable, which means they can't 0:06:28.080 --> 0:06:32.120 be fully explained or described in words like if I 0:06:32.200 --> 0:06:35.080 ask you, what does an avocado taste like, how are 0:06:35.120 --> 0:06:37.000 you going to answer that. Let's say that I tell 0:06:37.040 --> 0:06:39.480 you I've never eaten an avocado, and I really want 0:06:39.560 --> 0:06:42.039 you to tell me what that experience is. It's not 0:06:42.200 --> 0:06:45.719 something that you can directly transmit to me, because it's 0:06:45.839 --> 0:06:50.000 an experience that's private to you and generally cannot be 0:06:50.120 --> 0:06:54.200 reduced to words. The last piece of the foundation that 0:06:54.240 --> 0:06:56.800 we need is that when you look in the brain, 0:06:57.680 --> 0:07:00.640 it's all just neural signals going on, and all those 0:07:00.680 --> 0:07:03.719 signals look exactly the same. So if I opened up 0:07:03.760 --> 0:07:06.600 a little window somewhere in the skull and showed you 0:07:06.680 --> 0:07:09.240 just a little bit of brain tissue. And I used 0:07:09.320 --> 0:07:12.160 that magical microscope so you can see all the spikes 0:07:12.240 --> 0:07:12.960 zipping around. 0:07:13.240 --> 0:07:14.440 And I said to you, hey. 0:07:14.440 --> 0:07:17.720 Are we looking at the visual cortex here, or the 0:07:18.160 --> 0:07:21.840 auditory or the somatosensory or some other part. You wouldn't 0:07:21.840 --> 0:07:24.000 be able to tell me. I wouldn't be able to 0:07:24.000 --> 0:07:26.840 tell you because it's all the same stuff going on 0:07:26.920 --> 0:07:30.280 in there. It all looks the same. There aren't spikes 0:07:30.280 --> 0:07:33.160 that equate to consciousness and other spikes that are running 0:07:33.160 --> 0:07:37.320 around unconsciously. It's all cells and spikes, and they all 0:07:37.360 --> 0:07:42.160 look alike. So why do some patterns of signals mean 0:07:42.200 --> 0:07:46.680 the color red and others mean the smell of apple pie, 0:07:46.800 --> 0:07:50.360 and others mean the pain of a paper cut. It's 0:07:50.400 --> 0:07:52.960 all just signals and networks of cells. It's all the 0:07:53.040 --> 0:07:56.600 same stuff running around. And so this is really the 0:07:56.640 --> 0:07:59.600 heart of the mystery. The brain is made up of 0:07:59.760 --> 0:08:03.120 lots of cells, eighty six billion neurons and about as 0:08:03.160 --> 0:08:06.600 many glial cells. But they're just cells. And the brain, 0:08:06.640 --> 0:08:09.240 as far as we can tell, is just a giant 0:08:09.640 --> 0:08:14.240 machine that's made out of biological wetwear. It's an enormous 0:08:14.280 --> 0:08:18.760 and quite alien computational device. But every cell in the 0:08:18.800 --> 0:08:23.120 brain is driven by the activity of other cells, and 0:08:23.200 --> 0:08:26.040 so no matter how complex the whole system is, it 0:08:26.040 --> 0:08:29.560 appears to be fundamentally a machine in which each sequence 0:08:29.600 --> 0:08:33.120 of actions is leading to the next sequence. It doesn't 0:08:33.320 --> 0:08:37.160 appear that there's some extra bit in the brain that's 0:08:37.200 --> 0:08:40.560 not just about the physical stuff. And so somehow we 0:08:40.600 --> 0:08:44.079 need to look for consciousness in the physical stuff. And 0:08:44.160 --> 0:08:48.760 we know that consciousness depends on the details in the brain, 0:08:49.520 --> 0:08:53.400 because even very small damage to your brain can change 0:08:53.760 --> 0:08:57.920 your consciousness. For example, if your brain is badly damaged, 0:08:57.960 --> 0:09:01.520 you can end up in a coma without consciousness. Your 0:09:01.520 --> 0:09:04.760 brain changes and your consciousness changes. But this happens in 0:09:04.840 --> 0:09:06.199 much more subtle ways. 0:09:06.240 --> 0:09:06.720 Every day. 0:09:06.960 --> 0:09:12.000 When you ingest alcohol, the little ethanol molecules interact with 0:09:12.080 --> 0:09:16.480 your cells and your consciousness changes. Same with drugs, same 0:09:16.520 --> 0:09:20.400 with fatigue, same with low blood sugar. Or if you've 0:09:20.400 --> 0:09:23.200 ever known someone who had a stroke, or got a 0:09:23.280 --> 0:09:27.760 brain tumor, or had a traumatic brain injury, their consciousness 0:09:27.800 --> 0:09:32.080 can change pretty drastically. So we know that consciousness is 0:09:32.200 --> 0:09:35.720 intimately tied to the details of what's going on in 0:09:35.760 --> 0:09:39.760 the brain. Now, the French philosopher Renee Descartes thought that 0:09:40.160 --> 0:09:43.760 the physical and the mental were separate. Essentially, there's a 0:09:44.080 --> 0:09:48.360 separate soul, and that was maybe a reasonable starting guess, 0:09:48.400 --> 0:09:52.800 but centuries of neurology have taught us otherwise. When the 0:09:52.880 --> 0:09:58.000 brain changes, your consciousness changes. You are your brain. You 0:09:58.320 --> 0:10:01.040 can get a surgery and replace your heart entirely with 0:10:01.080 --> 0:10:03.800 an artificial heart, and you're really no different. You can 0:10:03.840 --> 0:10:06.840 get a kidney removed, and you're really no different. But 0:10:07.000 --> 0:10:10.600 even a very tiny change in the brain makes a 0:10:10.760 --> 0:10:15.360 giant difference to your conscious experience. Now, the amazing thing 0:10:15.440 --> 0:10:18.600 is that modern biology knows a lot about what is 0:10:18.679 --> 0:10:21.720 happening inside the human body, all the way down to 0:10:22.360 --> 0:10:25.720 cells and the contents of cells, to the genome and 0:10:25.760 --> 0:10:28.439 the molecules that make up the proteins and so on. 0:10:29.000 --> 0:10:33.320 But where are you in that picture? Why are you 0:10:33.400 --> 0:10:37.479 someone who cares about your life and listens to podcasts 0:10:37.520 --> 0:10:41.800 and has desires and fears and aspirations and tastes and 0:10:41.840 --> 0:10:44.880 so on. One of my mentors, the late Francis Krik, 0:10:44.960 --> 0:10:48.240 had a chalkboard in his office and it was busy 0:10:48.280 --> 0:10:51.120 with lots of scribbles, but there was one word right 0:10:51.160 --> 0:10:54.920 in the center, and that was meaning. And what he 0:10:55.000 --> 0:10:58.000 was reaching for with that was why in the world 0:10:58.040 --> 0:11:01.280 does any stimulus mean mean something to us? Why do 0:11:01.360 --> 0:11:04.480 you care about anything? How do you run a bunch 0:11:04.520 --> 0:11:09.040 of activity through cells and get meaning? This is really 0:11:09.120 --> 0:11:12.440 the question of consciousness, and it's a difficult problem for 0:11:12.520 --> 0:11:17.160 neuroscience to tackle. In part, it's because the language we 0:11:17.280 --> 0:11:20.760 have in science doesn't tell us how to translate from 0:11:20.800 --> 0:11:25.920 the realm of the physical to the realm of subjective experience. 0:11:26.160 --> 0:11:29.800 I can't write down an equation that captures the activity 0:11:29.800 --> 0:11:31.520 in a bunch of cells and then I say, okay, look, 0:11:31.600 --> 0:11:34.000 just do a double integral here and add something and 0:11:34.040 --> 0:11:37.760 carry the five. And that is the feeling of rain 0:11:37.880 --> 0:11:40.880 on a hot day, or the feeling of silk between 0:11:40.920 --> 0:11:45.720 your fingertips, or the sound of a saxophone and a stairwell. 0:11:46.160 --> 0:11:49.240 So science doesn't seem to have the language, at least 0:11:49.320 --> 0:12:09.440 not yet, to translate from the objective to the subjective. Really, 0:12:09.480 --> 0:12:13.080 the easiest way to see what's weird about consciousness is 0:12:13.120 --> 0:12:18.040 to think about other big, complex systems that presumably don't 0:12:18.040 --> 0:12:21.560 have consciousness. So imagine I were to hand you one 0:12:21.640 --> 0:12:25.200 hundred billion tinker toys. You remember those old toys with 0:12:25.240 --> 0:12:28.040 metal rods and connectors, and you can build pulleys and 0:12:28.080 --> 0:12:28.600 levers and. 0:12:28.600 --> 0:12:29.520 Any kind of structure. 0:12:29.840 --> 0:12:33.120 Now, these tinker toys that I hand you are physical 0:12:33.200 --> 0:12:36.400 things that can interact. So you push this one and 0:12:36.440 --> 0:12:38.760 that pulls this and shifts that, and pulls this one 0:12:38.800 --> 0:12:42.120 down and moves that one sideways. Each piece interacts with 0:12:42.160 --> 0:12:45.120 the other pieces around it, just like the brain. So 0:12:45.240 --> 0:12:49.360 the question is, can you build a tinker toy structure 0:12:49.800 --> 0:12:53.880 that is large enough, sophisticated enough that the whole thing 0:12:54.000 --> 0:12:58.320 becomes conscious? At what point do you say, Okay, I'm 0:12:58.360 --> 0:13:00.520 going to add this one more piece and can here 0:13:00.960 --> 0:13:05.320 and now it's enjoying the beauty of a flower, or 0:13:05.440 --> 0:13:09.960 now it's perceiving the color indigo blue, or now it's 0:13:10.040 --> 0:13:15.319 experiencing the smell of sunscreen on the beach. Or consider this, 0:13:15.760 --> 0:13:19.719 What is the difference between your brain and your laptop. 0:13:19.880 --> 0:13:22.120 As I said at the beginning, your brain is shuttling 0:13:22.160 --> 0:13:26.400 signals all around, and so is your laptop. But presumably 0:13:26.960 --> 0:13:31.400 your computer doesn't feel anything. It's just running algorithms. When 0:13:31.480 --> 0:13:35.160 you launch a funny YouTube video, it might make you laugh, 0:13:35.600 --> 0:13:40.239 but your computer doesn't feel amused or thrilled or surprised 0:13:40.360 --> 0:13:44.800 or mirthful. It's just moving around voltages through billions of gates. 0:13:45.440 --> 0:13:49.640 So what is the difference between you and it? Why 0:13:49.679 --> 0:13:54.440 do electrical signals in the computer equal logical operations or 0:13:54.440 --> 0:13:59.040 pixel colors, while electrical signals zapping around in your brain 0:13:59.600 --> 0:14:03.080 equate to the sweetness of sugar or the sting of 0:14:03.240 --> 0:14:06.839 wabi or the feeling of love. Why do we have 0:14:06.920 --> 0:14:12.680 this internal theater instead of running like tinker toys or laptops. Now, 0:14:12.679 --> 0:14:15.160 one thing to note is we're tackling this question is 0:14:15.200 --> 0:14:19.320 that consciousness seems to have evolved because it is useful. 0:14:19.680 --> 0:14:23.520 Consciousness is like a high level operating system. So back 0:14:23.520 --> 0:14:27.400 in the day, you'd program computers directly with punch cards 0:14:27.480 --> 0:14:32.720 or in machine language, But eventually we developed user interfaces 0:14:32.840 --> 0:14:37.080 like Windows, which hid all of the complex operations of 0:14:37.080 --> 0:14:40.000 the computer and allowed us to just deal with the 0:14:40.080 --> 0:14:43.120 stuff we needed at the highest level. I just want 0:14:43.160 --> 0:14:45.400 to move this thing over here, and send this email 0:14:45.440 --> 0:14:49.720 and drop this picture, And that's essentially what consciousness seems 0:14:49.760 --> 0:14:51.800 to be. It's a way for us to just have 0:14:51.880 --> 0:14:55.280 the highest level picture of what's going on, Like let's 0:14:55.320 --> 0:14:57.880 go get some breakfast and go for a walk. Without 0:14:58.080 --> 0:15:01.280 needing to deal with all the billion details of how 0:15:01.320 --> 0:15:03.880 your muscles are contracting and how you're getting oxygen to 0:15:03.880 --> 0:15:06.840 the right places and which chemicals need to be expressed. 0:15:07.440 --> 0:15:12.760 We just get the windows without all the machine code. Okay, 0:15:12.800 --> 0:15:15.240 So let's return to the central question. How do you 0:15:15.480 --> 0:15:19.240 build consciousness out of cells? In other words, how do 0:15:19.320 --> 0:15:23.800 you get some magical high level property from simple low 0:15:23.880 --> 0:15:27.800 level parts. Now that sounds impossible, but the first thing 0:15:27.800 --> 0:15:31.800 to understand is the concept of an emergent property. To 0:15:31.960 --> 0:15:35.360 understand consciousness, we may need to think not in terms 0:15:35.360 --> 0:15:38.280 of the pieces and parts of the brain, but instead 0:15:38.320 --> 0:15:41.400 in terms of how they all interact with each other. 0:15:42.200 --> 0:15:44.760 So if we want to understand how simple parts can 0:15:44.760 --> 0:15:47.880 give rise to something bigger than themselves, just think of 0:15:47.920 --> 0:15:51.880 something like an ant hill, look at something like leafcutter. 0:15:52.000 --> 0:15:52.400 Ants. 0:15:53.560 --> 0:15:57.040 They've got millions of members in a colony, and they 0:15:57.080 --> 0:16:00.640 act like farmers. They actually cultivate their own food. Different 0:16:00.840 --> 0:16:05.280 ants have different roles. Some leave the nest to find 0:16:05.760 --> 0:16:08.880 fresh vegetation, and when they find it, they chew off 0:16:08.960 --> 0:16:12.280 large pieces that they carry back to the nest. But 0:16:12.320 --> 0:16:15.880 they don't eat the leaves instead. What happens is these 0:16:16.120 --> 0:16:19.160 smaller worker ants take the pieces of leaves and they 0:16:19.200 --> 0:16:22.200 chew them into smaller pieces, and they use this as 0:16:22.440 --> 0:16:28.920 fertilizer to grow fungus in large underground gardens. So the 0:16:28.960 --> 0:16:33.280 ants feed the fungus, and the fungus blossoms into small 0:16:33.400 --> 0:16:36.960 fruiting bodies which the ants later eat. So they use 0:16:37.000 --> 0:16:42.680 this incredible farming strategy to build enormous nests underground that 0:16:42.840 --> 0:16:46.880 extend sometimes hundreds of square meters. So, just like humans, 0:16:46.920 --> 0:16:51.600 the leafcutter ants have built and perfected an agricultural civilization. 0:16:52.520 --> 0:16:53.760 But here's the important point. 0:16:53.840 --> 0:16:58.600 Although the colony is like a superorganism that accomplishes these 0:16:58.640 --> 0:17:04.200 extraordinary feats, each ant individually behaves just like a simple 0:17:04.200 --> 0:17:08.600 little robot. It just follows its local rules. The queen 0:17:08.840 --> 0:17:13.560 isn't giving commands and coordinating behavior. Instead, each ant just 0:17:13.680 --> 0:17:18.000 reacts to local chemical signals from other ants, or from 0:17:18.280 --> 0:17:21.000 larvae or intruders, or food. 0:17:20.760 --> 0:17:21.800 Or waste or leaves. 0:17:22.080 --> 0:17:26.800 Each ant is just a simple autonomous unit whose reactions 0:17:26.840 --> 0:17:31.640 depend only on its local environment and its genetically encoded rules. 0:17:32.440 --> 0:17:37.919 So even though there's no centralized decision making, the colony 0:17:38.119 --> 0:17:44.000 exhibits very sophisticated behavior. Each ant communicates locally with no 0:17:44.200 --> 0:17:47.040 sense of the bigger picture. But what emerges at the 0:17:47.160 --> 0:17:53.840 level of the colony is an agricultural civilization. So the 0:17:53.880 --> 0:17:57.320 important lesson here is that the complex behavior of the 0:17:57.359 --> 0:18:03.399 colony doesn't arise from complexity in the individuals. Each ant 0:18:03.480 --> 0:18:05.840 doesn't know that it's part of something bigger. It's just 0:18:05.960 --> 0:18:10.240 running its small, simple programs. But when enough ants come together, 0:18:10.920 --> 0:18:16.440 a super organism emerges with collective properties that are more 0:18:16.480 --> 0:18:21.080 sophisticated than its basic parts, and this phenomenon is known 0:18:21.119 --> 0:18:25.480 as emergence. This is what happens when simple units interact 0:18:25.520 --> 0:18:29.840 in the right ways and something larger emerges. The key 0:18:29.880 --> 0:18:34.200 thing is the interaction between lots of ants, and this 0:18:34.320 --> 0:18:37.840 is what's going on with the brain. A neuron is 0:18:37.920 --> 0:18:40.160 just a type of cell. It's just like the other 0:18:40.320 --> 0:18:43.919 cells in your body, but with some specializations that allow 0:18:43.960 --> 0:18:49.680 it to extend processes and propagate these electrical signals. But 0:18:49.880 --> 0:18:53.040 like an ant, an individual brain cell is just running 0:18:53.080 --> 0:18:56.560 its local programs its whole life. It just carries these 0:18:56.600 --> 0:19:00.879 electrical signals along its membrane. It spits out neuro transmitters 0:19:01.040 --> 0:19:03.480 it gets spat on by other cells. 0:19:03.840 --> 0:19:04.960 That's it. 0:19:04.960 --> 0:19:09.320 It lives its life in darkness, embedded in other cells. 0:19:09.400 --> 0:19:13.320 It doesn't know if it's involved in moving your eyes 0:19:13.440 --> 0:19:16.199 to read a Tony Morrison novel, or it's involved in 0:19:16.280 --> 0:19:19.600 moving your hands over the piano keyboard to play Mozart. 0:19:20.000 --> 0:19:23.440 It doesn't know about you. So here's what's so weird. 0:19:23.480 --> 0:19:28.760 Although your goals and intentions and abilities are completely dependent 0:19:28.960 --> 0:19:32.520 on the existence of these little neurons, they live on 0:19:32.600 --> 0:19:36.600 a smaller scale with no awareness of the thing they 0:19:36.640 --> 0:19:40.840 have come together to build you. But get enough of 0:19:40.880 --> 0:19:44.479 these basic brain cells together interacting the right way, and 0:19:44.560 --> 0:19:48.000 the mind emerges. And I'll talk more about this notion 0:19:48.080 --> 0:19:51.720 of emergent properties in other episodes, because the concept is 0:19:51.760 --> 0:19:57.400 so fundamental. Everywhere you look you find systems with emergent properties. 0:19:57.840 --> 0:20:01.080 Take an airplane. If you take any single hunk of 0:20:01.160 --> 0:20:04.560 metal on the airplane, not a single one of these 0:20:04.640 --> 0:20:08.400 pieces has the property of flight. But when you arrange 0:20:08.440 --> 0:20:13.240 all the pieces in the right way, flight emerges. Or 0:20:13.560 --> 0:20:17.240 imagine a bunch of metal poles. None has the property 0:20:17.480 --> 0:20:21.840 of constraining the behavior of a lion, but arrange several 0:20:21.840 --> 0:20:24.320 of these poles in the shape of a cage and 0:20:24.440 --> 0:20:30.400 the property of lion constraining emerges. And somehow you get 0:20:30.400 --> 0:20:32.879 a bunch of simple cells together and you wire them 0:20:32.960 --> 0:20:37.919 up in the right way, and consciousness emerges. So the 0:20:37.960 --> 0:20:41.400 pieces in parts of a system can be individually simple, 0:20:41.720 --> 0:20:44.919 but what emerges at a higher level is all about 0:20:45.000 --> 0:20:49.879 their interaction. So the mind seems to emerge from the 0:20:49.920 --> 0:20:52.800 interaction of the billions of pieces and parts of the brain. 0:20:53.200 --> 0:20:56.639 But this leads to a wacky question. Can a mind 0:20:56.880 --> 0:21:01.520 emerge from anything with lots of inter acting parts? For example, 0:21:01.840 --> 0:21:05.800 could a city be conscious? After all, a city is 0:21:05.840 --> 0:21:09.320 built on the interactions between elements. Think of all the 0:21:09.440 --> 0:21:12.680 signals moving through a city. You've got telephone wires and 0:21:12.760 --> 0:21:17.040 fiber optic lines and sewers carrying waste, and every handshake 0:21:17.119 --> 0:21:20.240 between humans, and every traffic light and so on. This 0:21:20.480 --> 0:21:24.080 scale of interaction in a city is on par with 0:21:24.119 --> 0:21:26.560 the human brain. Now, it would be very hard to 0:21:26.680 --> 0:21:29.680 know if a city were conscious, because it doesn't have 0:21:30.200 --> 0:21:32.520 ears and a mouth, and so how could it tell us? 0:21:32.560 --> 0:21:36.439 How could we ask it? To answer a question like 0:21:36.520 --> 0:21:42.000 this requires a deeper question. For a network to experience consciousness, 0:21:42.080 --> 0:21:45.160 does it need more than just a number of parts, 0:21:45.240 --> 0:21:50.320 but beyond that a very particular structure to the interactions, 0:21:51.040 --> 0:21:53.000 and that leads us to what we have in terms 0:21:53.040 --> 0:21:57.320 of scientific theories of consciousness. By the way, just a 0:21:57.400 --> 0:22:00.439 side note before we get into the scientific theories. For 0:22:00.520 --> 0:22:03.320 the purposes of this episode, we'll assume that everyone is 0:22:03.359 --> 0:22:06.840 having the same type of conscious experience. What's interesting is 0:22:06.880 --> 0:22:10.000 that we don't really have any idea how to measure consciousness, 0:22:10.000 --> 0:22:13.080 so we don't really know if other people are conscious. 0:22:13.600 --> 0:22:18.240 And there's a branch of philosophy called sollipsism, which suggests 0:22:18.280 --> 0:22:20.879 that you are the only conscious person in the world 0:22:21.160 --> 0:22:24.760 and everyone else is not conscious. They're just moving zeros 0:22:24.760 --> 0:22:27.159 and ones around and saying the right things and acting 0:22:27.160 --> 0:22:29.960 in the right way. But let's not go there. I 0:22:29.960 --> 0:22:32.800 think it's a reasonable assumption to take on board the 0:22:32.880 --> 0:22:37.600 notion that everyone around you is conscious and having private 0:22:37.800 --> 0:22:42.040 internal experiences just like you are. So one way you 0:22:42.040 --> 0:22:46.880 could go about studying consciousness scientifically is by saying, when 0:22:46.920 --> 0:22:51.119 you are seeing the color orange, what are the neurons 0:22:51.119 --> 0:22:54.879 that are lighting up? And when you're tasting cinnamon, which 0:22:54.960 --> 0:22:57.480 neurons are popping off? Or when you're conscious of a 0:22:57.640 --> 0:23:01.280 face or conscious of a touch or a sound, What 0:23:01.400 --> 0:23:04.919 precisely can we measure in the brain. Now, this is 0:23:04.960 --> 0:23:08.520 an endeavor that was emphasized by scientists like Francis Krik 0:23:08.560 --> 0:23:12.000 and Christoph Coch. They said, hey, as the first step here, 0:23:12.359 --> 0:23:17.280 let's try to find the neural correlates of consciousness, as in, 0:23:17.359 --> 0:23:19.959 when you are conscious of something, what is lighting up 0:23:19.960 --> 0:23:22.720 in your brain. One way you can study this is 0:23:22.720 --> 0:23:27.080 by looking at something like binocular rivalry. So I'll explain 0:23:27.119 --> 0:23:29.240 what that is. Let's say that your two eyes are 0:23:29.240 --> 0:23:33.120 seeing very different images. In your left eye, I show 0:23:33.160 --> 0:23:35.800 you a picture of a shoe, and in your right eye, 0:23:35.840 --> 0:23:38.080 I show you a picture of a house, and there's 0:23:38.080 --> 0:23:40.879 a piece of cardboard in between your eyes, so that 0:23:41.040 --> 0:23:44.320 each eye is just seeing one thing, the shoe. 0:23:44.160 --> 0:23:44.760 Or the house. 0:23:45.520 --> 0:23:48.679 Your conscious experience is not of seeing them both at 0:23:48.680 --> 0:23:53.040 the same time or a fusion. Instead, you see one 0:23:53.680 --> 0:23:56.679 and then after a few seconds it switches and you 0:23:56.680 --> 0:23:59.199 see the other. You see the shoe, and then you 0:23:59.200 --> 0:24:01.639 see the house, and then it's back to the shoe, 0:24:02.080 --> 0:24:05.040 and it switches every few seconds. And it's not because 0:24:05.040 --> 0:24:07.920 you're moving your eyes around or something. It just happens 0:24:08.000 --> 0:24:10.879 as your brain lands on one percept or lands on 0:24:10.920 --> 0:24:14.560 the other. So if I ask you about your conscious experience, 0:24:15.000 --> 0:24:18.000 you are seeing either the shoe or you're seeing the 0:24:18.040 --> 0:24:21.520 house at any given moment. So you can use experiments 0:24:21.640 --> 0:24:25.040 like this to then look for the correlates of consciousness. 0:24:25.080 --> 0:24:27.920 You can map which areas of the brain are firing 0:24:27.960 --> 0:24:31.159 when you're conscious of the shoe versus the house. We 0:24:31.240 --> 0:24:34.000 can look for what is different about the patterns of 0:24:34.040 --> 0:24:37.320 neural activity in the moments when you're perceiving the shoe 0:24:37.760 --> 0:24:40.200 versus when you're perceiving the house. The key thing is 0:24:40.240 --> 0:24:43.360 that I'm not changing anything in the outside world. The 0:24:43.440 --> 0:24:47.680 only thing that's changing is your internal experiences. So the 0:24:47.800 --> 0:24:51.760 question is what is the difference going on inside the brain. Now, 0:24:51.800 --> 0:24:55.520 this sort of study has been an ongoing endeavor, but 0:24:55.720 --> 0:24:58.919 part of the challenge with these types of experiments is 0:24:58.920 --> 0:25:02.119 that we don't have great techniques to measure the activity 0:25:02.560 --> 0:25:05.760 in billions of individual cells. All we have are things 0:25:05.880 --> 0:25:11.320 like fMRI functional magnetic resonance imaging, which allows us to 0:25:11.400 --> 0:25:14.479 measure great, big chunks of activity in the brain at 0:25:14.480 --> 0:25:17.879 any moment. So we can see big blobs of activity, 0:25:17.920 --> 0:25:21.440 but we can't narrow down with a high degree of specificity. 0:25:22.119 --> 0:25:25.399 As technology gets better, we can see a pathway to 0:25:25.520 --> 0:25:46.159 eventually answering these kinds of questions with greater specificity. So 0:25:46.720 --> 0:25:50.280 those types of experiments are ongoing and they're fascinating, but 0:25:50.359 --> 0:25:55.879