You (Don't) Know Where You Are

If someone asked you to point to yourself, where would you point? Your chest? Your head? Somewhere just behind your eyes? Where are you? In this episode, Professor Hannah Fry and VSauce’s Michael Stevens explore how the brain maps and understands out location, from the inner ear fluid that tells us which way is up, to the grid and place cells that build a kind of internal GPS. But how do London taxi drivers rewire their brains to memorise entire cities when the rest of us can’t? How does language change the way we orient in space? And what happens when your senses disagree about your where in the world you are? Moving from avalanches and virtual reality to ancient philosophy and modern neuroscience, Hannah and Michael move from how to find ourselves on a map to how locating the “self” inside the body may be one of the deepest mysteries in science. Why did Aristotle believe the self lived in the heart instead of the head? If we’re asked to find the self where do we point? What does it mean to say that you are somewhere…at all? ------------------- For more information about Cancer Research UK, their research, breakthroughs and how you can support them, visit ⁠⁠https://cancerresearchuk.org/restisscience⁠⁠. Cancer Research UK is a registered charity in England and Wales (1089464), Scotland (SC041666), the Isle of Man (1103) and Jersey (247). A company limited by guarantee. Registered company in England and Wales (4325234) and the Isle of Man (5713F). Registered address: 2 Redman Place, London, E20 1JQ. ------------------- Find The Rest Is Science all over the internet by ⁠⁠clicking here.⁠⁠ ------------------- Video Producer: Adam Thornton + Oli Oakley Video & Social: Bex Tyrrell Researcher: Hannah Dodd-Vastiau Assistant Producer: Imee Marriott Senior Producer: Lauren Armstrong-Carter Head Of Digital: Samuel Oakley Exec Producer: Neil Fearn Learn more about your ad choices. Visit podcastchoices.com/adchoices

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Michael Stevens?

  Welcome to The Rest Is Science. I'm Michael Stevens.

• 0:02Hannah Fry?

  And I'm Hannah Fry.

• 0:03Michael Stevens?

  And you are listening. I don't know your name, but I want you to follow along. And Hannah, you too, with a little experiment. We're starting right off the bat with an experiment. All right, those of you listening at home, Hannah, I'm gonna do this too. Everyone, point at your forehead. Okay, are you pointing at your forehead? Good. Now point to your chest.

• 0:24Michael Stevens?

  Now point at your knees. Point at your nose. Now point at your shoulders. Now point at yourself. Where are you pointing?

• 0:36Hannah Fry?

  Same place as chest.

• 0:38Michael Stevens?

  Same place as chest, interesting. Down in the comments below, let us know where you are pointing. Did you do the chest, the belly, go back up to the face? Where is the unique seat of yourself? Where are you? Where am I? How do we know any of this stuff? Where am I in my body? Where am I in the universe? Well, that's what we're talking about today.

• 0:58Hannah Fry?

  And this is gonna take two parts, really. I think the first part is gonna be a sort of a standard, straightforward answer to this question, as I guess ordinary humans would ask it. Where in the world are you? How do you work out where you are? And then in the second part, we're gonna delve deep into Michael's, I mean, the wonders of your mind, Michael, of what does it mean to say you are where you are? Is that fair?

• 1:25Michael Stevens?

  That's right, Hannah. And as it turns out, both of those questions are related in a boring way, but they're unrelated in a fascinating way.

• 1:35Hannah Fry?

  There we go. That's the hook and tease for this episode right there.

• 1:45Michael Stevens?

  This episode is brought to you by Cancer Research UK.

• 1:48Hannah Fry?

  The word cancer comes from the Greek kakinos, meaning crab. And Hippocrates used that word because tumors can spread out like crabs' legs.

• 1:58Michael Stevens?

  For a long time, cancer was poorly understood. And so I think because of that, it was almost scarier, and people didn't even say its name. But what science has done since is replace uncertainty with understanding.

• 2:10Hannah Fry?

  But that understanding is an instant because cancer isn't just one disease. It's it's hundreds of different diseases, each behaving differently, depending on where it is and its genes. And that complexity is why progress in cancer research can feel like it's slow. But step by step, research is saving and improving lives.

• 2:30Michael Stevens?

  And that's why Cancer Research UK, the world's largest charitable funder of cancer research, supports work across more than 200 types of cancer, from the tiny changes inside cells that start the disease to better ways to spot it earlier and treat it more precisely.

• 2:47Hannah Fry?

  For more information about Cancer Research UK, their research and breakthroughs, and how you can support them, visit cancerresearchuk.org/the rest is science.

• 2:57Speaker 02

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• 3:40Speaker 02

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• 4:28Speaker 03

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• 5:04Hannah Fry?

  All right, well, let's start up with, I mean, you know, you're sitting in your chair. You know where you are in the room around you. But I want to know, how do you know? How do you know which way is up? Because there are times when actually it's extremely difficult to work it out. People who get stuck in avalanches report not knowing which way the ground is, which way the sky is. When you are sort of, when you don't have any visual information, when the usual things that you use as cues are stripped away, it's incredibly difficult to orient yourself.

• 5:38Michael Stevens?

  I've heard that and I love thinking about it because it's so frightening to be like buried in snow, not knowing which way is up, not knowing which way to like crawl out. And I have in, while I'm laying in bed, thinking of how I would survive certain things, I've come up with my strategy. Can I tell you what it is?

• 5:56Hannah Fry?

  Yeah, go ahead.

• 5:57Michael Stevens?

  It would be to drool.

• 5:59Hannah Fry?

  Yes, that is, that's the actual trick.

• 6:01Michael Stevens?

  Is that a real thing that you should do?

• 6:02Hannah Fry?

  That's the real trick is to spit and see which way the saliva goes, yeah.

• 6:05Michael Stevens?

  And then you know which way down is.

• 6:07Hannah Fry?

  Exactly. Right, Michael, what other scenarios are you imagining in your mind at nighttime that you're trying to survive?

• 6:15Michael Stevens?

  A lot of illegal stuff, like.

• 6:19Michael Stevens?

  I'd often, I found this very relaxing to imagine how I could get to and deface the Hollywood sign without being stopped or caught.

• 6:26Hannah Fry?

  Okay.

• 6:27Michael Stevens?

  Just like imagining going up the hill and the steps I would take and what I would wear and then suddenly I'd be asleep. It was a great, it was like rather than counting sheep, I committed crimes.

• 6:38Hannah Fry?

  That would be your imaginary fantasy. Okay, did you have one for if you were surfing and you got wiped out on a surfboard and then working out which way to swim?

• 6:49Michael Stevens?

  Okay, yeah, here it's, it would be, it would be bubbles. I would, I would exhale bubbles and watch which way they went.

• 6:54Hannah Fry?

  I, I like, I have to say that I've never, well, I mean, I've, I've surfed, but I don't think you can really call it surfing. But like, is that something that happens that you're underwater for long enough that you could consciously sort of say, I'm going to blow a bubble and see which direction it moves in?

• 7:10Michael Stevens?

  That's what I'm wondering too. Cause I think in both of these examples, if you haven't been in these scenarios, you might say, how can you not know which way is up? You'll feel it. But when you are packed into avalanche snow, or when you are disoriented, you've spiraled, you're surrounded by water, you're buoyant everywhere, it is not immediately obvious.

• 7:33Hannah Fry?

  So there are other scenarios when this kind of total confusion of, of which way is up, which direction you're in, happens slightly more unusually in the microgravity of, of the International Space Station, or, you know, in, in space rockets in general. So, because, okay, so one of the ways that you're anchoring yourself is, is of course a vision, looking at which way gravity is working, where the horizon is and so on. But you also have inside your ear, in this sort of semi-circular canals, these incredibly intricate design. It's essentially like a biological accelerometer, which can tell which way you're moving and which way you are, you're oriented. But when you're in

• 8:18Hannah Fry?

  microgravity, the system which relies on, on gravity pulling it downwards, end up floating freely and they start signaling to your brain that you are Constantly falling and flailing. But your eyes meanwhile see this very static tab in. So so your brain panics because of course for the whole history of our evolution. The only situations you'd be in when your eyes didn't match what your ears were telling you would be if you'd been poisoned.

• 8:47Michael Stevens?

  Or or if you were falling, if you were in free fall.

• 8:50Hannah Fry?

  True, if you were in free fall, yeah.

• 8:52Michael Stevens?

  Both of them are bad scenarios.

• 8:53Hannah Fry?

  Very, I would say very bad. If you're if you're falling long enough for you to uh for your brain to register that there's a mismatch. In prehistoric times, I would say overall bad. I would say things are not looking good for you or your future offspring. But uh the thing is, is that it sort of assumes that it's this uh that you've been you you've you've had some kind of toxin. So it kind of pulls this emergency cord, getting you to vomit.

• 9:20Michael Stevens?

  The puking is a really good thing, like your body is trying its best to say, look, if I've been poisoned. Let me get out what's in the stomach. It might have been something I just ate. So if you're dizzy, if you're in the vomit rocket, like. Throwing up is is your body's like primitive way of fixing what we invented.

• 9:39Hannah Fry?

  Right, totally. And the thing is, there is like a lower level of this, people who are carsick or travel sick in general. Your body is feeling the physical sensation of this car moving, accelerating, braking, you know, moving around. But it's especially prevalent if you're reading or looking at your phone, you're watching something that's static. And and your body is like, these two things don't mesh time to feel sick. Which is why the the trick to if you feel carsick is to look out the window, sort of connect yourself with the outside, to connect yourself with the motion. Anyway, most people feel a little bit of sick when they um end up in the space station. But there was one guy, a senator, who uh flew to to space on the um on the space shuttle.

• 10:23Hannah Fry?

  Called Jake Garn and he really struggled, like a lot. So he vomited so much that NASA decided to they should set a new metric. Of one point O guns is like the limit of how much a human can reasonably vomit when when they experience this situation. Most people get to naught point one guns, by the way.

• 10:48Michael Stevens?

  How specific is it? Like, could I use it to measure my flu symptoms? Oh, man, I'm at half a gone.

• 10:54Hannah Fry?

  I don't think so. I think it was just, to be honest, them throwing shade at this pathetic senator who was too much of a weakling to be an astronaut.

• 11:01Michael Stevens?

  If I was him, I would not see it as shade. I would see it as an honor. You know, I'm down in the history books. I'm podcast fodder now. I'm a measure of vomit amount. Like, at least that's something.

• 11:12Hannah Fry?

  That's true. It's gonna live on beyond, beyond you, beyond your lifetime. And this whole thing about this mismatch between your, your ears and your eyes, your ears in general, working out which way you're up. Um, there's something really dangerous that can happen to pilots with this because inside your ear, the way that this works partly is about fluid moving through your ear through these little canals. Um, and that means that if you enter into a really long, steady bank, as you would if you were flying an aircraft, if you're sort of like doing a really long bank. What can happen is that the fluid can, can eventually catch up with the, the canal walls, which means your brain then thinks that you're level, even though you're still banking.

• 11:56Hannah Fry?

  So what has happened in the past, this is called the graveyard spin, instantly, is that when, when a pilot finally levels the plane to get it straight, the fluid shifts again, which means that the, the, the brain thinks that actually you've, you're banking in the opposite direction. It thought you were banking and you've gone straight and it thinks you were straight and now you're banking in the opposite direction. This was a really big problem in, in the RAF. Um, that pilots would have to overrule their body believing that they were banking. Because otherwise, what they would do is correct for this sort of phantom turn and then re-enter the original spin. And then they end up spiraling downwards. They feel like they're perfectly level.

• 12:40Hannah Fry?

  Um, but, but then of course can end up getting themselves in a position that they can't then pull out of.

• 12:46Michael Stevens?

  Wow, that's a great example of why your instruments are so important in a plane. And why pilots need to learn how to do instrument-only flying. Like, literally, with the windshields blacked out, you should be able to fly the plane, take it off, land it. Because the human body is just, yeah, it's, it, it acclimates to the bank and it's not built for that kind of thing. What a great example of that, because I always. Think it would be so scary to not be able to see if I was a pilot. And yet, in reality, the instruments know better than you because your instrument did not evolve for slow aircraft banking.

• 13:25Hannah Fry?

  Yeah, I mean, your body almost never lies to you. When it is strapped into a hunk of metal and flying through the sky at like crazy altitudes and pulling strange maneuvers, your body is gonna lie to you. Your body is gonna lie to you.

• 13:42Michael Stevens?

  Did you know, speaking of the vestibular system and fluid in the ear giving us a sense of balance, I have top shelf vertigo.

• 13:50Hannah Fry?

  Do you?

• 13:51Michael Stevens?

  Yes. So what that means is if I look up, like if I'm looking at the top shelf of something, usually it's when I'm looking up at a skyscraper, I'll go ahead and do it. When I look up like that and I come back down, I get very dizzy.

• 14:03Hannah Fry?

  Do you?

• 14:04Michael Stevens?

  I don't know which way is up. And the funny thing that this causes is that if I'm drinking out of a can and I'm walking and I'm finishing the can, I have to go like way up high. Then I come back down and I stagger around and stumble like I'm drunk. So it looks like I'm drinking beer and I'm really drunk for only about like two seconds and then and then it normalizes. But it means that I just cannot, if I'm riding a bike and I look up at something, I'm gonna crash. So I have to just like never look up at things when I'm, when I'm, when I'm, you know, walking around a new city and everyone's like, wow, look at that skyscraper. I'm like, I'll Google it. I can't, I can't look up at it because when I come back down, I'll fall over.

• 14:48Hannah Fry?

  Have you heard of straws? Just a, just a, just a little suggestion there, boy.

• 14:52Michael Stevens?

  Oh, man, I have heard of straws, but I never thought to connect the two.

• 14:56Hannah Fry?

  So have you worked out why this, why this is? I mean, it is, you have these like 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? What, so have you worked out why this might be?

• 15:11Michael 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 paroxysmal positional vertigo.

• 15:25Hannah Fry?

  Top shelf is better, though. Top shelf makes it sound like you get it every time you go to a supermarket.

• 15:31Hannah Fry?

  Reach for the beans.

• 15:32Michael 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.

• 15:54Hannah 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.

• 16:15Michael Stevens?

  Yeah.

• 16:16Hannah Fry?

  So I guess, yeah, if you've got these subtle, subtle things, either in the physical structure of your system, or the way that your brain's interpreting it.

• 16:24Michael 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 gonna fall. Let's just fall over.

• 16:51Hannah Fry?

  Have you ever been on one of those, NASA use them as training devices, I think, where they put you essentially in the center of a gyroscope and spin you around. And so you can move in all directions.

• 17:01Michael Stevens?

  I did that at space camp. 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.

• 17:12Hannah Fry?

  Wait, as a kid?

• 17:13Michael Stevens?

  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.

• 17:30Hannah 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. You're you're you 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. Thing is, this can go wrong, right? So in the nineteen seventies, there was this man called Ian Waterman. And he had this very rare viral infection.

• 18:09Hannah Fry?

  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. But he describes how he woke up one day and he literally felt like he was a head floating on a pillow. 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.

• 18:50Hannah Fry?

  If he closed his eyes, he he did not know what position his body was in, had no idea at all. The crazy thing about this story with Ian Waterman is that because he could still see his body. He was able to 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.

• 19:18Michael Stevens?

  By watching.

• 19:19Hannah Fry?

  By watching it.

• 19:20Michael Stevens?

  Wow.

• 19:21Hannah Fry?

  Yeah.

• 19:21Michael Stevens?

  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, um, that sucks. But what a phenomenal experiment and experience.

• 19:48Hannah Fry?

  Totally. So that's, 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.

• 20:00Michael Stevens?

  In the environment.

• 20:01Hannah Fry?

  Exactly. There, I just, some of my favorite 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, chunk of their brain.

• 20:26Michael Stevens?

  Yeah.

• 20:27Hannah Fry?

  And there was one patient in particular who had a section of his hippocampus removed. And at that point, this, this, um, this, this patient could no longer recognize hospital staff. So it's sort of his, some of his memory had been damaged, but he also could no longer find his way to the bathroom.

• 20:44Michael Stevens?

  Huh.

• 20:45Hannah Fry?

  And this was the point where people, um, realized that this, there's this connection, right? He couldn't, he couldn't recall day to day events, um, of his hospital life. And, and this was 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, is down to us remembering where we've been, essentially. In the 1970s then, a little while later, there's, um, a guy called John O'Keefe at UCL, my, um, my animata. And, um, he has worked out this way. He's basically invented a very precise little hat

• 21:26Hannah Fry?

  that you can put on a rat's head. Um, and this will measure the electrical signal from one neuron at a time inside this rat's brain.

• 21:35Michael Stevens?

  Wow.

• 21:35Hannah Fry?

  It's extremely precise, okay? It's like the tiny, tiny, tiny little wire was going into the rat's brain.

• 21:40Michael Stevens?

  Into one brain cell, one neuron. Wow.

• 21:44Hannah Fry?

  One brain cell, exactly. And this is the 1970s, so he hasn't got it rigged up to anything particularly fancy. It's just to 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, 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.

• 22:18Michael Stevens?

  Huh.

• 22:19Hannah Fry?

  So John keeps 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 know, um, he rotated the walls and this cell still fired in the exact same spot in the room. And as he rotated the walls, the firing field rotated with them. It's the way the rat was orienting itself. Is the right word?

• 22:52Michael Stevens?

  Orienting? Orientating sounds good too, though.

• 22:56Hannah Fry?

  I don't know. It was working out where it was relative to the walls and that's what this neuron was doing.

• 23:03Michael Stevens?

  And this was relative to the walls? So what about in the dark?

• 23:07Hannah Fry?

  In the dark, it could still tell roughly where it was in the space. And the neuron still fired in exactly the same spot.

• 23:16Michael Stevens?

  Wow.

• 23:17Hannah Fry?

  So it's like this, it's almost like, you know, the red pin you get on Google Maps.

• 23:21Michael Stevens?

  Yeah.

• 23:21Hannah Fry?

  Basically like this, this neuron is firing at that, that moment. Um, 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. Alice in Wonderlanding it, right?

• 23:39Michael Stevens?

  Yeah.

• 23:39Hannah Fry?

  Um, 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.

• 23:54Michael Stevens?

  Wow.

• 23:55Hannah Fry?

  Isn't that cool?

• 23:56Michael Stevens?

  That's such a cool experimental design. Stretch the room and you've stretched.

• 24:02Michael Stevens?

  The the mental map.

• 24:04Hannah Fry?

  Exactly, which means that our internal maps, they treat rooms like balloons, right? Rather than that can stretch and that can bend, then it we're not taking direct, exact measurements.

• 24:15Michael Stevens?

  It's like we didn't mean for this to happen, but life forms already are prepared to travel through spacetime with all of its curvatures and stretching.

• 24:25Hannah Fry?

  I mean, life forms live in spacetime, so why not?

• 24:27Michael Stevens?

  Why not? Bring on the nearly as fast as light vehicles, we're ready.

• 24:32Hannah Fry?

  So by now, we have these really clear understandings of they're called place cells. That's what they've been named. There's um, there's some amazing experiments where they have mice. So you put on this the same kind of hat, you pop it on a little mouse. And you you 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 is in virtual reality. And then you let the mouse navigate through Quake two video game.

• 25:18Michael Stevens?

  You are describing like a literal mouse.

• 25:22Hannah Fry?

  Yes.

• 25:23Michael Stevens?

  Or a computer. Like the old ball in the mouse, right? For a computer, this is this is the same ball, but there's an literal mouse on top of it.

• 25:33Hannah Fry?

  Literal mouse on top of who's controlling the direction. That's exactly what I'm describing, exactly what I'm describing.

• 25:41Hannah Fry?

  But the key point about this is that the mouse believes is in reality, I guess, is sort of trying to navigate to a drink of water down one end of one corridor or whatever it might be.

• 25:52Hannah Fry?

  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.

• 26:01Michael Stevens?

  Ah.

• 26:02Hannah Fry?

  You still get this same pattern that one neuron warfire in one particular place, like a red pin on a Google Maps. In this in this virtual imaginary space.

• 26:13Michael 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

• 26:52Michael Stevens?

  my hippocampus got physically larger, a little bit larger. 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.

• 27:10Hannah Fry?

  It doesn't care. And that's the thing. It's like that all of this stuff about the eyes and the ears mismatching. You can get the opposite, by the way. You can get it where you people feel VR sick, where the mismatch between the eyes and the ears, the ears isn't doing anything, but your 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 this, you have these place 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. So this is by the early 2000s, everyone knows about

• 27:55Hannah Fry?

  place cells. But the question is, place cells are sort of like, here's a landmark, here's an interesting, 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 um some researchers looked in this other part of the brain, in this entor際 cortex, and they did the same thing. They put a tiny little hat on a rat, looked to see when this, when these neurons were firing. And uh 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. And then they realized that maybe the room that they'd put the rat in was just too small. So they they made

• 28:39Hannah Fry?

  a much bigger room for this rat, and then realized 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 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 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 you have not not, it's not just black and white. You have like many, many, many different grid cells. And they are, the the cells are sort of overlapping with one another.

• 29:22Michael Stevens?

  They're like spatial interval cells. 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-south?

• 29:40Hannah Fry?

  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.

• 29:52Michael Stevens?

  Oh.

• 29:52Hannah Fry?

  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 in mice and rats and has since been found within humans. And and this is the way that we're navigating. If you only had place cells, it's the same as having like a a bunch of Polaroids of like interesting places, but no idea how they connect together.

• 30:18Michael Stevens?

  Right.

• 30:19Hannah 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.

• 30:29Michael Stevens?

  They're two different systems. Man, I wonder if there are.

• 30:34Michael Stevens?

  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.

• 30:45Hannah Fry?

  Hmm. 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.

• 31:07Michael 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,

• 31:51Michael Stevens?

  all within a six mile radius of Charing Cross. 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.

• 32:27Michael Stevens?

  That corresponds to the reality of London, the city.

• 32:31Hannah Fry?

  I should say, actually, my, 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, when London, this web of streets is basically impossible to navigate for anyone who, 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, this idea that if somebody is willing to go through that, then they just have this professionalism and dedication to the job

• 33:16Hannah Fry?

  that, that you don't necessarily get with like a, you know, like a ride hailing app or whatever it might be.

• 33:21Michael 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

• 33:28Hannah Fry?

  Oh, yeah.

• 33:28Michael Stevens?

  to be a black cab driver in London.

• 33:32Hannah Fry?

  Yeah. I mean, they earn good money, right? Like, it's, it's a really good, well-paid job. You get to use the bus lanes in London. You can move around. You, 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.

• 34:05Michael Stevens?

  Can I submit one, too?

• 34:07Hannah Fry?

  You absolutely can.

• 34:09Michael Stevens?

  Okay, let me, let me send you one.

• 34:10Hannah Fry?

  Okay, one second. Let's go on Street View. Okay, I've got one here. Right. What's this? Where is it? Shall we, shall we reveal, reveal to the audience before I call him?

• 34:21Hannah Fry?

  Okay, so I'm looking at your picture. Did you, you went and got this on Street View?

• 34:26Michael Stevens?

  Yeah, this is taken from Street View and I'm like retrodoxing myself. These are the shops next to Kerwick 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 Kerwick Court.

• 34:45Hannah Fry?

  Okay, all right, I'm gonna give him a call. Hang on, let me, yeah, let me send in the picture. And let's give him a call. I'm gonna give him no time to to consider it.

• 34:58Speaker 04

  Hello?

• 34:59Hannah Fry?

  Hey!

• 35:01Speaker 04

  Hello?

• 35:02Hannah Fry?

  Did you see the image?

• 35:04Speaker 04

  Yes, I did.

• 35:05Hannah Fry?

  Go on, what, what do you, where do you think it is?

• 35:07Speaker 04

  I, very quickly, straight away, I thought Brunswick Square.

• 35:13Hannah Fry?

  Right.

• 35:14Speaker 04

  Yeah, so you've got flats above shops.

• 35:17Hannah Fry?

  Hmm.

• 35:18Speaker 04

  Got trees around it. So that was my instant thought, but I don't know what all the given shops are, but look at the shops. I think the Brunswick Square shops are maybe a little bit.

• 35:27Hannah Fry?

  Bit posher. Shall 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.

• 35:35Michael Stevens?

  I know, that's why this is a really tough one.

• 35:38Speaker 04

  In that case, okay, my other stab in the dark is somewhere around Kennington, the Edith and Castle, something like that.

• 35:44Hannah Fry?

  Hey, you're right! It's Kennington Park Road.

• 35:48Speaker 04

  Just about to say, okay, then, so is it very close to the station, Kennington Station?

• 35:53Michael Stevens?

  Yes, exactly, it's exactly across from the station.

• 35:57Hannah Fry?

  That's good, that's really good, Rich.

• 36:00Speaker 04

  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.

• 36:06Hannah Fry?

  You are a genius. Amazing, amazing, Rich, thank you, I appreciate it.

• 36:11Speaker 04

  I just haven't let you down.

• 36:13Hannah Fry?

  No, you absolutely haven't. Thank you very much, I'll, I'll see you for my lift home later, yeah?

• 36:19Hannah Fry?

  Cheers, bye.

• 36:19Speaker 04

  Bye bye.

• 36:21Hannah Fry?

  Very handy.

• 36:22Michael Stevens?

  That's really 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.

• 36:36Hannah 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, he's getting it, you know, pretty much spot on straight away.

• 37:12Michael Stevens?

  Yeah, yeah, yeah, yeah. If you, 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, but it's much subtler than that.

• 37:22Hannah Fry?

  Hmm.

• 37:23Michael Stevens?

  What he's able to do.

• 37:25Hannah Fry?

  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.

• 37:37Michael Stevens?

  Yes, all of them. Let's take that on as a challenge.

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• 39:25Michael 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. Okay, one group was from a tribe in Namibia and the other was just some Dutch children. Okay, just some Dutch children, you know.

• 40:02Michael Stevens?

  To researchers, they're a dime a dozen. But what they did is they compared these two groups of children. Why? Because their languages were very different. Okay, 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,

• 40:45Michael Stevens?

  say, a landmark. 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.

• 41:28Michael 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.

• 41:44Hannah Fry?

  That is so fascinating. So you end up with all these toys squished along the short run of the table?

• 41:50Michael 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.

• 42:15Hannah Fry?

  So, okay, right, two things. First off, I do wonder if you had a spider on your leg, right? You're like, can you sort of say, I don't know, to a Dutch child, be like, "There's a spider on your left leg," and you sort of brush it off and it's fine. But if you're with Namibian children, you'd be like, "It's on your northwest leg. No, don't turn around. Now it's your southeast leg."

• 42:35Michael 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 took, 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.

• 43:08Hannah Fry?

  No, true. But you would never know which way north was.

• 43:12Michael Stevens?

  But I never knew which way north was. That's right.

• 43:15Hannah Fry?

  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 a decision, as it were, something that is a direct consequence of the language. It's nice. It's a really nice study.

• 43:36Michael 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.

• 43:55Hannah 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?

• 44:14Michael Stevens?

  So how we orient ourselves in space is very culturally dependent. But what isn't is where we put ourselves in our bodies.

• 44:29Hannah Fry?

  Mm hmm.

• 44:30Michael Stevens?

  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.

• 44:51Hannah Fry?

  I wonder what the ratio was in our comments. I wonder.

• 44:54Michael Stevens?

  We should, we'll do a little study. Yeah.

• 44:56Hannah Fry?

  I can barely imagine saying, point to yourself. It sort of doesn't feel right to me to point to your head.

• 45:02Michael Stevens?

  Yeah, point to yourself. And, and I want to talk about this and, 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? Or 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 some, 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.

• 45:47Michael Stevens?

  So for example, um, there was a great study that was done. I, I love the, the experimental design here. They had people go into a room where there was a pole from this, the, the floor to the ceiling and it had this, um, 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.

• 46:28Hannah Fry?

  So it's like anchoring, but for arrows and where you are.

• 46:32Michael Stevens?

  Yes, where you think you are in your body is very much dependent on how it's been anchored. Right? Um, 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, this question of where you are in your body has a very specific, uh, 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? They all understand like, oh yeah, sure.

• 47:16Michael Stevens?

  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 a 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.

• 47:50Hannah Fry?

  Like your conscious center sits just behind your eyes.

• 47:53Michael Stevens?

  That's right. Like if you're some kind of little rat, like 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.

• 48:18Hannah Fry?

  What about deaf people? Because I sort of wonder, I mean, there's a lot for, for, for, for people who have, you know, full hearing, full vision. There's a lot going on in, in your head, right? But, 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?

• 48:39Michael Stevens?

  In the congenitally deaf and blind, there's very little information. Because a person in, with, 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.

• 49:22Michael Stevens?

  I think that even without vision and hearing, we still have other things that make our head a focus, like the breathing and taste. 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,

• 50:06Michael Stevens?

  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. Your heart speeds up. And this isn't just about emotions. It's also about like, what did ancient people think? Aristotle believed that all of our memories and our thoughts were happening in the heart.

• 50:34Hannah Fry?

  Well, because they thought, they thought the brain was there to sort of cool down the body, right? Cool down the blood.

• 50:38Michael Stevens?

  That's right. They thought that the brain's only purpose was to cool down the, 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, the marionette strings that the heart pulled to make us move. 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.

• 51:09Hannah Fry?

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

• 51:28Michael Stevens?

  Yeah. Yeah, 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.

• 52:10Michael Stevens?

  Generally, if you've been doing a lot of cognitive work, your, your, your head area will feel tired because you've been using your eyes a lot.

• 52:18Hannah Fry?

  Hmm.

• 52:19Michael 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.

• 52:34Hannah Fry?

  I do sort of wonder, though, because 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. 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, it's almost impossible not to imagine that that your consciousness is centered near them. But then at the same time, it's interesting how you said that people put their ego, their

• 53:17Hannah Fry?

  ego center between the eyes where there isn't an eye, you know?

• 53:22Michael 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.

• 53:31Michael Stevens?

  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?

• 53:44Michael Stevens?

  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 learned that like, yes, that's how it feels, but I have two eyes. 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.

• 54:13Hannah Fry?

  Adorable, adorable little cyclops.

• 54:17Michael 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.

• 54:36Michael Stevens?

  And there's, there's one video on YouTube where a parent asks their kids and the kids do it. They like, 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. They call it the Cyclops Effect.

• 54:55Hannah Fry?

  It sort of feels like this is the perfect opportunity. If you, 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.

• 55:05Michael 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 and it takes a while to learn that you have two eyes.

• 55:24Hannah Fry?

  Well, okay, 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 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 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. Your brain is essentially combining those two images as though you have one eye.

• 56:09Hannah Fry?

  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 a cute little cyclops, they are biologically perfect walkers. We only switch to one eye when we're using tools.

• 56:31Michael Stevens?

  Yeah.

• 56:31Hannah Fry?

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

• 56:43Michael 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.

• 57:19Hannah Fry?

  I didn't know that. I didn't know that. Every day with you, Michael, every day is a school day.

• 57:24Michael Stevens?

  So the 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.

• 57:47Michael Stevens?

  They would be very 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, we just wanted your face. 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'd point to the chest.

• 58:29Michael Stevens?

  It would be very weird to say, she took my car. If I pointed to my face, I'm pointing to my, like, eyes right now. Even though in, in, 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 Kenzie Cooper Rider, who said that when you're talking, any gesture you make moves the person's eye. Unless it's like a very general gesture.

• 59:10Michael Stevens?

  So if I, 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.

• 59:47Hannah 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, maybe today, Michael, we can, we can make a shift. Maybe we can, we make it so that everybody from now on, whenever they say something, they go, what about me? And just directly points to the end of the note.

• 1:00:06Michael Stevens?

  Yeah, yeah, yeah, yeah, yeah. 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?

• 1:00:33Michael Stevens?

  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. 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?

• 1:01:00Hannah 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, of your elbow. You know, that it's like, it's slightly easier.

• 1:01:12Michael Stevens?

  Sure. Maybe it's just easier to control the power and the volume of your knock in that position.

• 1:01:19Hannah Fry?

  But it does, it's also, it does feel like at your kind of communication center. You know, it's sort of, it does come back to everything that you're describing that you've got. It's, it's almost like your center of mass, but it's like the center of me.

• 1:01:32Michael Stevens?

  Right.

• 1:01:33Hannah Fry?

  Right?

• 1:01:33Michael Stevens?

  The ego center. 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.

• 1:01:54Hannah 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.

• 1:02:09Michael Stevens?

  I know, 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.

• 1:02:24Hannah Fry?

  And so when it comes to the question of where are you, finding where you are on the earth, easy peasy. Finding where you are in a room, bit harder. Finding where you are in your body, genuine mystery.

• 1:02:37Michael Stevens?

  Yeah. Is that even a sensible question?

• 1:02:40Hannah Fry?

  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?

• 1:02:48Michael 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?

• 1:02:58Hannah Fry?

  I no longer understand any of the things that I thought, 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 is Science wherever you get or listen to your podcasts, or you can like and subscribe on YouTube if you would like to watch us.

• 1:03:16Michael 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 [email protected].

• 1:03:25Hannah Fry?

  See you next time.

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