What world do you live in? You may think your experience of life comes from the outside, with your brain processing sensory information as it’s received. Anil Seth, professor of cognitive and computational neuroscience at the University of Sussex in England, takes a different view. Tune in as Dr. Seth explains how your brain is actually creating your reality, not just interpreting it.
Plus… why the brain is a “prediction machine,” and how anesthesia is more like death than sleep.
Phil Stieg: Hello and welcome to our guest this week, renowned neuroscientist and author Anil Seth. His bestselling book “Being You: A New Science of Consciousness” earned resounding critical acclaim, including Economist Book of the Year, Bloomberg Business Book of the Year, and Guardian Book of the Week. His Ted Talk, “Your Brain Hallucinates Your Conscious Reality”, has captivated over 14 million viewers. Today, we will delve into the neuroscience of consciousness, and hopefully, by the end, we will have unraveled some of its deep mysteries. Anil, thanks so much for being with us today.
Anil Seth: Phil, it’s a pleasure. Thanks for inviting me.
Phil Stieg: So I guess we have to start with the basics. What is consciousness in your mind?
Anil Seth: In my mind? Well, I’m glad you asked what I think of it, because it’s one of these concepts that we’re all very familiar with, but it does escape a definition that everybody agrees on. I prefer to step back a bit and think about a really general definition of what consciousness is. For me, it’s any kind of subjective experience whatsoever. It’s what goes away when we enter a dreamless sleep, or even more profoundly, when we go under deep general anesthesia, and it’s what returns when we come round. We’ll wake up again, we’ll start dreaming. It’s the felt quality of our perceptions and our emotions that includes everything, also includes the sense of self that we have. Fundamentally, it’s what makes us different from just very complicated biological machines. It feels like something to be a conscious organism.
Phil Stieg: So for you, consciousness is a sense of awareness.
Anil Seth: Yeah, I use consciousness and awareness synonymously. I think they mean the same thing, and I think they encompass both awareness of the world, but also the sense of self, too. The experience of being you, as the book title has it, that’s part of consciousness, too. It’s not that our self does the experiencing, our self is part of the ongoing flow of experiences that the organism has.
Phil Stieg: You mentioned it when you first started and you write about it in your book, your experience with anesthesia. How did that affect you? And how did it affect your view of what consciousness is?
Anil Seth: Actually quite profoundly, I think. In a sense, anesthesia, it’s such a remarkable invention. It’s such a remarkable intervention as well, and I think probably with good reason. People in the medical profession maybe try to minimize how significant it is. “You’ll just go to sleep for a little bit and you’ll wake up and we’ll have fixed you. Don’t worry about the bit in the middle.”
Under anesthesia, you’re pushing the brain to a state as close to death or coma as you’ll ever reach without actually going there for the wrong reasons. Your brain really shuts off consciousness entirely, if the anesthesia is deep enough, and then switches it back on again. You turn into an object and then back from an object into a person.
And it’s amazing how your experience fades very quickly and then subjectively reappears instantaneously. You don’t experience the gap in the middle, and why should you? Because you’re unconscious. It seems a simple thing to say, but it’s actually very different from our everyday or every night experience of going to the sleep. When we sleep, we’re always aware that some time has passed. When we wake up again, we might get the number of hours wrong, but I know it’s been some time. Under anesthesia, when you’re out, you’re back straight away and you have no idea. It could have been five minutes, it could have been 50 years. And I think that complete absence of any kind of experience whatsoever really drove home to me that there’s something going on.
Consciousness cannot be taken for granted. There’s something the brain is doing that makes it the case that you’re conscious at all. And the fact that can be so precisely manipulated, I think that’s both a marvel for modern medicine, but also just a wonderful scientific insight into the brain basis of this central mystery for each of us.
Phil Stieg: Well, that’s what I wanted to bring out, is I think that your approach to human consciousness is very different than the philosophical approach. What’s that difference that a neuroscience approach like yours differs from philosophy and personal narratives?
Anil Seth: Well, I think ideally and I like to think and I might be wrong about this, but I like to think that my approach and others of my colleagues as well, tries to combine the neuroscience and the philosophy and the physics and the other scientific approaches as well.
There’s an old saying, it’s a little bit unkind, but I think it has some truth, that philosophy without science is lame and science without philosophy is blind. I think they need each other, especially when confronted with a phenomenon like consciousness. Science, neuroscience, whatever, psychology, it allows you to test your ideas in the court of reality, and I think that really matters because that can take you in unexpected directions.
Phil Stieg: How do you view the concept of self as being a construct of our brain’s need or desire to continuously create?
Anil Seth: This gets at the heart of the ideas that I’ve been thinking about and developing and testing for many years now. And there’s an old Scottish philosopher, David Hume, He talked about the self as not the thing that does the perceiving, not an essence of you or me, but as a bundle of perceptions, a collection of perceptions. And I think there’s something right about that, that the self is a kind of perception or a collection of perceptions.
And the idea that unifies this way of thinking about the self with a way of thinking about how we experience the world is that the brain is a kind of prediction machine. That the fundamental business that the brain is in is in making predictions about the causes of sensory signals — like what’s out there in the world or what’s in here in the body — and then updating these predictions on the basis of the sensory information that it gets. And the key point is that the goal of the brain in making and updating these predictions is not to figure out how things actually are in the world or in the body, but to stay alive.
The primary duty of a brain is to keep itself and therefore the body going. So predictions that underlie, I think, all our experiences of the world around us and of the self within it are ultimately grounded in the brain using predictions to regulate the body, to keep the body alive. So I like to say that we experience the world and the self with, through, and because of our living bodies.
Phil Stieg: It’s funny, that’s exactly where I wanted to go with this. Is that as I was thinking about your description, is it really self or is it about survival? And it sounds to me like you agree that the brain wants to survive and it’s going to make the body do whatever it needs to do in order to have the energy resources that the brain needs for functioning at the level that it wants. So is that consciousness just the brain’s desire to survive and it’ll do whatever it takes?
Anil Seth: No, I don’t think it’s quite that simple. It’d be nice if it was. But I don’t think that suffices as an explanation.
Predictions about things happening in the world have a particular character. We perceive objects in places that might move and so on, because that’s the kind of information about causes in the world that’s relevant for our survival. We want to know is that object coming towards me or not?
But think about an emotion. An emotion doesn’t have a particular location or a shape. Metaphorically, it might do a little bit. Sometimes we feel pain in our head or in our heart or something, but it doesn’t have a location in the same way that a car across the street has a location. Emotions are characterized by valence. Things are good or bad or likely to be better or worse in the future. And that reflects, in my view, the kinds of predictions the brain is making.
So at heart, this idea, I think it gives a way to connect the content of our experience to our nature’s living systems. And it raises the intriguing idea that really life is fundamental to consciousness because these predictions go all the way down, even within a single cell. I mean, there’s no way to say where the stuff stops mattering.
Phil Stieg: Yeah. So I’m walking down a busy street in Times Square, imagining the amount of external input that’s going into my brain between sound, vision, smell, even the taste of the air around me. What is it about my brain that says, “focus on this” so that I can achieve? Is that the consciousness we’re talking about?
Anil Seth: So It’s going to be evasive again. I think that’s attention. Our brains are very good at selecting what the most salient information is at any point. And sometimes we do this deliberately. We can choose to pay attention to something if we’re trying to listen to a conversation, let’s say, above some background noise. Sometimes it happens automatically. A loud noise or a bright light might just attract our attention. But attention in this set of ideas is really another way for saying how the brain prioritizes different kinds of sensory information. If sensory information is deemed really relevant, then it will have more effect on updating our perceptual predictions and it will become more prominent in our conscious experience.
But attention and consciousness – I think they’re different. I think we’re conscious of more than what we’re paying attention to at any minute, so they’re not exactly the same thing.
Phil Stieg: And what role does memory play in our consciousness?
Anil Seth: I think a substantial role. Memory, of course, is not one thing either. If you start to look into what’s happening in memory, we have long term memory of our lives, the shape of our lives over years and decades. We have a very short term memory of what happened in the last few seconds, and we have all the different forms of memory in between. And I think they shape our conscious experience in all sorts of ways. Certainly our experience of being who we are, the experience of being an individual person is strongly shaped by our memories of what happened to us and our plans for the future. We need this aspect of mental time travel to have this aspect of self.
But it could be that any kind of consciousness, even just opening your eyes and consciously registering a visual scene in front of you, that might require a very short term memory. Consciousness, I don’t think happens instantaneously. I think it’s a continual process of interaction between incoming sensory information and what happened immediately before.
My old boss, Gerald Edelman, had a book he called “The Remembered Present.” This is the idea that consciousness is not just a series of sort of zero duration frames, like frames in a movie. It’s smeared out a little bit. Our conscious experience of the now always extends a bit into the past and a bit into the future. The great phenomenologist Hassell talked about this a lot. I think there’s something right about that. And that means you can’t ever dissociate consciousness entirely from memory.
Phil Stieg: In your book, you give an interesting story about this patient, Clive Waring, who lost forward and backward memory, anterograde and retrograde, but he was still conscious. Describe that for us, please.
Anil Seth: Yeah. This is a really good example of how the different kinds of memory play into our conscious experience in different ways. So Clive Waring had a brain infection, which destroyed his hippocampus on both sides of his brain. It’s a very rare occurrence for this kind of illness. And the hippocampus turns out to be absolutely fundamental in the ability to form and recall episodic memories. Memories of things that happened to me, like what I had for breakfast or where I went yesterday. And he lost that.
So his wife, Deborah Waring, described him as living in a permanent present tense. His window of experience was somewhere between seven and 30 seconds. Anything outside that window, he was gone. He couldn’t remember what happened to him. He couldn’t plan for things in the future either, the flip side of memory.
But yet, of course, many things about him remained the same. He used to direct a choir and he went back to this choir, and he was able to conduct them through a piece of music because that kind of memory, people talk about it the muscle memory, but it’s a different kind of memory, procedural memory that was still there. And he seemed to be fully himself in that moment. But then when he returned to his home, of course he couldn’t remember it happening at all.
So I think it just shows we have this sometimes perhaps necessary illusion that the self is necessarily unified. We have memories, we have emotions, we have a first person perspective. We have a feeling that we have free will and we tend to experience these all of a piece and that’s, you know, the idea “that’s me,” the collection of all these things and what cases like Clive Wearing demonstrate, they show us that that intuition is wrong, that you can indeed lose parts of the self while others remain so is it the same person? Well, it depends what you mean.
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Phil Stieg: In your Ted Talk and also in your book, you talk a little bit about the brain functioning as a prediction machine and how that is played out, I guess, as controlled hallucinations. Explain that concept to us, please.
Anil Seth: So this gets us back to this core idea of the fundamental job of the brain being to throw out predictions about what’s going on in the world, in the body, and update these predictions using sensory data.
Now, it might seem to most of us, most of the time that the world just pours itself into our minds through the transparent windows of our eyes and our ears, that it’s just there, and we sample it through our senses and we read it out somewhere inside our brain and build a picture of this external reality.
But that’s not what’s going on. And this is where the term controlled hallucination comes in.
What our brain is doing is interpreting inherently noisy and ambiguous and unlabeled sensory data to create an experience that is only ever indirectly related to what’s out there in the world. I mean, think about colors. Colors don’t objectively exist, and we don’t need neuroscience to tell us this. Physics tells us this.
The brain creates colors from combinations of colorless radiation, and I think the same is true for all aspects of our experience. There are all kinds of constructions. And this is why I like the term “controlled hallucination” because it emphasizes that our experience of the world, even though it seems to come from the outside in, we seem to read it out, and it’s just there, actually comes from the inside out.
Everything we experience is an act of creative interpretation on the basis of the brain, but it’s not an arbitrary one. It’s calibrated by sensory signals, controlled by the sensory signals in ways that are constrained by how useful it is, not by how things actually are. Colors are useful ways in which the brain interprets colorless information to help guide our behavior. So we see the world in ways that are useful for us, not as it is.
And there’s a continuity here between normal perception where our brain’s predictions are controlled by sensory signals in useful ways, and what typically in medicine and just in everyday language, we talk about hallucinations, which is usually perceptions that are not related to what’s there. When people see or hear things that aren’t there. And I think rather than being distinct categories, they’re all part of the same process. Just the balance is tipped. And when we actually hallucinate, our brain’s predictions have lost their grip on their causes in the world.
Phil Stieg: So that takes me to the next hot topic, artificial intelligence. You can’t turn on 60 Minutes without seeing a special show on artificial intelligence these days. And when they interview the leaders of all the corporations playing in this arena, they use the word, well, you know, every now and again they hallucinate, which is the word that you use. They’ve given examples of AI creating literature that actually didn’t exist to justify the answer to a question.
Anil Seth: I think the right word to describe what they do is not hallucinate, but confabulate.
Phil Stieg: …or lie.
Anil Seth: Well, I think lying involves intent. These language models, they don’t actually know or understand anything. We humans, we’re very anthropomorphic creatures. We’re very susceptible to projecting humanlike qualities into things on the basis of superficial similarities. And language models – they’re surprisingly good at certain things. But the fact that they can generate fluent language doesn’t mean they do it in the same way that we do it. That requires an actual understanding of the concepts involved and so on. They’re trained on basically everything that’s ever been written to predict the next part of a word. And when you do that, perhaps it’s not so surprising that you get a system that can generate fluent language in the absence of understanding.
Phil Stieg: Well, I’m glad. I think you would agree with me that it’s a long time before a computer is going to replace us as humans when it comes to judgment and deeper cognitive components.
Anil Seth: I mean, I hope they never replace us. And I think that’s, in a sense, the wrong way to look at AI. And it’s sort of motivated by, I think, very tenacious science fiction tropes of Terminators and Hal 9000 and so on.
AI in my view, and this comes from a mentor of mine, Daniel Dennett, the philosopher, who said we should always think of AI as tools rather than colleagues and be mindful of that difference. And I think a mature AI will complement human intelligence, not replace it.
The challenges here are partly technological. How do we build systems that do that? What kind of system should we be trying to design? At the moment people build things because they’re powerful and cool, but what should we be actually aiming for? And so that’s one issue. I think we should be going for something like an oracle, something that we can trust to give us useful information, but that has no goals or objectives of its own.
And then the second challenge is more sociological rather than scientific or technological. How do we learn to live in a society where we’re interacting with systems that give us the appearance of being conscious or of having minds or of understanding things. This is a challenge that we’re just encountering now, and maybe it will be easier over generations. But the problem is this technology is developing so quickly that we don’t have much time to figure out how to integrate it productively into society.
Phil Stieg: Tell me a little bit about your study. Something that you’re very close to right now I believe is called the Perception Census. What are you doing with that?
Anil Seth: Yeah, it’s indeed a study that we’re still collecting data for. And if any of your listeners are interested in participating, it would be wonderful if they would.
Phil Stieg: Is there a website they can reach?
Anil Seth: There is a website. The easiest way to find it, to be honest, is to either just type in the Perception Census or even my website, anilseth.com, it’ll take you right there.
The idea of this study is to look at one of the implications of the notion of perception as a kind of controlled hallucination, which is that even for the same shared reality, we will all have slightly different experiences. Our experience of the world, if it comes from the inside out rather than from the outside in, will depend on the particularities of your brain, of my brain. And just as we all differ on the outside in skin color and height and so on, we’re all going to differ on the inside too. But these differences are much harder to recognize for two reasons.
Firstly, because they can be relatively small. Bigger differences surface into behavior and language, but if I say, yeah, I see a red car across the street and you’re standing next to me and you say, oh yeah, I see a red car across the street, we’ll not know from that exchange of language that we’re having different experiences of red.
And the other reason it’s hard to surface these differences is because it just seems to us that we see the world as it is. It doesn’t seem that it would be different from me than from you.
So the Perception Census is a large-scale “citizen science” study where we’re trying to map out this hidden landscape of perceptual diversity. How we differ on the inside and what it consists in in practice is just a series of hopefully fun and engaging interactive illusions and very short, simple experiments that anyone at home can do. All you need is your own computer. Can’t do it on a phone. Unfortunately, you need a computer. But we look at many different aspects of perception, vision, hearing, time, all of these things, and we want to understand what’s happening that explains this hidden variability in how we encounter the world and the self.
Phil Stieg: Anil, thank you for spending this hour with us. It’s been enlightening. I’m glad to see that we’re blending the philosophical with the Neuroscientific approach to our understanding of consciousness. I’m hopeful that your enlighten us so that we continue to understand the importance of community in our human consciousness. Thank you so much.
Anil Seth: Thanks for having me.