So just over a year ago, for the third time in my life, I ceased to exist. I was having a small operation. My brain was filling with anesthetic.

I remember a sense of detachment and falling apart and coldness.

And then I was back drowsy and disoriented, but but definitely there.

Now, when you wake from a deep sleep, you might feel confused about the time or anxious about oversleeping, but there's always a basic sense of time having passed, of a continuity between then and now. And coming around from anesthesia is very different. I could have been under for five minutes, five hours, five years, or even 50 years. I simply wasn't there. Was total oblivion.

Anesthesia, it's a modern kind of magic. It turns people into objects and then we hope back again into people. And in this process is one of the greatest remaining mysteries in science and philosophy. How does consciousness happen? Somehow within each of our brains, the combined activity of many billions of neurons, each one a tiny biological machine is generating a conscious experience. And not just any conscious experience, your conscious experience right here and right now. How does this happen? Well, answering this question is so important because consciousness for each of us is all there is. Without it, there's no world, there's no self, there's nothing at all.

Hi, I'm Annil Seth. I'm a professor of neuroscience at the University of Sussex and the author of the book Being You: A New Science of Consciousness. The first question that I have for you is for a regular person just going about their day-to-day. Why is it important to think about consciousness? Why does it matter?

It's really easy to take it for granted, isn't it? I mean, we we just are who we are and the world is how it is and we get on with our daily lives. But I think if you just reflect on it for a little bit and actually think children are very good at this cuz I remember first getting interested in consciousness as a child. I think as many of us are like why am I me and not somebody else? Questions like that. What happens when I die? But this moment of reflection suggests I think makes it clear that everything that matters to us matters through the medium of conscious experience. You know we feel good, we feel bad, we see something beautiful, we see something ugly, we uh without experiencing the world and the self, nothing really matters at all. So I think it's it's a central um concept. It's a central aspect of what it means to be a living human being. There are plenty of other reasons why why it's important. Plenty of other practical applications and you it's not just the realm of of philosophy. It it matters in our daily lives. I think that's fundamentally why we should be interested in it.

One of the uh the many things that I admire about your work is how you take really big complex ideas and you don't um oversimplify them but you do make them accessible. Um and so as we are going to have this conversation that I think is going to touch on a lot of of of big complex ideas about consciousness and conscious experience. Let's actually get started with what I found in your book and in just thinking about these ideas to be one of the easiest most concrete immediate examples which is to think about color, right? That we have a conscious experience of say the color red or the color green.

And we all think that we understand what that is. And yet it's possible, in fact, it's quite likely that other people's perception of those exact same colors is not the exact same as ours. that their experience of the world, their conscious experience is not the same as ours.

Well, I think it's not only likely, it just is the case. There's that example, I think. Um, do you remember it, Chris? I don't know if people listening to this will, but about 10 years ago, there was this photo of a dress that half the world saw as yellow and white and the other half saw us as blue and black. And that's a very clear example of how you can have exact the same exact stimulus, the same image, uh, but we can have a very different subjective experience.

I think color is an excellent example that gets us into this whole issue of of consciousness and why it's important because, as you said, it's it we take it for granted. We're we walk around the world and things are red or things are green, the sky is blue. exist that out there in the world independently of us. But we know that's not true. And this is even before neuroscience gets going really from physics. We know that the electromagnetic spectrum uh goes all the way from radio waves which are very long um to x-rays, gamma rays which are really short. And this so-called visible spectrum is somewhere in the middle. It's a thin slice of reality. And what's more, within that thin slice of reality, we just have uh cells that are sensitive to more or less three different wavelengths. We call them red, green, and blue, but they're not actually colored. They're just three wavelengths of electromagnetic radiation. And out of those three wavelengths, the brain conjures up in millions of different colors. So it's color just is not there out there in the world in the way that it seems. But it's also not made up. You know what's happening as far as people who study this stuff in in detail uh think is that what we experience as color is a sort of property of how different surfaces reflect light in in different ways. And that's why color is useful for us because it helps us keep track of objects when lighting conditions change and when things change. It's very useful thing for our visual systems to be able to do. But it's not this direct transduction of something that exists in objective reality. It requires a brain and a world to experience color.

One of the other reasons why I think color is such an interesting place to start is because my personal experience here is I am color blind. And so I struggle to differentiate between colors certain colors that many other people feel are very clearly different. So to me my experience of the world does not include this bright line between say lavender and light blue. Um certain types of green and brown are are more on a spectrum to me. And so um rather than like there's a there's a a clear difference between them. And one of the things that happens whenever people find out that I'm color blind is we play this game. It's it's like unavoidable. And it doesn't bother me. I know it bothers some other color blind people, but um we end up playing this game where they point at all the things around us and they say, "And what color is that? And what color is that? And what color is that? And what does this look like?" and they're amazed that it's not always the same for me as it is for them.

I mean, mo most people uh the most common form of color blindness and see if this resonates with you is is when what non-colorblind people would say is red and then say is green. Uh people with the most common form of color blindness would perceive those things as being, you know, roughly the same.

Yes, it's a red green color blindness. I don't I will say that that doesn't that example is not what plays out the most in my everyday life. It tends to be the blue and lavender are that's the one that comes up a lot where it's very hard for me to tell the difference. Say the color of a shirt. Um or there are these photos online every once in a while there'll be these photos that kind of go viral which is like how the world looks to someone with red green color blindness. And it'll be two photos that I'm told to someone who does not have this look very different. And to me, those photos look exactly the same. I could not tell you which one is the altered one.

You know, the philosopher Thomas Nagel years ago, 50 years ago, actually, wrote this uh this wonderful essay called, "What is it like to be a bat?" Now, I'm not saying being color blind is like being a bat. No. But his point was that, you know, for each of us, we have our subjective world, and that is unique to us. You know, everybody's world will be different. The subjective world of a bat is going to be very different because they have echolocation and all this other stuff. And the subjective world of someone with color blinds of Eucharist is going to be different with respect to color. Last week or the week before, there was this amazing new experiment published by I think it has a lab in in the US where they use lasers to stimulate one class of uh cell in the retina in the eye um that normally would never be activated just by itself. And they claimed they created a brand new color that no one had ever experienced in the world before. And of course then they tried to describe it and it was it's kind of fun like how do you describe a color that that the claims literally has never been seen before? You know words almost necessarily are going to fail. We use strooscopic light in my lab which is another way of creating very unusual visual experiences. And again in those conditions people report sometimes experiencing colors that they've never seen before. in in being you a new science of consciousness. You describe one idea of of seeing the world as as controlled hallucination. So can you define that and talk to us about about that because I feel like it really ties in with what we're talking about.

The idea of controlled hallucination is is not just an account of how we experience color. I mean the power of the idea at least for me and as I try to explain in the book it's a way of understanding everything that we experience whether it's an emotion or a sense of free will or the sense of being Chris or or being Annel. It's a it's it's a way of understanding everything that we experience whatsoever. The idea is is pretty simple and it's pretty old. I mean, in thinking about color, it's already clear that what we experience isn't this direct readout of what's objectively out there in the world, because colors aren't objectively out there in the world. But now, let's switch perspective a little bit and think about what things are like from the perspective of a brain. So, imagine being a brain. A brain is locked inside this bony vault of a skull. And you know to a first approximation what it's trying to do is figure out what the hell is going on out there in the world or in here in the body. All the brain has to go on are these electrical sensory signals that arrive via the eyes and the ears and so on. And light doesn't just get right into the brain. It's dark in the brain and it's silent. All the brain has are electrical signals that are only indirectly related to the things out there in the world. They don't have labels. So the brain has to infer, has to make a best guess about what is happening in the world based on these ambiguous, unlabeled, uncolored, unounded sensory signals.

The brain makes this best guess about what's happening in the world by continually making predictions about the sensory signals that it's getting. And then instead of just reading out the sensory signals to sort of form this inner picture of the world, the brain is continually updating the predictions. So they explain away um the sensory signals that are coming in. And the key idea here is that what we experience in this story is the content of these inside out predictions. We don't read out the world from the outside in. We always actively construct it, actively generate it from the inside out. Now it turns out math if you do all the maths and all this stuff that if you have a brain which is continually updating its top down inside out predictions to minimize you know the the sensory signals that are coming in to try and you know explain them predict them before they happen. That mathematically is a very very good way for the brain to um approximate exactly what caused the sensory signals out there in the world. It's a very good way to make a best guess. And that's the claim. That's what we experience. And that's why I call it a controlled hallucination, which is a term, you know, like all good analogies. But I like the idea because it emphasizes that our experiences come largely from within. Uh so that's the hallucination part.

A way for me to understand this inside out and outside in dance is I see something exciting and my heart starts pounding and my heart is pounding because I am excited. And then there's also the idea that I see something and my heart starts pounding and then my brain has to decide are your is your heart pounding because you are terrified or because you are excited and that increasingly the the science seems to be pointing towards the second rather than the first.

That's right. There's a theory of emotion from William James who who like many theories in psychology came up with these ideas back in the 19th century. But it was it was James and another guy called Carl Langanger who first put things this way and they gave the example of seeing a bear. So you see a grizzly bear or something, you feel very afraid and adrenaline starts coursing through your body and so you run away. Um, and in this way of thinking about it, you know, you see the bear, that causes an emotion of fear, and the emotion of fear sets and train all these bodily responses that allow you to to run away or fight if you you really want to fight a grizzly bear, which is bad idea. Um, and James kind of flipped that and it's a it's a it's the same kind of flip. So what James suggested was going on was that what we experience as the emotion of fear is more is mostly the brain's perception of the body's response to the bear. So the chain of causation is now subtly but importantly different. We see a bear, brain registers there's a bear cuz that's its best controlled hallucination of what's out there in the world. I mean that itself is is still an inference.

That visual perception of the bear immediately sets in train all these physiological changes in the body, cortisol, adrenaline, all of that. And then it's the brain's perception of these changes in the context of a bear being present that is the emotion of of fear.

And this is is a useful way to think about it because the interior of the body you know the state of the body even on the body on the inside the brain has to infer that too. One of the aha moments for me was to think of this James theory of emotion as actually basically identical to these ideas about how visual perception works. So just as the brain has to infer the causes of its visual signals and that's what we see. It's making predictions about what's out there. The exact same mechanism can do what James was suggesting happens. it can make its best guess about what's happening in the inside of the body and that becomes experiences of emotion. And that's kind of satisfying from a a sort of if you're a theory person, it's very satisfying because you got one simple principle, the brain making and updating predictions that can now bring together what were previously two quite different fields of understanding human experience. you know, visual perception on the one hand and emotion on the other. And I I very I find very appealing when you have these unifying principles and you can start to understand you know different domains of human experience through the same underlying mechanism.

I think that many people especially in the in the western world they often have this idea of the brain as like a supercomput like a a very uh hyper intelligent machine that is processing information and they that image of the brain is is often quite separate from the rest of the body. It seems to me like you are saying that it it is quite a bit more like the full body experience than just the locked away supercomput in in the top.

I think this idea of the brain as a computer has been an extremely powerful metaphor. Um but it's reaching its limits. You know the brain is this is pretty implacable in its complexity. And I think scientists have always struggled to figure out how how can we conceptualize what's what's happening in this gray goo inside our heads. And um initially it was a system of pipes and plumbing and then a telephone network. And since the 1950s this metaphor of a computer has been very powerful. So powerful that that we just sort of take it for granted that the brain computes and processes information. And um you know if you programmed a computer a real you know silicon computer in the right way you'd get everything that you get from real brains including and we'll come back to this consciousness and this is where I start to get really uncomfortable about this metaphor but the computer relies on something to implement the computations but it's it's you it's not nearly as intimately related to the body as you know our brains are related to our physical bodies.

And I think that's super important if we're ever to really understand how brains work and and what they're for. You know, the body isn't just this kind of meat-based robot that can take our brain computer from one meeting to the next. If you, you know, zoom backwards in evolutionary time, every brain that ever existed evolved to control and regulate and guide a body. That's what brains are fundamentally for. I'm inclined to think that we've reached the limits of the brain as computer metaphor. And the brain is actually much richer, much more complex than computers. There's one key difference that that I'll just mention and then I would love to see what you think of it, which is a key principle of all the computers we have um is that we have this sharp separation between software and hardware. I can run the same version of of whatever it is um Word on my computer. It will do the same thing on on yours. And on my computer, I can run many different programs and it'll do the same thing every time, right? If it's working properly. And even a single neuron is a very complicated biological machine that is trying to keep itself going, you know, right down into the furnaces of of metabolism.

And when you see brains like that and understand their their richness and see how different they are from from computers, then it really undermines the the idea that what they're doing is computation because computation makes sense when you've got this sharp separation. And to the extent you don't have that, then it makes much less sense to think of the brain as a computer.

Yeah. I think that the the two things that it makes me immediately think of are one the connection between our our body and our brain in the sense of like you know if you exercise if you lift heavy weights or go for a run it changes how you feel in your brain. It doesn't just change your body in a way that I think if I get a new mouse I don't perceive that as changing how my computer feels.

Right. you're right that um there is this tight interaction between our bodies, our brains and our minds. I mean our brains are part of our bodies. I think this is also something we we often neglect but but the brain is is an organ just as much as our heart, our liver, our kidneys are organs. Uh but it's a it's a distinctive one. It's probably if you're going to have an organ transplant, the brain is the one operation for which you'd want to be the donor and not the recipient.

You ask a question in your book and I think is a really important question for anyone who is listening to this or watching this to ask themselves as well. What is the aspect of being you that you cling to most tightly?

I think the aspect of self that um that I cling to most tightly is this sense of free will. I mean one of the other I think ways in which our intuition can mislead us when we think about consciousness is the idea that the self is just one thing that there is a single essence of Chrisy there isn't a single essence of of an Seth um but that's not the case and there are many ways in neurology psychiatry but also in the lab where we can show that the experience of being a self has all these different aspects which are all present in a kind of unified way for most of us most of the time but which can come apart. So for instance, emotion we already talked about is one part of the experience of self.

It feels like those are on the verge of crossing from the interesting academic questions into a really practical applicable question in a way that is quite frankly to me scary. I so I'll give you just my example that that I'm curious what you think about is for me the aspect of being me that I cling to most tightly is I think some version of uniqueness that like I am me and there isn't another me out there and yet if it was possible to upload my consciousness or to have an artificial intelligence that was trained on my voice and my writing and my thinking so much so that it was the same as me but not me that feels quite disturbing to me and

uh and yet it doesn't feel impossible to imagine a world where we get to that place. So So I'm curious to to hear your take on that.

I think you're absolutely right that this is these are the times we live in and that's both scary but also quite exciting and certainly very interesting place to be. you know, as as someone who's followed these things, of course, both in popular culture, as we all do, but just watching what's happening, the underlying science too. Um, and it's happening in many ways. So, there's the example you give about these these uh avatars is really is really fascinating. And I've had couple of opportunities to have a digital avatar. I haven't yet taken them up because I'm slightly worried about, you know, there are very ethical things about that that I'm I'm I'm concerned about. But the fact is it's it's now possible. I think it would be still distinguishable from me, but it's that's getting, you know, that things will just get better and and and better for sure.

Um, the other example where I think we're on the cusp of something that's going to be ethically and morally very challenging is with brain computer interfaces and you can stimulate the brain too. And here's a situation where on the one hand you've got all these amazing clinical benefits that you just can't argue against and you really shouldn't argue against because they're they're brilliant. You can help people with Parkinson disease. You can restore paralysis uh to people. You can restore sight to blind people potentially. I mean that that's coming. All these these amazing interventions that are on the horizon or even here now in some cases. But then you get to this um other terrain of cognitive enhancements. you know, can someone who's not got paralysis or blindness or Parkinson disease um should we all have brain computer interfaces just as we all have cell phones these days? Well, that's a very very different um world and it's a world where you if you take it to the to an extreme something like free will which you know is at least for me pretty central and part of uniqueness too. You know I feel that the thoughts are my thoughts. I feel that that my actions are my actions. But if now there's a a a brain computer interface that is not merely reading out my intentions to get something done, but actually causing me to have intentions and thoughts that I feel are my own, but I would not have otherwise thought, that's pretty scary to me because once you've got into the brain, there's nowhere else to go.

What should we be doing as regular people to protect our consciousness or to think about it in a way where we won't just wake up in a world that's not the world we want to live in? What what can we do or how can we uh understand this in a different level?

Yeah, I it's it's a very difficult question to to answer. I think the good side of the optimistic view is that there's still time to shape the future in these things. We're not already at the stage of fixing problems um that have already come to exist as we are for instance and how how do we rein in the society problematic consequences of of social media. We can still decide what kinds of technologies we want and what kinds of technology we don't want and how they should be regulated and and or made available. But, you know, I think there are things that, you know, regular folk can do. You know, we we can all do and it it's sort of it may sound slightly cliched or try to say it, but but the most important thing is to just not be scared of of trying to understand what's going on, right? We have to be informed. if we're not informed about what these technologies do um and also how our own brains work too. You know, we don't have to understand every detail. I'm not asking people to go and do whole neuroscience degrees and so on, but the more we understand um how our own minds work, I think the better we'll be able to make informed decisions about the kinds of technologies um that we want to people who are caring for family members and loved ones who have cognitive decline and dementia where this question of is this my mother? Is this my father? Is this the person that I've known? Is not a hypothetical question and it's not a a far-off technological question, but it's kind of a practical day-to-day question of like who is this person that I love and that I care for? And are they the same person they have been? And because you've been in that situation.

So, the the episode I described in in the book, my mother was in a hospital for um operation. She was um just shy of 80 years old. Uh but there were problems in the hospital and she had what I later learned was what her doctors call hospital induced delirium which I'd never heard of before and it's apparently very common especially in older people and the name is immediately suggestive of people actually don't know what what's going on at all. It's sort of a name straight out of the 18th century it sounded like to me but it's a severe disorientation but also a change of personality. She didn't recognize me. she thought I was somebody else and appeared to be a very different person.

That resolved but but yes in the in the years since then it's it's been a continual process um in which you know she and I have had to adapt to very different circumstances. So there are many ways in which a person can continue to be the same person even if they no longer know much about who they are or where they are, who other people are.

And for me that's been, you know, I think that's been a useful strategy. It it it helps me recognize that, you know, there's a there's a deep continuity, you know, underlying these these fairly dramatic changes, but there's there's nonetheless a continuity. And of course, the same is true for us. You know, we're we're changing too, but we just don't experience the change in ourselves um because we, you know, to cut the long story there, very short, when things change very slowly, we tend not to perceive them as changing.

I find that to be so profound and so comforting. It's impossible to lose it because it is a continuous transformation through the years.

That's right. It was never there in the first place to to be lost, right? It's always been this this process. And um I think it's it's important just talking about these things to just to point out that these these ideas have of course been central to many spiritual traditions. you know in in Buddhism um in a lot of meditative practice in in in Hinduism as well to some extent the idea of the self as process as identity as sort of multifaceted as constructed I mean this is not news to many people from different cultures and what I find quite fascinating is is the the confluence the convergence between these different ways of thinking and it's not that it's not that just science is basically telling the same story but 2,000 years later it's telling a different story that that it's a story in which what we are learning from the neuroscience and the philosophy modern philosophy about the self I think enriches the stories that were already there but also vice versa I think understanding consciousness that's part of the battle we come with all these preconceptions about what it is that we're trying to understand but actually the experience of being a self is not simple And when we widen the lens to other cultures and other traditions, I think we get a richer view of what consciousness research should be about.

I feel like it would be professional malpractice to have had a conversation about consciousness and the self and to not ask you about drugs, hallucinogenic drugs and also legal uh anesthetic drugs, right? Like

how does the fact that I can be put under to undergo an operation and wake up and have no memory or any possible way of accessing that time, how does that affect your ideas about consciousness? And then relatedly, if I can take LSD or hallucinogenic mushrooms or any of these other types of substances and change my experience of the world, how does that affect consciousness?

The more hallucenic drugs in particular psychedelic drugs for me anyway emphasizes the intimate connection between consciousness and the brain. You take a different chemical now interfere in the brain's business with a different kind of electrochemical manipulation pharmacological manipulation and now instead of losing consciousness it changes and it changes extremely dramatically.

So I you know I find this very very good uh evidence is highly compatible with a sort of view that consciousness is something the brain does. You know you intervene in the brain and consciousness changes. Interestingly you know you can take it in a very different way. You could take the experiences that you have on psychedelics as some sort of insight into the nature of reality and come to a very different conclusion that oh look you know I've experienced um that consciousness is in fact a fundamental property of the universe and so it doesn't depend on the brain at all. It all depends on your prior what you come into it with. For me it sort of reinforces the dependence of consciousness on the brain. But I think in each case um psychedelics can show well for well maybe not in each case but certainly from the perspective that psychedelics change the brain and that changes consciousness.

It's a it really underlines that what we experience is is a construction because you change aspects of brain function aspects of our conscious experience that we might otherwise take for granted. You know, we we can realize are things that the brain is doing um because they're changed or or they go away. So for me it's a very in it provides a lot of insight into those aspects of of consciousness which need explaining and that's entirely separate from all the the potential therapeutic benefits which I which I think are also very exciting very interesting. I think the jury's is going to be out for a little while on their on their overall efficacy. Um but there's there's a certainly a lot of rich potential there.

A perfect place to end. Thank you so much for being on the show. Thank you for your work and and thank you for taking the time to explain it to us.

No, thanks Chris. It's been a real pleasure. Thanks a lot for having me on the show.

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