How do your billions of tiny brain cells build consciousness as they chatter away with electrical spikes and chemical signals? And why is your laptop, with its sophisticated algorithms and billions of parts, presumably not conscious? Could other large systems like a city become conscious? And what does this have to do with ant hills, blue birds, or your memory of your first kiss? Join Eagleman on a journey into one of the central mysteries of neuroscience: why we have awareness.
How do your billions of tiny brain cells with their electrical spikes build consciousness? And why is your laptop, with its billions of parts and tiny electrical signals, presumably not conscious? Could other large systems like a city be conscious? And what does any of this have to do with ant hills or bluebirds or your memory of your first kiss? Welcome to Inner Cosmos with me David Eagleman. I'm a neuroscientist and an author at Stanford University, and I've spent my whole career studying the intersection between how the brain works and how we experience life. And there's hardly a better example of this intersection than consciousness. Your feeling of being aware of your surroundings and your own existence, your ability to experience and feel things. This somehow emerges from the activity of our brains, and it is our experience of life. So today we're going to dive deep into a big question, possibly the central question of neurobiology. What is consciousness. We'll talk about how we can define it, why it's a challenge for our science to capture it, and whether other things could be conscious. So think back to your first kiss. The memory of it pops back into your head in an instant, But where was that image before you became conscious of it, that feeling, the name of the person, How is it represented in your brain before and after I ask you to think about it. What's the difference between those two states? In other words, what events in the brain constitute awareness or consciousness. I made an earlier episode about all the things going on in your head unconsciously without any access or awareness on your part, and the upshot there was that at any moment, there's an enormous amount of activity going on in your brain, one hundred billion cells having little electrical spikes tens or hundreds of times per second, and you are not consciously aware of almost any of that activity in your brain. But a tiny, tiny bit of that activity is conscious. And so for this episode we're turning to that tiny tiny bit and the question of what is different about that activity than all the other activity in your brain, and why it's such a challenge for us to figure out how to translate that activity in your brain into your private, colorful experience of the world. The explanation of consciousness is one of the major unsolved problems of modern neuroscience, and possibly the most important. So first, what is consciousness. Defining it is the first step to the problem. So there are lots of ways to try to wrap our arms around it. But the definition that I think will get us started the fastest is to say consciousness is the thing that flickers to life when you wake up in the morning. I mean, think about how wacky this is. You have the same brain the moment before you wake up in the moment after, but something just changed a little bit about the activity, the way the signals are moving around, and suddenly you're conscious. Whereas a moment ago you were just lying there like a sack of potatoes. You had the same brain, but you weren't aware of anything. But now your brain cells start to run a slightly different algorithm, and suddenly you're aware of your existence, of your name, of your history, and your bedroom and the smell of coffee and the feel of your sheets and the details of.
The room around you.
Now, weirdly, what you're experiencing is a private experience. It's what we call a subjective experience. It's not objective, which is something we can measure and agree on a shared reality. Instead, only you are experiencing it. So if there's someone else in the bedroom when you wake up and that person is looking around, there are different things going on in that head, different thoughts, different feelings, a different subjective experience. Okay, so imagine you're there and you roll over and you look at a painting on your wall and you see the colors. Now, what's happening inside your brain is that different wavelengths of light are bouncing off the painting and they're activating particular color photoreceptors in the back of your eyes, which sends signals back to your brain through the optic nerve, and in the brain, cells in the visual cortex start activating. And if you had a magical microscope by which you could view what was happening in the brain, you'd see that you have a vast pattern of cells in the back of the brain that activate when you look at one painting color, and a different pattern of cells that activate when you look at a different color. But the question is why do you perceive the red in the painting as red? There's just a particular wavelength of light associated with your private subjective experience of seeing red.
But the redness is something made.
Up by the brain and could just as easily be perceived by you as blue or green or anything else. So why does this particular pattern of cells equally a particular color. These are called qualia. Qualia are the features of our experience, the internal experiences that are associated with conscious states. The redness of red in this case, or the sweetness of sugar, or the pain of a headache, these are called qualia. Now, these are irreducible, which means they can't be described in terms of something else. And by the way, they're also ineffable, which means they can't be fully explained or described in words like if I ask you, what does an avocado taste like, how are you going to answer that. Let's say that I tell you I've never eaten an avocado, and I really want you to tell me what that experience is. It's not something that you can directly transmit to me, because it's an experience that's private to you and generally cannot be reduced to words. The last piece of the foundation that we need is that when you look in the brain, it's all just neural signals going on, and all those signals look exactly the same. So if I opened up a little window somewhere in the skull and showed you just a little bit of brain tissue. And I used that magical microscope so you can see all the spikes zipping around.
And I said to you, hey.
Are we looking at the visual cortex here, or the auditory or the somatosensory or some other part. You wouldn't be able to tell me. I wouldn't be able to tell you because it's all the same stuff going on in there. It all looks the same. There aren't spikes that equate to consciousness and other spikes that are running around unconsciously. It's all cells and spikes, and they all look alike. So why do some patterns of signals mean the color red and others mean the smell of apple pie, and others mean the pain of a paper cut. It's all just signals and networks of cells. It's all the same stuff running around. And so this is really the heart of the mystery. The brain is made up of lots of cells, eighty six billion neurons and about as many glial cells. But they're just cells. And the brain, as far as we can tell, is just a giant machine that's made out of biological wetwear. It's an enormous and quite alien computational device. But every cell in the brain is driven by the activity of other cells, and so no matter how complex the whole system is, it appears to be fundamentally a machine in which each sequence of actions is leading to the next sequence. It doesn't appear that there's some extra bit in the brain that's not just about the physical stuff. And so somehow we need to look for consciousness in the physical stuff. And we know that consciousness depends on the details in the brain, because even very small damage to your brain can change your consciousness. For example, if your brain is badly damaged, you can end up in a coma without consciousness. Your brain changes and your consciousness changes. But this happens in much more subtle ways.
Every day.
When you ingest alcohol, the little ethanol molecules interact with your cells and your consciousness changes. Same with drugs, same with fatigue, same with low blood sugar. Or if you've ever known someone who had a stroke, or got a brain tumor, or had a traumatic brain injury, their consciousness can change pretty drastically. So we know that consciousness is intimately tied to the details of what's going on in the brain. Now, the French philosopher Renee Descartes thought that the physical and the mental were separate. Essentially, there's a separate soul, and that was maybe a reasonable starting guess, but centuries of neurology have taught us otherwise. When the brain changes, your consciousness changes. You are your brain. You can get a surgery and replace your heart entirely with an artificial heart, and you're really no different. You can get a kidney removed, and you're really no different. But even a very tiny change in the brain makes a giant difference to your conscious experience. Now, the amazing thing is that modern biology knows a lot about what is happening inside the human body, all the way down to cells and the contents of cells, to the genome and the molecules that make up the proteins and so on. But where are you in that picture? Why are you someone who cares about your life and listens to podcasts and has desires and fears and aspirations and tastes and so on. One of my mentors, the late Francis Krik, had a chalkboard in his office and it was busy with lots of scribbles, but there was one word right in the center, and that was meaning. And what he was reaching for with that was why in the world does any stimulus mean mean something to us? Why do you care about anything? How do you run a bunch of activity through cells and get meaning? This is really the question of consciousness, and it's a difficult problem for neuroscience to tackle. In part, it's because the language we have in science doesn't tell us how to translate from the realm of the physical to the realm of subjective experience. I can't write down an equation that captures the activity in a bunch of cells and then I say, okay, look, just do a double integral here and add something and carry the five. And that is the feeling of rain on a hot day, or the feeling of silk between your fingertips, or the sound of a saxophone and a stairwell. So science doesn't seem to have the language, at least not yet, to translate from the objective to the subjective. Really, the easiest way to see what's weird about consciousness is to think about other big, complex systems that presumably don't have consciousness. So imagine I were to hand you one hundred billion tinker toys. You remember those old toys with metal rods and connectors, and you can build pulleys and levers and.
Any kind of structure.
Now, these tinker toys that I hand you are physical things that can interact. So you push this one and that pulls this and shifts that, and pulls this one down and moves that one sideways. Each piece interacts with the other pieces around it, just like the brain. So the question is, can you build a tinker toy structure that is large enough, sophisticated enough that the whole thing becomes conscious? At what point do you say, Okay, I'm going to add this one more piece and can here and now it's enjoying the beauty of a flower, or now it's perceiving the color indigo blue, or now it's experiencing the smell of sunscreen on the beach. Or consider this, What is the difference between your brain and your laptop. As I said at the beginning, your brain is shuttling signals all around, and so is your laptop. But presumably your computer doesn't feel anything. It's just running algorithms. When you launch a funny YouTube video, it might make you laugh, but your computer doesn't feel amused or thrilled or surprised or mirthful. It's just moving around voltages through billions of gates. So what is the difference between you and it? Why do electrical signals in the computer equal logical operations or pixel colors, while electrical signals zapping around in your brain equate to the sweetness of sugar or the sting of wabi or the feeling of love. Why do we have this internal theater instead of running like tinker toys or laptops. Now, one thing to note is we're tackling this question is that consciousness seems to have evolved because it is useful. Consciousness is like a high level operating system. So back in the day, you'd program computers directly with punch cards or in machine language, But eventually we developed user interfaces like Windows, which hid all of the complex operations of the computer and allowed us to just deal with the stuff we needed at the highest level. I just want to move this thing over here, and send this email and drop this picture, And that's essentially what consciousness seems to be. It's a way for us to just have the highest level picture of what's going on, Like let's go get some breakfast and go for a walk. Without needing to deal with all the billion details of how your muscles are contracting and how you're getting oxygen to the right places and which chemicals need to be expressed. We just get the windows without all the machine code. Okay, So let's return to the central question. How do you build consciousness out of cells? In other words, how do you get some magical high level property from simple low level parts. Now that sounds impossible, but the first thing to understand is the concept of an emergent property. To understand consciousness, we may need to think not in terms of the pieces and parts of the brain, but instead in terms of how they all interact with each other. So if we want to understand how simple parts can give rise to something bigger than themselves, just think of something like an ant hill, look at something like leafcutter.
Ants.
They've got millions of members in a colony, and they act like farmers. They actually cultivate their own food. Different ants have different roles. Some leave the nest to find fresh vegetation, and when they find it, they chew off large pieces that they carry back to the nest. But they don't eat the leaves instead. What happens is these smaller worker ants take the pieces of leaves and they chew them into smaller pieces, and they use this as fertilizer to grow fungus in large underground gardens. So the ants feed the fungus, and the fungus blossoms into small fruiting bodies which the ants later eat. So they use this incredible farming strategy to build enormous nests underground that extend sometimes hundreds of square meters. So, just like humans, the leafcutter ants have built and perfected an agricultural civilization.
But here's the important point.
Although the colony is like a superorganism that accomplishes these extraordinary feats, each ant individually behaves just like a simple little robot. It just follows its local rules. The queen isn't giving commands and coordinating behavior. Instead, each ant just reacts to local chemical signals from other ants, or from larvae or intruders, or food.
Or waste or leaves.
Each ant is just a simple autonomous unit whose reactions depend only on its local environment and its genetically encoded rules. So even though there's no centralized decision making, the colony exhibits very sophisticated behavior. Each ant communicates locally with no sense of the bigger picture. But what emerges at the level of the colony is an agricultural civilization. So the important lesson here is that the complex behavior of the colony doesn't arise from complexity in the individuals. Each ant doesn't know that it's part of something bigger. It's just running its small, simple programs. But when enough ants come together, a super organism emerges with collective properties that are more sophisticated than its basic parts, and this phenomenon is known as emergence. This is what happens when simple units interact in the right ways and something larger emerges. The key thing is the interaction between lots of ants, and this is what's going on with the brain. A neuron is just a type of cell. It's just like the other cells in your body, but with some specializations that allow it to extend processes and propagate these electrical signals. But like an ant, an individual brain cell is just running its local programs its whole life. It just carries these electrical signals along its membrane. It spits out neuro transmitters it gets spat on by other cells.
That's it.
It lives its life in darkness, embedded in other cells. It doesn't know if it's involved in moving your eyes to read a Tony Morrison novel, or it's involved in moving your hands over the piano keyboard to play Mozart. It doesn't know about you. So here's what's so weird. Although your goals and intentions and abilities are completely dependent on the existence of these little neurons, they live on a smaller scale with no awareness of the thing they have come together to build you. But get enough of these basic brain cells together interacting the right way, and the mind emerges. And I'll talk more about this notion of emergent properties in other episodes, because the concept is so fundamental. Everywhere you look you find systems with emergent properties. Take an airplane. If you take any single hunk of metal on the airplane, not a single one of these pieces has the property of flight. But when you arrange all the pieces in the right way, flight emerges. Or imagine a bunch of metal poles. None has the property of constraining the behavior of a lion, but arrange several of these poles in the shape of a cage and the property of lion constraining emerges. And somehow you get a bunch of simple cells together and you wire them up in the right way, and consciousness emerges. So the pieces in parts of a system can be individually simple, but what emerges at a higher level is all about their interaction. So the mind seems to emerge from the interaction of the billions of pieces and parts of the brain. But this leads to a wacky question. Can a mind emerge from anything with lots of inter acting parts? For example, could a city be conscious? After all, a city is built on the interactions between elements. Think of all the signals moving through a city. You've got telephone wires and fiber optic lines and sewers carrying waste, and every handshake between humans, and every traffic light and so on. This scale of interaction in a city is on par with the human brain. Now, it would be very hard to know if a city were conscious, because it doesn't have ears and a mouth, and so how could it tell us? How could we ask it? To answer a question like this requires a deeper question. For a network to experience consciousness, does it need more than just a number of parts, but beyond that a very particular structure to the interactions, and that leads us to what we have in terms of scientific theories of consciousness. By the way, just a side note before we get into the scientific theories. For the purposes of this episode, we'll assume that everyone is having the same type of conscious experience. What's interesting is that we don't really have any idea how to measure consciousness, so we don't really know if other people are conscious. And there's a branch of philosophy called sollipsism, which suggests that you are the only conscious person in the world and everyone else is not conscious. They're just moving zeros and ones around and saying the right things and acting in the right way. But let's not go there. I think it's a reasonable assumption to take on board the notion that everyone around you is conscious and having private internal experiences just like you are. So one way you could go about studying consciousness scientifically is by saying, when you are seeing the color orange, what are the neurons that are lighting up? And when you're tasting cinnamon, which neurons are popping off? Or when you're conscious of a face or conscious of a touch or a sound, What precisely can we measure in the brain. Now, this is an endeavor that was emphasized by scientists like Francis Krik and Christoph Coch. They said, hey, as the first step here, let's try to find the neural correlates of consciousness, as in, when you are conscious of something, what is lighting up in your brain. One way you can study this is by looking at something like binocular rivalry. So I'll explain what that is. Let's say that your two eyes are seeing very different images. In your left eye, I show you a picture of a shoe, and in your right eye, I show you a picture of a house, and there's a piece of cardboard in between your eyes, so that each eye is just seeing one thing, the shoe.
Or the house.
Your conscious experience is not of seeing them both at the same time or a fusion. Instead, you see one and then after a few seconds it switches and you see the other. You see the shoe, and then you see the house, and then it's back to the shoe, and it switches every few seconds. And it's not because you're moving your eyes around or something. It just happens as your brain lands on one percept or lands on the other. So if I ask you about your conscious experience, you are seeing either the shoe or you're seeing the house at any given moment. So you can use experiments like this to then look for the correlates of consciousness. You can map which areas of the brain are firing when you're conscious of the shoe versus the house. We can look for what is different about the patterns of neural activity in the moments when you're perceiving the shoe versus when you're perceiving the house. The key thing is that I'm not changing anything in the outside world. The only thing that's changing is your internal experiences. So the question is what is the difference going on inside the brain. Now, this sort of study has been an ongoing endeavor, but part of the challenge with these types of experiments is that we don't have great techniques to measure the activity in billions of individual cells. All we have are things like fMRI functional magnetic resonance imaging, which allows us to measure great, big chunks of activity in the brain at any moment. So we can see big blobs of activity, but we can't narrow down with a high degree of specificity. As technology gets better, we can see a pathway to eventually answering these kinds of questions with greater specificity. So those types of experiments are ongoing and they're fascinating, but they're only attempting to answer the easy problem of consciousness. What am I referring to when I say the easy problem? Some years ago, the philosopher David Chalmers divided the scientific exploration of consciousness into two categories. There's the easy problem and the hard problem. The easy problem is to find neural signals that correlate with consciousness, as in this region is active when you're conscious of something. But the hard problem of consciousness is explaining why the physical stuff of the brain gives rise to subjective experience. It's a hard problem because it's not clear how physical stuff gives rise to a private internal life.
That's the hard problem.
Now we don't know the answer to this, but we can make progress by being very clear about the different challenges. One of them is something called the binding problem. For example, imagine that you look at your window and you see a beautiful blue bird fly past. Different signals from the bird are processed by different regions of your brain. So part of your brain is detecting the motion. This is the dorsal stream. Part of your brain is recognizing the shape of the bird. That's the ventral stream. Part of your brain is registering the blue color. This is a network called visual area four. Part of your brain is listening to the sound of the bird chirping.
This is your auditory system.
The features of the bird are getting represented in totally different territories of your brain. And yet somehow your brain is able to put all of this information together so that you see a single unified bird. You don't see the blue bleeding off, the moving object, and the sound coming from somewhere else. It all seems like one thing, even though it's processed in a bunch of different parts. Now, how do all these processing streams get combined. How do our brains take the disparate pieces of information that we receive from our senses and combine them into a single, coherent experience of the world. That is the binding problem. All these little pieces of the blue bird somehow get bound together. What's the solution? We don't know. One theory is that the brain uses timing information to integrate things. This means that different pieces of information are bound together by the fact that they're all popping off in the brain at the same time. For example, when you see the moving blue bird, the signals representing motion and the signals representing birdness and blueness, and the signals identifying the sound, they're all synchronized. Like imagine that you're at a stadium full of people and you clap your hands every three seconds, and scattered in the crowd are others who clap their hands every three seconds at exactly the same time that you do.
The idea is that you'd come.
To be able to pick out these folks out of this giant crowd because you'd realize your synchrony with them. And that's the general idea with this temporal binding theory. And there are various other ways that people think about how the binding problem gets solved. One is called global workspace theory. This was proposed by my colleague Bernard Bars, and the idea is you've got all these disparate elements, but things come together in what Bars calls the global workspace, and that's when you get consciousness. In other words, consciousness arises from the global sharing of information within the brain. Different brain modules are performing their specialized functions, but their output is integrated and made available to the entire brain via this hypothetical global workspace where the information gets combined and different processes compete for attention to enter it. When information gets into the global workspace, it becomes available to conscious awareness and you become aware of it. So in this view, consciousness emerges from the integration of all these diverse sensory and cognitive bits into a single, unified representation, let's say, of the bluebird. Another theory proposed by my colleague Julio Tononi is called integrated information theory. So he's proposed a quantitative definition of consciousness. It's not just about the pieces and parts interacting. Instead, in this framework, there has to be a particular organization that's underlying this interaction. So to study consciousness in the laboratory, Tononi uses transcranial magnetic stimulation TMS to compare the activity in the brain when it's awake and when it's in deep sleep, when your consciousness is not there. So by introducing a burst of electrical current into the cortex, he and his team can then track how the activity spreads, and what he finds is that when his subject is awake and consciously aware, you find these long lasting ripples moving to different cortical areas, and this unmasks this widespread connectivity across the network. But in contrast, when a person is in deep sleep, that same pulse stimulates only a very local area and the activity dies down quickly, So the network has lost its connectivity, and you find the same result. When a person is in a coma, the activity spreads very little, but as a person emerges from a coma over weeks into consciousness, the activity spreads more and more widely. So Toanoni believes this is because when we are awake and conscious, there's widespread communication between different cortical areas, but in contrast, when you're asleep or in a coma, you lose this communication across areas. So in his framework, Toinoni suggests that a conscious system requires a perfect balance of enough complexity to represent very different states. This is called differentiation. Can I distinguish black from white, and hot from cold and so on, and enough connectivity to have distant parts of the network be in tight communication with each other. This is called integration. So in this framework, the balance of differentiation and integration can be quantified, and he proposes that only systems in the right range experience consciousness. Now, if this theory turns out to be correct, they can give a non invasive assessment of the level of consciousness in coma patients. Now it would also give us the means to tell whether inanimate systems have consciousness. So, coming back to this question of whether a city is conscious, this could in theory be answered. It would depend on whether the information flow is a ranged in just the right way with the perfect amount of differentiation and integration. So if we can come up with the right sort of network structure that's needed to give rise to consciousness, we're on our way to understanding whether consciousness could escape its biological origins. In other words, although consciousness evolved along a particular path that resulted in a brain, maybe it doesn't have to be built on top of organic matter. Maybe you could build it just as easily out of silicon, assuming the interactions are organized in the right way. So as our understanding of the brain continues to evolve, we may be eventually able to answer the question of whether a city is conscious or a set of tinker toys, or eventually AI and this all comes down to the philosophical idea of materialism. This is the notion that you can build consciousness out of material stuff, whether that's beer cans and tennis balls, or tinker toys or computers. The magic of conscious experience emerges from the physical pieces and parts arranged in exactly the right way. And if we can figure out that right way, then we should be able to build it. But I want to mention some important caveats. The main one is that it's just a hypothesis that we can build consciousness out of physical stuff. It always needs to be kept in mind. Then our science is still quite young, and there may be other things that were simply not aware of. There's a hypothetical that I shared in my book Incognito to demonstrate this idea. Imagine that somebody living in a primitive tribe out in the desert somewhere finds a radio in the sand, and he's never seen anything like this, and so he picks it up and examines it, and he notices there's a knob on it, and so he sort of touched and playing with that, and he realizes that if he turns the knob that suddenly voices emerged from the box, and so he says, Okay, I'm going to figure out how this box is producing the noise. And he goes through a lot of trial and error, and he figures out that he can take off the back of the radio and there's these wires in there, and with this nest of wires, he does experiments and he figures out that if you pull out this wire temporarily the voices get garbled, and if you pull out this wire over here, the voices stop entirely, and so on. So this person becomes a radio materialist. What he would do is he'd conclude that if you put together this nest of wires in just the right way, with the right structure, the whole thing becomes alive and talks to you.
But he has no idea that.
There are radio towers that are beaming electromagnetic radiation from distant cities. It would never strike him that any of that is going on, because that's not part of it world. So he would come to the erroneous conclusion that if you put together the wires in the right way, they generate voices. And so my point in bringing up this analogy is not to say that our consciousness is getting beamed in from somewhere else. But it is to say it is certainly possible that we're missing big, giant pieces of the puzzle, and that there's something that for us would be the equivalent of not realizing that there's a giant tower beaming signals to the radio. So I began by pointing out that all the data we have in neuroscience says that the physical integrity of the brain needs to be there to have conscious experience, and if you damage your brain, you change consciousness. But the radio example is just meant to demonstrate that there still may be lots of unknowns, And a specific example of an unknown is this, does consciousness arise from hooking things up in the right way or does it instead depend on some special property of biological cells? In other words, is there something special about our biology and the material that makes up our brain that allows us to be conscious? For example, one question that people have been asking is whether there are quantum mechanical effects that happen in biological cells. Quantum mechanics is a branch of physics. It's considered the best scientific theory that we have because it predicts experiments out to fourteen decimal places. But it's very counterintuitive. It's difficult to understand because there are all kinds of very weird effects that happen at the level of atoms. I'll go into detail on that another episode, but for now, I'll just say that some people suggest that some of the spooky properties of quantum mechanics are just the kind of thing we need to explain the mysteries of consciousness. Now, other people have suggested that you can't have quantum mechanical interactions happening in the brain because of the hot temperature, and that may be true, but quantum effects are more and more commonly being discovered in biology, so it's prematu sure to rule it out entirely. For example, it was discovered in recent years that photosynthesis in plants is a quantum mechanical effect, So there are quantum mechanical effects that happen at this temperature and this level. So I'm not asserting there definitely are quantum effects in the human brain, but that's one type of possibility that people consider for how we might get consciousness in a human brain, but perhaps we wouldn't in a classical computer. Just for completeness, I'll mention one other theory that consciousness is like a fifth force in physics. This theory is called pan psychism, and the idea is that consciousness is a property that's present in all physical matter.
It's a property of atoms, and.
When you get a bunch of atoms and cells together and you collect enough of the material of consciousness, that's when consciousness emerges. The theory suggests that the details of the system don't really matter. It's all about getting enough of the material of consciousness together. Now I'm not suggesting pan psychism is true, but I'm mentioning this for completeness to illustrate that our science is quite young and we have no idea what the answer is, so we certainly can't rule things out prematurely. Okay, So we've talked about the mystery of consciousness and fundamentally how little we still know about it. And there's more, which is that to make progress towards the solution, we first need to get straight what phenomenon we're trying to explain. Consciousness is probably not like a light bulb, where it's either on or off. It may be that consciousness varies a lot between one person and another, between one species and another, and.
Also within you over time.
So consciousness is a diverse phenomenon and we still haven't yet figured out how the physical equals the mental. The ideas that we've looked at today start to help us understand some of the structure that might have to be in place for consciousness to emerge, but there are many questions to be answered. So for the next episode, I'm going to dive a little deeper into one aspect of this. I want to ask if it would be possible to upload our consciousness from our heads onto another substrate like silicon. Is it possible to transfer our consciousness to someone else or something else? And if so, could that be a solution to the problem of mortality. To find out more and to find further readings on this topic, head to eagleman dot com slash podcast, and if you have any questions or discussions, please send an email to podcast at eagleman dot com. You can also watch full episodes of Inner Cosmos on YouTube. Subscribe to inner cosmospods so you can follow along each week with new updates until next time. I'm David Eagleman, and this is Inner Cosmos.