Making Sense - Sam Harris - #113 — Consciousness and the Self

00:00:00.000 Today I spoke with Anil Seth. He is a professor of cognitive and computational neuroscience at

00:00:22.940 the University of Sussex and founding co-director of the Sackler Center for Consciousness Science.

00:00:30.000 And he's focused on the biological basis of consciousness and is studying it in a very

00:00:35.860 multidisciplinary way, bringing neuroscience and mathematics and artificial intelligence

00:00:41.680 and computer science, psychology, philosophy, psychiatry, all these disciplines together

00:00:47.300 in his lab. He is the editor-in-chief of the academic journal Neuroscience of Consciousness,

00:00:54.180 published by Oxford University Press, and he has published more than a hundred research papers

00:01:00.660 in a variety of fields. His background is in natural sciences and computer science and AI,

00:01:09.100 and he also did postdoctoral research for five years at the Neurosciences Institute in San Diego

00:01:15.160 under Gerald Edelman, the Nobel laureate. And we cover a lot of ground here. We really get into

00:01:22.200 consciousness in all its aspects. We start with the hard problem, then talk about where consciousness

00:01:28.280 might emerge in nature, talk about levels of consciousness, anesthesia, sleep, dreams,

00:01:35.040 the waking state. We talk about perception as a controlled hallucination, different notions of the

00:01:41.900 self, conscious AI, many things here. I found it all fascinating, and I hope you do as well.

00:01:50.820 And so, without further delay, I bring you Anil Seth.

00:01:57.640 I am here with Anil Seth. Anil, thanks for coming on the podcast.

00:02:01.820 Thanks for inviting me. It's a pleasure.

00:02:03.940 So, I think I first discovered you, I believe I'd seen your name associated with various papers,

00:02:10.460 but I think I first discovered you the way many people had after your TED Talk. You gave a much-loved

00:02:16.880 TED Talk. Perhaps you can briefly describe your scientific and intellectual background.

00:02:22.520 It's quite a varied background, actually. I mean, I think my intellectual interest has always been in

00:02:27.440 understanding the physical and biological basis of consciousness and what practical implications

00:02:33.520 that might have in neurology and psychiatry. But, you know, when I was an undergrad student at

00:02:40.200 Cambridge in the early 1990s, consciousness was certainly as a student then, and then in a place

00:02:46.620 like Cambridge, not a thing you could study scientifically. It was still very much a domain

00:02:51.560 of philosophy. And I was still, at that time, I still had this kind of idea that physics was going

00:02:58.440 to be the way to solve every difficult problem in science and philosophy. So, I started off

00:03:04.480 studying physics. But then, through the undergrad years, I got diverted towards psychology as more

00:03:11.080 of a direct route to these issues of great interest and ended up graduating with a degree in experimental

00:03:17.020 psychology. After that, I moved to Sussex University, where I am now, actually, again, to do a

00:03:23.880 master's and a PhD in computer science and AI. And this was partly because of the need, I felt,

00:03:31.200 the time to move beyond these box and arrow models of cognition that were so dominating psychology and

00:03:38.020 cognitive science in the 90s towards something that had more explanatory power. And the rise of

00:03:44.720 connectionism and all these new methods and tools in AI seemed to provide that. So, I stayed at Sussex and

00:03:53.320 did a PhD, actually, in an area which is now called artificial life. And I became quite diverted,

00:03:58.960 actually, ended up doing a lot of stuff in ecological modelling and thinking a lot more here about how

00:04:04.180 brains, bodies and environments interact and co-construct cognitive processes. But I'd sort of

00:04:10.300 left consciousness behind a little bit then. And so, when I finished my PhD in 2000, I went to San Diego to

00:04:18.080 the Neuroscience Institute to work with Gerald Edelman. Because certainly then, San Diego was

00:04:23.340 one of the few places, certainly that I knew of at the time, that you could legitimately study

00:04:29.180 consciousness and work on the neural basis of consciousness. Edelman was there, Francis Crick

00:04:33.520 was across the road at the Salk Institute. People were really doing this stuff there. So, I stayed there

00:04:38.600 for about six years and finally started working on consciousness, but bringing together all these

00:04:44.220 different, you know, different traditions of math, physics, computer science, as well as the tools of

00:04:50.080 cognitive neuroscience. And then, for the last 10 years, I've been back at Sussex, where I've been

00:04:54.660 running a lab. And it's called the Sackler Center for Consciousness Science. And it's one of the growing

00:05:01.040 number of labs that are explicitly dedicated to solving or studying, at least, the brain and biological

00:05:07.660 basis of consciousness. Yeah, well, that's a wonderful pedigree. I've heard stories, and I never

00:05:13.440 met Edelman. I've read his books, and I'm familiar with his work on consciousness. But he was famously

00:05:20.080 a titanic ego, if I'm not mistaken. I don't want you to say anything you're not comfortable with. But

00:05:25.700 everyone who I've ever heard have an encounter with Edelman was just amazed at how much space he

00:05:32.580 personally took up in the conversation. I've heard that too. And I think, you know, there's some truth to that.

00:05:37.500 What I can say from the other side is that when I worked for him and with him, you know, firstly,

00:05:43.220 it was an incredible experience. And I felt very lucky to have that experience, because he had a

00:05:48.220 large ego, but he also knew a lot too. I mean, he really had been around and had contributed to

00:05:53.160 major revolutions in biology and in neuroscience. But he treated the people he worked with, I think,

00:05:59.320 often very kindly. And one of the things that was very clear in San Diego at the time,

00:06:05.120 he didn't go outside of the Neurosciences Institute that much. It was very much his empire. But when

00:06:11.420 you were within it, you got a lot of his time. So, you know, I remember many occasions just being in

00:06:16.360 the office. And, you know, most days, I would be called down for a discussion with Edelman about

00:06:21.360 this subject or that subject or this new paper or that new paper. And that was a very instructive

00:06:26.840 experience for me. I know he was quite difficult in many interviews and conversations outside

00:06:32.960 the NSI, which is a shame, I think, because his legacy really is pretty extraordinary. I'm sure

00:06:38.780 we'll get onto this later. But one of the other reasons I went there was one of the main reasons

00:06:43.360 I went there was because I'd read some of the early work on dynamic core theory, which has later

00:06:48.960 become Giulio Tononi's very prominent integrated information theory. And I was under the impression

00:06:55.140 that Giulio Tononi was still going to be there when I got there in 2001, but he hadn't, he left.

00:07:01.380 And he wasn't really speaking much with Edelman at the time. And it was a shame that they didn't

00:07:07.000 continue their interaction. And, you know, when we tried to organize a festschrift, a few of us,

00:07:13.100 for Edelman some years ago now, it was quite difficult to get the people together that had

00:07:19.600 really been there and worked with him at various times of his career. I think of the people that

00:07:26.780 have gone through the NSI and worked with Edelman, there are extraordinary range of people who've

00:07:30.320 contributed huge amounts, not just in consciousness research, but in neuroscience generally, and of

00:07:34.500 course, in molecular biology before that. So it was a great, great experience for me. But yeah,

00:07:39.560 I know he could also be pretty difficult at times too. He had to have a pretty thick skin.

00:07:44.740 So, well, we have a massive interest in common. No doubt we have many others, but consciousness is

00:07:50.260 really the center of the bullseye as far as my interests go. And really, as far as anyone's

00:07:56.860 interests go, if they actually think about it, it really is the most important thing in the universe

00:08:01.820 because it's the basis of all of our happiness and suffering and everything we value. It's the space

00:08:08.940 in which anything that matters can matter. So the fact that you are studying it and thinking about

00:08:15.080 it as much as you are just makes you the perfect person to talk to. I think we should start with

00:08:21.560 many of the usual starting points here because I think they're the usual starting points for a reason.

00:08:26.980 Let's start with a definition of consciousness. How do you define it now?

00:08:31.360 I think it's kind of a challenge to define consciousness. There's a sort of easy folk definition,

00:08:36.300 which is that consciousness is the presence of any kind of subjective experience whatsoever.

00:08:42.560 For a conscious organism, there is a phenomenal world of subjective experience that has the

00:08:49.220 character of being private, that's full of perceptual qualia or content, colors, shapes, beliefs,

00:08:56.820 emotions, other kinds of feeling states. There is a world of experience that can go away

00:09:02.580 completely in states like general anesthesia or dreamless sleep. It's very easy to define it that

00:09:08.060 way. To define it more technically is always going to be a bit of a challenge. And I think sometimes

00:09:14.360 there's too much emphasis put on having a consensus technical definition of something like consciousness

00:09:21.260 because history of science has shown us many times that definitions evolve along with our scientific

00:09:27.080 understanding of a phenomenon. We don't sort of take the definition and then transcribe it into

00:09:31.020 scientific knowledge in a unidirectional way. So, so long as we're not talking past each other and

00:09:36.420 we agree that consciousness picks out a very significant phenomenon in nature, which is the

00:09:43.840 presence of subjective experience, then I think we're on reasonably safe terrain.

00:09:48.980 Many of these definitions of consciousness are circular. We're just substituting another word for

00:09:55.100 consciousness in the definition, like sentience or awareness or subjectivity or even something like

00:10:01.520 qualia, I think is parasitic on the undefined concept of consciousness.

00:10:06.180 Sure, I think that's right. But then there's also a lot of confusions people make too. So,

00:10:09.740 I'm always surprised by how often people confuse consciousness with self-consciousness.

00:10:14.580 And I think our conscious experience of selfhood are part of conscious experiences as a whole,

00:10:21.200 but only a subset of those experiences. And then there are arguments about whether there's such

00:10:29.740 a thing as phenomenal consciousness that's different from access consciousness, where

00:10:33.460 phenomenal consciousness refers to, you know, this impression that we have of a very rich

00:10:38.960 conscious scene, perhaps envisioned before us now, that might exceed what we have cognitive access

00:10:45.120 to. And other people will say, well, no, there's no such thing as phenomenal consciousness beyond

00:10:49.600 access consciousness. So, there's a certain circularity, I agree with you there, but there

00:10:54.500 are also these important distinctions that can lead to a lot of confusion when we're discussing

00:10:59.240 the relevance of certain experiments.

00:11:01.980 And I want to just revisit the point you just made about not transcribing a definition of a

00:11:08.380 concept that we have into our science as a way of capturing reality. And there are things about

00:11:14.080 which we have a folk psychological sense, which completely break apart once you start studying

00:11:20.160 them at the level of the brain. So, something like memory, for instance, we have the sense that it's

00:11:25.060 one thing intuitively, you know, pre-scientifically. We have the sense that to remember something,

00:11:32.220 whatever it is, is more or less the same operation, regardless of what it is. Remembering what you

00:11:39.020 ate for dinner last night, remembering your name, remembering who the first president of the United

00:11:43.840 States was, remembering how to swing a tennis racket. These are things that we have this one word for,

00:11:51.880 but we know neurologically that they're quite distinct operations, and you can disrupt one and

00:11:57.280 have the other intact. The promise has been that consciousness may be something like that,

00:12:02.900 that we could be similarly confused about it, although I don't think we can be. I think consciousness

00:12:08.560 is unique as a concept in this sense, and this is why I'm taken in more by the so-called hard

00:12:16.100 problem of consciousness than I think you are. I think we should talk about that, but before we do,

00:12:22.060 I think the definition that I want to put in play, which I know you're quite familiar with,

00:12:27.060 is the one that the philosopher Thomas Nagel put forward, which is that consciousness is the fact

00:12:33.520 that it's like something to be a system, whatever that system is. So if a bat is conscious, this comes

00:12:39.880 from his famous essay, What Is It Like To Be A Bat? If a bat is conscious, whether or not we can

00:12:45.660 understand what it's like to be a bat, if it is like something to be a bat, that is consciousness in

00:12:52.560 the case of a bat. However inscrutable it might be, however impossible it might be to map that experience

00:12:58.160 onto our own. If we were to trade places with a bat, that would not be synonymous with the lights going

00:13:04.440 out. There is something that it's like to be a bat if a bat is conscious. That definition, though, it's

00:13:10.260 really not one that is easy to operationalize, and it's not a technical definition. There's something

00:13:16.480 sufficiently rudimentary about that that it has always worked for me, and when we begin to move away

00:13:23.900 from that definition into something more technical, my experience has been, and we'll get to this as

00:13:30.940 we go into the details, that the danger is always that we wind up changing the subject to something

00:13:36.240 else that seems more tractable. We're no longer talking about consciousness in Nagel's sense, we're

00:13:42.280 talking about attention, or we're talking about reportability, or mere access, or something. So how do

00:13:49.880 you feel about Nagel's definition as a starting point? I like it very much as a starting point. I

00:13:54.860 think it's pretty difficult to argue with that as a very basic fundamental expression of what we mean

00:14:03.940 by consciousness in the round. So I think that's fine. I partly disagree with you. I partly disagree

00:14:11.640 with you, I think, when we think about the idea that consciousness might be more than one thing. And here,

00:14:19.120 I'm much more sympathetic to the view that, heuristically at least, the best way to scientifically

00:14:24.420 study consciousness, and philosophically to think about it as well, is to recognize that we might be

00:14:30.240 misled about the extent to which we experience consciousness as a unified phenomenon. And there's

00:14:36.940 a lot of mileage in recognizing how, just like the example for memory, recognizing how conscious

00:14:42.860 experiences of the world and of the self can come apart in various different ways.

00:14:47.320 Just to be clear, actually, I agree with you there. We'll get into that. But I completely agree with

00:14:52.040 you there that we could be misled about how unified consciousness is. The thing that's irreducible to

00:14:57.980 me is this difference between there being something that it's like and not. You know, the lights are on or

00:15:05.540 they're not. There are many different ways in which the lights can be on in ways that would surprise us.

00:15:11.320 For instance, it's quite possible that the lights are on in our brains in more than one spot. We'll

00:15:19.120 talk about split brain research, perhaps. But there are very counterintuitive ways the lights could be

00:15:23.680 on. But just the question is always, is there something that it's like to be that bit of

00:15:29.140 information processing or that bit of matter? And that is always the cash value of a claim for

00:15:35.660 consciousness. Yeah, I'd agree with that. I think that it's perfectly reasonable to put the question

00:15:40.380 in this way, that for a conscious organism, it is something like it is to be that organism. And

00:15:46.600 the thought is that there's going to be some physical, biological, informational basis to that

00:15:53.940 distinction. Now, you've written about why we really don't need to waste much time on the hard

00:16:01.200 problem. Let's remind people what the hard problem is. David Chalmers has been on the podcast,

00:16:06.780 and I've spoken about it with other people. But perhaps you want to introduce us to the hard

00:16:11.140 problem briefly. The hard problem has been, rightly so, one of the most influential philosophical

00:16:17.760 contributions to the consciousness debate for the last 20 years or so. And it goes right back to

00:16:24.920 Descartes. And I think it encapsulates this fundamental mystery that we've started talking about now,

00:16:30.600 that for some physical systems, there is also this inner universe, there is the presence of

00:16:39.300 conscious experience, there is something it is like to be that system. But for other systems,

00:16:43.080 tables, chairs, probably most computers, probably all computers these days, there is nothing it is

00:16:48.760 like to be that system. And what the hard problem does, it pushes that intuition a bit further, and

00:16:54.740 it distinguishes itself from the easy problem in neuroscience. And the easy problem, according to

00:16:59.620 Chalmers, is to figure out how the brain works in all its functions, in all its detail. So to figure

00:17:07.020 out how we do perception, how we utter certain linguistic phrases, how we move around the world

00:17:12.280 adaptively, how the brain supports perception, cognition, behavior in all its richness, in a way

00:17:17.780 that would be indistinguishable from, and here's the key really, in a way that would be indistinguishable

00:17:23.820 from an equivalent that had no phenomenal properties at all, that completely lacked

00:17:29.600 conscious experience. The hard problem is understanding how and why any solution to the

00:17:35.760 easy problem, any explanation of how the brain does what it does in terms of behavior, perception,

00:17:40.640 and so on, how and why any of this should have anything to do with conscious experiences at all.

00:17:45.980 And it rests on this idea of the conceivability of zombies, and this is one reason I don't really

00:17:52.180 like it very much. I mean, the hard problem has its conceptual power over us because it asks us to

00:17:58.480 imagine systems, philosophical zombies, that are completely equivalent in terms of their function

00:18:05.540 and behavior to you or to me or to any or to a conscious bat, but that instantiate no phenomenal

00:18:13.360 properties at all, the lights are completely off for these philosophical zombies. And if we can

00:18:19.740 imagine such a system, if we can imagine such a thing, a philosophical zombie, you or me,

00:18:24.660 then it does become this enormous challenge. You think, well, then what is it or what could it be

00:18:30.600 about real me, real you, real conscious bat? That gives rise, that requires or entails that there are

00:18:39.360 also these phenomenal properties, that there is something it is like to be you or me or the bat.

00:18:46.280 And it's because Chalmers would argue that such things are conceivable, that the hard problem seems

00:18:53.140 like a really huge problem. Now, I think this is a little bit of a, I think we've moved on a little

00:19:00.100 bit from these conceivability arguments. Firstly, I just think that they're pretty weak. And the more you

00:19:06.540 know about a system, the more we know about the easy problem, the less convincing it is to imagine

00:19:13.840 a zombie alternative. Think about, you know, you're a kid, you look up at the sky and you see a 747

00:19:21.460 flying overhead. And somebody asks you to imagine a 747 flying backwards. Well, you can imagine a 747

00:19:27.420 flying backwards. But the more you learn about aerodynamics, about engineering, the harder it is

00:19:32.760 to conceive of a 747 flying backwards. You know, you simply can't build one that way. And that's my worry

00:19:38.900 about this kind of conceivability argument, that to me, I really don't think I can imagine in a serious

00:19:44.860 way the existence of a philosophical zombie. And if I can't imagine a zombie, then the hard problem loses

00:19:51.640 some of its force.

00:19:53.480 That's interesting. I don't think it loses all of its force, or at least it doesn't for me. For me, the hard

00:19:58.740 problem has never really rested on the zombie argument, although I know Chalmers did a lot with

00:20:04.800 the zombie argument. I mean, so let's just stipulate that philosophical zombies are impossible. They're at

00:20:12.180 least, you know, what's called in the jargon, nomologically impossible. It's just a fact that we

00:20:17.500 live in a universe where if you built something that could do what I can do, that something would

00:20:22.700 be conscious. So there is no zombie Sam that's possible. And let's just also add what you just

00:20:29.260 said, that really, when you get to the details, you're not even conceiving of it being possible.

00:20:36.000 It's not even conceptually possible. You're not thinking it through enough. And if you did, you would

00:20:40.740 notice it break apart. But for me, the hard problem is really that with consciousness, any explanation

00:20:48.560 doesn't seem to promise the same sort of intuitive closure that other scientific explanations do.

00:20:59.420 It's analogous to whatever it is, and we'll get to some of the possible explanations, but it's not like

00:21:06.000 something like life, which is an analogy that you draw and that many scientists have drawn to how we can

00:21:13.300 make a breakthrough here. It used to be that people thought life could never be explained in mechanistic

00:21:18.920 terms. There was a philosophical point of view called vitalism here, which suggested that you

00:21:25.620 needed some animating spirit, some Elan Vital in the wheelworks to make sense of the fact that living

00:21:33.180 systems are different from dead ones, the fact that they can reproduce and repair themselves from injury

00:21:39.000 and metabolize and all the functions we see a living system engage, which define what it is to be

00:21:45.940 alive. It was thought very difficult to understand any of that in mechanistic terms, and then lo and

00:21:52.220 behold, we managed to do that. The difference for me is, and I'm happy to have you prop up this analogy

00:21:59.820 more than I have, but the difference for me is that everything you want to say about life, with the

00:22:05.360 exception of conscious life, we have to leave consciousness off the table here, everything

00:22:10.580 else you want to say about life can be defined in terms of extrinsic functional relationships among

00:22:18.140 material parts. So, you know, reproduction and growth and healing and metabolism and homeostasis, all of this

00:22:25.460 is physics and need not be described in any other way. And even something like perception, you know,

00:22:33.580 the transduction of energy, you know, let's say, you know, vision, light energy into electrical and

00:22:40.140 chemical energy in the brain, and then the mapping of a visual space onto a visual cortex, all of that

00:22:46.220 makes sense in mechanistic physical terms until you add this piece of, oh, but for some of these

00:22:53.480 processes, there's something that it's like to be that process. For me, it just strikes me as a false

00:22:59.340 analogy, and with or without zombies, the hard problem still stays hard.

00:23:06.120 I think it's an open question whether the analogy will turn out to be false or not. It's difficult

00:23:11.060 for us now to put ourselves back in the mindset of somebody 80 years ago, 100 years ago, when vitalism

00:23:17.400 was quite prominent, and whether the sense of mystery surrounding something that was alive

00:23:24.540 seemed to be as inexplicable as consciousness seems to us today. So it's easy to say with hindsight,

00:23:33.180 I think, that life is something different. But, you know, we've encountered, or rather,

00:23:38.220 scientists and philosophers over centuries have encountered things that have seemed to be

00:23:43.240 inexplicable, that have turned out to be explicable. So I don't think we should rule out

00:23:49.520 a priori that there's going to be something really different this time about consciousness.

00:23:58.060 There's, I think, a more heuristic aspect to this is that if we run with the analogy of life,

00:24:04.380 what that leads us to do is to isolate the different phenomenal properties that co-constitute

00:24:12.380 what it is for us to be conscious. We can think about, and we'll come to this, I'm sure we think

00:24:17.000 about conscious selfhood as distinct from conscious perception of the outside world. We can think

00:24:21.360 about conscious experiences of volition and of agency that are also very sort of central to our,

00:24:28.300 certainly our experience of self. These give us phenomenological explanatory targets

00:24:34.040 that we can then try to account for with particular kinds of mechanisms.

00:24:39.200 It may turn out at the end of doing this that there's some residue. There is still something

00:24:45.260 that is fundamentally puzzling, which is this hard problem residue. Why are there any lights on for

00:24:53.720 any of these kinds of things? Isn't it all just perception? But maybe it won't turn out like that.

00:24:59.900 And I think to give us the best chance of it not turning out like that, there's a positive and a

00:25:06.300 negative aspect. The positive aspect is that we need to retain a focus on phenomenology.

00:25:13.620 And this is another reason why I think the hard easy problem distinction can be a little bit

00:25:19.820 unhelpful because in addressing the easy problem, we are basically instructed to not worry about

00:25:27.080 phenomenology. All we should worry about is function and behavior. And then the hard problem

00:25:31.740 kind of gathers within its remit everything to do with phenomenology in this central mystery of why

00:25:37.500 is that some experience rather than no experience. The alternative approach, and this is something I've

00:25:42.480 kind of caricatured as the real problem, but David Chalmers himself has called it the mapping problem

00:25:47.140 and Varela, Francisco Varela talks about a similar set of ideas with his neurophenomenology,

00:25:54.540 is to not try to solve the hard problem to court, not try to explain how it is possible that

00:26:01.520 consciousness comes to be part of the universe, but rather to individuate different kinds of

00:26:06.920 phenomenological properties and draw some explanatory mapping between neural, biological, physical

00:26:13.840 mechanisms and these phenomenological properties. Now, once we've done that and we can begin to explain

00:26:19.400 not why is their experience at all, but why are certain experiences the way they are and not other

00:26:24.900 ways? And we can predict when certain experiences will have particular phenomenal characters and so

00:26:32.800 on. Then we'll have done a lot more than we can currently do. And we may have to make use of

00:26:39.100 novel kinds of conceptual frameworks, maybe frameworks like information processing will run their course and

00:26:45.040 will require other more sophisticated kinds of descriptions of dynamics and probability in

00:26:50.260 order to build these explanatory bridges. So I think we can get a lot closer. And the negative aspect is

00:26:56.380 why should we ask more of a theory of consciousness than we should ask of other kinds of scientific

00:27:03.140 theories? And I know people have talked about this on your podcast before as well, but we do seem to

00:27:10.540 want more of an explanation of consciousness than we would do of an explanation in biology or physics,

00:27:16.600 that it somehow should feel intuitively right to us. And I wonder why this is such a big deal when it

00:27:25.600 comes to consciousness. Because we're trying to explain something fundamental about ourselves doesn't

00:27:32.420 necessarily mean that we should apply different kinds of standards to an explanation that we would

00:27:37.040 apply in other fields of science. It just may not be that we get this feeling that something is

00:27:44.880 intuitively correct when it is in fact a very good scientific account of the origin of phenomenal

00:27:52.260 properties. Certainly, scientific explanations are not instantiations. There's no sense in which

00:27:58.420 a good theory of consciousness should be expected to suddenly realize the phenomenal properties

00:28:03.160 that it's explaining. But also, I think we, yeah, we do, I worry that we ask too much of theories of

00:28:08.940 consciousness this way. Yeah, well, we'll move forward into the details. And I'll just flag moments

00:28:13.740 where I feel like the hard problem should be causing problems for us. I do think it's not a matter of

00:28:20.820 asking too much of a theory of consciousness here. I think it's, there are very few areas in science where

00:28:26.060 the accepted explanation is totally a brute fact, which just has to be accepted because it is the

00:28:34.860 only explanation that works, but it's not something that actually illuminates the transition from,

00:28:41.620 you know, atoms to some higher level phenomenon. So again, for everything we could say about life,

00:28:48.280 even the very strange details of molecular biology, just how information in the genome gets out,

00:28:55.740 and creates the rest of a human body, it still runs through when you look at the details. It's

00:29:04.380 surprising, it's at parts difficult to visualize, but the more we visualize it, the more we describe it,

00:29:11.260 the closer we get to something that is highly intuitive, even something like, you know, the flow of

00:29:17.540 water. The fact that water molecules in its liquid state are loosely bound and move past one another,

00:29:24.520 well, that seems exactly like what should be happening at the micro level, so as to explain

00:29:30.300 the macro level property of the wetness of water and the fact that it has characteristics, higher level

00:29:36.400 characteristics that you can't attribute to atoms, but you can attribute to collections of atoms, like

00:29:41.600 turbulence, say. Whereas with, you know, if consciousness just happens to require some minimum number of

00:29:48.280 information processing units knit together in a certain configuration, firing at a certain

00:29:54.720 hertz, and you change any of those parameters and the lights go out, that, for me, still seems like

00:30:02.540 a mere brute fact that doesn't explain consciousness. It's just a correlation that we decide is the crucial

00:30:11.060 one. And I've never heard a description of consciousness, you know, of the sort that we will get to, like,

00:30:15.840 you know, integrated information, you know, Tononi's phrase, that unpacks it any more than that. And

00:30:23.360 you can react to that, but then I think we should just get into the details and see how it all sounds.

00:30:28.120 Sure. I'll just react very briefly, which is that I think I'd also be terribly disappointed if

00:30:33.240 the, you know, you look at the answer in A Book of Nature and it turned out to be, yes, you need

00:30:37.640 612,000 neurons wired up in a small world network and, you know, that's it. You know, the hope is,

00:30:45.240 that does seem, of course, ridiculous and arbitrary and unsatisfying. I mean, the hope is that as we

00:30:50.780 progress beyond, if you like, just brute correlates of conscious states towards accounts that provide

00:30:59.760 more satisfying bridges between mechanism and phenomenology that explain, for instance,

00:31:05.380 why a visual experience has the phenomenal character that it has and not some other

00:31:10.700 kind of phenomenal character like an emotion, that it won't seem so arbitrary. And that as we follow

00:31:17.780 this route, which is an empirically productive route, and I think that's important that if we can

00:31:23.900 actually do science with this route, we can try to think about how to operationalize phenomenology in

00:31:28.420 various different ways. Very difficult to think how to do science and just solve the hard problem

00:31:33.420 head on. At the end of that, I completely agree, there might be still this residue of mystery,

00:31:40.780 this kernel of something fundamental left unexplained. But I don't think we can take that

00:31:47.620 as a given because we can't, well, I certainly can't predict what I would feel as intuitively satisfying

00:31:54.740 when I don't know what the explanations that bridge mechanism and phenomenology are going to look

00:32:00.140 like in 10 or 20 years' time. We've already moved further from just saying it's this area or that

00:32:05.900 area, to synchrony, which is still kind of unsatisfying, to now, I think, some emerging

00:32:11.400 frameworks like predictive processing and integrated information, which aren't completely satisfying

00:32:18.380 either. But they hinted a trajectory where we're beginning to draw closer connections between

00:32:24.720 mechanism and phenomenology. Okay, well, let's dive into those hints. But before we do, I'm just

00:32:30.280 wondering, phylogenetically, in terms of comparing ourselves to so-called lower animals, where do you

00:32:37.580 think consciousness emerges? Do you think there's something that it's like to be a fly, say?

00:32:43.440 That's a really hard problem. I mean, I have to be agnostic about this. And again, it's just striking how

00:32:51.140 people in general's views on these things seems to have changed over the last recent decades. It seems

00:32:59.360 completely unarguable to me that other mammals, all other mammals, have conscious experiences of one

00:33:08.460 sort or another. I mean, we share so much in the way of the relevant neuroanatomy and neurophysiology

00:33:13.800 exhibit so many of the same behaviours that it would be remarkable to claim otherwise.

00:33:20.440 It actually wasn't that long ago that you could still hear people say that consciousness was so

00:33:26.620 dependent on language that they wondered whether human infants were conscious, to say nothing of

00:33:32.960 dogs and anything else that's not human. Yeah, that's absolutely right. I mean, that's a terrific

00:33:37.840 point. And this idea that consciousness was intimately and constitutively bound up with language or with

00:33:45.300 higher order executive processing of one sort or another, I think just exemplifies this really

00:33:52.060 pernicious anthropocentrism that we tend to bring to bear sometimes without realising it. We think

00:33:58.480 we're super intelligent, we think we're conscious, we're smart, and we need to judge everything by

00:34:02.740 that benchmark. And what's the most advanced thing about humans? Well, if you're gifted with language,

00:34:09.400 you're going to say language. And now already, with a bit of hindsight, seems to me anyway,

00:34:15.620 rather remarkable that people should make these, I can only think of them as just quite naive errors

00:34:23.280 to associate consciousness with language. It's not to say that consciousness and language don't have any

00:34:28.620 intimate relation. I think they do. Language shapes a lot of our conscious experiences. But certainly,

00:34:33.500 it's a very, very poor criterion with which to attribute subjective states to other creatures.

00:34:40.860 So mammals, for sure. I mean, mammals, for sure. But that's easy, because they're pretty similar

00:34:46.000 to humans and primates being mammals. But then it gets more complicated. And you think about birds

00:34:54.040 diverged a reasonable amount of time ago, but still have brain structures that one can establish

00:35:02.120 analogies, in some cases, homologies with mammalian brain structures. And in some species, scrub jays and

00:35:09.580 corvids generally, pretty sophisticated behavior too. It seems very possible to me that birds have

00:35:19.400 conscious experiences. And I'm aware, underlying all this, the only basis to make these judgments is in

00:35:25.340 light of what we know about the neural mechanisms underlying consciousness and the functional and behavioral

00:35:30.340 properties of consciousness in mammals. It has to be this kind of slow extrapolation, because we lack

00:35:34.800 the mechanistic answer, and we can't look for it in another species. But then you get beyond birds,

00:35:40.940 and you get out to, you know, I then like to go way out on a phylogenetic branch to the octopus,

00:35:49.680 which I think is an extraordinary example of convergent evolution. I mean, they're very smart,

00:35:54.820 they have a lot of neurons, but they diverged from the human line, I think, as long ago as sponges or

00:36:01.880 something like that. I mean, really, very little in common. And, but they have incredible differences

00:36:06.480 too. Three hearts, eight legs, arms, I'm never sure whether it's a leg or an arm, that behave semi-autonomously.

00:36:16.920 And one is left, you know, when you spend time with these creatures, I've been lucky enough to spend a

00:36:22.460 week with them in a lab in Naples. You certainly get the impression of another conscious presence

00:36:27.940 there, but of a very different one. And this is also instructive, because it brings us a little

00:36:34.500 bit out of this assumption that we can fall into, that there is one way of being conscious, and that's

00:36:41.240 our way. There's, you know, there is a huge space of possible minds out there. And the octopus is a very

00:36:49.120 definite example of a very different mind and very likely conscious mind too. Now, when we get down to,

00:36:59.040 yeah, not really down, I don't like this idea of organisms being arranged on a single scale like

00:37:05.300 this, but certainly creatures like fish, insects are simpler in all sorts of ways than mammals.

00:37:12.400 And here it's really very difficult to know where to draw the line, if indeed there is a line to be

00:37:18.000 drawn, if it's not just a gradual shading out of consciousness, that with gray areas in between,

00:37:25.120 and no categorical divide, which I think is equally possible. And fish, many fish display

00:37:31.640 behaviors which seem suggestive of consciousness, they will self-administer analgesia when they're

00:37:37.600 given painful stimulation. They will avoid places that have been associated with painful stimulation,

00:37:42.900 and so on. You hear things like the precautionary principle come into play, that given that

00:37:49.880 suffering, if it exists, conscious suffering is a very aversive state and it's ethically wrong to

00:37:55.820 impose that state on other creatures, we should tend to assume that creatures are conscious unless we have

00:38:04.740 good evidence that they're not. So we should put the bar a little bit lower in most cases.

00:38:12.480 Let's talk about some of the aspects of consciousness that you have identified as being distinct.

00:38:18.600 There are at least three. You've spoken about the level of consciousness, the contents of consciousness,

00:38:24.420 and the experience of having a conscious self that many people, as you said, conflate with consciousness

00:38:32.480 as a mental property. There's obviously a relationship between these things, but they're not the same.

00:38:38.440 Let's start with this notion of the level of consciousness, which really isn't the same thing

00:38:43.420 as wakefulness. Can you break those apart for me? How is being conscious non-synonymous with being

00:38:50.160 awake in the human sense? Sure. Let me just first amplify what you said, that in making these

00:38:57.500 distinctions, I'm certainly not claiming, pretending, that these dimensions of level, content, and self

00:39:05.000 pick out completely independent aspects of conscious experiences. There are lots of interdependencies.

00:39:11.260 I just think they're heuristically useful ways to address the issue. We can do different kinds of

00:39:17.520 experiments and try to isolate distinct phenomenal properties in their mechanistic basis by making

00:39:23.080 these distinctions. Now, when it comes to conscious level, I think that the simplest way to think of this

00:39:28.220 is more or less as a scale. In this case, it's from when the lights are completely out, when you're dead,

00:39:36.020 brain death, or under general anesthesia, or perhaps in very, very deep states of sleep,

00:39:41.820 all the way up to vague levels of awareness, which correlate with wakefulness. So when you're very

00:39:50.620 drowsy, to vivid, awake, alert, full conscious experience that I'm certainly having now, I feel

00:39:59.000 very awake and alert, and my conscious level is kind of up there. Now, in most cases, the level of

00:40:07.400 consciousness articulated this way will go along with wakefulness or physiological arousal. When you fall

00:40:15.140 asleep, you lose consciousness, at least in early stages. But there are certain cases that exist which

00:40:24.200 show that they're not completely the same thing on both sides. So you can be conscious when you're

00:40:32.440 asleep. Of course, we know this. This is called dreaming. So you're physiologically asleep, but you're

00:40:36.940 having a vivid inner life there. And on the other side, and this is where consciousness science,

00:40:43.740 the rubber of consciousness science hits the road of neurology, you have states where behaviorally,

00:40:49.020 you have what looks like arousal. This used to be called the vegetative state. It's been kind of

00:40:57.020 renamed several times now, the wakeful unawareness state, where the idea is that the body is still

00:41:03.140 going through physiological cycles of arousal from sleep to wake, but there is no consciousness

00:41:09.780 happening at all. The lights are not on. So these two things can be separated. And it's a very

00:41:20.980 productive and very important line of work to try to isolate what's the mechanistic basis of conscious

00:41:27.660 level independently from the mechanistic basis of physiological arousal.

00:41:32.960 Yeah. And a few other distinctions to make here. Also, general anesthesia is quite distinct from

00:41:39.500 deep sleep, just as a matter of neurophysiology.

00:41:43.040 Certainly, general anesthesia is nothing like sleep. Certainly, deep level is general anesthesia. So

00:41:49.280 whenever you go for an operation and the anesthesiologist is trying to make you feel

00:41:55.420 more comfortable by just saying something like, yeah, we'll just put you to sleep for a while and

00:41:59.320 then you'll wake up and it will be done. They are lying to you for good reason. It's kind of nice

00:42:05.180 just to feel that you're going to sleep for a bit. But the state of general anesthesia is very different.

00:42:09.580 And for very good reason, if you were just put into a state of sleep, you would wake up as soon as the

00:42:13.400 operation started and that wouldn't be very pleasant. It's surprising how far down you can take

00:42:19.320 people in general anesthesia, almost to a level of isoelectric brain activity where there is pretty much

00:42:24.880 nothing going on at all and still bring them back. And many people now have had the non-experience of

00:42:35.620 general anesthesia. And in some weird way, I now look forward to it the next time I get to have this

00:42:41.560 because it's a very sort of, it's almost a reassuring experience because there is absolutely

00:42:48.020 nothing. It's complete oblivion. It's not, you know, when you go to sleep as well,

00:42:51.380 you can sleep for a while and you'll wake up and you might be confused about what, how much time has

00:42:57.620 passed, especially if you've just flown across some time zones or stayed up too late, something

00:43:02.920 like that. You know, might not be sure what time it is, but you'll still have this sense of some time

00:43:07.600 having passed. Except we have this problem or some people have this problem of anesthesia awareness,

00:43:13.260 which is every person's worst nightmare if they care to think about it, where people have the

00:43:19.760 experience of the surgery because for whatever reason, the anesthesia hasn't taken them deep

00:43:26.260 enough and yet they're immobilized and can't signal that they're not deep enough.

00:43:30.700 I know, absolutely. But I mean, that's a failure of anesthesia. It's not a characteristic of the

00:43:34.500 anesthetic state.

00:43:35.760 Do you know who had that experience? You've mentioned him on the podcast.

00:43:39.100 I, really?

00:43:40.260 Francisco Varela.

00:43:41.580 Oh, really? I didn't know that. I did not know that.

00:43:44.280 Yeah. Francisco was getting a liver transplant and experienced some part of it.

00:43:51.280 Well, that's, that's pretty horrific.

00:43:53.340 Could not have been fun.

00:43:54.600 Yeah. I mean, of course, because the thing there is, you know, under most

00:43:57.300 serious operations, you're also administered with a muscle paralytic so that you don't jerk around

00:44:03.560 when you're being operated on. And that's why it's, it's particularly a nightmare scenario.

00:44:09.140 But, you know, if anesthesia is working properly, certainly the times I've had general anesthesia,

00:44:15.500 you start counting to 10 or start counting backwards from 10. You get to about eight and

00:44:21.280 then instantly you're back somewhere else, very confused, very disoriented. But there is

00:44:27.220 no sense of time having passed. It's just complete oblivion. And that, I found that really reassuring

00:44:34.580 because you, we can think conceptually about not being bothered about all the times we were not

00:44:40.320 conscious before we were born. And therefore we shouldn't worry too much about all the times we're

00:44:45.560 not going to be conscious after we die. But to experience these moments of complete oblivion

00:44:50.580 during a lifetime, or rather, you know, the edges of them, I think is a, is a very enlightening kind

00:44:58.260 of experience to have. Although there's a place here where the hard problem does emerge because

00:45:03.720 it's very difficult, perhaps impossible, to distinguish between a failure of memory and

00:45:09.780 oblivion. Has consciousness really been interrupted? Take anesthesia and deep sleep as separate but

00:45:17.100 similar in the sense that most people think there was a hiatus in consciousness. I'm prepared to believe

00:45:23.060 that that that's not true of deep sleep, but we just don't remember what it's like to be deeply

00:45:28.360 asleep. I'm someone who often doesn't remember his dreams and I'm prepared to believe that I dream

00:45:33.960 every night. And we know even in the case with general anesthesia, they give amnesic drugs so that

00:45:42.660 you won't remember whatever they don't want you to remember. And I recently had the experience of

00:45:47.940 not going under a full anesthesia, but having a, you know, what's called a twilight sleep for a

00:45:54.840 procedure. And there was a whole period afterwards where I was coming to about a half hour that I

00:46:01.880 don't remember. And it was clear to my wife that I wasn't going to remember it, but she and I were

00:46:06.760 having a conversation. I was talking to her about something. I was saying how, you know, perfectly

00:46:11.720 recovered I was and how miraculous it was to be back. And she said, yeah, but you're not going to

00:46:16.960 remember any of this. You're not going to remember this conversation. And I said, okay, well, let's

00:46:20.660 test it. You know, you say something now and we'll see if I remember it. And she said, she said, this

00:46:26.760 is the test, dummy. You're not going to remember this part of the conversation. And I have no memory

00:46:31.440 of that part of the conversation. It's a good test. Yeah. You're right, of course, that even in stages

00:46:39.500 of deep sleep, people underestimate the presence of conscious experiences. And this has been

00:46:44.500 demonstrated by experiments called serial awakening experiments, where you'll just wake somebody

00:46:50.160 up various times during sleep cycles and ask them straight away, you know, what was in your

00:46:55.000 mind? And quite often people will report often very simple sorts of experiences, static images

00:47:02.060 and so on in stages of non-REM, non-dreaming sleep. And I concede that there may be a contribution

00:47:10.620 of amnesia to the post hoc impression of what general anesthesia was like. But at the same

00:47:18.460 time, there's all the difference in the world between the twilight zone and full-on general

00:47:22.480 anesthesia, where it's not just that I don't remember anything. It's the real sense of a hiatus

00:47:28.560 of consciousness, of a complete interruption and a complete instantaneous resumption of that

00:47:33.560 experience.

00:47:34.080 Yeah, yeah. No, I've had a general anesthetic as well. And there is something quite uncanny

00:47:40.800 about disappearing and being brought back without a sense of any intervening time. Because you're

00:47:48.720 not aware of the time signature of having been in deep sleep, but there clearly is one. And

00:47:54.780 the fact that many people can go to sleep and kind of set an intention to wake up at a certain

00:48:00.180 time and they wake up at that time, often to the minute. It's clear there's some timekeeping

00:48:04.720 function happening in our brains all the while, but there's something about a general anesthetic

00:48:10.000 which just seems like, okay, the hard drive just got rebooted and who knows how long the computer

00:48:15.960 was off for.

00:48:17.060 Exactly.

00:48:18.060 Yeah. Okay, so let's talk about these other features. We've just dealt with the level of

00:48:22.100 consciousness. Talk to me about the contents of consciousness. How do you think about that?

00:48:26.820 When we are conscious, then we're conscious of something. And I think this is what the

00:48:33.240 large majority of consciousness research empirically focuses on. You take somebody who is conscious

00:48:40.300 at a particular time and you try to, you can ask a few different questions. You can ask what

00:48:47.240 aspects of their perception are unconscious and not reflected in any phenomenal properties and

00:48:54.520 what aspects of their perception are reflected in their phenomenal properties. What's the

00:48:59.420 difference between conscious and unconscious processing, if you like? What's the difference

00:49:03.880 between different modalities of conscious perception? So at any one time, we may, certainly

00:49:11.780 outside of the lab, our conscious scene at any one time, we'll have a very multimodal character.

00:49:17.580 So there'll be sound, sight, experiences of touch, maybe if you're sitting down or holding

00:49:23.440 something. And then a whole range of more self-related experiences too, of body ownership,

00:49:30.360 of all the signals coming from deep inside the body, which are more relevant to self.

00:49:33.960 But the basic idea of conscious content is to study what the mechanisms are that give rise

00:49:40.020 to the particular content of a conscious scene at any one time. And here, the reason it's useful

00:49:49.760 to think of this as separate from conscious level is partly that we can appeal to different kinds

00:49:56.600 of theories, different kinds of theoretical and empirical frameworks. So the way I like to think

00:50:04.740 about conscious perception is in terms of prediction, in terms of what's often been called the Bayesian

00:50:12.020 brain or unconscious inference from Helmholtz and so on. And the idea that perception in general

00:50:20.020 works more from the top down or from the outside in than from the... Sorry, I got that wrong.

00:50:27.740 Perception works more from the top down or the inside out rather than from the bottom up or the outside in.

00:50:34.740 And this has a long history in philosophy as well, back to Kant and long before that too. I mean,

00:50:41.000 the straw man, the kind of the easily defeated idea about perception is that sensory signals impinge

00:50:48.720 upon receptors and they percolate deeper and deeper into the brain. And at each stage of processing,

00:50:56.080 more complex operations are brought to bear. And at some point, ignition happens or something happens

00:51:02.580 and you're conscious of those sensory signals at that point. And I think this is kind of the wrong

00:51:09.420 way to think about it, that if you look at the problem of perception that brains face, and let's

00:51:16.820 simplify it a lot now and just assume the problem is something like the following, that the brain is

00:51:22.440 locked inside a bony skull. And let's assume for the sake of this argument that perception is the

00:51:29.020 problem of figuring out what's out there in the world that's giving rise to sensory signals that

00:51:33.720 impinge on our sensory surfaces, eyes and ears. Now, these sensory signals are going to be noisy

00:51:39.700 and ambiguous. They're not going to have a one-to-one mapping with things out there in the world,

00:51:43.540 whatever they may be. So perception has to involve this process of inference, of best guessing,

00:51:49.860 in which the brain combines prior expectations or beliefs about the way the world is with the sensory

00:51:55.380 data to come up with its best guess about the causes of that sensory data. And in this view,

00:52:01.480 what we perceive is constituted by these multi-level predictions that try to explain away or account for

00:52:10.880 the sensory signals. We perceive what the brain infers to have caused those signals,

00:52:16.360 not the sensory signals themselves. In this view, there's nothing that it is for there to be

00:52:21.960 raw sensory experience of any kind. All perceptual experience is an inference of one sort or another.

00:52:28.300 And given that view, one can then start to ask all sorts of interesting experimental questions like,

00:52:35.020 well, what kinds of predictions? How do predictions or expectations affect what we consciously perceive,

00:52:39.940 consciously report? What kinds of predictions may still go on under the hood and not instantiate any

00:52:46.780 phenomenal properties? But it gives us this set of tools that we can use to build bridges between

00:52:53.020 phenomenology and mechanism again. In this case, the bridges are made up of the computational

00:52:58.380 mechanisms of Bayesian inference as they might be implemented in neuronal circuitry. And so instead of

00:53:05.340 looking for, you know, asking questions like, is V1, is early visual cortex associated with visual

00:53:12.780 experience? We might ask questions like, are Bayesian priors or posteriors associated with

00:53:19.120 conscious phenomenology? Or are prediction errors associated with conscious phenomenology? We can

00:53:23.480 start to ask slightly, I think, more sophisticated bridging questions like that.

00:53:27.740 Well, yeah, in your TED Talk, you talk about consciousness as a controlled hallucination.

00:53:32.520 And I think Chris Frith has called it a fantasy that coincides with reality. Can you say a little

00:53:39.380 more about that and how that relates to the role of top-down prediction in perception?

00:53:46.600 Yeah, I think they're both very nice phrases. And I think the phrase controlled hallucination actually

00:53:53.120 has been very difficult to pin down where it came from. I heard it from Chris Frith as well,

00:53:58.000 originally. And I've asked him and others where originally it came from. And we can trace it to

00:54:03.440 a seminar given by Ramesh Jain at UCSD sometime in the 90s. But it was a verbal, there the trail goes

00:54:11.920 cold. But anyway, the idea is sort of the following, that we can bring to bear a naive realism about

00:54:18.220 perception where we assume that what we visually perceive is the way things actually are in the real

00:54:25.540 world. That there is a table in front of me that has a particular color that has a piece of paper on it

00:54:30.780 and so on. And that's veridical perception, as distinct from hallucination, where we have a

00:54:36.160 perceptual experience that has no corresponding reference in the real world. And the idea of

00:54:43.720 controlled hallucination or fantasy that coincides with reality is simply to say that normal perception

00:54:51.780 is always a balance of sensory signals coming from the world and the interpretations,

00:54:59.780 predictions that we bring to bear about the causes of those sensations. So we are always seeing what we

00:55:07.280 expect to see in this Bayesian sense. We never just see the sensory data. Now, normally, we can see

00:55:15.840 this all the time. It's built into our visual systems that light is expected to come from above because

00:55:22.120 our visual systems have evolved in a situation where the sun is never below us. So that causes us to

00:55:27.580 perceive shadows in a particular way. Rather, we'll perceive curved surfaces as being curved one way or

00:55:33.640 another under the assumption that light comes from above. We're not aware of having that constraint

00:55:40.160 built deep into our visual system, but it's there. And the idea is that every perception that we have

00:55:48.180 is constituted, partly constituted by these predictions, these interpretive powers that the

00:55:56.580 brain brings to bear onto perceptual content. And that what we call hallucinations is just the tipping

00:56:02.980 of the balance slightly more towards the brain's own internal predictions. And another good everyday

00:56:09.560 example of this is if you go out on a day where there's lots of white fluffy clouds, and you can see

00:56:14.660 faces in clouds. If you choose, if you look for them, it's periordelia, you can see patterns,

00:56:18.780 you can see patterns in noise. Now, that's a kind of hallucination there. You're seeing something

00:56:23.520 that other people might not see. And it's not accompanied by delusion. You know, it's a

00:56:30.840 hallucination. But it's still, it just shows how our perceptual content is always framed by our

00:56:37.060 interpretation. Another good everyday example is dreams, because of dreams, we know are a situation

00:56:44.120 where our brain is doing something very similar to what it's doing in the waking state, except the

00:56:49.700 frontal lobes have come offline enough so that there's just not the same kind of reality testing

00:56:56.260 going on. And our perception in this case is not being constrained by outer stimuli. It's just,

00:57:03.680 it's being generated from within. But would this be an analogous situation where our top-down

00:57:09.460 prediction mechanisms are roving, unconstrained by sensory data?

00:57:15.020 I think, yeah, dreams certainly show that you don't need sensory data to have vivid conscious

00:57:21.120 perception, because you don't have any sensory input, apart from a bit of auditory input when

00:57:25.900 you're dreaming. I think the phenomenology of dreams is interestingly different. Yeah, dream content is

00:57:32.660 very much less constrained. There is this naive realism just goes nuts in dreams, doesn't it? I mean,

00:57:38.480 things can change, people can change, identity locations can change, weird things happen all the

00:57:42.320 time you don't experience them as being weird. That's the weirdest part of dreams, the fact that

00:57:47.440 it's not that they're so weird, it's that the weirdness is not detected. We don't care that

00:57:53.140 they're so weird. Yeah, which is, I think, a great example of how we often overestimate the insight we

00:58:00.520 have about what our conscious experiences are like. We tend to assume that we know exactly what's

00:58:06.600 happening in all our conscious experiences all the time, whether it's weird or not. Dreams show that

00:58:10.480 that's not always the case. But I think the idea of controlled hallucination goes, it's as present

00:58:17.200 in the normal, in non-dreaming perception as it is in dreaming. And it really is this idea that

00:58:24.520 all our perception is constituted by our brain's predictions of the causes of sensory input.

00:58:31.260 And most of the time, walking around the world, we will agree about this perceptual content. If I see a

00:58:37.900 table and claim it's this colour, you'll probably agree with me. And we don't have to go into the

00:58:42.640 philosophical inverted spectra thing here. It's just a case of we tend to report the same sorts of

00:58:47.340 things when faced with the same sorts of sensory inputs. So we don't think there's anything

00:58:54.100 particularly constructed about the way we perceive things, because we all agree on it. But then when

00:59:01.000 something tips the balance, maybe it's under certain pharmacological stimulus, maybe it's

00:59:05.740 in dreams, maybe it's in certain states of psychosis and mental illness, then people's

00:59:12.380 predictions about the causes of sensory information will differ from one another. And if you're an

00:59:17.960 outlier, then people will say, oh, now you're hallucinating because you're reporting something that

00:59:22.860 isn't there. And my friend, the musician Baba Brinkman put it beautifully. He said, you know,

00:59:29.360 what we call reality is just when we all agree about our hallucinations, which I think is a really

00:59:34.620 nice way to put that. This leaves open the question, what is happening when we experience

00:59:40.500 something fundamentally new, or have an experience where our expectations are violated? So we're using

00:59:47.340 terms like predictions or expectations or models of the world. But I think there's a scope for some

00:59:55.400 confusion here. Just imagine, for instance, that some malicious zookeeper put a fully grown tiger in

01:00:03.280 your kitchen while you were sleeping tonight. I presume that when you come down for your morning

01:00:08.340 coffee, you will see this tiger in the kitchen, even though you have no reasonable expectation to

01:00:15.780 be met by a tiger in the morning. I think it's safe to assume you'll see it even before you've had

01:00:20.140 your cup of coffee. So given this, what do we mean by expectations at the level of the brain?

01:00:27.360 That's a very, very important point. It's this whole language of the Bayesian brain and predictive

01:00:33.760 processing bandies around terms like prediction expectation and prediction error, surprise, and all these

01:00:40.140 things. It's very, very important to recognize that these terms don't only mean or don't really mean at

01:00:48.180 all psychological surprise or explicit beliefs and expectations that I might hold. So certainly,

01:00:54.800 if I go down morning, I am not expecting to see a tiger. However, my visual system, when it encounters

01:01:04.480 a particular kind of input, it's still expecting, you know, if there are sensory input that pick out

01:01:11.760 things like edges, it will best interpret those as an edge. And if it will pick out stripes, it will

01:01:17.680 interpret those as stripes. It's not unexpected to see something with an edge, and it may not be

01:01:23.780 unexpected to see something with a stripe. It may not even be unexpected from my brain's point of view

01:01:28.700 to see something that looks a bit like a face. And those become low-level best guesses about the

01:01:35.900 causes of sensory input, which then give rise to higher-level predictions about those causes.

01:01:42.000 And ultimately, the best guess is that there's some kind of animal there, and indeed, that it's a tiger.

01:01:49.020 So I don't think there's a conflict here. We can see new things, because new things are built up

01:01:54.960 from simpler elements for which we will have adequate predictions for, built up over evolution

01:02:01.820 and over development and over prior experience.

01:02:04.700 And one thing you point out, at least in one of your papers, maybe you did this in the TED Talk,

01:02:08.400 that different contents of consciousness have different characters, so that visual perception

01:02:15.880 is object-based in a way that interior perception is not. The sensing of an experience like nausea,

01:02:23.220 say, or even of an emotion, like sadness, does not have all of the features of perceiving an object

01:02:31.860 in visual space. You're looking at an object in visual space, there's this sense of location,

01:02:38.020 there's the sense that anything that has a front will also have a back, that if you walked around it,

01:02:42.520 you would be given different views of it, none of which may ever repeat exactly.

01:02:47.580 You know, I'm looking at my computer now, yeah, I've probably never seen my computer from precisely

01:02:52.740 this angle, and if I walked around it, I would see, you know, thousands of different slices of this

01:02:58.140 thing in, you know, the movie of my life, and yet there's this unitary sense of an object in space

01:03:04.900 that has a front and back and sides. And of course, none of this applies when we're thinking about

01:03:09.940 our internal experience. Do you have any more you want to say about that? Because that's a very

01:03:15.820 interesting distinction, which, again, is one of these places where the terminology we use for

01:03:21.780 being aware of things, or being conscious of things, or perceiving things, doesn't really get

01:03:26.580 at the phenomenology very well. Now, thank you for raising that. I think this is a great point,

01:03:31.880 and something I've thought quite a lot about. And there's a couple of elements here. So I'll start

01:03:36.920 by talking about this phenomenology of objecthood that you beautifully described for vision there,

01:03:42.460 and then get on to this case of interoception and perception of the internal state of the body.

01:03:48.380 So indeed, for most of us, most of the time, visual experience is characterized by there being a world

01:03:54.540 of objects around us. I see coffee cups on the table, computers in front of me, and so on.

01:03:59.900 Actually, that's not always the case. If I'm, for instance, trying to catch a cricket ball,

01:04:05.420 or a softball, or something someone's thrown to me, what my perceptual system is doing there is not

01:04:10.680 so much trying to figure out what's out there in the world, it's all geared towards the goal of

01:04:16.640 catching the cricket ball. And there's a whole branch of psychology, it has roots in Gibsonian

01:04:23.380 ecological psychology, and William Power's perceptual control theory, that sort of inverts things. And it

01:04:30.400 says that there's this whole tradition in thinking about perception, and its interaction with behavior.

01:04:38.180 I mean, we like to think that we perceive the world, and then we behave. So we have perception

01:04:42.320 and the control of controlling behavior. But we can also think of it the other way around,

01:04:46.860 and think of behavior controlling perception, so that when we catch a cricket ball, what we're really

01:04:54.160 doing is maintaining a perceptual variable to be a constant. In this case, it would be the acceleration

01:05:00.340 of the angle of the ball to the horizon. If we keep that constant, we will catch the cricket

01:05:06.160 ball. And if you reflect on the phenomenology of these things, if I'm engaged in an act like

01:05:11.180 that, I'm not so much perceiving the world as distinct objects arranged in particular

01:05:14.800 ways, I'm perceiving how well my catching the cricket ball is happening. Am I likely to

01:05:21.740 catch it? Is it going well or not? That's a different kind of description of visual phenomenology.

01:05:27.700 But most of them, this will become important a bit later when we talk about why our experience

01:05:31.980 of the inside of our bodies, of being a body, has the character that it has. I think it's

01:05:37.300 more like catching a cricket ball, but we'll get to that in a second. But if we think now

01:05:41.800 just back to when we're not catching things, we're just looking around and we see this visual

01:05:47.440 scene populated by objects. And you're absolutely right that one way to think of that is that

01:05:52.660 when I perceive an object to be, to have a volumetric extension, to be a three-dimensional

01:05:59.980 thing in the world occupying a particular location. What that means is that I'm perceiving how that

01:06:08.200 object would behave if I were to interact with it in different ways. This has another tradition,

01:06:14.660 well, it's back to Gibson again and ecological psychology, but also sensorimotor theory of

01:06:19.840 Alvin Noe and Kevin O'Regan, that what I perceive is how I can interact with an object. I perceive an

01:06:26.500 object as having a back, not because I can see the back, but because my brain is encoding somehow

01:06:32.220 how different actions would reveal that surface, the back of that object. And that's a distinctive

01:06:40.100 kind of phenomenology. In the language of predictive processing of the Bayesian brain, one thing I've

01:06:46.800 been trying to do is cash out that account of the phenomenology of objecthood in terms of the

01:06:53.440 kinds of predictions that might underlie it. And these turn out to be conditional or counterfactual

01:07:00.500 predictions about the sensory consequences of action. So in order to perceive something as having

01:07:07.660 objecthood, the thought is that my brain is encoding how sensory data would change if I were to move around

01:07:15.500 it, if I were to pick it up, and so on and so forth. And if we think about the mechanics that might

01:07:22.360 underlie that, they fall out quite naturally from this Bayesian brain perspective, because

01:07:27.040 to engage in predictive perception, to bring perceptual interpretations to bear on sensory data,

01:07:36.320 our brain needs to encode something like a generative model. It needs to be able to have a model of the

01:07:43.380 mapping from sensory data to, or rather the mapping from something in the world to sensory data, and be

01:07:50.140 able to invert that mapping. That's how you do Bayesian inference in the brain. And if you've got a

01:07:55.760 generative model that can invert that mapping, then that's capable of predicting what sensory signals

01:08:00.960 would happen conditional on different kinds of actions. This is, it brings in an extension of

01:08:08.880 predictive processing that's technically called active inference, where we start to think about reducing

01:08:14.520 prediction errors, not only by updating one's predictions, but also by making actions to sort

01:08:20.560 of make our predictions come true. But in any case, you can make some interesting empirical predictions

01:08:25.480 about how our experience of something as an object depends on what the brain learns about ways of

01:08:34.740 interacting with these objects. And we started to test some of these ideas in the lab, because

01:08:39.420 you can now use clever things like virtual reality and augmented reality to generate objects that will

01:08:47.440 be initially unfamiliar, but that behave in weird ways when you try to interact with them. So you can

01:08:53.440 either support or confound these kinds of conditional expectations, and then try to understand what

01:09:00.620 the phenomenological consequences of doing so are. And you can also account for situations where this

01:09:09.160 phenomenology of objecthood seems to be lacking. So for instance, in synesthesia, which is a very

01:09:15.660 interesting phenomenon in consciousness research, and yeah, I'm sure you know this, Sam, but a very

01:09:23.600 canonical example of synesthesia is when, as graphene color synesthesia, people may look at a black letter or

01:09:30.960 number or graphene, and they will experience a color along with that experience. They will have a color

01:09:38.640 experience, a concurrent color experience. This is very, very well established. What's often not focused

01:09:44.640 on is that pretty much across the board in graphene color synesthesia, synesthetes, they don't make any

01:09:52.440 confusion that the letter is actually red or actually green. They still experience the letter as black, they're

01:09:59.440 just having an additional experience of color along with it. They don't confuse it as a property. So this is why

01:10:05.760 whenever you see a kind of illustration of synesthesia with the letters colored in, it's a very, very poor

01:10:10.240 illustration. I'm guilty of using those kinds of poor illustrations in the past. But this color

01:10:16.760 experience does not have the phenomenology of objecthood. It lacks it. It doesn't appear to be

01:10:22.960 part of an object in the outside world. Why not? Well, it doesn't exhibit the same kinds of sensory

01:10:29.760 motor contingencies that an object that has a particular color does. So if I'm synesthetic

01:10:37.520 and I'm looking at the letter F and I change a lighting condition somewhat or move around it,

01:10:42.720 then a really red F will change its luminance and reflectance properties in subtle but significant

01:10:49.760 ways. But for my synesthetic experience, it's still just an F. So my experience of red doesn't

01:10:57.840 change. So I think this is just a promising example of how concepts and mechanisms from within predictive

01:11:07.600 perception can start to unravel some pervasive and modality-specific phenomenological properties

01:11:16.560 of consciousness. I think it's worth emphasizing the connection between perception and action because

01:11:22.400 it's one thing to talk about it in the context of catching a cricket ball. But when you talk about

01:11:29.280 the evolutionary logic of having developed perceptual capacities in the first place, the link to action

01:11:36.000 becomes quite explicit. We have not evolved to perceive the world as it is for some abstract

01:11:44.000 epistemological reason. We've evolved to perceive what's biologically useful. And what's biologically

01:11:50.160 useful is always connected, at least when you're talking about the outside world, to actions. If you

01:11:58.000 can't move, if you can't act in any way, there would have been very little reason to evolve a capacity for

01:12:03.680 sight, for instance.

01:12:04.880 Absolutely. I mean, there's that beautiful story I think of, is it the sea slug or the sea snail or

01:12:10.560 something of that sort? Some very simple marine creature that swims about during its juvenile

01:12:17.600 phase looking for a place to settle. And once it's settled and it just starts filter feeding,

01:12:24.000 it digests its own brain because it no longer has any need for perceptual competence now that it's not

01:12:30.720 going to move anymore. And this is often used as a slightly unkind analogy for getting tenure in

01:12:36.400 academia. But you're absolutely right that the perception is not about figuring out really what's

01:12:43.600 there. We perceive the world as it's useful for us to do so. And I think this is particularly important

01:12:49.280 when we think about perception of the internal state of the body, which you mentioned earlier,

01:12:55.200 this whole domain of interoception. Because if you think, what are brains for fundamentally?

01:13:04.160 Right? They're not for perceiving the world as it is. They're certainly not for,

01:13:08.080 didn't evolve for doing philosophy or complex language. They evolved to guide action.

01:13:13.920 But even more fundamentally than that, brains evolved to keep themselves and bodies alive.

01:13:21.120 They evolved to engage in homeostatic regulation of the body so that it remains within viable

01:13:32.880 physiological bounds. That's fundamentally what brains are for. They're for helping creatures

01:13:39.760 stay alive. And so the most basic cycle of perception and action doesn't involve the outside world at all.

01:13:48.960 It doesn't involve the exterior surfaces of the body at all. It's only about regulating the internal

01:13:57.280 milieu, the internal physiology of the body, and keeping it within the bounds that are compatible with

01:14:04.160 survival. And I think this gives us a clue here about why experiences of mood and emotion and of,

01:14:13.600 if you like, the most basic essence of selfhood have this non-object-like character.

01:14:22.800 So I think the way to approach this is to first realize that just as we perceive the outside world on

01:14:30.720 the basis of sensory signals that are met with a top-down flow of perceptual expectations and predictions,

01:14:37.200 the very same applies to perception of the internal state of the body. The brain has to know what the

01:14:45.760 internal state of the body is like. It doesn't have any direct access to it just because it's wrapped

01:14:49.600 within a single layer of skin. I mean, the brain is the brain. All it gets are noisy and ambiguous

01:14:55.520 electrical signals. So it still has to interpret and bring to bear predictions and expectations in

01:15:04.080 order to make sense of the barrage of sensory signals coming from inside the body. And this

01:15:08.320 is what's collectively called interoception, perception of the body from within. Just as a

01:15:13.520 side note, it's very important to distinguish this from introspection, which could hardly be more

01:15:18.000 different introspection. Consciously reflecting on the content of our experience, this is not that.

01:15:22.560 This is interoception, perception of the body from within. So the same computational principles

01:15:29.040 apply. We have to bring to bear, our brain has to bring to bear predictions and expectations.

01:15:34.640 So in this view, we can immediately think of emotional conscious experiences, emotional feeling states

01:15:44.640 in this same inferential framework. And I've written about this for a few years now that we can think of

01:15:50.800 interoceptive inference. So emotions become predictions about the causes of interoceptive signals in just

01:15:57.920 the same way that experiences of the outside world are constituted by predictions of the causes of sensory

01:16:02.800 signals. And this, I think, gives a nice computational and mechanistic gloss on pretty old theories of

01:16:12.320 emotion that originate with William James and Carl Langer. That emotion has to do with perception of

01:16:19.120 physiological change in the body. These ideas have been repeatedly elaborated. So people ask about

01:16:26.240 the relationship between cognitive interpretation and perception of physiological change.

01:16:31.920 This predictive processing view just dissolves all those distinctions and says that

01:16:36.320 emotional experience is the joint content of predictions about the causes of interoceptive signals

01:16:43.440 at all levels, at all low and high levels of abstraction. And the other aspect of this that becomes important

01:16:53.120 is the purpose of perceiving the body from within

01:16:57.040 is really not at all to do with figuring out what's there. My brain couldn't care less that

01:17:06.000 my internal organs are objects and they have particular locations within

01:17:11.680 my body. Couldn't care less about that. It's not important. The only thing that's important about

01:17:17.280 my internal physiology is that it works. That if you imagine the inside of my body is a cricket ball,

01:17:25.040 it really don't care where the cricket ball is or that it's a ball. All it cares is that I'm going to

01:17:30.800 catch the ball. It only cares about control and regulation of the internal state of the body.

01:17:36.720 So predictions, perceptual predictions for the interior of the body are of a very different kind.

01:17:43.840 They're instrumental. They're control oriented. They're not epistemic. They're not to do with finding out.

01:17:48.960 And I think that gets it. For me anyway, it's very suggestive of why

01:17:56.240 our experiences of just being a body have this very sort of non-object-based,

01:18:03.520 inchoate, phenomenological character compared to our experiences of the outside world.

01:18:08.880 But it also suggests that everything can be derived from that. That if we understand the original

01:18:14.880 purpose of predictive perception was to control and regulate the internal state of the body,

01:18:22.560 then all the other kinds of perceptual prediction are built upon that evolutionary imperative,

01:18:28.640 so that ultimately the way we perceive the outside world is predicated on these mechanisms that have

01:18:35.600 their fundamental objective in the regulation of our internal bodily state.

01:18:40.400 And I think this is really important for me because it gets away from these pre-theoretical

01:18:49.600 associations of consciousness and perception with cognition, with language, with all these higher

01:18:53.840 order things, maybe social interaction, and it grounds them much more in the basic mechanisms of life.

01:19:01.760 So here we have a nice thing that it might not just be that life provides a nice analogy

01:19:07.280 with consciousness in terms of hard problems and mysteries and so on, but that there are actually

01:19:12.320 very deep obligate connections between mechanisms of life and the way we perceive consciously and

01:19:17.920 unconsciously ourselves and the world.

01:19:19.840 Well, so now if interoception is purpose toward what is sometimes called allostatic control,

01:19:27.760 so the regulation of internal states on the basis of essentially homeostasis as governed by behavior and

01:19:35.360 action. If that's the purpose and emotion is essentially parasitic on these processes,

01:19:43.360 an emotion like disgust, say, or fear or anger, much of the same neural machinery is giving rise to

01:19:51.440 these kinds of emotions. How do you think about emotion by this logic? What precipitates an emotion is

01:20:00.160 most often, I mean, it can just be a thought, right, or a memory of something that's happened,

01:20:04.320 but its referent is usually out in the world, very likely in some social circumstance. What is the

01:20:10.960 logic of emotion in terms of this picture of prediction and control in, you know, our internal

01:20:19.440 system? It's very interesting. I think it's more of a research program than a question that's easy to

01:20:23.760 answer in the here and now, but I think the idea would be that emotions, emotional content of any

01:20:32.880 sort is ultimately marking out in our conscious experience the allostatic relevance of something

01:20:43.280 in the world, an object or a social situation or a course of action, so that our brain needs to be

01:20:51.360 able to predict the allostatic consequences. And here, you're absolutely right, allostasis is sort

01:20:56.720 of the behavioral process of maintaining of homeostasis. So our brain needs to be able to

01:21:03.520 predict the allostatic consequences of everything that it, every action that the body produces,

01:21:11.520 whether it's an internal action of autonomic regulation, whether it's an external

01:21:16.400 action, a speech act or just a behavioral act. What's that? What are the consequences of that for

01:21:22.480 our physiological condition and the maintenance of viability? And I think emotional content is a way

01:21:30.480 in which those consequences become represented in conscious experience. And they can be quite simple.

01:21:37.840 So if you think of, you know, probably primordial emotions like disgust have to do with a rejection

01:21:43.920 of something that you try to put inside your body that shouldn't be there, because the consequence

01:21:47.440 is going to be pretty bad. And that's a very non-social kind of emotion, at least

01:21:53.280 certain forms of disgust that have to do with eating bad things don't depend so much on social

01:21:59.520 context, though they can be invoked by social context later on. But then other more sophisticated or

01:22:06.560 more ramified emotions like regret, think about regret. It's not the same as disappointment.

01:22:15.920 And disappointment is, I was expecting X and I got Y, you know, like a lot of people might have done

01:22:21.680 Christmas last week. You can be disappointed, but regret has an essential counterfactual element that,

01:22:28.000 oh, I could have done this instead. And then I would have got X if I'd done this. And I think

01:22:37.680 certainly my own personal emotional life involves many experiences of regret, and even anticipatory

01:22:43.680 regret, where I regret things I haven't even done yet because I kind of assume they're going to turn out

01:22:47.920 badly. And the relevance of that is that these sorts of emotional experiences depend on quite

01:22:55.120 high-level predictions about counterfactual situations, about social consequences, about

01:23:01.920 what other people might think or believe about me. So we can have an ordering of the richness of

01:23:08.000 emotional experience, I think, that is defined by the kinds of predictions that are brought to bear.

01:23:13.360 But they're all ultimately rooted in their relevance for physiological viability.

01:23:19.600 Well, so we've been talking about the contents of consciousness and how varied they are and

01:23:25.120 how they're shaped by top-down predictive processes, perhaps even more than bottom-up processes.

01:23:34.240 But what do you think about the experience of, it's often described as being of pure consciousness,

01:23:41.760 consciousness without content or without obvious content? Is this something that you are

01:23:46.640 skeptical exists, or do you have a place on the shelf for it?

01:23:52.560 I think it probably does exist. I don't know. I mean, unlike you, I've not been a very disciplined

01:24:00.720 meditator. I've tried it a little bit, but it's not something that you probably gain very much from

01:24:06.960 dabbling in. I think it seems to me conceivable that there's a phenomenal state which is characterized

01:24:16.480 by the absence of specific contents. Now, I can imagine I'm happy with the idea that that state

01:24:23.120 exists. I'm somehow skeptical of people's reports of these states. And this gets back to what we were

01:24:30.080 talking about earlier, that we tend to somehow overestimate our ability to have insight into

01:24:38.880 our phenomenal content at any particular time. But yeah, I mean, the interesting question there,

01:24:44.320 which I haven't thought about a lot, is what would the computational vehicles of such a state be in

01:24:49.440 terms of predictive perception? Is it the absence of predictions or is it the prediction of that nothing

01:24:55.520 is causing my sensory input at that particular time? I don't know. I don't know. I have to think

01:25:01.600 about that some more. Yeah, I mean, it's an experience that I believe I've had. And again,

01:25:06.720 I agree with you that we're not subjectively incorrigible, which is to say we can be wrong about

01:25:12.480 how things seem to us. We can certainly be wrong about what's actually going on to explain the

01:25:19.120 character of our experience. But I would say we can be wrong about the character of our experience

01:25:23.280 in important ways. Just to say that if we become more sensitive to what an experience is like,

01:25:29.360 we can notice things that we weren't first noticing about it. And it's not always a matter

01:25:34.480 of actually changing the experience. Obviously, there's conceptual questions here about whether or

01:25:39.120 not being able to discriminate more is actually finding qualia that were there all the time that you

01:25:45.840 weren't noticing, or you're actually just changing the experience. When you learn how to taste wine,

01:25:51.280 are you having a fundamentally different experience? Or are you actually noticing things that you

01:25:56.480 might have noticed before? Or are both processes operating simultaneously? I think it's probably

01:26:01.760 both. Yeah, I mean, I think this whole predictive perception view would come down pretty firmly that

01:26:07.200 at least to some extent, your experience is actually changing because you're developing a

01:26:11.040 different set of predictions. Your predictions are better able to distinguish

01:26:15.760 initially similar sets of sensory signals. So I think, yeah, it's not just that you're noticing

01:26:20.400 different things. Your experiences are changing as well.

01:26:23.360 I mean, to take the experience of pure consciousness that many meditators believe they've had,

01:26:29.120 people have had it on psychedelics as well, and perhaps we'll touch the topic of psychedelics,

01:26:34.560 because I know you've done some research there. But the question is, what I'm calling pure consciousness,

01:26:40.160 was there something there that I could have noticed that was the contents of consciousness that I wasn't

01:26:45.760 noticing there? But the importance of the experience doesn't so much hinge for me on whether or not

01:26:52.960 consciousness is really pure there or really without any contents. It's more that it's clearly

01:27:00.720 without any of the usual gross contents. It's quite possible to have an experience where you're no longer

01:27:08.640 obviously feeling your body. There's no sensation that you are noticing. There's no sense of, you know,

01:27:15.840 proprioception. There's no sense of being located in space. In fact, the experience you're having

01:27:21.280 is a consciousness denuded of those usual reference points, and that's what's so interesting about it.

01:27:27.920 That's what's so expansive about it. That's why it suddenly seems so unusual to be you in that moment,

01:27:34.000 because all of the normal experiences have dropped away. So seeing, hearing, smelling,

01:27:39.760 tasting, touching, and even thinking have dropped away. This is where, for me, the hard problem does

01:27:46.160 kind of come screaming back into the conversation. On many of these accounts of what consciousness is,

01:27:51.600 we should probably move to Tononi's notion of integrated information. On his account,

01:27:57.040 and this is a very celebrated thesis in neuroscience and philosophy, on his account, consciousness

01:28:03.840 simply is a matter of integrated information. And the more information and the more integrated,

01:28:10.560 the more consciousness, presumably. But an experience of the sort that I'm describing of

01:28:17.120 pure consciousness, consciousness, you know, whether pure or not, consciousness stripped of its usual

01:28:22.560 informational reference points is not the experience of diminished consciousness. In fact, the people who

01:28:30.560 have this experience tend to celebrate it as more the quintessence of being conscious. I mean,

01:28:36.720 it's really some kind of height of consciousness as opposed to its loss. And yet, the information component

01:28:45.840 is certainly dialed down by any normal sense in which we use the term information. They're not

01:28:53.200 things being discriminated from one another. And I guess you could say it's integrated, but there are

01:28:58.720 other experiences that I could describe to you where the criteria of integration also seems to fall apart,

01:29:04.240 and yet consciousness remains. So again, this is one of those definitional problems. But if we're going to

01:29:10.480 call consciousness a matter of integrated information, if we find an example of there's something that it's

01:29:17.520 like to be you, and yet information and integration are not its hallmarks, well then it's kind of like

01:29:25.360 defining all ravens as being black and then we find a white one. What do we call it? A white raven or

01:29:31.200 some other bird. Do you have any intuitions on this front?

01:29:35.440 There's an awful lot in what you said just there. I think if we just put aside for a second

01:29:43.280 trying to isolate what we might call the minimal experience of selfhood. Is there anything left

01:29:50.000 after you've got rid of experiences of body and of volition and of internal narratives and so on and so

01:29:56.240 on? Have a thought about that. Just for one point of clarification, I would distinguish this from

01:30:01.920 the loss of self, which I hope we come to. I think you can lose your sense of self with all of the

01:30:08.800 normal phenomenology preserved. So you can be seen and hearing and tasting and even thinking just as

01:30:15.680 vividly, and yet the sense of self, or at least one sense of self, can drop away completely. This is

01:30:22.880 a different experience I'm talking about.

01:30:24.480 Yes, I mean that sounds like flow state type experiences in some way. But maybe we can get onto that

01:30:31.200 but if we move indeed to IIIT and think about how that might speak to these issues of pure

01:30:40.160 consciousness and whether these experiences serve as some kind of counter example, some

01:30:45.920 phenomenological counter example to IIIT. I think that's very interesting to think about. And it gets

01:30:51.920 that whether we consider IIT integrated information theory to be primarily a theory of conscious level,

01:31:00.480 of how conscious a system is, or of conscious content, or of their interaction. Perhaps it's

01:31:06.880 best to start just by summarizing in a couple of sentences the claims of IIT, because you're absolutely

01:31:13.200 right. It's become, it's come to occupy a very interesting position in the academic landscape of

01:31:19.200 consciousness research. A lot of people talk about it, although in the last couple of meetings of the

01:31:26.080 Association for the Scientific Study of Consciousness, certainly the last one, there was surprisingly

01:31:30.480 little about it. And I have a thought why that might be, which we can come on to. It's probably

01:31:36.320 worth trying to explain just very briefly what integrated information theory IIT tries to do. And what it

01:31:45.040 tries to do, it starts with a bunch of phenomenological axioms. So it doesn't start by asking the question,

01:31:51.920 what's in the brain and how does that go along with consciousness? It tries to identify

01:31:57.360 axiomatic features of conscious experience, things that should be self-evident, and then try to,

01:32:04.000 from there, derive what are the necessary and sufficient

01:32:08.880 mechanisms, or really what's a sufficient mechanistic basis given these axioms. IIT will call these

01:32:15.280 postulates. There are actually, in the current version of IIT, five of these axioms. But I think

01:32:21.840 we just consider a couple of them, and these are the fundamental ones, information and integration.

01:32:26.400 And these particular, you can call them axioms, or you can call them just generalizations of what

01:32:35.120 all conscious experiences seem to have in common. Information integration. So the

01:32:41.440 axiom of information is that every conscious experience is highly informative for the organism,

01:32:48.320 in the specific sense of ruling out a vast repertoire of alternative experiences. You're having

01:32:55.040 this experience right now, instead of all the other experiences you could have, you could have had,

01:33:01.360 you have had, you will have, you're having this particular experience. And the occurrence of that

01:33:06.720 experience is generating an enormous amount of information because it's ruling out so many

01:33:11.920 alternatives. As you go through this, I think it will be useful for me to just flag a few points where

01:33:18.640 this phenomenologically breaks down for me. So again, the reference here is to kind of non-ordinary

01:33:24.640 experiences in meditation and with psychedelics. But the meditative experiences for me, at least,

01:33:31.200 have become quite ordinary. I can really talk about them in real time. So the uniqueness of each

01:33:38.160 conscious experience as being highly informative because it rules out so many other conscious

01:33:45.040 experiences. In meditation, in many respects, that begins to break down because what you're noticing

01:33:53.920 is a core of sameness to every experience. What you're focusing on is the qualitative character of

01:34:01.920 consciousness that is unchanged by experience. And so the distinctness of an experience isn't what is so

01:34:11.040 salient. What is salient is the unchanging quality of consciousness in its openness, its centerlessness,

01:34:19.360 its vividness. And one analogy I've used here, and if you've ever been in a restaurant which has had a

01:34:25.760 full-length mirror across one of the walls and you haven't noticed that the mirror was a mirror and you

01:34:31.200 just assume that the restaurant was twice as big as it in fact is, the moment you notice it's a mirror,

01:34:37.440 you notice that everything you thought was the world is just a pane of glass. It's just a play

01:34:43.200 of light on a wall. And so all those people aren't really people or they're not extra people. They're

01:34:48.560 in the room just being reflected over there. And one way to describe that shift is almost

01:34:53.680 a kind of loss of information, right? It's just like there's no depth to what's happening in the

01:34:58.240 glass. Nothing's really happening in the glass. And meditation does begin to converge on that kind of

01:35:05.840 experience with everything. The Tibetan Buddhists talk about one taste, being that there's basically,

01:35:11.600 there's a single taste to everything when you really pay attention. And it is because these

01:35:17.600 intrinsic properties of consciousness are what have become salient, not the differences between

01:35:22.480 experiences. So I don't know if that just sounds like an explosion of gibberish to you, but it's a way

01:35:28.320 in which when I begin to hear this first criterion of Tononi's stated as you have, it begins to not map

01:35:36.880 on to what I'm describing as some of the clearest moments of consciousness. Again, not a diminishment of

01:35:44.320 consciousness. That's very interesting. And those states of being aware of the unchanging nature of

01:35:53.600 consciousness, I think that that's really very important. I'm not sure it's misaligned with

01:36:02.640 Tononi's intuition here, because I think the idea of informativeness is, so if you think about it,

01:36:08.160 I mean, there's one way to think about it, which is that specific experience that you're having in

01:36:12.240 that meditative state of becoming aware of one taste or of the unchanging nature that underlies all

01:36:20.000 experiences. That itself is a specific experience. It's a very specific experience. You have to have

01:36:25.760 trained in meditation for a long time to have that experience. And the having of that experience

01:36:32.560 is equally distinctive. It's ruling out all the other experiences when you're not having that

01:36:36.960 experience. So it's not so much how informative it is for you at the psychological level.

01:36:43.920 It's a much more reductionist interpretation of information. I think the other way to get at that

01:36:52.000 is to think of it from the bottom up, from the simple systems upwards, and Tononi uses an analogy,

01:36:58.320 which I think has got some value. Why is a photodiode not conscious? Well, for a photodiode,

01:37:04.000 the whole world, in the world, outer world, it's either dark or light. The photodiode doesn't have

01:37:10.080 an experience of darkness and lightness. It's just, you know, on or off, one or zero.

01:37:16.000 And generalizing that, that a particular state has the informational content it has

01:37:24.400 in virtue of all the things it isn't, rather than the specific thing that it is. So we can think

01:37:30.400 about this in terms of color. You know, red is red, not because of any intrinsic redness

01:37:36.400 to a combination of wavelengths, but because of all the other combinations of wavelengths

01:37:42.320 that are excluded by that particular combination of wavelengths. And I think this is really interesting.

01:37:48.800 This point actually precedes integrated information theory, goes right back to the

01:37:54.080 dynamic core ideas of Tononi and Edelman, which was the thing that first attracted me to go and work

01:37:59.600 in San Diego, nearly 20 years ago. And even then, the point was made that an experience of pure darkness,

01:38:07.280 or, you know, complete sensory deprivation, where there's no sensory input, no perceptual content,

01:38:13.600 call this a hypothetical conscious state for now. I don't know how, to what extent, you know,

01:38:18.320 it's approximated by any meditative states. That has exactly the same informational content,

01:38:24.640 as does a very vivid, busy, conscious scene walking down the high street, because it's ruling out

01:38:31.280 the same number of alternatives. And it may seem subjectively different, less informative,

01:38:37.360 because there's nothing going on. But in terms of the number of alternative states

01:38:42.960 that it's ruling out, it's the same. So I think there's a sense in which we can interpret

01:38:48.480 information, this axiom of informativeness, as applying to a whole range of different kinds of

01:38:59.440 conscious contents. Of course, this does get us onto tricky territory about whether we're talking

01:39:04.720 about a theory of level, or a theory of content. But this idea is, yeah, I think it can account for

01:39:13.120 your situation, though it does ask the question about, can we really get it at content specifically

01:39:19.360 there? So the number of states over which you can range as a conscious mind defines how much

01:39:26.640 information is encoded when you're in one of those states? That's right. That would be the claim. And

01:39:33.520 you know, you can think of it in terms of, so one of the quantities associated with this technical

01:39:40.480 definition of information theory is entropy. And entropy simply measures the range of possible

01:39:47.920 options and the likelihood of being in any particular one of those options. And so information,

01:39:55.760 so entropy is a measure of the kind of uncertainty associated with a system state. And so, you know,

01:40:03.920 a photodiode can only be in one of two possible states. A single die can be in six possible states,

01:40:10.320 a combination of two die can be in 12 possible states. And there's actually, I want to linger here

01:40:18.480 slightly longer because it's in these technical details about information theory that IIT, I think,

01:40:27.520 runs aground because it's trying to address the hard problem. It's because of this identity relationship

01:40:35.280 that Tononi argues for between integrated information. We'll get onto integration in a second,

01:40:40.640 but let's just think about information. It's because of this identity relationship in which he says

01:40:46.640 consciousness simply is integrated information measured the right way. That the whole theory becomes

01:40:54.560 empirically untestable and lame. Because if we're to make the claim that the content and level of

01:41:05.280 consciousness that a system has is identical to the amount of integrated information that it has,

01:41:12.480 that means in order to assess this, I need to know not only what state the system is in and what state

01:41:21.280 it was in previous time steps, let's say we measure it over time, but I also need to know

01:41:29.120 all the states the system could be in, but hasn't been in. I need to know all its possible combinations.

01:41:36.480 And that's just impossible for anything other than really simple toy systems. There's a metaphysical

01:41:42.880 claim which goes along with this too, which is that information has ontological status.

01:41:48.000 This goes back to John Wheeler and It From Bit and so on, that the fact that a system could occupy a

01:41:56.400 certain state but hasn't is still causally contributing to the conscious level and state of the system

01:42:05.440 now. And that's a very strong claim, and it's a very interesting claim. I mean, who knows

01:42:11.200 what the ontological status of information in the universe will turn out to be.

01:42:15.680 But you also have an added problem of how you bound this possibility. So for instance,

01:42:22.320 so not only can you not know all the possible states my conscious mind could be in so as to

01:42:29.600 determine the information density of the current state, but what counts as possible? If, in fact,

01:42:37.600 it is possible to augment my brain even now, I just don't happen to know how to do that,

01:42:42.960 but it's possible to do that, or it'll be possible next week. Do we have to incorporate those

01:42:47.840 possibilities into the definition of my consciousness? If you'd like to continue

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Making Sense - Sam Harris - January 09, 2018

#113 — Consciousness and the Self

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