The Rest Is Science - Cognitive Ghosts

Episode Date: March 17, 2026

Ever wanted to squish a puppy just because it’s impossibly cute? Or felt absolutely certain you’ve lived this exact moment before? Hannah and Michael explore the bizarre, everyday glitches of the human mind, unpacking why our brains occasionally seem to short-circuit. They dive into the weird neurology of "cute aggression", or urges like thinking of throwing your phone off a bridge, to the jarring time-bending sensation of déjà vu to reveal how our grey matter manages overwhelming feelings and sudden memory misfires. ------------------- 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 Assistant Producer: Imee Marriott Researcher: Sophia Constantinou Producer: Simona Rata Senior Producer: Lauren Armstrong-Carter Head Of Digital: Samuel Oakley Exec Producer: Neil Fearn Learn more about your ad choices. Visit podcastchoices.com/adchoices

Hello and welcome to the rest is science. I'm Michael Stevens. And I'm Hannah Fry. I've got a little experiment for you today, Michael, and all of the people who are watching and listening. Okay. Your job, it's very simple. All you've got to do is I'm going to read your list of words and you need to count how many words on this list begin with the letter S. Okay.

It's very simple. Just keep the number in your head. Okay. Right. Here are the words. Bed. Awake. Tired.

Dream. Blanket. doze, yawn, night, dark, pillow, rest and nap. Got it? Okay? Yeah. All right. I want you to hold on to that number in your head.

Just know that this episode today is all about cognitive ghosts. We'll come back to it in a moment. This episode is brought to you by Cancer Research UK. If you wanted to type out the entire human genome, you would have to type at 60 words a minute. for eight hours a day for about 50 years. Okay, that's the scale of the DNA rulebook inside each one of your cells, telling it when to grow, when to divide, and when to stop. And different tissues read that same rule book in different ways.

So a skin cell doesn't behave like a lung cell. And cancer can begin when those instructions change, not one dramatic moment, but through small, gradual edits over time. Now, cancer isn't one disease. It is more than 200 types shaped by where those changes to the rulebook happen and how cells respond. Cancer Research UK is the world's largest charitable funder of cancer research, backing studies across all types of cancer. Work that takes years of very careful, steady progress to deliver each breakthrough. For more information about Cancer Research UK, their research, breakthroughs and how you can support them,

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Find your advisor at IGPrivatewealth.com. Hannah, I can't wait to see what the point of that list of words were, but I will tell the listeners out there that for this episode, Hannah and I decided to explore the phrase, cognitive ghosts, and what that means to us. So we've both come prepared with some cognitive ghost stories, and I can't wait to see how we both interpreted that and how it all comes together.

Okay, have you managed to hold on to that number in your head? Yes, I have. Right, how many of that list started with the letter S? Zero. Correct. Right, now what I'm going to do is I'm going to say three words, and you need to tell me whether these words were on the list. All right?

Okay. Blanket was. Correct. Jellyfish? No. Correct. Sleep? No.

How is your brain feeling right now? Well, it's feeling. It's feeling. a little, how do I describe this? I think I've heard of studies like this before where there's like a word that should so totally be on the list but you don't mention it. And so I start to confabulate that it was on the list.

I would have thought sleep was one of them if I hadn't have been paying very close attention to whether words started with S or not. And so when sleep never showed up, because I knew, because I was waiting for it, I was like, it's the only S word that's going to fit this list, and it never happened. I'm like, sleep is very conspicuously absent.

Absolutely. Okay. So this experiment that I've just done on you is what is described in a paper that's called the awareness of novelty for strangely familiar words, a laboratory analog of the deja vu experience. So, essentially, what is going on in your head while you're listening to that list, and particularly when I ask you if the word sleep appeared, is that you know that it wasn't on the list because it starts with an S and you've already told out loud that there were no S words.

That's what happened. But at the same time, the word feels kind of spookly familiar, right? Sort of like triggers this memory that isn't a memory. And this is what they describe as artificial deja vu. This is the only way, really, that we have to trigger deja vu in a lab in order to study it. Oh, so we get people to think of it sort of quietly. Quietly. And then later, it's deja vu like when.

they hear it again. That's exactly right. Exactly right. Even though they know it was a false memory, they never actually heard it in the first place. I got to say, it's so much less cool than real deja vu. It's cool to real deja vu. Hammers home the topic of the episode, cognitive ghosts. Things, I mean, that means a lot of things. But deja vu is definitely one. It's like really, really hard to conjure up yourself. And yet, it fleetingly passed. through, it interacts with us kind of, but our instruments aren't always ready. How can we study it? So the thing that is quite nice about these experiments is that when you do this to people, when they're in an fMRI scanner, it's not the hippocampus that the memory center of your brain

that lights up. Instead, when you hear the word sleep, it's the frontal cortex, which is the area of your brain that is responsible for decision making, for conflict resolution. That's the bit that kicks off. And so the argument here is that deja vu, as we experience it, it's not this false memory. It's more like your fact-checking software, as it were, in your head. It's kind of running through. It sort of feels as though there's something familiar, but you're running through your memories and not finding it. So it's your brain glitching, essentially, saying, wait, no, have we been here before? We haven't been here before. This familiarity that I'm feeling is a phantom signal. Right. And that you can see in the scan. So even though, as you say,

it's nowhere near as cool as real deja vu, seeing in the scan is also is nonetheless really cool. Wow. I love that because again, it's not as cool of an experience, but we just can't catch deja vu in the act and study it. It's still so mysterious. You're right. Like the leading hypothesis for the feeling of deja vu that, oh my gosh, this happened before. This is so familiar, but I can't tell why. that might be your brain trying to solve a little problem that it's created for itself. The processing of the data happened way faster than the perceptual awareness. So your brain is already responding with feelings and associations to the thing before you actually see it. And you're going, hold on, but this is already here, deja vu.

So that list strategy allows us to do a similar thing with less effective power. It's not like, whoa, trippy. Is my brain okay? But if it allows us to recreate some of those brain processes, maybe we'll finally be able to study deja vu better. I would love to be able to induce it for real. For real, I know. In a way?

Well, I could convince people that I was a sorcerer. I could convince them that demons were at work. I don't know. That'd obviously be my first use of the technology. Of course. It goes without saying, rather than for the advancement of human understanding. and the sum total of all scientific knowledge. Of course, you being a sorcerer of makes much more sense.

The thing is so much of how your brain works, right, is memory is essentially a survival strategy. It's like, can you take the experiences that you had before and apply them in the future to make life easier, to make your survival more likely? And so what we know now about memory is that it's not like watching a video recording of where you've been. It's like you take the gist of your experience and that's the stuff that you that you recall. So essentially what's happening when you have a deja vu in real life,

when you have a kind of full blown one, is you, I don't know, walk into a room and there's something about the gist of that room that triggers a feeling of familiarity. Maybe the chairs are laid out and there's something about them that's similar to the way the chairs were laid out in your grandmother's kitchen or whatever it might be. So your brain, is like, oh, okay, I've been here before. There's this familiarity and goes looking for the relevant memory effectively. And when it doesn't find it, that's the experience that you have, this kind of very strange feeling that you've been there before because you have the familiarity but without the memory.

Yes. And it shows us that those two things, familiarity and the memory, are separate. Yeah. That we can feel that something is familiar. We can know that we know something, but not immediately be able to recall it. And that very specific phenomenon has a different name. That's Presquevue. Presquevue, when it's like on the tip of your tongue.

The tip of the tongue. Yes, I love Presquevue because it's so trippy. It's so weird and it makes me feel so out of control of my own mind. And it's not just a me or a you thing. It's like a socially contagious phenomenon. Presquevue is the experience of, as we said, tip of the tongue, when you know that you know something, but you cannot call it to mind and say it.

You can picture the face of that actor. Oh my gosh, I've seen like every movie they've been in, but what is their name? The people around you often can't help because in some way that block in your mind is contagious and everyone at the dinner table goes, oh, yeah, no, I can't, what is that? No, it wasn't, oh, I can name all the movies he's been in.

Or I can picture the person. They're a coworker of mine. We all know them, but what the heck is their name? And it doesn't come to you until you stop trying to find it. The whole time, you know, you know it. It's not like a, I can't remember. You know that it's there, it's in there. And then you change gears.

You start a different topic of conversation. You go make a sandwich, and then suddenly you go, oh, Gary Sinise. That was the actor who played Lieutenant Dan and Forrest Gump. Duh. Presquevue was also a kind of very, cognitive ghostish thing. We, I think, can study it better than deja vu. We know a bit more about what might be going on.

It seems to be the brain trying to help us, except it missed the mark. And we're thinking of all the movies and all the other actors that have been in that movie or other related things to the target. And to help us, the brain inhibits recollection of the actual fact we want and facts that are adjacent to the ones

that we're pulling up. And so while you're in that space trying to access that target, you're getting everything but it. And you need to stop, have your brain start helping you in a different way. And now you can open the box that has the target in it. I really like, well, I mean, I don't like that feeling at all. I absolutely despise that feeling of the word being on the tip of your tongue. The other one, there's one other, which is called Jamevoo, which is where you can sort

of take something quite solid and make it into something quite ghostly. And this, by the way, Jaamee Vu, is the feeling of not knowing something that is actually familiar. This is very easy to trigger in a lab. So there's a paper on this, which is called The Induction of Jaumevue in the laboratory. What a great title for this paper. Because essentially what they did is they took close to university students and they told them to take a single word and just repeat it over and over and over on a piece of paper. So they used words like door, money, the was one of them.

And the students were told to keep writing as fast as they could. And they were only told to stop once they felt peculiar, or when their hand hurt, or when they just couldn't take it anymore. And about 70% of the students stopped because they felt peculiar. They felt peculiar before their hand hurt. And normally it's only about 30 repetitions that you need to do that can induce this. If you just choose whichever word you like, write it out, 30 times and it'll start to do something really strange in your in your brain.

I think so many of us have accidentally discovered this like as kids. You repeat a word over and over again, seller, seller, seller, seller. And then you start to go, how is that a word? This seems so weird suddenly. Doesn't make any sense. We're both moving in the direction of easier to study, but more eerie feeling. The author of that paper, the induction of Jamévin in the laboratory called Chris Moulin, he thinks that there's a reason, there's a good reason for Jammey Vu, which is that if you get an animal who's sort of stuck in it in a repetitive behavioural loop like, I don't know, examining the same rock over and over and over and over.

It makes them really vulnerable, right, sort of a survival thing. His idea, I mean, difficult to validate this, but his idea is that if you have neurons that are firing too repeatedly in the same path, right, the, the, the, the, the, the, the, the, the, the, the, the, the, the, the, the, the, the, then the brain triggers Jaamevu to make the familiar feel like it's really alien to sort of shock the brain out of doing the same thing again and again and again and again and again kind of forcing your brain to go and pay attention to something else instead wow that's a pretty clever technique and I like that theory

does it make so much sense for survival for that you create your own novelty but it's such a fun little trick to do when you're bored just looking at an object like looking at at a bottle. You're just like, oh my gosh, bottles are so friggin weird when you think about it. If you really just focus long enough, and it's our brain trying to keep things fresh. I feel like you've sort of built most of your career on taking really ordinary things, Michael, and saying, they're really weird if you think about them.

Hey, vis-sasa, ja me vu here. Exactly. It's like, we all know that things fall down, but which way is down? And then you start to go, oh, shoot, which way is down? I could have answered that five minutes ago, but now I'm... Now I'm stuck. Now I'm stuck. There's lots of these, right? There's lots of different situations where your brain is, you have these two underlying systems in your brain, either memory and familiarity or whatever it might be. And they're just mismatching ever so slightly. Yes. There are so many dejahs, or so many vues, if you will, depending on how people have decided to construct the word, that we know even less about. For example, Deja Reve is something that I've tried to research. to no avail. What is it? Deja Reve is that feeling when you witness something in real life and you go, hey, I saw this in a dream before I think. That's happened to me. I've been like, oh my gosh,

I dreamt this guys. And one, it's boring to everyone but me, right? Like no one else feels this, this eerie, eariness. They're just like, okay, man, I don't know. Like, you're not psychic. Stop. But it's a weird feeling and you can only really find information on it on like reddit where people are like yeah that's happened to me or like like sort of new age wellness blogs talk about it and why that feeling happens we don't know is it related to deja vu where instead of thinking oh this has happened before in real life something's a bit different and we start thinking hey this happened before but in a dream we honestly don't know so that's why i think kodaghs. cognitive ghosts is a great overarching category name for these things.

There's so much research that still has to be done. But the thing is, I mean, there's lots of examples of where people have had memories of things that have happened in past lives, right? That they have discussed and been absolutely convinced that they happened to them before, right? But that actually, once you dig into them, our brains are not very good. at remembering the origin of where our stories come from. So there's a couple of really famous stories about this of people who have been hypnotised

and then while they were under hypnosis, they've come up with these incredibly elaborate stories. There's one in the 50s where an American housewife called Virginia Taihi. And when she was hypnotized, she claimed to be this woman called Bridie Murphy, who was born in Cork in 1798. She gave all these details about her husband, the grocer's, all these Irish songs and so on.

And everyone was really stunned because she'd never been to Ireland. And there was no, you know, internet to look things up. And how could she know the name of this obscure 19th century Irish grocer, which she got right, by the way? And then this is all in the 1950s, journalists end up going to Chicago, start knocking on doors. They discover that there was a Irish immigrant who lived across the street from her when she was younger. and the neighbor used to tell her stories when she was a kid, singing all these songs, including the names of all of these places. And the neighbor's name was Bridie Murphy, Corkill.

So it's like you have the memory, but you don't remember where it came from. This has happened over and over again, where people have thought that they are recalling something from a past life, but actually it's from a novel that they read or a story that they heard. So I think that that's the thing about the, a deja reve potentially, is that it might be a deja vu where you're getting the familiarity and the memory mixed up, or it might be that you have experienced some similarities in a story before

that you don't remember you watched it, you just thought that you dreamt it instead. Yes, yes. I think the nature of memory is responsible for so many of the cool things that we love to share and talk about and experience. I've thought a lot about whether reality was different when I was a kid. This is, again, like a weird one, but you'll see this on Instagram and TikTok all the time where people are like, you remember how in like the 90s,

everything was like more colorful or like the sky was bluer? And I feel that way too. I feel like the color of light was different, but I can't tell if it's because photographs of the time used different film and printing techniques from books and magazines were different and reality was the same but I just can only remember it now by looking at photos

which give me the wrong impression of how things looked but we definitely we prototypicalize our experiences when they turn into memories so colors become more primary making them blockier and brighter and more saturated so when we think back to

man my school was so bright and now when I return as an adult later in life, and it just seems smaller and dingier and doler. A lot of it is that remembering, like you said, is not a perfect replica. I think the word remember is perfect. We are re-membring. We're like Frankenstein together what happened out of pieces that are slightly different this time. But it's not just memories that are being confabulated and constructed.

It's also live experience. blind sight is one of the freakiest cognitive ghosts. Blind sight is the phenomenon whereby someone is legally blind. They cannot see. They can't read a street sign. And yet they act as though they can see. It's very paradoxical. First of all, how does it happen?

It's brain damage. It can be caused, for example, by severing the two halves of the brain, cutting the corpus callosum. A person with blind sight is legally blind. They need help. They can't read a book. They can't read a street sign. But if you throw something at them, they will flinch and they will try to block it. What?

And if you ask them, well, how did you, why did you raise your arm? They cannot tell you why. They literally don't understand. And they confabulate answers. They say, oh, well, didn't you? Didn't you tell me that you were about to throw something? Or, well, I could, I suddenly needed to raise my hand. The famous example is that you can show these people a prompt, like, go get me a drink from the fridge.

And they can't read it. They have no recollection of reading those words, and yet they will get up and go to the door. And if you say, hey, where are you going? They come up with all kinds of reasons. Oh, I heard a sound. and they truly believe these explanations. Wait, hold on, I don't understand. How can they possibly read it if they're blind?

Because a non-conscious part of their brain is receiving the visual signal and responding to it, but the awareness is not getting the message. And so they can't access what's actually happening in front of them. Their eyes are still processing what they're seeing. It's just not being told to their conscious self. So they see the message, go get me a drink. And when I say they, I mean at an unconscious level, but then memory and awareness is never told.

So their body starts reacting to things like even a bump in the road. They'll avoid the bump in the road. But they won't be able to tell you how they did it. And they come up with a ghostly fabricated reason on the spot. Why did you take a step to the left? I don't think I did. I think I kind of tripped. But they didn't trip.

It's just their brain is always trying to explain their own behavior to themselves, and they buy it wholesale. Blindsight in humans is really hard to study because you kind of have to like wait for someone to have this particular kind of brain damage. And under what conditions would someone get that kind of brain damage? I mean, that sounds like a sort of surgical intervention. There are so many causes. There are all these different stages of visual processing in the brain and problems usually caused by stroke or tumors or anything. To almost any of those regions can sometimes result in blindsight. It's not common enough that we know that much about it.

But it does provide yet another example of the fact that there's you. And then there are these ghosts inside that are doing a bunch of stuff without your authority and control. These sort of shadows of your central self. Yeah. I've been thinking about this a lot. It may be part because of, you know, you were describing about where do you sit in your body? we had this conversation a couple of weeks ago on the podcast. I think that it's very tempting to believe that you have this sort of humunculus, as it were,

this sort of like center of yourself, that there's like there's one version of you that exists. And all of these systems, your site system, your memory system, your familiarity system are kind of spinning off like a spider diagram from this central version of you. But when you describe things like that, when you describe people whose systems function perfectly well, but they just can't explain to themselves. It does make me wonder whether actually the whole idea of us having a single central self, like a humunculus, is actually real at all. Maybe it's just, maybe we're just like the sum of ghosts rather than like a single individual

with all of these things spinning off it. I know. I know. It's really trippy and it's really frustrating because as easy as it is to believe that I'm a homunculus, which means a little person inside my head pulling the levers and looking out the eyes, you then have to wonder, well, who's inside the mind of that little person? And you get an infinite regress that doesn't explain anything. I think one thing that we do know for sure is that when there's a mismatch in the levers,

the humunculus gets very confused. Yeah. Yeah, and it can be scary or it can be fun depending on, you know, how you interpret it. For me personally, I've got a really strong feeling of what's called high place phenomenon. I don't like heights at all. And I've gotten more and more scared of them as I've gotten older. It was so bad at one point that I looked this up. Basically, what high place phenomenon is, is that when you are up high and there's an edge or like a cliff or you're on the patio of a high apartment building, I start to feel like I'm.

being drawn towards the edge. And it can feel either like there's a slant and I'm actually falling or I'm being drawn or I'm going to fall off basically. Or it can feel almost like an internal compulsion. Like there's something in me that makes me want to jump. Our best idea about what causes this high place phenomenon is that right away, the high place the ledge the cliff scares you and you become so scared that you could fall off that your brain doesn't know how to deal with that fear because you don't normally just suddenly leap two

meters forward right and so to explain the fear your brain creates a complete ghost a confabulated unreal desire you must you must be falling in that direction or you must want to because nothing else would explain the fear. And so now you've got two things, the fear and an illusory belief that you're going to fling yourself off the edge. I have to tell you, when I first moved to London, I got this feeling so intensely every time I got on the tube that what I really wanted to do was to jump off the platform. As the tube train came into the station, that it would be so easy to do it. Yeah. And then sort of catching yourself doing it. And I ended up talking to a therapist.

I was seeing a therapist at the time and talking to him about it. And apparently this version of High Place phenomenon or La Pelle du Vid or the Call of the Boyd, there's a nice French name for everything in this episode, it turns out. There is, yes. I love that the call of the void. Hello, I'll answer. Yes. In Londoners on the tube, it's phenomenally common.

60% of Londoners apparently have this, have this exact feeling. And that kind of demonstrates, I think, that it's like this is something that is in all of us, this mismatch, this sort of this fight, this tension between the different versions of ourselves that's going on. That's right. Because the point here is that this desire to fling yourself off the ledge or into the oncoming train wasn't already there already. It seems to be the only interpretation the brain can come up with to explain certain fears that are generated. and the strength of those fears. So, yeah, we're in a lot of ways just along for the ride, and it's a crazy ride. There are other examples of this. Like there's a tussle going on in your mind of what you want to do.

I'm thinking about like when you see a really, really cute puppy. Yes, it's called cute aggression. And it is actually a pretty new area of investigation. We've known about this forever, but it's been hard to pinpoint. what's going on. Cute aggression describes the feeling we have when we see something cute that goes beyond just, oh, I want to protect you. I want to keep you warm.

And it turns into I'm overwhelmed by how cute these photos are or this puppy. And I just want to squeeze it. I just want to fight it and eat or eat you up. And the study of this, I just love, let me open this up because the researchers just showed people super cute things and then listened to them. talk about it and they coded people's responses. And of course, you're going to see the usual caretaking things. I want to protect it. I want to hold it. They just, they say appraisal utterances like, oh, that's so cute. Or maybe they'll say, I want to approach it. But they might

feel overwhelmed. I can't stand how cute this is. But then you go even further and you start to see things that can be coded as aggression. You see it and you just want to go, er, you want to say gur, you want to squeeze it, you want to pinch the cheeks, you want to eat it up. I want to eat you, yeah. Through your gritted teeth, you speak. And in a lot of ways, this is, I think, similar to the ghost of I want to fling myself off the edge. Right.

But it's not being created by the brain as an explanation for a fear. It's being created by the brain to bring itself back down to homeostasis, that the instinct we have to protect and pay attention to and cuddle and care for cute things is so overwhelming that the neurotransmitters responsible flood the brain and to bring itself back down to normal, it has to bring in other neurotransmitters that do the opposite effect and encourage aggressive behaviors. That's the current leading theory because we've looked at all the other options, but it's just that you see it, it's so cute, but you need to also push it away, but you also need to like hurt it because you're being overwhelmed by your desire to not hurt it. And it's very

confusing. And we see this in other cases too. Like when people get so, so overwhelmed with joy and happiness, they cry. Or something really awful happens and they laugh. I know. And it's frightening. But again, it's another kind of ghost that's created, not one that's there as an explanation, but one that's there to help write the ship to keep it going straight. Oh, you're going too far in the happiness direction time to cry. Oh, that was really, really awkward and terrible and tragic and now you're laughing. Ah, shoot, but at least like together they keep us normal. There's all these different versions of you that are continually fighting inside your head. You know, and on the topic of these ghosts and how there sort of seems to be multiple

versions of ourselves inside ourself, another thing that happens to me a lot is the hypnotic jerk. It's sometimes called a hypnagogic jerk. As I'm falling asleep, I will suddenly twitch and wake up. I have a very strong sense of feeling that I was about to fall. In fact, I'd love to know in the comments how other people experience this. For me, it's almost always accompanied or prefaced by a dream where I'm doing something like riding a bike or climbing a tree and then suddenly I fall over and I wake up The science tells us that the hypnot jerk occurs because when we sleep, our muscle tone and our blood pressures goes down. If our awareness isn't quite asleep yet, it's unaware of what the heck the body is doing. And as far as it knows, our body has just lost all tone and support.

So that's what it feels like when we fall. So it goes, we're falling, like, fix this, like brace yourself. And that's what that jerk is. What I find so weird is that, for me at least, it's not just an out of nowhere falling experience. It is, in my head at least, the culmination of a whole dream. I've been skateboarding for 30 minutes, and then suddenly I tripped and fell,

and that's when the jerk happened. So either my dream knew that this jerk was coming, this relaxing, my body's going to lose its muscle tone as I sleep. Or it was completely caught off guard and then has confabulated a memory of an entire dream that was happening just before, an entire explanation for why I suddenly felt like I was falling. And that 30 minutes of dream has just been put into my head at that moment. You've taught me something, Michael, because I had a different understanding of what was going on with the hypnotic jerk. Okay, tell me. Well, okay, so I thought, but I've just checked and your one was right.

So, you know, congratulations. This is not what it is. This is, if you'd ask me, okay, but I want to hear, I want to hear what it's not. Okay, so I thought it was that at some point during your sleep cycle, it's important that your body goes into a state of essentially paralysis so that you're not flailing around and hurting yourself while you're asleep. And that this is what can go wrong when if you have,

sometimes you can wake up where your mind wakes up before you come out of this state of paralysis and then these night terrors. No, wait, there's a particular name for them. them, isn't there? Your sleep demon. Or sleep paralysis, right? This is what can happen. So I thought incorrectly, apparently, that what was happening was that your body was going into paralysis and to check that you were in paralysis, your body was testing, was testing it. But apparently that's not true. Was testing it out. Are we ready to sleep? Is the body shut off? Am I ready? No. Sleep paralysis is like literally the opposite of the hypnot jerk. So sleep paralysis is like a different combination

of problems between these two different selves, the physical self that is relaxing or under paralysis so that while you're sleeping, you're not flinging your arms around. And then the awareness of like your actual conscious, what's happening and how am I creating a story around this. Regardless of the reason, and your one I think is more scientifically valid, my was a debilipy function theory. Why would your body do this? It sort of doesn't make much sense. It sounds like something's gone wrong. A lot of people have asked that question. And funny enough, the answer is that they are, these phenomena are in another way a kind of ghost, meaning not a confabulated phantom, but something from the past that's still around, even though, you know,

it's gone. Like a vestigial cognition. Frederick Coolidge out of the University of Colorado, his theory is that the hypnot jerk is this old thing from evolution from back when we lived in trees. Because we don't see hypnot jerks in all animals. Now, we do see them in cats and dogs. You know, they'll startle themselves awake. We don't know what they were thinking or how it felt, though. That's the problem. We do.

They were dreaming of sausages. Back, right. Back when we were being attacked by a predator or something. Sure. And sometimes a hypnot jerk can be associated with that, too. Sometimes I've felt like in my dream like a baseball hit me. and that's why I jerked. But the tree hypothesis is that back when we were living in trees,

as you lost muscle tone, you could fall out of the tree. And so that jerk is a response to, oh, you better write yourself and become more stable because you're about to go into the relaxed portion of sleep where your muscles aren't constantly flexing against the tree branches. So it's like a corrective measure that we no longer need because we sleep on mattresses. Okay. So this is a different kind of ghost. I mean, there's like, there's ghosts in every direction here then.

There's the two versions of yourself that are mismatching. But there's also that there's this lingering memory of your ancient past. Exactly. I like that. Because actually, when we decided we were going to do an episode on cognitive ghosts, when we decided we were going to do an episode on cognitive ghosts, Michael and I took the title, went off, decided how we wanted to interpret it. And actually, one of the things that I was thinking about

was this idea of things that we currently think that are actually just these hangovers, these echoes of our historical past. And one example that I was thinking about was have, there's lots of my family who are really into crystals, like sort of the healing powers of crystals. Right, right, right.

Anyway, there is this great myth. I don't know if you've come across this, that if you wear amethyst, you can't get drunk, right? So if you're going on a night out, pop a bit of amethyst on, and you'll be fine. Do whatever you want. Okay. Thank you for your, I could see by your face, your, your score at the very idea.

Oh, no, yeah, right. All I'm saying is I've tried it doesn't work. The cops don't buy it. The cops don't buy it, exactly. The thing is, I think, is a really interesting example of another type of cognitive ghost. Okay. because actually what used to happen in ancient Greece, ancient Rome, what people would do is they would have these feasts that would last for, you know, hours, hours,

and hours, and hours, and hours, maybe even days. And if you were a kind of cany politician or a very clever noble person, you would want to keep sharp during all of these feasts when there is wine flowing around all over the place. Now, important to say that actually what they used to do is they used to slightly water down there, wine, they'd have it like a ratio of one to two. So it would have this slightly purple hue. So what people would do is they would have goblets that were made of amethyst. Because in that situation, when you had water in it, you could not tell when someone was holding it that they

were just drinking water. What? Oh my gosh. So actually amethyst was this way to trick people into thinking that you were drinking when you were actually sober. Right. And so the fact that you're not drunk must be explained by the amethyst glass, the crystal. Right. Rather than, rather than, you know, and over time, that kind of really solid idea has morphed into something that's this, just this echo. Another example of this is with salt, because of course, before refrigeration, salt was absolutely vital for human survival.

You know, you would use it to preserve meat for the winter. It was also, by the way, incredibly expensive, difficult to harvest. The word salary even comes from the Roman practice of paying soldiers at salarium, right, an allowance to buy salt because this is the thing that would allow us to survive. That's amazing. I love that. I love sitting in a restaurant looking at the pepper being like, there's so much pepper here. People used to die for pepper. Right.

And salt as well. Salt too. There's so much salt. I could spill this and the restaurant would just be like, that's all right. But it used to be that that was your salary. That was your salary. Right. Exactly. And so this is it because the idea of spilling salt, it wasn't just this sort of ups moment of like, oh, made a bit of a mess. It was this devastating financial loss and this threat to your entire family's winter food supply. So it became this idea of that there would be the devil. If you spilled salt, the devil would appear. So you have to throw salt over your left shoulder because the devil is there. But what's happened is the reason for,

caring so much about salt has dissipated, but the remnants of our stories that we tell ourselves and each other from generation to generation to generation, this is like the oral history of something that really used to scare our ancestors. I think that's a different kind of version of a cognitive ghost. Right. It haunts us in a more innocuous form still to this day. Totally, totally.

But you know what? I also, in interpreting this title, I also came up with a few other cognitive ghosts that happen inside the body or maybe even outside the body. And I reckon we should come back to those after the break. All right. This episode is brought to you by Project Hail Mary, the new spectacular space adventure movie coming to cinemas from the author of the Martian, Andy Weir, and the directors of the Spider-Verse movies, Phil Lord and Christopher Miller. But here's an even better combination, teachers in space. Hello, thank you. Project Helmery stars Ryan Gosling as science teacher of Rylan Grace, who is sent unexpectedly on an impossible mission into space to discover why the Sun and the Stars are dying.

And he teams up with an unimaginable ally to defy all odds and save the universe from extinction. Okay, here's a question for you, Michael. What kind of prep would you hope Ryan Gosling had done for this role in order to play the role of a science teacher? He should have spent a bunch of time with cool teens. and tried to teach things to them so that it wasn't just like a good explanation, but also kept their interest and made them want to hear more and understand it so that they could share it to be cool too. See Project Hail Mary in Cinemas and IMAX from Thursday the 19th of March. You can also catch it early on Saturday the 14th of March, which is Pye Day, and Sunday

the 15th of March. This episode is brought to you by Cancer Association. We often think of beating cancer as treatment, but imagine stopping it before it begins. After years of work, Cancer Research UK scientists are launching a clinical trial of lung vacs, the first vaccine designed to prevent lung cancer. It builds on TracerX, the world's largest cancer evolution study, which tracked lung cancer cells over many years to uncover the disease's earliest warning signs. Lung Vax is designed to train the immune system to spot these signs early on, destroying 40 cells before cancer develops. So it's not treatment, but preventative with the potential to stop lung cancer before it starts.

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Welcome back. So far we've been talking about cognitive ghosts inside your own mind. But Hannah, you're going to tell us about some that exist outside of the mind. Well, you know, I sort of think I want to take ghosts a little bit more literally. I've never had the opportunity to talk about ghosts on a science podcast before. So I thought I'd run with it, frankly, Michael. Please do. And in particular, I want to talk about extreme explorers and ghostly companions that appear to them in their moments of most dire need. So there's some really famous stories about this of people.

who have crossed the North Pole, been up mountains, real endurance situations where they have then seen ghosts. Probably the most famous story about this is Shackleton. His ship, endurance was crushed by the Arctic ice. And so Shackleton and two of his men, they had to make this unimaginable, desperate voyage across the ocean and then trek across these glaciated mountains of South Georgia Island to find this whaling station. And, And while they were doing this, they were, I mean, literally starving. They were freezing. They were severely sleep deprived right at the very edge of what the body can manage.

And a while later, Shackleton, I mean, they survived it astonishingly. Shackleton wrote this line where he said, it seemed to me that as they were walking across these lands, there were four, not three of us. Okay, so he had this like vision of a ghost. But the thing is, Shackleton didn't talk about this with his men. He didn't want to say to his other two men, it feels like there's another person here until weeks later. And when he did, when he finally brought it up, it turned out that Worsley and Crean, the other guys who were with him, both confessed that they had felt the exact same invisible fourth person who was walking with them the entire time. Oh, weird.

How strange is that? So T.S. Eliot wrote a poem that called The Worse. wasteland. And the first line is, who is the third who walks always beside you? It's this, this idea of the third man, the kind of the extra person who you weren't expecting to be there. Anyway, this is like such a strange question. It really perplex people for a really long time, because how is it possible that you have three separate brains hallucinating the exact same ghost being there? Yeah. And then you see this story pop up over and over again. There's Another example of this Frank Smyth, who was this British mountaineer, he was attempting to summit Everest, didn't have any supplemental oxygen.

It's like back in the days when they did it properly, terribly, and mostly fatally, but properly. His climbing partner had to turn back. So he was totally on his own. He's at 28,000 feet. He's in the death zone. And then he felt this ghost appear next to him. And the presence that Smyth felt was so visceral, so tight. totally physical that he ended up taking his rational brain just couldn't handle it at all. And at one point he reached into his pocket, pulled out a bit of his rations, a bit of Kendall mint cake, broke it in half and physically turned round to hand it to the ghost. And it was only when he turned round that he realised that this, this ghost wasn't there. This is like so mysterious, so completely at the edge of, I mean, it's really proper ghost

stories this. Yeah. It turns out there is a really scientifically credible explanation that covers all of this simultaneously. Wow. And it turns out that when you have extreme physical exertion, also if you have sensory monotony, so especially if you're surrounded by snow, right, you're kind of staring endlessly at white snow, there is this neurological glitch that happens. It's in the temporal paratal junction, which is the bit of your brain that's like your

conscious body schema. It's the bit that's in charge of your proprioception. You know, if your proprioception is kind of the data, the TPJ, as it's known, is the thing that kind of does the 3D rendering. It's the bit that like works out where your body is, where your body ends and the world begins. And there is this glitch that can happen in it, particularly when you are, when you're deprived of oxygen, it takes all of your own internal sensor motor skills. And and then mistakenly projects them outwards outside of your body, kind of creating this hallucinated version of yourself that your brain thinks is this separate entity.

And it turns out this isn't just a theory, right? This is what I think is so amazing about this. All these incredible stories from the past. It's not just a theory because there is a team of people who have managed to replicate this in a lab setting. Oh, wow. And you, Michael, can have your very own. ghost, if you like, and I can tell you how to do it.

This is 2014. It's this group of neuroscientists. This is at the Eccole Polytechnique Federal de Luzan in Switzerland. What they decided to do, they were trying to summon this cognitive ghost. And they did it so well that they ended up freaking out loads of the participants. So what they do, you put someone in a room, okay, you put a blindfold on them, earplugs in, So they've got kind of no visual auditory cues. They stand in the middle of the room.

And in front of them, there's this robotic lever that they can push and pull with their hands. And then directly behind them, there is this secondary robotic arm. So when they first go in, they can move the lever and it moves the arm around them. And then the arm sort of pokes them in the back. And it all happens instantaneously. They're directly connected. Motion of the lever moves the poker in the behind you. Exactly.

And that's, you know, it's like a bit of weird experience, but it's fine. You know, you can kind of deal with it. It's no big deal. you're moving your own hand and you're filling on your back, right? But it's fine. You're in charge. But when the brain gets used to that, then what the researchers did is they introduced this neuroglitch. So they add this 500 millisecond delay. That's it.

Which is almost nothing. It's half a second. Half a second. Exactly. Thank you. Put it in real terms. Between the participant moving the lever and the robot on the back poking them. But because with that gap, which, you know, doesn't seem like very much, but to your brain, it's an absolute age, the brain can no longer reconcile the timeline of you're moving this thing and then this, you're the cause and there's the action.

And so it defaults to the only plausible solution, the only plausible conclusion, which is that if I didn't cause this touch, there must be someone else in the room with me. And so all the participants, they don't just feel this mechanical poke. It's not just like, oh, I'm just getting poked. They overwhelmingly report this powerful, undeniable feeling of presence that there is someone who is standing a few inches behind them. Some people felt multiple ghosts kind of crowding around them. And this illusion was so visceral and freaky and upsetting that loads of these very healthy, very rational participants were like, I don't want, I don't like this.

This is freaking me out and took the blindfold off because they were completely convinced that someone snuck into the lab and was tapping them on the back. Wow. Isn't that good? I so want to do that. I want to feel that experience. And so could it be possible that a delay like that can happen not even with a mechanism, but in your own body when you're exhausted, when you're nutritionally in trouble?

And suddenly you start to feel like your own behaviors are those of another presence. Exactly. To possibly explain what happened to Shackleton, what happens to these North Pole explorers. Right. And add in some starvation of oxygen to the mix. Add in the sensory deprivation of you can't really tell what's going on in the landscape. It turns out that this is something that happens. I mean, it's either that or they really did have a ghost to appear to decide them at their... Right. Sure. It could have been a real ghost.

I've been a real ghost. I'm genuinely okay with that as another alternative explanation. It's funny how all of these things, including this one, are so related by mechanism to deja vu. Like just a little bit of a disconnect between two processes that normally work together can generate such eerie feelings. Yeah, that you can no longer explain. You just know that it feels really strange. I also took a very different interpretation of cognitive ghosts. And I started to think of cognition, things we think that aren't real, that aren't really there.

And I thought about tropes. I thought about how in books and movies, we almost have a completely different reality. One where, you know, when someone gets electrocuted, they zap around and you can see their bones through their body. And like a lot of people truly believe that that's what happens when someone's electrocuted. Because what really happens is. What really happens is that your muscles completely become rigid and you look frozen. There isn't the kind of the thing. And yet, in a movie or in a stage play, to show the audience what's happening, you've got to do something that's less real.

You've got to have the character shake and you've got to have a zapping sound and you've got to have their bones show through their skin like they're being x-rayed. And then everyone goes, oh, they're being electrocuted, got it. And because we encounter fictitious depictions of electrocution so much more often than real ones, many of us come to believe the made-up story version. And this is all over the place, right? When people have earpieces in, because they're like, you know, a secret service agent, and they're always having to like, they talk by touching the little earpiece in their ear. Obviously, they never actually do that.

Like, you don't need to push it to hear anything. And it gives away that it exists. Exactly. But the fact that it gives it away is why they do it in movies all the time so that we watching go, ah, yeah, yeah, yeah. They have an earpiece in, Roger. You know, they always like they touch it. And that helps us know what they're responding to to the point where that becomes reality

for us. It's not real. It is a ghostly, made up hyper-real vision. And so then when people pretend or talk in conversation about like, I'm a spy, they'll touch their ear. but that's not a thing that spies do at all. That electrocution one, where does that even come from then? Is there like an origin to it?

Because it's such a trope? I don't know. I don't know where it comes from. I mean, I'm sure there's some origin that we could look up, but there are cliches that literally don't have an origin. The website TV tropes calls them dead unicorns. These are overused events in movies that we see now as like satire as parody. Like the film noir detective who says she came into my office and had legs for days.

And like that has never happened straight. There's never been a movie that seriously did that. Same with the villain wrapping a damsel onto the railroad tracks. The dastardly, like that has only ever existed as. a parody of villain stories. So it's a dead unicorn in that it's dead. It's been overused. It's like a dead horse. Like, oh my gosh, this again. But it's a unicorn in that it doesn't exist. It never really existed. It's a completely made up cliche. Another example would be. Oh, I know. Yeah. What about like what about the falling anvil? I, gosh, I don't know.

I mean, how often do anvils fall on people? It would only ever happen in the, I mean, you've got to be lifting an an envelope somewhere on a crane, which does happen. And I guess people just think, oh, that would be like the worst thing to have fall on you. And then suddenly the cartoons are like, yes, that's what should always be falling all the time. I don't know if ever even seen a real anvil in real life on the ground, let alone falling from the sky. I wanted to say that, you know, another sort of ghost that will emerge through media that leads to people misunderstanding history is that the way people talk in period films needs to make sense to us

and if we tried to make it really accurate it could be just really confusing so what I'm thinking of is something like the TV show Deadwood which is set in the old American West but yet they curse they use swear words like the F word and I can't really say all these words but you can imagine what they say or go watch the show and hear them those words are curse words to us

but back then, if people were really going to swear up a storm, they would say things like, go darn it, and things that would just make us laugh. And so the writers of the show had to use modern day taboo words because otherwise we would be like, okay, he just said Spalarky. Is he mad or is he a clown?

And they're like, guys, in 1860, you would have been like, dang, that guy is serious. The other one that I find really noticeable is I can't say I've watched very much of it, but Bridgeton, which is sort of, I mean, it is a very fictional account of what England was like in the 1800s around that era. Forgive me, I haven't got the exact year-right Bridgeton fans. But what seems to happen is rather than any sort of accurate depiction of the use of language, they just say indeed a lot. Yes. Yes, indeed. A lot of words that they would have used, we wouldn't realize we're serious.

Like, instead of saying, I understand that all too damned well. Back in the 1860s, they would say, I understand that too tarnel well. And it feels, it doesn't convey the emotion that it used to. So we have to just use made up unrealistic language. And then we come to think that that's the way things really are. There's a whole suite of these ghosts of reality that appear in media that we come to take to be real. In fact, there's a name for this. It's called the Coconut Effect.

The name comes from the fact that in old radio shows, when you wanted horses to be clopping through, you take coconuts, right? We see this in the Monty Python movie, right? They clop two coconut halves together, and it sounds like hooves on cobblestones. Well, what wound up happening is that in the early days of movies, people were already used to hearing the clopping coconut sound for horses. then in a movie, they would have horses on like a beach walking on sand. And the producers would go, no, this is confusing. I need to hear the clopping of coconuts. And the people who knew stuff about horses said, well, no, that doesn't make that sound on sand.

And they're like, yeah, but the audience expects it now. They think that that's real. So we now need to keep the lie up because otherwise they will be confused. So the coconut effect is when you have to lie in some form of communication, whether it's a movie or a radio show or a book, just to get your point across because to tell the truth would be confusing because we're so divorced from it.

Oh my gosh. So there's all these cliches, right? I don't want to list them all, but there's things like a glitter of light makes a shing sound or a ricocheting bullet makes sparks. They don't usually, but that helps the audience see it. Or when people pull out a blade

and then it makes the sound of metal on metal, despite the fact that there's no other metal there. Where's the other metal? Or if someone pulls a gun out and you hear this sound of like a gun being assembled. And it's like, what the heck is your gun all floppy and on hinges? Like that noise just helps alert audiences to it. And the audiences experience the representation more often than the reality.

So they come to think that that's what's real. Laboratories are not full of beakers of bubbling bright liquids. You know, when you get scared and frightened, does your life really flash before your eyes? these things kind of like are literary devices that then become... Wow. That last one may actually be true. Okay, I have read some about this. Do you know more about it? Okay, so for starters, it's been reported numerous times. But there is a good mechanistic potential reason for this.

If you're in sort of extreme peril, you know, maximum adrenaline, things are looking really bad. it does make sense that your brain would want to rifle through all of your memories to see if there's anything useful. You know, let's say you are about to be bitten by a shark. Your brain is like, I think back to all of those Atterbury programs I watched when I was a kid. Right. Like, is there any of them that say I should punch the shark on the nose? The answer, yes, there is. If you find yourself in that situation.

But this is, I mean, it's quite difficult to study this thing, right? You can't exactly take someone and then put them in extreme patterns. peril in an MRI scanner? No. But wait, this, someone did die during an MRI scan. Did they? Well, I'm not totally prepared to give the details. But yeah, there's a, you can look this up. There was a story of an elderly man who was having an MRI done.

And he died during the MRI. And they kept recording. So they were able to see what brain activity is just before, during, and after the moment of death. It's the kind of thing you could never make happen, but it could happen accidentally. And the brain waves and the brain activity resembled exactly what happens when we are searching for information and remembering. No. Yeah.

Oh, my gosh. I didn't. I'm sorry. I didn't know that. I didn't know that. We don't know that that's what he was experiencing. But this whole meme, the trope of your life flashing before your eyes encourages that sort of interpretation. That whole point about leading up to your death and what your brain is doing before you die

does actually lead me on to the last cognitive ghosts that I wanted to talk to you about. This is something I've found fascinating for such a long time because there is this well-reported effect that when people are coming towards the end of their life, particularly if they're cancer patients and palliative care or whatever it might be, but where they're sort of cognizant, awake and able to talk in the weeks and months leading up to their death, over and over again, patients will report that about a month out from dying, they will have a really, really vivid dream. And these dreams generally involve people who they know, who they've loved,

who have already died, standing with them. There are these key themes that appear. One is this idea of a welcoming committee. This is sort of the most common vision that people have where they're interacting with deceased loved ones, parents, spouses, old friends, whoever it might be, sometimes deceased pets too. They rarely dream of people who are still alive in this very vivid dream that they have.

There's also another theme is the idea of a journey. So patients frequently dream that they're packing bags or they're waiting for a train or they're looking for their passport or preparing for a trip in some way. Another theme that comes up is that patients sometimes dream about past traumas or estranged relationships, but that the dreams always end in this kind of sense of forgiveness or closure. And for decades and decades and decades, there's been reports of this. But the medical establishment were like, no, no, no, it's just morphine.

It's just hallucinations. It's just sort of chaotic. Your brain is oxygen starved. It's something that you just don't worry about it. But the thing about this is that these are not rare. edge cases and they are very different from delirium. So delirium is very chaotic. It's fragmented.

It's kind of scary. The patient's really anxious. They're terrified. But these, they're called end of life dreams and visions. They are super lucid. They're structured. They're almost universally comforting as well.

So about 10 years ago, Dr. Christopher Kerr, who works at hospice and palliative care in Buffalo, he started collecting these stories and he ended up quantifying the experience of 1,400 dying patients over the course of a decade and he revealed that up to 88% of patients, right? Almost everybody has at least one of these dreams before they die

and they typically start with a few weeks before death and then they can increase in frequency and vividness right up as the patient gets closer and closer towards the end of their life. Now in terms of like what is going on here, it's really hard to know. So the thing that we can say is you can put on EEGs

to collect data from people who are in palliative care and there are a couple of theories about why this might be happening. One thing that you do see from the EEGs is that in the final moments or final days and weeks the brain doesn't just fade away. Instead, it actually experiences this surge of gamma waves. And gamma waves, they're the fastest frequency of brain waves, and they're what you get with

intense concentration, essentially. They're with memory retrieval. This is what we've seen with the guy in the fMRI scanner. They're also with conscious awareness. Your brain is sort of lighting up in this electrical storm, essentially, of deep concentration, rendering these, like, very immersive experiences for your, that feel very different from other dreams. The theory about why this might happen, though, other than just the evidence of what's going on in the brain, is that as your organs start failing,

maybe your body is stopping getting all the data in from the outside world. You know, your eyes are failing, your eyes are failing, touch is failing. But your brain is like this prediction engine and it's trying to just fill in those gaps, right? It's trying to construct a version of reality. Another suggestion for this is that, you know, dying is obviously this incredibly traumatic physical event. I mean, the most traumatic physical event there is.

And that maybe as your organs fail, your body is subjected to this really big levels of physiological stress. And so perhaps to protect the conscious mind from the catastrophic pain that's going on, maybe the brain is flooding itself with, you know, endogenous endorphins and sort of free analgesia and trace amounts of what effectively amounts to psychedelics. And essentially, you're sort of, you're chemically sedating yourself in order to to not have to sit there with the physiological pain that's going on. But you know, the true answer about why this happens is we just have no idea. We just have no idea, which I think is very profoundly beautiful, actually, because I am completely open to more spiritual interpretations of this.

I'm not, we've spoken about on this podcast before, I'm not closed off to deeper, more meaningful interpretations of this. But I also think that it really does demonstrate that the most important moments of a person's life as they transition from being alive to being dead, there is still so much that we don't understand when you cannot ask a person, how did it feel to go through that? There is still so many unanswered questions.

So as we've seen in your day-to-day life, you're not alone. There's other versions of you. There's other processes that are separate from your awareness, that are all happening. But even at the end of life, you are certainly not. alone. Your brain makes sure of it. And maybe we're constructing these ourselves and maybe we're constructing them as a society

from our history. Maybe there are echoes of what our ancestors most cared about or we've sort of twisted the things that are real into something that isn't. Yeah, as a mechanism of protection against the trauma of organ failure, of what's happening to the body at the end of life. New presences or brought to us for the comfort they provide. Wow. Well, twice a week, Han and I will be here to comfort you and accompany you on your journey through this reality. I'm glad you listened today. And if you'd like to reach out, you can email us at the rest is science at gollhanger.com. Or sign up to our free newsletter, therestes.com forward slash science.

Thanks for watching and we will see you next time. See you next time.