You (Don't) Know Where You Are

13:18Hannah Fry:Have you heard of straws? Just a little suggestion there, Foy.

13:22Michael Stevens:Oh, man, I have heard of straws, but I never thought to connect the two.

13:26Hannah Fry:So have you worked out why this is? I mean, you have these little canals and it's about fluid moving through those canals compared to sort of, there's like hairs and little bones in there as well, right? So have you worked out why this might be?

13:41Michael Stevens:I haven't looked up the cause. I just kind of embrace it as an unquestioned part of myself. But let me see. Oh, it's got a better name. Benign paroxymal positional vertigo.

13:55Hannah Fry:Top shelf is better, though. Top shelf makes it sound like you get it every time you go to a supermarket. Reach for the beans.

14:02Michael Stevens:Yeah, it's well, the crystals in my ear fluid slide around and they start spinning like the sloshing of the liquid. I guess my brain doesn't correct for. Because when I go back down, the water isn't like, oh, you're down again. The water's like, whoa, I'm still trying to find my balance. And my brain does not interpret that. It doesn't ignore that.

14:23Hannah Fry:That's how you have to think of it. Imagine if you had a cup of tea in a car. You would be very messy for starters. But if you think that the rigid sides of the cup are going to move with the car, but you have the sort of inertia of the fluid, the fluid will like slosh against the sides. That's essentially how it works inside of your ears. So I guess, yeah, if you've got these subtle things, either in the physical structure of your system or the way that your brain's interpreting it.

14:54Michael Stevens:Yeah, for most people, that kind of confusion would only be caused by intense spinning. And then that fluid keeps sloshing after you stop and you feel dizzy. But for me, it takes the littlest motion and only looking up. If I look to the side quickly, I'm fine. If I look down, I'm fine. But for some reason, looking up, my brain goes, all right, this fluid's out of control. You're spinning. You're going to fall. Let's just fall over.

15:20Hannah Fry:Have you ever been on one of those? NASA used them as training devices, I think, where they put you essentially in the center of a gyroscope and spin you around so you can move in all directions. I did that at space camp.

15:32Michael Stevens:I earned my gold space camp wings, by the way, but let's not make this podcast about Michael's achievements. I went for three years, you know, whatever. Big deal. Point is. Wait, as a kid? As a kid. Yeah. They've got three levels and I got into them all and I loved it. I absolutely loved it. But I was a kid back then and I didn't have top shelf vertigo back then. It was like it was like a later in life phenomenon.

16:00Hannah Fry:Okay. So this is what your body's using. your body's using vision fine standard it's using your inner ear stuff but it also has this third mechanism to work out where you are in space which is proprioception so these are essentially the signals from your muscles from your joints from your skin uh your your you basically have a map in your mind that you build up when you are extremely young that tells your body where your arms and legs are positioned in space relative to your to your to your body effectively at all times um the thing is this can go wrong right so in the 1970s there was this man called um ian waterman and he had this very rare viral infection that completely destroyed all of his sensory nerves for touch and proprioception below the neck so he describes that essentially he woke up one day he knew he'd been sick he didn't lose any of the the motor nerve so he can move his muscles um but he describes how he woke up one day and he literally felt like he was a head floating on a pillow yeah like he felt as though he didn't have any body in space and he could tell that his um that his legs one was under the duvet cover and one was out because there was a temperature difference but he couldn't tell that it was legs he couldn't tell it was just the weirdest strangest feeling of being this sort of floating floating head in space um if he closed his eyes he he did not know what position his body was in, had no idea at all.

17:25Hannah Fry:The crazy thing about this story with Ian Waterman is that because he could still see his body, he was able to sort of look at his hand and go, okay, I want to move my hand from this position to that position. I want to like clench my fist. So he had to relearn how to move his body, which he could only do by visually looking at it at all times. By watching. By watching it.

17:50Michael Stevens:Wow. See, this is a sense that we don't talk about very often, proprioception. But when you imagine someone losing it, you realize how important it is. It's what allows you to close your eyes and stretch out your hand and touch the tip of your nose. Like, look at that. I didn't even look. And that's because I can feel where my body is. But if you lose that, like this guy did, that sucks. But what a phenomenal experiment and experience.

18:17Hannah Fry:Totally. So that's you knowing where your body is, knowing which way up you are, but knowing where you are, so where you are relative to your surroundings. In the environment. Exactly. There, just some of my favourite research ever has been done into this to work out exactly how your brain does it. So this story starts back in the 50s when they were doing some quite horrifying brain surgeries on people. You know, someone might have epilepsy or whatever. They would just go in and lock out a chunk of their brain. And there was one patient in particular who had a section of his hippocampus removed.

19:01Hannah Fry:And at that point, this patient could no longer recognize hospital staff. So some of his memory had been damaged. but he also could no longer find his way to the bathroom. And this was the point where people realised that there's this connection, right? He couldn't recall day-to-day events of his hospital life. And this is the point where scientists were like, well, maybe navigation requires us making memories of space in this quite specific way. Maybe us understanding where we are is down to us remembering where we've been. essentially. In the 1970s then, a little while later, there's a guy called John O 'Keefe at UCL, my alamata, and he has worked out this way.

19:52Hannah Fry:He's basically invented a very precise little hat that you can put on a rat's head. And this will measure the electrical signal from one neuron at a time inside this rat's brain. It's extremely precise. It's like the tiny, tiny, tiniest little wire is going into the rat's brain into one brain cell one neuron one brain cell exactly and this is the 1970s so he hasn't got it rigged up to anything particularly fancy it's just a little microphone that just goes pop when this neuron fires and it's in the hippocampus of this rat and this rat's having a lovely time it's running around in this little space um and what he noticed is that um this neuron would fire when the rat was in a particular part of the room so the rat would run over there and it would go pop and then the rat would run off in a different part of the room and it would go silent and only when it went back to that exact same spot would this thing go off so John and Keith are sitting there and this like it's like popcorn basically the sound of popcorn whenever the rat is in this particular part of the room so he's like well maybe there's something going on about that part of the room so he took away all the food he turned off the lights he you You know, he rotated the walls and this cell still fired in the exact same spot in the room.

21:13Hannah Fry:And as he rotated the walls, the firing field rotated with them. It's the way the rat was orienting itself. Use the right word. Orientating? Orientating sounds good too, though. I don't know. It was working out where it was relative to the walls. And that's what this neuron was doing. And this was relative to the walls? So what about in the dark? In the dark, it could still tell roughly where it was in this space. And the neurons still fired in exactly the same spot. So it's like this, it's almost like, you know, the red pin you get on Google Maps.

21:51Michael Stevens:Yeah.

21:51Hannah Fry:It's basically like this neuron is firing at that moment. Now, a little bit later, they were like, well, let's see what this neuron does when we change the room. So they stretched the room, kept exactly everything the same, but just made the room a bit wider. Alison Wonderlanding it, right? Yeah. And whereas before this neuron had fired in a really tight little circle, now the neuron fired in an oval shape where it had been stretched with exactly the same dimensions as the way the room had stretched. Wow.

22:24Michael Stevens:Isn't that cool? That's such a cool experimental design. Stretch the room and you've stretched the mental map.

22:34Hannah Fry:Exactly. Which means that our internal maps, they treat rooms like balloons, right? Rather that can stretch and that can bend. We're not taking direct exact measurements.

22:45Michael Stevens:It's like we didn't mean for this to happen, but life forms already are prepared to travel through space time with all of its curvatures and stretching.

22:54Hannah Fry:I mean, life forms live in space time. So why not? Why not?

22:58Michael Stevens:Bring on the nearly as fast as light vehicles. We're ready. So by now we have these really clear understandings of, they're called place cells.

23:08Hannah Fry:That's what they've been named. There's some amazing experiments where they have mice. So you put on the same kind of hat, you pop it on a little mouse and you hold the mouse steady, but you let its legs run on this kind of styrofoam ball. So it can run in any direction it wants to, can like move around and and then you pop the mouse inside what is essentially like a imax for mice right so this curved screen this projected space it's in virtual reality and then you let

23:42Michael Stevens:the mouse navigate through quake 2 video game you are describing like a literal mouse yes or a computer. Like the old ball in the mouse, right, for a computer, this is the same ball, but there's a literal mouse on top of it.

24:03Hannah Fry:Literal mouse on top of it who's controlling the direction. That's exactly what I'm describing. Exactly what I'm describing. But the key point about this is that the mouse believes it's in reality, I guess. It's sort of trying to navigate to a drink of water down one end of one corridor or whatever it might be. It can go in any direction it likes. But what they find is that the place cells don't distinguish between real spaces and virtual spaces. You still get this same pattern that one neuron will fire in one particular place, like a red pin on Google Maps, in this virtual imaginary space.

24:43Michael Stevens:Well, I didn't know they'd done this with mice. I did it to myself in an episode of Minefield. I worked with researchers at UC Irvine and they had me run like a rat in a maze, like a giant human sized maze. And they also scanned my brain to check the size of my hippocampus. Then they had me play 3D video games for like a week or two, which I didn't play video games much. So this was like a big change in my lifestyle. I had to play like for hours and hours every day, navigating these brand new novel 3D spaces. And after that, not only was I better at navigating real life mazes, but also my hippocampus got physically larger, a little bit larger.

25:27Michael Stevens:Maybe it needed more cells, more place cells. And that all happened by exercising my sense of direction in virtual spaces. The brain didn't distinguish between the real and the virtual.

25:40Hannah Fry:It doesn't care. And that's the thing. it's like all of this stuff about the eyes and the ears mismatching. You can get the opposite, by the way. You can get it where people feel VR sick, where the mismatch between the eyes and the ears, the ears isn't doing anything, but your eyes think something is coming, where you again feel really nauseous. But the brain, in terms of the way it's navigating, doesn't care. It's just, it's not, whether it's an imagined space or a real one, it's still firing in the same way. So you have these play cells, But the other thing that was probably growing inside your brain at the same time where you're doing all this practice is in the entorial cortex.

26:20Hannah Fry:So this is by the early 2000s. Everyone knows about play cells. But the question is, play cells are sort of like, here's a landmark. Here's an interesting red pin on the map. But it doesn't really tell us how you navigate between them. It doesn't say anything about distance or direction. So, some researchers looked in this other part of the brain, in the centurial cortex, and they did the same thing. They put a tiny little hat on a rat, looked to see when these neurons were firing. And they were firing as the rat was moving around, but it was a complete mess. Initially, it just looked like a total junk that didn't make any sense at all.

27:03Hannah Fry:And then they realised that maybe the room that they'd put the rat in was just too small. So, they made a much bigger room for this rat. and then realised that there is a second system that your brain is using. You have place cells, but you also have something called grid cells. The way that the mice's brain was mapping this space was almost like a chessboard. There is a neuron that fires every time that it goes through a white square. So if a rat runs from one side of the room to the other, this neuron will fire at regular intervals as it crosses the space. It's the same neuron. But it's not just black and white.

27:45Hannah Fry:You have many, many, many different grid cells. And the cells are sort of overlapping with one another. They're like spatial interval cells.

27:56Michael Stevens:It's not so much about the location. It's about, okay, you've covered three feet and another three feet and another three feet. are they sensitive to direction like one of them is just for east west motions and one's for north

28:09Hannah Fry:south no they end up being this tightly packed grid um and actually it's i mean i gave the chessboard analogy but they're actually hexagons they're actually extremely neatly packed hexagons oh and this is the thing is that normally biology is a mess right like you know biology is like blobs and gradients and squiggles and this was this this pre-programmed coordinate system that we found in mice and rats and has since been found within humans. And this is the way that we're navigating. If you only had play cells, it's the same as having a bunch of Polaroids of interesting places, but no idea how they connect together.

28:49Hannah Fry:And if you only had grid cells, you'd have a ruler and a compass, but no landmarks. And it's when you put those two together that you are able to navigate spaces.

28:59Michael Stevens:They're two different systems. Man, I wonder if... There are life forms that have only one and not the other. If they've got a more simple brain and then through evolution, some of us like rats have both.

29:16Hannah Fry:So one thing I do know is that I was working with some roboticists in actually a few years ago now, maybe like 22, 23. and they were trying to mimic this exact same system of grid cells and place cells because they think that it is the most efficient way to navigate through an environment.

29:37Michael Stevens:So we've got these two systems, place cells and grid cells, and they aren't just like given at birth. They are dynamic through your life. As I was talking about, it's been shown, not just by Minefield, but by lots of studies, that the more novel places you visit and navigate, the bigger, like the physically bigger the hippocampus in your brain gets. And I think one of the first and most famous places this was found was in the brains of London taxi cab drivers, right? This is a famous story because in order to be a licensed taxi cab driver in London, you need to be able to recall more than 20 ,000 streets and 100 ,000 landmarks all within a six mile radius of Charring Cross.

30:23Michael Stevens:There's a test you have to pass. And if you pass it, you have what they call the knowledge. Okay. The test is really so fun. It'll be something like you'll sit down at a desk and the instructor will say, okay, so you pick someone up on Essex Road and they say, I lost my cat. Help me find the cat. And you start driving east. Name each street you pass as you go. And so they have in their brains a map made of many different systems, probably, that corresponds to the reality of London, the city.

31:01Hannah Fry:I should say, actually, my ex-husband, who I'm still extremely really good friends with, he's doing this at the moment. He's learning the knowledge at the moment. So even though GPS now basically means you don't really need to know it all off by heart. I mean, the 1850s, sure, when London, this web of streets is basically impossible to navigate for anyone who didn't know them. Now with GPS, you don't need to, but there's still this real prestige that comes with it. There's also, I think, this idea that if somebody is willing to go through that, then they just have this professionalism and dedication to the job that you don't necessarily get with a ride-hailing app or whatever it might be.

31:50Michael Stevens:That's right. That's why I was so happy to learn that despite the fact that we all have GPS devices, the knowledge is still required to be a black cab driver in London.

32:02Hannah Fry:Yeah. I mean, they earn good money, right? Like it's a really good, well-paid job. You get to use the bus lanes in London. You can move around. You know, Black Cab is still like the fastest way to move around in London in a vehicle. There's a cabbie who I know really well, a very good friend of mine. And I have played this game with him before where I've shown him pictures of streets in London to see if he can work out what the street is see how quickly he can get the correct answer can i submit one too you absolutely you absolutely let me send you one okay one second let's go on street view okay i've got one here right what's this where is it should we uh should we reveal to the audience before i call him okay so i'm looking at your picture did you you went and got this on street view

32:55Michael Stevens:Yeah, this is taken from Street View and I'm like retro-doxing myself. These are the shops next to Carrick Court where I lived when I lived in London, directly across from Kennington Tube Station on Kennington Park Road, looking away from the station to the right of Carrick Court.

33:15Hannah Fry:Okay, all right, I'm going to give him a call. Hang on, let me send him the picture and let's give him a call. I'm going to give him no time to consider it. Hello? Hey. Hello. Did you see the image?

33:34Michael Stevens:Yes, I did.

33:35Hannah Fry:Go on, where do you think it is? Very quickly, straight away, I thought Brunswick Square. Right. Yeah, so you've got flats above shops, got trees around it. So that was my instant thought. But I don't know what all the given shops are. But looking at the shops, I think the Brunswick Square shops are maybe a little bit... A bit posher. Should I give you a clue? It's south of the river. Hang on. Hang on, Michael. London cabbies don't go south of the river. I know. That's why this is a really tough one. In that case, okay, my other stab in the dark is somewhere around Kennington, the Edithram Castle, something like that.

34:14Hannah Fry:Yeah. Hey, you're right. Wow. It's Kennington Park Road. just about to say okay then so is it very close to the station yes exactly it's exactly across from the station that's good that's really good rich there's there's a group of flats and some shops just across the road from the station there you go i'm a genius you are a genius amazing amazing rich thank you i appreciate it at least i haven't let you down no you absolutely haven't thank you very much i'll um i'll see you from my lift home later yeah cheers bye bye very handy that's really

34:52Michael Stevens:cool i mean even knowing the science behind it like i shouldn't be surprised but to see it happen in real life the actual human trick of it all is is just really makes me feel proud of our species

35:05Hannah Fry:i think this is the thing if you are if you haven't spent a lot of time in london and aren't familiar with the city, I think that you wouldn't necessarily appreciate just how phenomenally impressive that is. I mean, this city is vast, vast, and we're picking streets completely at random with no discernible characteristics on them. There's no sort of, no shop signs, no, you know, awnings with names on, just like a random building somewhere random in London. and he's getting it pretty much spot on straight away.

35:43Michael Stevens:Yeah, yeah, yeah, yeah. If you've never been there before, you might think, oh, well, it must be that each street has a very unique style of building.

35:50Hannah Fry:But it's much subtler than that, what he's able to do. Yeah, well, there you go. Incredible what the human mind can do. And we are going to be talking more about the human mind after the break and all other human body parts. Maybe not all of them, but a lot of them.

36:07Michael Stevens:Yes, all of them. Let's take that on as a challenge.

36:23Michael Stevens:This episode is brought to you by Cancer Research UK.

36:27Hannah Fry:Radiotherapy is over a century old, but it is still changing. Cancer Research UK helped lay the foundations of radiotherapy in the early 20th century and has driven progress ever since.

36:39Michael Stevens:Radiotherapy remains one of the cornerstones of cancer treatment today. Every year, millions of people worldwide benefit from Cancer Research UK's work to make it more precise.

36:50Hannah Fry:Scientists are still refining how radiotherapy is delivered. And one example is an experimental treatment called flash radiotherapy, which delivers radiation in fractions of a second, up to a thousand times faster than standard radiotherapy.

37:05Michael Stevens:And early studies suggest that speed could make a real difference. Flash radiotherapy may cause up to 50 % less damage to healthy cells.

37:14Hannah Fry:But scientists don't yet know why healthy cells seem to be spared, so Cancer Research UK are working to answer that. Understanding it could be key to reducing side effects in the future.

37:26Michael Stevens:For more information about Cancer Research UK, their research and breakthroughs, and how you can support them, Visit cancerresearchuk.org forward slash the rest is science.

38:02Michael Stevens:safe.

38:32Michael Stevens:Welcome back. We've been talking about how the human brain orients itself in space. And we've talked about place cells and grid cells and liquid in the ear. We've talked about landmarks in the eyes. But language also plays a role in how we understand three-dimensional space. So in 2011, a team from the Max Planck Institute of Psycholinguistics decided to compare two groups of children. OK, one group was from a tribe in Namibia and the other was just some Dutch children. OK, just some Dutch children, you know. To researchers, they're a dime a dozen. But what they did is they compared these two groups of children.

39:16Michael Stevens:Why? Because their languages were very different. OK, the children from the Netherlands, their language involved words like left, right, in front of and behind these relative terms. Right. Left is different if I'm facing this way or if I'm facing this way. My left is different than your left. They're relative to me. But in the language spoken by these Namibian children, there were no relative directions. Everything was absolute. They only had words for north, south, east, west. And it's not always the cardinal directions. Other tribes have languages that are absolute in direction that might be in reference to, say, a landmark.

39:54Michael Stevens:Like, is that mountain, you know, in front or behind the thing? Something like that. Anyway, in the experiment, they set up a table that, say, ran east-west, like a long table. And they lined up toys on this in a particular order. And they had the kids remember the order. And then they moved the table 90 degrees. and they asked the children to arrange the animals again in the same order they'd seen previously. And the Dutch children did it the way I think many of you listening would do it. They arranged them left to right in the same way. But the children from Namibia arranged them according to the cardinal directions.

40:35Michael Stevens:So instead of having everything go to the left, to the left, to the left, they said, well, no, no, no, the toys are now going to have to go the other way on the table because they used to all be facing south. And so I will keep them facing south because that's the way they conceived of space and objects in it.

40:51Hannah Fry:That is so fascinating. So you end up with all these toys squished along the short run of the table.

40:58Michael Stevens:Exactly. To the Dutch children, what mattered was who was to the left and the right of a target toy. But to the Namibian children, what mattered was which way the animals had been facing the entire time. So instead of being left to right, but now facing, say, west, they were all still facing south and they didn't even fit on the table. So what mattered was, what was relevant was the cardinal absolute directions.

41:23Hannah Fry:So, OK, right. Two things. First off, I do wonder if you had a spider on your leg, right? Because you sort of say, I don't know, to a Dutch child, there's a spider on your left leg and you sort of brush it off and it's fine. But if you're with a Namibian children, you'd be like, it's on your northwest leg. No, don't turn around. Now it's your southeast leg.

41:43Michael Stevens:That's right. That's exactly right. And it's like a superpower. It sounds that way to us because we are just, I mean, especially with GPS, I really don't need to know which way north is. I can just get as lost as I want and then my phone will tell me where to go. Now, it is, however, true that if you take a person who has an absolute direction language only and you spin them around and make them dizzy, they do lose track of which way north is, just like we do. Whereas if you spun me around, I would not forget which way left was.

42:15Hannah Fry:No, true. But you would never know which way north was.

42:19Michael Stevens:But I never knew which way north was.

42:21Hannah Fry:That's right. Exactly. I mean, that really demonstrates that it's a cognitive effort then, that they're keeping track from the last time they knew what north was rather than it's not a magical trick. It is something that's a sort of decision, as it were, something that is a direct consequence of the language. It's nice. It's a really nice study.

42:43Michael Stevens:Just as we've learned from studies on place cells and grid cells, it is about memory. They remember and they keep even a non-conscious memory of how they have moved and what that would mean for the direction of north. Whereas those of us whose culture does not pay attention to cardinal directions in the same way, we don't have to.

43:02Hannah Fry:I do wonder though, okay, so that's sort of where things are in relation to each other. I also wonder about, we were talking about proprioception a bit before the break, but I also wonder about the map that you have of your own body, because presumably you're not born with that, right?

43:21Michael Stevens:So how we orient ourselves in space is very culturally dependent. But what isn't is where we put ourselves in our bodies. Going back to the experiment we did at the very beginning of this podcast, point to yourself. Where are you pointing? There's generally only two places people point, regardless of their culture, their age, their gender, their life experiences, they point either to the head or to the chest.

43:58Hannah Fry:I wonder what the ratio was in our comments. I wonder. We'll do a little study. Yeah. I can barely imagine saying point to yourself. It sort of doesn't feel right to me to point to your head.

44:09Michael Stevens:Yeah, point to yourself. And I want to talk about this. And I don't have a big whiz bang insight to give because a lot of this is research that I did years ago for an episode about like, where is your seat of consciousness? Where do you think it is? Where does it feel like it is? And I didn't know enough about consciousness to find an answer. So I never made the episode, but I wanted to share some of the cool things I found on this journey. And one of these days it'll make it into an episode. So as it turns out, like where people point when you ask them to point to themselves depends almost entirely on context.

44:54Michael Stevens:So, for example, there was a great study that was done. I love the experimental design here. They had people go into a room where there was a pole from the floor to the ceiling and it had this arrow on it. and you could move the arrow up and down. And they told people to just move the arrow until it pointed at them. And as it turns out, if they walk into the room and the arrow is down on the ground at the bottom of the pole, they'll pull it up until it reaches their chest and they'll stop and they'll say, there, I did it. But if you begin with the arrow near the top of the pole when they enter the room, they'll only pull it down to their face.

45:35Hannah Fry:So it's like anchoring, but for arrows and where you are.

45:39Michael Stevens:Yes, where you think you are in your body is very much dependent on how it's been anchored, right? They could also have a person go in with a blindfold on. And if you have a blindfold on, you're a little bit more likely to have it point at your chest than at your face. If you have a blindfold off, you are much more likely to point it at your eyes, at your face. But this question of where you are in your body has a very specific target in psychology. It's called the ego center. And the ego center is the name for where I believe the very middle, the center of myself is. And you can ask people this and they all understand it, right?

46:21Michael Stevens:They all understand like, oh, yeah, sure. Like my life is basically a POV video game. Where am I seeing the world from? So the eyes become this really dominant sense for determining where we think that we are. And interestingly, all the sensory holes influence it. Because if you give someone like a map of the body and you tell them to pinpoint exactly where they think they are, it's almost always a place right in between the eyes, just a little bit back, just a few inches back. Or maybe even like just like a centimeter behind the eyes in between. Like your conscious center sits just behind your eyes.

47:01Michael Stevens:That's right. Like if you're some kind of little rat driving your body around, we think that we are that rat sitting right behind the eyes. But people who have been blind since birth place their ego center in between the eyes, but much further back, almost in the middle of the head, right in between the ears. Because sight hasn't dominated and put in its influence on, no, no, no, you're right here. You're up here where you see things.

47:25Hannah Fry:What about deaf people? Because I sort of wonder, I mean, there's a lot for people who have, you know, full hearing, full vision. There's a lot going on in your head, right? But I can imagine that for people who are deaf and who use sign language, like their communication center is their hands, right? Does that end up changing things?

47:46Michael Stevens:In the congenitally deaf and blind, there's very little information because a person with those conditions is often it's just hard to even ask them, like, where is yourself? But there are a lot of just from like anecdotal reading online, there's a lot of discussion of tactile thoughts, dreams being tactile. and what I haven't been able to find is any real confirmation that a deaf and blind person from birth pictures themselves, say, in their fingers or in their lips or somewhere where there's a lot of touch information coming in. I think that even without vision and hearing, we still have other things that make our head a focus like the breathing and taste.

48:40Michael Stevens:It all comes in through stuff up here. And it also can move around a lot. Our limbs can also move around a lot. But the trunk, the torso is hypothesized to be an extremely universal anchor point for where we say we are because it just it doesn't move independently. I can't move my torso without also moving my arms. My legs and arms and my head can be in weird positions, but my body is always that central point, which also probably explains why so many of us point to the chest for the self. And of course, there's also the fact that when you feel things deeply, you often feel it in your gut and in your heart.

49:29Michael Stevens:Your heart speeds up. And this isn't just about emotions. It's also about like what would ancient people think? Aristotle believed that all of our memories and our thoughts were happening in the heart. Well, because they thought they thought the brain was there to sort of cool down the body, right? Cool down the blood. That's right. They thought that the brain's only purpose was to cool down the blood. The heart was clearly more important because when you looked inside a human body, you saw all of these veins and arteries that went everywhere. Clearly, those were the marionette strings that the heart pulled to make us move.

50:04Michael Stevens:It was clearly the seat of consciousness, and this is where we are. So where you think you are in your body isn't just about your sensory holes. It's also about your culture and what you know.

50:16Hannah Fry:So I also wonder, though, then that just tracing that backwards, I wonder whether you would get less people saying, I am here, you know, sort of the seat of my ego is right in where my brain is. If you rewound the clock and ask the ancient Greeks, would they have all said in the chest? Yeah. Yeah.

50:37Michael Stevens:And the ancient Egyptians as well. And so at some point there was a change where we switched from the heart is where my thinking happens to the brain is where my thinking happens. And I mean, a lot of this is I don't have a point that I've reached with this research, but I've looked a lot into the feeling of mental exhaustion. Like if you if you're thinking a lot, doesn't it kind of feel like your head is tired? So why didn't ancient people say, man, when I think a lot, my head is tired because we don't have nerves in our brain, actually. Generally, if you've been doing a lot of cognitive work, your head area will feel tired because you've been using your eyes a lot.

51:26Michael Stevens:And you haven't been using the other parts of your body a lot. but to me it's still a bit of a mystery why the brain was so unimportant when it came to the location of the self in the body to the ancients i do sort of wonder though because

51:43Hannah Fry:as you said you don't have nerve endings in your brain i mean this is the reason why you can have people who have brain surgery while they're still awake right um i i sort of wonder whether you feel like your brain is tired because we now know that that is where everything is happening how much it's really difficult to disentangle one from the other. One thing I did think that was really interesting that you said there is that it's interesting how, as you said, the eyes, this like real magnetic center where so much information comes in from them that you are, it's almost impossible not to imagine that your consciousness is centered near them.

52:20Hannah Fry:But then at the same time, it's interesting how you said that people put their ego, their ego center between the eyes where there isn't an eye, you know?

52:29Michael Stevens:That's right. Yes. Okay. So yes, this reminds me, I think I've told you this before, but I want everyone to hear about the Cyclops effect. If you ask a child who is like, I don't know, two years old, like young enough to look through a cardboard tube or to look inside a tube, here's like a tube, okay? They will put the tube right in between their eyes and they won't be able to look inside of it. And that's because, of course, our brain takes both of the images from both of our eyes and combines them into one image right in between the eyes. And as an adult, we learn that, like, yes, that's how it feels, but I have two eyes.

53:09Michael Stevens:And so around the age of, like, three, three and a half, kids start to, when asked to look inside a tube, they put it up to just one eye. They tend to keep both eyes open, though.

53:22Hannah Fry:Adorable. Adorable little cyclops.

53:24Michael Stevens:It's really adorable. And this is honestly another reason I haven't done a video on this is that I lost that window with my daughter. I needed to do the experiment with her to get good footage of it happening. And now she's too old. She knows that she has two eyes and she doesn't just like vision isn't just coming out of the middle between them. and there's one video on YouTube where a parent asks their kids and the kids do it. They like stick the thing right in between their eyes and get confused about why they can't see inside of it but I can't use that footage because it's like someone else's children but it's a phenomenal illustration of this effect.

54:00Michael Stevens:We call it the Cyclops effect.

54:02Hannah Fry:It sort of feels like this is the perfect opportunity if you happen to know or live with a small person under the age of three see if you can get a video of them doing Cyclops Effect and send it in to us.

54:12Michael Stevens:Yes, yes, please. And of course, won't use anything without a lot of discussion. But it's just hilarious to see it happen. And there's just literally one video on YouTube. And it is so it's like so funny, but also really deep about how we understand our bodies that it takes a while to learn that you have two eyes.

54:32Hannah Fry:Well, OK, so here's the thing. You just said now you're an adult, you know that you have two eyes. But the thing is, is that I think that, you know it intellectually but I think your body actually often defaults to thinking that you have one eye so the really nice way to do this is if you get it like a little roll of paper and you hold it up to say your right eye and then you hold your your left hand up right next to it and keep both of your eyes open what will happen very quickly I mean initially your brain's like what's going on but very quickly it then looks like you've got a hole in your hand right like your brain is essentially combining those two images as though you have one eye and i think what's really nice about this is that actually when you're walking around the reason why your brain is doing this is because you need one eye for walking effectively you know your your little two-year-old child who's um a cute little cyclops they are biologically perfect walkers We only switch to one eye when we're using tools.

55:38Hannah Fry:Yeah. When you're being much more precise and specific that you, you know, the distance between your eyes starts to matter. So, you know, these little babies, they're great at walking. Terrible hunters. Terrible at using tools.

55:51Michael Stevens:And not to go on about this forever, but if you want to ruin the effect of the hole in the hand, put a photograph of a person's face on your hand. because the brain privileges faces when it comes to combining two different images from each eye. And there's actually another name for this, which is the Cheshire cat effect, where the face is so important that it stays on top. And it might fade a little bit, but the eyes and the mouth will always be there. The brain doesn't combine them with what the other eye is getting.

56:26Hannah Fry:I didn't know that. I didn't know that. Every day with you, Michael, Every day is a school day.

56:31Michael Stevens:So the last thing I wanted to say is that I've been trying to tease out the contexts that affect why sometimes we point to the face or we think of the face as the self and why sometimes we don't. For example, if someone said, oh, hey, Michael, can I get a picture of you? If I gave them a photo of my knee, they would be very confused. confused. If I gave them a picture of my entire body from the neck down, they would say, I'm sorry, this is not what we wanted. And I'd be like, what do you mean? That's 90 % of my body's surface area. Like that's the, that's me. They'd be like, no, no, no. We just wanted your face.

57:12Michael Stevens:And I'm like, but my face is such a small part of my body. How can that be me? At the same time though, when we're talking with each other, we won't just reference the face with gestures to refer to ourselves. Like if I said something like, and you know what? She took my car. I point to the chest. It would be very weird to say she took my car. If I pointed to my face, I'm pointing to my eyes right now. Even though in the visual world of photographs, my face is me. In the world of discourse and talking, I am my chest. And I'm not exactly sure why that all is. The best explanation for the chest gesture for myself, for me, comes from Kinsey Cooperrider, who said that When you're talking, any gesture you make moves the person's eye unless it's like a very general gesture.

58:18Michael Stevens:So if I say my book, I'll point to my chest because it doesn't distract you enough as if I like pointed to my shin. You'd be like, oh, why is he pointing to his shin? And you'd have to move your head. But if I point to my chest or I just put my hand on my chest, I'm emphasizing the word mine without distracting your eye. If I pointed to my head and I said, my book, you'd be like, oh, why is he pointing to his temple or his cheek? And it would distract. But the chest is like a vague enough but not far enough away place that it just emphasizes the word. Anyway, it's very mysterious.

58:54Hannah Fry:It is very mysterious. This is why I like it so much. I like to think that part of this is potentially cultural. And maybe today, Michael, we can make a shift. Maybe we can make it so that everybody from now on, whenever they say something, they go, what about me? And just directly points to the end. Yeah, yeah, yeah, yeah.

59:14Michael Stevens:So I want to throw in one more thing that I've been I've been researching, and that's where we knock on doors. When you go up to a door and you need to knock on it, we usually knock like about here at the height of like the shoulder or the or the eye somewhere in between there. even though our hand, you know, hangs down at our waist or something. Why is that? Is that a cross-culturally true thing? Because you could come up to a door and knock at the bottom of the door. But we don't do that. We knock about where our voice would be coming out if we were to be talking to the person. We knock kind of where we might be looking if we were looking at the person.

59:53Michael Stevens:Is that what motivates all of us to knock on doors where we do rather than like I could knock at it down at my waist or right where my hand happened to be. But no, we like put our hand up and we knock where our mouth would be. Maybe.

1:00:07Hannah Fry:Maybe. Maybe. I mean, there's a bit of me that wonders whether it's just because it's sort of the physics of the angles of your elbow, you know, that it's like it's slightly easier.

1:00:19Michael Stevens:Sure. Maybe it's just easier to control the power and the volume of your knock in that position.

1:00:26Hannah Fry:But it does feel like at your kind of communication center. It does come back to everything that you're describing that you've got. It's almost like your center of mass, but it's like the center of me. Right. The ego center.

1:00:42Michael Stevens:Exactly. Exactly. So the point is, this is a lot of kind of funny stuff where there aren't a lot of clear answers. And yet, I feel like we know less about where the self resides in the body than we do how we understand where our bodies are in space.

1:01:01Hannah Fry:Which is something that happens quite a lot. I mean, if you think about we have explored the galaxy, the solar system, and yet still the Mariana Trench is a rare anomaly in our understanding of the ocean floor. I know.

1:01:17Michael Stevens:We know more about the surface of the moon or of Neptune than we do the ocean floor. So I call this the proximity paradox. It seems like the closer something is, the harder it is to really look at it and understand it. And so when it comes to the question of where are you, finding where you are on the earth, easy peasy.

1:01:37Hannah Fry:Finding where you are in a room, a bit harder. Finding where you are in your body, genuine mystery. Yeah. Is that even a sensible question? And this is what I like about this program, right? You do a program on where are you. You're not going to get this kind of stuff on other science podcasts, are you?

1:01:55Michael Stevens:No, no, you're going to leave. You're not going to leave going, oh, that's where I am. You're going to leave going, what does where mean and who am I?

1:02:05Hannah Fry:I no longer understand any of the things that I thought I could take for granted. Well, okay, that I think is a good point to leave it for this episode. Make sure that you are following the rest of science wherever you get or listen to your podcast, or you can like and subscribe on YouTube if you would like to watch us.

1:02:23Michael Stevens:And if you'd like to ask us any questions, which we might just answer on a Field Notes episode in the future, you can send that question to the rest is science at goal hanger dot com.

1:02:32Hannah Fry:See you next time.