Is consciousness related to quantum physics? (with Roger Penrose and Stuart Hameroff)

Transcript

Why do we have the experience of being conscious? Can you build consciousness just by putting together lots of neurons in the right way? Or might there be deeper principles at work? Could quantum physics have something to do with the brain and specifically with consciousness? Is it possible that consciousness is actually something that predates biology and there's a sense in which biology evolved to take advantage of it? And what are the right ways to make new theories in neuroscience when we don't know the answers? Welcome to Inner Cosmos with me, David Eagleman. I'm a neuroscientist and author at Stanford. And in these episodes, we sail deeply into our three-pound universe to uncover some of the most surprising aspects of our lives. Today's episode is about consciousness and quantum mechanics and the question of whether there could be even possibly any connection between them. So to get at this, I'll be talking today with Roger Penrose, mathematical physicist and polymath and winner of the 2020 Nobel Prize in physics and also Stuart Hammeroff, an anesthesiologist who has collaborated with Penrose for many years on a theory.

Before we dive into those interviews, I want to set the table by saying that what we're going to talk about today are speculative ideas and many neuroscientists don't even like to go near them. But the fact is that despite the thousands of neuroscience journals and textbooks and laboratories, there are still fundamental basic questions that we don't know the answer to. And one of the most fundamental is the question of consciousness. Why does anything feel like something? In other words, imagine that you built a little toy out of pulleys and levers and switches. Would you say that it is conscious? Presumably, you wouldn't.

Now double your little toy in size with new levers and switches and pulleys. Is it conscious now? There's no particular theoretical reason to think so. Now keep adding to it. Put on another pulley and another lever and another little door and attach a wheel and keep doing this until you fill a room and then a stadium. Do you have any reason to assume that it becomes conscious and has internal experience just because it's more and more complex? If you now remove a pulley, does it feel pain? And if you put a little molecular detector on it such that it can recognize molecules of different shapes, does it have a different experience like displeasure for some shapes and pleasure for other shapes? And where is that happening? I certainly wouldn't think that your giant toy is conscious or at least let me say that I have no theoretical reason to believe that it suddenly experiences pain or hunger or longing or pleasure because it's just pieces and parts.

So this is a fundamental question about the brain. We look at your 86 billion neurons which are generally thought of especially now in this era of AI as being units that are popping either on or off one or zero. And so it's not clear to any of us in neuroscience why we have private subjective experience. And this is true whether you have 86 neurons or 86 billion or 86 gajillion of them. Why do these little electrical signals and chemical releases give us the experience of eating a lemon or the pleasure of an orgasm or the pain of stubbing your toe? Now, we don't know the answer, but here's a speculation that some people have put forward.

Could consciousness, the most intimate, subjective, elusive feature of our existence, have something to do with quantum physics? Now, this is not a mainstream idea in neuroscience. You're not going to find it in the standard textbooks. Most cognitive scientists, if asked to explain consciousness, will talk about neurons and synapses and the emergent properties of complex systems. the language will be biological and electrochemical and computational. But a few scientists have suggested a hypothesis that there's something deeper going on, something much stranger.

And that's what we're going to explore today. I'm not presenting an argument that quantum mechanics does explain consciousness, but it's worth understanding why some serious minds are entertaining the hypothesis. So we'll begin with Roger Penrose who is perhaps an unexpected figure in this conversation because he's not a neuroscientist. He's a mathematical physicist. He's done so many amazing things in his career.

He worked with Stephven Hawking on black hole singularities or you might know him for his geometrical shapes called Penrose tiles. And you certainly know him because in 2020 he won the Nobel Prize in physics for showing that black holes result naturally from Einstein's general theory of relativity. And by the way, he's also the one who mathematically described black holes in detail, including their singularity, where all known laws of nature dissolve. But especially in the 1980s and 90s, Roger Penrose turned his attention toward the brain. Not because he wanted to build a better theory about cognition, but because he had a concern about algorithms.

Penrose felt that consciousness just can't be explained by any rule-based system. He pointed to an idea called Girdle's incompleteness theorem which said look there are mathematical truths that we can see to be true but they can't be proven within mathematics. In other words, there are many systems where we can see things to be true but the system itself can't prove them. You need to somehow step outside of the system. Now to Penrose, this was a sign that human understanding operates in a way that transcends computation.

In other words, he said brains aren't just computers. And if they're not just computers, then the mystery of consciousness might demand a different kind of physics. So he wrote a very interesting book called The Emperor's New Mind, which asserted that the brain can't just be a computer. So in your book Emperor's New Mind which I read as a as a young person and really loved you. So you argue that consciousness can't be explained by algorithms.

So help us to understand that. But it really means you see an algorithm is just a sort of technical word for a computer program if you like. Maybe people use that term. It just means that you have a rule which is a computational rule. Right.

And why why what made you feel that consciousness can't be explained by algorithms? Well, it goes back to the girdle the lecture that steam gave about girdle theorem and I realized that you see if you see mathematical proof you could have a set of rules rule axioms and rules of procedure and these are of a nature that you could put them on a computer. Do you think there are forms of human insight that fundamentally cannot be replicated by algorithms? Is that that's correct? Okay. Yes. Absolutely right. Okay.

Great. And so and so that made you think that maybe this mystery of consciousness needed to be taken seriously by physicists and mathematicians. So yes, so how did you how did you start addressing this? You see, I was trying to think about the laws of physics that um we sort of understand and some of them are very powerful. Well, even Newtonian mechanics explains an awful lot. Um Einstein's general theory of relativity explains a lot more uh and it's more difficult to apply things, but it's still computational.

What about quantum mechanics? Now before we go further, I just want to give a reminder about what quantum physics is. It's the branch of physics that describes the behavior of matter and energy at the smallest possible scales at the level of atoms and subatomic particles. And down there, the world behaves nothing like what we're used to. Particles can be in more than one place at once. This is what's known as superp position.

Particles can become mysteriously linked across space. in what's called entanglement. And the most bizarre feature of all is that the mere act of measuring a system seems to affect its outcome. This is what's called the observer effect. In our current understanding of quantum mechanics, the story is that until a particle is observed, its properties don't exist in a definite way.

They exist only in probabilities. In other words, a quantum particle doesn't have a precise location until you look at it. Until that moment, it's smeared across a range of possibilities. And then those possibilities collapse to one outcome when you observe. Now, this isn't just a metaphor.

This general idea has been tested and confirmed for over a century, and it's built into the fabric of our technology. Quantum mechanics is the science that allows the transistors in your cell phone and the lasers at the grocery store scanners and the GPS in your car. Quantum mechanics is real and it's very counterintuitive. And it seems to tell us that at the heart of reality is a kind of indeterminacy, a fuzziness that only collapses into certainty when it's observed. So think of it roughly this way.

You toss a coin in the air and while it's spinning, it's not heads or tails. It's sort of like it's both at once. But the instant you catch it and look, it becomes just one. Heads or tails. That moment of catching it is like the wave function collapsing.

Now, here's the thing. In quantum mechanics, there's no way to predict what the coin's going to be, heads or tails. And so that non-computable strangeness, that's what Penrose was interested in. He wondered what if that indeterminacy, that collapse of possibilities into one real outcome wasn't just a physical process, but also has to do with a mental one. In other words, what if the flicker of consciousness is related in some way to the collapse of the quantum wave function? So back to Penrose talking about his search for something non-computable and getting interested in the collapse.

What about quantum mechanics? Then I thought, well, it's shroing equation. There's no problem about putting that on. There may be lots of parameters involved which make it tricky. But that's a well determined deterministic equation. But the Schroinger equation doesn't give you what happens in the world.

Why doesn't it give you what happens? Schroinger himself was very keen on explaining these things and his well-known cat. He was making the point this is just an absurdity to have a cat which is dead and alive at the same time is a nonsense. This is point of what he was trying to make. He was saying this is an absurdity. His equation he was trying to say he was saying roughly speaking my equation does not describe reality.

there is something more and this something more is what we tend to call the collapse of the wave function. Your wave function chugs along and behaves according to the Schroinger equation very reliably and honestly and then from now time to time it says whoops I'm going to do something else and then it becomes probabilistic and it's all hidden in all sorts of mathematical schemes. So your argument is that classical computation can't explain consciousness. And so the question is then what can and this is where you make the fascinating proposal that quantum mechanics and specifically the collapse of the wave function might be involved in consciousness. See people say sometimes I just think well here's a problem and here's a problem so they're the same thing.

It's not that. is that we need something which which is not a computable part of physics. What is it in the physics that we know that would not be possible to put on a computer? Well, you see, if the collapse of the wave function is purely random, then you could put it on a computer source off and it's not perhaps really random. It's something very subtle and you need that for the collapse of the wave function. And the story has developed in other ways beyond what I had then.

You see, this was the beginning of the story. And you're asking me about the beginning. The beginning was the story. It was a little bit feeble in the sense that I didn't know really much about what to do. I could see that in my according to my viewpoint, the collapse of the wave function had to be a major part of the physics which is responsible for evoking consciousness.

So to summarize where we are, Roger felt certain that consciousness couldn't be explained just by classical computation. Again, most of quantum mechanics you can easily model on a computer, like the evolution of the Schroinger wave function. But there's something very weird about the collapse. That's the part you can't compute. So Roger felt he was on to something interesting there.

So he sat down and wrote The Emperor's New Mind. And the title, as you might guess, was a reference to the story of the emperor's new clothes. The idea being that everyone is assuming we can explain consciousness by putting together enough neurons. But in fact, in his view, the emperor is naked. Consciousness possibly can't be explained by just a bunch of neurons.

So I asked Roger what happened just after he published the book in 1989. I wrote my book, The Emperor's New Mind, and hoping some young people might be stimulated, only got old, retired people. I thought I'd done a sort of fairly reasonable job as an ignoramist, but not too bad a job of trying to learn the main features of neurohysiology. So, Roger started studying up on the brain, really as a side gig to his mathematical physics career. But the more he looked at it, he thought that maybe the macro level at which we were able to study the brain wasn't really revealing its secrets.

But I would say that it has a genuine deep purpose and that purpose is not clearly revealed in the in the structures, but it's not something which is obviously like a computer. Something else going on, but I didn't know what was going on. I had no real idea. By the time I got to the end of my April humor, I I just I could have stopped writing in this book, but I thought, well, that's I've written so much so far, I better go on. And so I more or less thought of some idea, which I didn't really believe.

I tried to think of something that might be non-computable. You see, so that's where things were for Roger's idea. He suspected there must be some kind of quantum effects in the brain, but he didn't know where to look. But at the same time in America there was a young anesthesiologist named Stuart Hammeroff who was interested in consciousness and uh I got interested in consciousness and I went to med school and was interested in neurology, neurosurgery, psychiatry but I didn't like those lifestyles uh particularly what what they got to do. They didn't actually get to do much.

The surgeons did but the neurologists in particular didn't have much to do. And um I took a research elective over a summer in a cancer lab and studied mitosis. I figured just try something different and uh so we uh studying cell division and as you know the cells divide the chromosomes are separated by these spindles which are microtubules. That's Stuart Hammeroff and while everyone in that lab was interested in the chromosomes where the genes are he found himself interested in the microtubules. Now what are microtubules? The starting point here is that all the cells in the brain like neurons and gal cells are not empty.

Inside every single brain cell is a bustling inner world. You've got all kinds of structures that help the cell keep its shape and transport materials around. And among these structures are microtubules, which are tiny hollow tubes. They're part of the cell's skeleton. Sometimes people think of these like the tracks that guide packages through a warehouse.

Now, these are very, very tiny. Each microtubule is about 25 nanometers in diameter, which means you can line up 4,000 of them across the width of a single human hair. And they're long, too. So, they stretch like tiny straws all through the interior of the neuron. Now, what's amazing is these are constantly assembling and disassembling themselves, almost like living Legos, and this adjusts the internal architecture of the cell in real time.

So Stuart got interested in these microtubules and wondered if they were more than just railroad tracks. Back to Stuart. Well, microtubules are found in all cells, including neurons, which are full of them. And they are like the skeleton and the scaffolding of the cell, but they're also the nervous system of the cell. They organize things.

And their structure I learned back then is a lattice kind of like a computer lattice where you have individual units proteins called tubulants that I thought back then uh can be in two two states uh like like flexing like a peanut open and closed and that would be like a bit a one or a zero. So Hamroof was looking carefully at these and he proposed that microtubules might be doing something beyond structural work that instead of just looking at the microtubule as a roadway, you might think about the details of the microtubules and ask whether this could be a structure that was a lot more interesting than it first appeared. So he started modeling tubulins, the little bricks of microtubules, and came to the conclusion that you could store something like 10 to the 16th bits of information in a single neuron using microtubules. And this was essentially the number that people were talking about for the storage capacity of the entire brain. Now his colleagues were skeptical.

They didn't want to hear it. Told me to get lost. So except then one day, fateful day, this guy said to me, okay, wise asked, let's say you're right. How would that explain consciousness? How would that explain? Love, feelings, pinkness, joy, blah blah blah. Essentially, the hard problem 5 years before Dave uh announced and uh but I, you know, I knew the knew the problem.

I said, "Whoa, you're right. I have no idea. I was a reductionist and I didn't I was ashamed of myself actually." So, wait, actually, just one second. I want to make sure everyone's following. So, the hard problem of consciousness is you've got all this physical stuff happening in the brain.

Why does it feel like anything? Why do we have experience? That's the hard problem. Okay. So, so you were looking at these microtubules which are made up of these tubulant peanut shaped proteins and you're saying hey there's something really interesting here but um but it didn't solve the hard problem right so okay I was just saying more computation more information processing so and the guy had a beautiful point and I was kind of stunned and he said you should read this book by Roger Penrose called the emperor's new mind I said I've kind of heard of that guy so I bought the book I read it and I was kind of blown away I mean it's a amazing book The first half is about why consciousness is not a computation. He used something called Girdle's theorem for mathematics which said a mathematical theorem cannot prove itself. You need somebody or something outside the system like a a mathematician to say yeah it's true or not.

And he extrapolated that and said it's like understanding you know to understand something you need to be outside the system. Very similar to John Surl's Chinese room argument. You know the guy has the Chinese symbols he looks them up and he translates but he doesn't understand Chinese. So that's the he's just doing computer operations and so that was the difference and Roger so the second half of the book was Roger's solution which had something to do with quantum physics and collapse of the wave function the measurement problem in quantum mechanics which is a whole another mystery and uh but he said the solution to that mystery is the same as is for consciousness but Roger didn't have a biological structure that could be at the quantum level and he said in the book I don't know what it is maybe somebody does so I read the book and I said holy crap he needs microtubules. I had been studying for 20 years.

So Stuart wrote Roger a letter. But then Stuart Hammerov read my book and wrote back to me and said, "Evidently, you don't know about microtubules." He was absolutely right. If I'd known about right microtubules, I'd say here's a much better bet. For various reasons, they are partly because they're tubes. Actually, it seemed to me that there is a much better chance you could isolate quantum effects.

So, they met up in England and Roger was very taken by the geometry of these microtubules. Tell us what is special about microtubules. Well, what's special about microtubules? There's several things which excited me about them. Some of them are sort of peripheral but not not so stupid maybe. They are tubes to begin with.

And that struck me as much better chance to preserve coherence. You see, if you're going to have the collapse of the wave function, you've got to have a well- definfined wave function which isn't collapsed by the environment. You see, normally what happens is that that the environment collapses it. And that's no use to anybody. The standard, as I say, land vonoman arguments you say that the collapse occurs because the environment gets involved.

you have no control over the environment and so therefore it behaves randomly in some way. In other words, he's pointing out that the environment normally collapses the wave function very rapidly. But he appreciated the possibility that microtubules might serve as a wave guide, which means there's something about the particular structure of these long thin straws that keeps the wave function uncolapsed for a longer time. A, they're tubes. B, they have a very symmetrical structure of the the the tubulins and they they combine together in this particular structure which I found fascinating because it has for example symmetries in three different directions.

One is along the axis, one is twisting one way and the other is twisting the other way. So it just struck me what's funny about these microtubules. You have these microtubles which have one direction along the tube and that seems to mirror what you get in these nano tubes that they become superconductive. So this suggested to me that maybe there is some quantum superconductive effect along the tubes which is quite different from nerve transmission and which is absolutely a quantum effect. So the idea is you've got these microtubules which are inside all the neurons and these can serve as wave guides.

One of the criticisms that people have had about quantum mechanics in the brain is they say look it's too warm and noisy in there. What what do you say uh in response to that? Well that's a general comment. You might expect that applies if you if it hasn't got some very very specific structure. Um, and the microtub was I thought much better chance of that sort of thing. I mean, they're doing a pretty trick, pretty good trick.

You see, if they actually are preserving coherence along the tubes, this is a neat trick that nature allegedly I'm saying that is to say that's my viewpoint, must actually have succeeded and making this trick. I the general comment is warm and messy sure as a whole but there are structures within this warm and messy things. You don't need the whole thing to be structured in this way. You just need certain elements in this complicated structure which as a whole may be warm and messy and all sorts of things. But there are things the claim goes which can preserve quantum coherence.

And the idea is that maybe microtubules do. And when I heard about them for Stuart, I thought that was a much better case than anything I'd seen before. So Hammeroff and Penrose got interested in this possible relationship between microtubules and quantum mechanics. But what does any of this have to do with consciousness? Back to my interview with Stuart. In quantum mechanics, things can be in different positions.

The wave function predicts how that moves along nicely. But what happens is you get a collapse of the wave function which tells you hey the let's say the particle is over here over here and the idea was the collapse that moment when that happens there's uh some consciousness in the universe that's what he predicted that's what he predicted okay other people were saying conscious comes to the outside and causes a collapse but that puts consciousness outside science it's a dualist position actually one of the charmers takes now but other you know goes back to vigner and vonorman and and bore um uh early part of the 20th century and then uh and and others had many didn't want collapse to deal with it or consciousness. So they just said many worlds it's easier to think about than consciousness and uh and Roger came up with a solution said the separations are unstable and will collapse and give consciousness and due to an objective threshold given by the indeterminacy principle one equation okay and so who is experiencing the consciousness or the qualia when there's a collapse of the wave function the collapse itself is who's is who what is experiencing I don't think this is controversial I don't there needs to be a separate self. Uh other people disagree with me on that. Um but I think if you have a sequence of experiences and memory, you have a self.

You know who you are. You know when you wake up in the morning, the same person moment to moment. So I don't think there's any separate entity as the self. I think just I think you have a sequence of experiences, complex experiences. I should go back and say when when when the u objective reduction that's his name for objective threshold quantum state reduction objective reduction or or uh when that occurs in the environment in in the chair anywhere other than uh in particular arrangements it's the experience is random fleeting uh disconnected it comes and it goes it's apparently happening all around us we never know what it is it's like and that was protoconcious so that they call that protoconscious and I liken that to uh if you go to the symphony and the musicians are tuning their instruments before and you hear all this to me noise to a trained musician it's different but to me it's like you know it's it's noise and then they start to play and it's bronze or beethoven or whatever and uh and that's what the brain does that's what the microtubules do orchestrates the objective reduction hence the theory is orchestrate objective reduction okay so when there's the collapse of the wave function.

There's a little bit of consciousness. Um, but if you build a device in the right way where you've got all these microtubules that are guiding this that are orchestrating this whole thing, then you get something like our consciousness and they have to they have to be entangled. So the superposition states become part of one one more complicated state. So when you when we're collapsing our conscious moments now, there's a lot of richness in it. I see you, you see me, I see the stuff behind you, etc., etc.

And so and there's sound, there's uh different senses. It's all orchestrated. I would say integrated, but that's a different theory. It's it's more orchestrated. Now, what would that get us to have entanglement across different regions of the brain? Well, one example Stuart turns to is what's called the binding problem.

The binding problem is a long recognized mystery that different regions of the brain encode very different types of information like movement here and colors here and face recognition and sound and touch and yet you enjoy a totally unified experience. For example, let's say you're watching a basketball player race down the court dribbling the ball. Different areas of your brain are processing the shape and the movement and the sound of the ball hitting the court, but you perceive the whole thing as one guy racing down the court. The colors and the motions and the sounds don't separate off from one another. So, how are these distinct features processed in totally different brain regions integrated into one seamless perception? This remains a central mystery in neuroscience.

So how might their theory address that spatial temporal binding? You know, you see something moving through the sky and it shape, color, motion, meaning are processed at different places in different times in the uh visual cortex and cortex in general and yet we see one object. We see a yellow kite fluttering instead of yellow kite fluttering, we see one thing instantaneously. So it's it's integrated or uh orchestrated in time and uh and also in different regions of the brain. So I think the brain needs entanglement one way or the other. So in other words, neuroscience traditionally just thinks about neurons and those are in some sense quite slow.

But maybe Hamarov suggests there are much faster processes that are binding things together. It's more like music. It's more like resonance, harmonics, interference beats. In fact, to get from the very fast to the very slow interference beats is probably what what does it. So I think the brain is more a quantum orchestra than a than a computer.

Got it. And so essentially all our technologies are just measuring what neurons are doing. Like you dunk an electrode in and you see the spiking of the neuron. And so um they're only listening to the bass and percussion of the symphony. They're missing the flutes and the piccolo and the and everything else.

And what makes you think this? The other theories don't work. All the other theories are based on a neuron firing is a bit or a neuron is essentially a one or a zero. And if you look at a single cell organism like a parramium, it swims around. It finds food. It finds a mate.

It has sex. It can learn. If you suck it into a capillary tube, it gets out faster and faster each time. It's one cell. And it does all that with its microtubules, with its silia and its internal microtubules.

So if a parramium can do that, are you serious in thinking a neuron is a one or a zero and that's it? It's an insult to neurons. So together, Penrose and Hamoff worked on their idea of entanglement going on across the brain. And the hypothesis is that these deep tubes humming away deep inside the brain's machinery, these orchestrate when and what collapses. So they call this orchestrated objective reduction. Give me the idea of of orchestrated objective reduction.

What does that mean? And how does that explain consciousness potentially? Okay, think of a I used to I used to play ping pong when I was at at school for instance, you see, and I never achieved any great skill at this, but I can understand that it's a game where you have to act very quickly. And the way if I flick the ball into the right hand corner as opposed to the leftand corner, it's because I think by looking at my opponent that he's not expecting it me for me to flick it into the left hand corner. And so I do that flick into that corner because I think from what I've just gained a very small fraction of a second, much less than half a second, I estimated that this is a good thing to do. So I think that was a conscious choice. Now what is the current view amongst I believe and I get this from Stuart the current view amongst neurohysiologists is that these actions are not conscious they're much too quick but Stuart's view and mine is that is conscious but it can only occur because of the following mechanism.

The argument would be that you could preserve quantum coherence at a big level that it's sufficiently isolated from the outside world that in this layer you could preserve a lot of quantum coherence. So that this would mean that the action of flicking the ball this way rather than that way and this choice is it made conscious consciously the current view is there's no time that the consciousness come about much too late for this but our view is no there is time because the choice of which action to take can be a conscious one. The action taking involves a lot of nerve transmissions and making your arm go this way rather than that way and all these things. You think of a tennis player deciding to go crosscourt rather than the down the line and that involves different muscle muscle actions. Now those different muscle actions can be in superp position kept in superp position.

So which one of them is triggered can be done very quickly and those then the actions take place and then and the person does what is decided to be done. So although the the conscious action to move all those particular muscles like this and that's not conscious what's conscious is I'm going to flick the ball to the right rather than to the left and so that is a whole lot of different motions which are all together in superp position. So this is the idea that this collection of motions and that collection's emotions and which ones are activated are all there together and which one is activated is a is a conscious choice and that conscious choice as it is at a quantum level choice in these very specific cells that you get the coherent superposition of different actions. I see. It could be this action is under control or this one or this one and they're all there in quantum superposition.

So the choice you make as to which one is controlled is a quantum choice. And presumably when when the waveform collapses that's when you become conscious of something. That's that's the idea. Yes. That's what the consciousness is to do with the actual collapse.

One intriguing thing is that this proposal uh seems to blur the line between physics and philosophy in an interesting way. So if consciousness arises through quantum processes, does that suggest that consciousness is not just a feature of brains but a more fundamental property of the universe? How do you see that? Yes. But you see, but it might be you got to get it organized in a very subtle way in order to reveal. You see, the collapse part of it might be easy to reveal, but the way in which it's not quite random and quite random probably in a very sophisticated way. Does this hypothesis have implications for free will? That's a very good question.

You see, I'm quite recently sort of changed my view on this question. I often thought it's a sort of meaningless question in a way. I mean does it mean that a quantum effect is brought into play because quantum thing is not deterministic and does the fact that it's not deterministic mean free will? Not normally because it's random and if it's random that's not free will. I mean you're just tossing a toy. It's not random because it's got to be doing something.

I mean, randomness isn't beneficial in a way. You see, you could you could make it random, but that's not the point of free will. You could say that. You see, people often say that free will could be there if it's not deterministic. But it doesn't do you any good if it's just random.

Yeah. So, the view I have is is more or less this. It's not even my It's a fairly recent view, I think. But the view is more this. There is something retrocausal about it.

What free will really means and what I'm arguing for here is not that you can do anything you like and you can act randomly if you like. You're doing what you think is the right thing to do. So you have the free will to do what you think is the right thing to do. Now it doesn't necessarily mean righteous in the sense of virtuous. It means the in your judgment the correct thing to do whether it's correct just for your own beneficialness or or for the good as the whole or whatever that's not the point.

The point is that you are doing it because you think it's the right thing to do. Now that means you're understanding it. What kind of experimental result would excite you most in in the coming years? I think if you're looking at things plausible within the current technology, maybe some convincing kind of quantum coherence within microtubules. I want to ask you about AI. We've seen such incredible progress in classical AI systems.

But given your view that consciousness involves non-computable processes, do you think that AI uh is conscious, could be conscious, or is it just an impressive simulation? No. In one word. Okay. It's not conscious. Okay.

and it's not going to be conscious by having more and more and more uh elements in your computer. So could a quantum computer in the future could a quantum computer be conscious if it were designed with the right architecture or is something else still missing? You have to be careful about what you mean by a quantum computer because I don't think quantum computer in the sense that people use that term does actively involve using the collapse of the wave function as part of the mechanism in quotes because it's not really a mechanism. That's right. Yeah. Okay.

Got it. So the the kind of quantum computers that for example Google is working on now because presumably it doesn't involve the collapse of the wave function. You think it wouldn't be conscious as such? Is that right? Okay, great. I asked Stuart the same question about whether contemporary AI could be conscious, not with the kind of computers we have now. Uh not with a siliconbased and you know, our friend Dave Chamers uh after uh decades of the hard problem recently came out and said, "Well, uh AI consciousness is inevitable and throwing the heart problem under the bus." Totally interesting.

and then backing up. And when I questioned him about it, he said, "Well, what's the fundament? There's no fundamental difference between silicon and carbon." I said, "Wrong answer, Dave. First of all, it's not carbon. It's organic carbon, which means aromatic rings, which means quantum." So that and there's a huge difference between organic carbon and silicon. Silicon can't do that.

So, and this organic carbon aromatic hydrocarbons have been in the universe right from the start. So, let's summarize. According to this idea from Penrose and Hammeroff, the brain isn't just a network of firing neurons. It's also a kind of quantum computer. Inside every single brain cell is a whole world of microtubules.

These tiny cylindrical structures that are so small they've traditionally been ignored. But maybe they suggest these structures are doing more than organizing the cell's interior. Maybe these microtubules are hosting quantum processes. Maybe they're sustaining delicate quantum states long enough to do something meaningful and entangling across cells and that the collapse of these states might correspond to moments of conscious experience. Now I just want to repeat one point.

You might be thinking, wait, doesn't quantum physics get washed out in warm, wet environments like the brain? That's a reasonable objection. In fact, it's one of the main reasons that many scientists have been skeptical of the orchestrated objective reduction theory. Quantum coherence usually does not last long in messy biological environments. It's fragile. But on the other hand, that skepticism has been challenged in recent years by findings in other parts of biology.

Quantum effects have now been observed in photosynthesis, in bird navigation, in the sense of smell. Somehow, living systems might be more hospitable to quantum phenomenon than we thought. And if that's the case, then maybe, just maybe, the brain has found a way to leverage quantum effects, not just for computation, but for consciousness itself. Now, Penrose and Hamroof's theory and others like it remain highly speculative. Neuroscience continues to make great progress without invoking quantum mechanics.

artificial neural networks which are entirely classical in their architecture. These have achieved unbelievable feats like the modern blossoming of AI. But so far as we know artificial neural networks like chat GPT are not conscious. And so the idea here is that we need to think not just bigger but perhaps also submicroscopically smaller. So, we've just heard from two thinkers who aren't afraid to step beyond the comfortable borders of their fields to probe around in areas that most scientists won't touch.

What I find so compelling isn't the certainty of the theory. It's the audacity of the question. It's the willingness to say, "Look, perhaps our current tools aren't enough. Maybe consciousness isn't just a clever computation, but something much stranger. Maybe the deepest puzzles in neuroscience can't be solved without rethinking everything from the ground up.

There's a long history of big leaps in science, beginning with questions that sounded naive or mystical. There was a time when most of the ideas we take for granted today were ridiculous. So, I want to return to one last thought from Roger. What advice would you give to young scientists who are drawn to the big risky questions about consciousness but are afraid to step too far outside conventional boundaries to be try and do the following. You will have some specialist view that you see in order to make progress you got to dig deeply in a certain area and understand that area as well as you can and better than most other people.

But you also at the same time should keep a broad outlook of what's going on in the outside world and pick up maybe if you see something which might connect with what you're doing. There are plenty of critics of this idea who point out reasonably that there's not enough experimental evidence to take this idea with the requisite seriousness yet. But it's okay to explore the speculative as long as we keep one foot planted in the empirical. The key to making progress in science is balancing skepticism with curiosity and openness. All of us in neuroscience like to believe that we're close to cracking the puzzle of consciousness.

But the fact is we're probably just at the foot of the mountain. And it's always possible, just like in any field, that we're not even asking the right questions yet. What if we've been looking at the hardware in an incomplete way and missing the best tricks of physics? The fact is that the central mystery of neuroscience for which no one has a good answer is the hard problem of consciousness. Why, if we have an organ that goes around and collects information, no different than a camera or a microphone, why does it feel like something presumably in a way that your iPhone does not when it makes a recording? Why do we have private subjective experience of the world? Quantum mechanics may or may not provide the answer. Maybe we're all just shooting in the dark until we discover a new field in a 100 years from now called schmantum mechanics.

But whatever the case turns out to be, it seems likely to me that the neuroscience textbooks used by our great great grandchildren will have very different stories than we do today. And future centuries will look back on our scientific frameworks with the quaintness that we look back on ideas of flegiston or spontaneous generation or that the earth was at the center of the universe. But the only way we're going to get there is to keep digging deeper and asking. By not falling for the assumption that we've got it all figured out with our standard textbook models, but by continuing to propose and put to the test brave new hypothesis. Go to eagleman.com/mpodcast for more information and to find further reading.

Check out my newsletter on Substack and be a part of the online chats there. You can watch the videos of Inner Cosmos on YouTube or you can leave comments. Until next time, I'm David Eagleman and this is Inner Cosmos. [Music]