Jean Mary Zarate: 00:04
Hello and welcome to Tales from the Synapse, a podcast brought to you by Nature Careers in partnership with Nature Neuroscience.
I’m Jean Mary Zarate, a senior editor at the journal Nature Neuroscience, and in this series, we speak to brain scientists from all over the world about their life, their research, their collaborations, and the impact of their work.
In episode two, we speak to a prominent researcher and writer who is pushing the boundaries of work around the nature of consciousness.
Anil Seth: 00:39
I’m Anil Seth. I’m a professor of neuroscience at the University of Sussex, and author of Being You: A New Science of Consciousness.
Finding a title for my book was actually pretty challenging, because a lot of titles about consciousness have already been taken.
So I settled on “Being You,” I think partly to emphasize one of the most fundamental, important salient aspects of the mystery of consciousness is the experience of being a person, of being me, of being a self within the world.
I like to think of consciousness as two fundamental aspects. There’s our experiences of the world around us, the colours and shapes and people and places and objects.
But then there’s the experience of being a self within that world. And that’s, and that’s really fundamental for living our lives, for who we are.
And I think it’s also the source of many confusions and debates about consciousness. Big questions, like freewill, that has to do with the self. Emotion, mood, all of these things are to do with the self.
And so it’s a bit harder to study, but it’s very, very rich. But Being You is just the simplest way to get across this idea that there is something to be explained about what it is to be anyone.
There’s three main arguments I make in the book.
The first is that consciousness is something that can be addressed by science. This goes against an influential idea that consciousness is beyond the reach of science.
But I rather think treating consciousness as something like life, where it used to be mysterious, but then just by identifying its properties and explaining these properties one by one, like metabolism, reproduction, homeostasis, people understood life as being not beyond science, and I think we can follow the same strategy with consciousness.
And those elements of consciousness that I talked about in the book, dividing it from one big scary mystery into a few smaller, more tractable mysteries. conscious level, and how conscious is somebody at a particular time the difference between general anesthesia and wakeful awareness, falling into a dreamless, sleep, psychedelic state, and so on.
These are all different levels of consciousness. How can we explain the transitions between these levels?
Then, secondly, perception of the world around us. And here comes the idea that we each live within a controlled hallucination, that our experiences of the world don’t give us direct, unfettered access to whatever’s out there, but rather perceptual experience, the colours and the shapes and the sounds that populate the world that we experience, they are actively generated, not passively perceived.
The idea, the neuroscience idea here, is that the brain is a prediction machine. And it’s continually generating predictions about what’s out there, and using sensory signals, to calibrate these predictions.
So we don’t read out the world from the sensory signals. We actively generate it, but our active constructions tied to the world in useful ways. So the control is just as important as the hallucination.
And then the third step is to realize that this also applies to the self. The self is not the thing perched somewhere behind the eyes in the middle of the skull, that’s doing the perceiving, that’s the recipient of all this information.
The self itself is a perception. It’s another kind of controlled hallucination, all its aspects, whether it’s the experience of free will, of having a body, of emotion, of mood, all different kinds of perception.
And the argument that I make at the end, this place we end up in, is that maybe these basic experiences of selfhood are primary, that all the mechanisms by which the brain makes predictions and forms experiences of the world and of the self are all fundamentally rooted in our nature as living creatures. As beast machines in the words of Descartes.
And through this lens, which which I didn’t expect to get to, when starting this journey, is that we experience the world and the self, with, through, and because of our living bodies.
And this intimate relationship between life and consciousness, has quite profound implications. So at the end of the book I explore some of these implications for consciousness in non-human animals. And finally, for consciousness in machines. The question of whether artificial intelligence will not only become intelligent, but also sentient, also conscious.
This is often a topic of much interest in science fiction, in the media. But if you think of consciousness through this lens of its intimate relation to the living, it makes the prospect of artificial consciousness less likely.
Any good science needs to start with a definition. So this question of how to define consciousness always comes up. And I like to start with with a pretty simple definition of consciousness. And this comes from a philosopher called Thomas Nagel.
And he said, for a conscious organism, there is something it is like to be that organism that feels like something to be me.
For any other person, it feels like something to be that person probably feels like something to be a bat or a kangaroo, or a cockatoo.
But it probably doesn’t feel like anything, to be a table, a chair, or a laptop computer. These things, there’s no inner life.
And I like this definition because it’s very, it’s very inclusive, it’s just any kind of subjective experience whatsoever.
Consciousness is not the same thing as intelligence, it’s not the same thing as having language. It’s not the same thing as behaving in a particular way. It’s just the fact that experience is happening.
And we all know this. We all know what it’s like to be conscious. And to lose consciousness when we fall into a dreamless sleep, or go under anesthesia.
That’s actually another good way to define it. Consciousness is what goes away, when you lose it, when you fall into dreamless sleep or when you go under anesthesia. And it’s what returns when you come around again.
Anil Seth: 07:38
When I was a kid, probably about eight or nine years old, growing up in a small village in South Oxfordshire, I have this memory.
And I don’t know how accurate it is, because it’s from from long ago, but the memory is of looking in the mirror, in my parents’ bathroom on the ground floor of the house, seeing myself in the mirror and realizing at that point, that eventually, I would die, that this experience, this thread of experience of being me would come to an end.
And from that single moment of realization, a whole raft of questions just came rushing forth like, “Well, where was I before I was born? Who am I? Why am I me and not somebody else? What is this thing that is in mind?”
I probably didn’t formulate these questions quite that way when I was eight years old. But it’s a memory of the ignition of this interest in consciousness and in the self. And I think many kids do have these kinds of questions, do have these kinds of interests, and then get educated out of them because they’re considered armchair speculation, philosophy, religion, maybe not that useful.
But when I was a teenager many of my friends would just argue about things like free will and the mind and consciousness.
And I think I’ve just been lucky in being able to continue to be interested in these fundamental questions for many, many years since then, and actually making a career from it, which I feel very fortunate to be able to do.
Anil Seth: 09:24
And when I went to university at 18 I was keen to study physics because I thought physics is the queen of all the sciences. Ultimately, any mystery that seems to exist is going to be solved through physics. That’s certainly what I thought.
But I ended up transitioning to psychology, just the gap between what we were doing in physics and this interest in the mind seemed seemed too large.
So I ended up transitioning to psychology and then segued again into computer science and AI, because at the time, in the 90s, models of the mind and the brain were mainly boxes and arrows.
And here is memory and here is emotion and here is decision making and here is attention. And they have arrows between them.
And that wasn’t for me very satisfying. So I wanted to go and learn about neural networks, and also more of the philosophy about mind and brain.
So I ended up at Sussex University where I am now and did a PhD in artificial intelligence, which was very useful in bringing to me a different set of tools and perspectives about how brains and bodies and environments all work together in constructing our mental lives.
But while this was really, really interesting, and productive, I was getting further away from this core question about consciousness.
And so I then started working in neuroscience. And this was probably the first time that I started in neuroscience itself was when I was a postdoc in America, and working in San Diego, with Gerald Edelman, who won his Nobel Prize in immunology many years before, and with that, of intellectual capital decided that it was okay to study consciousness.
Because here’s the thing and the 90s. In my experience, anyway, and even 2000s, there were very few places that would explicitly say that this is what we’re doing outside of philosophy in a few enclaves of neuroscience, it was still considered a little bit disreputable.
I remember Stuart Sutherland in the international dictionary of psychology from 1989. So not that long ago. I mean, he wrote, ”Consciousness is a mysterious phenomenon. Nobody knows what it is, how it works, or what it’s for, nothing worth reading has ever been written on it” which is quite a damning indictment of consciousness, and it’s quite offputting for a young student who’s interested in this stuff.
But by the mid 90s, in certain places, things had changed, and there were more institutions, more senior academics willing to say that it was okay, and built labs that were explicitly working on consciousness.
That’s why I ended up in the US. But in the mid 2000s (2007 I think) I came back to Sussex to set up my own group there. And that’s where I’ve been ever since.
Anil Seth: 12:32
Yeah, I think I’ve taken a bit of an unusual trajectory to get to where I am now. And part of that was was this resistance against the idea that I thought was necessary in science, that you just keep on specializing, that you choose a broad subject area, and then that would get a bit narrower, and get narrower again, until eventually you knew everything about something that nobody else cared about at all. And I didn’t want to end up like that.
But I also realized, and this wasn’t my realization, it’s very clear for many people, that a question like consciousness doesn’t reside easily in any single discipline, or part of the discipline.
It’s such a pervasive challenge in science and philosophy that it brings together in neuroscience and psychology and physics and maths and computer science. Even the arts, (well, philosophy, of course), but also the humanities. Literature is a great exploration of what it is to be a human self.
So the study of consciousness is some kind of insurance against falling into a single, disciplinary hole and remaining there forever.
So my own trajectory did skip about between different disciplines in different areas with the result, of course, now that, you know, I’m not expert in any of these areas.
But I have some experience of of how to find the right links between them to ask and answer the questions that we want to ask and answer, in a science of consciousness.
And in my group now at the University of Sussex, it’s highly interdisciplinary. We do have people with PhDs in string theory, in mathematics, in psychology, of course, and in neuroscience.
But we also have people working with VR, people working with with brain imaging.
And we do increasing amount of art science collaboration, too. And we are discovering things this way, this isn’t just an act of publicity for the science. These collaborations with artists can reveal new questions or new ways to address existing questions about consciousness.
And for me, this interdisciplinary mix has been both extremely challenging, to try and keep figuring out how we, how we do it, and how we keep funding it, but also extremely rewarding because you’re always learning new things. You’re always up against it and there’s, there’s always something quite novel and quite innovative to do.
Figuring out how perception works is a massive challenge. It’s not purely in the study of consciousness. It’s been a big topic in psychology and neuroscience for centuries.
But when we think about in the context of consciousness it’s really this question of “How does our conscious experience of the world out there relate to the sensory information that’s coming in through our eyes and our ears?”
And it may seem as though there’s not really much to explain here. It might seem as though the world just pours itself in through the transparent windows of our senses into the mind and that the self is perched in there somewhere, doing the perceiving, the recipient of all this information.
But this isn’t what’s going on at all. And to see why, to understand why, I think it’s helpful to change perspective and imagine that you are a brain, to imagine that you are your brain.
There you are, you’re locked inside this bony vault of a skull, it’s dark in there, sign it, there’s no light, there’s no sound. All you’ve got to go on as a brain are these electrical signals coming through the sensors, which are only indirectly related to what’s out there.
These signals, they don’t come with labels on they came from a cat or a coffee cup, or I’m blue, I’m green, or anything like that.
They’re just electrical signals that are noisy, uncertain, ambiguous, with respect to what’s outside. So the brain has to make sense of these signals in order to form the definite perceptions we have.
I experience a sofa over there in the distance, I experience a TV on a stand over there, these things really seem to be there.
So the way this happens, the idea that I find the most compelling about this, is that perception is a process of inference, of best guessing.
So the brain is continually making its best guess about what gave rise to the sensory signals that it gets.
And what we perceive, what we experience, is not a read out of the sensory signal, it’s not something that’s coming purely from the outside in, or the bottom up.
What we perceive is the content of the best guess itself. Our perceptual experience comes primarily from the inside out, or the top down.
And this is not a new idea. There’s the German polymath physicist and physiologist, Kelvin Von Helmholtz, who was probably the first to describe a framework which we now call predictive processing.
And this is the idea that the brain is continually generating predictions, not about the future, not always about the future, but predictions about what’s out there and the here and now.
And it uses sensory signals to calibrate, to update these predictions. And perception, in this view, is a process of the brain continually trying to minimize prediction error, trying to suppress prediction error, so that its best guesses latch on to the world in ways that are useful for the organism.
Not necessarily in terms of accuracy. But in terms of utility. Anais Nin the novelist said it best when she said “We don’t see the world as it is, we see the world as we are.”
Thinking of perception this way, it’s a bit like a controlled hallucination. And I like this term. It’s a bit, it’s a bit provocative, for sure. But I like it because it emphasizes a continuity between normal perceptual experience, which just seems to be seeing, perceiving the world as it is, and hallucination, which we think of as cases where our experiences depart from what’s out there, from what others see.
But actually, there’s probably a continuity between all forms of experience. It’s just that in normal perception our hallucinations are reined in, they’re controlled by signals from the world.
And hallucination, and this thing where cases where people experience things that others don’t see people that other people don’t see, hearing voices that other people don’t hear, you can think of these as uncontrolled perceptions.
It’s the same mechanism, but the brain’s best guesses have lost their grip on reality.
Anil Seth: 19:47
Central to any conscious experience that we have, at least most of the time, is the experience of self, and the experience of being the subject of experience.
It’s not that there are experiences of a car across the road, It’s that I am having that experience, there’s an experience of a person and me and identity, maybe sitting behind the eyes that that is receiving these perceptions, and then deciding what to do with them, deciding whether to get up and park the car, drive the car, make a cup of tea.
So there’s this intuition, that the self is the thing that’s doing the perceiving. But again, I don’t think that’s right. And there’s a long history of thought and philosophy and also work in psychology that also challenges this, to suggest that the self is not that which does the perceiving.
But the self is also a kind of perception. It’s the brain’s best guess, in this case more about the body, rather than about the world. And that’s what underpins our experience of being a self. My experience of being me, or your experience of being you.
Reflecting on all this, on this rich experience of being a self, and even richer experience when we consider the world around us. You know, we experience a self within this beautiful, rich, coloured, vibrant world, it just endlessly astonishes me that all of this comes about through the activity of this electrical wetware inside our skulls.
And the brain is very complex. We have 86 billion neurons and 1000 times more connections. But it’s still an object. It’s a complicated object. And to think that the wonder of the experience of the self, and of a world can come about through this electric chemical machinations in this tofu-textured wetware that we have. I mean, that’s, that’s just, I mean, it seems like a miracle.
But I think that’s the point of science, isn’t it, to preserve the wonder of a phenomenon. But to explain it too.
Anil Seth: 22:04
These ideas about perception as a kind of controlled hallucination and the self as a kind of perception, they’ve been around for a long time and in different ways. I’ve taken them in my own direction with a theory that I’m calling the “beast machine theory of consciousness and self.”
And I use the word beast machine. I’ve stolen it from from René Descartes. And Descartes, back in the, in the 17th century, he used the term beast machine to describe non-human animals because he thought, or he at least he claimed, that non-human animals were not conscious.
In his mind, they were just machines made of flesh and blood, or beast machines. And I’m trying to reappropriate the term for almost the opposite reason, to suggest that we are conscious along with other animals, not in spite of but because of our nature as living systems, that we perceive the world around us, and the self within it, with through and because of our living bodies.
That’s the main idea. To get there, it’s really a case of, of running with this idea of perception as a controlled hallucination as far as it will go.
We first start thinking about perception of the world around us, as the brain’s best guess, of what’s there. And then we can turn the lens inwards, and apply the same ideas to how we perceive the body, how the brain perceives the body. It’s generating a best guess of what is and what is not the body.
And that can give us our experience of, of embodiment of what is the object in the world that is my body?
But then we can go even deeper. And there’s a whole tranche of perception, whole area of perception, called intereception, which is all about the brain sensing and regulating and perceiving and interpreting the signals that come from deep within the body itself. signals that reflect things like heart rate, and blood oxygenation, and the function of the liver, all of these sorts of things.
Again, imagine being a brain, you still don’t have direct access to what’s going on in the body, you still have to infer it, based on sensory signals that are coming, in this case from the body itself.
And my argument is that it’s the same mechanism at work. So the brain is again making predictions about the causes of sensory signals from within the body.
And what we experience as the embodied self is the content of these predictions. And these can be things like emotions and moods. And this way of thinking builds on some pretty classic experiments actually, in in old school psychology.
So there, there’s this one of my favourites is this experiment by by Dutton Aron in the 70s. To show that what we experience as an emotion isn’t just a direct readout of the physiological state of the body. But it’s an interpretation of why that state of the body is happening. And the basic idea goes back even further, it goes back to William James, who argued that emotions are kinds of perceptions of the body, I think this is where we first see this idea arise in psychology.
And then, in this experiment, what Dutton Aron did was, they had groups of male students who would walk across one of two bridges in a river near somewhere Vancouver. One bridge was very sturdy and safe and quite low over the water. But the other bridge was very rickety, and very high above this rocky ravine quite scary thing to walk over.
And so the students walked over these bridges. And at the other end, they were met by an attractive female researcher with a questionnaire.
And they filled in the questionnaire. And the researcher gave the students a phone number and said, “If you’ve got any further questions, give me a call.”
And what happened was that quite a number of the students who’d gone over the rickety bridge called the researcher to ask for a date. And many fewer, who walked over the sturdy bridge.
Now, this was an experiment done in the 70s so the methods and so on might be a little bit outdated, but it’s really, (and the ethics might be a bit complicated now as well!).
But it makes the point that the emotions that the students were experiencing were an interpretation of what was going on in their bodies.
Like going over the rickety bridge invokes a state of physiological arousal. You’re a bit scared up on this high bridge. But that physiological arousal was being reinterpreted, or misinterpreted, as some kind of attraction by the time they got to the end of the bridge.
And this didn’t happen on the sturdy bridge where there was no comparable physiological arousal. So this has been a bit of a sidebar, but I think it’s a lovely example of how emotions again, our constructions of the brain, their best guesses about why the body’s physiology is doing, doing what it does.
Anil Seth: 27:32
The final step in the beast machine is to recognize that the brain’s predictions are not simply about finding out stuff. They’re about controlling stuff.
This is a very old idea, again, in this case from engineering, that if you’re going to control a system, whether it’s a body, or a central heating system, or an autopilot in a plane, you need to be able to predict what’s happening to that system, and how it’s likely to behave if it’s perturbed or disturbed in various ways.
And I think this explains the core difference between, let’s say, the experience of an emotion, and the experience of looking at a car parked across the road. And when we’re looking at a car, the brain is mainly trying to figure out what’s there.
And so we experience a world full of objects in different places. But when the brain is making predictions about the interior of its body it doesn’t really care where the internal organs are, or what colour or shape they are It cares about how well they’re doing, about how good a job the brain is doing at keeping a body alive.
And that’s why emotions, instead of having shapes and locations, they have a kind of valence. Things are good or bad, or likely to be good or bad, in the future, to different kinds of prediction, different kinds of experience.
And through this lens, if you think about what brains are fundamentally for, they’re not for doing neuroscience, they’re not for writing poetry, they’re not even primarily for figuring out what’s out there in the world. They are for keeping the body alive. That’s the fundamental, most basic duty of any brain.
And so from this perspective, all of our experiences, the entirety of the predictive machinery that allows us to experience the rich world around us, and the self within it, all stem from this fundamental biological imperative to keep the body in a state of being alive.
So this is where this idea comes from that we perceive the world around us and the self within it, with through and because of our living bodies.
Anil Seth: 29:57
I’m often asked and I often think about anyway, how spending 20 odd years now, thinking about and researching consciousness, has it changed me? I mean, of course, it’s changed me Everything changes you, whatever it is that you do changes you.
And I don’t have an alternative me that did something else to compare against, to see how it would be different.
So there’s, I don’t really know exactly how, but I can make some, some guesses. And I think it really has had quite a profound impact on me.
It doesn’t mean that I suddenly experienced the world and the self in a totally different way, you know, not at all.
The red car across the road still looks like a red car across the road to me, and the experience of being yourself still carries with it all the emotions, all the frustrations, all the plans, all the annoyances, and all the pleasures and joys I think that other people experience too. It’s more that there’s a different layer now.
As well as this ongoing flow of experiences there’s another more reflective layer, which has become a little bit automatic for me, to recognize that the way things seem, is not the way they are.
And that the world that I experience is not to be taken for granted. It is the result of this incredible biochemical neural brain-based best guessing that is generating this world, out of a sea of electrical signals. It’s just easy to take consciousness for granted. You wake up in the morning, open your eyes, and there’s the world and as yourself.
But we shouldn’t take these things for granted. And when we notice from from medicine, life is fragile. Mental health is fragile, consciousness is fragile.
You have damage to a few neurons somewhere in your brainstem, you lose consciousness forever.
But even when we are healthy and well, walking around the world with its colours, and shapes, and people in places, all of these things are always being generated by the world.
Or rather, our experience of them is always being generated.
And that I think is profoundly meaningful to reflect on. It has the further consequence that I can recognize that the way I experience the world is not necessarily or not ever the same as how somebody else perceives the world, it’s not going to be totally different.
We all live in a shared objective reality. But we’re all going to experience that reality in sometimes very different, but I think very frequently subtly different ways that we might not even be aware of.
We walk along Brighton seafront, both look up at the blue sky, do we both see the same blue? Probably not. And this, in turn can cultivate a humility, about our perceptions. It seems to us that we see the world exactly as it is and therefore it’s very hard to really appreciate that other people might have different experiences, but they do.
And the only way, or the best way to get that, is to realize that our own experiences are also somewhat unique, somewhat personalized, distinctive.
None of us have a privileged access to the way things actually are. And that humility applies to the self to. My perception of being me, is itself a construction. I’m going to experience self it differently from another person.
Maybe that’s going to be helpful, that, that humility with respect to the way we see the world. Finally, this perspective of consciousness through the lens of the Beast machine is being intimately tied to our nature, as living flesh and blood machines.
When I think about that it makes me feel more part of this vast grand tapestry of nature, and less apart from it. In science and philosophy there’s always been this tendency as, as humans, to put ourselves above and apart from the rest of nature, whether it’s at the centre of the universe, or whether it’s apart from all other animals, we always think of ourselves as exceptional as special.
And we are distinctive, but we’re not that distinctive. We are still part of nature, and this view of consciousness as being intimately tied to life. Just makes that very, very clear, just weaves into the tapestry of nature in a way that’s much deeper than some other perspectives on consciousness.
Jean Mary Zarate: 35:03
Now that’s it for this episode of Tales from the Synapse. I’m Jean Mary Zarate, a senior editor at Nature Neuroscience. The producer was Don Byrne. Thanks again to Professor Anil Seth, and thank you for listening.