The Hidden Power Of Forgetting

What if you could remember everything? Every conversation, every meal, every detail of every day you've ever lived? I would say that sounds incredible, because in reality, I forget names, I forget where I put my keys, I have forgotten entire years of my childhood. Each time I forget something these days, I treat it like a failure, like my brain has let me down. And yes, I start to worry that I have dementia. In this video, I want to take you inside the science of forgetting, because forgetting might be one of the most important things your brain does. Let me explain. At University College Dublin, psychologist Kiera Greene studies how memories are formed. She and her colleague Gillian Murphy wrote a book about this topic. One striking story Kiera told me was about a woman with an extremely rare condition. She can recall virtually every event in her life.

So Jill Price is a woman who's very well known because she has an extremely rare condition that's called highly superior autobiographical memory. Somebody who you might be able to say, tell me what the weather was like on the 30th of September, 1998. And most of us would go, how on earth would I possibly know that? But somebody with HSAM, someone like Jill, would say, oh yeah, I remember, it was really sunny, but the clouds came over at about 3 o'clock. We thought for a while it was going to rain, but then it didn't. And, you know, would be able to give you this extremely detailed blow-by-blow account of their own personal experiences.

Sounds like a superpower, right? But not all of Jill's memories are about idyllic afternoons where she hangs out with her friends. Some of her memories are less happy. Take one memory from the time she was a little kid. Jill's father worked as the agent for Jim Henson, the creator of the Muppets. One time, he arranged for Jill's entire nursery school class to visit the studio where the puppets were made. The kids looked forward to the outing for weeks. But when the day rolled around, Jill had tonsillitis. She couldn't go. Her dad, of course, had committed to taking the whole class to the studio. The studio was expecting to see a bunch of excited kids. He couldn't just drop the plan because Jill was sick. So he decided to go ahead without her. To little Jill, this was devastating. Her own daddy was going to leave her behind And take all of her friends to see the Muppets.

And even though she had tonsillitis, so she had a really sore throat, she stood, you know, like, there, screaming at the top of her lungs, screaming at her parents that they were not letting them go.

Now, you've probably had a meltdown like this as a kid. But here's the thing. You don't remember the meltdown. You don't remember how you felt as you melted down. Jill does. For her, It's like it never stopped happening.

And she says, you know, when every time she thinks about it, she still feels this overwhelming sense of disappointment every time she sees the Muppets. So every time you see A Muppet's Christmas Carol, you're brought back to this moment, really like almost being right back there again and feeling it as though she's right there in the moment.

I have a memory of my own from childhood. I was 11 or 12, running around in an outdoor parking lot. It was dark out. The parking lot wasn't paved and the surface was uneven. There may have been tree roots sticking out of the ground here and there. I tripped, fell hard, and landed on my ring finger. It was incredibly painful. I remember crying. But today, I cannot actually feel the pain anymore. I'm not even sure if it was the ring finger on my right hand or my left hand. This is what we mean when we say that time heals our wounds. What we're really saying is that time helps us to forget. But not for someone like Jill. Now, this is where the story turns really dark. Jill fell deeply in love with a man named Jim. They were married. It was a wonderful relationship. But after only 2 years of marriage, Jim suffered a stroke. He was 42 years old and he died.

And so she describes in really great detail how, when she, you know, her father came home and told her that Jim had collapsed at work and then they're driving to the hospital and she goes through in this just exhaustive detail Every phone call she made to the nurse, and then the nurse is telling her this, and then, you know, all these details of the drive to the hospital, and then, you know, what the doctors were— you know, it was this horrible situation where he was in critical care for days, and then eventually the doctors had to tell her that they had to turn off the life support machines.

Now, no normal person will forget that their beloved spouse has died, but for most people, the details will get blurry over time. Not for Jill.

And she says that even like every time now, years and years later, she can't drive down that road where they drove to the hospital because every vivid little detail of that drive to the hospital is there, it comes back, and they don't fade with time.

So tell me now, do you want to have a perfect memory, to recall everything that happened to you every single day of your life? Can you start to see how our capacity to forget is actually something of a superpower. Let's spend a minute understanding why we remember some things and forget others. The first thing to understand is that most of us make a huge mistake when we think about how our memories work. We have an image of a filing cabinet inside our heads. We pull open a drawer, drop in a folder, and the folder sits there waiting for us to retrieve it whenever we want. Or we see something and it's like taking a photograph. We drop the photograph into a folder that sits on a computer hard disk That's not how our memories work.

Rather than thinking of memory as being this kind of passive process where we just file information away and then it just stays there, memory is actually this really active process.

It's a bit of a mind-bending idea, but lots of scientific research shows that it's true. Our memories are not recollections as much as they are reconstructions. When we remember something, we play an active role in what we remember. We're not just pulling something out of a filing cabinet. Our moods, the situations and contexts in which we find ourselves, they shape what we remember. When you think about it for a moment, you can see why it would be completely impractical for the brain to remember everything that happens to us. Like, think about what you had for breakfast today.

You could, if you think of that computer metaphor, you could imagine that for every single day of your life, you should have a perfect recollection of exactly how— what you ate for breakfast, how you poured out the cornflakes, how you poured out the milk, how you sat down at the table, picked up your spoon, how many bites you ate, how many times you chewed each bite. But honestly, what a waste of time to remember all of these things in such detail. Really, all you really need to know is to sort of condense all of that information into, usually I eat cornflakes for breakfast. Most of the time, remembering all of these very repetitive events in our lives in this perfect individual detail is actually a really inefficient way of storing information.

One of the amazing things our minds do is to throw away most of the details of our experiences and retain only the gist. You generally know you eat breakfast, you like cereal, you don't like eggs. What you ate for breakfast on March 18th, 2024? Completely unimportant. That's why you remember driving to a friend's house but don't remember every traffic light or every turn you took. Your brain retains the gist and discards the rest. Kira says this is why it's a mistake to think that being able to remember something is good and forgetting something is bad.

Forgetting is actually a fundamental component of memory. We tend to think of forgetting almost as the flip side of memory, and that memory is the positive, what we're supposed to do, and then forgetting is the thing that— the accidental thing that happens. But that's really not the case. Like, forgetting is a fundamental element of what happens in our memory processes.

One reason it's easier to remember some things is because there are multiple pathways in the brain that lead to that memory. Think of it like a city grid. There are places in the city that have lots of roads and highways connected to them. And there are places that are out of the way, that have only a single alley leading up to them. The places that have lots of roads leading to them are easier to get to. Your memory is like that too.

If we think about, you know, how memories are formed in the brain, They're formed by synapses forming connections between different neurons. And some of those networks have lots and lots of connections to them. So there's like lots and lots of roads or routes to that particular memory, lots of paths by which we can access it. But some of our memories are kind of— those networks are a little less dense and there are fewer connections to them. So we don't have as many kind of easy routes to them. So they're kind of less easily accessed in a lot of ways.

This is why sometimes Seemingly random experiences can trigger memories. For me, I associate the smell of a certain dish with an aunt who liked to cook that dish when I was a kid. If the memory of my aunt is my destination, I can reach that destination easily when I encounter that smell.

And that's kind of that feeling that sometimes we have where, you know, you're walking down a street and then something— it could be a smell or a sight or just something really small— triggers a memory that you haven't thought of for years and years and years. And that is, you know, it was some memory, some kind of something that was stored in such a way that it had relatively few connections to other parts of your memory. And then, but then something, you essentially accidentally found yourself on the road to that memory and you're retrieving it.

Our emotions help to cement memories, which is why we remember things that are very emotional. Some years ago, Ciara was riding her bike through Dublin on a rainy November night. It was a busy road, with a lot of buses and cars. There was no bicycle lane. The roads were wet. Keira was going a little fast because she was late.

I skidded on the bike, and I skidded right in front of a bus, which fortunately didn't hit me. But it was one of those e-bikes, an electric bike, so it has, you know, the electric power in it, which means it's very heavy, and the downtube is really heavy. So as I fell, my leg got caught in the downtube and snapped my leg in half. It's like if you could imagine a little small bunch of twigs, And then you snap those twigs, they don't snap cleanly. They snap with shards.

The bus driver called emergency services, but the ambulance took nearly an hour to arrive, snarled in traffic on that wet, busy night. Kira lay there, minute after agonizing minute, in excruciating pain. She told me it was the kind of pain she had never imagined was possible.

I've never had the experience before where I would actually scream with pain But not intend to. It was completely involuntary. I'd feel like screams were being drawn out of me against my will. Just incredibly agonizing, like electrifyingly sharp, overwhelming, blinding pain. You know, in a hospital where they ask you, you know, like, how's the pain on a scale of 1 to 10? My previous 10 was now a 6 on the broken leg scale of 1 to 10.

7 months after the accident, Keira got back on her bike to go to her parents' house. But something had changed.

My heart was going like— just going like the clappers the whole time. And I found that I couldn't release my— I had this death grip on the handlebars and I couldn't release my hands from the handlebars enough to turn right. So of course, we drive in Ireland on the left-hand side of the road. So turning left is easy enough. You just stay on the side you are. Turning right involves crossing over the road, you have to indicate. So I did it to prove to myself that I could do it, but it was such an anxiety-provoking experience that I couldn't. I feel there is a thing with a lot of activities like cycling where you need to have a sort of illusion of invulnerability in order to do it. And that illusion was completely shattered, that I knew how vulnerable I was. And there was no getting around that. There was no pretending that this was a safe thing to do. I no longer believed that it was in any way a safe thing to do.

Some people have debilitating memories about injuries. It makes perfect sense, doesn't it? Kira got back on her bike and her brain said, remember what happened the last time you got on a bike? Remember how painful it was? You don't want that to happen again, do you? As we move through our lives, our memories are trying to provide us with information that is helpful. Notice I didn't say that our memories are trying to provide us with information that is truthful. Researchers once ran a fun study that asked people to think back to their school days. In fact, you can try this yourself. Do you remember tests where you got an excellent grade? What about tests where you did really badly? In this study, researchers had access to all the grades that volunteers actually got in school. They found that when people were asked to remember tests on which they got an A and tests on which they got a D, people remembered their A grades accurately, 89% of the time. Their D grades? They remembered those only 29% of the time. Now, the volunteers knew that the researchers had access to their real grades, so it wasn't like they were trying to hoodwink the researchers. Their memories had been genuinely reshaped— weakened when it came to failure and strengthened when it came to success.

It's kind of slightly tied into that idea that everybody is a better-than-average driver. Nobody is thinking of themselves as being a terrible driver. Nobody is thinking of themselves as, you know, oh, I was really only ever just average.

Your brain isn't lying to you. It's editing for you, keeping a version of the past that helps you move forward. And it goes further than grades. In another study, researchers gave volunteers a description of a person, a mix of positive and negative traits. Someone who was kind, but sometimes a bit dishonest. A mixed bag, like all of us. Then the volunteers were told either, this description is about you, as in other people describe you this way, or, this description is about someone named Chris.

And what they found is that when people recalled the Chris study, they recalled kind of both the positive and the negative details. But if the description was supposed to apply to themselves, then they only really recalled the positive details and they were much less likely to recall the negative ones.

When it was about Chris, people remembered everything, good and bad. When it was about them, the unflattering parts were quietly forgotten. Their brains edited the portrait to be a little more generous, a little more forgiving. Now look, I'm not going to tell you that lying to yourself is a good thing. But if we want to understand how memory works, we need to ask what memory is for. You have eyes So that you can see. You have taste buds to taste. Why do you have memory?

Memory isn't something that was just kind of created out of whole cloth. It's something that we evolved. And we evolved, like, all the kind of both the physical and the mental attributes that we have evolved are things that have survived evolution because they offer us some kind of benefit for either survival or for reproduction.

The errors we make are shaped by this evolutionary history. The capacity to forget is not evidence that your brain is faulty. It's a survival tool. In the ups and downs of your life, remembering your virtues and forgetting your flaws, remembering your successes and forgetting your failures— these nudge you toward happiness.

So we know that people who are happier live longer, they're healthier, you know, all of these things. So it's not just a kind of touchy-feely, oh, I'll feel better. It's like these things actually have survival benefits.

It's striking that people with depression often paint a more accurate picture of their lives. They don't just remember the A's, they remember the D's. Their memories are more truthful, but they might not be as helpful. Kira says it's also the case that we tend to remember things that are similar to our present emotional states.

So if I'm currently feeling very happy, I'm more likely to be able to remember events when I was happy. If I'm feeling sad or depressed, I'm more likely to be able to retrieve memories from my life that are sad or depressing. And then what that will mean is that I'll have a kind of slightly skewed perspective of my life, that I'll tend to, you know, view my life as being glass half empty instead of glass half full.

This can create a vicious cycle.

So somebody with depression might have more difficulty retrieving positive memories and will find that they keep drifting into thinking about the more negative side. And then Because they'll do that, then we'll have another cognitive bias that will say, you know, okay, if I retrieve, let's say, 6 memories from my life and 4 of the memories that I retrieve are really sad ones, I must have had a really sad life. And that may well be true, but it can also be influenced by the fact that bias is leading you to retrieve those memories in the first place and then leading you to kind of overinterpret the frequency of those as being representative of your life as a whole.

I'm not suggesting, of course, that all forms of forgetfulness are normal. People can and do develop dementia, and if you worry that you're losing your memory, you should talk to a doctor about it. But the general view that we have, that remembering things is always good and forgetting things is always bad, I hope I've convinced you that that view is simply wrong. In Chinese mythology, Meng Po is the goddess of oblivion. She brews a soup of 5 ingredients that erases all your memories of your life, so your soul can go on to be reincarnated without carrying the burden of a previous life. Yes, it's mythology, but science is now confirming, sometimes the kindest thing a mind can do is forget. Thank you for watching this video. If you want to learn more about the science of the mind, and discover practical ideas that can help you lead a better life, check out the audio version of the Hidden Brain podcast. Just search for Hidden Brain on Spotify or Apple, or visit us at hiddenbrain.org. I'm Shankar Vedantam. See you soon.