Forget About It!

This is Hidden Brain. I'm Shankar Vedantam. In Chinese mythology, Meng Po is sometimes known as the Goddess of Oblivion. She polices the land of the dead and has a special responsibility. She makes sure that souls on their way to being reincarnated do not remember their past lives. To ensure this, she prepares a soup with 5 ingredients. Her 5-flavored soup of oblivion produces immediate and permanent amnesia. The soul can now proceed to be reincarnated with no memory of previous lives. There are rare occasions when spirits fail to drink the 5-flavored soup, and when these souls are reincarnated, they become humans who can remember their past lives. Nearly every culture in the world has stories and legends about memory and forgetfulness. Our ability to remember long-ago events is a signature accomplishment of the brain. Our inability to remember important things is an endless source of frustration. Today on the show, and in a companion story on Hidden Brain Plus, we examine the science of forgetting. We look at why our minds hold on to some memories for a lifetime but discard others within seconds. And we answer a question many people ask themselves: is my forgetfulness a sign that something is wrong with me? Forgetting to remember and remembering to forget, this week on Hidden Brain. Support for Hidden Brain comes from Planet Visionaries. Professional climber and environmental advocate Alex Honnold hosts Planet Visionaries, a podcast spotlighting the people tackling climate challenges with real, hopeful solutions. Throughout season 6, Alex brings together extraordinary changemakers for powerful conversations about grit, determination, and the power of hope to fuel our fight for a better future. In partnership with the Rolex Perpetual Planet Initiative, This is Planet Visionaries. Listen or watch wherever you get your podcasts.

Quick question. Do people come to you for answers at work? Maybe you're managing projects, training new hires, or just the one everyone relies on. That's leadership. Through UVA Darden's Part-Time MBA in Rosslyn, we help professionals like you turn real-world experience into recognized leadership credentials without stepping away from your career. Whether you work in healthcare, education, government, or business, This is how you take the next step. Learn more at darden.virginia.edu/ptmba.

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In Charles Dickens' novel Great Expectations, we are introduced to the character Miss Havisham.

Many years earlier, she was jilted at the altar on her wedding day.

She becomes obsessed with this moment and and cannot move on from it. She surrounds herself with reminders of that day, wearing her wedding dress and keeping the clock stopped at the exact moment of her wedding. In so doing, she becomes consumed with sadness. She becomes a prisoner of her own memories. The memories we carry say a lot about who we are and how we see the world. At University College Dublin, psychologist Ciara Greene studies how memories are formed and the roles that both remembering and forgetting play in our lives. Kira Greene, welcome to Hidden Brain.

Hi, Shankar. Thanks for having me.

Kira, I want to talk about something that happened to you some time ago.

You live in Dublin, and it's common for people to get around by bike.

You were riding your bike on the way to a piano lesson.

Can you describe the day for me?

Sure. It was about 3 years ago, and it was a rainy November night. And it was dark, and it was starting to rain, and it was just a kind of cold, miserable night. I was leaving work to go to my piano lesson, and I was in a rush. So, you know, I rushed down the stairs, and I got down to my bike, and I realized I'd forgotten my helmet. So I rushed back upstairs and all the way back up through this very large building, got my helmet, went back down. So then I was running late for my lessons.

Ciara started zipping through the night to her class. The roads were slick.

I was cycling through Donnybrook, which is a kind of a busy road. And on that road, there's a lot of buses, there's a lot of cars, there's a lot of cyclists. And what there There isn't on that part of the road a bicycle lane. The bicycle lane had stopped earlier. So in fact, as I was cycling along, I was weaving around traffic and in around buses. So I was cycling on wet roads, I was going too fast, and you can probably see where this is going, because I skidded on the bike and I skidded right in front of a bus, which fortunately didn't hit me. 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. And I had this very strange experience where I, you know, I've heard of this happening before, but I'd never experienced it where I didn't feel the pain. Straight away, I was lying on the ground, and, you know, you get that moment of shock. And I was lying on the ground, and I tried to stand up, and I couldn't stand up. And I didn't know why I couldn't stand up. And then I looked down, and my shoe had come off somewhere. I don't know where it had gone, but my shoe had come off. But my leg was dangling like, like a kind of like a stuffed sock. The bus driver came rushing out, and he was like, are you okay? And I was like, well, No, I think I broke my leg. But it still didn't hurt. And then it was only a little while later that the pain started to come in. The bus driver called 999, so he called the emergency services. But it took nearly an hour for the ambulance to get there because it was a very busy, wet evening. So they were snarled up in traffic.

As Ciara waited in the rain for the ambulance to fight its way through traffic, She started to experience the kind of pain she had never dreamed possible.

This incredibly sharp, overwhelming, almost electric pain. And I suppose it is because it's nerve pain, essentially. It's the shards of the bone sawing against the nerve. 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.

Around midnight, doctors decided to try and set the leg. They told Keira they would give her anesthesia.

I'm allergic to one of the most common anesthetic. So they said, we'll try ketamine. I'd never had ketamine before. And I'm sure if you are taking this for recreational purposes, that maybe it's a good time if you are starting out in a happy state and you're comfortable and relaxed with friends. But if you're starting out in a state of fear and pain, it was terrifying. It was a really, really terrifying experience. It felt like it lasted about 1,000 years. It was, I, you know, had this incredibly vivid hallucinations. And I, you know, came to believe at one point that, like, I had ceased to exist, that I no longer existed. And I could feel not pain, but pressure, which obviously in retrospect was pressure on my leg as I tried to set it. But it felt to me like I was being compressed through, I felt like I was a train being compressed through a train tunnel. And it was just really, really, Surreal and very frightening experience. And I've had a lot of flashbacks to that experience since. And then after all that, it didn't work. They tried to set my leg and they put it in plaster, but it didn't work. So then they said, actually, after all that, we need to do surgery anyway.

I'm assuming there must have been a very lengthy period of rehab after this much work on your leg, Keira.

Yeah, so I mean, I couldn't walk at all for several months. I was on crutches then afterwards for 6 months, and there was very extensive physiotherapy and rehab and so on. It's 3 years later now, and I do still have pain in my leg. You know, it's much, much better, and I don't limp anymore mostly. I can walk fine, but I used to dance, and I used to do things that I can't do anymore. So, you know, it has had a lot of knock-on consequences. in my life, more than I think— I think previously I would have used the expression, you know, somebody breaking a leg. Oh, you might break a leg. And you think it's, you know, unpleasant, but not a huge deal. But it was quite life-altering in a lot of ways.

I'm wondering how the memories of this event have stayed with you. Have you been able to get back on a bike? Have you been able to, you know, go back to the place where the accident took place? What's happened?

Yeah, so definitely the memories have stayed with me. I'll find myself kind of repeatedly thinking about parts of it. In terms of getting back on a bike, well, of course I couldn't for a long time because I was physically, I was totally unable to. I was in a wheelchair for a while and then I had crutches for a long time. But then maybe 6, 7 months after the accident, I did get back on the bike. I just said, right, I'll do a short cycle from, from my house down to my parents' house, which is not, you know, maybe a few miles. It's not very far. And I did it and I was proud that I did it, but 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. So I never, I still have the bike and I still, want to get back on it, but I've never gotten back to being able to cycle to work, for example.

And when you consider sort of going on the bike, when you consider the inconvenience of parking and you say, maybe I should bike today, what happens in your mind? What does your mind say?

Well, I don't think I've even really gotten to that stage. I think if I was even to think about, you know, would I do it tomorrow? Because I'd have to plan, I'd have to think, well, you know, I'll pack the bike bag and I'll pump up the tires, you know, on the bike. And just straight away, I'm just like, no. It's— there's always a thing. It's particularly— and I live in Ireland. It rains a lot. This is no surprise. If I look out the window and it looks like it might be wet, it might be rainy, the road might be slick, absolutely no way. The thought of getting on the bike is really very frightening. I start to feel very anxious about it. And so even if I'm driving and I see people, you know, cyclists weaving around, I get so anxious on their behalf. What if they slipped? What if they fell? What if they got knocked down? What if they had an accident? But it is, it's absorbing a good amount of my attention.

You mentioned a second ago that what happened at the hospital was also in some ways very difficult, that in some ways you continue to have these memories. Are you still bothered by those memories of what happened when you received ketamine and when you were in the hospital?

Yes, to a certain extent, but then I had a strange experience maybe a year and a half ago, So maybe again, about a year and a half after the accident, I had laser eye surgery. It only takes about 10 minutes, and it's not painful. They put, you know, anesthetic eye drops into your eyes, but obviously your eyes are open for the surgery, and there's, you know, a laser coming in and doing things, and there's a lot of pressure on your eye. And when they're doing that, you see strange things. Like, it looks like kind of like a tunnel. You know, you have that kind of vibe of things looking like things are coming away, shooting away from you, or coming towards you, like they're down a tunnel. And I had this almost flashback to that ketamine experience where I told you it felt like I was being compressed compressed and squeezed down a tunnel. And it was just the visual elements of that gave me this kind of reaction. And I knew that's what was happening at the time. And I didn't have a panic attack or anything. But I was aware that I was like, God, this is like that. And it made it very, very unpleasant. And it felt like a long 10 minutes.

All of us want to have a sharp memory. But Keira's painful memories of her bike accident raise an important question. Is a sharp memory always a good thing? You're listening to Hidden Brain. I'm Shankar Vedantam.

Quick question: Do people come to you for answers at work? Maybe you're managing projects, training new hires, or just the one everyone relies on. That's leadership. Through UVA Darden's Part-Time MBA in Rosslyn, we help professionals like you turn real-world experience into recognized leadership credentials without stepping away from your career. Whether you work in healthcare, education, government, or business, this is how you take the next step. Learn more at darden.virginia.edu/ptmba.

Support for Hidden Brain comes from Progressive. Whoever says saving money is hard doesn't know that new customers who bundle and save with Progressive Save hundreds. Because switching your home and auto insurance is better than cutting down on those iced lattes you love. Switch to Progressive and see if you could save. Get your quote today at progressive.com. Progressive Casualty Insurance Company, affiliates, and other insurers. Not available in all states. This is Hidden Brain. I'm Shankar Vedantam. Most of us wish we could remember things better. We think of forgetting as a flaw. But being able to forget some things can be a blessing. At University College Dublin, psychologist Kiera Greene cites the example of a woman with an unusual ability.

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, which is usually abbreviated as HSAM. And what it is is a really extraordinary memory for the events of your own life. So somebody with HSAM, like somebody like Jill, for example, will be able to tell you in enormous detail about all the incidents of their lives. Like 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 I was hanging out with my friends, and my friend picked me up, and then we went off down to the shopping center, and we hung out outside Claire's Accessories, and my friend was thinking about getting her ears pierced. And, you know, would be able to give you this extremely detailed— Blow-by-blow account of their own personal experiences.

So Jill Price wrote a memoir about her condition, and in the memoir, she tells a story about something that happened to her when she was a child. Tell me the story, Kira.

So she tells the story that her dad used to work as the agent for Jim Henson, who of course was the creator of the Muppets and, you know, the brain behind Sesame Street. And, you know, he would tell all these kind of stories about, you know, to the family and everybody, all about Sesame Street and about Jim Henson and how incredible it was. And at the time, Jill was very young. She was in nursery school. But her dad arranged for her whole class to go on a field trip to Jim Henson's studio where all of the puppets were created. And this, you know, they've talked it up for ages. And this is something, of course, that they were all really, really looking forward to it. But when the day came around for the field trip, Jill was sick. She had tonsillitis. So she wasn't able to go. And of course, being very, very young, she didn't understand that, you know, her father had already committed to this and had already committed to take the whole class with her. So they had to go ahead without his own daughter. They had to go ahead and run the trip. And she was devastated, couldn't understand why he was doing this, taking all of her friends, leaving her behind. And even though she had tonsillitis, so she had a really sore throat, she stood, you know, like screaming at the top of her lungs, screaming at her parents that they were not letting them go. And she says, you know, that it was a small thing in retrospect, but that 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 Muppets Christmas Carol, you're brought back to this moment of not just a rose-tinted view of, oh, haha, this is a funny thing that happened to me as a child, but really like almost being right back there again and feeling it as though she's right there in the moment.

Now, because she has this extraordinary memory, this extraordinary autobiographical recall for things. She remembers very vivid details about what happened that day. She remembers hearing her mother walking away from her and hearing the sound of her mother's heels as they walk away from her. Really, really detailed. Now, what's striking, of course, is that when things happen to us many years ago, in time, our memories start to fade. We start to forget details of it. But that seems like that's not the case for Jill.

No.

So it's actually— it is very unusual. Whereas, say, my memory of a childhood event might be very, very fuzzy, very foggy, I might remember kind of a core detail of that event, but I might not remember how I got there or what happened afterwards or what I was wearing. All of those really, really clear details, those are still very vivid in Jill's memory.

I remember a time when I was running around. I must have been 12 or 13. It was dark. I think I was in a parking lot somewhere. I tripped and fell. I landed very hard on my finger. I broke my finger. It was very painful at the time. But now when I look back on it, you know, I look back on it and say, that's what being a kid was. You ran around, you did silly things, and you had injuries. I no longer remember the pain. I don't remember the details. To be honest, I'm not even sure which finger was actually hurt anymore. But with Jill, because she has this detailed memory, the memory is also painful in a way for her that it's not for me.

Yeah, exactly. So a lot of the time, really what's happening here is that she's constantly reliving these same experiences and kind of perseverating on them and thinking about them. And then it does mean then that, like, you're not able to let some of these things go. So we often tend to think of this kind of really extraordinary memory as being an extra gift, that it's this extra, like, wonderful thing that you have, this skill that you have. And in some ways, of course, it is. And a lot of people who have this condition or, you know, who have this ability think of it as being wonderful, but there are significant downsides. And one other way of thinking about this is that it's not so much a great ability to remember as it is an inability to forget.

So Jill Price doesn't just remember this one childhood event. She remembers other things in her life. Tell me the story about her husband, Jim, and what happened to him, Kira.

So yeah, so in the book, Jill talks a lot. She firstly talks a lot about how she met her husband, Jim. And, you know, they had been— had a kind of a long-distance relationship at first. And then when they met, they had this really, really strong connection and, you know, fell very deeply in love and got married and, you know, lived together and had this you know, from her recollection, had this wonderful marriage. But there was this extremely tragic end to it, which is that only after only 2 years of marriage, when Jim was only 42, he died. He had very severe diabetes, and he suffered a stroke as a result of that, and died as a result after several days in the hospital.

Now, one of the things that's striking is that because Jill had such good memory, she could remember many of the good times in great detail, perhaps in much better detail than many of us could have remembered it. She remembered when she first met Jim, you know, their first night together, what their wedding day was like. She remembered the good times in extraordinary detail, but that also meant that she remembered the tragic end in excruciating detail.

Yes, exactly. And I mean, of course, many people listening might be saying, well, I remember my wedding day as well. But I think the thing is that it's not just these big key events that she remembers. It's also just everyday things. And she'll remember not just our first date was great, but every detail of it in extraordinary clarity. But yes, I guess towards the end then as well, she also cannot allow those terrible memories of Jim's illness and death to fade. 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, 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. The fact of this terrible thing happening is something that everyone would remember. And like, nobody's going to have forgotten that their husband died so tragically. But it's every little detail of it. 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, comes back, and they don't fade with time. You know, we have that, that cliché that time is a great healer, um, and we do tend to see that, that over time our negative memories tend to fade and we tend to hold on more to the positive memories. Now, there are exceptions, but Jill's memory, it really doesn't seem to discriminate. She holds on to all of those details, whether or not they're still relevant, whether or not they're useful to her. Um, she's still holding on to all Kira, say more about this idea.

I think when many of us think about forgetting, we think about forgetting as a flaw. I find myself forgetting things all the time, and whenever I forget things, I'm so upset with myself. And I say, you know, I used to have a fantastic memory, and now my memory is failing me. It's not good. I worry if I have a disorder of some kind. Talk about this idea that in some ways, we get it profoundly wrong when we think about forgetting as a flaw.

Yeah, so I think the first thing to note is that 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. I think a lot of the problem here comes in that when we tend to, make the mistake of thinking that our memories act like a computer system, that we should be able to just file away information and then it will stay in that same place, and then later on we should be able to retrieve that information and we pull it back exactly the same way it was before. And if we had a computer where we went to go and retrieve a file and the file wasn't there, it had been accidentally deleted, we'd be disgusted. That's not what a computer is supposed to do, right? A computer is supposed to retain this perfect record of information as we recorded it. But that's not what our memories do. 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 where we're kind of actively engaging in our memories. We engage in actively constructing and reconstructing our memories, and we change the way our memories are stored in our brains. And part of that process is that forgetting is a kind of a natural sort of digestion process in memory, that we have lots and lots of different events in our lives. And one of the really key things that our memories do and that forgetting helps us do essentially is to identify the gist of those memories. So like, for example, right, like imagine every day probably you eat breakfast, okay? And probably most days you eat more or less the same thing for breakfast. Maybe you eat something different on the weekends than you do the weekdays, okay? But probably you eat the same thing more or less every morning. 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 veridical recollection of exactly 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. Okay? And then sometimes when something a little bit different happens, then we need to be able to remember that. Like, well, we ran out of milk this morning, so I had toast instead. I must remember to go to the shop and buy milk. But most of the time, remembering all of these very repetitive events in our lives in this perfect individual detail, it's actually a really inefficient way of storing information. Instead, we kind of condense that information down and we pull out the gist of what those— of those kind of repeated continuous events. So if you can't do that, if you're not able to kind of essentially leave some of those details behind you, then what you're going to have more trouble doing is identifying the gist, identifying the commonalities among all of those different events.

You know, it's so striking, Kira, because I think when most of us think of memory, not just in our individual lives, but also I think in our social lives, we think of forgetting as almost being something that is bad. I mean, if you think about courtroom settings, for example, we think about people who don't remember where they were or what they were doing at the time of a crime as being potentially suspicious or even guilty.

Yes, absolutely. I think, again, it comes back to that idea that we really have these very unrealistic expectations of what our memories can or should do. And we do tend— we tend to hold, to a certain extent, ourselves, but really other people to very unrealistic standards regarding their memory. And we tend to assume, for example, and there's lots of evidence of this, that in, for example, forensic or legal settings, as you've said, we tend to assume that if someone's memory changes or has gaps in it, that they're hiding something or that they're lying. That if their memory of an event changes, that shows that they're lying about that event and that they can't be trusted. If there's a gap in their memory, maybe they're lying, maybe they can't be trusted, there's something going on. Where in fact, that is completely normal. And if somebody is actually able to give you this perfect, clear description of what happened to them, a lot of that is going to have been essentially reconstructed and rebuilt. So in fact, even the story I told you earlier on about my accident, and in particular, the story I told you about the incident with the ketamine and so on, I was literally under the influence of drugs. I do not have a clear memory of that, but I have a reconstructed memory of how I remember it having happened. That doesn't mean that that's actually necessarily an accurate representation of what happened. It's my reality, but it doesn't necessarily correspond to external reality.

In some ways, Kira, there's a famous Maya Angelou quote that sums up very well what you were just saying.

Yeah, she says that, so people will forget what you said, people will forget what you did, but people will never forget how you made them feel. And I think that really is that idea again of that core aspect of what it is that we're trying to remember from events. So I remember that my bike accident was frightening and terrifying, but, you know, did I cross the white line before the back wheel went out or not? I don't know. I could probably, if I thought about that long enough, I would construct a memory in which I would tell you with certainty that I had, you know, I was on the correct side of the white line, but there's no guarantee that that memory is accurate, okay? But what I can tell you with confidence is how I feel about it. and about that core emotional content of the memory.

You know, I also find it a little amusing that people remember that quote as coming from Maya Angelou when in fact it probably predated her. So the feeling that it was from Maya Angelou sticks in our head more than the facts of whether it actually was from her or not.

Well, yeah, I think that's the case with a lot of famous quotes is that they get, I mean, I'd say 90% of quotes on the internet are attributed Oscar Wilde. And I mean, the man said a lot of things, but he didn't say everything.

When we come back, how evolution has sculpted our brains to quickly forget certain painful events.

If you had that Jill Price-like perfect, vivid memory of that first pregnancy, you might be more likely to say, there's absolutely no way I'm ever doing that again. That was like a horror movie. I'm not doing it again.

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Tell me a little bit about that.

I understand it was a difficult pregnancy?

Yes.

So Gillian was pregnant with her second child, and she was really sick, as a lot of people are. She just had appalling morning sickness, which didn't— was not restricted to the morning. You know, she was just sick all the time. She felt absolutely miserable. And she was saying to me and to her husband and anybody who'd listen how miserable this was. And I remember her telling me, you know, this was just so miserable and it had not been anything like this bad the last time. And what was different with this pregnancy when it hadn't been this bad the last time? And I was listening to this in incredulity and I was just saying like, Gillian, are you mad? It was just this bad the last time. I remember it. We were working together. We were good friends. Your first pregnancy was terrible. You were so sick. You were in bits. And her husband was saying the same. Her husband was saying, like, are you kidding? You couldn't get out of bed when you were pregnant the first time. It was so bad.

You know, as memory researchers, both of you study the science of memory, what did you notice about this? What did you observe about the fact that she seemed to have completely forgotten what the first pregnancy was like?

I do tend to look at everything through this lens, so I just think it was absolutely fascinating how her memory of that had been distorted. And it seemed, what always seemed obvious to me and to Gillian in retrospect, was that her memory had not been distorted in a completely random way. It had been distorted in a very systematic way. And if we think that, you know, about the purpose of evolution at its bare core, you know, of allowing us to propagate our genes, allowing us to reproduce, you know, you could think about that idea that would anybody ever have a second child if they remembered how bad it was the first time around? So that maybe there is an evolutionary benefit or like a functional benefit to misremembering or forgetting some of those negative experiences because it allows us to move forward with our lives. But there is some evidence suggesting that actually this is true, that women who are trying to get pregnant or want to have a second child do misremember the kind of the difficulties of their first pregnancy and of their first childbirth, and that they will kind of dial down the negative elements of that, and that sort of supports them to be able to kind of just even mentally deal with the idea of doing it again.

There's a very popular movie series about a girl named Riley. The premise of the Inside Out movie series is to personify the different processes unfolding inside Riley's head. In one scene, characters are playing different emotions in Riley's head, And they go through her old memories, discarding, you know, unused piano lessons, the names of most of the US presidents, even the names of Riley's favorite childhood toys. So the movie suggests that one purpose of forgetting is a form of decluttering. Is that right, Kira?

To an extent. I mean, it's not the case necessarily that we're actually just taking memories and taking them out and putting them away, but certainly we are kind of combining things together and digesting them in such a way that we're kind of clearing up some kind of mental space. Now, when I say mental space, I don't mean long-term memory storage. We actually do have, you know, quite like the ability to store a huge amount of information. A lot of the time when we talk about not being able to remember something, it's not that that memory isn't there anywhere, it's that we don't have an easy route to access it. So, you know, you can think about, if you think about in, you know, how memories are formed in the brain, they're formed by by synapses forming connections between different neurons. Okay, so we create these networks of connections between different neurons in the brain. 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. 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. So, you know, when we think about that kind of inside out, idea of decluttering the memory. In some ways, yeah, that does happen to an extent that we are condensing down kind of the gist, you know. So out of all this list of US presidents, for example, which ones do I actually need to remember? And which of them can I just collate into a list of, there was a load of other guys who were probably all called Andrew, you know. So I can't— I could not tell you the names of more than about 6 US presidents, you know. So there's, you know, there's ways that we can condense down what's actually going to be really important here.

Talk about some of the emotional reasons we have for forgetting. What is the link between negative memories and psychological disorders like depression?

People on average tend to remember positive events more than negative events over time. We tend to kind of let a lot of the negative stuff go and keep a lot of the positive stuff. So we'll tend to kind of remember that we got better grades when we were in school, Or we'll tend to remember that we were more generous than we were, that we gave more money to charity, that we were more helpful to other people, that we, you know, did things that, you know, will make us look good. And there's some really nice work showing that it isn't just that we do this in a way that it makes us look good to other people, it's also that it makes us look good to ourselves. So, like, for example, there was a really nice study looking at grades where people were asked to remember their grades, but in this study, they knew that the researchers had access to their actual scores, But even so, when people would kind of be asked to retrieve, you know, what were your grades like? And people who had gotten A's would remember them really well. People who had gotten D's did not remember them well. They remembered that they had gotten B's or C's, even though they knew the researchers knew the real data. So it wasn't a matter of, I'm gonna kind of slightly smudge this 'cause, you know, I know there's a reason why I didn't do well there, but they don't need to know. You know they know. So you're actually— your memory is actually being distorted to make you feel like you were a better student than you were, or you were more generous or kinder or whatever.

I understand that in that study, the people remembered their A grades accurately 89% of the time, but they remembered their D grades only 29% of the time.

Yeah, exactly. And this is, I suppose, 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 themselves as And, you know, oh, I was really only ever just average. But of course, this varies with a number of different things. So for example, with people who have depression, that tends to be a little bit less the case. And one of the things that we can think about when we think about how our emotion interacts with our memory is that if we think about how our memories are very associative, okay? So memory, like I talked earlier on about that idea of you're walking down the street and something triggers a memory. A lot of our memory works in the same way in a lot of different contexts. And one of the things that's really interesting from an emotional context is that we tend to retrieve memories that are congruent with our current emotional state. 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. Okay, so this idea that that's referred to as a schema that we have, we create these schemas, these sort of mental frameworks that we use to store lots of information in our memory. One model of depression is that depression is caused by a kind of a negative schema. So essentially a way of seeing the world that tends to characterize things as very negative, both in the moment, but also in terms of how we react the kinds of memories that we're retrieving. So somebody with depression might have more difficulty retrieving positive memories, and we'll 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, you know, 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 that bias is leading you to retrieve those memories in the first place, and then leading you to kind of over-interpret the frequency of those as being representative of your life as a whole.

I understand there was one study which provided people either critical information about them or critical information about another person, but when they were asked to recall what this critical information was down the road, People had better recall for the critical information when it was about somebody else as opposed to when it was about them. And that seems like almost an act of self-preservation here.

Yes. So in this study, they had the participants read descriptions of a person, and the description would include, you know, both positive and negative traits of the person. So they might describe the person as being kind, but sometimes they're a bit dishonest. Okay. And so, you know, all the kind of things that we all are to greater or lesser extent. Everybody's a bit of a mixed bag. And then the participants were later told that these— this is a description either of you, so other people have described you in this way, or it's a description of some other third party, okay, which they called Chris. And then later on, they asked the participants to recall as much of the description as they could. 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. So again, we have this sort of systematic thing where we're likely to remember the part where somebody said, oh, well, you're, you know, she's a very kind person, but not the part where they said, well, she's sometimes a bit sneaky.

So other research has found that we tend to forget more if we cannot do anything about a particular memory. Talk about this research, Kira. What does it find?

Yeah, so again, if we take that same idea of, you know, giving people like a summary of a description of themselves or of somebody else that includes both positive and negative traits, the extent to which people will remember those seems to depend on whether or not people think that those are things that they can change or not. Okay? So if people think that these kind of negative traits are kind of malleable, then, you know, then they're like, okay, well, that's fine. Maybe I still have those, but it's kind of something I can fix. But if it's something that's completely, like, kind of, you know, something that you can't do anything about, like, oh, well, she's a nice person, but she's very, really unfortunately short. And there's absolutely nothing you can do about that. Well, then you're likely to forget that detail coming in. But if they say like, oh, well, she's a really nice person, but sometimes, you know, she has a habit of rolling her eyes, you kind of go, okay, well, I could probably change that. So you could say, oh, I suppose sometimes I do do that, but I'm working on it, you know? So we're less likely to misremember or to forget those details where we feel like there's something that we can change or something we can do about them, and they don't feel like they're a fundamental part of who we are.

What I love about what you're doing here, Kira, is that you're really showing how forgetting is actually very often functional.

Absolutely, yeah. So we really think it is, and I think that's one of our key messages is that, yeah, that forgetting is not just a side effect of memory. It's not memory failing. It's part of what memory is supposed to do, and that forgetting is functional. It helps us to see the gist among different things. It helps us to recognize kind of what's important to us and what isn't. It helps us to to hold on to the things that really support us to live our lives. So like, if we think about not just like what memory is, but what memory is for, that 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. So all of these kind of, what we can't see as memory distortions or memory errors, or sometimes called memory sins, all of these things that sometimes are annoying to us, but actually really a lot of these are things that we have evolved to be able to do, and they are functional, they support us to live, thrive, and survive, okay? So they help us to be happier. And even when you look at, like, say, things like mental health, being happy, having good mental health has huge survival advantages. 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.

Kira and other researchers have found that even our pernicious tendency to remember negative things about our political opponents and positive things about our political allies, even this This likely has functional benefits from an evolutionary point of view, even if it might be bad for democracy.

So we have a lot of work looking at, say, false memories for fake news, showing that people— firstly, that people can very easily form false memories. If I show you a news story about, like, a political scandal that never happened, there's a fairly decent chance that you'll go, oh yeah, yeah, I remember that. And you'll tell me where you remember it from and how you felt at the time and all kinds of things, okay, even though we just made it up. But what we find really consistently is that that is way more likely if that story is congruent with your existing ideological views. So if it's a story that reflects well on your group or reflects badly on the other side, you're much more likely to form a false memory for that than you are if it reflects well on the other team or reflects badly on your team. And again, that is part of that idea where we think it's a part of kind of shoring up those social bonds that we're kind of reinforcing that sense of identity with our social groups. And, you know, being part of a social group is, again, a hugely important survival factor. Humans are social animals. We don't survive well on our own. We live as part of a society, and being integrated in a society and feeling part of a social group is a hugely important part of our psychological makeup.

One practical implication of all this research, Kira says, is that we should look at our own memories with skepticism and our own forgetfulness with compassion. Indeed, just observing how our biases shape what we remember and what we forget can change how we feel about painful memories.

We kind of tend to see our thoughts and believe in our thoughts as objective reality. And sometimes kind of there's a therapeutic technique called defusion that's about trying to take that step back. So To put it simply, it's that idea of to recognize your own thoughts and to reflect on them. So to kind of to see things like saying, for example, you might have the thought, I'm a failure. Okay. You can either say like, well, that means I am a failure, as in this thought has objective reality, or you can take a step back and say and recognize that, no, I'm having the thought that I'm a failure. That actually doesn't mean that I am. I just recognize that I'm having that thought. And just taking that little bit of distance and recognizing that not every thought that you have necessarily holds objective truth, that you can take that distance from them and say, these are, look, observe my thoughts, observe how my thoughts are working, observe the patterns that they go in, and then recognize that.

In our companion story to this episode, In that episode, we look at provocative science that explores how we might do a better job forgetting the past. Can we really put painful memories to rest or prevent them from getting deeply anchored in the brain? Research suggests there might be a sweet spot when it comes to forgetting. Try too hard to forget a painful memory, and you could end up strengthening it. If you're subscribed to Hidden Brain Plus, that episode is available for you right now. It's titled Setting the Past to Rest. If you're not yet subscribed, please sign up at support.hiddenbrain.org. If you have an Apple device, go to apple.co/hiddenbrain. In both places, you can get a free 7-day trial. Kira Greene is a psychologist at University College Dublin. With Gillian Murphy, she's the author of the book Memory Lane: The Perfectly Imperfect Ways We Remember. Kira, thank you so much for joining me today on Hidden Brain.

Thank you, Shankar.

Do you have follow-up questions about memory and forgetting for Kira Greene? If you'd be comfortable sharing those questions with the Hidden Brain audience, please record a voice memo on your phone and email it to us at ideas@hiddenbrain.org. That email address again is ideas@hiddenbrain.org. Use the subject line Memory. Hidden Brain is produced by Hidden Brain Media. Our audio production team includes Annie Murphy-Paul, Kristen Wong, Laura Quirrell, Ryan Katz, Autumn Barnes, Andrew Chadwick, and Nick Woodbury. Tara Boyle is our executive producer. I'm Hidden Brain's executive editor. Thanks for listening. See you soon.

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