The Infinite Monkey Cage - What Is Reality?

Episode Date: February 1, 2016

What is Reality?Brian Cox and Robin Ince are joined by US superstar neuroscientist David Eagleman, Professor Sophie Scott and comedian Bridget Christie to ask what is reality? Is our sense of the world around us a completely personal experience and a construct of our brains? How can we ever know whether what one person perceives is exactly the same as what another person perceives. Is your sense of the world around you an illusion constructed by this extraordinary organ, the brain, that has no direct access to the outside world that it is helping you to understand.

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You know all that stuff that we can't fit in? Yeah, what you mean into the general recording when it goes out on Radio 4? Yeah, well I think we should put it in something else. What kind of format could we place a longer version of Radio 4 Show in? Well you know those pod things? Yeah, like with aliens in them. No, the ones that are like a thing that you can play. An elongated audio recording that you can deliver electronically to different devices and then listen to it at your leisure. Well, I've made that already and they can listen to it now. Don't know why you've been dragging this down. Oh, the Infinite Monkey Cage podcast.

Now. It's now. They're hearing it now. Well, not now, because I'm still saying now. When I stop saying now, they'll hear it. Simultaneity is a big question in relativity. I don't think there is such a... There's no universal now, so I don't think you should say that. You wonder why we can't fit everything into the recording. It's ridiculous. Hello, I'm Robin Ince. And I'm

Brian Cox. And today we're talking about the nature of self. And, hang on, no, I am Robin Ince. Thank God for that. Yeah, that is a relief actually, isn't it? Because that does mean that you still look young and lovely and I am old and specky. So, but in my finest cardigan. You don't wear cardigans, do you? Not really your telly

thing. So, today Should we swap? It won't work. It really won't work for me. Go on. This is going to be brilliant on radio. Yeah, this is, there we go. This is my third best cardigan, and you're wearing a corduroy anorak, so... Can I get in?

This is the lovely thing. One of the things you find about particle physicists is they're very good at studying things, but very bad at dressing themselves. How's that? Describe for the listeners what I look like. You really... It changes your hair. It changes suddenly.

The moment you lose something which has kind of form and shape, you look like the worst date ever. You look like... Everything about the Brian Cox beauty, it turns out, was merely held in your coat. Bye-bye. I'm off to Tellyland to have your fortune. This is hot. What's it made of? This is... Well, I've been wearing it, and as you know,

the atom, there is a... The heat vibrations will heat... You know nothing, do you? How do you get away with it? An earpiece connected to Jim Al-Khalili's mind. So, what are we discussing today, Brian? Today, we're looking at our brains. How do they put together our picture of the world? How much can we trust our sensations?

What are the limits of understanding the human brain and is a strawberry red? Yes, we've moved on from dead. We are now going to be discussing whether a strawberry truly is red or not. So, to guide us into this world of neurons, we are joined by a panel of great brains who are... David Eagleman.

I'm a neuroscientist at the Baylor College of Medicine and my favourite part of the brain is the mind. Ah. My name's Sophie Scott and I'm a cognitive neuroscientist from University College London and my favourite part of the brain is Heschel's gyrus. Heschel's gyrus. Heschel's gyrus. I like it for two reasons. First of all it's where sound first enters the cortex and it's very complex, much more complex than visual processing. The other reason

I like it is it kind of dates from a time when people could investigate the brain and name a bit after themselves. So if you look at Heschel's works, he actually drew or had drawn pictures of his gyrus with his face on it. Here I am, just Heschel, hanging out with my gyrus, looking pretty good. And there's never going to be a Scots gyrus. That's happened, they've gone, all the bits have been named. So I have to hang on to sort of, like, vicariously

enjoy naming bits of the brain through Heschel. And our final guest is... Hello, I'm Bridget Christie. My favourite part of the brain through Heschel. And our final guest is... Hello, I'm Bridget Christie. My favourite part of the brain is the hippocampus. Is it because within it, it has the word hippo? It has the possibility to enlarge. And as a lady... Anyway, sorry.

And this is our panel! Thank you all! panel. David, there is clearly a physical reality outside our brains. We just established that, first of all. So when we ask the question, what is reality? What are we actually asking? So I'm asking, what do we perceive? So we all have this private subjective experience from the moment you wake up in the morning and you feel like you're being flooded with your senses. But that is a construction of your brain. And it sometimes has very little to do with what's in the outside world. So of course, there's an objective reality out there. And the job of physics is to figure out what that looks like. But what you perceive, how you misperceive things, how you

perceive colors and the taste of feta cheese and your whole world on the inside, that's the part I'm interested in, that reality. So the job of physics is to describe things as they really are, and the job of biology is to sort out the mistakes that we make. No. I mean, I see biology, neuroscience in particular, as a really strong inroad into understanding ourselves and why we have the kind of experiences we do. And I have a suspicion that physics is you know we have to work through this filter of our psychology the way we even build physics and there's a lot of physics

that we won't have discovered yet or will be difficult to discover because of the way we're trapped inside of our own heads so sophie how much can we know of what kind of shared reality we actually have well part of it comes from just doing straightforward good psychology and actually investigating how people perceive stuff and finding what's common across people. And if you think about it, if we didn't have some shared reality, we wouldn't be able to use language because words wouldn't have the same meaning.

If my meaning of red meant something totally different from everybody else's, there'd be no point in having it for any kind of meaningful discussion with people um and basically the history of a lot of psychology has been really spelling out the tremendous mismatches between what it feels like the world is like and what actually is what we are perceiving and visual processing is a very good example i feel like when i'm looking at you i can know where david is and i know where brian is but in fact i've got very poor representation of david at this point and if he was to start sticking his tongue out at me i probably wouldn't be able to tell but don't um but and that's because actually i'm looking at you when i when we look at things in the world

that's actually where we've got the best visual acuity the best detail and it drops off very rapidly and we feel like we have a good representation of the world because we move our eyes round about it all the time. So we're filling in, like somebody doing a jigsaw, the space around us visually, but at any one time we're seeing very little of it. And even more extraordinarily, when you make those eye movements, when you saccade your eyes around the world, that's the word used for these ballistic, fast eye movements,

your brain actually turns off visual processing, so you don't see anything at all. It's why if you look at yourself in the mirror and look from one eye to the other eye, you'd never see your eyes move because your brain's actually shutting things off. You don't notice that. Your brain fills in the gaps. So you have your experiences of a smooth, continuous visual reality that's simply not there. So we're holding a model, a three-dimensional model, essentially, in our brains, and just updating it every now and again. Well, you're updating it continuously, yes, but that's one way of considering it.

You never have access to all that information, and you are guessing about what's there if you haven't actually looked there. So you could right now remove half the audience and replace them with cats, and I would probably notice when I looked, but up until that point, unless I check, I won't know. Sorry, just to mention mirrors, And I would probably notice when I looked, but up until that point, unless I check, I won't know. So just you mentioned mirrors, about how much of what we see is in terms of brain fabrication or filling in the gaps. There's the thing that I've tried this, in fact, that thing where if you stared, I don't know if anyone in the audience ever tried this,

if you stare directly into a mirror with a low light behind you, and if you stare directly into your own eyes, after about, I think it's somewhere between 30 seconds and two minutes, your head seems to change. Some people will suddenly, I've heard one of the most common ones, is you will appear to be very, very old. You suddenly see yourself as tremendously old. Other people see their heads pulsating. Other people have this experience where their head seems to disappear. And apparently, I was told, because when I tried it out,

it's really good, by the way, it is quite a buzz. Can I just ask, Bridget, is this the life of a stand-up comic? Particularly bad show, have you stood there staring into your hotel room mirror for over two minutes to see if your head pulsated? Or is that just Robin Ince? I think that might be where I'm going wrong, actually. No, I've never... I don't tend to stare at myself.

I mean, I would if it was for an experiment, but I think it's quite an odd thing to do, to stare at yourself in the mirror for ages until your head starts moving. I agree. I don't think that's odd at all. If you have the choice... What does that say about Robin? He's persistent. I think it's difficult.

In fact, it happens if you stare at anything, because it's a really unusual thing to do. What your eyes want to do is jump off around the room and sort of explore everything. So actually, if you stare at anything, really crazy stuff starts to happen around the edges. This is not mad, is it? No.

This is real. Right, David, you're from America. This is... I am not... Right, this bit, because the audience now, they're staring at me so much that I do feel like my head's pulsating. This doesn't rule in or out that you're mad, but it does illustrate this very important point about the internal model. So the internal model is this issue that really your perception of the world has to do with this internal activity in your brain.

And you get just a little bit of data dribbling in through these two holes in the skull through your eyes. And that little bit of data can modulate what's happening internally. But essentially everything you're seeing is happening in the closed theater of your cranium. That's where the show is getting played. So if you stop taking in information because you're staring, and as Sophie pointed out, your eyes want to move around and gather bits of data. So if you're staring and leaving out some of what's out there, your brain will start having its own reality trip. And of course, we experience this every night when we go to bed, we have our eyes closed and you still have full, rich visual

experience, but it's now unanchored from any data coming in. And so you go off to whatever reality you want. And the really strange part is you believe it, whatever your brain's serving up to you, and you're in the middle of a dream, you buy the whole thing. And what do we know about the physical processes that are happening in the brain? So when you're building this model, you're seeing reality, the external reality,

what is your brain actually doing? So the wrong way to think about it that's still in a lot of introductory textbooks is that light hits your eyes and it works its way towards the back of your brain and then up to some end point and then you see like a camera. But in fact, it's just the opposite that's happening. Your whole visual cortex, the back of your brain, is generating this world. Essentially, it's hypotheses about what it expects is out there. And then the little bit of data coming through your eyes is compared against that model. And all that's going back to the visual cortex

is just the difference, the violation of those expectations, what it got wrong. That's how it's working. So it's actually like the system is running backwards from the way you might imagine it. Bridget, do you find this as, how disconcerting do you find this idea that in fact our reality our perceived reality that you know just hearing Sophie there talking about the fact that when you're looking at images and how much of the that is just going you're actually not seeing anything we are now just fabricating this for you for practical use for speed I presume in some ways almost to save energy perhaps all of these different things. How do you feel about that, Bridget? I find it quite comforting because I'm often told by people

that I have no grasp on reality, and now that I've got this information, I'm able to say to them, what is reality? There is no reality. I think what you mean to say is that you have no grasp on my reality. What I'm really interested in since I read David's book was, if we can agree that there is shared reality, i.e. that the things that a lot of us see,

a lot of us think are the same thing, how did two separate individuals have a shared reality that is not based in a common reality? So how did two different people see the same ghost? They don't exist. They don't. No, but two separate people can have two experiences that is not a shared reality.

Something that's not there. Yes. I don't accept that. Ah. Don't be surprised, he's a physicist. Well, no, that's a good question. I mean, so if indeed two people and they're in two different places i can't answer the ghost question um because because i'm i'm with

brian on this one that i don't think there's any good evidence to support that i'm not saying there's ghosts either okay but i'm saying that there are people who believe and who are in different different places i think i can't answer answer this. So I mentioned that your reality is constructed in this closed auditorium of your skull, but the machinery in there is shaped by your genes and, more importantly, your culture, every experience you've ever had. So if people are in a culture where ghosts exist

as part of the mythology, then an interpretation of some external stimulus will naturally be interpreted in that framework. And it's not surprising if several people in the same culture will have the same interpretation because of their shared history. And you find that with people sort of saying, I've toasted this piece of bread, and I've seen a figure of the Virgin Mary in it. That never happens to people who aren't already religious. It simply doesn't happen. So you only see this sort of experience of seeing something,

over-interpreting something that's clearly there, but it looks like something to you. I usually see brains in toast. My bagel has Richard Dawkins in it. Don't eat me. It only happens if you already believe in the larger phenomena. So if you're atheists, don't find pictures of Jesus in toast.

It doesn't happen. So those people who see the same thing that isn't there... It can be driven exactly as David's saying, by their expectations and their beliefs, because that's feeding into this sort of... Perception is highly interpretive. It's not sitting around going, oh, what's going on? Let's have a look.

It's going, oh, is that a cat? Is that a cat? Is that a ghost? Is that Jesus? I just want to question how much is actually shared. So Sophie pointed out earlier that, you know, we can transact in the outside world with, let's say, the color red. If I say, hand me the red thing, you'll sort of know what I'm talking about.

But beyond that, I think language is really low bandwidth and that we don't share... Language doesn't represent something that's truly shared. So if I say justice, that means something in my head, it means something in your head too, and everyone has a different entire history of what that word might mean. And this is true with every word in our language. I think there's, you know, when you draw out the diagram of overlap,

there's not that much overlap between people, perhaps. Well, what is this isn't i'll start with you so that in terms of within human cultures what is the greatest disparity we see in different cultures in realities if you say i mean like we we often hear time being used about different groups different tribes etc will have a different sense and feeling of the past and the future and the way that it is expressed which suggests some kind of do we see are there any particular groups where you go the difference between uh you know traditional kind of say you know anglo-saxon tribe and then other

tribes you definitely do find it so um you can find differences actually in color depending on whether or not you've got words in your language for colours. So we only relatively recently got a word for orange, and before then everything was red or yellow. And you can find environments where people speak a language that doesn't have particular colour words, very often round red, orange, yellow colours. And they just don't see colours that way, they describe a different spectrum. So they are seeing the same world as you, but they are really not at some level seeing the same thing and the argument is that language moderates that actually to go back to david's point you can consider language to be a map of the world and you kind of fill in the details that you need so we kind of get by with

a map that works for everybody but as soon as you for example you want to learn a skill you want to become a wine taster or a doctor you start learning new words to describe the perceptual stuff you need to know to do that or a comedian or a physicist any kind of any kind of expertise involves new words and new mappings so it's definitely find ones associated with language and they go across expertise and across cultures you also find differences in emotional experience so you can find emotions that are expressed similarly across all human cultures like laughter and they you kind of find them everywhere people recognize them and then you find other emotions that are extremely culture specific there is a kind of mad fear associated with um uh certain eskimo cultures

where people or inwit cultures where people kind of go completely wild with fear and they run around and they tear off all their clothes and they eat feces and they steal things and then they go to bed and they wake up remembering absolutely nothing sorry was that me i've done that gig or a weekend in blackpool i don't know but it's um it's now we don't have that constructive fear in our culture and we on the whole on the whole tend not to go i'm sorry i'm going to go absolutely crazy steal your things and eat pieces you know we don't do it all and that that kind of example is an extreme example but there's other kinds of strong emotional experiences which are so culture specific is to suggest that they they have to be that there's not some universal

experience david given that there's a strong cultural element to the way that we perceive the world and we've also heard that there's a language plays a role the language that you grow up with and learn determines your external model and how much of that model is is innate it's hardwired into the brain and how much of it is learned and dependent on the culture that we grow up in. Much of it is shaped by the culture that you happen to drop into. So one example is language. Babies are born being able to hear any of the sounds of human languages, but as they are exposed to their native tongue, their sort of map of sound space gets crafted, gets put into shape so that they get really good at hearing particular sounds and they become unable to hear other sounds.

So, for example, a baby born in Japan can hear the difference between R and L sounds. But as the baby gets older, he or she loses the ability to discriminate those sounds. And so this is an example of being born sort of universally able to take in whatever the world is going to offer. And then the world shapes us and crafts us. So is that neural pruning? Is that basically, is that part of the neural pruning? So we are born basically with, we actually lose, but we gain more connections. Is that kind of how? That's exactly right.

You're actually gaining more and more synapses during your first two years. Synapses are the connections between the specialized cells of the brain, the neurons. You get more and more of those. By the time you're two years old, you have more than you'll ever have in your life. And from then on, it's really about pruning back that overgrown garden. And that pruning is essentially a Darwinian process. Whatever is resonating with the world and getting used stays around and gets strengthened, and the other stuff goes away. Because I would imagine if I met someone, let's say I encountered a tribe that had never encountered anyone from outside their particular area before,

tribe that had never encountered anyone from outside their particular area before, I would still naturally imagine that I was looking out on the, because I'm looking out on the same world as them, I see the world in the same way. That would be my prejudice. But are you suggesting that really that is not necessarily the case? Yeah, it's all about your interpretation and their interpretation. So, you know, the example of the piece of toast, you would see something in the artwork that they're showing you. They would be seeing something else. I think what's even more interesting than cross-cultural differences in reality is all the differences we see within a culture. So this is an example, you know, 1% of the population has schizophrenia. And when somebody is in the thick of a delusion, the same photons are hitting their eyes as yours.

The same scene is hitting their eyes, but they have a completely different interpretation of what's going on. About 3% of the population has something called synesthesia, which is a cross-blending of the senses. They might hear music and it causes them to see colors,

physically have a color experience. So they're having a different experience of reality than you are. And even within your own life, moment to moment, you can have different interpretations. So, you know, speaking of this, how you interpret the toast, if you, look, I was hiking in Colorado a little while ago, and then I was suddenly told by a little while ago, and then I was suddenly told by a guide, oh, by the way, there are a lot of bears around here. So then every shadow

and movement that I saw after that, I thought was a bear because my interpretation of the world now had a different frame. So everything about how we perceive an object is about us. It's about our unique historical trajectory, what has crafted you from the moment you dropped into the world your family of origin your neighborhood your culture your experiences sophie why is the our our model of reality so subjective because um it's clearly the the ability to build these sophisticated models of reality is Darwinian. It's evolved to help us survive. But it's not so subjective, is it? I mean, we're getting basic, that's, yeah.

Why is this element of cultural subjectivity, let's say? Well, I suppose because a certain amount of it is likely to be there because of the fact that we all share broadly similar physical forms and we live in a world with the same physical properties. So even if you go to a culture that's never seen a you know white european person before anybody who's not from their group they things still drop down when they when they let go of them and you know that and they they born and they die and they've got legs and arms and they move about the same sort of way so there are certain general constraints that come from physical stuff that you that that's going to be there for

everybody um and then beyond that because we one of the characteristics of the human brain is its sheer size and plasticity and flexibility. And you can solve the bubble. Clearly, we solve the problem of perception in a number of different ways. Perception isn't only one thing. If you look in my area of looking at how people hear voices, when you hear voices, the left side of the brain and the right side of the brain do pretty much different things without the same information. And then at some point further down the line they put it together

so that when you encounter somebody you know they're easier for you to understand and that's the outcome but before that in fact there's been a lot of sort of separate processing of stuff and you've got no insight into that no but it's just a way that the brain's carved it up so i think there's constraints based on the physical nature of life and there's constraints based on how your brain is actually, well, the sheer scale of the possibilities of the ways it can solve the problem. And then beyond that, I suppose,

because we all have entirely different developmental trajectories. I mean, one of the... Do you remember when everybody got very concerned about clones? They were like, oh, clones, wouldn't it be awful if you had a clone who was exactly like you? And I was like, no, you'd have to, like, raise that clone for, like, 20 years before they're remotely like you, and you'll be a lot older by then,

so really, you're not going to have a clone catching up on you instead of appearing just like you, because their experience will be different. We have these large brains, and the characteristic of mammals' brains is our brains are big, and we have these extended juvenile periods when we train those brains up. We do not all have the same experiences in that training,

and it's a huge amount of time that your brain is developing in in juvenilia and that's giving you considerable plasticity and flexibility in just how and the finished product not that there ever really is a finished product because that does continue changing over your whole lifespan david the we're hearing there sophie describing the complexity of um understanding language and the that there are lots of different bits of the brain putting all this data together and at some point you understand the language. You mentioned the visual system. It's very complex again. It's remarkable, isn't it, that we managed to build this synchronised model of reality

from all these different... So we don't have a lip sync problem. We see people's lips moving and we interpret that and then we hear all this sound and we interpret that. We put it all together and we get this completely in sync view of reality. Do we know how that happens? Yeah, so you're pointing to a very interesting issue, which is that the different senses

will process at different speeds. So for example, the reason that we use a gun to get sprinters off the blocks at a race is because you can react faster to a bang than you can to a flash. You're much slower when signals have to work their way through your visual system and out through your motor system. So we've known since the 1800s

that the different senses get processed at different speeds, but what you're pointing to is this issue that when I clap my hands, it looks all synced. In fact, it feels synced to me. It feels even the time that I put out the motor command and I feel it and I hear it and I see it. Okay. Your brain is doing lots of very sophisticated editing tricks to make that seem true. And the only way that it can actually pull it off is for you to live in the past.

And I don't mean the kind of clothes you're wearing or something like that. I mean... Robin. Robin. Hang on, this is your jacket. By the way, I've also found out he doesn't turn his phone off. He's had four texts.

Yeah, you have. Do you want it now? That seems right. Yeah, what it means is that you're living in the past. So when you think the moment now occurs, it's already long gone. This whole show might be over for all we know. So that's because for your conscious mind to put together a story of what just happened, it has to stitch together a lot of information, compare compare across the senses and finally serve it up and that's the story that you have do we have any idea of what that delay is um it's estimated to

be about half a second really yeah so how does that fit with the our ability to let's say dodge a projectile that's flying towards so it turns out your unconscious brain, which is most of what's happening, can do extremely sophisticated things. So, for example, you know, people hit fastballs in baseball all the time. Those are traveling at least 92 miles an hour. The ball travels from the pitcher's mound to home plate in four tenths of a second, which is faster than your conscious mind can keep up with. faster than your conscious mind can keep up with. So I used to play baseball and my experience was always becoming consciously aware that I had hit the ball and that it was flying away from me and now it's time to throw the bat and run because your body can do incredibly complex things pre-consciously and often without

conscious interference at all. And as we automatize things, that's what our life becomes. When you ride a bicycle or walk or eat or do a hundred other things, you know, as we automatize things, that's what our life becomes. When you ride a bicycle or walk or eat or do a hundred other things, you don't even have access anymore to how you're doing it. But nonetheless, your brain can take care of it. So that means that you can, if you say a baseball is coming towards the bat, then that timing of the hit, which we can time very accurately if you're a good baseball player so that's that's unconscious it's it takes precedence so somehow your brain prioritizes that information and do this first

and i'll build the model of reality and experience it afterwards exactly there there are shortcuts where you can have visual information coming in uh making decisions hitting the motor cortex signals go down your spinal cord to your muscles. You're making feedback corrections on the swing. All of that happens. And this just, you know, underscores the point that putting together the story of your conscious experience is a separate process that's very slow

and is much slower than all that. I was just going to, I had some really good advice from a farmer. And what happened was he we were i was on his land and he said get off i was on his land but he let me be there anyway so we were clay pigeon shooting and um like i'd sort of kept missing. And then he said, just forget about it. Don't think about it. Don't look at the clay. Don't think about it.

Just imagine where you think the clay is going to be and then aim much further than that. And I didn't miss a single clay. Literally, when I stopped thinking about where it was and hitting it and went way in front of it. And that's just about the bullet travelling and all of that. But it is interesting with target sports. You're kind of not supposed to look at the thing

that you're trying to hit. That happened to Luke Skywalker in Star Wars as well, didn't it? When he had to fire the thing down, the Death Star. Exhaust force. You are such a physicist. A user of force. This illustrates an important point such a physicist. The use of force. This illustrates an important point, which is that the conscious mind

typically only interferes when something is automatized and the body can just do it. Just as an example, I'd like everyone to pick up two dry erase markers in front of you. So pretend you're holding two dry erase markers

and do this next time you're in front of a dry erase board. Sign your name forwards and backwards and mirror image. Go ahead and sign your name. So your left hand is doing backwards from what your right hand is doing. Okay, so some of you did better than others. Here's the thing. Try this when you're next in front of a dry erase board. It's easy to do if you don't think about it. The moment you start thinking about how letters look and so on, then you're dead. You can't do it anymore.

That's like walking down the stairs as well yeah yeah that's right or playing the piano or anything if you start paying attention to what you're doing you can't do it yeah you can't do it yeah you're right this is uh well by the way i loved your your clay shooting anecdote it's lovely when an anecdote's a threat as well the uh i can shoot when you're talking about the human brain and uh about its possible malleability and learning i was thinking of an experiment, I think it was Roger Sperry, who did the experiment where, I'll tell you this in a very kind of basic way, basically there's a frog which requires a certain line for a fly to go past for the tongue to then go, it's not kind of thinking, yum, yum, there's a fly, there we go.

And they took, I think, he took the frog's eye, basically basically and pretty much turned it upside down so the picture is then then upside down and what they found was the fly never learns every time a fly goes past its tongue goes in the opposite direction and then it dies of starvation yeah sorry the frog yeah the fly survives in fact it's very good news for the fly, very bad news for the frog. And that idea that where do we see in species the ability to learn... We have what appears to be the ability to change our behaviour to survive, but this frog, unless the fly goes at the right angle, that's it. It's dead. It's quite extreme. If you go to London Zoo in the reptile house,

they've got a great big crocodile skull and it's got this great big chunky plate bone running down these nostrils and eye holes. And it's a huge thing. It's really heavy to pick up. And right at the back, about the size of my little finger joint, there's a little pit. And that's its brain. Now, I can go, oh, ha, look at this little brain. If I was in the water with that crocodile, with its little brain,

it would probably be more of a threat to me than I would be to it with my lovely, great, big brain because it's got a pretty limited repertoire, but it works quite well. And obviously, you can't just line up all the animals in the world based on the size of their brains and say, here, we've got very simple behaviour, and here, we're going up through the vole, getting more complex, and then up to wonderful humans.

It's not that simple. Very, very generally, in evolution evolution you can see these step changes or steppish changes where you start to see these new networks getting built in so by the time you get to primate brains you do start to see quite consistently different patterns that do seem to relate not just to size but to extreme complexity and perceptual processing so for example mammals evolved in the dark and they lost the ability to see color this normally makes people start saying oh no no not my cat but i promise you your cats aren't see color um now primates including humans rediscovered that we found a way back to getting color information out and that's you know there's probably to do

fruit eating or something but that's just an example of the you know like a relationship between behavior and perception and actually the the changes in the plasticity and the capabilities of the brain don't they develop animals and humans parts of the brain that we need so for a crocodile can shut down half of its brain apparently and they said that it can sleep with one eye open. So that's obviously evolved so that crocodiles can catch you. And the same with... Or, you know, whatever. The same with that we develop... That's what lacks a lot of the natural history documentaries on BBC Two.

Lack the, oh, whatever. Whatever prey they like. Yeah, whatever they do with their one eye. Or just keep one eye open for another reason. And so we develop the things that we need and sort of get... Because there's a lot of the brain that we don't use, isn't there? No, no, no, you use all of it, really, honestly, you use all of it. All the time.

All of it, all the time. You'd notice it very quickly if you didn't have any of it working. Really? I thought we didn't use a lot of it. No, there's been the... Because I think you told me about it, Sophie. Because people sometimes say you only use 10% of your brain. And they did some research and they actually found out that it's not true, you don't only use 10% of your brain. Deepak Chopra says that.

Except for people who say we only use 10% of our brain who do. OK, so... Yes, thank you. It's widely said so. So when you say we don't see as much as we think we do, that's we don't physically see as much as we think we do. Not we don't actually see as much as we think we do. Your brain is dealing with a lot less visual information than it feels like you're getting because, as David says,

you've got this internal model that you're updating all the time. Terrifyingly, because you turn your visual cortex off when you move your eyes and when you blink, you are functionally blind for 15% of your day. When we're driving and we're crossing roads, we're not seeing at all. That's how profound it is. It depends how you mean it, I think. Because what we're always experiencing, of course, is our internal model of the road. And so the interesting part about our eye movements, if you watch somebody's eye movements, often we think, oh, it looks like a little camera, the eyes moving around.

But in fact, if you were to take a camera and film in this jerky fashion where it's jumping around the resulting video would would be nauseating right the reason we feel like the world is stable even though our eyes are moving like a drunk person holding the camera is because they're not a camera all they're doing is going out and finding little bits of data to add into our internal model and so you're totally right of course about while they're in movement they're not taking in new information they're suppressed they're turned off they're suppressed yeah but but but the internal model is stable yep so so it's not exactly that's why we don't experience it as 15 percent of darkness or blackness your internal model is perfectly fine it just means that only 85 percent

of the time are you actually landing on spots to pull more data into your internal model and improve it. But David, this internal model, which is what we experience as reality. So we've discussed that it's built, it's partly, I suppose, the hardware of the brain, it's partly learned, it's partly cultural, also partly based on our memories and our past experience. So what do we know about those components? If we take memory, for example, what do we know about the contribution of our past experience to our present model? Everything about your past experience has left its footprints in your nervous system. So that is what makes you exactly who you are at the moment. And the fact is that,

you know, if you look around a room, there's a lot of variation in people's faces and there's that much variation in people's brains too. Brains are unique and your experience of consciousness right now is presumably unique in the history of humankind for everybody in this room. unique in the history of humankind for for everybody in this room um and it won't last i mean we're you know we're works in progress and so uh you know tomorrow it'll be something different but but memory is intertwined into that all of your experiences are constantly um pushing you farther along on this trajectory that that you're on and what is it that's changing so so physical interconnections in the brain? Is there some sense there's a this idea of a program? You know, if you think about computing, you think

there's some program running somewhere. Is it all physical? Is it all structural? To the best of our knowledge, it's all physical and structural. One of the most obvious things that changes is the connections between the neurons. And the vast pattern of connections is summarized as the connectome, which is this huge map of a thousand trillion connections. That is, you know, like an extremely high dimensional fingerprint. A thousand trillion. So that would be, what was that? A thousand and then 12 noughts. Yeah. So 15 zeros. Yes. Yeah.

That's how many connections you have. And every one of those is passing signals multiple times a second, every second of your life. But here's the thing. The change, you know, when you learn something new, a new skill or a new fact, there definitely are changes at these connections, but probably it goes a lot deeper

than that, all the way down into the biochemical cascades inside of the cells, all the way down to changes in the nucleus that change gene expression. So we've been concentrating on the connections between neurons for a long time because our technology allows us to dunk electrodes in and look at that. The finer and finer levels are harder for us to look at but for sure changes are happening all the way down so it's always unbelievably complicated place the brain yeah if you think about how recently we've even started to ask questions about what's inside our heads compared to how long we've been asking questions about the skies and there's just an order of magnitude. It's about the last 150 years, really seriously.

We didn't even know there were... You can see people, when they got hold of microscopes, finding funny fibrous stuff in the brain. Of course, that turns out to be axons, and that's what neurons have. And, you know, we didn't know about that until microscopes got really good. So we're in incredibly early days, unbelievably early days. And think about how long it's taken us to get this far in understanding the universe well we are hundreds of years down

the line with the brain well if you think in fact i've just looked because we're at the end of the show and i've looked at how far we've got through the questions and we've actually only got to question three uh right there we go we go there's so much great stuff there we have so we are traditionally yes yeah we asked the audience a question. Yeah, we asked the audience a question. What is the one thing you would change about your reality? So, Brian, what have you got? The fact that I still come across

Comic Sans outside of primary school on an all-too-often occasion. It's not like we'd all live on one peaceful planet and there would be no war, is it? I just want to get rid of Comic Sans. It's kind like we'd all live on one peaceful planet and there would be no war, is it? I just want to get rid of Comic Sans. It's kind of a limited ambition, isn't it?

We actually know the guy who came up with Comic Sans and he still gets a lot of hate mail. In aerial bold. Anyway, so... I would change it so that I was married to Brian Cox. That's Nicky Stubman, if you'd like to stand up now, and we shall perform the ceremony. Nicky will be filling in for the other 57 people in this audience who said they would be married to Brian Cox.

This brings us to the end of the show. Thank you very much to our guests, David Eagleman, Sophie Scott and Bridget Christie. And now to end our show on reality, Brian Cox has made a list of things that he believes are not real. Brian, ghosts,

astrology, alien invaders, alien medical experiments, the magical memory of water, spine wizardry. The Loch Ness Monster. Bigfoot. Marxism. The abominable snowman.

Raymond Briggs' snowman. No! No, that's where the audience turn and tore him apart. You've been listening to another edition of Brian Cox's Real or Not Real, a particle physicist's indictment of humanity. Thank you very much. Goodbye. In the Infinite Monkey Cage Without you traveling

In the Infinite Monkey Cage In the Infinite Monkey Cage In the Infinite Monkey Cage You're now nice again. Thank you very much for listening to the Infinite Monkey Cage podcast. Now, there are other science programs available as podcasts.

We have to say that for the reasons of balance, don't we? Otherwise people might think this is the only show on Radio 4, apparently. It's the only one worth listening to, I suppose. Brian, don't have a go. What is it with you and Jim Al-Khalili? You've got to just get your differences over and done with. You wrote a book on biology.

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