Is Reality Just A Hallucination In The Brain? - Anil Seth

most of us at one point or another in our lives have wondered who am I really why am I me and not someone else where was I before I was born what will happen after I die am I the same person from one year to the next these are very personal questions when we take the self to be not the thing that does the perceiving but an aspect of this flow of conscious experience that requires explanation itself then I think we're making progress what is the real problem of consciousness I think it's it's this approach to understanding Consciousness that I'm taking and I think a lot of my colleagues also are whether they know it or not the real problem is in contrast to the so-called hard problem the hard problem of Consciousness is this problem which seems very hard of trying to figure out how in the world something like conscious experience felt experience the redness of red the sharpness of pain now that is generated by or is identical to stuff happening in the world of stuff Mata biological stuff we're made of stuff it's complicated stuff but it's still stuff how does that give rise to conscious experience that's the hard problem now we can try and solve it head on but no one's managed to do that yet the real problem of Consciousness is the is it's just saying that Consciousness exists some philosophers even would have us doubt that Consciousness exists we all know what it's like to have experiences of the world itself and they're related in Intimate ways to the brain and the body so can we try to explain properties of Consciousness like what experiences feel like why are visual experience is different from an emotion can we explain properties of Consciousness in terms of the brain and the body and I think if we do that that's addressing the the real problem and whether we eventually completely solve the hard problem or not is still up for grabs but let's see how far we get and my suspicion and and belief really is that by making progress on this real problem then the hard problem with eventually fade away and just dissolve in a puff of philosophical smoke what would an explanation of the real problem of Consciousness look like I'm trying to work out what sort of form that could actually take it's could take many forms and there are there are many different forms they all kind of move us away from what the Neuroscience of Consciousness started like which was Finding correlations between things happening in our experience and things happening in the brain for example a correlation could be your part of your brain maybe your frontal cortex lights up when you consciously see something but doesn't when you don't that's a correlation it's useful to know but it's not the whole story it's not we it doesn't give us a sense of satisfaction and we all know intuitively and in other areas that correlations are not the same thing as explanations or causations like I think there's there's things like the historical price of cheese in Wisconsin correlates with a divorce rate in France I think which is a fun fact but it doesn't mean anything have you seen the correlation between I think it's the number of movies that Nick Cage was in in that particular year and the number of people who drown in their own swimming pool well maybe there is a causal link there I mean that seems potentially okay to the road swimming pool to escape the new Nick Cage movie it's yeah I mean it seems unlikely but you never know but no this is the point that correlations we can always find correlations and the the goal is to move from things that merely correlate to things that have explanatory and predictive value so that we can say okay oh yeah that makes sense why that kind of pattern of brain activity goes along with that kind of conscious experience and to make that link that to go from it just does to oh it makes sense that it does we need theories we need theories that try to explain um why conscious experiences have the character that that they do and there are a number of theories on offer the one I prefer and the one I work with mainly is the idea that the brain is a kind of prediction machine and that different kinds of conscious experience are different kinds of brain based prediction and that gives it a language for connecting these two different levels why is being ourselves and having a sense of self related to a discussion of Consciousness how did those two things get related do we know what it's like to have this phenomenological experience of being yourself we talk about it the book is called being you like it's it's what's that got to do with Consciousness why is the self-rooted in Consciousness and how do they relate I think it's Central and I think this is actually one of the side benefits if you or maybe it's even the main benefit of the real problem of Consciousness approach because even if we don't solve the whole mystery it changes the way we think about the problem and in science and philosophy often when you change the way you think about the problem you change the questions that's also progress and so when it comes to the self we might think that the problem of Consciousness is really the problem of how we experience the world around us there's a world around us it has objects in it has people in it and we experience them as moving around having different visual appearances and so on but I think for many of us there is a sense of mystery about what the self is and we might take it for granted and just think well there's this essence of me you might want to call it a soul or a spirit or something there's this essence of me that is inside my skull that is just there and it's the thing that does the perceiving and it's making the decisions about what my organism body does and that's all there is to it I mean that's separate from the problem I think it's the central part of the problem Consciousness for each of us consistent experiences of the world but also experiences of the self of being the individual that we are and if I think back in in talking to a lot of people actually that's where the relevance of Consciousness research often becomes most clear so I think most of us at one point or another in our lives have wondered who am I really why am I me and not someone else where was I before I was born what will happen after I die am I the same person from one year to the next these are very personal questions and so when we take the self to be not the thing that does the perceiving but an aspect of this flow of conscious experience that requires explanation itself then I think we're making progress yeah I think when we're talking about Consciousness the for the non-neuroscientists amongst us it's the most front and center part of it right everybody understands what it's like to have a felt sense of existing I know what it's like they go through these things I mean they know what it's like almost to the extent that you don't even think about it because your yourself is kind of always there you know your conscious perceptions of the world change as you move around and you might have different emotions of course and your experience of self does change but it's it's with you because it is you so that might make it easy to overlook when you think about the problem what is the cell is it a a perception that we have of the the thing that inhabits all of the different experiences we go through like what does it mean to say that we are the same person now as we were 20 years ago that's a very complicated question because I think it makes sense in some ways but not in other ways and the reason for that is that what it is to be yourself is not one thing and the self is not a thing it's a process it's a unfolding process that encompasses different kinds of perceptual experience one way to think of the nature of the self for adult human being is to break it down into different levels so at the lowest level as you said a minute ago there's this basic almost unquestionable experience of just being a living organism of merely existing on top of that we have emotions and moods these are key parts of what it is to be yourself now an emotion is not a perception of something out there in the world it feels within it feels Part of Me Part of us and then there's an experience of the body as an object again very easy to take for granted but when you think about it we experience our bodies as separate from the rest of the world and there are many conditions where this isn't the case people with Phantom limbs people with other kinds of conditions where their brains create other experiences about what is or what is not the body and then built on top of that you have experiences of perceiving the world from a first-person perspective that's part of the self experiences of agency and and the and what we would call free will which is not what most people think it is but it's still part of the self in terms of the experience of Free Will and only then do you get to the the level of personal identity the level of the self where you'd associate a name a set of memories of the past and plans for the future and a social network a social influence on Who We Are so they're all these different dimensions of Salford that are bound together for most of us most of the time in a seamless whole but we know from lab experiments from neurology from Psychiatry that they can and do come apart so the self is is complex it doesn't have to be the way it is and when we ask am I the same person I was 20 years ago or will be in 20 years time in some ways yes some of these aspects of self might be quite similar but Others May well change and we won't notice the change necessarily unless we have a sudden illness or something like that then we'll notice because it's very abrupt but most of the time the self changes slowly and smoothly and continuously and so we are the same person but what that person is is itself changing yeah there's a sort of strange ship of Theseus thing going on I think every cell in your body has changed is it seven years something like that I remember hearing uh it was a piece of breakup advice for girls uh that said no matter how bad it hurts don't worry because in seven years time there won't even be a cell left in your body that was around when you're in a relationship with your ex which I always thought was kind of a funny way of thinking about it but even with that right so that there is there is a person that is you and there are cells that made up you but you are more than just the cells because the cells can be replaced and yet your sense of self continues that's exactly right and I think it would be it's kind of strange to locate the self in a particular cell or collection of cells but it's equally strange to not do that right because then what is going on then where is it it's in the organization and in the process and this this happens in other things as well right I mean you have maybe a wetter system and all the different molecules of water probably change over time as well and yet the storm system continues to have a coherent identity of itself and the same thing I think is is here it's it's another version of the the ship of Theseus argument by the way that's that's the old kind of Greek story isn't it where you have a ship and you basically replace every part of the ship with a new piece of wood here a new piece of wood there a new rope here and when you've replaced every single part of it the question is is it still the same or triggers broom if you're British and grew up in the 90s no you're shaming me now I grew up in well maybe I'm too old Only Fools and Horses you watched Only Fools and Horses surely with my tiny Fools and Horses yeah come on oh should we get sorry yeah yeah I'm with you triggers broom the famous example for the Americans listening there's this guy who's kind of an idiot that was a friend of all of the other people on this comedy show and he said that he was given an award by the local Council for having used the same broom for eight years and he couldn't believe it and they said hey Amanda with the same broom for eight years it's amazing he said yeah it's only had four new handles and three new heads and everybody looked at him so yeah triggers broom is the British ship of Theseus and that's why British comedy is so good because it's a philosophy lesson as well as comedy yeah um so yeah you know this this same sense of self yeah is it is it the cells is it the fact that you can just replace this is it the organization of the cells but even if it is does that mean that if I was able to recreate that organization elsewhere that that other me would be me well it's no is it okay so is it the fact that I as me inhabited this particular location these particular coordinates and have these particular experiences that I related to with all of my other experiences contiguously over time well maybe but what about if you're unconscious what about if you're going to general anesthetic what about when you're asleep right so they're they're all kinds of weird thought experiments one can play about the self and things that one can do in practice like like anesthesia you know on the first one if you recreate all the parts somewhere else that then what happens there's a very famous philosophical thought experiment which I do talk about a bit in the book called the Teddy Transportation sort of experiment and this is the idea that uh you know a future or maybe even present Elon Musk in his next business venture develops this trans tele transportation system where you go in it scans you at whatever level of detail you think is relevant now maybe the neurons maybe every single molecule maybe every every single atom or quark and it recreates an identical and materially identical version of you somewhere else let's say on Mars and the question is okay so this happens what happens to you subjectively I mean you're you're in let's say I don't know where it is London you get in the device and then you are rebuilt in Mars but at the same time that you're rebuilt in Mars you are destroyed in London like a whole bunch of lasers come and evaporate you because we don't want an ex continual explosion of people that has to work that way so you going into this transportation system should probably just experience yourself one instant you're in London the next instant you're in Mars or on Mars and then one day there's a mistake the system goes wrong and the automatic lasers which would have evaporated the London you don't work and you're still there in London and a technician comes in holding a gun and says I'm sorry we've got to do it the old style way um but the lasers didn't work and then suddenly you have this but hold on a minute I'm still here so what is going on the the Temptation is to think you're either in London or on Mars but really you're probably in both places and this this highlights another assumption that we might make which is another pop culture reference like Highlander that there can be only one the idea of the self that is is indivisible and unique and I think this is probably wrong if you do have exactly the same material thing down to whatever level of organization then you're gonna have the same conscious experiences so in this case initially there would be exactly two of you one on Mars One in London but let's assume they didn't pull the trigger and you leave the the system and you go wandering around of course from that moment on what it is to be each one of you changes and you start to become different people probably much like identical twins start off very much alike and then even though they're surprisingly similar over the lifetime they still diverge because they've had different experiences their brains change their cells change well I don't think that even interestingly in that thought experiment no one would think that the version of them that was scanned and the version of them that appeared in Mars even if they managed to delete the old one and create the new one at the same time I don't think anybody listening would expect for their felt sense to now be on Mars I don't think that anybody would believe that they their experience would can be one contiguous stream and then they would appear in Mars I think it would be because then if that happened and they didn't could it you would be split what would happen you'd be experiencing two lives at once like two eyeballs facing in opposite directions I don't think that that's true either I don't know that would be a question you'd have to there's a branch of philosophy called experimental philosophy where instead of making assumptions about what people would think in these cases we you know you tell them and then you ask them so what do you think would happen I don't know I mean I I think that if you describe it sort of properly then I think it wouldn't be it's a bit like the other example that you use when you go to sleep or go under anesthesia when you go under anesthesia you lose Consciousness entirely and you'll move from one room to another you usually wake up in a recovery room which is different from where the anesthetic was administered and most people expect to be the same person on the other side of that right and they're not going from London to Mars but they're going from one part of the hospital to another yeah yeah so what's the difference in that situation yeah yeah yeah yeah yeah why aren't you waking up as a different person why when you wake up in the morning do you expect to behave the same way as you did previously yeah because I think the brain has a very strong prior expectation that we are the same person and part of that is Justified because not all of the molecules change overnight and a lot of the you know the processes that shape our conscious experience and maintain an Integrity maintain an identity like the storm system maintains its identity over time as well but we're not exactly the same people before or after sleep or before or after anesthesia and I think that's fine and I think recognizing and reconciling ourselves to the ever-changing self is is actually both scientifically and philosophically accurate but also quite helpful and of course echoes a lot of what people have been saying in in things like Buddhist literature and meditative practice forever that there's an impermanence to things and there's an impermanence to the self and to Identity and we should not try and fight against that impermanence will you say that it might be comforting it may have also spiraled somebody into this sort of recursive self uh skeptical thought Loop uh that means they're now not going to be able to leave bad for a little while so I apologize if that's happened so moving on to how we and our Consciousness relates with reality you say that our experience of reality is that of a controlled hallucination what do you mean by that no metaphor is perfect but what I mean by this is that our experiences of the world and of the self too but let's stay with the world for now are not direct reflections of some objective reality like as if the world was just there and it poured itself directly into our minds through our eyes and our ears it might seem like that and we open our eyes in the morning or after anesthesia and it just seems as though the world is there and it has all these properties like color and shape and size and sound and our brains don't seem to have much to do with it but our brains have everything to do with it and the idea and it's not a new idea is that instead of our perceptual conscious experience of the world being a process of reading the world out in this kind of outside in Direction it's a process of active interpretation in which the brain is always trying to make its best guess about what's out there in the world on the basis of sensory information that comes in through the senses but is ambiguous and noisy and it doesn't have labels on like it doesn't have a label saying I'm from a red thing or I'm from a car it's just electrical activity and the brain has to make sense of it and the theory the idea is that it does so by basically having an internal model of the most likely causes of the sensory signals that it gets and what we experience is not a readout of the sensory signal but the brain's predictions about what causes those signals and this is a pretty big flip in how we relate to our experiences because even though it seems they come from the outside in they're actually I think coming from the inside out and the sensory signals are there to keep our brains predictions our brains best guesses tied to reality in ways that are useful for our Behavior as a complex organism that's where the metaphor of controlled hallucination comes from hallucination because experiences are internally generated when we think about hallucinations in everyday language we typically think about something that's generated internally rather than something that's registering the outside world but critically the control is just as important in normal everyday perception uh perceptual experiences don't just wander off into whatever they might be they they're very carefully regulated controlled by the world and the body and that's why perception of course works that's why Evolution has developed it that way so that it's useful for us yeah talk to me about how an evolutionary or a sort of an ancestrally Adaptive lens plays a role here why is it that we would have evolved this particular type of ability why is it that we would be making these predictions what what advantage does it give us and how does that work I think it makes things a lot easier for complex organisms it has to maybe especially so for complex creatures like us um if there were a one-to-one correspondence between some sort of sensory information and something in the world and what we should do about it then we might not need any complex business of making predictions inside our brains but things aren't like that way back in philosophy Emanuel Kant pointed out or made the argument that we can never perceive the world as it really is we only perceive an interpretation as a I guess a transformation of it through a sensory Veil and sensory information that we get is not reliable it's noisy it's uncertain it might come from different things it changes according to the context according to the environment according to lighting conditions and so to get a reliable indication of what's going on in the world it's not enough simply just to funnel sensory information into the brain it has to be interpreted and mathematically there's a there's a way in which one might do this like optimally completely perfectly but this turns out to not really be possible for things to do in practice so this whole process by which the brain makes a prediction of what's out there and then uses sensory information to update these predictions that turns out to be a very very good approximation for how any kind of system would solve this problem of figuring out what's there under conditions of uncertainty why not just absorb what's there I don't know if I'm being thick here but why why not just observe it the way that it is why do this other thing well take color for example take our experiences of color now when we experience color this is a useful thing for for brains to provide our experience with right because colors allow us to keep track of surfaces when lighting conditions change they highlight things we might miss like the color of a ripe fruit in a tree very very useful but where are colors in the world colors don't exist out there in objective reality anyway there's just electromagnetic radiation that goes from radio waves to gamma waves and our eyes are only sensitive to three wavelengths of that radiation and out of those three wavelengths we experience millions of colors so when we experience color we're experiencing simultaneously less than what's there because it's just three wavelengths out of a long vast spectrum and more than because we experience of millions of colors not just three so in this case it wouldn't really be very useful to for us to experience what's really there because what would that mean would it mean that we experienced a continuous kind of set of wavelengths from kilometer long to whatever x-ray however long those are it's not even clear what that would mean to experience that and yet we don't even experience a small subset of that we create the brain create something out of the sensory environment that is very useful for us but you can put it even more simply like what's really out there is it objects or is it atoms or is it quantum foam or something nobody really knows what's out there anyway so to put as a benchmark experiencing things as they really are is I think just to misunderstand what kind of business a brain is in just it's in the business of helping us stay alive this doesn't feel is it Donald Hoffman is that the guy that's got the kind of ideas that the world is very different out there this doesn't feel a million miles away from what he talks about it is similar in some ways so yeah Don Hoffman has his idea of an interface theory of perception which is that what we experience is some kind of user interface which in which intervenes between how the world really is and something that's useful for us to to survive by we agree in the sense that the contents of experience are indirectly related to what's going on out there in the world but there are two places where we disagree one is this metaphor of a user interface I think is problematic because it suggests that there's some kind of Mini-Me inside my head you know looking at this interface as much as I might look at a computer screen and clicking on this icon or that icon whereas back to the self I think the self is part of the interface there is no me that's separate from the flow of experience and I think things that that bring back that smuggle back in this inner homunculus uh is not the way to go and then we also disagree and this is something that I've talked to a few times about he then also makes a whole bunch of claims about the real nature of what's out there in terms of little conscious agents everywhere and and I've not yet been persuaded by his ideas on that they might be in the future but I haven't been yet and you don't have to go that far you can still just try to understand the nature of perception as solving this indirect thickness between how things are in the world and what's the best way for the brain to make sense of things in order to survive I remember reading uh an explanation for an Adaptive uh justification for Consciousness and included in that was the fact that as complex social beings who have to manage our own uh interpretation our own status who have to be able to model that of other people and how that other person is interacting with that other person and so on and so on and so on and so on how important do you think the complex social networks of ancestral humans has been to encouraging this predictive sense that Consciousness sort of has I think it's important but I think it's important can be and sometimes has been taken too far so we think about what it means to be an adult human self we often put a great deal of emphasis on the the level of personal identity you know the me being Anil Seth you being Chris Williamson we have these we have these identities in particular people and at the level of personal identity the social aspects is very important we have to differentiate ourselves from others and we have to at the same time predict the behavior of others too so modeling the minds of others is is absolutely key to our actual everyday Behavior and it may even be key to some aspects of what it means to be yourself so it could be as some people have argued one of one uh one of my mentors Chris frith has made this case that the reason we know about our own mental States like you know when I have an experience I don't just have it I know that I have it I can talk about it the reason I have this insight into my own mental States is because my brain first evolved the ability to predict others mental States and it's that kind of theory of mind that then wrapped itself back into within the organism and gave each individual a more elaborated sense of self I think that might be the case but I think you can go too far and say as some do as well that that's necessary for any kind of Consciousness that that's why we have conscious experiences and that's why we have selves for me I actually go right the other way and I say the origin of the predictive brain the reason we have predictive brains is fundamentally because of the brain's need to control and regulate the body if you think about what brains are generally for not only in humans but in other animals as well the primary duty of any brain is to keep itself and the body alive and the best way to regulate the body is to be able to predict what's going to happen to it prediction is that any control engineer will tell you when you can have a predictive model of a system you can much better control it because you can stop it going wrong before it even starts to go wrong like if you had a if you had a central heating system or an air conditioning system that predicted the change in the outside weather you could keep the temperature of your house much more stable rather than just reacting to changes as they happen so for me that is the fundamental reason why brains evolved this ability to make predictions about sensory signals and everything else gets built on that our ability then to predict what the body is like to to make perceptual predictions about what's out there in the world I think it's plausible all this Machinery rests on this fundamental imperative to stay alive eventually social predictions become important as well but if you want to figure out what's fundamental I don't think we look there that's very interesting it's very interesting to think that it it's not necessarily what what's important what you've done a ton of experiments that kind of show how the predictive as opposed to the perceptual side of the brain can cause people to erroneously predict I guess could you explain some of your favorite uh examples of that so there's there's another this is one of the fun things about this kind of job is that the experiments can be quite Illuminating but also entertaining and this idea that what we perceive is a kind of controlled hallucination begs the question if we change things can we change people's experiences in ways that would be aligned with this idea we've done this in a few different ways so in one experiment we wanted to simulate what it would be like when people's brains had overly strong perceptual predictions so the control hallucinations become a little less controlled you know more little hallucination and sorry let me say that again because I'm a little bit so we wanted to try and understand what would happen if people's brains had overly strong perceptual predictions so a little more hallucination a little less control in the controlled hallucination and we did this by using a neural network the sort of thing that's pretty old hat now given the developments in AI but a powerful neural network that's able to classify what objects appear in different images and we ran it backwards using an algorithm that was adapted from what Google called Deep dream we ran it backwards so basically it just takes a category of object like dog and IT projects that back through the image to simulate the kind of hallucination of dog and we did this with a 360 degree panoramic video of Sussex University and then we gave people headsets virtual reality headsets to wear and replayed the video so they could look around in all directions and see what was going on and the result is kind of striking it's a really immersive experience and it's a it's a model not of what people do or how they behave but it's a model of a different kind of conscious experience and the initial experiment was just a proof of concept it wasn't really like any specific experience people said it was a bit like psychedelics but I didn't think it was and now what we're doing is making it much more specific so we're taking this proof of principle and we're developing it so that we can model different kinds of visual hallucination so people that have Parkinson's disease have hallucinations of a specific kind people who have visual loss have hallucinations of another specific kind and we can now begin to understand these differences in terms of different ways the predictive brain can go wrong and by doing this we can understand much more about how the predictive brain works in the normal case again there's a lesson from engineering here that if you want to understand how a system works you kind of look at how it breaks in various ways and that gives you a clue about what's going on in the normal case which you might otherwise miss things that you would take for granted so that's kind of a cool I'm enjoying this experiment because it involves just modeling weird kinds of experiences and then going out and testing whether they accurately reflect what people in the world with these different kinds of hallucinations really experience we've also seen other sort of experiments where people have had their is it corpus callosum severed and then you can do all manner of strange things with different hands right hand being related to the left hemisphere and left hand being related to the right hemisphere you can do things where you show images to different sides and people have to put their hand into bags and select certain things out how much is that related to this discussion of Consciousness and how much is that just uh I guess an artifact of the fact that we've got this crisscross brain Body Connection I think it's very related and it's it's still absolutely fascinating area there was a lot most of this work was done quite a while ago because back in the 50s 60s 70s when people had really severe epilepsy there weren't that many options to treat it and one of the options quite a radical option was this kind of surgery it's called a calisotomy and it is basically cutting this big bundle of connections that connect the two brain hemispheres it sounds incredibly brutal but the surprising thing is that if you do it seems to have surprisingly little effects you know people they're pretty much the same and you can only find differences in these quite weird situations where you show different information to the different hemispheres and then all of a sudden it seems like something strange is going on and it's very relevant to Consciousness because it immediately raises the prospect that are there now two conscious selves sharing a single brain that's kind of weird and it's still a little bit unresolved in these days one of the side effects of better Medical Treatments repcolepsy is that these operations aren't done so much and if they are done they're not done where you separate all of the hemispheres you usually leave some some bits intact now this is great medically but it's it's kind of deprived as this wonderful strange um almost living thought experiments of a split brain and the story as it is now have a colleague a former postdoc of mine in Amsterdam yay Pinto who sort of picked up the Chase and tried to try to do a lot of these experiments have been done in the 60s and 70s again it's like a classic experiment as you say would be um you'd give you'd show a picture which one brain hemisphere would see and um it would you'd ask it to draw what it saw and then you'd ask the person what why they drew what they drew but having shown that hemisphere another word and so what's it's a it's a bit hard to explain but basically one hemisphere is usually where the neural circuitry for language resides usually the left hemisphere in most most adult humans and so the left hemisphere which sees the right visual field can describe what it sees but the left visual field which goes to the right hemisphere doesn't usually involve language it can but it can sort of do other things it can draw you know with the left hand knacks everything is crossed in the brain so it left goes to right right goes to left and when you introduce a conflict then the the left hemisphere which can speak will often just make something up to explain what the right is doing it will confabulate but it will be completely weird and wrong and you have this uncanny sense that the left hemisphere is is just unaware of what the other half of its of the brain is doing now these days it seems to be a little more finesse than that these massive separations they may be not quite so dramatic they might resolve over time but there are still differences there's definitely differences in in how people with split brain um operations how they can integrate information across the whole visual field and there is still this fundamental question about the unity of Consciousness can it be divided and what does that what does that even mean I find that it's probably not resolvable but it's it it just it provokes our assumptions about what we are I mean again we have this this idea just like the teddy Transportation experiment that we are one thing and unique and indivisible but they're all sorts of ways that the self can come apart and this is just one of them a lot people have uh areas of the brain that are removed or damaged for a variety of reasons and you know Consciousness persists perhaps their personality changes so Consciousness is it suggests at least in part distributed in some regard it can't it can't be necessary for every single bit of the brain to be operating the way it is for Consciousness to persist maybe maybe that person person is somehow less conscious if they were to lose five percent of their brain because a railway sleeper or whatever Railway screw goes through the top of the head or whatever that famous story is but it does it make sense to ask the question where does Consciousness arise is is that even a a question that makes sense it makes some sense like all these questions it doesn't make sense if you're looking for one place you know the seat of the soul I don't think it makes sense that way but one of the most uh I think most informative aspects of the Neuroscience of Consciousness in the last 20 years has been to try and identify those parts of the brain that are more involved in Consciousness compared to those that aren't and it will change it changes depending on how you look but there are some things which are relatively clear one of the things I find always a bit surprising is that three quarters of your brain if you count it by number of neurons number of brain cells three quarters of your brain does not seem to be much involved in Consciousness at all this is the the cerebellum so our brains are organized into these two hemispheres but we also have this kind of mini brain at the back cauliflower shape thing called the cerebellum it is very important in controlling how we move and maybe even in orchestrating how we think the ability to do things in sequence and so on but it doesn't really seem particularly implicated in Consciousness there are some people born without a cerebellum that seems absolutely fine all the brain activity that we when we contrast things like what happens when somebody loses Consciousness or when they're conscious of something and versus not it never really involves the cerebellum so the mechanisms that are most relevant for consciousness are elsewhere and they seem to be in the cortex maybe underneath the cortex so in the more in the more frontal parts of the brain compared to the cerebellum and here is still just a big open question there are some experiments and some theories and here I must be I must admit it feels a little a little depressing that after this long and you know the advanced technology that we've got and so on one of the main debates in the field is still about whether Consciousness is more in the front of the brain or more in the back of the brain I mean great but it's it's a bit it's a bit blunt isn't it I mean that's that's quite a big contrast and it's still unresolved and part of the reason it's unresolved is there's one extremely tricky problem with studying Consciousness which is that we only know what people are conscious of if they tell us in some way whether through words or through pressing a button or through some other way of reporting what they're conscious of and the challenge here when we look at what's happening in the brain is how do we separate what's happening in the brain that actually underlies what we're conscious of at any moment and what is just necessary for us to talk about it to report it and it could be that the experiments that say the front of the brain is critical well they show that but actually what they're showing is that the front of the brain mechanisms are important for our ability to say what we're conscious of but not for the conscious experience itself so the last few years in this field a lot of it's been about trying to get around that whether it's through Theory or through clever experimental design it's a real challenge but it's an exciting challenge because you know I think it's overcomeable it's just not simple yeah I guess it's almost like that section of the brain is a little bit more of the philosophical zombie it is the one that is able to explain it but less so the one that is actually the experiencer of it that that that's a very nice way to put it that may be the case but then there are other people who say no actually those are the same things it's kind of the ability to explain what's going on in another part of the brain that is the experience so there are various theories like there's a theory called higher order thought Theory which basically says that that Consciousness is in the act of one part of the brain explaining or looking at another part of the brain but then other theories would be the other way around so given that it seems like there's varying parts of the brain that are involved in varying degrees to our experience of Consciousness and there are chunks of it that are the latest in terms of our Evolution to develop that seem to be a little bit more uh advanced is it right to say that lower order animals in that case aren't conscious have you got any idea whether or not other animals are conscious do they meet a threshold or a test by which you would be happy to say that they are it's so interesting you mentioned test and one of the active projects I'm involved in right now is what do we even mean by a test for Consciousness and how what would we want from one and how might we develop it because it's not just in non-human animals it's also in brain damaged people it's in newborn infants and it's of course in new technologies like Ai and also neural organoids which are collections of brain cells grown in the lab there's lots of lots of areas where we might want to test for Consciousness because well firstly for moral and ethical reasons as soon as something is conscious it has some sort of moral status unethical status for non-human animals I personally think it's very hard to know for sure but this is part of the problem we can't ask them but if we look at the preponderance of evidence in terms of what brain mechanisms are shared with other species that we know or have good reason to believe are important in human consciousness then I think it's fairly clear that all mammals have some kind of conscious experience even if they can't tell us about their conscious experiences they share the same parts of Cortex and the bits underneath the cortex the thalamus that that just are very deeply implicated in human consciousness when you get Beyond mammals it becomes harder because we don't have a consensus Theory Of Consciousness that we can generalize to to other things very easily it's going to be a kind of what's our best guess you know what what's the best thing we can say with the limited evidence that that we have and here it depends on what kind of theory about the most important aspects of Consciousness if you think as we said earlier like if you think having a sense of theory of mind and being able to predict what other people other animals are going to do is important maybe it's quite restricted if you think Consciousness is co-extansive with something like intelligence or social intelligence then maybe it's not present in that many other species my dog doesn't know whether I'm going to go left or right or whether it's whatever time or this other time but it might even you might some people might even make a stronger claim that because your your dog can't do that it's not conscious at all precisely yeah yeah I think I think this is I I find this unappealing and not just unappealing because I like to think dogs are conscious but I find it theoretically unappealing because I think that the roots of conscious experience are in the the need for brains to regulate the body to keep the body going in environments where there's a lot of information in their sensory world that pertains to how the brain regulates the body so if you think Consciousness is more rooted in this this fundamental process of physiological regulation then you're going to be more liberal about how many other creatures have it and you might start to think okay you know it's not just mammals it's it's it's maybe Birds it's maybe cephalopods like octopuses and Squid I'm down for I'm down for octopi I'm down for octopi being conscious man I've read enough sci-fi stories about super intelligent octopi um what is the most commonly used definition of Consciousness that is the barometer that most researchers in this field are using to work out whether a threshold is being crossed or not so the definition doesn't really provide a threshold which is part of the problem I mean the definition that most people use people use different definitions but fairly good one comes from the philosopher Thomas Nagel who says for a conscious creature there is something it is like to be that creature it feels like something to be me it feels like something to be um a dog but it doesn't feel like anything to be a table or a chair it's what makes a conscious creature more than just an object that's the intuitive definition that of course is just a description it doesn't give you something that you can then go and measure and the the consensus about what to do in that what to actually go out and measure well there is no consensus it's a very febrile area of discussion and and it depends what kind of Consciousness people are looking for so a a well used test in the sense of that's been used a bunch of times is the mirror self-recognition test so the mirror self recognition test asks whether an animal knows in some sense that its mirror image is itself rather than another animal we humans we do this naturally we look in the mirror and For Better or Worse we know that it's us but this ability in humans doesn't appear at Birth it takes several months it takes probably over a year to develop in in human infants what does this mean it means that it takes a while for that aspect of self-consciousness to develop it does not mean that Consciousness was entirely absent before then it just means the aspect of perceiving oneself as a distinct entity that might take quite a while and may be restricted to a few species rather than loads of species at the other end you might say something about responsiveness to pain and here I have a lot more sympathy so you can look at what animals will do when they are subjected to some something damaging or painful and not just do they run away but do they do the kind of constellation of behaviors that we associate with our conscious response to pain do we tend the wound do we go to somewhere where there's anesthetic available um do we change our whole organization of our Behavior so as to Aid recovery I think this is I think it's the most sensible place to look it might it might be a bit you know you have to pick where on the scale you want to you want to make do you want to be overly conservative or overly liberal because you're not going to get it bang on so in in my you know my feeling pain is important if if a species if a creature has the ability to suffer and then it's really deserving of a place in this sort of charm circle of ethical moral consideration yeah I was thinking about a snake and uh something tells me that a snake can't reflect I can't uh recognize itself in a mirror but if you stick a stapler into the side of it it's it's probably gonna know it's gonna know for sure yeah yeah I don't know I mean I have actually no idea whether anyone's done the mirror self recognition test on a on a snake I mean this is also part of the problem these experiments are quite hard to do and we've only studied a handful of species with anything that's hard to do and I'll get get a snake get a mirror stick it stick it on the floor you know what I mean well you know you say not hard to do but you get you know you have to do it several times and also there's many reasons why animals fail this test like um many animals don't like to make eye contact and some don't like mirrors so they're just going to fail this test for reasons for other reasons so even then you don't know how to interpret the results I was thinking as you were explaining the mirror self recognition test I was thinking about uh bats or voles that have got particularly poor eyesight basically no eyesight or what about an animal who's had both of its eyes damaged yeah if it's never able to detect itself does that mean that it's no longer conscious again like yeah probably not right I mean that that was Thomas Nagel's point in his his paper where we where the definition of Consciousness came from that we we've been talking about his paper was what is it like to be a bat and it's a very interesting thought to experiment because bats of course have echolocation we don't have anything like echolocation um so it will be impossible for us to experience being a bat unless you actually are a bat with the potential exception of not Batman but there's this there's a few people who have developed so-called human echolocation so people who've gone blind or who are born blind and have developed the ability to make clicking sounds and perceive the layout of their environment through processing The Echoes to these clicking sounds I find this really really interesting it's it's you know we our brains didn't evolve to do this so it's not going to be as good as a bat's not as good as a bat but it's it's the closest that we might be able to get the weirdest first date that I ever went on was it I think it's called Cafe Noir in London have you heard of this is this where they serve food in total darkness correct and it's blind it's only blind servers now I think that rather than using echolocation the servers have just memorized the rooms layout incredibly well but you know my bedroom I tried to go to the bathroom last night without turning the light on so it wouldn't ruin my sleep and I crashed into something I've been in that room you know hundreds of times so there is some part of their spatial awareness their proprioception which has been tuned up for them to be able to carry plates through a room with tons of people in all talking and not drop it on the wrong person remember where they're going find the person of where they're going etc etc um but yet that was that was the first day I don't know what it says that this girl decided to take me into a room where she literally couldn't see me um I'm not really too sure what that says about our first date but it was really fun actually and I remember thinking at the time there's something going on here there is something that has happened to allow these people to compensate for yeah it's fascinating and the thing is I know your example of you kind of stumble around in the darkness trying to find a bathroom but you know if you if you adapted to it if you gave yourself time and you can do surprisingly well at picking up just these very subtle cues out there and if you think about these waiters in Cafe Noir imagine like how much better you get at moving around in the dark after just trying to do it for an hour and then just imagine that they've done it for a lifetime maybe it's not so surprising that they're that they're really good but about the the mirror thing I mean it's true that we tend to overemphasize or we tend to strongly emphasize visual stuff as humans we we feel we're very visual creatures and again that bias may lead us astray when thinking about other animals the mirror self-recognition test seems to be a visual test but there are some researchers looking for instance you know didn't even go to bats you go to dogs dogs uh they have vision of course but for dogs smell olfaction is so much more important so there are people trying to develop an olfactory mirror test for for a dog and I'm not don't ask me quite how it works I have no idea exactly what they do but I like the I like the point that that if you you have to you have to try and understand the ecological niche or as the there's a German philosopher psychologist called Jacob Von erkskill he came up with his concept of the unvelt the kind of lived world of another animal so if you're a bat you know your world is suffused by by a co-locatory signal so you kind of would have a sense of where things are and it wouldn't be visual but it would be like having radar or something like that and then bees have another unwelt entirely where where the light reflected from um in the UV or infrared becomes very prominent and I think this is a there's a wonderful book by by Ed young called an immense World which which really highlights that it seems as though we're sharing the same world but if you if you have you know a human a mouse a bat an elephant all in the same space and assume they're all conscious and ask well if they are conscious what would their experiences be like their experiences are so different well I suppose what's interesting about that example of having a number of different animals within the same environment and then let's say that it's a maze or the they they just need to go about and do the normal thing they need to maybe find some food and some water and do the rest of it from the outside you can observe Behavior which looks like it could be coming from the same place right because the net outcome of their behavior is the same it may do it in different ways but the outcome is that they eventually find some food and they find some water and they go in shade when it's hot and they go into sunlight when it's cold and blah blah blah but internally how each of those animals arrives at the thing that it's doing to track down the food the human May heavily rely on its visual field the dog may heavily rely on its olfactory senses the mouse may use if it was a bee the B would have UltraViolets um it can see ultraviolet light so okay you're you're able to produce Behavior which is not only adaptive and useful but from the outside might not look all that different and yet the root at which each animal got to it is completely different well let's Linger on that for a second I think there's there's something worth unpacking here because in this example of I don't know a mosquito an elephant a human it sounds like a bad joke doesn't it go into a bar and um they're all in the same bar and I think in this case the behaviors are quite different like in a mosquito will detect levels of carbon dioxide and you know be able to use that to find skin I think that's what they're sensitive to I can't remember now but they'll be sensitive to very different kinds of things and and and we'll do things that seem a bit uncanny like you move around in the in the dark you know mice was so sensitive in their hearing and sense of vibration that they'd be able to run away owls can hear things at such a vast distance that it the behaviors would be different and so it's maybe easy to recognize that the perceptual world the unveiled of these creatures would also be different to us I think where we might make mistakes is actually within a species so if you have a bunch of people in this room in a room and they're all you interacting with each other then you're right they may all do the same sort of thing they may all look for food they may all go from to the shade when it's hot and so on and just in general in our everyday lives we tend to expect people to behave in a way that we might behave more or less and so it's very easy then to assume that other people experience the world the same way we do because their behaviors might be relatively consistent compared to you know the difference between me and a mosquito but I think this is a mistaken assumption it seems to us we see the world as it is and we use the same words often to describe things like I see a red car you see a red car we both say it's a red car and so we assume then that we're having the same internal experience of this shared objective reality and I don't think that's true in fact I know it's not true in fact this is not a new thing to say there's plenty of evidence out there of people who experience the world in very different ways you know that have hallucinations and so on have synesthesia when people see colors when they hear sounds and mixing of the senses and of course there's the whole area of neurodiversity which really highlights that there are there are substantial differences in how different people encounter a shared world but I think we still underestimate what's going on because at the moment unless we are hallucinating or unless we associate ourselves with a neurodivergent condition like autism or something like that it's easy to assume that we're neurotypical and we experience the world just as it is and I don't think there is such a thing I think that we all differ and understanding that unpacking that I think is a great challenge because we we know the importance of taking into account and actually um really relative relishing I'm trying to think of the right the right word here not just taking into account but um recognizing the value of diversity that we can see on the outside you know diversity and cultural background and in in body shape size and so on but we also have this inner diversity and it's if we don't recognize it that it's there because we use the same words and it seems as though we see things as they are I think we're losing an opportunity to um benefit from A diversity of ways of perceiving of ways of seeing things and this is a this is a sorry it's a very long-winded way of mentioning that we have a project at the moment called the perception census which is trying to do exactly this it's a big citizen science project where we ask people to join in and do a bunch of pretty simple and fun little interactive visual Illusions and so on to try and help us get a picture of perceptual diversity to map out this hidden landscape of of inner variation and it's online it's all you need is a computer and you're making people go if they want to try this up if they just um look for perception census just type that into Google or go through my website just look for anilseath.com and take you straight there and you can do a little bit you can set it aside come back and we'll keep track of your progress and you'll learn a lot about perception and your own particular Way of perceiving the World we've already had about 26 000 people try it now and from 100 countries so we want to make this a real real Landmark study both to map out this perceptual diversity but also to raise awareness that it's actually there and I think that will be of quite some significant social value talking about perception what happens when you took LSD quite a lot I mean I didn't take LSD until I was in my 40s I didn't have the opportunity or probably the desire when I was a teenager in South Oxfordshire and at some point it seemed like the right thing to do I guess I really wanted to know what it was like from the first person you know thinking about consciousness a lot for me it doesn't do this for every researcher in this area but for me made me very curious about what kinds of conscious experiences are available because part of the whole motivation for me is understanding what we take for granted in our own experience because it's always been there it's always been some particular way and not another way so ways to get out of the perceptual habits that we're in I think can be very Illuminating and there are many ways to do this there's there's meditation there's jumping out of a plane there's all sorts of things right but psychedelics is one obvious way and very reliable it's very reliable and it's and it's reliably substantial you just know so well this is what I was expecting this is what I'd been told and in fact this is true right you you put some you put a little tab on your tongue and under your tongue and then stuff will happen and it will happen for a while and I think I was I was both reassured and surprised and the way to explain that is nothing happened that I didn't expect to happen but the fact that was happening to me was still surprising and what it involved was large changes in my perceptual environment you know things became much more fluid things became much more changeable there seemed to be this influence that I could have over what I was perceiving by almost willing clouds to change into things they did things started to bleed together and things became imbued with this sort of sense of quite magic and they would there would be this quality to the whole environment that that changed and of course the sense of self changed as well and and it's very it's a notoriously hard to describe these kinds of experiences without sounding entirely enough I think Michael Pollan has done a good job in his book how to change your mind well if Aldous Huxley you know if we have to call on one of the greatest wood Smiths of all time to try and tell us what he thinks and does a perception then yeah yeah it's it's hard and I I don't want to mangle these things and rather just appeal to these kinds of authorities but but it was it was yeah I I've been prepared to be disappointed I think about okay it's it's well that wasn't quite as transformational as I as I'd been hoping for but it was I was not I was not disappointed and it is it is remarkable I think the other thing that it's interesting that for me it just reinforced the the idea that I went in with that our conscious experiences are biological phenomena in the same way that anesthesia did you know anesthesia for me shows that you can if you change the brain in a very specific way you change Consciousness in a very reliable predictable specific way as well with anesthesia it goes away and then comes back with psychedelics again your your intervening in the system in a very precise and very specific way and your conscious experience changes in a very you know the details may vary but the overall trajectory of what's happening is very predictable yeah so the implication here is that if Consciousness wasn't something which is as you had predicted it shouldn't be able to be impeded or imposed on by these sorts of substances you shouldn't reliably be able to change it because it should be something which is outside of the the the the changeable it's interesting because some people would take entirely the opposite conclusion and the fact that a psychedelic experience may give you a sense that you you're outside of your body or that yourself is part of the universe may take these experiences at face value and reach the conclusion that their normal conscious experience is some kind of heavily filtered down version of the perturbed version of the molested perverse version of what is true it always it always happens to be that what is true involves psychedelics you know it's never what is true is your mind when you're sat on the toilet like that's it's never that state it's always a state of sort of psychedelic Bliss yeah and and that's I mean that's one way you can go and you can say now I've seen things as they really are the blinkers are off the filters have been have been removed that for me is not an appealing way to think about it it is for me it is yeah you change your brain you change your experience it's exactly what you'd expect to happen if our conscious experiences were embodied biological phenomena moving Beyond just your research how has all of the work that you've done into the nature of self changed about how you think about problems or deal with the the challenges and the joys of Life have you found that it's sort of impacted the the way that you relate to emotions it's one of the things we haven't necessarily mentioned is emotions for all that they may be this phenomenon that exists and they're kind of that or or there and not there at the same time they feel incredibly real they feel like the most real thing that you can think of you know going through anxiety it's it's the reason why uh the Greeks and the Romans personified the gods right because it felt like something it was such a visceral experience that it could only be bestowed On You by a higher power that was cursing or blessing you specifically and I'm interested in how all of this time thinking about the nature of self and Consciousness has changed your relationship with your enjoyable and unenjoyable experience of it yeah emotions that they're definitely real as our experiences and they're probably the most important experiences we have I mean they they're what matters and they guide and direct our Behavior every minute of every day they're real in in the same way that colors are real I think they don't exist out there independently of a mind but they are critical to our mental lives in my work I think of that connection even more tightly so an emotion for me is another kind of perception it's a perception of the state of the body in the context in which we're in it's a perceptual inference about what's happening in the body and so they're very tightly coupled and thinking about this a lot it's always a challenging question to try and understand what its impact has been on me personally partly because I don't have a twin brother who went off to be an estate agent to compare against but I think it has had an effect however unreliable that introspective conclusion might be and I mean I can kind of see it maybe it's just getting older as well but I can kind of see that I'm a bit more adaptively detached from the transient flow of emotions than I was not entirely I mean I'm not trying I'm not claiming to be some sort of enlightened um monk I mean I still feel frustrated anxious sad upset furious at times happy too sometimes now the the flow of emotions is still there but I think it has helped me in the round to navigate things more effectively and of course one the goal isn't to be uniformly happy I don't think the goal is to just be able to um accept the stream of emotions and curate them a little bit but to to live a life where they're part of you and you don't try and fight them quite so much I think in one specific area I can see progress so for a few times in my life I did suffer depression I had it pretty bad and and and when you were saying that the visceral reality of things like anxiety I know this very well and these were you know the hardest times in my life how to get out of those is you know it's a great challenge everyone does it in their own way but I think ing about the impermanence the constructed provisional nature of the self and of emotional responses has helped me in this regard a bit it provides a little bit of a psychological immune system it may be a bit similar to to meditation now people who've done a ton of meditation also learn to pay attention to their emotions and their mental States and to recognize that their transient that they pass I think the direct experience of meditation is probably better than the theoretical knowledge you know in the same way that direct experience of psychedelics exceeds and outstrips what one might learn from the books and from experiments but I think it can get you somewhere and in a sense thinking about Consciousness for now 20 25 30 years that's been a lot of hours and so in a way that's been a lot of some kind of meditative practice on the nature of the cell phone of perception and I would be I'd be disappointed if it had no effect I think it has had an effect and I think it's had a beneficial effect though you know there's still a lot of work I'm still very much a work in progress and also ladies and gentlemen if people want to keep up to date with the stuff that you're doing online where should they go the easiest place go to my website it's anilseath.com or you can follow me on Twitter I still use Twitter Anil K Seth and I really appreciate you I look forward to seeing what you do next I've been a fan of your work for a long time so it's been very cool to catch up today I'm so glad we were able to have this conversation I know it took a long time to arrange thanks so much Chris what's happening people thank you very much for tuning in if you enjoyed that episode then press here for a selection of the best clips from the podcast over the last few weeks and don't forget to subscribe