309 | Christof Koch on Consciousness and Integrated Information

Hello, everyone. Welcome to the Mindscape podcast. I'm your host, Sean Carroll. Despite multiple episodes here on Mindscape devoted to the topic, we have still not figured exactly out what consciousness is or how it works. We've had philosophers on... talking about what it means to have an experience. We've had neuroscientists talking about what happens in the brain.

all to no avail. It's not that there's not been progress. I'm slightly tongue-in-cheek here, but this is a hard problem. What exactly is consciousness? Because it's one of those things we're very, very familiar with. But it's kind of unique in that we're most familiar with it from the inside, right? Rather than at an objective stance, measuring things with calipers or microscopes or whatever, we're experiencing it all the time. That's an opportunity.

also creates certain unique problems. So today we're talking to someone who is a neuroscientist but is also very, very willing to mix it up with the big philosophical questions. Christoph Koch is currently at the Allen Institute for Brain... Science, where he was originally the chief scientist and president of the Institute. Before that, he was a professor at Caltech for quite a while. In fact, I met Christoph when...

Believe it or not, we were both consulting on a movie, and the idea of consciousness came up, and the idea of consciousness in a computer came up, and Christoph pulls out his iPhone and points to it and says, know this isn't conscious.

At the time, I did not take that seriously, but now I understand the issues a lot better, and I know that he was gesturing toward the idea of panpsychism, which we've talked about before, of course, on the podcast. And Christoph is not quite a panpsychist, but he's panpsychist.

panpsychist adjacent as a proponent of the IIT, or integrated information theory, approach to consciousness. It's a very down-to-earth theory in the sense that there are numbers and equations, and you try to measure the connectivity. and the integration of the information in some system. The system might be a human brain or it might be an AI system or it might be a pile of rocks on the beach. You can measure its integrated information. But the point is you always get some numbers.

And Christoph's point was, well, that number is not going to be zero for most systems. It might be very, very tiny, nothing like what we consider to be consciousness, but maybe you can talk about it as a wee tiny bit of consciousness without actually saying that...

electrons have feelings. So this is years later and a lot has happened and we're going to talk about a number of things that Christoph has done. He's been very involved in figuring out, ever since his early work with Francis Crick, what are called the

neural correlates of consciousness. So forgetting about what consciousness is, what is it that happens in the brain at the level of neurons when you're having conscious experiences, doing very down-to-earth experiments in the brains of... mice and seeing how maybe that can be extended to human experiences and then developing tools to understand is someone in a coma. conscious, is an artificial intelligence, large language model conscious, and so forth. His most recent book...

has the interesting title, Then I Am Myself the World, What Consciousness Is and How to Expand It. So he's gotten into the questions of, you know, again, from the personal first-person perspective, are there things we can do through meditation? other forms of enhanced awareness to improve our own personal level of consciousness. So Christoph is happy to be provocative about many things. We cover a lot of ground in a short conversation. I think you're going to find this one amusing. So let's go.

Christoph Koch, welcome to the Mindscape podcast. Thank you very much, Sean, for having me on Mindscape. You know, you've been doing this for a while, going back to your collaboration with Francis Crick after he moved from molecular biology to thinking about consciousness. I wanted to start by just asking... What is the major way, if there are any, that your views on what consciousness is and how it works have changed since you started thinking about this? Also, when Francis...

And I started back when I was a young assistant professor at Caltech, partially overlapping with you. Consciousness was still a complete no-no among serious working day scientists, particularly if, like me, you hadn't obtained the holy state of tenure yet. And so it was something that you did after hours and where grad students who are always in the know, they routinely roll their eyes when, oh, yeah, that topic now, right?

And then what we instituted, this purely empirical, pragmatic program, okay, let's forget about the philosophy because we haven't made much progress over the last two millennia there. Let's focus on what we can do. So we talked about certain model systems.

in monkeys, in people, of course, in mice, how to go about it, which techniques to use, which visual illusions to use, and what are some of the basic questions. And that really caught on this purely empirical program and led to what's now known, the search for the... ncc or the neuronal or the neural correlates of consciousness in other words what are the footprints in the brain for any one conscious experience like right now i see you

And I hear you in my head, this voice inside my head. Well, nothing in physics right now tells us why there should be voices or sights or smells or feeling of being angry, upset in love, right? Nothing in quantum mechanics, nothing in general.

relativity, nothing in periodic table of chemistry, nothing in the endless ATGC chatter tells me that we have these things, these voices, these experiences. And so the search for the NCC is neutral with respect to your particular philosophical metaphysical underpinning as long as you believe and not even all philosophers believe that consciousness is something that needs to be explained

Some philosophers, most famously Dan Dennett and the Churchlands, they claim it's all a big confusion. It doesn't really exist in any sort of way that you and I believe it exists. It's just a big distraction. But among the vast majority of people and even the majority of philosophers, it cries out for an explanation. Looking for the footprint is an empirical program.

However, and this is also what has changed since I worked with Francis Crick for 14 years. Let's say in the fullness of time, we will have an explanation about the neuronal footprint. Anytime, Sean, that you feel bored, the feeling, the experience of being bored, it feels like something to be bored, right? Very different from being in love.

We know ultimately we will know it involves these neurons or maybe that mechanism or maybe even the collapse of the wave function, whatever it is. But then, of course, you want to know, well... Why this mechanism and not that? Why these neurons here and not those neurons? If it's a collapse, why should the collapse feel like anything?

This is, of course, also known as a heart problem by David Shalmer. So ultimately, we need a theory of consciousness that precisely gets at the question you asked early on. You warned me, you're going to ask, when... Is a fetus conscious? And if so, when? Is a machine ever conscious? Is a particle ever conscious? Is a paramedium ever conscious? So for all of that, you need a theory of consciousness. You need an empirical, verifiable, scientific, objective theory.

that tells us which bits and pieces of matter, which bits and pieces of organs like this, the most complex piece of matter in the known universe. have feelings and and francis and i we we purposely didn't go there but that of course was was you know 30 years ago and so in the meantime we have theories in particular

one of the two most popular theories, Integrated Information Theory of Consciousness, that Francis would have liked because it's causal. And in fact, he met the originator, Giulio Tononi, we had lunch. He came over twice to have lunch with Francis and myself at his house. So that's the biggest difference.

And perhaps the metaphysical assumptions, but we can leave that for later. We might get there. So in other words, from the start, we're looking for the things that happen in the brain that correlate with the conscious experience. you're more taken with the idea that that's important, but also we need a theory so that we can ask about things we can't immediately quiz, like the fetus or the AI.

Yeah, exactly. We right now completely depend on our intuitions, our religious or philosophical biases, right? For some people, of course, the fetus is conscious, right? Way back to inception, other people... and say, no, it's only born, only when it's born to, you know, it's a dog conscious. I know you're a cat lover, a cat conscious. How far does consciousness go down the tree of life? All of that right now, we have intuition. Everyone has a difference.

intuition. But that's not good enough, right? We all have the intuition that whales are fishes. Well, it turns out actually they're not fish, they're mammals. Well, you mentioned the idea that you're...

talking to me, you're seeing a little picture of me, you're hearing what I say. What is the distinction between consciousness, which seems so laden and philosophical, with simple awareness of things? Are they the same thing? Yeah, so for us, so Francis and I wrote about it explicitly. For us, they're just different words. Some people, particularly early on, now you can use consciousness even in nature and, you know, in PIL. You couldn't do that 30 years ago.

you're roger penrose so people use the softer thing awareness awareness is just a more generalized sort of you know you're aware that you're alive you're aware that you're awake you're aware of you know that that you know there's a president here so it's more background consciousness but it's all about ultimately you can also call it mental states subjective states phenomenal

you know philosophers like to use the word phenomenals all the same this it feels like something to be alive to be awake to be bored to be hungry

And how much progress have we made on the literal neural correlates? Do we know which little neurons are firing when I'm hungry? When I'm feeling the feeling of being hungry?

Well, even if we knew, of course, we know a lot about neurons and we know a lot about brain areas, but those are, of course, all correlation. Yeah, so we know, I mean, there are hundreds of experiments. Right now, I see you and you see me, so we have a pretty good... understanding what are the neural pathways involved in vision.

vision because it's the best studied modality of all but of course that's different from that's just correlation which of those bits and pieces are actually necessary so for instance the eye clearly you know photons are entering my eye And then I transformed ultimately into vision. Do I need my eyes? No, I can close my eyes and I can see you still ghostly. And of course, tonight, if I dream about you, you know, I dream in the dark and my eyes are closed. So I don't need the eyes.

the challenge has been to sort of disambiguate mere correlation from what is actually the causal agent. And there it's still very controversial.

You may have heard I had this famous bet with the philosopher Dave Chalmers 27 years ago now, where after a late night pub call in Bremen at a conference on consciousness, you know, he challenged me, he says, look. even in a quarter of a century which you know i was we were all much younger seemed forever We won't find these. It's going to take us much longer. He didn't say it's impossible. He agrees the NCC is a purely empirical, operational, defined...

project with enough people, money, funding, research, we will figure it out. And so we had this meeting two years ago where it turned out as part of this adversarial collaboration. The Templeton Foundation started this cool project where they pitted the two dominant theories of consciousness, integrated information theory and global neuronal workspace theory, directly against each other.

We're a little bit like, you know, the famous experiments 1919, you know, predicting, you know, the solar eclipse, doing the solar eclipse, whether the shift of light follows Newtonian physics or Einstein. general relativity, we directly pit the two theories against each other, trying to resolve empirically, well, where is it? What are the empirical predictions? Which one is actually true? And so at this meeting in New York in May of 2023, the agreement was, well, none of the theories are...

Totally correct. At least the empirical manifestation of these theories in the brain with respect to where is the neural correlate. So IIT says the neural correlate is in the back, the sensory cortices.

Well, global neuronal workspace makes the argument it's primarily in the prefrontal cortex, a part of the brain that's most expanded in humans compared to other mammals. And the field still hasn't... settle down on that that paper is finally coming out in nature in a couple of months from now okay because there was a lot of controversy about it it turns out big surprise here sean it turns out

People who work for 20 years on a theory, then if you go into this adversarial collaboration and the theory or some of its prediction is disproven, they don't just say, ah, you got me. My theory is wrong. I admit 25 years of my life was wasted. Sorry about that. I don't believe it. Yes, people actually don't do that. Surprise, surprise. Newton wasn't around in 1917, 1919. Otherwise, he would have objected again.

So we still haven't converged, but we're getting closer. And what we do realize, what came out in this debate, that the prefrontal cortex... and this is relevant to your other question, are computers ever going to be conscious, is much more closely associated with doing, with planning, with intelligence. This is the difference between consciousness.

and intelligence, right? Also artificial consciousness and artificial intelligence. Consciousness is ultimately... about being, being in love, being happy, being angry, seeing things, hearing things, etc. Well, intelligence is really about... short-term, medium-term, long-term planning to act, right? I have to save money now in order to collect it or retirement, right? That's an intelligent action. So ultimately, that's about... doing stuff function it's about functions etc

And that's different from being. And so, therefore, it's not that surprising that the parts and bits of the brain that are involved in planning, in reasoning, in thinking, in moral reasoning, in decision-making are different. different from the bits and pieces of the brain that seem to be the substrate for feeling, for having experiences. Well, I love the idea of the adversarial collaboration. I think it should be...

more widely adopted, although some adversaries would just not be able to collaborate, in my experience. So congratulations to you folks for being able to do that.

But now I need to ask this question, even if it takes a long time to answer. What are these two theories? What is integrated information theory, global workspace theory? I had never heard the idea that they focus or they propose different... parts of the brain as being central for consciousness.

Well, I mean, that was a good thing that came out of this meeting. Well, let's step back. Most people, in fact, I just attended just before a meeting at Google, I mean, virtual at DeepMind in London, about what's called computer...

computational functionalism and consciousness. So most people who study consciousness, particularly everyone in AI and big tech, makes this philosophical metaphysical assumption that was proposed formally by Putnam, the American philosopher, called a Turing functionalism or computational functionalism.

Consciousness has one or more functions. Let's call it planning or summarizing the current state of the world in my mind and acting on it. You know, long-term memory, broadcasting information in the brain. probably a list of functions. And any... Any system that implements these functions will therefore be conscious, including a Turing machine. So if we can get a Turing machine to mimic everything that people do that seems to involve consciousness, like talking about consciousness.

consciousness and reasoning based on it, then machines like large language models will also be conscious. And so now it's just a practical question we can discuss. Is, you know, ChatGPT 4.0? Is O3? You know, is DeepSeq? is Gemini. Are they conscious or are they still missing? Well, maybe they're still missing a little bit of something. Maybe they have to take in more tokens to do a little bit longer memory or whatever. But it's really just a question around pragmatics.

So that's computational functionalism. So ultimately, consciousness is a computation. It's a hack. If a program machine, it's substrate independent, it can run in the cloud, it can run on a quantum computer, whatever. It's a clever hack. And once you instantiate this hack, of course, these machines are conscious. You can ask them and they talk about it at a great length. as they are, how they feel. That's according to that view, the Putnam view.

The partner view, which is very, very prevalent. And of course, it is a dominant one in the industry. And I get it's so dominant because if you interact with an LLM, they seem incredible, not only intelligent, but also... So, yeah, they talk about feelings. Aware, yeah.

Now, of course, they talk about feelings because they've been fed on every novel humans have ever written. And all novels are about the feelings of the protagonist, right? Their love and hate and being slighted and being insulted and hurting and et cetera, et cetera.

And they've ingested all of that like vampires. So, of course, they can reproduce it. It's all deep fake. That's what I believe. OK, so the other theory on the other side, there's really only one dominant theory, which is integrated information theory.

which says, no, consciousness is not a clever hack. It's not a computation. It's not a process. It's not a function, although it may be associated with all those things. Ultimately, consciousness is, as I said, a state of being. It's a structure in a very high dimensional causal space. So ultimately... Consciousness is about a system, a substrate like this brain having causal power upon itself. And this is the particular...

way the system acts upon itself, in other words, can determine its own future and be determined by its past, I can unpack that, the more this system feels like something. So it's a little bit like saying complex systems. that can act upon themselves, in other words, that are not just randomly determined where the next state is a function of the previous state, any...

Any such system, if you look at the mathematical formulation in terms of its transition probability matrix, has what's called causal power. The current state... co-determines the next state. There may be some noise, so it may not be fully deterministic, but determines the next state. Or the past determines the present, and the present determines the future. The more internal causal power the system has to... to determine its own fate, the more it is conscious.

And the theory describes two aspects of it. It has a number called phi, the Greek number phi, which you can also think about the irreducibility of the system. The more the system is above and beyond the sum of its part, the higher the phi, the more it is conscious. So you can have a system that's phi zero, which means it's totally... It does not exist as a whole. Its irreducibility is zero.

It's not really a system. It's more too independent system. That system wouldn't be conscious. The higher the phi, the more conscious the system is. And most importantly, and this is never stressed by other theories, it... You also have to have a theory that tells you why does being in love feel the particular way it does? Why does time flow? You know, we all experience time as flowing forward. It never moves backward. Why? Space.

You know, whether it's visual space or seen space or heard space, feels extended. Well, what is it about the underlying substrate that gives rise to the feeling of extendedness or boredness or, you know, being bored or being angry? So the theory also explains by the structure of this unfolded causal space why one experience feels the way it is, very different from any other experience. And so...

Is the global workspace theory the sort of descendant of the functionalism of Putnam? Yeah, okay. Sorry, you asked me that. Yeah, so global workspace is a computer science metaphor from the 50s, right? The idea is you have a central process and that writes information on a blackboard. also called the blackboard architecture. And then every local processes can access this blackboard. So the idea here is my brain does many things, but unconsciously.

You and I, like all humans, we move our eyes four times a second. The regulation of eye movements is very sophisticated, highly controlled, but it totally bypasses our consciousness. Just like the way I adjust my gait, I move my hands, I sort of infer syntax. We speak in correct sentences, but we don't constantly put those things together. It just happens. Those are all local processes.

Every information that's conscious is globally accessible. What's meant, and I think it's a correct insight from psychologists, once I'm conscious of something, oh, there is something funny over there, then all... the different processes in my brain are informed about it. I can put it into long-term memory.

I, of course, have it into short-term memory. I can use that information. I just became conscious of to do long-term planning. I can think about it. I can reason about it. So that's the idea that once information... becomes global, it's accessible to all the information processing system in the brain, and that's what consciousness is. So the metaphor is really, you broadcast information. And Stan DeHaan and his collaborators.

have identified a set of neurons that are situated in the prefrontal cortex that project the information back to the rest of the brain. So that is this broadcast. So the claim is every time information percolates... from the visual system that starts at the back of your brain, propagates forward, is still local, is still local, then reaches the front of the brain, and then that information, if it's important enough and we attend to it, becomes... It's broadcast to all the rest of cortex.

to the neocortex, the outermost layer of the brain, that act of broadcasting, that function is what constitutes consciousness. So any system that instantiates that...

that broadcasts will be conscious. So if I understand it correctly, then the global workspace theory seems to focus on the spotlight of attention that consciousness involves, whereas integrated information theory, IIT, is more... about the integrated information that we use to plan and control our own destinies.

Yeah, but it's not just destiny at a high level, you know, at a high level. It's just looking out. I mean, causal power is just the ability of, you know, let's see, some elements, whether neurons or transistors or whatever, to influence. Electric charge has extrinsic causal power, right? Because a positive charge here has the ability to influence the negative charge over here. Gravity has causal power due to curvature in space-time. So those are examples of extrinsic.

causal power intrinsic causal power is just you have a you have a little cellular network of neurons or cells or or transistors whatever and

If these elements are in this state, then the next state will be this. And if they're in that state, then the next state will be something else. So causal power is something you can actually evaluate if you have a complete... mathematical description of a system, how its states evolve over time and how the individual elements influence each other, you can fully compute, explicitly compute all of its causal powers.

So it's not an airy-fairy. It's an operational. So in that sense, it's very operational. It doesn't appeal to anything mysterious. So it's not dualist. Some people say IIT is dualist. Well, it's not because it doesn't appeal to any substance. It's just the claim that fundamentally... What experience feels like is this unfolded causal power. So any system that is integrated, that's more than the sum of the individual parts, maybe even a very simple system like a paramecium.

Well, because of its vast complexity of the, you know, in the parametrium, there are probably a billion different molecules of maybe a thousand or two thousand different types, you know, proteins, et cetera. They all interact causally with each other. And this causal interaction feels a bit like something, like being alive maybe. So this is why you are not, you know...

running in fear from the idea of panpsychism, even though you're not like a full panpsychist, but you kind of get why that would be a way of thinking about things. Consciousness is not something that... pops up at a threshold. It's like there's little bits of it everywhere. That's correct. I mean, that's entirely correct. It's also parameter free.

You don't have to say, well, if phi is 42, then you're conscious. But if below 42, sorry, you just didn't make it. Because that seems totally arbitrary. I mean, why 42? And particularly if you're bought. So, you know, I'm also bought. So we study mouse brains that are, you know, a tiny fraction the size of human brain, in fact, almost exactly a thousand times. Yet if you look at the hardware, it's almost impossible.

If I focus in with a microscope on a tiny quinoa-sized grain of mouse cortex, it's almost impossible to tell it apart from the human brain. And so there's no doubt you can go. even down to smaller animals, that if you just observe animals, they have complex behavior, they have memory, that is quite likely that all animals... certainly animalia may well feel like something. And this is, of course, this very ancient intuition that's called panpsychism. But you would...

I should phrase this as a question. Would you classify yourself as a physicalist? Do you think that it's just physical stuff? There's no spooky essences involved here. Well— So something that's always bothered me about physicalism from way, way back is the mental is clearly not physical. My state... of seeing, of being, or thinking, or whatever, is not physical. By definition, it's phenomenal. In fact, Schrödinger, so I was recently rereading Erwin Schrödinger, right?

And he makes this very explicit that... Even as a physicist, I have to look, I have to experience the trace on an oscilloscope. Well, it means I have to see. That's a conscious experience. I have to hear other people saying something. When, you know, like Einstein, I'm... imagining some you know the elevator and free fall etc well i use my imagination that's consciousness so we cannot escape everything we have the only thing sean we have access to

The only thing is our experiences of the world. I don't have access to atoms. I've never had. No one has. Yeah, you can show me little pictures. You can show me equations that are compatible with atomism and all of that. But you don't have. direct access all you have access to is the phenomenals all these beautiful shapes painted on the inside of your cage that you call your reality that's your bespoke reality right that's the only thing

everyone knows of. That's the only thing philosophers have a phrase you are directly acquainted with. So physicalism... It's an additional assumption that says, well, there's not only these phenomena, but then I infer there's something above and beyond. So now inverting that and saying, well, now I'm going to do away with this observer altogether.

So there are no phenomena. Everything is physical. It's always struck me as ludicrous. But until recently, you couldn't say that in polite academic society if you wanted to remain a scientist. You can't say that because then people say, oh, now we're talking about... woo-woo, right? Yep, I would say that, but I'm glad you're liberated. I'm glad that you feel the courage to admit these inclinations. Yes, in fact, I have, after a particular type of experience I had, I...

Became reacquainted. So I grew up obviously in a Germanic household. And so I grew up around not only Richard Wagner, but also Arthur Schopenhauer, who is probably one of the best known, at least modern Western idealists. And now there's a resurgence in philosophy, not only... I mean, perhaps psychism is becoming more popular now. But idealism, good old idealism. And so I'm thinking of this computer scientist.

I think I would warmly recommend you interview him. Very smart guy, computer scientist and philosopher. He has two PhDs, Bernardo Kastrup. who has this, he calls it analytic idealism, which is really sort of Schopenhauer for the modern world, where essentially he says, well, the simplest explanation...

We can all agree following Occam's razor and all of that. The simplest explanation if we only postulate one thing. Well, the only thing I have directly acquaintance with is phenomenal. It's phenomenal all the way to the horizon. Because that's the only thing I and you ever know. So then everything is phenomenal. And in fact, the physical has to be explained within, is ultimately arising from the phenomenal. That even the physical stuff like atoms and charges and brain.

you know, elementary particles and quarks and whatever you have ultimately has to be explained with respect to the phenomenon. And then this philosophy now meets... Foundational physics where, you know, ever since Bell's inequality and the entangled, you know, particles and, you know, Einstein's spooky action at a distance, we now know there may be no truly observer independent.

And then maybe the observer has to be right there, central part of physics, including maybe saying, well, that's really fundamentally what truly exists. Because here's one point, Sean.

which is really central to IIT. IIT distinguished between absolute existence and relative existence. Absolute existence is existence for itself. You exist for yourself. Tonight, when you're going to go to sleep three hours earlier than I am, you will, particularly in the early phase of your night, of your sleep, you'll go into deep sleep.

So if I awake you during your deep sleep and I ask you, Sean, Sean, wake up. Where did you just come from? You would say, typically you would say from nowhere because you were deep sleep. You know, these delta waves are crisscrossing your brain. You were not there. You were not there to yourself. Your partner, your...

You know, your bad partner can definitely see your body is there. So you are there for others, but not for yourself. Then later on, as you continue to, as your body continues to sleep, you'll wake up inside your sleeping body and suddenly you are something. You are, you know. flying you're meeting long lost you know dead friends lovers pets whatever you're dreaming it's a conscious state and so this cup

only exists for others. This cup does not exist for itself. Only conscious creatures, only conscious system exists for themselves. So that's really the fundamental gap that runs straight through everything. Are you on this? Do you exist for yourself? Or do you only exist for others? You can see that is the most critical distinction there is. And so that really puts the onerous on the phenomenal, on experience.

This is great. It's wild stuff. I'm very glad you're saying it. I could not possibly disagree more with everything that you're saying, but I love it. Wait, wait, wait, wait. Okay, why? Why? Why do you disagree? I'm a physicalist through and through. I think that quantum mechanics doesn't say what you say it says. I think that as scientists, we take in data from the world, from the phenomenal experiences that we have. That's absolutely true. Completely agree with everything you say.

say that, of course, we, by construction, we get what we get as our phenomenal selves by— construction, but then we use that to make a hypothesis about how the world works. And the best hypothesis we have is the true existence of a physical world of which we are emergent parts.

Okay, so I've no trouble with the hypothesis. That's, of course, what I do every day in my daily work, you know, studying brains. But I guess we can differ to what extent... quantum mechanics now reintroduces the notion of an of or is thinking of getting rid you know there was this paper in nature physics a year ago by howard wisman and people from australia right questioning the absolute the absoluteness of events, that facts, there are no observer-independent facts.

Now, I agree that hasn't been resolved. You know, it's ongoing. But that's always been a challenge for quantum mechanics to say what is the fact and what facts do not depend on an observer. Well, I think that this is one of the difficulties in understanding quantum mechanics, because it's the one theory that we have in physics, putting aside consciousness and psychology, etc. But in physics, quantum mechanics is the one theory that...

introduces the notion of an observer when it gives you the rules of the game, right? I just wrote my own paper in Nature that appeared a week ago, you know, sort of... Rehearsing the history of this. I'll send it to you. Oh, yes, please. But, of course, there are, since the 1950s, straightforwardly physicalist models that explain why.

observations in quantum mechanics seem to be special without making observers a part of the fundamental ontology. And then it's an empirical question if and which of these models are actually correct. I agree. Ultimately, it's an empirical... Well, the metaphysics, of course, for better or worse, is immune from verification or falsification, right? The metaphysical interpretation, yes. Ultimately, it's an empirical question. What is the best...

theory within, is it a psionic theory, a Bayesian theory, or many-world theory, etc., within quantum mechanics. Yes, I totally agree. Yeah, I mean, my inclination, and I'll try not to go on too long, because there's so much good stuff I want to talk about, so otherwise we should have a whole separate conversation.

My impression is that assuming physicalism and deriving mentality from it is enormously more productive scientifically than— biting the bullet of idealism and trying to derive the physical world from that. I grant you that, but that's a purely pragmatic consideration. And I want to know before I die, I want to know what is the true state of the universe, not which is the most pragmatic state to hold.

Right. Well, that's an interesting distinction right there that we could talk about. But good. Anyway, I completely am on board with the idea that idealism in its modern guise is, you know, an intellectually... way to go, whether it's epistemic approaches to quantum mechanics or idealism or panpsychism, etc. I'm just not going there. That's why I'm very glad to have such an articulate spokesperson for the idea.

Without getting too distracted then, you can probably anticipate I'm going to ask a question about former Mindscape guest Scott Aronson's famous objection to integrated information theory. Great thing about IIT, everyone agrees, is that it sticks its neck out. It has a quantitative thing. It says this. This is the thing we're going to compute, this number phi. It's going to help tell us where the consciousness is. And Scott's objection is that he can come up with examples of things that...

on face value don't look conscious at all, like a large rectangular array of logic gates, which have a huge value for this number you're computing, but don't seem to map on to our intuitive view of consciousness. So what is your response to that? Yeah, so he's correct. IIT, like any good theory, if you extrapolate it, makes some rather strange predictions. In fact, I would argue this part of the brain, the...

The posterior part of the neocortex that empirically seems to be like the substrate of consciousness in mammals, including humans, is like a very large array. Not of neurons, and you can approximate neurons as a particular type of logical array that have a topographic connectivity. So very, I mean, not unrelated to the type of arrays that he postulated.

Yeah, so I think he is right. There's some very non-intuitive predictions. And so now we have to do the science. This has always been the case. You know, people way back argued, you know, at the time of the Greeks and, of course, in the Renaissance, that... The earth cannot be a sphere because people would fall off. Of course they fall off on the other side. That's the most ridiculous things. You can't be on the backside of a sphere without falling off, right?

So we have to be careful with things where we think, well, that's so ridiculous. Sometimes we have to take things seriously, like black holes, right, that were also left. you know, people laughed about them and then actually try to do an experiment to see, is it true? So for instance, Sean, people can now start to build cerebral organoids. You've heard about mini brains in a dish, right? Yeah. So in principle, in 10, 20 or 30 years, we'll be able to build them like...

Very large tissue. So if I were to take your or my neocortex, the outermost layer of the brain that's really most closely associated with vision and consciousness and intelligence in us, it's really a pizza-like tissue. It's two to three millimeters. thick like a pizza and it's 12 to 14 inch across and it's highly folded and you have two of them left in right brain so in the fullness of time in 20 30 years people will be able to grow these things in a dish

Yeah. I mean, it seems sort of ridiculous, but I think that's going to happen because you can reuse it to fix. Let's say if you have Alzheimer's or some other pathology, you can fix it. Well, in principle, this piece of tissue may feel like something. Maybe it just feels...

It feels a vast spatial extendedness, like you get during certain meditative states when the meditators just talk about this vast luminosity. So consciousness may end up being found in very... strange spaces and we have to the only way we can verify any theory of continents is in us in you and i and other people and once we have a theory verified then we have to go where it takes us and

Okay, so your answer is to bite the bullet and say, yes, these examples that don't seem to map onto our intuitive idea of consciousness should nevertheless count as conscious. That's... And conversely, things that look very conscious, like LLMs, same logic applies. We have to test, are they really conscious or are they just faking it? Has anyone computed phi for an LLM?

Yeah, so there's a paper that's on BioArchive now that we're trying to submit that shows formally within, so this is only assuming IIT is true. Yeah. Because it's very formal and it's very specific. So what we can formally show, you have a simple model of a von Neumann machine. okay it's a it's a very simple with 116 gates or something like that and you can show you can show an actual i mean it's it's all simulated so in one case we have a simple automata

That's heavily non-linear. In the other case, we map this automata onto a simple... but perfectly general 4-bit computer. And you can show that the input-output state of these two systems, here a physical set of four nonlinear gate, here 160. 16 gates as you would typically find them in a von Neumann architecture. Functionally, they're totally equivalent. They perform the same input, give rise to the same output. So you cannot distinguish them. So by Turing, they're exactly the same.

But you can show phenomenal. This has some causal power. Well, this one doesn't exist at all at the level of the whole system, 116 gates. And only a very small subset of them have a tiny bit of... causal power. Why is the difference? Well, because machines, so in a typical CPU, one transistor will talk to two or three other transistors. But then, of course, you have endless billions of these transistors arrayed to give you universal logic.

while the way the brain is wired, you have one neuron gets input from 50,000, projects to 50,000 with heavily, heavy overlap. And so the...

this notion of causal power is radically different in one from the other. So you can show functional equivalent does not equate to phenomenal equivalence, including in the limit. You have two systems that are functionally identical. This one is highly conscious. This one isn't conscious at all, which I think is the case for LLMs. You can't do such a proof for neuromorphic computers.

nor for quantum computers. So it may well be that you can build. So there's no question. IoT says there isn't anything supernatural about the brain. So clearly you can build. artifacts that are conscious, but just not the way we build them today, not the computers running in the cloud. Are you at all sympathetic to the idea, just to finish up the Scott Aronson conversation, that IIT...

might be better thought of as a necessary but not sufficient condition for consciousness to happen. Like if you don't have this integrated information, this high quantity phi, you're not conscious. But just because you do doesn't mean you are. If you're not representing the world, if you have no semantics, etc., then maybe we shouldn't count it as conscious.

Well, okay, so A, you can perfectly well, and in fact, we've done this, there are a number of papers where you can evolve, you know, in a computer, you can evolve simple creatures that have hi-fi that represent the world. in a sense that there's a mapping between, you know, these are creatures that you have 10,000 of them, you let them run through mazes, you collect the best one, you perturb the genome, you give rise to another brain, you send them through that, you do that.

thousands of times, you start with randomly connected brains and you end up with brains that have mappings from the outside, the labyrinth or whatever they have to deal with onto their internal brain. So IIT doesn't... beclude in at all that there is this lawful mapping like you and i have between the external world and the visual the visual brain or the um or the auditory world no you can i mean who knows you know i i cannot

think about the space of all possible theories. But within IIT, in fact, there's a thing called the central identity as part of IIT that says your conscious experience is identical to... or can be... can be fully accounted for, that's a better formulation, one-to-one with nothing left over on either side by the totality of the intrinsic causal power. Every aspect of your experience, including every memory, every thought, every dream.

can be fully accounted for. Now this may be wrong, it's a theory, but that's what the theory states.

And I do want to get on other things, but maybe a quick opportunity to talk about like the nitty gritty of looking at brains. You've mentioned mouse brains already. Are we... Testing? Does it even make sense to ask the question? Christoph is showing us a little key ring with a mouse ring on it. Can you take the ideas from IIT and either... test them in the mouse brain or learn about the mouse brain using these ideas? And if so, how do we do that?

Yeah, I mean, the mouse brain, you know, people think a mouse, well, what's a mouse? It doesn't talk. You know, I'll never have dinner conversation with it. All of that's true. But again, if I take a grain of mouse brain, dog brain, elephant brain, human brain. Basic hardware is all the same.

It's not identical. You know, we evolved the last common answer between us and Mises, you know, 60 million years ago or so. But the components are remarkable the same to the extent that we just published a whole series of nature papers showing. The brain consists of 5,000, on the other 5,000 different types of brain cells, porcineous cells, pyramidal cells, very different types of pyramidal cells, etc. The same 5,000 cells can more or less be found in the human brain. It's just like genes.

Our genome is on the order of 20,000 genes. The mouse genome is on the order of 20,000 genes. It's all very, very similar. But the difference is, of course, in the mouse. You know, it's much easier to do experiments and for ethical reasons. There are certain questions. You can't ask the mouse about language, of course, but you can do the basic. They're highly tactile. They're highly olfactory. They're less visual. They have vision.

They're less visual than us. So there are lots of experiments that you can do in a mouse or in similar creatures that are really very similar or relate closely to experiments that people can do in humans, where you, of course, limited, typically don't access. human brain you only see it indirectly so you have to use e-gene fmi

So we are all closely related. We're all nature children. We have some specialization, like a hyperdeveloped sense of importance. That's one big difference. I don't know. The mice might. I just don't know. But then, okay, so you're... So you're now still affiliated with the Allen Brain Institute, is that right? Yes. Yeah, correct. And are...

Is the Allen Brain Institute a hotbed of IITism, or is it more ecumenical? No, no. So, you know, we are now 1,000 people. When I came, we were 100. When I was the chief scientist and the president, we went to sleep. I stepped down and now we are 1,000 people. So we focus on a few very large projects, like cataloging all the cell types in the mouse brain or all the cell types in the human brain, doing this, also doing development.

You know, what happens in a very young, immature brain as it develops? How do cell types change? What about the Atlas? We're doing these connectome projects where we do, you know, at the finest level possible where we don't image with photons, but with electrons. by cutting up tiny slivers, you know, two or three nanometers of brain and cutting, you know, millions of these slices, putting them together. So we do a few very large...

projects that typically are not going to be done by industry and can't be done at a university. By and large, we don't think too much about consciousness and such things. We leave that to academics like me or like many other people.

academics at various universities. Well, I mean, it's good. I'm very glad you said this because I think that it's fun to talk about the big picture philosophical questions. And they're not the same as, but they absolutely do rely on... this kind of empirical work where you're trying to figure out how many different kinds of neurons there are in the brain.

Totally. Otherwise, we'd still sit around like Plato and Aristotle at the Academy days, right, 2,400 years ago in Athens, and shoot the breeze without ever making progress. But that's a great thing about science, including about psychedelics, including quantum mechanics. You can ask nature the right question in the form of the correct experiment, right? And you will get an answer. That's the best thing about science, better than any other human activity.

I agree. I completely agree. And so given what we've learned and what we're still hypothesizing about, there's a bunch of questions lying out there about consciousness that are pretty... down-to-earth and operational. As we've already alluded to, we want to know, are people conscious when they're dreaming? Are they conscious when they're in a coma? Are they conscious when they're six weeks after conception? Do you think we've made progress on these questions?

Yeah. So, in fact, I helped start. So, one of them, very much on all of those questions, except maybe the final one. Let's come to that. So, A, I helped start a company called Intrinsic Powers. that brings a device that used to be a pure research prototype. developed by Giulio Tornoni, the architect of integrated information theory, and a close medical colleague of his, Marcello Massimini. to test for the presence of consciousness in behavioral unresponsive patients. So if you or I have...

after this conversation, a heart attack or bleeding or, you know, a car accident. We get into the ICU. We are unresponsive. We're clearly alive. We're on a ventilator. We're unresponsive. And they ask you, you know, can you hear me? Can you see me? Can you track? a flashlight with your eyes you know if i pinch you will you moan or will you move a limb you don't do any of that so you're considered behavioral unresponsive this used to be called vegetative state okay

The tragic is four to five days out, if you remain in this day for four or five days, typically the team, the medical team will initiate discussion with your loved one. Well, what did he want? It's a time to pull the plug, literally. They pull ventilator support. And up to 90%, up to 9 out of 10 of these patients die because of withdrawal of life-critical care. Okay?

Now, we do know that one quarter of these patients are conscious, but covertly conscious. So what that means, for instance, if you ask them, So you have this person lying there. You ask him, sir, imagine playing soccer for 30 seconds. And then imagine just being quiet. Again, ask. You ask him a second time, imagine playing soccer for 30 seconds. Imagine lying quiet. Then you can see, for instance, the nice modulation in your motor cortex response.

So it means this patient who's unable to communicate, where you have no idea whether there's anyone home, still can lawfully, voluntarily regulate their brain activity, okay? And so...

And together we developed this device. So essentially what it does, it knocks the brain by sending in a magnetic pulse called a transcranial magnetic stimulation. And then you measure the response using high-density EG. And essentially you complete... compute the complexity of that in iot and it turns out there's an absolute threshold 0.32 it's normalized so zero which means it's totally flat line you you knock the brain and there's no response that's brain death

Or one would mean every point, every electrode is totally independent of the other. This doesn't happen in real brains. So typically brain complexities between 0.6 and 0.8. 8 typically in you and I, for instance, right now. Or when we know, when you dream, same thing. When you're in a deep sleep, it's very small complexity, below a threshold 0.31. When you're in a dream state, your complexity is high.

When you are under psychedelics, your complexity is high. When you are under anesthesia, your complexity is low. When you're in an unambiguous coma where... it's clear that you're not there, your complexity is low. So it's a very nice threshold and with very high specificity of 0.95.

we can determine whether you're actually... So it's a primitive consciousness detector. It's the first primitive conscious detector. So again, this really shows, independent of all these idealism, physicalism, psychism, we can actually make progress on these. questions we can build consciousness detectors right now for us in the fullness of time we will certainly we can develop them for every for any mammal

and maybe in the fullness of time for any system, but right now for humans. So that's real progress. Does it help us with the prospect of brain-computer interfaces and being able to talk with people who are in a coma? No, so this is a purely device just to see is the complexity of this brain, is it sufficient to support consciousness? No, separately, you can then specifically take these patients.

and further do rehabilitation or talk about if they remain in this state. So typically what happens, so most people, the natural cause of events, people either die. or they recover some functionality. So if you remain in this state, a small subset, 5% to 10%, they become chronic. And then they're typically in a home or sometimes they get actually taken to their own home.

and they remain in this state where they have either no or only minimal, sometimes people sort of recover some ability to move their eyes, in the worst case, they may not recover at all. Yeah. And, okay, I'm sorry to hear that, but I'm glad you're doing—I mean, I'm sorry to be reminded of this terrible fact about human life, but I'm glad that you're making progress on distinguishing between the cases that really—

seem to be essentially gone and those that are recoverable. Then what about the youthfulness question? What about the fetus and becoming conscious? Is that something that we can talk quantitatively about? Well, so all we can say, and in fact, I was participating in Amicus Brief in that anti-abortion lawsuit. We know... The cortex doesn't really fully develop until the second trimester. So your nervous system develops at 8 to 10 weeks in the first trimester.

But it starts developing, but then really sort of doesn't develop the connectivity and the connectivity to the external world through the thalamus. That doesn't happen until week 22 or 24. um eg is also pretty much flat until then and then you get the first so-called birth suppression eg where you get activity and then quiet Activity and quiet and the typical pattern in you and I that doesn't happen till very late end of third trimester where you get a more normal looking.

e.g., with all the waves developing. So it's very difficult to say right now. But in the first trimester, I probably may not feel... I mean, it's very difficult to inference. As far as we can tell, it probably doesn't feel a lot to be a first trimester. At the end of the second trimester, you begin to get some simple reflexivity. So in premature babies, when they need some operation, they do already limb withdrawal reflexes.

But that doesn't, you know, a fly, a drosophila embryo does the same thing. It curves away from a source of heat like a match. So it's that reflex. It's very difficult to be certain. Is it exciting or somewhat scary to be part of an amicus brief in front of the Supreme Court? Well, it was exciting and, you know, we're trying to do the right thing.

It didn't amount to much. It wasn't decided on the merits of the scientific case, right? It was just decided, we need to send this back to the States. Okay, and then you already mentioned a little bit about LLMs and your opinions about that.

But is there, from IIT or from any competing theory, do we suggest some kind of roadmap for making artificial computer programs that truly are conscious, or is that a very far way off? Well, first, why would you want to do that? People want to do lots of things. Okay, that's true. Yeah, so you cannot simulate it. Okay, that's a big claim. Yeah, because, look, you can perfectly well simulate the black hole at the center of our galaxy, right, Sagittarius A-star.

But have you ever worried, Sean, that if you turn on this simulation, you're next to the computer program in the computer center that runs this, you're going to be sucked into the black hole? No, I have not worried about that. Why not? Where's the difference? No, I kid you not. Where's the difference? Well, the simulated test particles in the computer would be sucked into the simulated black hole. Yes.

But that's all simulation. It's a difference between the real and the simulated, right? So because this computation by itself does not have causal power to bend space-time, just like it never gets, I mean, Sean Searle made this argument, you know, decades ago.

ago it doesn't get wet inside a rain simulation right same thing it doesn't have the causal power yes so you can perfectly well even if you were to build a computer simulation of the human brain the complete human brain like you know henry markham blue brain project wanted to do that in the future we'll be able to do it but still and this computer simulation of course will wake up and speak because it's you know it can do that but it won't

feel like anything because you can't simulate it you actually have to build it so if you want true conscience you have to build it you either have to do neuromorphic engineering where you build hardware Not simulate, you actually build hardware in the image of the brain. People are trying to do that at IBM and Intel, etc. Or possibly quantum computers.

Possibly, like Willows at Quantum Compute Lab, etc. So embodiment might be very important for this project. Yes, it's not going to be substrate independent. Right, okay, good. So I don't believe, by the way, in this, you know, mind upload, right? No, I agree.

You know, that I cut my brain, I get my brain's connectivity, I simulate it up in the cloud, and then this thing will be conscious. No, it may be able to mimic me, including my accent and everything perfectly, but it doesn't feel like anything. It's a deep fake.

You're not worried about The Matrix? No. I'm worried about many things, but not The Matrix. Well, you've written—I'm sorry that it's taken this long to get there—but you've written a provocative book just last year. Do you want to give the title, or should I read it? Then I Am Myself the World, which is taken from the second act of Richard Wagner's opera Tristan Isolde, where the eponymous lovers have this union.

where i mean they make love on stage basically but they want to overcome their own self and so they have what's in modern language called a mystical experience they become they lose the boundaries between themselves between tristan isolde and the rest of the universe, so they feel they are one with the universe, which is one of the defining features of what's called a mystical experience. Well, this is what we can talk about when you're at a certain stage of your successful academic career.

about expanding consciousness now, which is certainly fraught territory. Well, yeah, I mean, yes, I've been fortunate enough to have such an extraordinary experience and it leaves you totally unmoored. It leaves you completely flabbergasted. It leaves you...

I had this when I was 65, and I thought my metaphysics, my sense of what exists, has been fully established, and 65 isn't going to budge anymore. And then suddenly you have... this ontological earthquake where literally all the plates shift and everything you lived and you

you know everything you did suddenly looks very very different so it's it's it's for sure it's a transformative experience in a sense if you undergo this there's a distinct before and after you'll never look at things the same way again which is Another defining hallmark of a transformative experience. So we're talking about some kind of psychedelics or other pharmaceuticals or a purely like meditative state. No, this was with help. Yeah, okay. But you're a neuroscientist. You know that...

You had an experience that was caused by prodding your neurons with chemicals. So how does that help you get insight into the fundamental nature of reality? Okay, so you're totally right. My brain was a substrate of this experience. I don't doubt that for one second, helped or not. But the...

So William James talks about it in this wonderful book. I can warmly recommend it to everyone to read it. It hasn't aged, has aged very well that he first wrote in 1906. You know, the father of American psychology, the varieties of. religious experience where he talks about mystical experience and he says they bring one of the defining hallmarks of them this what he calls noetic quality you know from news knowledge greek you bring back this experience. And it has...

Powerful authority over you. You cannot help but now try to seek, you know, I'm still a rational scientist in person. So what I try to do is try to see how does what I experience, how is that compatible? with my view of everything else. including science, including brain science, including knowledge that my brain was a substrate of this particular experience. So I think you can reconcile both of those things.

Look, it's a little bit like, imagine, Sean, the following scenario. No one dreams. Okay? People, you've never read about dreams. When people go to sleep, they just sleep. That's it. And you have one. Experience. One. How would that change your life? If you only had one experience, one dream experience, you know, where you met your long lost parents or friends or et cetera.

it would sort of profoundly affect you, right? Absolutely. I hope it would not lead me to change my ontological view of the world. Well, because you haven't had – look, and I take Nova, and James says this explicitly. You can't convince other people of your abuse, and I'm not trying to. This is just my experience. I do know that –

These types of experience that I write about are common in literature, common across all cultures. Lots of people in lots of different settings have written about them. So they're not that rare. It's not unheard of. And so the challenge is if you accept them, you know, if you accept them, what does this tell you about the world? And in particular, what does it tell you about the metaphysical?

the metaphysics about the world. So I can continue to do all my science, all my neuroscience, etc. But it really shook the ontological foundation, which is why I'm now much more sympathetic. To idealism, which I hadn't thought about for 50 years. Okay, so my question was going to be, so what is the shift in your metaphysics? But is that it, that you're much more sympathetic to idealism?

Yeah, because what I experienced there was effectively the world at large. There was no self anymore. Self was completely gone. Crystal was gone. There wasn't a body. There wasn't anything like that. And instead, I experienced the universe at large.

literally the galaxy i mean the universe at large yeah i know it sounds corny and all of that but that's okay but but but but that's what you experience and you're in this time there's no passage of time it's not too slow or too long this moment you know and so yeah so you run around this was at midnight on a beach somewhere in brazil and you you know you're totally confused the next weeks and months right because you're trying to fit in

You know, how does this accord with everything else? You know, I know. And then sort of I thought that Schopenhauer, I came upon this remarkable quote of Schopenhauer where he talks about 200 years ago in his book. the only book he really wrote, The World as Will and Representation, where he talks about states like that.

And as far as we know, meditation didn't exist at the time in the West. Psychedelics really didn't. He never had any experience like that. That was, of course, before we encountered opium and other substances. So he just... thought about these things. And then, yeah, I looked around at idealism, and then I came across this philosopher, computer scientist, Bernardo Kastrup, who espouses this modern form of idealism.

And in your book, you're going to suggest that people can understand consciousness better and expand it through these kind of intense experiences? I would certainly suggest, yes.

So I grew up at a time when, you know, I was heavily into... alcohol, like many of us in the West, but nothing else. But that's changed over the last 10 years. Yeah, they can reveal you. So A, they can reveal these states of self... where...

where your ego is dissolved, ego dissolution, where there's no self. And you can experience a profound beauty. Like here, I'm looking at the island, the forest, the green lush forest. You can just see the transcendent beauty of it whole. And there's no self to get in.

away. I mean, we need the South. It's necessary to do long-term planning, all of that, but it also constantly gets in the way, right? It's always about me, me, me, me, and me. I mean, look at the most senior political... personality in this country you shall remain nameless right or the two of them both of them right

And it's all about me, me, me, me, me. And so suddenly you have this experience of loss of self and you realize, well, that's perfectly fine. The universe is profoundly beautiful without me. So I think that's really an essential experience. most everyone should have and can have in a safe, if you do it in a safe manner. Now, not everyone, there are certain dangers. Some of these substances are very powerful. So you have to be very cautious.

You have to use all the proper safeguards, etc. But I think for most people, they can reveal aspects of consciousness that they haven't thought about or they have never experienced or they have never imagined. Good.

Should we wind things up by talking about quantum mechanics? Sure. It seems like a good thing to end on. Well, I mean, we've talked about it already, but you have a paper out not too long ago about the possibility that quantum mechanics does play a role in consciousness.

Yeah, so we initiated this collaboration with Hartmut Neven, who is a physicist and also his background with computational neuroscience, like me. In fact, we had our same advisor back in Germany. But since then... he's a vice president now at Google and heads the quantum compute Google group in Santa Barbara building, busy building these large-scale quantum computers.

with a bunch of experimentalists, particularly Ken Kosek, who's at University of California in Santa Barbara, and Luca Turin, who's at a university in UK. And the idea is... Well, so there's theoretical work and then right now there's experimental work trying to test it. That sort of inverting pen rows really... Penrose famously argued within his objective production that the collapse of the wave function, you have a particular system, it's in a superposition.

that collapsed because of interactions with the environment. And that gives rise to a little ping, a little bit, a little conscious moment. That's his argument. And then he got together with the anesthesiologist to hammer off, you know, microtubule and all of that. But let's divorce the instantiation of that microtubule from that idea.

It's controversial but has remained irresistible to many, many people. So we are inverting that because we are saying, well, if you have a system that consists of... two or three or more than one qubit that are all entangled, something Roger Penrose never considered, then if that's true, you could then use that to communicate faster than light information.

violating relativity theory that no one really wants to violate right so you can invert that by saying well no it is when the system goes into superposition that you create a conscious moment And if you have a system with 20, let's say, qubits, then they go into the superposition of 20 qubits. But the defining thing of consciousness is you only ever experience a definite experience, right?

Not a superposition. And so this is where the many worlds interpretation come in. I only travel down one of these branches of the two to the n possibility, you know, if I just have up-down states, two to the n... And that's the one I consciously experience. And what you experience depends on the way these interact. And here you could use, for example, IIT to explain that.

So it sort of inverts Roger's proposal. And if that's true, you can then sort of build quantum systems that could interact with your consciousness as long as you can get a system. You know, if the latest iPhone has quantum computing and is entangled with my qubits in my brain, then that would be one conscious mind. So you could expand your consciousness if you have the right technology. you

Now, it's one of many crazy-sounding ideas in the interface between consciousness and quantum mechanics. But the great thing is we're trying to test it now. And this, again, where we come back to this thing, if you ask...

the right experiment, you can get an answer. So there have been since, you know, 30 years, Klaus Schulten's work, these hypotheses that... biological system, in particular bird navigation, avian navigation, uses a quantum compass, right? In quantum, in the interaction in the eye... There you have the interaction between photons and the molecule, and this depends weakly, seems to depend on magnetic field, and that songbirds can use that to navigate across vast distances.

Ultimately, that's based on a radical pair mechanism. That's one hypothesis or a nuclear spin interaction. It's another one. So we are trying to test that. There has been one claim that xenon. So you take the rare gas xenon. It's an anesthetic. This is known.

It's actually very good anesthetic because it's rare gas. It doesn't interact much with anything. It's very safe. It doesn't burn. So it can be used in the clinic. It's just very expensive. So it's not really used in day-to-day practice. But it is an anesthetic. There's one claim there's an isotope dependency that xenon 128, 129, 130, and 131 have different anesthetic potencies.

Now, the difference in atomic mass is minute. It's under 1%. So the hypothesis is unlikely to be due to the difference in mass. But the most critical difference is that 128 and 130 has been zero. While 129 and 131 has been respectively one half and three half. So now Luca Turin is trying to test this very simple experiment in flies. In other words, if you take a bunch of flies, you put them in a tube.

So now you see 30 drosophila, fruit flies, in a tube. You introduce gas, various types, you know, different types of xenon, different isotopes dependent xenon gas, and you compress. And at some point, you see when you reach certain pressure that the flies are all immobile. They are anesthetized. And then you release them again. So you can do this experiment multiple times.

The very simple test is, is it true that this dependency, how deep you have to plunge the plunger into that vial with xenon gas until you achieve... immobility that here stands in for anesthetic potency, does that depend on the isotope? of xenon good and a different model system that we're trying to do with kankosik what about uh human these human cerebral organoids made out of human pluripotent stem cells

If you can get them, if you put xenon on, again, ultimately the tissue will... Usually these tissue, these mini-brains fire action potential. If you put sufficient xenon in... that ceases, that stops the firing. So does that the point, the precise point when that firing stops, does that depend on the isotope? Is it going to be different for xenon-129 versus xenon-130? That's the question we're asking.

It's certainly an experiment very well worth doing. I guess it's late in the podcast, so I can ask one technical question. The hypothesis that a system being in superposition is relevant for consciousness somehow, that's what— bugged me a little bit when I saw the paper, because being in superposition is sort of not an objective fact, right? That is relative to what basis you're using to describe your system. So is there a more physical criterion that we can replace for that?

No, not right now. Okay. That's why it's science. We've got to do it. Yes. Yes. Yes. What is your thought? If you had to place Bayesian priors here, do you think that quantum mechanics is super important for consciousness?

Probably not in the human brain. Okay. But it would be cool. For all the reasons. On the other hand, look, evolution, you know, it's been around since for a billion years, roughly, right? And so evolution is very clever. It's done all sorts of things. If it's not outlawed by the laws of physics, somewhere, and if it's really beneficial for the organism, then it may well have been exploited.

Would I bet my house on it? No. That's why we're doing the experiment. Yeah, that's why we do the experiment. And that's a very good philosophy to end with. So Christoph Koch, thanks so much for being on the Mindscape Podcast. thank you very much for having me sean that was very enjoyable that was very enjoyable good

What is your paper about? You said you just published a paper 10 days ago? Oh, it was just a review article for Nature, an essay about the 100th anniversary of quantum mechanics and why it's still... controversial, why it's still difficult to really figure out and get a consensus on what quantum mechanics actually says. That's right. 1925.

It's the quantum year. The United Nations has said that this is the year of the quantum. And it's not true for general relativity, right? There are none of these controversies swelling around GR. No other theory has these controversies. There's not like a whole...

subset of people doing philosophy of electromagnetism, right? Quantum mechanics is the one that... And I think it's an embarrassing situation for the physics community because we have not addressed the problem. I think that's an issue. Yeah. But it's also an opportunity. Exactly. Well, I like to say, like, I personally am very slow, so I'm perfectly happy with the rest of the community not racing me to do this. I'm trying to figure it out myself. Yeah, so please send it to me, the article.

I will do that. Thanks. Thank you. That was fun.