Ep99 "Why do brains sometimes make things up?"

Oscar Meyer Wieners or the Berenstein Bears, or the narrative that we tell ourselves about our lives. Welcome to Intercosmos with me, David Eagleman. I'm a neuroscientist and an author at Stanford, and in these episodes we sail deeply into our three pound universe to understand why and how our lives look the way they do. Today's episode is about confabulation. That's when the brain makes something up entirely. But it's

different than lying. Lying is purposeful deception. You know the truth, but you squelch it and make up something in its place. We all know what lying is, but Confabulation is a different beast. It's where your brain cooks up something that is not true, but you believe it entirely. How does confabulation happen? How frequently does it happen? Is it seen not just in patience with brain damage? But do we

all do this to some degree? And what does this tell us about memory and truth telling and the interpretation of your life as a story that sometimes changes retrospectively. So to set the table, picture this Alexander, a fifty eight year old man, sits comfortably in a hospital room, chatting with a neurologist. Alexander describes his morning in detail, the breakfast he had, the news that he read, the friend that he bumped into on his way here. His

voice is confident, the details are specific. But there's a problem. None of it happened. This man, who's a former school teacher. He suffered brain damage years ago. His memory is profoundly impaired. He can't form new memories. Every day is a blank slate, but he doesn't seem aware of this. Instead, his brain fills in the gaps, fabricating a seamless believable reality. And he's not lying, not in the way we usually think

about lying. He fully believes the story he's telling. Why when the brain is faced with missing in from does it sometimes just make things up? So let's zoom in on the issue at the center of all this, which is our memory systems. We tend to think of memory as a recording device, something that stores our experiences faithfully and plays them back on demand.

Some forms of it are dramatic, as in cases of brain injury, which I'll tell you more about, But milder versions happen to all of us, like when we misremember childhood events, when we confidently recall things that never happened, when we rewrite history without realizing it. So in today's episode, we're going to dive deep into the world of confabulation.

We'll explore cases where brain injury leads to striking, almost cinematic fabrications, patients who invent entire days and blind people who insist they can see and split brain patients whose minds generate explanations out of thin air. And next we'll turn the lens on ourselves. How often do we confabulate without realizing it?

So let's take an example. The neurologist Oliver Sacks described a patient that he called mister Thompson. Now, mister Thompson had severe amnesia due to a condition known as Corsicosts syndrome, which is caused by chronic alcoholism, which leads to a deficiency an thiamine, which damages particular circuits in the brain. Now, mister Thompson couldn't form new memories, and yet rather than expressing confusion or admitting that he couldn't remember, he constantly

invented new realities. Every few minutes, mister Thompson would introduce himself as someone different, sometimes a shopkeeper, sometimes a businessman, sometimes a priest. Once someone entered the room, he would confabulate an entire backstory for them on the spot, convinced that he had known them for years, and the moment they left and returned, he had forgotten everything and would create an entirely new identity for them.

as Anton's syndrome. This happens when damage to the visual cortex makes a person unable to see, but their.

and in fact, the room is in total darkness. Anyway, you might ask her to do something like can you turn on the lamp, and she'll reach out with total certainty about where the lamp is, even though there's no lamp there, and of course she'll fail to reach the switch that she thinks is there, but rather than acknowledging that, her brain will generate explanations like, oh, I just miscalculated the distance. And if you ask her to try again, she might say, oh, you know, my arm hurts too

much to keep trying again. Dina isn't trying to lie to you. Her brain believes it it's fabricating reality in real time to compensate for the missing information, and this is a fundamental lesson. The brain prioritizes coherence over accuracy. Now, one interesting feature of confabulations is that they tend to contain a kernel of truth, so Dina might remember a

room like the one she's describing. One hypothesis about confabulations is that their memories in the brain, but they're not built from the right pieces given the situation at hand. So one way to see this is that a patient will confabulate if they're asked a question like where are you right now?

The key surprising lesson here is that your current situation, what you're looking at right now, doesn't just trigger a particular memory, but instead tickles a whole world of possible memories, which then other parts of the brain go through a lot of trouble to squish down as they're looking.

side and confine him to a wheelchair. Now, despite this, Douglas insisted on being discharged from the hospital, claiming that he was perfectly fine. He dismissed reports of his paralysis as a myth, and when he was met with skepticism, he even invited reporters to join him on a hike, a suggestion that was widely seen as absurd. He went so far as to say that he had just been

kicking football field goals with his paralyzed leg. Because of this detachment from reality, Douglas was ultimately removed from his position on the Supreme Court. But what he was experiencing is called a nosagnosia, which is a condition where a person is completely unaware of their body's impairment. People will adamantly deny their paralysis, not out of deception, but because

their brain genuinely believes that they can move normally. Douglas fabricated because of his brain's drive to construct a coherent narrative, and this is wild to witness. For example, imagine you meet a person who is paralyzed on one side and they have a no sagnosia. So you gently ask the person to put both hands on an imaginary steering wheel in front of them. So she puts one hand on the steering wheel, and if you ask her why only one hand, she will insist that both hands are in place.

seek in fabulation in a very different situation. After a person has undergone a split brain surgery.

ask why would anyone ever have that surgery. It was for people with severe epilepsy, where the seizures would spread from one hemisphere to the other. So the idea was that by destroying the road between the hemispheres, you disallow the spread. So neurosurgeons started down this road in the nineteen sixties, but they stopped once they realized that the

surgeries were revealing something astonishing. So let's say someone has just had this surgery, and what you do is you now show a picture, like a snowy scene, but you place that so only the right hemisphere can see that picture. And there are several objects laid out on the table. One of them is, let's say, a snow shovel, and so the left hand, which is controlled by the right hemisphere,

picks up the snow shovel. But when you verbally ask the left hemisphere why the hand just chose a snow shovel, the person will canfabulate. They'll make up a story. They'll say, oh, my hand picked up that snowshovel because I was recently doing some gardening and this reminds me of it. So their left hemisphere has no access to the right hemispher's information, but rather than admitting confusion, it just makes up a story to explain the action. I'll put a link about

split brain studies on the show notes. But what this tells us is that our brain's storytelling function is not just about narrating past events. It's active even in the present moment. It shapes our reality as we go. In all of these cases, from mister Thompson's endless reinventions of himself to the blind woman who insists she can see, to the split brain patients who fabricate explanations for their own actions, the brain is doing what it does best,

creating a cohesive narrative. It just so happens that sometimes the facts don't cooperate. But these extreme cases lead us to a bigger question. If confabulation happens in people with brain damage.

what hadn't he passed away three decades before? Weirdly, so many people had that story wrong.

Here's one. Everyone seems to remember Darth Vader saying Luke, I am your father, when in fact that's not the line.

we'll say the tail has a black tip. Even though his tail is completely yellow, his ears have black tips, and somehow millions of people misremember it as being on his tail. And I'll tell you another version of the Mandela effect that comes about for a slightly different reason. Think about Oscar Meyer Wieners. You've certainly seen the ads and maybe even the Oscar Meyer truck driving around. Here's

the question, how is Meyer spelled? The large majority of people will swear that it is spelled me e y e r, but in fact it's m a y e r. But m e y e r is a much more common spelling, and so we misremember it. And here's another example of that same thing. You may remember a children's book series called The Berenstein Bears. Essentially, everyone remembers this as being spelled barren Stein sti e n, when in fact the last five letters are stai n. It looks

like Baron stain bears. When this has pointed out to people, they generally don't believe this until they go and pull the book off their shelf and take a look.

by your expectations given the particulars of the language. In other words, some ways of spelling things are so much more common that you come to believe that's what you had seen, and like the other versions of the Mandela effect, you really, really are certain that this is how you saw it, And when you see the actual thing written down, it's hard to reconcile the certainty of your memory against

the reality of what is in front of you. Think about all these examples of the Mandela effect, quiz your friends on what they believe and remember, and think of what else you might have misremembered the movies, the characters, the logos, whatever, and a note at podcasts at Eagleman dot com to let me know because I can't get enough of these things. Okay, I think this is one of the most fascinating ways to study confabulation in the individual.

Healthy mind canfabulations which we normally never notice or gain an awareness of. And there's a closely related issue about the way that our knowledge and beliefs can create unconscious distortions about what details we remember. In episode seventy, I told you about a nineteen thirty's study on a short Native American fable called The War of the Ghosts. Participants read the story and then they wrote down their recollection of it immediately after, and then again a week after,

and then again three months after. And as people recalled the story again and again through time, it turned out they smoothed out the details that were inconsistent with their own pre existing knowledge and belief systems. As they recalled the story over and over, it became more consistent with their worldview. As another example, consider the way we explain our own decisions. There are a bunch of studies on this, and essentially, when people are asked why they made a

particular choice, they often canfabulate explanations. Their choices may have been influenced by subconscious factors they weren't aware of, but they'll create a convincing story to explain why they did.

painful memories to make the breakup seem inevitable. In other words, studies show that with romantic partners, if a relationship goes bad, we tend to remember the details of that relationship as more negative than they actually were. If a relationship improves, then we see it through rose colored glasses and remember things as better than they were. There's a sense in which we are always confabulating, turning complex realities into clear stories.

Now all this may seem innocent enough, but in episode nineteen, I dove deep into why This sort of confabulation matters so much when it comes to something like eyewitness testimony, where there's real world consequence. And the issue that comes up here again is not just about the fragility of memory, but the way that we feel so certain about whatever memory gets served up to us, and our memories can

get manipulated by very subtle cues. For example, in one study by my colleague Elizabeth Loftis, participants watched a video of a car accident and were asked a question how fast were the cars going when they hit each other? Others were asked a slightly different version of the question, how fast were the cars going when they smashed into

each other. The result was that those who heard smashed consistently recalled the cars going faster, with some even falsely remembering broken glass despite the fact that none was shown. So memory isn't stored like a video. It's actively reshaped when we recall it, and even a single word can alter what we remember. And Loftis did other experiments showing how false memories can be injected. She showed that people can be led to remember events that never actually happened

simply through suggestion. In one of her Landmark studies. She successfully implanted false childhood memories by asking participants about events like the time they were lost in a shopping mall or the time they went on a hot air balloon ride, even though these things have never occurred, but they were

described as if they had. Over time, a lot of the participants not only accepted these fabricated events as real, but they ended up adding more details into the story and in the big picture, in the criminal justice system, it's been shown with hundreds of studies that you can mislead eyewitnesses by suggestive questioning. You can alter their recollections of somebody's appearance or what precisely happened during the crime, and this problem rears its head every day with eyewitness

testimony in the courtroom. The problem is that memory is notoriously unreliable.

together into a coherent narrative. Small gaps get filled in with assumptions, as we see with the War of the Ghosts experiment. Details get smoothed over as we see with the eyewitness experiments. New information can get inserted even if it wasn't there originally. Over time, the original memory can be completely rewritten, and once we update a memory, we forget we ever changed it. The new version feels like the original. This is why two people who experience the

same event can remember it completely differently. Each person's brain has reconstructed the experience. It's based on their own biases and assumptions and emotions. We've seen how confabulation affects history, like the Mandela effect, how it affects society like Eyewinness testimony, how it affects your childhood memories. And that leads me to always wonder about the small confabulations that we tell

ourselves every day. It's hard to know the answer to this, but how often do you rewrite past decisions, like when you rationalize some suboptimal decision that you made by convincing yourself that you always wanted the outcome you got. This is a post talk confabulation, a way for the brain to maintain a sense of consistency. How often do we misremember conversations? You ever had an argument where you and the other person are one hundred percent certain about what

was said, but your memories completely disagree. I know it's always tempting to say the other person is the one confabulating, but my hope is that after listening to this episode, you might be slightly more willing to revisit this. So if confabulation happens to all of us, how can we ever trust our memories? The answer isn't to distrust everything, but just to develop a tiny bit of skepticism about the stories our minds tell us. Your memory feels real,

but feeling real doesn't make it true. Okay, so we've been exploring how memory is a shifting story. But what does this mean for how we understand ourselves. One thing that's happened lately in neuroscience is implanting false memories in animals, let's say rats. So here's how it works. A team led by Sousumo, Tonogawa and MIT puts a rat in a box and lets them run around to explore it. Then the rats come out of the box and they

hang out, relax. And what the researchers now do outside the box is they reactivate the neurons that encoded the memory of that box. They do this using optigs, So they reactivate those neurons, and now they deliver a little electric shock to the rat's foot. Okay, Now, later they put the rat back in the box a place where the rat had never before been harmed, and the rat freezes in fear, behaving as if it remembered being shocked. There,

even though that had never actually happened. So the scientists were able to create an entirely false experience, one that the rat presumably fully believed to be real. Brains don't store perfect representations of reality, but flexible, rewriteable narratives.

agent whose real memories were erased. This was a very pioneering story that played with the tension between authentic experience and synthetic memory.

their past. Historical confabulation shapes our understanding of events, often to serve a specific narrative. In episode forty one, I talked about the former USSR and how they loved to erase political enemies from photographs. For one example of many, there's a famous photo which proudly captures Lenin and other Soviet leaders in Red Square in Moscow in nineteen nineteen. You can see Lenin and on his left to see Leon Trotsky, and on Lenin's right is a man named Kamenev,

and there's a Bolshevik leader from Georgia in front of them. Now, if you look at a release of this photo some years later, the official Soviet version of the photo, you see that after Leon Trotsky fell from party favor, he was airbrushed out of the photo. In the revised photograph, there's just an empty space where he used to be and Kommenev on Lenin's right has disappeared as well, and the bearded Bolshevik leader never existed.

shaping public memory. History is always being rewritten, and it works because, just like individuals, societies need a coherent story when reality is messy. History gets edited, sometimes consciously, sometimes through the natural distortion of collective memory. So if our memories are fiction, who are We Just think about the way that we tell our life stories. We highlight certain events, we downplay others. We add emotional weight to moments that

might have been minor at the time. We rewrite past decisions to make them seem more logical. We are, at least to some extent, unreliable narrators.

we believe we are. So some argue that confabulation can be useful, but it also has a dark side, which is over confidence. Because we don't realize we're confabulating, we assume our memories are true, and that can lead to serious problems like false convictions, where innocent people are imprisoned because if eyewitnesses who believe they are.

Just because we remember something vividly doesn't necessitate that it's true. So how do we live with this knowledge? How do we best navigate the confabulating brain. It doesn't mean we should distrust all our memories. It just means we should be more open eyed about the situation. So instead of saying I remember exactly what happened, try saying this is how I remember it, But I could be wrong. As we wrap up today's journey through the confabulations of memory,

let's leave with one thought. Our memories shape our lives, our identities, and our understanding of the world. But they aren't perfect records. They are ever changing. They're always evolving, just like us. The fact is we humans are storytelling creatures. We don't just experience the world, we organize it into narrative. In this same way, history can be a story we tell about the past. Personal identity is a story we

tell about ourselves. We began today's podcast with a simple but unsettling question, why do brains sometimes make things up? Along the way we saw that confabulation isn't just a quirk of the damaged brain. It's a part of how all brains function. We are all in a sense fiction writers, Memory is not a recording device. It's a dynamic creative system. Every time we recall an event, our brains reconstruct it, sometimes correctly, sometimes with error, and sometimes in ways that

are more than a little fabricated. The strange part is that we trust our memories with absolute conviction. We trust them in relationships, we trust them in courtrooms. We trust them to tell us who we are. But if memories can change, if our pasts are being subtly rewritten with each passing year, what does that mean for the sense of self?

gaps somewhere. Is this a true recollection or has it been shaped by the stories I've told myself over the years. Don't distrust every memory. Instead, this is just an invitation to approach memory with humility, to recognize that what feels absolutely real might in fact be a creative act.