The science of memory with Charan Ranganath (Transcript)

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ReThinking with Adam Grant
The science of memory with Charan Ranganath
March 29, 2024

[00:00:00] Adam Grant:
Hey everyone, it's Adam Grant. Welcome back to ReThinking, my podcast on the science of what makes us tick with the TED Audio Collective. I'm an organizational psychologist and I'm taking you inside the minds of fascinating people to explore new thoughts and new ways of thinking. 

My guest today is Charan Ranganath, a psychologist and neuroscientist who directs the Dynamic Memory Lab at the University of California Davis. 

Are you a forgetful person?

[00:01:07] Charan Ranganath:
I am a very forgetful person. I know that I am the prototypical absent-minded professor, and so I do have a lot of problems with memory, and so it's probably a reason why I'm interested in the prefrontal cortex as a result.

[00:01:19] Adam Grant:
He's a Guggenheim fellow and the author of the new book, Why We Remember, and he's about to turn some of your assumptions about memory upside down. 

How did you get interested in memory? 

[00:01:33] Charan Ranganath:
I took a class from Danny Kahneman and Danny at that time, you know, wasn't like the Nobel Prize winner, but you know, he's just still as charismatic and smart as ever, and so he was talking a lot about decision making and how people can be irrational. But, a lot of what the work was about is really about how memory leads people to make decisions that are irrational. 

Then, later on, I go to grad school and I'm actually working in clinical psychology, but a lot of that clinical work is seeing patients and testing them for brain damage. And, no matter what was wrong with them, like nine times outta ten, they came in saying they had a problem with their memory, or worse, a relative would bring them in and say they had a problem with their memory. And, the range of things that people were having problems with could be clinical depression, it could be multiple sclerosis, it could be, of course, early Alzheimer's disease. But, memory was affected in almost everything. And, then when I was doing my therapy work in the clinic, I was doing cognitive behavior therapy. But, a lot of that is addressing people's beliefs and in that process of digging into people's beliefs and being curious about it, as opposed to saying, well, you just have dysfunctional beliefs, you end up getting into the world of memory and you end up finding out how people arrived at these things.

And, sometimes you'd end up with these really idiosyncratic stories. Uh, in the book I talk about my first therapy patient who had a driving phobia, and we actually worked behavior therapy on the driving part of it, but he wasn't, he didn't feel like he was done.
And, we eventually got into it and, and he was revealed that he had had this big, you know, he was gay and he came out to his father and got into a big fight with him right before he went out and got into a car accident, got rear-ended by someone. And, so did that cause him to have a phobia? I don't know. 
But, it was really important for him to share that story.

And, so all these things kind of came together in my mind of how important memory was. And, then at the time, brain imaging was just taking off and we had this unprecedented opportunity to change the way we understand memory because so much of the thinking in the clinic was based on ideas that had come out, you know, decades before. 

And, there was really this opportunity to change the way we think about it. And, so I decided to rethink my, uh, career direction and hopped away from what would've been probably a lucrative career in clinical psychology, and instead just jumped on the chance to do some actual neuroscience research. 

[00:04:12] Adam Grant:
I was stunned that we're wrong about the fundamental function of memory, that the point of memory is not to be able to recall the past, which just sounds so counterintuitive. Talk to me a little bit about why, in fact, my memory is not about remembering. 

[00:04:27] Charan Ranganath:
If you just take the most basic finding in memory research, like go back to when people first started quantifying memory, one of the things that we know is, is that people forget most of what they've tried very, very hard to learn. People forget that within 24 hours. And, to this day, no one has been reported as just somebody who can truly remember everything. There are people who remember a lot of detail about certain aspects of their experiences, but nobody remembers everything. 

So, right off the bat, we know that the expectation that we're supposed to remember everything from our past is just wrong, right? So, then you ask yourself, okay, well what is memory for? And, you know, 'cause by definition, if something is in the past, it's over with. So, from an evolutionary perspective, why should you even care about it? 

And, the answer is of course, because some of the things that we remember from our past are useful in the present and the future. And, more and more, as my career started to get into deeper and deeper in memory, I became less and less interested about seeing what goes on in terms of recording the past and more about how we use memory in the here and now, and how memory is used to anticipate what could happen in the future to generate predictions and plan and so forth. 

And, if you see people who have a memory problem, the reason why they're so upset by that, the reason why it just gets to the core of them, is in part because you can't function with a memory problem and you can't function because you're constantly getting lost in the middle of conversations. You're physically getting lost when you're trying to move from place to place. 

You feel mentally disconnected in time and space. Imagination, planning, you're kind of stuck in this present time and there's some positives to that we can get into, but there's a lot, it's deeply disturbing too. 

[00:06:25] Adam Grant:
One, one of the things your work has left me wondering is, is forgetting actually a good thing, um, or is it, is it sometimes a useful thing? 

[00:06:35] Charan Ranganath:
I would definitely say the answer is yes, and I think most scientists in the field of memory would agree. As long as you're remembering the right things or the things that you need, forgetting is good. And, and the analogy I give is, is that as we've done more computer models of memory where we've tried to figure out reverse engineer the brain, one of the things that you start to realize very, very quickly is there are design principles. I think our brains are designed for quality over a quantity, and you could see this in the brain from the most basic, basic level of, I feel like I'm seeing everything in front of me, but, really, I'm only attending to a small proportion of what's actually out there. 

And, the parts that I'm attending to when I'm moving my eyes all over the place, I'm getting high resolution, but little chunks of the world and I'm using my knowledge and I'm using what's happening in the present and putting it all together into a picture in my mind of what's in front of me. Right? And, so right off the bat we're saying, hey, we get a little bit of information, but it's as high quality as possible and then we use that economically to get meaning and to really generate information about what's useful.

So, kind of a long answer to your question, but yes, I think forgetting is a very useful part of that because there's so much that we don't wanna haul around.

[00:07:55] Adam Grant:
Well, I think higher on that list of things we would like to forget are, you know, are unpleasant memories, embarrassing moments, for example, and I want to talk in part in our conversation about how to improve our memory, but you're making me wonder about how to improve our forgetting. So, maybe let me, let me give you an anecdote, uh, that I think captures a, a little bit of my curiosity around this.
I remember in my first year of grad school, I had a classmate who was enamored with some work done by an en, an eminent psychologist, Dick Nisbett. And, she read four or five of his papers. They'd been published about a decade earlier and she got a meeting with him. She sat down and she started asking him questions about the papers. And, he gave her this blank look and he couldn't answer any of her questions. 

And, finally she said, well, you know, I really wanted to talk to you about this body of work. And, he said, oh, that, that finished eight years ago. I've purged it from my memory. And, I was so, I was so troubled by the idea that you could actively purge something from your memory. It never occurred to me that you could intentionally forget something. 

So, is this, is this a thing? Can you do it? If so, how?

[00:09:06] Charan Ranganath:
Yes, it is a thing how big of an effect it is in the real world, we just, we don't know. One of my friends and colleagues, Mike Anderson, who's now in Cambridge, has basically made his career studying this and he's very passionate about this idea of voluntary forgetting and he's got a good body of evidence to show that that same kind of control that we can exert to inhibit, say, a movement, we can inhibit the retrieval of a memory.
And, so the question is how big of an effect that is and how permanent it is. But he's, it's definitely been shown that you can inhibit the recovery of a memory and make it harder to access and maybe even change it to make it blurrier.

[00:09:47] Adam Grant:
So, how, how does this inhibition work? If, if I wanted to forget a memory, how would I do it? 

[00:09:53] Charan Ranganath:
Well, according to Mike's research, it's literally as easy as telling people don't think about it. There is a school of thought that says, if I tell you not to think about something, you will actually think about it. 

[00:10:04] Adam Grant:
Yeah. I'm immediately thinking about the, the Dan Wegner work on the, the white bear effect and the ironic effects, effects of, of thought suppression. 

So, you tell me not to think about something and it becomes more active in my mind. 

[00:10:16] Charan Ranganath:
It’s not like he's just saying, never think about this terrible memory, but you're sort of like actually, kind of, getting people in the process of retrieving it, then squashing that process. That's a big theme that connects many, many areas of memory research is the act of remembering in and of itself changes the memory in certain ways, and you can inhibit it to kind of squash it, especially squash some of the details, or you could enhance it and make it more accessible later on. So, you might find that a story that you tell once or twice, it's just easy. It comes to mind so much easier the more you tell that story, right? And so that's a case where recovering a memory can actually strengthen it.

You can also modify it. And, so maybe the more times you tell the story, you embellish it here, you embellish it there, and then it becomes hard to tell the difference between the original thing that happened and all these embellishments that you threw in for different audiences. 

[00:11:10] Adam Grant:
Well, and I think this is why people often run into trouble with stories they've retold over and over, over a period of years. They haven't realized how the story has morphed as it's been recalled. 

[00:11:22] Charan Ranganath:
There's work on what's called audience tuning effects. I've got a memory, but I shape the perspective of that memory so that we can come to kind of some common ground. 

Then you tell me something back and through this interaction that's no longer my unique experience, it's our experience and a little bit of you is being injected back into this memory again, right? And, so what happens is, is then we tell these stories to different people and we tune them up to different audiences and then they react. 
And, that changes the way we think about that memory.

In some cases, it can lead to some real distortions and introduce all this new junket to it. But, one of the positive sides is it can really change your perspective. You know, one of my favorite quotes from Star Wars is Ben Kenobi says, “Many of the truths we cling to depend on our own perspectives.”

And, it really is true that we often confuse the data in memory that is little bits that come up that are representative of what happened. With the theory that we generate, which we use to say, well, what really happened? 

And, that story is heavily influenced by perspective. This is one thing super powerful about psychotherapy in the clinic is that's what a therapist should be there for, is not just to say, oh, I totally agree with you, but to listen to you and reflect back from an alternate perspective. Or, maybe just encourage you to rethink from an alternate perspective.

[00:12:49] Adam Grant:
We're not just helping you process the memory, we're actually reconstructing it.

[00:12:53] Charan Ranganath:
When many scientists have looked at brain activity, when people, um, recall past events that they've experienced, it actually looks remarkably similar to things that they imagine that could happen in the future. And, there's a whole line of research that's just fascinating about how hard it is for people to tell the difference between memory and imagination, even. 

[00:12:43] Adam Grant:
I read some research recently suggesting that when people recalled traumatic memories, it activated neural networks associated with current experience. People were almost reliving them as opposed to recalling them. Talk, talk to me about that.

[00:13:34] Charan Ranganath:
So, sometimes what happens is people get this feeling that's so strong, they feel like they're reliving the event, even though many of the details are, actually, missing. 

And, that doesn't mean it's a wrong memory, it just means that our feeling of re-experiencing so often tied to that visceral playback as opposed to the actual information content. 

[00:13:57] Adam Grant:
Let's talk about how to improve memory. My basic read of a couple decades of memory research as an outsider is if you wanna remember something you read, you should not spend all this time rereading it or highlighting it. 

Instead, what you want to do is let it consolidate by taking a break, ideally in a quiet place, quiz yourself so that you can identify what you remember and what the gaps are, and then retrieve it repeatedly to make it stick. I like to do that by, by sharing it, telling somebody else about it so that there's, there's now like there's an inter an interaction or an exchange that it's part of. 

Um, how does that track with the science and what am I missing? 

[00:14:40] Charan Ranganath:
There are different tricks for remembering different kinds of things. So, the trick that you might use for memorizing someone's name might not be the trick that you use for memorizing Spanish vocabulary words or something like that, right? 

So, that, that's just a little bit of a, kind of a disclaimer. But, a lot of the things that you brought up are kind of something that I would subsume under the term error driven learning. When we are struggling to learn something, you're actually going to retain that information better than if you're not. You know, spacing out your learning experiences, testing yourself, all of these different kinds of techniques, you're basically putting a stress test on the thing that you initially learned.

And, so in our computer model what happens is, is that every time you recall something, you relearn it, right? That's a new way of reshaping the memory. And, so what happens in our computer models is you actually reshape some of the connections involved in that memory so that you remove some of the weak parts of the trace and you add some of the good parts. 
You just reinforce those, and so it's just more accessible later on.

On one hand, this is counterintuitive because it's like, well, surely, giving yourself the right answer, just memorizing it over and over should be better than producing a wrong answer and then correcting yourself. But, I mean, nobody who's like rehearsing for a play just reads the lines over and over and over again and then says, okay, I'm gonna do it perfectly when I go on stage. Right?
It's you actually give yourself the chance to screw up the lines and then go back and you figure it out. Right? It doesn't have to be making a mistake. It's really revealing the weaknesses in your memory and then going back and repairing those weaknesses. 

[00:16:26] Adam Grant:
That definitely resonates. So, let, let's take a personal example here. 

When I first started teaching, I was teaching a, a week long intensive course, and I had about 225 students across three different sections, and there was no way I was gonna get to have a meaningful personal interaction with every one of them. But, I wanted to make it clear that I cared about getting to know them. 

So, before the first day of class, I memorized all their names and had them put their name cards down, and then I went around the room and named them. And, it was pretty time consuming to memorize all the names with all the faces, adding the layer of some people didn't look like their pictures. And, also I had three different students at different times of day sitting in the same seat, and sometimes I would mix them up, so I, I, I think the first time I did it, I got all the students right in one room of 75, but I missed a couple in another. And, I'm curious about how I can improve.

My, my basic, my basic memory technique was I would go through and basically memorize five names and just repeat, kind of, the names in order over and over again. 

And, then I would quiz myself on those five. And, then once I got it, I'd add more and, and kind of brute forced it.

And, I got some advice that I should try the memory palace, which I haven't. I'm curious to get your, your reactions and recommendations. What do you think of my technique and how could I make it more efficient and also more effective? 

[00:17:50] Charan Ranganath:
First of all, I do like the technique and, and I admire your willingness to go through that trouble because it's like you are going to have some forgetting and you're revealing those weaknesses. 

[00:17:59] Adam Grant:
Well, actually this is one of the memories I wanna forget is when I called a student by the wrong name. This, this is 15 years ago and it still bothers me. 

[00:18:08] Charan Ranganath:
Well, you know, see this is the…

[00:18:08] Adam Grant:
And to your point, I still remember that student's name.

[00:18:11] Charan Ranganath:
Exactly right. So…

[00:18:12] Adam Grant:
Michael, I'm really sorry.

[00:18:16] Charan Ranganath:
Well, so to be fair, you've probably met a lot of people named Michael. Right? And, so it's not that you can't remember the name, Michael. It's that you can't associate it with that face because that name has been attached to so many other people you probably met and know, right? 

The memory palace is kind of a fancy way for those people who might not know it. It's basically like same, take a place that you know very well, like your childhood home or something like that, or you could make it up and create a little palace in your head. But, if you take, like, your childhood home or something like that, and you imagine, okay, I'm going to take Michael and I'm gonna visualize Michael in room number one, and then I'm gonna walk over to room number two and say, okay, I'm gonna visualize Harriet in room number two. 

So, you go around like that. And, so what happens is just by virtue of taking advantage of that structure, that you know, this place and putting these things that you're trying to memorize in different places, you can restrict the degree to which these memories compete with each other, and you give yourself an access point that allows you to reach them again. 

That's one way of doing it. I don't particularly like that way for things like names and faces though, because I feel like that's better for memorizing kind of arbitrary things that have no meaning. You know? I think for someone like you, if you're going through the trouble of memorizing each person's name, it's 'cause you want to get to know these people. 
Right? And, so what I would suggest is you get a fun fact about them or you get something like biographical about them that's meaningful.

One of the weird things about memory is if you give people more things to memorize, they're typically bad at it. But, if you can make all those things play well together, now it gives you something that it's easier to remember. 

So, for instance, it's like if I had just met you on the street and I knew nothing about you, it would be really hard for me to remember your name and face, right? But, I've heard a lot of your stuff talking previously and I've seen, you know, and, uh, read stuff, and so it's like coming here, I already had a schema, so to speak. 

I already had knowledge and so all I have to do is tack on your facial details to that knowledge that I already had, and it's much easier, you know? And, so the more you can get some, kind of, a unique factoid about the person, some, kind of, knowledge that you can tack it onto, it's no longer an arbitrary piece of information. 

Recommendation two would be repeat the name once just to make sure you got it. Then, randomly revisit that name later on so you space out those attempts that you had.

So, it's like, rather than saying Michael, okay, Michael, Michael, Michael, let me move on. I would go two or three to, you know, go back, go through the entire list, and then start revisiting these people again and say, okay, so I know I probably have already lost some of these names and so, you know, I'm just gonna try again. 

So, you, and do it in a different order so that it's kind of random. But, the more you space out these attempts, what happens is your brain's gonna struggle more and more because the time between those things has passed. And, so you have to change the memory more each time. And, at least in our simulations, when we simulate this in computer models of the brain, what happens is you start to cut out the things that are specific to seeing Michael at this time in this place, and it becomes more just about him as opposed to this one moment in time when you heard his name. 

[00:21:47] Adam Grant:
It's, it's a little different from what, what I've done historically, which is I've done spaced retrieval more, I'd finish memorizing a whole class, and then I'd put it away for half an hour and then I'd come back to it. 

And, you're saying I can actually do that even within the class.
[00:22:00] Charan Ranganath:
And, I think also giving yourself that chance to make mistakes, people often blow that chance because once they kind of, once they go, oh, I couldn't remember the name, they go off to the races in their head, and rather than giving themselves the opportunity to just solidify that memory or even go further, be more curious and, kind of, get more knowledge about that you can use to kind of repair that memory. 

[00:22:22] Adam Grant:
This is very familiar for me. I've always been good at remembering facts and details about people, but not where I parked my car. I actually once was wandering in a parking garage for two hours 'cause I lost my car. We did a WorkLife episode a few years ago on how to remember anything and, and Josh Foer was one of the guests.
We talked a lot about his process of becoming a memory champion. 

[00:22:46] Charan Ranganath:

[00:22:46] Adam Grant:
And, I guess I came away from that discussion really appreciating the importance of place in memory, which is something you were stressing a moment ago as well. 

[00:22:54] Charan Ranganath:

[00:22:54] Adam Grant:
And, I don't think I fully got it until I landed at O'Hare Airport. 
Have you been there?

[00:23:00] Charan Ranganath:
Uh, yeah. Yeah. Yeah.

[00:23:02] Adam Grant:
Were you there when they gave every floor a sports team?

[00:23:05] Charan Ranganath:
Yeah. Yeah. Yeah.

[00:23:07] Adam Grant:
It was so helpful. I, I immediately remembered that I parked on the Chicago Bulls level.

[00:23:11] Charan Ranganath:
Yeah. Yeah.

[00:23:11] Adam Grant:
And, I can picture Michael Jordan and I don't need to write it down.

[00:23:14] Charan Ranganath:

[00:23:15] Adam Grant:
And, it made me wonder why, first of all, why does every airport not do this? 
Second of all, why is the world organized to make it harder to remember things?

[00:23:24] Charan Ranganath:
That's a great question. I suspect it's because people just assume it should be easy. There's this overconfidence that they have that if you fail to remember something, it's your fault. It's like parking your car, there's so much competition there that it's like your memory's being eaten alive by all these different other memories that, that are fighting to get out there. 

And, so as a result, it's just really a very hard problem and I think a lot of what goes on is institutions and people don't appreciate the difficulty of that problem. But, getting back to this kind of institutional thing, it's really interesting and I think it speaks to this question of how much I look back on education and our attitudes about education. 

And, again, it's so much of like we grade people on how good they are as opposed to how much they've learned. And, I think that's such a wrong attitude to have that it's like this, kind of, the idea that somehow learning should be effortless. And, if you're putting effort into it, that's 'cause you're not smart or something, which is just like absolutely absurd. 

I always tell my students, if you don't have an apostate complex, you're probably not working hard enough. And, what I mean by that is that it's, like, if you don't feel like you're outside of your comfort zone, you're probably not learning enough. And, for me, in my field, if you're not learning what, what's the point of being a scientist? 

[00:24:57] Adam Grant:
Okay, this is a good time for the lightning round. What is the worst memory advice that people give and receive? 

[00:25:03] Charan Ranganath:
Yeah, yeah. Probably the biggest bad advice I would say is people saying that you should try to repeat things over and over again in your head, and that's a good way of memorizing.

And, then lifestyle wise, trying to go for like multi vit-, I mean there are, multivitamin do have some good effects, but just in general, searching for supplements and crossword puzzles to improve your memory as opposed to bigger lifestyle changes you can make. 

[00:25:29] Adam Grant:
Do you have a favorite memory movie? My runaway first pick is Memento.
[00:25:35] Charan Ranganath:
My runaway first pick is also Memento. 

It was just the best memory movie of all time. But, I will say my favorite memory TV show now is Severance, because Severance…

[00:25:47] Adam Grant:
So good.

[00:25:48] Charan Ranganath:
…is just the deepest meditation on the mind memory and identity that I've ever seen. Um, just this idea that people could be in a workplace and divorced from all their memories outside of this workplace, and they are different people because they're trapped in this context and that context dictates their sense of who they are and it dictates what they can remember and, and it's just this fascinating idea of, like, how, because we have these things in our head anyway that are these contexts that, sort of, block off what we can remember and what we can't. And so yeah, I just love that show.

[00:26:28] Adam Grant:
I thought the season finale, season one was probably the best season finale I've ever seen of a show. And, it did shatter some of what we typically think about the, the normal segmentation of life domains. 

My, my colleague, Nancy Rothbard, uh, has consistently found that if, if you're somebody who likes to segment work in life and maintain a, a border between them, you tend to be happier, uh, than if you're an integrator who's constantly blurring boundaries. I think Severance took that too far. 

[00:26:57] Charan Ranganath:
My parents are both just having a difficult time transitioning into retiring, but they're transitioning and the difficult part for them is it is kind of a death, you know? 

It is such a change in life that you're letting go of that context in your life. You know? Of course, it's not really gone 'cause they've even had the severance procedure, but it's just this fascinating idea of how if you lose a memory for something, it's as if this part of you has died. 

[00:27:23] Adam Grant:
This also reminds me of another classic Dan Wegner finding around transactive memory that one of the reasons breakups are so hard on people is that you've outsourced some of your memory to your partner and they've literally walked away with some of your memories and also your ability to recall like, okay, how do I pay those bills? 

And, where exactly is this location that I don't ever drive to. And it, it seems like, um, somebody literally walking out of your life, also taking part of your memory ends up stealing some of your identity. 

[00:27:57] Charan Ranganath:
Yeah. Yeah. And, and it's like, there's always something there to remind you. The most mundane things that, uh, that you'd be doing now are reminders of what's missing from your life. 

[00:28:07] Adam Grant:
The, the thing that drives everyone I know crazy about memory is the tip of the tongue phenomenon. You had something, you were about to say it, and you've just lost it. Can you give us any guidance for how to solve that problem when you run into it?

[00:28:23] Charan Ranganath:
There's a number of different causes for why that happens, but one big one is you get stuck on the wrong answer because we have these biases to keep producing what's easy. 

Once you get the wrong answer, your brain is kind of primed to keep producing the wrong answer, and you have to overcome that. And, so sometimes changing your context and just changing the subject and saying, I'll get back to it, it'll come to me, is the best thing you could do because once you then go back, you're no longer primed to keep pulling out that wrong answer. 

[00:28:57] Adam Grant:
What is the question you have for me? 

[00:28:59] Charan Ranganath:
What is the latest thing that aroused your curiosity? 

[00:29:04] Adam Grant:
Earlier today, I was running on the treadmill. I opened up Netflix and it recommended Breaking Bad. And, all of a sudden I found myself wondering for the first time, why does everyone love this show? What is it? And, I am now in episode in, and I totally get it. Late to that party. 

I learned that it's fascinating to watch a good person do a bad thing. And, the opposite is probably true too, and that it's also interesting to watch someone change right before your eyes. 

[00:29:36] Charan Ranganath:
One of the things we find is that when people's curiosity is triggered, you can, actually, boost the ability to learn and retain things that are happening in the moment. 

So, we, and we found when we look at areas of the brain that are involved or processing reward information and, actually, processing dopamine, the neuromodulator, what we find is, is that those areas activate in proportion with not getting an answer to a question, but getting the question itself and getting that boost of curiosity. 

And, what's really cool is we have this job where we're constantly confronted with things that challenge us, and it's the gap, the prediction error is what we call it scientifically, but it's really the gap between what you thought you knew and what you're actually confronted with that can trigger a lot of those feelings of curiosity. 

And, what happens is it energizes you and it gives you this itch of like, I gotta get more information. But, what's fascinating is I also find it's uncomfortable. I hear this all the time in scientific discussions where somebody hears something and if there is a truly new idea or something that's truly different than the norm, half the people say, well, it must be wrong and half the people say, well, we already knew it. 

[00:30:50] Adam Grant:
I have long thought that when you share a finding and half the audience thinks it's completely counterintuitive and the other half thinks it's completely obvious, you're onto something intriguing.

You reminded me a couple minutes ago of George Loewenstein’s work on curiosity gaps and how he and the Heath brothers describe this, this gap between what you currently know and what you want to know as like an itch that you have to scratch. 

That's a great impetus for learning it, it obviously makes things more memorable. I sometimes worry that we're creating those gaps inadvertently and sometimes in ways that are harmful. So, the, the context that comes to mind immediately is when a judge says to a jury, disregard what you just heard. And, I think to myself, well, well, aren't you drawing attention to that? 

And, then, aren't you also making the jury wonder like, well, what, what is it about that that was problematic for me to hear? And, then, do they go and pay more attention to it? Is that, is that a problematic instruction? Should we be approaching this differently? What, what would you say is a memory expert?

[00:31:57] Charan Ranganath:
I think you're right that it's like if the first thing that may come to mind is this curiosity of, well, what's so bad about it that I can't actually remember it. 

And, so I think without a reason, people may not be compliant because a lot of this is not about like what, you know, the message itself, but what people do with it. And, and that's like the story of memory for so long. I mean, behaviorism was all about, people are just stimulus, stimulation responses. But, uh, since then, I think the, it's pretty clear. 

It's not about like laws of here's how you memorize things, but rather what you do with the instructions. That's, that's super important. 

[00:32:36] Adam Grant:
So, we wanna tell judges to be really clear about why it's important to disregard.

[00:32:40] Charan Ranganath:
Yeah. Yeah, exactly. Exactly. Yeah.

[00:32:43] Adam Grant:
Okay, good.

[00:32:44] Charan Ranganath:
And then, and then say, don't think about it. 

[00:32:47] Adam Grant:
Well, you can't tell me what to think.

[00:32:50] Charan Ranganath:
That's true.

[00:32:51] Adam Grant:
I'll show you. 

[00:32:52] Charan Ranganath:
Yeah, yeah, exactly. But, you don’t want to think about this.
[00:32:55] Adam Grant:
It's so easy now to outsource our memory to technological tools. Uh, how many people actually know their friends and family members' phone numbers anymore?

How often do we know that we can run a Google search or now use a generative AI tool to look something up that we used to take pride in, in having stored in our own brains?
Uh, I'm, kind of, in two minds about this. I think on the one hand it seems like it frees up cognitive resources. On the other hand, I worry that like there, there's real knowledge lost. Where do you 
come down?

[00:33:28] Charan Ranganath:
I think with most technology, just throughout the history of humankind, it's not, it doesn't come down so much to the technology, but how we interact with it, that's the issue.
I'm a huge fan of outsourcing certain kinds of tedious memory tests to phones and devices, right, because it's like, I don't have a photographic memory, but my phone literally does. So, why not take a picture of where I parked my car, but as opposed to, actually, try to memorize it.

But, I think there's two ways in which we really hurt ourselves. 

We live in a culture of documenting things for social media, and so it's like you take pictures of things all the time and people will post it and as soon as they post it, they never go back to the pictures. But, the problem is when they were taking the pictures, they were never there in the first place, right? 

So, you'll go even go to concerts and people would be like taking videos with their phones and they're just recording the whole thing mindlessly, but as a result, they're never there. And, so they're depriving themselves of the ability to form a rich memory in the moment and they're not even taking advantage of that reminder later on to, kind of, recall it over and over again. 

You can actually use photos in a way to help your memory by grabbing what's distinctive or unique about this time and using your focus on the moment of like, Hey, this is curious. This is weird. Let me grab a picture of this. 'Cause those are the things that will be serve as great reminders later on. As much as we'd like to think the technology is really gonna help and adapt to human thinking, I feel like humans are much more likely to adapt to the thinking of our technology. 

The brain is always trying to optimize and produce things more fluently and easily, and so even things that are just words or sentences will be more or less accessible just through certain kinds of repetition. We start to shape our language around what's suggested to us as is true with music, too. You see like algorithms that feed us particular things and it sort of deprives us of the opportunity of those weird experiences that we can have that opens us up to something really new. 

[00:35:42] Adam Grant:
You talked a minute ago about having novel experiences and I think that speaks to something you captured that's really powerful about the pandemic. So, there's this paradox when, when I think about 2020 and 2021, which is a lot of people felt like time stood still and they took forever, those two years, but also people can't remember a thing that happened during Covid. 

What’s going on there?

[00:36:10] Charan Ranganath:
It was fascinating because right around that time we were studying this phenomenon in our lab called event boundaries. If you think about time, it moves continuously, right? But, when we remember our experiences, we remember them in terms of events. So, you remember a conversation that you had with somebody, not the word in the conversation that happened right before you walked out the door or whatever. 

Those event boundaries are kind of like the little organizers of our experience. Memory's all about having distinctive experiences and just by virtue of our daily schedules in normal life, we go to different places and that puts very big event, it's one of the biggest ways to create an event boundary. 

So, what's interesting about the pandemic is we had the opposite. You're sitting in front of a screen all day, interacting with screens all day. You're in the same house. You are doing procedures that are very, very similar to each other. And, so what happens is over the course of a day, it feels like your event boundaries have blurred into almost nothingness. 

And, so there's a real value in changing your context, seeing different people going to different places, if nothing else, just to give you that distinctiveness and memory. 

[00:37:25] Adam Grant:
So that, that sounds like a, an antidote to the Groundhog Day effect. 

[00:37:30] Charan Ranganath:
My family, when I was growing up, we didn't take a lot of vacations, but you know, in the last few years, I should say, I've really been very mindful of taking vacations with my family because I wanna be able to look back on the last year and remember something and, you know, I'm not gonna remember all those hours I spent watching YouTube videos or, you know, sitting at my computer responding to emails. But, I will remember those times where I truly changed context. I learned new things. I met new people. We spent time together in a new way, outside of our normal context. And, so that whole part of life has become much, much more important to me because, again, most of our decisions, most of our assessment of our lives, and you know how good they were, it's not based on what we experienced, but what we remembered. 

[00:38:18] Adam Grant:
Can you give us some averages for how long it takes for, for a memory to fade and then how often we'd want to retrieve it or practice or self-test in order for it to stick? 

[00:38:31] Charan Ranganath:
Yes, Ebbinghaus was the first scientist that really quantified how quickly we forget, and he actually measured forgetting by actually memorizing these really arbitrary, meaningless pieces of information and then he would wait a certain amount of time and then he would see, can I recall everything perfectly, and if not, how many study episodes does it take for me to relearn that information? Right?

Typically, in the Ebbinghaus Forgetting Curve, he was finding, even by this really generous measure, within about 24 hours, he was losing about, uh, 60% of what he learned, which is why I say so much of our experience is just doomed to be forgotten, right?

If you're talking about the most meaningless information, like your parking place situation, another example, right, you typically get within like about two hours, I believe. You start to like lose about, you know, 40% of what was memorized before. 

So, it's a very steep curve of forgetting and then it starts to ease off over time. So, definitely within that first day is when you're gonna experience the most forgetting. And, then after that starts to level off. So, probably the best thing to do is if you learn something in the morning, try to recall it again at night before you go to bed, and then you know when you wake up again, try to recall it. 

And, so you're waiting for a lot of that forgetting to have taken place, but not for so much forgetting that you really are gonna be at the point where you're not gonna remember anything about it. 

[00:40:03] Adam Grant:
The final question that that speaks to is I think people are worried when they can't remember something that it's lost. 

And, especially as they age, they get more and more concerned about that. And, I think one of the takeaways of your work is that it's, it's not necessarily gone from our memory in many cases, is that we don't know how to retrieve it. Agree or disagree? 

[00:40:25] Charan Ranganath:
Agree. Yeah. So, I think the kind of subjective proof of this is listening to a song or smelling something, or being back in a place that you haven't been like in a long time, and all of a sudden this thing comes back to you that you just didn't even think that memory existed until it just pops into your head. Right?

And, so the advice I give for trying to find those memories is exactly that. Try to put yourself back in that context, what was happening in that moment in time. There's a lot of controversy in my field about how much is gone and how much can't be retrieved. 

And, this is a big debate and I'm sure there stuff, there's memories that actually are gone, so to speak, or morphed in ways that are just completely unrecognizable.

So, for instance, the first two years of life, nobody really remembers anything. You can get it later on through looking at pictures and stuff and hearing stories, but nobody remembers those periods. 

So, those definitely seem to be gone. 

[00:41:23] Adam Grant:
This has, this has been really interesting and thought provoking, and I would even say memorable. Although, if I forget this conversation, you're telling me that might not be the end of the world. 

[00:41:33] Charan Ranganath:
It might not be the end of the world because you'll still have some savings and the next time you hear it, it'll be like, ah, that's a really good point. 

[00:41:41] Adam Grant:
Yes, but, but that's not gonna happen because I'm gonna think of you every time I watch Severance now.

[00:41:46] Charan Ranganath:
It's a collective memory now. 

[00:41:51] Adam Grant:
If there's one idea from this conversation that you shouldn't forget, the primary purpose of remembering is not to document the past. It's to help you plan the future. 

ReThinking is hosted by me, Adam Grant. This show is part of the TED Audio Collective, and this episode was produced and mixed by Cosmic Standard.

Our producers are Hannah Kingsley-Ma and Aja Simpson. Our editor is Alejandra Salazar. Our fact checker is Paul Durbin. Original music by Hansdale Hsu and Allison Leyton-Brown. 

Our team includes Eliza Smith, Jacob Winik, Samiah Adams, Michelle Quint, Banban Cheng, Julia Dickerson and Whitney Pennington Rodgers. 

[00:42:43] Charan Ranganath:
They had people text messaging. People couldn't tell the difference very often between a real human and the machine. 

[00:42:50] Adam Grant:
It, it reminds me of a paper that I read recently showing that a lot of people thought that if you wanted to convince another person that your text message was from a human, you should say love, but people were actually more persuaded by banana and poop.

I think, I think the, the test was, you can only say one word that convinces the person on the other end that you're actually a human, not a computer. Nope. Don't say love, banana poop.