#430 – Charan Ranganath: Human Memory, Imagination, Deja Vu, and False Memories

Charan Ranganath is a psychologist and neuroscientist at UC Davis, specializing in human memory. He is the author of a new book titled Why We Remember. Please support this podcast by checking out our sponsors: – Riverside: https://creators.riverside.fm/LEX and use code LEX to get 30% off – ZipRecruiter: https://ziprecruiter.com/lex – Notion: https://notion.com/lex – MasterClass: https://masterclass.com/lexpod to get 15% off – Shopify: https://shopify.com/lex to get $1 per month trial – LMNT: https://drinkLMNT.com/lex to get free sample pack Transcript: https://lexfridman.com/charan-ranganath-transcript EPISODE LINKS: Charan’s X: https://x.com/CharanRanganath Charan’s Instagram: https://instagram.com/thememorydoc Charan’s Website: https://charanranganath.com Why We Remember (book): https://amzn.to/3WzUF6x Charan’s Google Scholar: https://scholar.google.com/citations?user=ptWkt1wAAAAJ Dynamic Memory Lab: https://dml.ucdavis.edu/ PODCAST INFO: Podcast website: https://lexfridman.com/podcast Apple Podcasts: https://apple.co/2lwqZIr Spotify: https://spoti.fi/2nEwCF8 RSS: https://lexfridman.com/feed/podcast/ YouTube Full Episodes: https://youtube.com/lexfridman YouTube Clips: https://youtube.com/lexclips SUPPORT & CONNECT: – Check out the sponsors above, it’s the best way to support this podcast – Support on Patreon: https://www.patreon.com/lexfridman – Twitter: https://twitter.com/lexfridman – Instagram: https://www.instagram.com/lexfridman – LinkedIn: https://www.linkedin.com/in/lexfridman – Facebook: https://www.facebook.com/lexfridman – Medium: https://medium.com/@lexfridman OUTLINE: Here’s the timestamps for the episode. On some podcast players you should be able to click the timestamp to jump to that time. (00:00) – Introduction (10:18) – Experiencing self vs remembering self (23:59) – Creating memories (33:31) – Why we forget (41:08) – Training memory (51:37) – Memory hacks (1:03:26) – Imagination vs memory (1:12:44) – Memory competitions (1:22:33) – Science of memory (1:37:48) – Discoveries (1:48:52) – Deja vu (1:54:09) – False memories (2:14:14) – False confessions (2:18:00) – Heartbreak (2:25:34) – Nature of time (2:33:15) – Brain–computer interface (BCI) (2:47:19) – AI and memory (2:57:33) – ADHD (3:04:30) – Music (3:14:15) – Human mind

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Lex Fridman?

  The following is a conversation with Charon Ranganath, a psychologist and neuroscientist at UC Davis specializing in human memory. He's the author of Why We Remember: Unlocking Memory's Power to Hold On to What Matters.

• 0:17Lex Fridman?

  And now, a quick few second mention of each sponsor. Check them out in the description. It's the best way to support this podcast. We got Riverside for recording remote podcasts, ZipRecruiter for hiring, Notion for note-taking and team collaboration, MasterClass for learning, Shopify for e-commerce, and Element for delicious, delicious hydration. Choose wisely, my friends. Also, if you want to work with our amazing team, or you just want to get in touch with me, go to lexfridman.com/contact. And now, onto the full ad reads. As always, no ads in the middle. I try to make these interesting, but if you must skip them, friends, please do check out our sponsors. I enjoy their stuff. Maybe you will too.

• 1:00Lex Fridman?

  This episode is also brought to you by Riverside, the platform for recording remote podcasts and studio quality. I've used them a bunch of times in the past. They're amazing. It is the thing I recommend for anybody, especially for people starting a podcast. Studio quality, exceptionally easy to use, a million features that are all extremely useful for the whole pipeline of creating a podcast. I mean, where do I start? First of all, they do the editing. And you could do text-based editing of the audio and the video. So whatever you say, there's an AI-generated transcript in like 100-plus languages. Whatever the language is, you can use then the text to do the editing. It does speaker detection, so it figures out who's speaking.

• 1:42Lex Fridman?

  All the synchronization, obviously, is done. Not obviously, because some things seem obvious, but a really effortless, beautiful execution of it just is a breath of fresh air. So, in case you don't know, it's a through the browser, you record the video and the audio, both sides of the conversation. Everything is synchronized, everything is stored, just everything is done really well. They have a lot of recommendations of what kind of hardware to use. I think in the video they provide, they say the most important thing is the microphone and lighting, and I agree with that. Good audio is number one. Second to that is indeed lighting because basically every kind of camera that's available now will do all right. Anyway, Riverside makes that whole process super

• 2:26Lex Fridman?

  easy. I record my remote interviews with Riverside. Give it a try at riverside.fm and use code Lex for 30% off. That's riverside.fm and use code Lex. This episode is also brought to you by ZipRecruiter, a site that connects employers and job seekers. To me, one of the most fulfilling things in life is working together with a great team. I love working. I love what I do. Everywhere I've ever worked, I loved doing it. And I love to be surrounded by people who also love doing it and especially who are very good at it and are pushing themselves to the limit and together we're creating something special, whatever that is. It could be a small thing, or it can be a world-changing

• 3:10Lex Fridman?

  thing, whether the mission is small or the mission is big. As long as there's a mission and we're in it together and we're constantly improving. I mean, like, a team that works great together, full of great people, is one of the real joys of life. I think that's true for me. I think that's true for anybody because so much of our lives is spent working. And that's where we really, especially in the realm of intellectual pursuits, really challenge ourselves. And so in the process of that challenge is where we find meaning. So build great teams and use the best tools to do it. See why four out of five employers who post on ZipRecruiter get a quality candidate within the first day. Go to ziprecruiter.com/lex

• 3:54Lex Fridman?

  to try it for free. That's ziprecruiter.com/lex, the smartest way to hire. This episode is brought to you by Notion, a note-taking and team collaboration tool. I've used it for a long time now, for note-taking, for organizing my thoughts, for connecting my thoughts, for searching through my thoughts, and now using AI to summarize, organize, generate drafts of

• 4:22Lex Fridman?

  Things that I'm either planning or ideas that I'm working through or the research that I'm doing. Now, that's for the individual. Where Notion really starts to shine is when there's multiple people working together. It is an incredible team collaboration tool. And again, the AI component gets integrated really nicely because you can do the search, you can do the summarization, you can create a report of what everybody's been working on. It looks to the docs, the wikis, the projects, and can basically do a Q and A for you to figure out, like, where do things stand from a manager position or from an individual contributor? What am I supposed to be doing? What are the people doing? Where can I help? That kind of

• 5:01Lex Fridman?

  stuff. Try Notion AI for free when you go to notion.com/lex. That's all lowercase notion.com/lex to try the power of Notion AI today.

• 5:14Lex Fridman?

  This episode is brought to you by MasterClass, where you can watch over 180 classes from the best people in the world in their respective disciplines. Phil Ivey on poker, Aaron Franklin on barbecue, and Carlos Santana on guitar, Tom Morello on guitar, Terrence Taillot on mathematical thinking, Martin Scorsese on filmmaking. In fact, I would really love, and I'm planning on talking to actors and directors more. I love film. I love great TV. I love that medium of storytelling. And great actors and great directors are the way we consume

• 5:54Lex Fridman?

  stories. They are the medium, the channels, the wizards through which we, all of us, take in the stories, new exciting stories. There's stories of old retold better and better and better. So, I would like to talk to those people. WTF Podcast by Marc Maron. In the past, I really loved it when he interviewed actors and directors, and he's done it really well. Inside Actor Studio was a program I really loved. When long form interviews with actors, long form interviews with directors, even Charlie Rose did a really good job of that. Not the clickbait sort of Hollywood style journalism,

• 6:36Lex Fridman?

  but more long form conversations. I would love to do more of those. Get unlimited access to every masterclass and get an additional 15% off an annual membership at masterclass.com/lexpod. That's masterclass.com/lexpod. This episode is also brought to you by Shopify, a platform designed for anyone to sell anywhere with a great looking online store. I got a store, lexroom.com/store. It has a few shirts on there. If you want to get a shirt, you can get it. It was so easy to set up. I like the machinery of humans selling stuff and buying stuff and through that capitalist

• 7:18Lex Fridman?

  machine figuring out together the things that bring happiness to our lives. In fact, the things isn't the source of happiness, of course. The things are the catalyst for human connection, for humans to connect with each other. Like a T-shirt with Metallica, or whatever band, or whatever podcast, or whatever show you like. Its power is not in the fact that it looks good or something like this. It's power in the connection you make when another person notices it and are also a fan of Metallica or whatever is on the shirt. Or they don't know anything about Metallica, but they like the logo. And it starts a conversation where they'd be like, what is that? Metallica, is that some kind of machine shop thing?

• 8:01Lex Fridman?

  And you say, no, it is the greatest metal band of all time. And there you grab a beer and the conversation begins. It's the human connection. The capitalist machine is not enough. It is merely a catalyst for the beauty of human connection. So join, if you want, the capitalist machine by signing up for a $1 per month trial period at Shopify.com/lex. That's all lowercase. Go to Shopify.com/lex to take your business to the next level today.

• 8:35Lex Fridman?

  This episode is brought to you by Element. It's the delicious electrolyte drink, sodium, potassium, magnesium, that I drink every day, a lot of it every day. I drank it in the jungle when I was dying of thirst. When I was dehydrated and questioning whether I would be able to make it through the day, not to mention the night, I had one pack of Element with me, waiting, knowing that I would disperse that pack of Element into whatever water I would be able to find because electrolyte is also really important. But also, I knew that I've had to drink sort of water, still water, full of mud and all of that. Element would be the thing that makes it taste good.

• 9:19Lex Fridman?

  My favorite flavor, the one I brought to the jungle, the one I always drink is watermelon salt. But they also have cans now, which has like a carbonated fizzy thing to it and lots of great flavors and I really love it. And I've been drinking that nonstop, whatever, whenever I get some, I drink, I drink all of it very quickly. So I highly recommend that as well. Either the packs or the cans of Element Drink, love it. Get a sample pack for free with any purchase. Try it at drinkelement.com/lex. This is the Lex Fridman Podcast. To support it, please check out our sponsors in the description. And now, dear friends, here's Charon Ranganath.

• 10:18Lex Fridman?

  Danny Kahneman describes the experiencing self and the remembering self. And that happiness and satisfaction you gain from the outcomes of your decisions do not come from what you've experienced, but rather from what you remember of the experience. So can you speak to this interesting difference that you write about in your book of the experiencing self and the remembering self?

• 10:42Speaker 01

  Danny really impacted me because I was an undergrad at Berkeley and I got to take a class from him long before he won the Nobel Prize or anything. And it was just a mind blowing class. But this idea of the remembering self and the experiencing self, I got into it because it's so much about memory, even though he doesn't study memory. So we're right now having this experience, right? And people are can watch it presumably on YouTube or listen to it on audio. But if you're talking to somebody else, you could probably describe this whole thing in 10 minutes. But that's going to miss a lot of what actually happened. And so the idea there is is that the way we remember things is not the replay of the experience. It's something totally different.

• 11:26Speaker 01

  And it tends to be biased by the beginning and the end. And he talks about the peaks, that there's also the, you know, the, the best parts, the worst parts, et cetera. And those are the things that we remember. And so when we make decisions, we usually consult memory. And we feel like our memory is a record of what we've experienced, but it's not. It's this kind of very biased sample, but it's biased in an interesting and I think biologically relevant way.

• 11:54Lex Fridman?

  So in the way we construct a narrative about our past, you say that it gives us an illusion of stability. Can you explain that?

• 12:05Speaker 01

  Basically, I think that a lot of learning in the brain is driven towards being able to make sense. I mean, really, memory is all about the present and the future. Past is done, so biologically speaking, it's not important unless there's something from the past that's useful. And so what our brains are really optimized for is to learn about the stuff from the past that's going to be most useful in understanding the present and predicting the future. Right? And so cause effect relationships, for instance, that's a big one. Now, my future is completely unpredictable in the sense that like you could, you know, in the next 10 minutes, pull a knife on me and slit my throat, right?

• 12:46Lex Fridman?

  I was planning on it.

• 12:48Speaker 01

  But having seeds of your work, it just, you know, generally my expectations about life, I'm not expecting that. I have a certainty that everything's going to be fine. We're going to have a great time talking today, right? But we're often right. It's like, okay, so I go to a, see a band on stage, you know, I know they're going to make me wait. The show's going to start late. And then, you know, they come on, there's a very good chance there's going to be an encore. I have a memory, so to speak, for that event before I've even walked into the show, right? There's going to be people holding up their camera phones, trying to take videos of it now, because this is kind of the world we live in. So that's like everyday fortune telling that

• 13:28Speaker 01

  we do, though. It's not real, it's imagined. And it's amazing that we have this capability, and that's what memory is about. But it can also give us this illusion that we know everything that's about to happen. And I think what's valuable about that, that illusion is when it's broken, it gives us the information, right? So, I mean, I'm sure, being in AI, you know about information theory. And the idea is the information is what you didn't already have. And so those prediction errors that we make based on, you know, we make a prediction based on memory, and the errors are where the action is.

• 14:04Lex Fridman?

  The error is where the learning happens.

• 14:08Speaker 01

  Exactly, exactly.

• 14:10Lex Fridman?

  Well, just to linger on Danny Kahneman, and just this whole idea of experiencing self versus remembering self, I was hoping you can give a simple answer of how we should live life. Based on the fact that our memories could be a source of happiness, or could be the primary source of happiness, that an event, when experienced, bears its fruits the most when it's remembered over and over and over and over. And maybe there is some wisdom in the fact that we can control to some degree how we remember it, how we evolve our memory of it, such that

• 14:54Lex Fridman?

  it can maximize the long-term happiness of that repeated experience.

• 15:00Speaker 01

  All right. Well, first, I'll say, I wish I could take you on the road with me, because that was such a great description.

• 15:06Lex Fridman?

  Can I be your opening act?

• 15:07Speaker 01

  Oh, my God, no, I'm gonna open for you, dude. Otherwise, it's like, you know, everybody leaves after you're done.

• 15:16Speaker 01

  Believe me, I did that in Columbus, Ohio, once. It wasn't fun. Like, the opening acts, like, drank our bar tab. We spent all this money going all the way there. There was only the, everybody left after the opening acts were done, and there was just that stoner dude with the dreadlocks hanging out. And then, next thing you know, we blew, like, our savings on getting a hotel room.

• 15:36Lex Fridman?

  So we should, as a small tangent, you're a legit touring act.

• 15:41Speaker 01

  When I was in grad school, I played in a band. And, yeah, we traveled. We would play shows. It wasn't like, we were in a hardcore touring band, but we did some touring and had some fun times. And, yeah, we did a movie soundtrack.

• 15:54Lex Fridman?

  Nice.

• 15:54Speaker 01

  Henry Portrait of a Serial Killer. So that's a good movie. We were on the soundtrack for the sequel, Henry II: Mask of Sanity, which is a terrible movie.

• 16:02Lex Fridman?

  Yeah. How's the soundtrack? Is it pretty good?

• 16:04Speaker 01

  It's badass. At least that one part where the guy throws up the milkshake.

• 16:08Lex Fridman?

  Okay, all right.

• 16:09Speaker 01

  It's my song.

• 16:09Lex Fridman?

  We're gonna have to see. We're gonna have to see it.

• 16:11Speaker 01

  All right, we're getting back to life advice.

• 16:14Lex Fridman?

  And happiness, yeah.

• 16:15Speaker 01

  Uh, one thing that I try to live by, especially nowadays, and since I wrote the book, I've been thinking more and more about this, is how do I want to live a memorable life? You know, I think if we go back to, like, the pandemic, right? How many people have memories from that period? Aside from the trauma of being, you know, locked up and seeing people die and all this stuff. Um, I think it's like one of these things where we were stuck inside, looking at screens all day, doing the same thing with the same people. And so I don't remember much from that in terms of those good memories that you're talking about, right? You know, when I was growing up, my parents worked really

• 16:58Speaker 01

  hard for us, and, you know, we went on some vacations, but not very often. And I really try to do now vacations to interesting places as much as possible with my family, because, like, those are the things that you remember, right? So I really do think about what's going to be, like, something that's memorable, and then just do it, even if it's a pain in the ass, because the experiencing self will suffer for that, but the remembering self will be like, yes, I'm so glad I did that.

• 17:28Lex Fridman?

  Do things that are very unpleasant in the moment, because those can be reframed and enjoyed for many years to come. That's probably good advice, or at least when you're going through shit, it's a good way to see the silver lining of it.

• 17:44Speaker 01

  Yeah, I mean, I think it's one of these things where if you have like, people who you've gone through, since you said it, I'll just say, since you've gone through shit with someone, and it's like, that's a bonding experience often, you know, I mean, that can really bring you together. I like to say it's like, there's no point in suffering unless you get a story out of that.

• 18:05Speaker 01

  So in the book, I talk about the power of the way we communicate with others and how that shapes our memories. And so I had this near death experience, at least that's how I remember it, on this paddleboard where just everything that could have gone wrong did go wrong almost. So many mistakes were made and ended up like at some point, just like basically, away from my board, pinned in a current like in this corner, like not a super good swimmer. And my friend who came with me, Randy, who's a computational neuroscientist, and he had just been pushed down past me, and so he couldn't even see me. And I'm just like, if I die here, you know, I mean, no one's around.

• 18:49Speaker 01

  It's like you just die alone. And so I just said, well, failure is not an option. And eventually I got out of it and froze and got cut up. And I mean, the things that we were going through were just insane. But a short version of this is, you know, my, my wife and my daughter and Randy's wife, they gave us all sorts of hell about this because they were just like, we're, they were ready to send out a search party. So they were giving me hell about it. And then I started to tell people in my lab about this and then friends. And it just became a better and better story every time. And we actually had some photos of just the crazy things like this generator that was hanging over the water.

• 19:32Speaker 01

  And we're like ducking under this, they're these metal gratings and I'm like going flat on, and it was just nuts, you know? But it became a great story and it was definitely, I mean, Randy and I were already tight, but that was a real bonding experience for us. And yeah, I mean, and I learned from that, that it's like, I don't look back on that enough, actually, because I think we often, at least for me, I don't necessarily have the confidence to think that things will work out, that I'll be able to get through a certain thing. But my ability to actually get something done in that moment is better than I give myself credit for, I think. And that was the lesson of that story that I really took away.

• 20:14Lex Fridman?

  Well, actually, just for me, you're making me realize now that it's not just those kinds of stories, but even things like periods of depression or really low points. To me, at least, it feels like a motivating thing, that the darker it gets, the better the story will be if you emerge on the other side. That, to me, feel feels like a motivating thing. So maybe if people listening to this and they're going through some shit, as we said, one thing that could be a source of light is that it'll be a hell of a good story when it's all over, when you emerge on the other side. Let me ask you about decisions. You've

• 20:56Lex Fridman?

  already talked about it a little bit, but when we face the world and we're making different decisions, how much does our memory come into play? Is it the the kind of narratives that we've constructed about the world that are used to make predictions? That's fundamentally part of the decision making?

• 21:16Speaker 01

  Absolutely. Yeah. So let's say after this, you and I decided we're going to go for a beer, right? How do you choose where to go? You're probably going to be like, oh, yeah, this new bar opened up near me, had a great time there. They had a great beer selection. Or you might say, oh, we went to this place and it was totally crowded and they're playing this horrible EDM or whatever. And so, right there, valuable source of information, right? And then you have these things like where you do this counterfactual stuff like, well, I did this previously, but what if I had gone somewhere else instead? Maybe I'll go to this other Place because they didn't try it the previous time. So there's all that kind of reasoning that goes into it, too.

• 21:56Speaker 01

  I think even if you think about the big decisions in life, right? It's like you and I were talking before we started recording about how I got into memory research and you got into AI. And it's like, we all have these personal reasons that guide us in these particular directions. And some of it's the environment and random factors in life. And some of it is memories of things that we want to overcome or things that we build on in a positive way. But either way, they define us.

• 22:27Lex Fridman?

  And probably the earlier in life, the memories happen, the more defining, the more defining power they have in terms of determining who we become.

• 22:36Speaker 01

  I mean, I do feel like adolescence is much more important than I think people give credit for. I think that there is this kind of a sense like, you know, the first three years of life is the most important part. But the teenage years are just so important for the brain, you know? And so that's where a lot of mental illness starts to emerge. You know, now we're thinking of things like schizophrenia as a neurodevelopmental disorder because it just emerges during that period of adolescence and early adulthood. So, and I think the other part of it is, is that, you know, as I guess I was a little bit too firm in saying that memory determines who we are. It's really the self is an evolving construct. I think we kind of underestimate that.

• 23:20Speaker 01

  And when you're a parent, you feel like every decision you make is consequential in forming this child. And plays a role, but so do the child's peers. And so do, you know, there's so much. I mean, that's why I think the big part of education, I think that's so important, is not the content you learn. I mean, think of how much dumb stuff we learned in school, right? But a lot of it is learning how to get along with people and learning who you are and how you function. And, you know, that can be terribly traumatizing, even if you have a perfect, you know, parents working on you.

• 24:00Lex Fridman?

  Is there some insight into the human brain? That explains why we don't seem to remember anything from the first few years of life?

• 24:08Speaker 01

  Yeah, yeah. In fact, actually, I was just talking to my really good friend and colleague, Simona Getty, who studies the neuroscience of child development. And so we were talking about this. And so there are a bunch of reasons, I would say. So one reason is there's an area of the brain in the called the hippocampus, which is very, very important for remembering events or episodic memory. And so the first two years of life, there's a period called infantile amnesia. And then the next couple of years of life after that, there's a period called childhood amnesia. And the difference is that basically in the lab and even during childhood and afterwards, children basically don't have any episodic memories for those

• 24:53Speaker 01

  first two years. The next two years, it's very fragmentary. And that's why they call it childhood amnesia. So there's some, but it's not much. So one reason is that the hippocampus is taking some time to develop. But another is the neocortex, so the whole folded stuff of gray matter all around the hippocampus is developing so rapidly and changing. And a child's knowledge of the world is just massively being built up, right? So I mean, I'm gonna probably embarrass myself, but it's like if you showed like, you know, you trained a neural network and you give it like the first couple of patterns or something like that, and then you bombard it with another like, you know, years worth of data, try to get back those first couple of patterns, right? It's like, everything changes. And

• 25:37Speaker 01

  so the brain is so plastic, the cortex is so plastic during that time. And we think that memories for events are very distributed across the brain. So imagine you're trying to get back that pattern of activity that happened during this one moment. But the roads that you would take to get there have been completely rerouted, right? So I think that's my best explanation. The third explanation is a child's sense of self takes a while to develop. And so their experience of learning might be more learning what happened as opposed to having this first person experience of how I remember I was there.

• 26:15Lex Fridman?

  Well, I think somebody once said to me that kind of loosely philosophically that the reason we don't remember The first few years of life, infantile amnesia is because how traumatic it is. Basically, the error rate that you mentioned, when your brain's prediction doesn't match reality, the error rate in the first few years of life, your first few months certainly, is probably crazy high. It's just nonstop freaking out. The collision between your model of the world and how the world works is just so high that you want whatever trauma of

• 26:57Lex Fridman?

  that is not to linger around. I always thought that's an interesting idea because like, just imagine the insanity of what's happening in a human brain in the first couple of years. Just you don't know anything. And there's just this stream of knowledge and we're somehow, given how plastic everything is, it just kind of molds and figures it out. But it's, it's like an insane waterfall of information.

• 27:24Speaker 01

  I wouldn't necessarily describe it as a trauma, and we can get into this whole stages of life thing, which I just love. Basically, those first few years, there are, I mean, you know, I mean, think about it, a kid's internal model of their body is changing, right? It's like, just learning to move. I mean, like, you know, if you ever have a baby, you'll know that like, the first three months, they're discovering their toes, right? And it's just nuts. So, everything is changing. But what's really fascinating is, and I think this is one of those, this is not at all me being a scientist, but it's like, one of those things that people talk about when they talk about the, you know, positive aspects of children, is that they're exceptionally curious, and they have this kind of openness

• 28:07Speaker 01

  towards the world. And so, that prediction error is not a negative traumatic thing, I think. It's like, a very positive thing, because it's what they use, that they're seeking information. One of the areas that I'm very interested in is the prefrontal cortex. It's an area of the brain that, I mean, I could talk all day about it, but it's, it helps us use our knowledge to say, hey, this is what I want to do now. This is my goal. So, this is how I'm going to achieve it. And focus. Everything towards that goal, right? The prefrontal cortex takes forever to develop in humans. The connections are still being tweaked and reformed like into late adolescence,

• 28:48Speaker 01

  early adulthood, which is when you tend to see mental illness pop up, right? So it's being massively reformed. Then you have about 10 years, maybe of prime functioning of the prefrontal cortex. And then it starts going down again and you end up being older and you start losing all that frontal function. So I look at this and you'd say, okay, from you sit around episodic memory talks. I always say children are worse than adults at episodic memory. Older adults are worse than young adults at episodic memory. And I always say, would say, God, that's so weird. Why would we have this period of time that's so short when we're perfect, right? Or optimal. And I like to use that word optimal now because there's such a culture of optimization right now.

• 29:30Speaker 01

  And it's like, I realized I have to redefine what optimal is because for most of the human condition, I think we had a series of stages of life where you have basically adults saying, okay, young adults saying, I've got a child and you know, I'm part of this village and I have to hunt and forage and get things done. I need a prefrontal cortex so I can stay focused on the big picture and the long haul goals. Now I'm a child. I'm in this village and kind of wandering around and I've got some safety and I need to learn about this culture because I know so little. What's the best way to do that? Let's explore. I don't want to be constrained by goals as much.

• 30:14Speaker 01

  I want to really be free, play and explore and learn. So you don't want a super tight prefrontal cortex. You don't even know what the goals should be yet, right? It's like, if you're trying to design a model that's based on a bad goal, it's going to, it's not going to work well, right? So then you go late in life and you say, oh, why don't you have a great prefrontal cortex then? But I think, I mean, if you go back and you think, how many species actually stick around naturally long after their childbearing years are over, after reproductive years are over, like menopause, from what I understand, menopause is not all that common in the animal world, right? So why would that happen? And so I saw Alison Gopnik said something about

• 30:57Speaker 01

  this, so I started to look into this, about this idea that, you know, really, when you're older, in most societies, your job is no longer to form new episodic memories, it's to pass on the memories that you already have, this knowledge about the world, what we call semantic memory, to pass on that semantic memory to the younger generations, pass on the culture. You know, even now in indigenous cultures, that's the role of the elders, they're respected, they're not seen as, you know, people who are past it and losing it. And I thought that was a very poignant thing, that memory is doing what it's supposed to throughout these stages of life.

• 31:36Lex Fridman?

  So it is always optimal, in a sense, it's just optimal for that stage of life.

• 31:41Speaker 01

  Yeah, and for the ecology of the system. So you've got, so I looked into this, and it's like, another species that has menopause is orcas. Orca pods are led by the grandmothers, right? So not the young adults, not the parents or whatever, the grandmothers. And so they're the ones that pass on the traditions to the, I guess, the younger generation of orcas. And if you, you know, if you look, from what little I understand, different orca pods have different traditions, they hunt for different things, they have different play traditions, and that's a culture, right? And so in social animals, evolution, I think, is designing brains that are really around, you know, it's, it's obviously optimized

• 32:25Speaker 01

  for the individual, but also for kin. And I think that the kin are part of this, like, when they're a part of this intense social group, the brain development should parallel that, the nature of the ecology.

• 32:37Lex Fridman?

  Well, it's just fascinating to think. Of the individual orca or human throughout his life in stages, doing a kind of optimal wisdom development. So in the early days, you don't even know what the goal is. And you figure out the goal and you kind of optimize for that goal and you pursue that goal. And then all the wisdom you collect through that, then you share with the others in the system, the other individuals. And as a, as a collective, then you kind of converge towards greater wisdom throughout the generation. So in that sense, it's optimal. Us humans and orcas got something going on. It works.

• 33:17Speaker 01

  Apex predators.

• 33:20Lex Fridman?

  I just got a megalodon tooth. Speaking of apex predators. It's a, just imagine the size of that thing. Anyway, how does the brain forget? And how and why does it remember? So maybe some of the mechanisms. You mentioned the hippocampus. What are the different components involved here?

• 33:43Speaker 01

  So we could think about this on a number of levels. Maybe I'll give you the simplest version first, which is we tend to think of memories as these individual things and we can just access them, maybe a little bit like, you know, photos on your phone or something like that. But in the brain, the way it works is you have this distributed pool of neurons and the memories are kind of shared across different pools of neurons. And so what you have is competition where sometimes memories that overlap can be fighting against each other. Right? So sometimes we forget because that competition just wipes things out. Sometimes we forget because there aren't the biological signals which we can get into that would promote long-term retention.

• 34:26Speaker 01

  And lots of times we forget because we can't find the cue that sends us back to the right memory and we need the right cue to be able to activate it. Right? So, you know, for instance, in a neural network, there is no, you wouldn't go and you'd say, this is the memory. Right? It's like the whole network, I mean, the whole ecosystem of memories is in the weights of the neural network. And in fact, you could extract entirely new memories, depending on how you feed.

• 34:52Lex Fridman?

  You have to have the right query, the right prompt to access that, whatever the part you're looking for.

• 34:57Speaker 01

  That's exactly right. That's exactly right. And in humans, you have this more complex set of ways memory works. There's, as I said, the knowledge or what you call semantic memory. And then there's these memories for specific events, which we call episodic memory. And so there's different pieces of the puzzle that require different kinds of cues. So that's a big part of it, too, is just this kind of what we call retrieval failure.

• 35:21Lex Fridman?

  You mentioned episodic memory, you mentioned semantic memory. What are the different separations here? What's working memory, short-term memory, long-term memory? What are the interesting categories of memory?

• 35:32Speaker 01

  Yeah. And so memory researchers, we love to cut things up and say, you know, is memory one thing? Or is it two things? There's two things, or there's three things. And so one of the things that, there's value in that. And especially experimental value in terms of being able to dissect things. And the real world is all connected. Speaking of your question, working memory is a term that was coined by Alan Batley. It's basically thought to be this ability to keep information online in your mind, right in front of you at a given time. And to be able to control the flow of that information, to choose what information is relevant, to be able to manipulate it and so forth.

• 36:11Speaker 01

  And one of the things that Alan did that was quite brilliant was he said, there's this ability to kind of passively store information, you know, see things in your mind's eye or hear your internal monologue. But, um, you know, we have that ability to keep information in mind. But then we also have this separate, what he called a central executive, which is identified a lot with the prefrontal cortex. It's this ability to control the flow of information that's being kept active based on what it is you're doing. Now, a lot of my early work was basically saying that this working memory, which some memory researchers would call short-term memory, is not at all independent from long-term memory.

• 36:53Speaker 01

  That is, that a lot of executive function requires learning and you have to have like synaptic change for that to happen. And, um, but there's also Transient forms of memory. So one of the things I've been getting into lately is the idea that we form internal models of events. The obvious one that I always use is birthday parties, right? So you go to a child's birthday party, once the cake comes out and they start, you just see a candle, you can predict the whole frame, you know, set of events that happens later. And up till that point where the child blows out the candle, you have an internal model in your head of what's going on. And so if you follow people's eyes, it's not actually on what's happening. It's going where the action's about to happen, which is just

• 37:38Speaker 01

  fascinating, right? So you have this internal model, and that's a kind of a working memory product. It's something that you're keeping online that's allowing you to interpret this world around you. Now, to build that model, though, you need to pull out stuff from your general knowledge of the world, which is what we call semantic memory. And then you'd want to be able to pull out memories for specific events that happened in the past, which we call episodic memory. So in a way, they're all connected, even though it's different. The things that we're focusing on and the way we organize information in the present, which is working memory, will play a big role in determining how we remember that information later, which people typically call long-term memory.

• 38:20Lex Fridman?

  So if you have something like a birthday party, and you've been to many before, you're gonna load that from disk into working memory, this model, and then you're mostly operating on the model. And if it's a new task, you're, you don't have a model. So you're more in the data collection?

• 38:39Speaker 01

  Yes. One of the fascinating things that we've been studying, and this is, we're not at all the first to do this. Jeff Sachs was a big pioneer in this. And I've been working with many other people, Ken Norman, Leila Devachi, NY, or Columbia has done some interesting stuff with this, is this idea that we form these internal models at particular points of high prediction error, or points of, I believe, also points of uncertainty, points of surprise, or motivationally significant periods. And those points are when it's maximally optimal to encode an episodic memory. So I used to think, oh, well, we're just encoding episodic memories constantly, boom, boom, boom, boom, boom. But think about how much

• 39:22Speaker 01

  redundancy there is in all that, right? It's just a lot of information that you don't need. But if you capture an episodic memory at the point of maximum uncertainty for the singular experience, right, you're just, it's only going to happen once. But if you capture it at the point of maximum uncertainty or maximum surprise, you have the most useful point in your experience that you've grabbed. And what we see is that the hippocampus and these other networks that are involved in generating these internal models of events, they show a heightened period of connectivity or correlated activity during those breaks between different events, which we call event boundaries. These are the points where you're like surprised,

• 40:06Speaker 01

  or you cross from one room to another and so forth. And that communication is associated with a bump of activity in the hippocampus and better memory. And so if people have a very good internal model, throughout that event, you don't need to do much memory processing. You're in a predictive mode, right? And so then, at these event boundaries, you encode, and then you retrieve, and you're like, okay, wait a minute, what's going on here? Branginath's now talking about orcas, what's going on? And maybe you have to go back and remember reading my book to pull out the episodic memory to make sense of whatever it is I'm babbling about, right? And so there's this beautiful dynamics that you can see in the brain of these different networks that are coming together and then deaffiliating

• 40:50Speaker 01

  at different points in time that are allowing you to go into these modes. And so, to speak to your original question, to some extent, when we're talking about semantic memory and episodic memory and working memory, you can think about it as these processes that are unfolding as these networks kind of come together and pull apart.

• 41:08Lex Fridman?

  Can memory be trained and improved? This beautiful connected system that you've described, what aspect of it is a mechanism that can be improved through training?

• 41:22Speaker 01

  I think improvement, it depends on what your definition of optimal is. So what I say in the book is, is that you don't want to remember more. You want to remember better, which means focusing on the things that are important. And that's what our brains are designed to do. So if you go back to the earliest quantitative studies of memory by Ebbinghaus, what you see is that he was trying so hard to memorize this arbitrary nonsense. And within a day, he lost about 60% of that information. And he was using, he was basically using a very, very generous way of measuring it. Right? So as far as we know, nobody has managed to violate those basics of having people forget, you know, most of their experiences.

• 42:05Speaker 01

  So if your expectation is that you should remember everything and that's what your optimal is, you're already off because this is not what human brains are designed to do. On the other hand, what we see over and over again is that the brain does, basically, one of the cool things about the design of the brain is it's always less is more, less is more. Right? It's like, I mean, I've seen estimates that the human brain uses something like 12 to 20 watts, you know, in a day. I mean, that's just nuts, the low power consumption. Right? So it's all about reusing information and making the most of what we already have. And so that's why basically, again, what you see biologically is, you know,

• 42:46Speaker 01

  neuromodulators, for instance, these chemicals in the brain like norepinephrine, dopamine, serotonin, these are chemicals that are released during moments that tend to be biologically significant, surprise, fear, stress, et cetera. And so these chemicals promote lasting plasticity. Right? Essentially some mechanisms by which the brain can say prioritize the information that you carry with you into the future. Attention is a big factor as well, our ability to focus our attention on what's important. And so there's different schools of thought on training attention, for instance. So one of my colleagues, Amishi Ja, she wrote a book called Peak Mind and talks about mindfulness

• 43:31Speaker 01

  as a method for improving attention and focus. So she works a lot with military, like Navy SEALs and stuff, to do this kind of work with mindfulness meditation. Adam Gazali, another one of my friends and colleagues, has work on kind of training through video games, actually, as a way of training attention. And so it's not clear to me, you know, one of the challenges, though, in training is you tend to overfit to the thing that you're trying to optimize, right? So you tend to, if I'm looking at a video game, I can definitely get better at paying attention in the context of the video game, but you transfer it to the outside world. That's very controversial.

• 44:12Lex Fridman?

  The implication there is that attention is a fundamental component of remembering something, allocating attention to it, and then attention might be something that you could train.

• 44:23Speaker 01

  Yeah.

• 44:24Lex Fridman?

  How you allocate attention and how you hold attention on a thing.

• 44:28Speaker 01

  I can say that, in fact, we do in certain ways, right? So if you are an expert in something, you are training attention. So we did this one study of expertise in the brain. And, you know, so people used to think, let's say if you're a bird expert or something, right? People will go like, if you get really into this world of birds, you start to see the differences in your visual cortex is tuned up and it's all about plasticity of the visual cortex. And vision researchers love to say everything's visual. But it's like, we did this study of attention and working, or working memory and expertise. And one of the things that surprised us were the biggest effects as people became experts in identifying these different kinds of just crazy objects that we made up.

• 45:13Speaker 01

  As they developed this expertise of being able to identify what made them different from each other and what made them unique, we were actually seeing massive increases in activity in the prefrontal cortex. And this fits with some of the studies of chess experts and so forth, that it's not so much that you learn the patterns passively, you learn what to look for. You learn what's important, what's not, right? And you can see this in any kind of expert professional athlete. They're looking three steps ahead of where they're supposed to be. So that's a kind of a training of attention. And those are also what you'd call expert memory skills. So if you take the memory athletes, I know that's something we're both interested in.

• 45:52Speaker 01

  And, you know, so these are people who train in these competitions and they'll memorize like a deck of cards in like a really short amount of time. There's a great memory athlete, her name I think is pronounced Yenya Wintersoul. But she, so I think she's got like a giant Instagram following. And so she had this YouTube video that went viral where she had memorized an entire Ikea catalog, right? And so how do people do this? By all accounts from people who become memory athletes, they weren't born with some extraordinary memory. But they practice strategies over and over and over again. The strategy that they use for memorizing a particular thing, it can become automatic and you can just deploy it in an instant. Right?

• 46:37Speaker 01

  So again, it's not necessarily going to, one strategy for learning the order of a deck of cards might not help you for something else that you need, like, you know, remembering your way around Austin, Texas. But it's going to be these, whatever you're interested in, you can optimize for that. And that's just a natural byproduct of expertise.

• 46:58Lex Fridman?

  There's certain hacks. There's something called the memory palace that I've played with. I don't know if you're familiar with that whole technique and it works. It's interesting. So another thing I recommend for people a lot is I use Anki a lot every day. It's a app that does spaced repetition. So I think medical students and like students use this a lot to remember a lot of different things.

• 47:20Speaker 01

  Oh, yeah. Okay, we can come back to this, but yeah.

• 47:22Lex Fridman?

  Sure. It's the whole concept of spaced repetition. You just, when the thing is fresh, you kind of have to remind yourself of it a lot. And then over time, you can wait. A week, a month, a year before you have to recall the thing again. And that way, you essentially have something like note cards that you can have tens of thousands of and can only spend 30 minutes a day and actually be refreshing all of that information, all of that knowledge. It's really great. And then for a memory palace is a technique that allows you to remember things like the Ikea catalog or by placing them visually in a place that you're really familiar with.

• 48:03Lex Fridman?

  Like, I'm really familiar with this place, so I can put numbers or facts or whatever you want to remember. You can walk along that little palace and it reminds you. It's cool. Like, there's stuff like that that I think athletes, memory athletes could use, but I think also regular people can use. One of the things I have to solve for myself is how to remember names. I'm horrible at it.

• 48:27Speaker 01

  Yeah.

• 48:28Lex Fridman?

  I think it's because when people introduce themselves, I have the social anxiety of the interaction where I'm like, I know I should be remembering that, but I'm freaking out internally about social interaction in general. And so therefore, I forget immediately. So I'm looking for good tricks for that.

• 48:49Speaker 01

  So I feel like we've got a lot in common because when people introduce themselves to me, it's almost like I have this like just blank blackout for a moment and then I'm just looking at them like, what happened? I look away or something, what's wrong with me?

• 49:06Lex Fridman?

  Yeah.

• 49:06Speaker 01

  So, I mean, I'm totally with you on this. The reason why it's hard is that there's no reason we should be able to remember names. Because when you say remembering a name, you're not really remembering a name. Maybe in my case you are, but most of the time, you're associating a name with a face and an identity. And that's a completely arbitrary thing, right? I mean, maybe in the olden days, somebody named Miller, it's like they're actually making flour or something like that. But you know, for the most part, it's like, uh, these names are just utterly arbitrary. So you have no thing to latch on to. And so it's not really a thing that our brain does very well. It's to learn meaningless arbitrary stuff. So what you need to do is build connections somehow.

• 49:50Speaker 01

  Visualize a connection and sometimes it's, it's obvious, or sometimes it's not. I'm trying to think of a good one for you now, but the first thing I think of is Lex Luthor, but

• 50:00Lex Fridman?

  That's great.

• 50:00Speaker 01

  Yeah. So I think of Lex Luthor.

• 50:02Lex Fridman?

  This isn't Lex Luthor where, uh, a suit, I think.

• 50:05Speaker 01

  I, I know he has a shaved head though, or he's bald, which you're not. You've got a great head. If I trade hair with you any day, but, but like, you know, but something like that. But if I can come up with something like, I could say, okay, so Lex Luthor is this criminal mastermind. And then I just imagine you.

• 50:20Lex Fridman?

  We talked about stabbing or whatever earlier.

• 50:22Speaker 01

  Yeah, exactly.

• 50:23Lex Fridman?

  Kind of connected and that's it.

• 50:24Speaker 01

  Yeah, yeah. And I, but I'm serious though, that these kinds of weird associations now I'm building a richer network. I mean, one of the things that I find is if I've, like, you can have somebody's name that's just totally generic, like John Smith or something, not that, no offense to people that, that name, but you know, if I, if I see a generic name like that, but I've read John Smith's papers academically, and then I meet John Smith at a conference, I can immediately associate that name with that face because I have this pre-existing network to lock everything into, right? And so you can build that network and that's what the method of low side or the memory palace technique is all about. Is you have a pre-existing structure in your head of like your childhood home,

• 51:07Speaker 01

  or this mental palace that you've created for yourself. And so now you can put arbitrary pieces of information in different locations in that mental structure of yours. And then you could walk through the different path and find all the pieces of information you're looking for. So the method of low side is a great method for just learning arbitrary things because it allows you to link them together and get that cue that you need to pop in and find everything, right?

• 51:37Lex Fridman?

  We should maybe linger on this memory palace thing just to make obvious. Cause when people were describing to me a while ago, what this is, is seems insane. I just, you literally think of a place like a childhood home or a home that you're really visually.

• 52:00Lex Fridman?

  Familiar with and you literally place in that three dimensional space, facts or people or whatever you want to remember. And you just walk in your mind along that place visually. And you can remember, remind yourself of the different things. One of the limitations is there is a sequence to it. So it's, I think your brain somehow, you need, you can't just like go upstairs right away or something. You have to like walk along the, the room. So it's really great for remembering sequences, but it's also not great for remembering like individual facts out of context. So the full context of the tour, I think is important.

• 52:40Lex Fridman?

  But it's, it's fascinating how the mind is able to do that. When you ground these pieces of knowledge into something that you remember well already, especially visually. Fascinating. And you can just do that for any kind of sequence. I'm sure she used something like this for the, for Ikea catalog.

• 52:58Speaker 01

  Oh yeah, absolutely, absolutely. And I think the, the principle here is, again, I was telling you this idea that memories can compete with each other. Right? Well, I like to use this example and maybe someday I'll regret this, but I've used it a lot recently. Is like, imagine if this were my desk, it could be cluttered with a zillion different things. So imagine it's just cluttered with a whole bunch of yellow Post-it notes. And one of them, I put my bank password on it, right? Well, it's going to take me forever to find it. I might, you know, it's just going to be buried under all these other Post-it notes. But if it's like hot pink, it's going to stand out and I find it really easily. Right? So that's one way in which if things are distinctive, if you've processed information in a very distinctive way,

• 53:42Speaker 01

  then you can have a memory that's going to last. And that's very good, for instance, for name, face associations. If I get something distinctive about you, you know, that it's like, that you've got very short hair. And maybe I can make the association with Lex Luthor that way or something like that. Right? You know, but I get something very specific. That's a great cue. But the other part of it is, what if I just organized my notes so that I have my finances in one pile? And I have my like reminders, my to do list in one pile and so forth. So I organize them. Well, then I know exactly if I'm going for my banking, you know, my bank password, I could go to the finance pile. Right? So the method of loci works, or memory palaces work because they give you a way of organizing.

• 54:28Speaker 01

  There's a school of thought that says that episodic memory evolved from this like kind of knowledge of space. And, you know, basically this primitive abilities to figure out where you are. And so people explain the method of loci that way. And, you know, whether or not the evolutionary argument is true, the method of loci is not at all special. So if you don't, you're not a good visualizer, stories are a good one. So a lot of memory athletes will use stories and they'll go like, if you're memorizing a deck of cards, they have a little code for the different like, like the king and the jack and the ten and so forth. And they'll make up a story about things that they're doing and that'll work. Songs are a great one, right?

• 55:11Speaker 01

  I mean, it's like, I can still remember there was this obscure episode of the TV show Cheers. They sing a song about Albania that he uses to memorize all these facts about Albania. I could still sing that song to you. It's just I saw it on a TV show, you know?

• 55:27Lex Fridman?

  So you mentioned spaced repetition. So what, do you like this process? Maybe can you explain it?

• 55:32Speaker 01

  Oh, yeah. If I'm trying to memorize something, let's say if I have an hour to memorize as many Spanish words as I can. If I just try to do like half an hour and then later in the day I do half an hour, I won't retain that information as long as if I do half an hour today and half an hour one week from now. And so doing that extra spacing should help me retain the information better. Now there's an interesting boundary condition, which is it depends on when you need that information. So many of us, you know, for me, like I can't remember so much from college and high school because I crammed, because I just did everything at the last minute.

• 56:12Speaker 01

  And sometimes I would literally study like, you know, in the hallway right before the test. And it was great. Because what would happen is, is I just had that information right there. And so actually not spacing can really help you if you need it very quickly, right? But the problem is, is that you tend to forget it later on. But on the other hand, if you space things out, you get a benefit for later on retention. And so there's many different explanations. We have a computational model of this. It's currently under revision. But in our computer model, what we say is, is that an easy, maybe a good way of thinking about this is,

• 56:52Speaker 01

  this conversation that you and I are having, it's associated with a particular context, a particular place in time. And so all these little cues that are in the background, these little guitar sculptures that you have, and that big light umbrella thing, right? All these things are part of my memory for what we're talking about, the content. So now, later on, you're sitting around and you're at home drinking a beer and you think, God, what a strange interview that was, right? So now you're trying to remember it, but the context is different. So your current situation doesn't match up with the memory that you pulled up. There's error. There's a mismatch between what you pulled up and your current context.

• 57:35Speaker 01

  And so in our model, what you start to do is you start to erase or alter the parts of the memory that are associated with a specific place in time. And you heighten the information about the content. And so if you remember this information in different times and different places, it's more accessible at different times and different places because it's not overfitted in a, in a AI kind of way of thinking about things. It's not overfitted to one particular context. But that's also why the memories that we call upon the most also feel kind of like they're just things that we read about almost. You don't vividly reimagine them, right? It's like they're just these things that just come to us like facts, right?

• 58:16Lex Fridman?

  Yeah.

• 58:16Speaker 01

  And it's a little bit different than semantic memory, but it's like basically they, these events that we have recalled every, you know, over and over and over again, we keep updating that memory. So it's less and less tied to the original experience. And then we have those other ones, which it's like you just get a reminder of that very specific context. You smell something, you hear a song, you see a place that you haven't been to in a while, and boom, it just comes back to you. And that's the exact opposite of what you get with spacing, right?

• 58:45Lex Fridman?

  That's so fascinating. So with spaced repetition, one of its powers is that you lose attachment to a particular context. But then it loses the, the intensity of the flavor of the memory.

• 58:59Speaker 01

  Mm hmm.

• 59:00Lex Fridman?

  That's interesting. That's so interesting.

• 59:02Speaker 01

  Yeah, but you know, at the same time, it becomes stronger in the sense that the content becomes stronger.

• 59:07Lex Fridman?

  Yeah, so it's used for, for learning languages, for learning facts, for learning, for, you know, for that generic semantic information type of memory.

• 59:15Speaker 01

  Yeah. And, and I think this, this falls into a category, we've done other modeling. One of these is published study in PLOS Computational Biology, where we showed that another way, which is, I think, related to the spacing effect is what's called the testing effect. So the idea is, is that if you're trying to learn words, let's say in Spanish or something like that, and this doesn't have to be words, it could be anything, you test yourself on the words and that act of testing yourself helps you retain it better over time than if you just studied it, right? And so from traditional learning theories, some learning theories, anyway, this seems weird, why would you do better

• 59:56Speaker 01

  giving yourself this extra error from testing yourself rather than just, you know, giving yourself perfect input that's a replica of what it is that you're trying to learn? And I think the reason is, is that you get better retention from that error, that mismatch that we talked about, right? So what's happening in our model, it's actually conceptually kind of similar to what happens with backprop in AI, so, or neural networks. And so the idea is, is that you expose, here's the bad connections and here's the good connections. And so we can keep the, the parts of the cell assembly that are good for the memory and lose the ones that are not so good. But if you don't stress test the memory, you

• 1:00:37Speaker 01

  haven't exposed it to the error fully. And so that's why I think this is kind of, this is a thing that I come back to over and over again, is that you will retain information better if you're constantly pushing yourself to your limit, right? If you are feeling like you're coasting, then you're actually not learning.

• 1:00:59Speaker 01

  So it's like.

• 1:01:00Lex Fridman?

  Always you should always be stress testing the memory system.

• 1:01:05Speaker 01

  Yeah, and feel good about it, you know, even though everyone tells me, oh, my memory is terrible. In the moment, they're overconfident about what they'll retain later on. So it's fascinating. And so what happens is when you test yourself, you're like, oh, my God, I thought I knew that, but I don't. And so it can be demoralizing until you get around that and you realize, hey, this is the way that I learned. This is, this is how I learned best. It's like if you're trying to, you know, star in a movie or something like that, you know, just sit around reading the script. You actually act it out and you're going to botch those lines from time to time, right?

• 1:01:42Lex Fridman?

  You know, there's an interesting moment. You probably experienced this. I remember a good friend of mine, Joe Rogan, I was on his podcast. And

• 1:01:53Lex Fridman?

  we were randomly talking about soccer football. Somebody I grew up watching, Diego Armando Maradona, one of the greatest soccer players of all time. And we were talking about him and his career and so on. And Joe asked me if he's still around.

• 1:02:13Lex Fridman?

  Now, and I said, yeah.

• 1:02:18Lex Fridman?

  I don't know why I thought, yeah, because that was a perfect example of memories. He, he passed away. I tweeted about it, how heartbroken I was, all this kind of stuff, like a year before. I know this, but in my mind, I went back to the thing I've done many times in my head. Visualizing some of the epic runs he had on goal and so on. So for me, he's alive. So I'm part of the also the conversation when you're talking to Joe, you're the stress and like your, the focus is allocated, the attention is allocated in a particular way. But when I walked away, I was like, in which world was Diego Maradona still alive? Like in which, because I was sure in my head that he was still alive.

• 1:03:04Lex Fridman?

  There was a, it's a moment that sticks with me. There's, I've had a few like that in my life where it just kind of.

• 1:03:11Lex Fridman?

  Like obvious things just disappear from mind. And it's cool, like it shows actually the power of the mind in a positive sense to erase memories you want erased, maybe. But I don't know, I don't know if there's a good explanation for that.

• 1:03:26Speaker 01

  One of the cool things that that I found is is that some people really just revolutionize a field by by creating a problem that didn't exist before. It's kind of like why I love science is like I engineering is like solving other people's problems and science is about creating problems. I'm just much more like I want to break things and you know, create problems.

• 1:03:48Lex Fridman?

  Yeah.

• 1:03:49Speaker 01

  Not necessarily move fast, though.

• 1:03:52Speaker 01

  But one of my former mentors, Marcia Johnson, who in my opinion is one of the greatest memory researchers of all time. She comes up, young woman in the field and it's mostly guy field. And she gets into this idea of how do we tell the difference between things that we've imagined and things that we actually remember? How do we tell I get some mental experience? Where did that mental experience come from? Right? And it turns out this is a huge problem. Because essentially, our mental experience of remembering something that happened, our mental experience of thinking about something, how do you tell the difference? They're both largely constructions in our head. And so it is very important.

• 1:04:33Speaker 01

  And the way that you do it is, I mean, it's not perfect, but the way that we often do it and succeed is by again, using our prefrontal cortex and really focusing on the sensory information or the place and time and the things that put us back into when this information happened. And if it's something you thought about, you're not going to have all of that vivid detail as you do for something that actually happened. But it doesn't work all the time, but that's a big thing that you have to do, but it takes time. It's slow and it's again, effortful. But that's what you need to remember accurately. But what's cool, and I think this is what you alluded to about how that was an interesting experience is imagination is exactly the opposite.

• 1:05:15Speaker 01

  Imagination is basically saying, I'm just going to take all this information from memory. Recombine it in different ways and throw it out there. And so for instance, Dan Schachter and Donna Addus did cool work on this. Demis Hasibus did work on this with Eleanor Maguire in UCL. And this goes back actually to this guy Frederick Bartlett, who is this revolutionary memory researcher. Bartlett, he actually like rejected the whole idea of quantifying memory. He said, there's no statistics in my book. He came from this anthropology perspective. And short version of the stories, he just asked people to recall things. You give people stories

• 1:05:56Speaker 01

  and poems, ask people to recall them. And what he found was people's memories didn't reflect all of the details of what they were exposed to. And they did reflect a lot more. They were filtered through this lens of prior knowledge, the cultures that they came from, the beliefs that they had, the things they knew. And so what he concluded was that he called remembering an imaginative construction, meaning that we don't replay the past. We imagine how the past could have been by taking bits and pieces that come up in our heads. And likewise, he wrote this beautiful taper on imagination, saying, when we imagine something and create something, we're creating it from these specific experiences that we've had and combining it with our general knowledge. But

• 1:06:40Speaker 01

  instead of trying to focus it on being accurate and getting out one thing, you're just ruthlessly recombining things without any, you know, any necessary kind of goal in mind. I mean, or at least that's one kind of creation.

• 1:06:54Lex Fridman?

  So imagination is fundamentally coupled with memory in both directions?

• 1:07:03Speaker 01

  I think so. I mean, it's not clear that it is in everyone, but one of the things that's been studied is some patients who have amnesia, for instance, they have brain damage, say to the hippocampus. And if you ask them to imagine things that are not in front of them, like imagine what could happen after I leave this room, right? They are find it very difficult to give you a scenario of what could happen. Or if they do, it'd be more stereotyped like, yes, this would happen. But it's not like they can come up with anything that's very vivid and creative in that sense. And it's partly because when you have amnesia, you're stuck in the present. Because to get a very good model of the future, it really helps to have episodic memories to draw upon, right?

• 1:07:47Speaker 01

  And so that's, that's the basic idea. And in fact, one of the most impressive things, when people started to scan people's brains and ask people to remember past events, what they found was there was this big network of the brain called the default mode network. It gets a lot of press because it's like thought to be important. It's engaged during mind wandering. And if I ask you to pay attention to something, it only comes on when you stop paying attention. You know, so people, oh, it's just this kind of, you know, daydreaming network. And I thought, this is just ridiculous research. Who cares? You know? But then what people found was when people recall episodic memories, this network gets active.

• 1:08:27Speaker 01

  And so we started to look into it and this network of areas is really closely functionally interacting with the hippocampus. And so in fact, some would say the hippocampus is part of this default network. And if you look at brain images of people or brain maps of activation, so to speak, of people imagining possible scenarios of things that could happen in the future, even things that couldn't really be very plausible, they look very similar. I mean, you know, to the naked eye, they look almost the same as maps of brain activation when people remember the past. According to our theory, and we've got some data to support this, we've broken up this network into various sub pieces, is that basically it's kind of taking apart all of

• 1:09:11Speaker 01

  our experiences and creating these little Lego blocks out of them. And then you can put them back together if you have the right instructions to recreate these experiences that you've had, but you could also reassemble them into new pieces to create a model of an event that hasn't happened yet. And that's what we think happens. And when I'm, our common ground that we're establishing in language requires using those building blocks to put together a model of what's going on.

• 1:09:38Lex Fridman?

  There's a good percentage of time I personally live in, in the imagined world. I think of, I've, I do thought experiments a lot. I, you know, take the absurdity of human life as it stands and play it forward in all kinds of different directions. Sometimes it's rigorous thoughts, thought experiments, sometimes it's fun ones. So I imagine that that has an effect on how I remember things. And I suppose I have to be a little bit careful to make sure stuff happened versus stuff that I just imagined happened. And this also, I mean, some of my best friends are characters inside books that never even

• 1:10:23Lex Fridman?

  existed. And I'm, you know, there's some degree to which they actually exist in my mind. Like, these characters exist, authors exist, the Stevsky exists, but also Brothers Karamazov.

• 1:10:37Speaker 01

  I love that book.

• 1:10:38Lex Fridman?

  Yeah.

• 1:10:39Speaker 01

  It's one of the few books I've read. One of the few literature books that I've read, I should say. I read a lot in school that I don't remember, but Brothers Karamazov.

• 1:10:47Lex Fridman?

  But they exist. They exist, and I have almost kind of like conversations with them. It's interesting. It's, uh, it's interesting to allow your brain to kind of play with ideas of the past, of the imagined, and see it all as one.

• 1:11:00Speaker 01

  Yeah, there was actually this famous mnemonist, he's kind of like back then the equivalent of a memory athlete, except he would go to shows and do this. That was described by this really famous neuroscientist from Russia named Luria. And so this guy was named Solomon Sherashewski, and he had this condition called synesthesia that basically created these weird associations between different senses that normally wouldn't go together. So that gave him this incredibly vivid imagination that he would use to basically imagine all sorts of things that he would need to memorize. And he would just imagine, like, just create these incredibly detailed things in his head

• 1:11:44Speaker 01

  that allowed him to memorize all sorts of stuff. But it also really haunted him by some reports that basically it was like he was at some point, you know, and again, who knows if the drinking was part of this, but at some point had trouble differentiating his imagination from reality, right? And this is, this is interesting because it's like, I mean, that's what psychosis is in some ways is you, you know, first of all, you're just learning connections from prediction errors that you probably shouldn't learn. And the other part of it is, is that your internal signals are being confused with actual things in the outside world, right?

• 1:12:23Lex Fridman?

  Well, that's why a lot of this stuff is both feature and bug. It's a double edged sword.

• 1:12:27Speaker 01

  Yeah, I mean, it might be why there's such an interesting relationship between genius and psychosis.

• 1:12:32Lex Fridman?

  Yeah, maybe they're just two sides of the same coin. Humans are fascinating, aren't they?

• 1:12:40Speaker 01

  I think so. Sometimes scary, but mostly fascinating.

• 1:12:43Lex Fridman?

  Can we just talk about memory sport a little longer? There's something called the USA Memory Championship. Like, what are these athletes like? What does it mean to be like elite level at this? Have you interacted with any of them or reading about them? What have you learned about these folks?

• 1:13:02Speaker 01

  There's a guy named Henry Rodiger who's studying these guys. And there's actually a book by Joshua For called Moonwalking with Einstein where he talks about, he actually, as part of this book, just decided to become a memory athlete. They often have these life events that make them go, hey, why don't I do this? So there was a guy named Scott Hagwood, who I write about, who thought that he was, he was getting chemo for cancer. And so he decided, like, because the chemo, there's a well-known thing called chemo brain, where people become like, they just lose a lot of their sharpness. And so he wanted to fight that by learning these memory skills. So he bought a book and this is the story you hear in a lot of memory athletes is they

• 1:13:47Speaker 01

  buy a book by other memory athletes. Or other memory experts, so to speak. And they just learn those skills and practice them over and over again. They start by winning bets and so forth, and then they go into these competitions. And the competitions are typically things like memorizing long strings of numbers or memorizing, you know, orders of cards and so forth. So there tend to be pretty arbitrary things, not like things that would be able, you'd be able to bring a lot of prior knowledge. But they build the skills that you need to memorize arbitrary things.

• 1:14:21Lex Fridman?

  Yeah, that's fascinating. I've gotten a chance to work with something called end back tasks. So there's all these kinds of tasks, memory recall tasks that are used to kind of load up the quote unquote working memory.

• 1:14:32Speaker 01

  Yeah, yeah.

• 1:14:33Lex Fridman?

  And to see, a psychologist used it to test all kinds of stuff, like to see how well you're good at multitasking. We use it in particular for the task of driving, like if you fill up your brain with intensive working memory tasks, how good are you at also not crashing, that kind of stuff. So it's fascinating, but again, those tasks are arbitrary and they're usually about recalling a sequence of numbers in some kind of semi-complex way. Are you, do you have any favorite tasks of this nature in your own studies?

• 1:15:10Speaker 01

  I've really been most excited about going in the opposite direction and using things that are more and more naturalistic. And the reason is, is that we've really moved, we've moved in that direction because what we found is that memory works very, very differently when you study it, when you study memory in the way that people typically remember. And so it goes into a much more predictive mode and you have these event boundaries, for instance, and you have, but a lot of what happens is this kind of fascinating mix that we've been talking about, a mix of interpretations and imagination with perception. And so, and

• 1:15:54Speaker 01

  the new direction we're going in is understanding navigation in our memory for places. And the reason is, is that there's a lot of work that's done in rats, which is very good work. They have a rat and they put it in a box and the rat goes, chases cheese in a box. You'll find cells in the hippocampus that fire when a rat is in different places in the box. And so the conventional wisdom is that the hippocampus forms this map of the box. And I think that probably may happen.

• 1:16:26Speaker 01

  When you have like absolutely no knowledge of the world, right? But I think one of the cool things about human memory is we can bring to bear our past experiences to economically learn new ones. And so for instance, if you learn a map of an Ikea, let's say if I go to the Ikea in Austin, I'm sure there's one here. I probably could go to this Ikea and find my way to the, you know, where the wine glasses are without having to even think about it because it's got a very similar layout, even though Ikea is a nightmare to get around. Once I learned my local Ikea, I can use that map everywhere. Why form a brand new one for a new place?

• 1:17:08Speaker 01

  And so that kind of ability to reuse information really comes into play when we look at things that are, you know, more naturalistic tasks. And another thing that we're really interested in is this idea of like, what if instead of basically mapping out every coordinate in a space, you form a pretty economical graph that connects basically the major landmarks together and being able to use that as, you know, emphasizing the things that are most important, the places that you go for food and the places that are landmarks that help you get around. And then filling in the blanks for the rest because I really believe that cognitive maps or mental maps of the world,

• 1:17:53Speaker 01

  just like our memories for events are not photographic. I think there's this combination of actual verifiable details and then a lot of inference that you make.

• 1:18:04Lex Fridman?

  So what have you learned about this kind of spatial mapping of places? How do people represent locations?

• 1:18:12Speaker 01

  Uh, there's a lot of variability. I think that, and there's a lot of disagreement about how people represent locations. In a world of GPS and physical maps, people can learn it from like basically what they call like survey perspective of being able to see everything. And so that's one way in which humans can do it. That's a little bit different. There's one way which we can memorize routes, like I know how to get from here to, let's say if I knew walk here for my hotel, I can just rigidly follow that route back, right? And there's another more integrative way, which would be what's called a cognitive map, which would be kind of a sense of how everything relates to each other.

• 1:18:54Speaker 01

  And so there's lots of people who believe that these maps that we have in our head are isomorphic with the world. They're like these literal coordinates that follow Euclidean space. And as you know, Euclidean mathematics is very constrained, right? And I think that we are actually much more generative in our maps of space so that we do have these bits and pieces. And we've, we've got a small task as it's right now, not yet. Like, uh, we need to do some work on it for further analyses. But one of the things we're looking at is, uh, these signals called ripples in the hippocampus, which are these bursts of activity that you see that are synchronized with areas in the neocortex,

• 1:19:38Speaker 01

  in the default network, actually. And so what we find is, is that those ripples seem to increase at navigationally important points when you're making a decision or when you reach a goal. So this speaks to the emotion thing, right? Cause if you have limited choices, if I'm walking down a street, I could really just get a mental map of the neighborhood with a more minimal kind of thing by just saying, here's the intersections and here's the directions I take to get in between them. And what we found in general in our MRI studies is basically the more people can reduce the problem, whether it's space or any kind of decision-making problem, the less the hippocampus encodes.

• 1:20:21Speaker 01

  It really is very economical towards the points of most, highest information content and value.

• 1:20:28Lex Fridman?

  So can you describe the encoding in the hippocampus and the ripples you were talking about? What the, what's the signal in which we see the ripples?

• 1:20:38Speaker 01

  Yeah, so this is really interesting. There are these oscillations, right? So there is these waves that you basically see. And, um, these waves are points of very high excitability and low excitability. And, uh, at least during, they happen actually during slow wave sleep too. So the deepest stages of sleep when you're just zonked out, right? You see these very slow waves where it's like very excitable and then very unexcitable. It goes up and down. And on top of them, you'll see these little sharp wave ripples. And when there's a ripple in the hippocampus, you tend to see a sequence of cells that resemble a sequence of cells that fire when, you know, an animal's actually doing something in the world.

• 1:21:21Speaker 01

  So it almost is like a little, people call it replay. It's a little bit, I don't like that term, but it's basically a little bit of a compressed play of the sequence of activity in the brain that was taking place earlier. And during those moments, there's a little window of communication between the hippocampus and these areas in the neocortex. And so that, I think, helps you form new memories, but it also helps you, I think, stabilize them, but also really connect different things together in memory and allows you to build bridges between different events that you've had. And so this is one of, or at least our theories of sleep and its real role in helping you see the connections between different events that you've experienced.

• 1:22:07Lex Fridman?

  Oh, so during sleep is one of the connections that formed?

• 1:22:10Speaker 01

  The connections between different events.

• 1:22:12Lex Fridman?

  Yeah.

• 1:22:13Speaker 01

  Right? So it's like, you see me now, you see me next week, you see me a month later. You start to build a little internal model of how I behave and, you know, what to expect of me. And we think sleep, one of the things that allows you to do is figure out those connections and connect the dots and find the signal in the noise.

• 1:22:33Lex Fridman?

  So you mentioned FMRI. What is it and how is it used in studying memory?

• 1:22:39Speaker 01

  This is actually the reason why I got into this whole field of science. So when I was in grad school, FMRI was just really taking off as a technique for studying brain activity. And what's beautiful about it is you can study the whole human brain. And there's lots of limits to it, but you can basically do it in person without sticking anything into their brains and very non-invasive. I mean, for me, being an MRI scanner is like being in the womb. I just fall asleep. If I'm not being asked to do anything, I get very sleepy, you know? But you can have people. Watch movies while they're being scanned, or you can have them do tests of memory, like giving them words and so forth to memorize.

• 1:23:21Speaker 01

  But what MRI is itself is just this technique where you put people in a very high magnetic field. Typical ones we would use would be three Tesla to give you an idea. So three Tesla magnet, you put somebody in and what happens is you get this very weak, but you know, measurable magnetization in the brain. And then you apply a radio frequency pulse, which is basically a different electromagnetic field. And so you're basically using water, the water molecules in the brain as a tracer, so to speak. And part of it in FMRI is the fact that these magnetic fields that you mess with by manipulating

• 1:24:05Speaker 01

  these radio frequency pulses and the static field. And you have things called gradients, which change the strength of the magnetic field in different parts of the head. So they're all, we tweak them in different ways, but the basic idea that we use in FMRI is that blood is flowing to the brain. And when you have blood that doesn't have oxygen on it, it's a little bit more magnetizable than blood that does, because you have hemoglobin that carries the oxygen, the iron basically in the blood that makes it red. And so that hemoglobin, when it's deoxygenated, actually has different magnetic field properties than when it has oxygen. And it turns out when you have an increase in local activity in some part of the brain,

• 1:24:49Speaker 01

  the blood flows there and as a result, you get a lower concentration of hemoglobin that is not oxygenated. And then that gives you more signal. So I gave you, I think I sent you a GIF, as you like to say.

• 1:25:07Lex Fridman?

  Yeah, we had off record intense argument. Well, if it's pronounced Jif or gif, but that's we shall set that aside.

• 1:25:16Speaker 01

  We could have called it a stern rebuke, perhaps.

• 1:25:19Lex Fridman?

  Rebuke, yeah. I drew a hard line. It is true, the creator of GIFs said it's pronounced Jif, but that's the only person that pronounces Jif. Anyway, yes, you sent a GIF of.

• 1:25:34Speaker 01

  This would be basically a whole, a movie of fMRI data. And so when you look at it, it's not very impressive. It looks like these like very pixelated maps of the brain, but it's mostly kind of like white. But these tiny changes in the intensity of those signals that you probably wouldn't be able to visually perceive, like about 1% can be statistically very, very large effects for us. And that allows us to see, hey, there's an increase in activity in some part of the brain when I'm doing some task like trying to remember something. And I can use those changes to even predict, is a person going to remember this later or not? And the coolest thing that people have done is to decode what people

• 1:26:18Speaker 01

  are remembering from the patterns of activity from, because maybe when I'm remembering this thing, like I'm remembering the house where I grew up, I might have one pixel that's bright in the hippocampus and one that's dark. And if I'm remembering, you know, something like more like the car that I used to drive when I was 16, I might see the opposite pattern where a different pixel is bright. And so all that little stuff that we used to think of noise, we can now think of almost like a QR code for memory, so to speak, where different memories have a different little pattern of bright pixels and dark pixels. And so this really revolutionized my research. So there's fancy research out there where people really, I mean, not even that, I mean, by your standards would be Stone Age, but

• 1:27:02Speaker 01

  you know, applying machine learning techniques to do decoding and so forth. And now there's a lot of forward encoding models and you can go to town with this stuff, right? And I'm much more old school of designing experiments where you basically say, okay, here's a whole web of memories that overlap. In some way, shape or form, do memories that occurred in the same place have a similar QR code? And do memories that occurred in different places have a different QR code? And you can just use things like correlation coefficients or cosine distance to measure that stuff, right? Super simple, right? And so what happens is you can start to get a whole state space of how a brain area is indexing all these different memories. And

• 1:27:47Speaker 01

  it's super fascinating because what we could see is this little like separation between how certain brain areas are processing memory for who was there and other brain areas are processing information about where it occurred, or the situation that's kind of unfolding. And some are giving you information about what are my goals that are involved and so forth. And so, and the hippocampus is just putting it all together into these unique things that just are about when and where it happened.

• 1:28:15Lex Fridman?

  So there's a separation between spatial information, concepts, like literally there's distinct, as you said, QR codes for these?

• 1:28:28Speaker 01

  So to speak, let me try a different analogy too, that might be more accessible for people, which would be like, you've got a folder on your computer, right? And you open it up, there's a bunch of files there. I can sort those files by, you know, alphabetical order. And now things that both start with letter A are lumped together, and things that start with Z versus A are far apart, right? And so that is one way of organizing the folder, but I could do it by date. And if I do it by date, things that were created close together in time are close, and things that are far apart in time are far. So every, like, you can think of how a brain area or a network of areas contributes to memory by looking

• 1:29:10Speaker 01

  at what the sorting scheme is. And these QR codes that we're talking about that you get from fMRI allow you to do that. And you can do the same thing if you're recording from massive populations of neurons in an animal. And you can do it for a recording, local potentials in the brain, you know, so little waves of activity in, let's say, a human who has epilepsy, and they stick electrodes in their brain to try to find the seizures. So that's some of the work that we're doing now. But all these techniques basically allow you to say, hey, what's the sorting scheme? And so we've found that some networks of the brain sort information in memory according to who was there. So I might have, like, we've actually shown in one of my favorite

• 1:29:55Speaker 01

  studies of all time that was done by a former postdoc, Zach Ray, and Zach did the study where we had a bunch of movies with different people in my labs. There are two different people and he filmed them at two different cafes and two different supermarkets. And what you could show is in one particular network, you could find the same kind of pattern of activity, more or less, a very, very similar pattern of activity every time I saw Alex in one of these movies, no matter where he was, right? And I could see another one that was like a common pattern that happened every time I saw this particular supermarket nugget, you know? And so, and it didn't matter whether you're watching

• 1:30:37Speaker 01

  a movie or whether you're recalling the movie. It's the same kind of pattern that comes up, right?

• 1:30:42Lex Fridman?

  That's so fascinating.

• 1:30:43Speaker 01

  It's fascinating. It's so, now you have those building blocks for assembling a model of what's happening in the present, imagining what could happen and remembering things very economically from putting together all these pieces. So that all the hippocampus has to do is get the right kind of blueprint for how to put together all these building blocks.

• 1:31:03Lex Fridman?

  These are all like beautiful hints at a super interesting system that makes me wonder on the other side of it, how to build it. But it's like, it's fascinating. Like the way it does the encoding is really, really fascinating. Or I guess the symptoms, the results of that encoding are fascinating to study from this. Just as a small tangent, you mentioned sort of the measuring local potentials with electrodes versus FMRI.

• 1:31:31Speaker 01

  Oh, yeah.

• 1:31:32Lex Fridman?

  What are some interesting like limitations, possibilities of FMRI? Maybe the way you explain it is like brilliant with, with blood and detecting the, um, the activations or the excitation because blood flows to that area. What's like the latency of that? Like, what's the blood dynamics in the brain that?

• 1:31:54Speaker 01

  Yeah, yeah.

• 1:31:54Lex Fridman?

  Like, how quickly can it?

• 1:31:57Lex Fridman?

  How quickly can the tasks change and all that kind of stuff?

• 1:31:59Speaker 01

  Yeah, I mean, it's very slow to the brain 50 milliseconds is like, you know, like it's an eternity. Maybe 50, you know, maybe like, you know, let's say half a second, 500 milliseconds, just so much back and forth stuff happens in the brain in that time. Right? So in fMRI, you can measure these magnetic field responses about six seconds after that burst of activity would take place. All these things, it's like, is it a feature? Or is it a bug? Right? So one of the interesting things that's been discovered about fMRI is it's not so tightly related to the spiking of the neurons. So we tend to think of the

• 1:32:42Speaker 01

  computation, so to speak, as being driven by spikes, meaning like there's just a burst of it's either on or it's off and the neurons like going up or down. But sometimes what you can have is these states where the neuron becomes a little bit more excitable or less excitable. And so fMRI is very sensitive to those changes in excitability. Actually, one of the fascinating things about fMRI is where does that, how is it we go from neural activity to, you know, essentially blood flow to oxygen, you know, all this stuff. It's such a long chain of, you know, going from neural activity to magnetic fields.

• 1:33:23Speaker 01

  And one of the theories that's out there is most of the cells in the brain are not neurons. They're actually these support cells called glial cells. And one big one is astrocytes. And they play this big role in regulating, you know, kind of being a middle man, so to speak, with the neurons. So if you, for instance, like one neuron's talking to another, you release a neurotransmitter, like let's say glutamate, and that gets another neuron, starts talking, starts getting active after you release it in the gap between the two neurons called synapse. So what's interesting is if you leave that, you know, imagine you're just flooded with this like liquid in there, right? If you leave it in there too long, you just excite the other neuron too much and you can start to basically get seizure

• 1:34:07Speaker 01

  activity. You don't want this. So you got to suck it up. And so actually what happens is these astrocytes, one of their functions is to suck up the glutamate from the synapse. And that is a massively, and then break it down and then feed it back into the neurons so that you can reuse it. But that cycling is actually very energy intensive. And what's interesting is, at least according to one theory, they need to work so quickly that they're working on metabolizing the glucose that comes in without using oxygen, kind of like what anaerobic metabolism. So they're not using oxygen as fast as they are using glucose. So what we're really seeing in some ways may be in fMRI, not the neurons

• 1:34:52Speaker 01

  themselves being active, but rather the astrocytes which are meeting the metabolic demands of the process of keeping the whole system going.

• 1:35:02Lex Fridman?

  It does seem to be that fMRI is a good way to study activation. So with these astrocytes, even though there's a latency, it's pretty reliably coupled to the activations.

• 1:35:16Speaker 01

  Oh, well, this gets me to the other part of it. So now, let's say, for instance, if I'm just kind of like, I'm talking to you, but I'm kind of paying attention to your cowboy hat, or I'm looking off to the, or I'm thinking about the right, even if I'm not looking at it. What you'd see is that there'd be this little elevation in activity in areas in the visual cortex, which process vision around that point in space. Okay. So if then something happened, like, you know, a sudden a light flashed in that part of, you know, right in front of your cowboy hat, I would have a bigger response to it. But what you see in fMRI is even if I'm not, even if I don't see that flash of light, there's a lot of activity that I can measure because you're kind of keeping it excitable and that

• 1:36:00Speaker 01

  in and of itself, even though I'm not seeing anything there that's particularly interesting, there's still this increase in activity. And so it's more sensitive with fMRI. So then, is that a feature or is it a bug? You know, some people, people who study spikes in neurons would say, well, that's terrible. We don't want that, you know. Likewise, it's slow and that's terrible for measuring things that are very fast. But one of the things that we've found in our work was when we give people movies and when we give people stories to listen to, a lot of the action is in the very, very slow stuff. It's in because if you're thinking about like a story, let's say you're, you're listening to a podcast or something, you're listening to the Lex Fridman podcast, right?

• 1:36:44Speaker 01

  You're putting this stuff together and building this internal model over several seconds, which is basically, we filter that out when we look at electrical activity in the brain because we're interested in this millisecond scale. It's almost massive amounts of information, right? So the way I see it is every technique gives you a little limited window into what's going on. MRI is huge problems. You know, people lie down in the scanner. There's parts of the brain where you, I'll show you in some of these images where you'll see kind of gaping holes because there's, you can't keep the magnetic field stable in those spots. You'll see parts where it's like there's a vein and so it just produces big increase and decrease in signal or respiration that causes these changes. There's lots of artifacts

• 1:37:28Speaker 01

  and stuff like that, you know? Every technique has its limits. If, if I'm lying down in MRI scanner, I'm lying down. I'm not interacting with you in the same way that I would in the real world. But at the same time, I'm getting data that I might not be able to get otherwise. And so different techniques give you different kinds of advantages.

• 1:37:48Lex Fridman?

  What kind of big scientific discoveries, maybe the flavor of discoveries have been done throughout the history of the science of memory, the studying of memory? What kind of things have been like understood?

• 1:38:03Speaker 01

  Oh, there's so many. It's really so hard to summarize it. I mean, I think it's funny because it's like, when you're in the field, you can get kind of blasé about this stuff. But then once I started to write the book, I was like, oh my God, this is really interesting. How did we do all this stuff?

• 1:38:21Speaker 01

  I would say that some of the, I mean, you know, from the first studies, just showing how much we forget is very important. Showing how much schemas, which is our organized knowledge about the world, increase our ability to remember information, just massively increase it. Studies of expertise showing how experts like chess experts can memorize so much in such a short amount of time because of the schemas they have for chess. But then also showing that those lead to all sorts of distortions in memory. The discovery that the act of remembering can change the memory, can strengthen it, but it can also distort it if you get misinformation

• 1:39:04Speaker 01

  at the time. And it can also strengthen or weaken other memories that you didn't even recall. So just this whole idea of memory as an ecosystem, I think, was a big discovery.

• 1:39:15Speaker 01

  I could go, this idea of like breaking up our continuous experience into these discreet events, I think was a major discovery.

• 1:39:24Lex Fridman?

  So the discreteness of our encoding of events?

• 1:39:26Speaker 01

  Maybe, yeah. I mean, you know, and again, there's controversial ideas about this, right? But it's like, yeah, this idea that, and this gets back to just this common experience of you walk into the kitchen and you're like, why am I here? And you just end up grabbing some food from the fridge. And then you go back and you're like, oh, wait a minute, I left my watch in the kitchen. That's what I was looking for. And so what happens is, is that you have a little internal model of where you are, what you're thinking about. And when you cross from one room to another, those models get updated. And so now, when you're in the kitchen, you have to go back and mentally time travel back to this earlier point to remember what, what it was that you went there for. And so these event boundaries, turns out, like, in our research, and again, I don't want to make it sound like we've figured

• 1:40:10Speaker 01

  out everything, but in our research, one of the things that we found is, is that Basically, as people get older, the activity in the hippocampus at these event boundaries tends to go down. And but independent of age, if I give you outside of the scanner, you're done with the scan, I just scan you while you're watching a movie, just watch it. You come out, I give you a test of memory for stories. What happens is you find this incredible correlation between the activity in the hippocampus at these singular points in time, these event boundaries, and your ability to just remember a story outside of the scanner later on. So it's marking this ability to encode memories, just these little snippets

• 1:40:55Speaker 01

  of neural activity. So I think that's a big one. There's all sorts of work in animal models that I can get into, you know, sleep. I think there's so much interesting stuff that's being discovered in sleep right now. Being able to just record from large populations of cells and then be able to relate that. And when I think the coolest thing gets back to this QR code thing, because like, what we can do now is like, I can take fMRI data while you're watching a movie. Or let's do better than that. Let me get fMRI data while you use a joystick to move around in virtual reality. You're in the metaverse, whatever, right? But it's kind of a crappy metaverse, because there's always so much metaversing

• 1:41:38Speaker 01

  you can do in an MRI scanner. So you do this crappy metaversing. So now, I can take a rat, record from his hippocampus and prefrontal cortex and all these areas, with these really new electrodes, get massive amounts of data, and have it move around on a trackball in virtual reality in the same metaverse that I did, and record that rat's activity. I can get a person with epilepsy who we have electrodes in their brain anyway, to try to figure out where the seizures are coming from. If it's a healthy part of the brain, record from that person, right? And I can get a computational model. And one of the, one of the brand new members in my lab, Tyler Bond, is just doing some great stuff. He relates computer vision

• 1:42:23Speaker 01

  models and looks at the weaknesses of computer vision models and relates it to what the brain does well.

• 1:42:29Speaker 01

  And so you can actually take a ground truth, you know,

• 1:42:35Speaker 01

  code for the metaverse, basically, and you can feed in the visual information, let's say the sensory information or whatever that's coming in to a computational model that's designed to take real world inputs, right? And you could basically tie them all together by virtue of the state spaces that you're measuring in neural activity and these different formats, these different species and in the computational model, which is just, I just find that mind blowing. You could do different kinds of analyses on language and basically come up with just like the, basically it's the guts of LLMs, right? You have, you could do analyses on language and you could do analyses on, you know, sentiment

• 1:43:18Speaker 01

  analyses of emotions and so forth and put all this stuff together. I mean, it's, it's almost too much, but if you do it right and you do it in a theory-driven way, as opposed to just throwing all the data at the wall and see what sticks. I mean, that to me is just exceptionally powerful.

• 1:43:35Lex Fridman?

  So you can take fMRI data in, across species and across different types of humans or conditions of humans and what, find, construct models that help you find the commonalities? Or like the core thing that makes somebody navigate through the metaverse, for example?

• 1:43:56Speaker 01

  Yeah, yeah, I mean, more or less. I mean, there's a lot of details, but yes, I think, and not just fMRI, but you can relate it to, like I said, recordings from large populations of neurons that could be taken in a human or even in a non-human animal that is, you know, where you think it's an anatomical homologue. So that's just mind blowing to me.

• 1:44:17Lex Fridman?

  What's the similarities in humans and mice?

• 1:44:22Lex Fridman?

  I was smashing pumpkins, uh, we're all just rats in a cage. Is that smashing pumpkins?

• 1:44:28Speaker 01

  Despite all of your rage.

• 1:44:30Lex Fridman?

  Is that smashing pumpkins, I think?

• 1:44:32Speaker 01

  Despite all of your rage at GIFs, you're still just a rat in a cage.

• 1:44:36Lex Fridman?

  Oh, yeah. All right. Good callback. Anyway.

• 1:44:38Speaker 01

  Good callback. See, these memory retrieval exercises I'm doing are actually helping you build a lasting memory of this conversation.

• 1:44:46Lex Fridman?

  And it's strengthening the visual thing I have of you with James Brown on stage. It's just coming stronger and stronger by the second. Um, but anyway.

• 1:44:57Lex Fridman?

  But animal studies work here as well.

• 1:45:00Speaker 01

  Yeah, yeah. So, okay, so let's go to the, um, so I think recent, I've got, you know, great colleagues who I talk to who study memory in mice, you know, and there's some, uh, um, one of the valuable things in those models is you can study neural circuits in an enormously targeted way because you could do these genetic studies, for instance, where you can manipulate like particular groups of neurons and it's just getting more and more targeted to the point where you could actually turn on a particular kind of memory just by activating a particular set of neurons that was active during an experience, right? So there's a lot of conservation of some of these neural circuits across, you know,

• 1:45:45Speaker 01

  um, evolution in mammals, for instance. Um, and then some people would even say that there's genetic mechanisms for learning that are conserve even going back far, far before. But let's go back to the mice and humans question, right? Um, there's a lot of differences. So for one thing, the sensory information is very different. Uh, mice and rats explore the world largely through, um, smelling, olfaction. Uh, but they also have vision that's kind of designed to kind of catch death from above. So it's like a very big view of the world. And we move our eyes around in a way that focuses on particular spots in space where you get very high resolution from a very limited set of spots in space. So that makes us very different in that way.

• 1:46:30Speaker 01

  We also have all these other structures of social animals that allow us to, um, respond differently. There's language. There's like, um, you know, so you name it. There's obviously gobs of differences. Humans aren't just giant rats. There's much more complexity to us. Timescales are very important. So. Primate brains and human brains are especially good at integrating and and holding on to information across longer and longer periods of time, right? And and also, you know, finally, it's like our history of training data, so to speak, is very, very different than, you know, I mean, humans' world is very different than a wild mouse's world.

• 1:47:11Speaker 01

  And a lab mouse's world is extraordinarily impoverished relative to an adult human, you know?

• 1:47:16Lex Fridman?

  But still, what can you understand by studying mice? I mean, just basic, almost behavioral stuff about memory?

• 1:47:22Speaker 01

  Well, yes, but that's very important, right? So you can understand, for instance, how do neurons talk to each other? That's a really big, big question. Neural computation, in and of itself, you'd think it's the most simple question, right? Not at all. I mean, it's a big, big question. And understanding how two parts of the brain interact, meaning that it's not just one area speaking. It's not like, you know, it's not like Twitter, where one area of the brain is shouting and then another area of the brain is just stuck listening to this crap. It's like they're actually interacting on the millisecond scale, right? How does that happen? And how do you regulate those interactions, these dynamic, you know, interactions?

• 1:48:05Speaker 01

  We're still figuring that out, but that's going to be coming largely from model systems that are easier to understand. You can do manipulations, like drug manipulations, to manipulate circuits and, you know, use viruses and so forth, and lasers to turn on circuits that you just can't do in humans. So I think there's a lot that can be learned from mice. There's a lot that can be learned from non-human primates. And then there's a lot that you need to learn from humans. And I think, unfortunately, some of the people in the National Institutes of Health think you can learn everything from the mouse. It's a, like, why study memory in humans when I could study learning in a mouse? And just like, oh, my God, I'm gonna get my funding from somewhere else.

• 1:48:47Lex Fridman?

  So. Well, let me ask you some random fascinating questions.

• 1:48:51Speaker 01

  Yeah, sure.

• 1:48:53Lex Fridman?

  How does déjà vu work?

• 1:48:55Speaker 01

  So deja vu is, it's actually, one of these things, I think that some of the surveys suggest that like 75% of people report having a deja vu experience one time or another. I don't know where that came from, but I've polled people in my class and most of them say they've experienced deja vu. It's this kind of sense that I've experienced this moment sometime before, I've been here before. And actually, there's all sorts of variants of this. The French have all sorts of names for various versions of the chameau vu. Parle vu, I don't know.

• 1:49:30Speaker 01

  All these different vus. Yeah. But deja vu is this sense that it can be like, almost disturbing, intense sense of familiarity. So there is a researcher named Wilder Penfield. Actually, this goes back even earlier to some of the earliest, like, Hewings Jackson was this neurologist who first, who did a lot of the early characterizations of epilepsy. And one of the things he notices in epilepsy patients, some group of them, right before they would get a seizure, they would have this intense sense of deja vu. So it's this artificial sense of familiarity. It's a sense of having a memory that's not there.

• 1:50:11Speaker 01

  Right? And so what was happening was there is electrical activity in certain parts of these brains. And so this guy Penfield, later on, when he was trying to look for, how do we map out the brain to figure out which parts we want to remove and which parts don't we? He would stimulate parts of the temporal lobes of the brain and find you could elicit the sense of deja vu. Sometimes you'd actually get a memory that a person would re-experience this from electrically stimulating some parts. Sometimes they just have this intense feeling of being somewhere before. And so one theory which I really like is, Is that in higher order areas of the brain that are integrating from many, many

• 1:50:51Speaker 01

  different sources of input, what happens is, is that they're tuning themselves up every time you process a similar input, right? And so that allows you to just get this kind of affluent sense that I'm very familiar, you're very familiar with this place, right? And so just being here, you're not going to be moving your eyes all over the place because you kind of have an idea of where everything is. And that fluency gives you a sense of like, I'm here. Now I wake up in my hotel room and I have this very unfamiliar sense of where I am, right? But you know, there's a great set of studies done by Anne Cleary at Colorado State where she created these virtual reality environments. And we'll

• 1:51:33Speaker 01

  go back to the metaverse. Imagine you go through a virtual museum, right? And then she would put people in virtual reality and have them go through a virtual arcade. But the map of the two places was exactly the same. She just put different skins on them. So one looks different than the other, but they've got same landmarks and same places, same objects and everything, but carpeting, colors, theme, everything's different. People will often not have any conscious idea that the two are the same, but they could report this very intense sense of déjà vu. So it's like a partial match that's eliciting this kind of a sense of familiarity. And, and that's why, you know, in patients who have

• 1:52:15Speaker 01

  epilepsy that affects memory, you get this artificial sense of familiarity that happens. And so we think that, and again, this is just one theory amongst many, but we think that's, we get a little bit of that feeling. It's not enough to necessarily give you déjà vu, even for very mundane things, right? So it's like if I

• 1:52:37Speaker 01

  Tell you the word rutabaga, your brain's going to work a little bit harder to catch it than if I give you a word like apple. Right? Um, and that's because you hear apple lots. Your brain's very tuned up to process it efficiently, but rutabaga takes a little bit longer and more intense. And you can actually see a difference in brain activity in areas in the temporal lobe when you hear a word, just based on how frequent it is in the English language. So we think it's tied to this basic, it's a basically a byproduct of our mechanism of just learning, doing this error-driven learning as we go through life to become better and better and better, to process things more and more efficiently.

• 1:53:15Lex Fridman?

  So I guess deja vu is just thinking, uh, extra elevated, the stuff coming together, firing for this artificial memory as if it's the real memory. This, I mean, why does it feel so intense?

• 1:53:29Speaker 01

  Uh, well, it doesn't happen all the time, but I think what may be happening is it's such a, it's a partial match to something that we have. And it's not enough to trigger that sense of, you know, that ability to pull together all the pieces. But it's a close enough match to give you that intense sense of familiarity without the recollection of exactly what happened when.

• 1:53:52Lex Fridman?

  But it's also like a spatio-temporal familiarity. So like, it's also in time. Like there's a weird blending of time that happens. Um, and we'll, we'll probably talk about time because I, I think that's a really interesting idea, how time relates to memory. But, um, you also kind of, artificial memory brings to mind this idea of false memories. That comes in all kinds of contexts, but how do false memories form?

• 1:54:20Speaker 01

  Well, I like to say there's no such thing as true or false memories. Right? It's like, uh, um, Johnny Rotten from the Sex Pistols. He had a saying that's like, I don't believe in false memories any more than I believe in false songs. Right? It's like, um, and so the basic idea is, is that we have these memories that reflect bits and pieces of what happened, as well as our inferences and theories, right? So I'm a scientist and I collect data, but I use, I use theories to make sense of that data. And so a memory is kind of a mix of all these things. So where memories can go off the deep end and become what we would call conventionally as false memories are sometimes little distortions where we filled in the blanks,

• 1:55:04Speaker 01

  the gaps in our memory, based on things that we know, but don't actually correspond to what happened, right? So if I were to tell you that I'm like, you know, a story about this person who's like worried that they have cancer or something like that, and then, you know, they see a doctor and the doctor says, "Well, things are very much like you would have expected," or like, you know, "what you were afraid of," or something. When people remember that, they'll often remember, "Well, the doctor told the patient that he had cancer," even if that wasn't in the story, because they're infusing meaning into that story, right? So that's a minor distortion.

• 1:55:45Speaker 01

  But what happens is, is that sometimes things can really get out of hand, where people have trouble telling the difference in things that they've imagined versus things that happen. But also, as I told you, the act of remembering can change the memory. And so what happens then is you can actually be exposed to some misinformation. And so Elizabeth Loftus was a real pioneer in this work, and there's lots of other work that's been done since. But basically, it's like if you remember some event, and then I tell you something about the event, later on, when you remember the event, you might remember some original information from the event, as well as some information about what I told you.

• 1:56:27Speaker 01

  And sometimes, if you're not able to tell the difference, that information that I told you gets mixed into the story that you had originally. So now I give you some more misinformation, or you're exposed to some more information somewhere else, and eventually, your memory becomes totally detached from what happened. And so sometimes you can have cases where people, this is very rare, but you can do it in lab too, or like a significant, not everybody, but you know, a chunk of people will fall for this, where you can give people... Misinformation about an event that never took place. And as they keep trying to remember that event more and more, what happens?

• 1:57:08Speaker 01

  They start to imagine, they start to pull up things from other experiences they've had. And eventually they can stitch together a vivid memory of something that never happened. Because they're not remembering an event that happened. They're remembering the act of trying to remember what happened. And basically putting it together into the wrong story.

• 1:57:29Lex Fridman?

  This is fascinating because this could probably happen at the a collective level. Like, this is probably what successful propaganda machines aim to do. This creating false memory across thousands, if not millions, of minds.

• 1:57:45Speaker 01

  Yeah, absolutely. I mean, this is exactly what they do. And so all these kind of foibles of human memory get magnified when you start to have social interactions. There's a whole literature on something called social contagion, which is basically when misinformation spreads like a virus. Like, you remember the same thing that I did. But I give you a little bit of wrong information. Then that becomes part of your story of what happened. Because once you and I share a memory, like, I tell you about something I've experienced and you tell me about your experience of the same event. It's no longer your memory or my memory, it's our memory. And so now the misinformation spreads. And the more you trust someone, or the more powerful that person is,

• 1:58:29Speaker 01

  the more of a voice they have in shaping that narrative, right? And there's all sorts of interesting ways in which misinformation can happen. There's a great example of when John McCain and George Bush Jr. were in a primary. And there are these polls where they would do these, like, I guess they were like, not robocalls, but real calls where they would poll voters. But they actually inserted some misinformation about McCain's beliefs on taxation, I think. And maybe it was something about illegitimate children or something. I don't really remember. But they included misinformation in the question that they asked. Like, you know, how do you feel about the fact that he wants to do this or something?

• 1:59:13Speaker 01

  And so people would end up becoming convinced he had these, you know, policy things or these personal things that were not true, just based on the polls that were being used. So it was a case where, interestingly enough, The people who are using misinformation were actually ahead of the curve relative to the scientists who are trying to study these effects in memory.

• 1:59:37Lex Fridman?

  Yeah, it's, um, it's really interesting. So it's not just about truth and falsehoods, like us as intelligent reasoning machines, but it's the formation of memories where they become like visceral. You can rewrite history. If you just look throughout the 20th century, uh, some of the dictatorships with Nazi Germany with, uh, with the Soviet Union, effective propaganda machines can rewrite our conceptions of history, how we remember our own culture, our upbringing, all this kind of stuff. And you could do quite a lot of damage in this way. And then there's probably some kind of social contagion happening

• 2:00:19Lex Fridman?

  there. Like certain ideas that may be initiated by the propaganda machine can spread faster than others. You could see that in modern day, certain conspiracy theories, there's just something about them that they are like really effective at spreading. There's something sexy about them to people to, to where, uh, something about the human mind eats it up and then uses that to construct memories as almost as if they almost were there to witness whatever the content of the conspiracy theory is. It's fascinating because once you feel like you remember a thing, I feel like there's a certainty, there's a, it emboldens

• 2:01:01Lex Fridman?

  you to like say stuff like you really like, it's not just you believe an idea is true or not. You're like, it's at the core of your being that you, you feel like you were there to watch the thing happen.

• 2:01:16Speaker 01

  Yeah. I mean, there's so much in what you're saying. I mean, one of the things is, is that. People's sense of collective identity is very much tied to shared memories. If we have a shared narrative of the past, or even better, if we have a shared past, we will feel more socially connected with each other and I will feel part of this group. They're part of my tribe if I remember the same things in the same way. And you brought up this weaponization of history. And you know, it really speaks to, I think, one of the parts of memory, which is that if you have a belief, you will find, and you have a goal in mind, you will find stuff in memory that aligns with it and you won't see the parts in memory that don't.

• 2:01:58Speaker 01

  So a lot of the stories we put together are based on our perspectives. Right? And so let's, let's just zoom out for the moment from like misinformation. Take something even more fascinating, but not as like scary. I was reading Tan Viet Nguyen, but he wrote a book about the collective memory of the Vietnam War. He's a Vietnamese immigrant who was flown out as, after the war was over. And so he went back to his family to get their stories about the war. And they called it the American War, not the Vietnam War, right? And that just kind of blew my mind, having grown up in the US and always heard about it as the Vietnam War, but of course they call it the American War because that's what

• 2:02:43Speaker 01

  happened. America came in, right? And that's based on their perspective, which is a very valid perspective. And so that just gives you this idea of the way we put together these narratives based on our perspectives. And I think the, the opportunities that we can have in memory is if we bring groups together from different perspectives and we allow them to talk to each other and we allow ourselves to listen. I mean, right now you'll hear a lot of just jammering, you know, people going blah, blah, blah about free speech, but they just want to listen to themselves, right? It's like, let's face it, the old days before people were supposedly woke, they were trying

• 2:03:27Speaker 01

  to ban Two Live Crew or, you know, just think about Letty Bruce got canceled for cursing. Jesus Christ, you know? It's like, this is nothing new.

• 2:03:36Lex Fridman?

  Yeah.

• 2:03:36Speaker 01

  People don't like to hear things that disagree with them, but.

• 2:03:42Speaker 01

  If you're in a, I mean, you can see two situations in groups with memory. One situation is you have like people who are very dominant, who just take over the conversation. And they, basically what happens is the group remembers less from the experience and they remember more of what the dominant narrator says, right? Now, if you have a diverse group of people, and I don't mean diverse in necessarily the human resources sense of the word, I mean diverse in any way you want to take it, right? But diverse in every way, hopefully. And you give everyone a chance to speak and everyone's being appreciated for their unique contribution. You get more accurate memories and you get more information from it, right? Even two people who come from very similar backgrounds, if you can appreciate the unique

• 2:04:27Speaker 01

  contributions that each one has, you can do a better job of generating information from memory. And that's a way to inoculate ourselves, I believe, from misinformation in the modern world. But like everything else, it requires a certain tolerance for discomfort. And I think when we don't have much time, and I think when we're stressed out, and when we are just tired, it's very hard to tolerate discomfort.

• 2:04:53Lex Fridman?

  And I mean, social media has a lot of opportunity for this because it enables this distributed one-on-one interaction that you're talking about where everybody has a voice. But still, our natural inclination, you see this on social media, is there's a natural clustering of people and opinions and you just kind of form these kind of bubbles. I think that's, to me personally, I think that's a technology problem that can be solved. If there's a little bit of interaction, kind, respectful, compassionate interaction with people that have a very different memory, that respectful interaction will start to intermix the memories and ways of thinking to where you're slowly moving towards truth.

• 2:05:38Lex Fridman?

  But that's a technology problem because naturally, left our own devices, we want to cluster up in a tribe.

• 2:05:45Speaker 01

  Yeah, and that's the human problem. You know, I think a lot of the problems that come up with technology aren't the technology itself as much as the fact that people adapt to the technology in maladaptive ways. I mean, one of my fears about AI is not what AI will do, but what people will do. I mean, take text messaging, right? It's like it's a pain in the ass to text people, at least for me. And so what happens is the communication becomes very Spartan and devoid of meaning, right? It's just very telegraphic. And that's people adapting to the medium, right? I mean, look at you, you've got this keyboard, right? That's like got these like dome shaped things and you've adapted to that to communicate, right?

• 2:06:27Speaker 01

  That's not the technology adapting to you, that's you adapting to the technology. And I think, you know, one of the things I learned when Google started to introduce autocomplete in emails, I started to use it and about a third of the time I was like, this isn't what I want to say. A third of the time I'd be like, this is exactly what I wanted to say. And a third of the time I was saying, well, this is good enough, I'll just go with it, right? And so what happens is it's not that the technology necessarily is doing anything so bad as much as it's just going to constrain my language because I'm just doing what's being suggested to me. And so this is why I say, you know, kind of like my mantra for some of what I've learned about everything in memory

• 2:07:11Speaker 01

  is to diversify your training data, basically. Because otherwise you're going to, so like humans have this capability to be so much more creative than anything generative AI will put together, at least right now, who knows where this goes. But it can also go the opposite direction where people could become much, much less creative if they just become more and more like resistant to discomfort, you know, and resistant to exposing themselves to novelty, to cognitive dissonance and so forth.

• 2:07:43Lex Fridman?

  I think there is a dance between natural human adaptation of technology and the people that, the design, the engineering of that technology. So I think there's a lot of opportunity to create like this keyboard, things that on net are a positive for human behavior. So we adapt and all this kind of stuff, but when you look At the long arc of history, across years and decades, has humanity been flourishing? Are humans creating more awesome stuff? Are humans happier, all that kind of stuff? And so there, I think, technology on that is, uh, has been, and I think, maybe hope will always, will always be on that a positive thing.

• 2:08:25Speaker 01

  Do you think people are happier now than they were 50 years ago or 100 years ago?

• 2:08:29Lex Fridman?

  Yes, yes.

• 2:08:31Speaker 01

  I don't know about that.

• 2:08:32Lex Fridman?

  I think humans in general like to reminisce about the past, like the times are better. And complain about the weather today or complain about whatever today, because we, there's this kind of complainy engine that's just, there's so much pleasure in saying, you know, life sucks for some reason.

• 2:08:54Speaker 01

  That's why I love punk rock.

• 2:08:56Lex Fridman?

  Exactly. I mean, there's something in humans that loves complaining, even about trivial things. But complaining about change, complaining about everything. But ultimately, I think, on net, on every measure, uh, things are getting better. Life is getting better.

• 2:09:15Speaker 01

  Oh, life is getting better, but I don't know necessarily that tracks people's happiness, right? I mean, I would argue that maybe, who knows? I don't know this, but I wouldn't be surprised if people in hunter-gatherer societies are happier. I mean, I wouldn't be surprised if they're happier than people who have access to modern medicine and email and cell phones.

• 2:09:38Lex Fridman?

  Well, I don't think there's a question whether you take hunter-gatherer folks and put them into modern day and give them enough time to adapt, they would be much happier. The question is, in terms of every single problem they've had is now solved. There's now food, there is guarantee of survival, shelter, and all this kind of stuff. So what you're asking is a deeper sort of biological question. Do we want to be, oh, Werner Herzog and the movie Happy People, Life in the Tiger? Do we want to be busy 100% of our time, hunting, gathering, surviving, worried about the next day? Maybe that constant struggle ultimately creates a more fulfilling life? I don't know, but I do know this modern society allows us.

• 2:10:23Lex Fridman?

  To when we're sick, to find medicine, to find cures. When we're hungry, to get food, much more than we did even 100 years ago. And there's many more activities that you could perform or create of all this kind of stuff that enables the flourishing of humans at the individual level. Whether that leads to happiness, I mean, that's a very deep philosophical question. Maybe struggle, deep struggle is necessary for happiness.

• 2:10:55Speaker 01

  Or maybe cultural connection, you know, maybe it's about like functioning in social groups that are meaningful and like having time. But I do think this is, there is an interesting memory related thing, which is that if you look at like things like reinforcement learning, for instance, you're not learning necessarily every time you get a reward, if it's the same reward, you're not learning that much. You mainly learn if it deviates from your expectation of what you're supposed to get. Right. So it's like you get a paycheck every, you know, month from MIT or whatever. Right. And it's like, you're kind of, you probably don't even kind of get excited about it when you get the paycheck. But if they cut your salary, you're going to be pissed.

• 2:11:37Speaker 01

  And if they increase your salary, you go, oh, good, I got a bonus, you know? And that adaptation and that ability that basically you learn to expect these things, I think, is a major source of, I guess, it's a major way in which we're kind of more, in my opinion, wired to strive and not be happy, to be in a state of wanting. And if, you know, so people talk about dopamine, for instance, being this pleasure chemical. And it's like, there's a lot of compelling research to suggest it's not about pleasure at all. It's about the discomfort that energizes you to get things, to seek a reward.

• 2:12:19Speaker 01

  Right. And so you could give an animal that's been deprived of dopamine, a reward and oh yeah, I enjoy it, it's pretty good, but they're not going to do anything to get it, you know? And just one of the weird things in our research is, is we, I got into curiosity from a postdoc in my lab, Matthias Gruber. And one of the things that we found is when we gave people a question, like a trivia question that they wanted the answer to. The question, the more curious people were about the answer, the more activity in these dopamine-related circuits in the brain we would see. And again, that was not driven by the answer per se, but by the question. So it was not about getting the information, it was about the drive to seek

• 2:13:04Speaker 01

  the information. But it depends on how you take that. If you get this uncomfortable gap between what you know and what you want to know, you could either use that to motivate you and energize you, or you could use it to say, I don't want to hear about this. This disagrees with my beliefs. I'm going to go back to my echo chamber, you know?

• 2:13:24Lex Fridman?

  Yeah. I like what you said, that maybe we're designed to be in a kind of constant state of wanting, which by the way is a pretty good either band name or rock song name, State of Wanting.

• 2:13:40Speaker 01

  That's like a hardcore band name. Yeah, yeah, yeah.

• 2:13:43Lex Fridman?

  Yeah, it's pretty good.

• 2:13:43Speaker 01

  But I also like the Hedonic treadmill.

• 2:13:46Lex Fridman?

  Hedonic treadmill is pretty good.

• 2:13:47Speaker 01

  Yeah, yeah, we could use that for like our techno project, I think.

• 2:13:52Lex Fridman?

  You mean the one we're starting?

• 2:13:53Speaker 01

  Yeah, exactly.

• 2:13:54Lex Fridman?

  Okay, great. We're going on tour soon. This is our announcement.

• 2:14:02Speaker 01

  We could build a false memory of a show, in fact, if you want. Let's just put it all together. So we don't even have to do all the work to play the show. We just create a memory of it and might as well happen because the remembering self is in charge anyway.

• 2:14:15Lex Fridman?

  So let me ask you about, we talked about false memories, but you know, in the legal system, false confessions. I remember reading 1984 where, sorry for the dark turn of our conversation, but through torture, you can make people say anything and essentially remember anything. I wondered to which degree there's like truth to that. If you look at the torture that happened in the Soviet Union for confessions, all that kind of stuff, how much can you really get people to really? Yeah, to force false memories, I guess.

• 2:14:51Speaker 01

  Yeah, I mean, I think there's a lot of history of this, actually, in the criminal justice system. You might have heard the term the third degree. If you actually look it up, historically, it was a very intense set of beatings and starvation, physical demands that they would place on people to get them to talk. And you know, there was certainly a lot of work in the that's been done by the CIA in terms of enhanced interrogation techniques. And from what I understand, the research actually shows that they just produce what people want to hear, not necessarily the information that is being looked for.

• 2:15:34Speaker 01

  And the reason is, is that, I mean, there's different reasons. I mean, one is people just get tired of being tortured and just say, whatever. But another part of it is, is that you create a very interesting set of conditions where there's an authority figure telling you something that you did this, we know you did this, we have witnesses saying you did this. So now you start to question yourself. Then they put you under stress. Maybe they're not feeding you. Maybe they're kind of like making you be cold or, you know, exposing you to like, music that you can't stand or something, whatever it is, right? It's like they're, they're creating this physical stress. And so stress starts to act on, you know, starts to down regulate the prefrontal cortex. You're not necessarily

• 2:16:19Speaker 01

  as good at monitoring the accuracy of stuff. Then they start to get nice to you and they say, imagine, you know, okay, I know you don't remember this, but maybe we can walk you through how it could have happened. And they feed you the information. And so you're in this weakened mental state and you're being encouraged to imagine things by people who give you a plausible scenario. And at some point, certain people can be very coaxed into creating a memory for something that never happened. And, and there's actually some pretty convincing cases out there where you don't know exactly the truth. There's a sheriff, for instance, who came to believe that He had a false memory, I mean, that he had a memory of doing sexual abuse based on,

• 2:17:03Speaker 01

  you know, essentially, I think it was, um, you know, I'm not going to tell the story because I don't remember it well enough to necessarily accurately give it to you, but people could look this stuff up. There are definitely stories out there like this where people confess to crimes that they just didn't do and objective evidence came out later on.

• 2:17:23Speaker 01

  But there's a basic recipe for it, which is you feed people the information that you want them to remember. You stress them out. You have an authority figure kind of like pushing this information on them. Uh, or you motivate them to produce the information you're looking for, and that pretty much over time gives you what you want.

• 2:17:44Lex Fridman?

  It's really tragic that centralized power can, can use these kinds of tools to destroy lives. Sad.

• 2:18:00Lex Fridman?

  Since there's a theme about music throughout this conversation, one of the best topics for songs is heartbreak, love in general, but heartbreak. Why and how do we remember and forget heartbreak? Asking for a friend.

• 2:18:15Speaker 01

  Oh God, that's so hard to, asking for a friend. I love that.

• 2:18:22Speaker 01

  Oh, it's such a hard one. Well, so, I mean, part of this is we tend to go back to particular times that are the more emotionally intense periods.

• 2:18:36Speaker 01

  And so that's a part of it. And again, memory is designed to kind of capture these things that are biologically significant and attachment is a, you know, big part of biological significance for humans, right? Human relationships are super important. And sometimes that heartbreak comes with chain, massive changes in your beliefs about somebody, say if they cheated on you or something like that. Or regrets and you kind of ruminate about things that you've done wrong.

• 2:19:06Speaker 01

  There's really so many reasons, though, but you know, I mean, I've had this.

• 2:19:12Speaker 01

  My first pet I had as you know, was we got it for a wedding present as a cat and got it after like, but it died of FIP when it was four years old. And you know, I just would see her everywhere around the house, you know, we got another cat that we got a dog, dog eventually died of cancer and the cat just died recently. And, you know, so we got a new dog because I kept seeing the dog around and I was just so heartbroken about this. But I still remember the pets that died. It just comes back to you. I mean, it's part of this. I think there's also something about attachment that's just so crucial that drives, again, these things that we want to remember

• 2:19:56Speaker 01

  and that gives us that longing sometimes. Sometimes it's also not just about the heartbreak, but about the positive aspects of it, right? Because the loss comes from not only the fact that the relationship is over, but you had all of these good things before that you can now see in a new light, right? And so, part of, one of the things that I found from my clinical background that really I think gave me a different perspective on memory is so much of the therapy process was guided towards reframing and getting people to look at the past in a different way, not by imposing, changing people's memories or not by imposing

• 2:20:37Speaker 01

  an interpretation, but just offering a different perspective and maybe one that's kind of more optimized towards learning and, you know, and appreciation, maybe, or gratitude, whatever it is, right? That gives you a way of taking, I think you said it in the beginning, right? Where you can have this kind of like dark experiences and you can use it as training data to, you know, grow in new ways. But it's hard.

• 2:21:05Lex Fridman?

  This, I often go back to this moment, this show Louis with Louis CK, where he's all heartbroken about a breakup with a woman he loves. And an older gentleman tells him that that that's actually the best part, that heartbreak, because you get to intensely experience how valuable this love was. He says, the worst part is forgetting it is actually when you get over the heartbreak. That's the worst part. So I sometimes think about that because, you know, having the love and losing it, like the losing it is when you sometimes feel it the deepest,

• 2:21:49Lex Fridman?

  which is an interesting way to celebrate the past and relive it. It's it sucks that you don't have a thing, but when you don't have a thing, it's a it's a good moment to viscerally experience the memories of something that you now appreciate even more.

• 2:22:08Speaker 01

  So you don't believe that an owner of a lonely heart is much better than an owner of a broken heart? You think an owner of a broken heart is better than the owner of a lonely heart?

• 2:22:17Lex Fridman?

  Yes, for sure. I think so. I think so. But I'm gonna have to, day by day. I don't know. I'm gonna have to listen to some more Bruce Springsteen to figure that one out.

• 2:22:27Speaker 01

  Well, you know, it's funny because it's like after I turned 50, I think of death all the time. Like, I just think that, you know, I'm in like, I probably, I have fewer, probably a fewer years ahead of me than I have behind me, right? And so you think about, I think about one thing, which is, what are the memories that I want to carry with me for the next period of time? And also about like, just the fact that everything around me could be, you know, I know more people who are, you know, dying for various reasons. And so, I'm not lots, I'm not that old, right? But, you know, it's, it's something I think about a lot. And I'm reminded of like, how I talked to somebody who's like, you know, is a Buddhist.

• 2:23:10Speaker 01

  And I was like, you know, the whole idea of Buddhism is renouncing attachments. Some way, the idea of Buddhism is like staying out of the world of memory and staying in the moment. Right? And they talked about, you know, it's like, how do you, how do you renounce attachments to the people that you love, right? And they're just saying, well, I appreciate that I have this moment with them. And knowing that they will die makes me appreciate this moment that much more. I mean, you said something similar, right? In your daily routine that you think about things this way, right?

• 2:23:41Lex Fridman?

  Yeah, I meditate on mortality every day.

• 2:23:45Lex Fridman?

  But I don't know, at the same time, that really makes you appreciate the moment and live in the moment. And I also appreciate the full, deep roller coaster of suffering involved in life. The little and the big too. So I don't know. The Buddhist kind of removing yourself from the world, or the Stoic removing yourself from the world, the world of emotion. I'm torn about that one. I'm not sure.

• 2:24:12Speaker 01

  Well, you know, this is where Hinduism and Buddhism, or at least some strains of Hinduism and Buddhism differ. In Hinduism, like if you read the Bhagavad Gita, the philosophy is not one of renouncing the world, because the idea is that not doing something is no different than doing something, right? So what they argue, and again, you could interpret in different ways, positive and negative. But the argument is, is that you don't want to renounce action, but you want to renounce the fruits of the action. You don't do it because of the outcome. You do it because of the process. Because the process is part of the balance of the world that you're trying to preserve, right? And of course, you could take that different ways.

• 2:24:56Speaker 01

  But I really think about that from time to time in terms of like, you know, letting go of this idea of does this book sell? Or trying to, you know, like impress you and get you to laugh at my jokes or whatever, and just be more like I'm sharing this information with you and, you know, getting to know you or whatever it is. But it's, it's hard, right? It's like, because we're so driven by the reinforcer, the outcome.

• 2:25:23Lex Fridman?

  You're just part of the process of telling the joke. And if I laugh or not, that's up to the universe to decide.

• 2:25:31Speaker 01

  Yep, it's my dharma.

• 2:25:35Lex Fridman?

  How does studying memory affect your understanding of the nature of time? So like, we've been talking about us living in the present and making decisions about the future, standing on the foundation of these memories and narratives about the memories that we've constructed. So it feels like.

• 2:25:56Lex Fridman?

  It does weird things to time.

• 2:25:58Speaker 01

  Yeah. And the reason is, is that in some sense, I think, especially the farther we go back, I mean, there's all sorts of interesting things that happen. So your sense of like, if I ask you, how different does one hour ago feel from two hours ago? You'd probably say pretty different. But if I ask you, okay, go back one year ago versus one year and one hour ago, it's the same difference in time. It won't feel very different. Right? So there's this kind of compression that happens as you look back farther in time. So that it's kind of like why when you're older, the difference between somebody who's like 50 and 45 doesn't seem as big as the difference between like 10 and five or something, right? When you're 10 years old, everything seems like it's a long period of time.

• 2:26:44Speaker 01

  Here's the point is that, you know, so one of the interesting things that I found while I was working on the book, actually, was during the pandemic, I just decided to ask people in my class when we were doing the remote instruction. So one of the things I did was I would poll people. And so I just asked people, do you feel like the days are moving by slower or faster or about the same? Almost everyone in the class said that the days were moving by slower.

• 2:27:11Speaker 01

  So then at the, I would say, okay, so do you feel like the weeks are passing by slower, faster or the same? And the majority of them said that the weeks were passing by faster. So according to the laws of physics, I don't think that makes any sense. Right? But according to memory, it did, because what happened was people were doing the same thing over and over in the same context. And without that change in context, their feeling was that they were in one long, monotonous event. And so, but then at the end of the week, you look back at that week and you say, well, what happened? I have no memories of what happened. So it must, the week just went by without even my noticing it. But that week went by during

• 2:27:56Speaker 01

  the same amount of time as an eventful week where you might've been going out, hanging out with friends on vacation or whatever. Right? It's just that nothing happened because you're doing the same thing over and over. So I feel like memory really shapes our sense of time, but it does so in part because context is so important for memory.

• 2:28:16Lex Fridman?

  Well, that compression you mentioned, it's an interesting process. Cause when I think about when I was like 12, Fifteen.

• 2:28:26Lex Fridman?

  I just fundamentally feel like the same person. It's interesting what that compression does. It makes me feel like it's all, we're all connected, not just amongst humans and spatially, but in terms, in back in time. There's a kind of eternal nature, like the timelessness, I guess, to life. It could be also a genetic thing, just from, for me. I don't know if everyone agrees to this view of time, but to me, it all feels the same.

• 2:28:55Speaker 01

  Like, you don't feel the passage of time, or?

• 2:28:58Lex Fridman?

  No, I feel the passage of time in the same way that your students did from day to day. There's certain markers that let you know that time has passed. You celebrate birthdays and so on. But the core of who I am and who others I know are or events, it like, that compression of my understanding of the world.

• 2:29:18Speaker 01

  Okay.

• 2:29:19Lex Fridman?

  Removes time, because time is not useful for the compression. So like, the details of that time, at least for me, is not useful to understanding the core of the thing, so.

• 2:29:29Speaker 01

  Maybe what it is, is that you really like to see connections between things. This is like, really what motivates me in science, actually, too. But it's like, when you start recalling the past to, you know, and seeing the connections between the past and present, now you have this kind of web of interconnected memories, right? And so, I can imagine in that sense, there is this kind of, the present is with you, right? But what's interesting about what you said, too, that struck me is that your sixteen year old self was probably very complex, you know? And I, by the way, I'm the same way, but it's like, it really is the source of a lot of darkness for me, so.

• 2:30:12Speaker 01

  But, uh, but when, like, you can look back at, like, let's say you hear a song that you used to play, like, before you would go do a sports thing or something like that. And you might not think of yourself as an athlete, but once you, you get back to that mental, you mentally time travel to that particular thing, you open up this little compartment of yourself that wasn't there before, right? That didn't seem accessible for. Dan Schacter's lab did this really cool study where they would ask people to either remember doing something altruistic or imagine doing something altruistic. And that act made them more likely to want to do things for other people.

• 2:30:54Speaker 01

  So that act of mental time travel can change who you are in the present. And we tend to think of, this goes back to that illusion of stability. And we tend to think of memory in this very deterministic way, that I am who I am because I have this past. But we have a very multifaceted past and can access different parts of it and change in the moment based on whatever part we want to reach for, right?

• 2:31:20Lex Fridman?

  How does nostalgia connect into this? Like this desire and pleasure associated with going back?

• 2:31:30Speaker 01

  Yeah, so my friend Felipe de Brigard wrote this, and it just like blew my mind, where the word nostalgia was coined by a Swiss physician who was actually studying traumatized soldiers. And so he described nostalgia as a disease. And the idea was it was bringing these people extraordinarily unhappiness because they're remembering how things used to be. And I think it's very complex. So as people get older, for instance, nostalgia can be an enormous source of happiness, right? And being nostalgic can improve people's moods in the moment. But it just depends on what they do with it.

• 2:32:11Speaker 01

  Because what you can sometimes see is nostalgia has the opposite effect of thinking, those were the good old days and those days are over, right? It's like, America used to be so great and now it sucks. Or, you know, my life used to be so great when I was a kid and now it's not, right? And you're selectively remembering the things that, I mean, we don't realize how selective our remembering self is. And so, you know, I lived through the seventies, it sucked. Like partly it sucked more for me, but I would say that even otherwise, it's like there's all sorts of problems going on, gas lines, people were like, you know, worried about like Russia, nuclear war, blah, blah, blah. So, I mean, it's just this idea that

• 2:32:55Speaker 01

  people have about the past can be very useful if it brings you happiness in the present. But if it narrows your worldview in the present, you're not aware of those biases that you have, you will end up, you can end up, it can be toxic, right? Either at a personal level or at a collective level.

• 2:33:15Lex Fridman?

  Uh, let me ask you both a practical question and an out there question. So let's start with the more practical one. What are your thoughts about BCI's brain computer interfaces and the work that's going on with Neuralink? We talked about electrodes and different ways of measuring the brain. And here Neuralink is working on basically two-way communication with the brain. And the more out there question will be like, where does this go? But more practically in the near term, what do you think about Neuralink?

• 2:33:44Speaker 01

  Yeah, I mean, I can't say specifics about the company because I haven't studied it that much. But I mean, I think there's two parts of it. So one is they're developing some really interesting technology, I think with these like surgical robots and things like that. BCI though, has like a whole lot of innovation going on. I'm not necessarily seeing any scientific evidence from Neuralink. And maybe that's just because I'm not looking for it, but I'm not seeing the evidence that they're anywhere near where the scientific community is. And there's lots of startups that are doing incredibly innovative stuff. One of my colleagues, Sergey Savisky, is just like a genius in this area and they're working on it. I think speech prosthetics like that are incorporating, you know, decoding

• 2:34:28Speaker 01

  techniques with AI and, you know, movement prosthetics is just like the, the rate of progress is just enormous. So part of the technology is having good enough data and understanding which data to use and what to do with it, right? And then the other part of it then is the algorithms for decoding it and so forth. And, and I think- I think part of that has really resulted in some real breakthroughs in neuroscience as a result. So there's lots of new technologies like neuropixels, for instance, that allow you to harvest activity from many, many neurons from a single electrode. I know Neuralink has some technologies that are also along these lines, but I even, again, because

• 2:35:10Speaker 01

  they do their own stuff, the scientific community doesn't see it, right? But I think BCI is much, much bigger than Neuralink and there's just so much innovation happening. I think the interesting question, which we may be getting into, is I was talking to Sergey a while ago about, you know, so a lot of language is not just what we hear and what we speak, but also our intentions and our internal models. And, you know, so are you really going to be able to restore language without dealing with that part of it? And he brought up a really interesting question, which is the ethics of reading out people's intentions and understanding of the world as opposed to the more, you know,

• 2:35:54Speaker 01

  the more concrete parts of hearing and producing movements.

• 2:35:58Lex Fridman?

  Just so we're clear, because you said a few interesting things. When you say, when we talk about language and BCI is what we mean is getting signal from the brain and generating the language, say you're not able to actually speak. It's as a kind of linguistic prosthetic, it's able to speak for you exactly what you wanted to say. And then the deeper question is, well, saying something isn't just the letters, the words you're saying, it's also the intention behind it, the feeling behind, all that kind of stuff. And is it ethical to reveal that full shebang, the full context of what's going on in our in our brain? That's really, that's really interesting.

• 2:36:43Lex Fridman?

  That's really interesting. I mean, our thoughts. Is it ethical for anyone to have access to our thoughts?

• 2:36:51Lex Fridman?

  Because right now, the resolution is so low that we're okay with it, even doing studies and all this kind of stuff. But if neuroscience has a few breakthroughs to where you can start to map out the QR codes for different thoughts, for different kinds of thoughts, maybe political thoughts, you know, McCarthyism. What if I'm getting a lot of them communist thoughts, or however we want to categorize or label it? That's interesting. That's really interesting. I think ultimately, this always, the more transparency there is about the human mind, the better it is.

• 2:37:33Lex Fridman?

  But there could be always intermediate battles with how much control does a centralized entity have, like a government and so on? What is the regulation? What are the rules? What are the, what's legal and illegal? You know, if you talk about the police, whose job is to track down criminals and so on, and you look at all the history, how the police could abuse its power to control the citizenry, all that kind of stuff. So people are always paranoid, and rightfully so. It's fascinating. It's really fascinating. You know, we talk about freedom of speech, you know, freedom of thought, which is also a very important liberty at the core of this country and probably humanity, starts

• 2:38:18Lex Fridman?

  to get awfully tricky when you start to be able to collect those thoughts. But what I wanted to actually ask you is, do you think, for fun and for practical purposes, you'll be able to, we would be able to modify memories? So how difficult is it to, how far away we are from understanding the different parts of the brains, everything we've been talking about? In order to figure out, how could we adjust this memory at the crude level from unpleasant to pleasant? You talked about, we can remember the mall and the people, like the location, the people. Can we keep the people and change the place? Like this kind of stuff.

• 2:39:03Lex Fridman?

  How difficult is that?

• 2:39:05Speaker 01

  Well, I mean, in some sense, we know we can do it just behaviorally, right?

• 2:39:09Lex Fridman?

  Behaviorally, yes.

• 2:39:10Speaker 01

  Like tell you, give, you know, under certain conditions, anyway, it can give you the misinformation and then you can change the people and places and so forth, right? On the crude level, there's a lot of work that's being done on a phenomenon called reconsolidation, which is the idea that essentially, when I recall a memory, what happens is, is that the connections between the neurons and that cell assembly that give you the memory are going to be like more modifiable. And so, some people have used techniques to try to like, for instance, with fear memories, to reduce that physical visceral component of the memory when it's being activated.

• 2:39:51Speaker 01

  Right now, I think I've, as an outsider looking at the data, I think it's like mixed results. And part of it is, and this speaks to the more complex issue, is that you don't, you need somebody to actually fully recall that traumatic memory in the first place. And in order to actually modify it, then what is the memory? That is the key part of the problem. So if we go back to reading people's thoughts, what is the thought? I mean, people can sometimes look at this like behaviorists and go, well, the memory is like, I've given you A and you produce B. But I think that's a very bankrupt concept about memory. I think it's, it's much more complicated than that.

• 2:40:33Speaker 01

  And, you know, one of the things that when we started studying naturalistic memory, like memory from movies, that was so hard, was we had to change the way we did the studies. Because if I show you a movie and I show, and I watch the same movie, and you recall everything that happened, and I recall everything that happened, we might take a different amount of time to do it, we might use different words, and yet to an outside observer, we might have recalled the same thing, right? So it's not about the words necessarily, and it's not about how long we spent or whatever. There's something deeper that is there, that's this idea, but it's like, how do you understand that thought? I encounter a lot of concrete thinking that it's like,

• 2:41:16Speaker 01

  If I show a model, like, you know, the visual information that a person sees when they drive, I can basically reverse engineer driving. Well, that's not really how it works. I once saw a talk by somebody, or I saw somebody talking in this discussion of between neuroscientists and AI people. And he was saying that the problem with self-driving cars that they had in cities as opposed to highways was that the car was okay at, you know, doing the things it's supposed to. But when there are pedestrians around, it couldn't predict the intentions of people. And so that unpredictability of people was the problem that they were having in, you know, the self-driving car design because

• 2:41:59Speaker 01

  it didn't have a good enough internal model of what the people were, you know, what they were doing, what they wanted. Or what do you think about that?

• 2:42:09Lex Fridman?

  Well, I spent a huge amount of time watching pedestrians, thinking about pedestrians, thinking about what it takes to solve the problem of measuring, detecting the intention of a pedestrian, really of a human being in this particular context of having to cross a street. And it's fascinating. I think, I think it's a window into how complex social systems are that involve humans. Because, you know, I would just stand there and watch

• 2:42:49Lex Fridman?

  intersections for hours. And what you start to figure out is every single intersection has its own personality. So like, there's a history to that intersection, like jaywalking, certain intersections allow jaywalking a lot more. Because what happens is

• 2:43:09Lex Fridman?

  Were leaders and followers. So there's a regular, let's say, and they they get off the subway and they start crossing a red light and they do this every single day. And then there's people that don't show up to that intersection often and they're looking for cues of how we're supposed to behave here. And if a few people start to jaywalk and cross on a red light, they will also, they will follow. And there's just a dynamic to that intersection. There's a spirit to it. If you look at Boston versus New York versus a rural town versus even Boston, San Francisco or here in Austin, there's different personalities citywide, but there's different personalities area wide, region wide, and there's different personalities, different intersections.

• 2:43:50Lex Fridman?

  And it's it's just fascinating for for a car to be able to determine that is tricky. Now, what machine learning systems are able to do well is collect a huge amount of data. So for us, it's tricky because we get to like, understand the world with very limited information. Right. And make decisions grounded in this big foundation model that we've built of understanding how humans work. AI could literally, in the context of driving, this is where I've often been really torn in both directions. If you just collect a huge amount of data, all of that information and then compress it into a representation of how humans cross streets, it's probably all there.

• 2:44:35Lex Fridman?

  In the same way that you have a Noam Chomsky who says, no, no, no, AI can't talk, can't write convincing language without understanding language. And you know, more and more, you see large language models without quote unquote, understanding can generate very convincing language. But I think what the process of compression from a huge amount of data compressing into a representation is doing is in fact, understanding deeply. In order to be able to generate one letter at a time, one word at a time, you have to understand.

• 2:45:11Lex Fridman?

  The cruelty of Nazi Germany and the beauty of sending humans to space. And like, you have to understand all of that in order to generate, like, I'm going to the kitchen to get an apple and do that geratically correctly. You have to have a world model that includes all of human behavior.

• 2:45:28Speaker 01

  You're thinking LLM is building that world model.

• 2:45:31Lex Fridman?

  It has to in order to be good at generating one word at a time, a convincing sentence. And in the same way, I think AI that drives a car, if it has enough data, will be able to form a world model that will be able to predict correctly what the pedestrian does. But when we, as humans, are watching pedestrians, we slowly realize, damn, this is really complicated. In fact, when you start to self-reflect on driving, you realize driving is really complicated. There's like subtle cues we take about like, just, there's a million things I could say, but like one of them determining who around you is an asshole, aggressive driver.

• 2:46:14Speaker 01

  Yes, yes, I was just thinking about this, yeah.

• 2:46:17Lex Fridman?

  Or like.

• 2:46:18Speaker 01

  You can read it a mile, once you get, become a great driver, you can see it a mile away. This guy is gonna pull an asshole move in front of you.

• 2:46:26Lex Fridman?

  Exactly.

• 2:46:26Speaker 01

  He's like way back there, but you know it's gonna happen.

• 2:46:29Lex Fridman?

  And I don't know what, because we're ignoring all the other cars.

• 2:46:33Speaker 01

  Yeah.

• 2:46:33Lex Fridman?

  But for some reason, the asshole, like a red, like, like a glowing, obvious symbol is just like right there, even in the periphery vision. Because we're, again, we're usually when we're driving, just looking forward. But we're like, using the periphery vision to figure stuff out. And it's like a little puzzle that we're usually only allocating a small amount of our attention to, at least a cognitive attention to. And it's fascinating, but I think AI just has a fundamentally different suite of sensors in terms of the bandwidth of data that's coming in, that allows you to form the representation and perform inference on the representation you've, using the representation you form.

• 2:47:13Lex Fridman?

  That for the case of driving, I think it could be quite effective. But one of the things that's currently missing, even though OpenAI just recently announced adding memory.

• 2:47:26Speaker 01

  Mm hmm.

• 2:47:27Lex Fridman?

  And I did want to ask you, like, how important it is, how difficult is it to add some of the memory mechanisms that you've seen in humans to AI systems?

• 2:47:38Speaker 01

  I would say superficially not that hard, but then in a deeper level, very, very hard, because we don't understand episodic memory, right? So, uh, one of the ideas I talk about in the book is one of the oldest kind of, uh, dilemmas in computational neuroscience is what, uh, Steve Grossberg called the stability-plasticity dilemma, right? When do you say something is new and overwrite your pre-existing knowledge versus going with what you had before and making incremental changes? And so, you know, part of the problem with going through like massive, you know, I mean, part of the problem of things like if you're trying to design an LLM or something like that, is especially for English, there's so many exceptions to the rules, right?

• 2:48:23Speaker 01

  And so if you want to rapidly learn the exceptions, you're going to lose the rules. Uh, and if you want to keep the rules, you have a harder time learning the exception. And so David Marr is one of the early pioneers in, uh, computational neuroscience. And then, uh, Jay McClelland and my, uh, colleague Randy O'Reilly, some other people like, uh, Neil Cohen, all these people started to come up with the idea that maybe that's part of what we need in what the human brain is doing, is we have this kind of a, actually a fairly dumb system, which just says, this happened once at this point in time, which we call episodic memory, so to speak. And then we have this knowledge that we've accumulated from our experiences as semantic memory.

• 2:49:07Speaker 01

  So now, when we want to, we encounter a situation that's surprising and violates all our previous expectations, what happens is, is that now we can form an episodic memory here. And the next time we're in a similar situation, boom, we could supplement our knowledge with this information from episodic memory and reason about what the right thing to do is, right? So it gives us this enormous amount of flexibility to stop on a dime and change without having to erase everything we've already learned.

• 2:49:40Speaker 01

  And that solution is incredibly powerful because it gives you of the ability to learn from so much less information, really, right? And it gives you that flexibility. So one of the things I think that makes humans great is having both episodic and semantic memory. Now, can you build something like that? I mean, computational neuroscience people would say, well, yeah, you just record a moment and you just get it and you're done, right? But when do you record that moment? How much do you record? What's the information you prioritize and what's the information you don't? These are the hard questions. When do you use episodic memory? When do you just throw it away?

• 2:50:21Speaker 01

  And these are the hard questions we're still trying to figure out in people. And then you start to think about all these mechanisms that we have in the brain for figuring out some of these things. And it's not just one, but it's many of them that are interacting with each other. And then you just take not only the episodic and the semantic, but then you start to take the motivational survival things, right? It's just like the fight or flight responses that we associate with particular things or the kind of like reward motivation that we associate with certain things so forth. And those things are absent from AI. I frankly don't know if we want it. I don't necessarily want a self motivated LLM, right?

• 2:51:01Speaker 01

  It's like, and then there's the problem of how do you even like build the motivations that should guide a proper reinforcement learning kind of thing, for instance. So a friend of mine, Sam Gershman, I might be missing the quote exactly, but he basically said, you know, if I wanted to train like a typical AI model to make me as much money as possible, first thing I might do is sell my house. So it's not even just about having one goal or one objective, but just having all these competing goals and objectives, right? And then things start to get really complicated.

• 2:51:37Lex Fridman?

  Well, it's all interconnected. I mean, just even the thing you've mentioned is the moment. You know, if we record a moment, it's difficult to express concretely what a moment is, like how deeply connected it is to the. The entirety of it, maybe to record a moment, you have to make a universe from scratch. You have to have, you have to include everything. You have to include all the emotions evolved, all the context, all the things that built around it, all the social connections, all the visual experiences, all the sensory experience, all of that, all the history that came before that moment is built on. And we somehow take all of that and we compress it

• 2:52:21Lex Fridman?

  and keep the useful parts and then integrate it into the whole thing, into our whole narrative. And then each individual has their own little version of that narrative and then we collide in a social way and we adjust it and we evolve.

• 2:52:36Speaker 01

  Yeah, yeah. I mean, well, even if we want to go super simple, right? Like Tyler Bonin, who's a postdoc who's collaborating with me, he actually studied a lot of computer vision at Stanford. And so one of the things he was interested in is some people who have brain damage in areas of the brain that were thought to be important for memory. And, but they also seem to have some perception problems with particular kinds of object perception. And this is super controversial. It's how people found this effect, some didn't. And he went back to computer vision and he said, let's take the best state of the art computer vision models and let's give them the same kinds of perception tests that we were giving to these people. And then you would find the images where the computer vision models

• 2:53:20Speaker 01

  would just struggle and you would find that they just didn't do well. Even if you add more parameters, you add more layers, on and on and on, it doesn't help, right? The architecture didn't matter. It was just there, the problem. And then he found those were the exact ones where these humans with particular damage to this area called the parietal cortex, that was where they were struggling. So somehow this brain area was being, was important for being able to do these things that were adversarial to these computer vision models. So then he found that the, that it only happened if people had enough time, they could make those discriminations. But without enough time, if they just get a glance, they're just like the computer vision models.

• 2:54:04Speaker 01

  So then what he started to say was, well, maybe let's look at people's eyes, right? So computer vision model sees every pixel all at once, right? It's not, you know, and we don't, we never see every pixel all at once. Even if I'm looking at a screen with pixels, I'm not seeing every pixel at once. I'm grabbing little points on the screen by moving my eyes around and getting a very high resolution picture of what I'm focusing on and kind of a lower resolution information about everything else. But I'm choo-, I'm not necessarily choosing, but I'm directing that exploration and allowing people to move their eyes and integrate that information gave them something that the computer vision models weren't able to do.

• 2:54:48Speaker 01

  So somehow integrating information across time and getting less information at each step gave you more out of the process.

• 2:54:57Lex Fridman?

  I mean, the process of allocating attention across time seems to be a really important process. Even the breakthroughs that you get with, uh, with machine learning mostly has to do attention is all you need, is bought attention, transformers about attention. So attention is a really interesting one.

• 2:55:22Speaker 01

  Yeah.

• 2:55:23Lex Fridman?

  Well, then like, yeah, but how you allocate that attention again is like, is at the core of like what it means to be intelligent, what it means to process the world, integrate all the important things, discard all the unimportant things. Attention is at the core of it, is probably at the core of memory too. Cause there's so much sensory information, there's so much going on, there's so much going on to filter it down to almost nothing and just keep those parts and to, to, to keep those parts. And then whenever there's an error to adjust the model such that you can allocate attention

• 2:56:03Lex Fridman?

  even better to new things that would result, maybe maximize the chance of confirming the model or disconfirming the model that you have and adjusting it since then. Yeah, attention is a weird one. I was, uh, I was always fascinated. I mean, I, I got a chance to study.

• 2:56:22Lex Fridman?

  Peripheral vision for a bit and indirectly study attention through that. It's just fascinating how humans, how good humans are at looking around and gathering information.

• 2:56:32Speaker 01

  Yeah, at the same time, people are terrible at detecting changes that can happen in the environment. If they're not attending in the right way, if their predictive model is too strong, you know? So you have these weird things where like the machines can do better than the people. It's not that it's like, you know, so this is the thing is people go, oh, the machines can do this stuff. That's just like humans. It's like, well, the machines make different kinds of mistakes than the people do. And I will never be convinced unless I that, you know, we've replicated human. I don't even like the term intelligence because it is a stupid concept, but it's like, I don't think we've replicated human intelligence unless I know

• 2:57:14Speaker 01

  that the simulator is making exactly the same kinds of mistakes that people do. Because people make characteristic mistakes. They have characteristic biases. They have characteristic like, you know, heuristics that we use. And those I have yet to see evidence that chat GPT will do that.

• 2:57:33Lex Fridman?

  Since we're talking about attention, is there an interesting connection to you between ADHD and memory?

• 2:57:41Speaker 01

  Well, it's interesting for me because when I was a child, I was actually told my school. I don't know if it came from a school psychologist. They did do some testing on me, I know for like IQ and stuff like that. They, or if it just came from teachers who hated me, but they told my parents that I had ADHD. And so this was, of course, in the seventies. So basically they said like, you know, he has poor motor control and he's got ADHD. And so, and, you know, there were social issues. So like, I could have been put a year ahead in school, but then they said, oh, but he doesn't have the social. It doesn't have the social capabilities.

• 2:58:21Lex Fridman?

  Right.

• 2:58:21Speaker 01

  So I still ended up being like, you know, an outcast even in my own grade. But, um, but then like, uh, I was, so then my parents said, okay, well, they got me on a diet free of artificial colors and flavors because that was the thing that people talked about back then. So, so I am interested in this topic because I've come to appreciate now that I have many of the characteristics, if not, you know, full blown, it's like, I'm definitely time blindness, uh, rejection sensitive, you name it, they talk about it. It's like impulsive behavior. I could tell you about all sorts of fights I've gotten into in the past, uh, just you name it. Um, uh, but yeah, so ADHD is fascinating though, because right now we're seeing like more and

• 2:59:06Speaker 01

  more diagnosis of it. And I don't know what to say about that. I don't know how much of that is, um, based on kind of inappropriate expectations, especially for children and how much of that is based on true, kind of like maladaptive kinds of, uh, tendencies. But what we do know is this is that ADHD is associated with differences in prefrontal function so that attention can be both more, you're more distractible. You have harder time focusing your attention on what's relevant. And so you shift too easily, but then once you get on something that you're interested in, you can get stuck.

• 2:59:45Speaker 01

  And so, you know, the attention is this beautiful balance of being able to focus when you need to focus and shift when you need to shift. And so it's that flexibility plus stability again. Um, and that's balance seems to be disrupted in ADHD. And so as a result, memory tends to be poor in ADHD, but it's not necessarily because there's a traditional memory problem, but it's more because of this attentional issue, right? And so, um, and people with ADHD often will have great memory for the things that they're interested in and just no memory for the things that they're not interested in.

• 3:00:26Lex Fridman?

  Is there advice from your own life on how to learn and succeed from that? From just how the characteristics of your own brain with ADHD and so on? Uh, how do you learn? How do you, uh?

• 3:00:43Lex Fridman?

  Remember information, how do you flourish in this sort of education context?

• 3:00:49Speaker 01

  I'm still trying to figure out the flourishing per se, but education, I mean, being in science is enormously enabling of ADHD. It's like you're constantly looking for new things. You're constantly seeking that dopamine hit and, and that's great, you know, and they tolerate your being late for things. Nothing is really, nobody's going to die if you screw up. It's nice. It's not like being a doctor or something where you have to be like much more responsible and focused. You could just freely follow your curiosity, which is just great. But what I'd say is, is that like I'm learning now

• 3:01:26Speaker 01

  about so many things like about how to structure my activities more and basically say, okay, if I'm going to be, email is like the big one that kills me right now. I'm just constantly like shifting between email and my activities. And what happens is, is that I don't actually get the email. I just look at my email and I get stressed because I'm like, oh, I have to think about this. Let me get back to it. And I go back to something else. And so I've just got fragmentary memories of everything. Right? So what I'm trying to do is set aside a timer. Like this is my email time. This is my, you know, writing time. This is my goofing off time. And so blocking these things off,

• 3:02:09Speaker 01

  you give yourself the goofing off time. Sometimes I do that. And I sometimes I have to be flexible. Go like, okay, I'm definitely not focusing. I'm going to give myself the downtime and it's an investment. It's not like wasting time. It's an investment in my attention later on.

• 3:02:25Lex Fridman?

  And I'm very much with Callan Newport on this. He wrote Deep Work and a lot of other amazing books. He, he talks about task switching as a sort of the thing that really destroys productivity. So like, you know, switching, it doesn't even matter from what to what, but checking social media, checking email, maybe switching to a phone call and then doing work and then switching, even switching between if you're reading a paper, switching from paper to paper to paper.

• 3:02:53Speaker 01

  Yeah.

• 3:02:53Lex Fridman?

  Because like curiosity and whatever the dopamine hit from the attention switch, like limiting that, because otherwise your brain is just not capable to really like load it in. Really. Uh, do that deep deliberation. I think that's required to uh, remember things and to really think through things.

• 3:03:15Speaker 01

  Yeah, I mean, you probably see this, I imagine, in AI conferences, but definitely in neuroscience conferences. It's now the norm that people have their laptops out during talks. And, you know, conceivably they're writing, you know, they're writing notes. But in fact, what often happens, if you look at people, and we can speak from a little bit of personal experience, is you're checking email and you're like, uh, or I'm working on my own talk. But often it's like you're doing things that are not paying attention. And I have this illusion, well, I'm paying attention and then I'm going back. And then what happens is I don't remember anything from that day. It just kind of vanished because what happens is I'm creating all these artificial event boundaries.

• 3:03:57Speaker 01

  I'm losing all this executive function every time I switch. I'm getting like a few seconds slower and I'm catching up mentally to what's happening. And so instead of being in a model where you're meaningfully integrating everything and predicting and generating this kind of like rich model, I'm just catching up, you know? And so, yeah, there's great research by Melina Unkafer and Anthony Wagner on multitasking. And people can look up that talks about just how bad it is for memory. And, and, you know, it's becoming worse and worse of a problem.

• 3:04:31Lex Fridman?

  So, uh, you're a musician. Take me through, uh, how'd you get into music? Like what, what made you first fall in love with music, with creating music?

• 3:04:39Speaker 01

  I, yeah, so I started playing music just when I was like doing trumpet in school. For a school band and I would just read music and play and, you know, it was pretty decent at it, not great, but I was decent.

• 3:04:52Lex Fridman?

  How'd you go from trumpet to a?

• 3:04:55Speaker 01

  Guitar.

• 3:04:55Lex Fridman?

  To guitar, especially the kind of music you're into.

• 3:04:58Speaker 01

  Yeah, so basically in high school, yeah, so I kinda was a late bloomer to music, but just kind of MTV grew up with me. I grew up with MTV. And so then you started seeing all this stuff. And then, uh, I got into metal was kind of like my early genre. And I always reacted to just things that were loud and had a beat like, uh, I mean ADHD, right?

• 3:05:24Speaker 01

  Like, you know, everything from Sergeant Pepper's by the Beatles to like Led Zeppelin two. My dad had both. My parents had both those albums, so I'd listen to them a lot. And then like The Police, Ghost in the Machine. And but then I got into metal, Def Leppard and, you know, ACDC, Metallica, went way down the rabbit hole of speed metal.

• 3:05:48Speaker 01

  And that time was kind of like, oh, like, why don't I play guitar? I can do this. And I had friends who were doing that. And I just never got it. Like I was, I took lessons and stuff like that. But it was different because when I was doing trumpet, I was reading sheet music. And this was like, I was learning by looking, there's a thing called tablature. You know this where it's like, you see like a drawing of the fretboard with numbers? And that's where you're supposed to put your, it's kind of like paint by numbers. Right? And so, um, I learned it in a completely different way, but I was still terrible at it. And I didn't get it. It's actually taken me a long time to understand exactly what the issue was.

• 3:06:28Speaker 01

  But it wasn't until I really got into punk and I saw bands like, I saw Sonic Youth, I remember especially. And it just blew my mind because they violated the rules of what I thought music was supposed to be. I was like, this doesn't sound right. These are not power chords. And this isn't just have like a shouty verse and then a chorus part. It's not going back. This is just like weird. And then it occurred to me, you don't have to write music the way it's, people tell you it's supposed to sound. That just opened up everything for me and I was playing in a band and I was struggling with writing music because I would try to write like,

• 3:07:08Speaker 01

  you know, whatever was popular at the time and or whatever sounded like other bands that I was listening to. And somehow I kind of morphed into just like, Just grabbing a guitar and just doing stuff. And I realized a part of my problem with doing music before was I didn't enjoy trying to play stuff that other people played. I just enjoyed music just dripping out of me and just, you know, spilling out and just doing stuff. And so then I started to say, what if I don't play a chord? What if I just play like notes that shouldn't go together and just mess around with stuff? And I said, well, what if I don't do four beats going na, na, na, na, one, two, three, four, one, two, three, four, one, two, three, four, whatever I go, one, two, three, four, five,

• 3:07:51Speaker 01

  one, two, three, four, five, and started messing around with time signatures. Then I was playing in this band with a great musician who was really Brent Ritzel, who was in this band with me, and he taught me about arranging songs. And it was like, what if we take this part and instead of make it go like back and forth, we make it like a circle, or what if we make it like a straight line, you know, or zigzag, you know, just make it like nonlinear in these interesting ways. And then next thing you know, it's like the whole world sort of opens up as like the, and then what I started to realize, especially, so you could appreciate this as a musician, I think, so time signatures, right? So we are so brainwashed to think in four, four, right? Every rock song you can think of almost is in four, four.

• 3:08:35Speaker 01

  I know you're a Floyd fan, so think of Money by Pink Floyd, right?

• 3:08:39Lex Fridman?

  Yeah.

• 3:08:40Speaker 01

  Bum, bum, and a bum, bum, bum, bum, bum.

• 3:08:44Lex Fridman?

  Yeah.

• 3:08:44Speaker 01

  You feel like it's in four, four because it resolves itself, but it resolves on the, the last note of, basically it resolves on the first note of the next measure. So it's got seven beats instead of eight where the riff is actually happening.

• 3:08:59Lex Fridman?

  Interesting.

• 3:09:00Speaker 01

  But you're thinking in four because that's how we use, we're used to thinking. So the music flows a little bit faster than it's supposed to, and you're getting a little bit of prediction error every time this is happening. And once I got used to that, I was like, I hate writing in four, four because I was like, everything just feels better if I do it in seven, four, if I alternate between four and three and, and doing all this stuff. And then it's like you just, jazz music is like that, you know, they just do so much interesting stuff with this and.

• 3:09:32Lex Fridman?

  So playing with those time signatures allows you to like really break it all open and just, I guess there's something about that where it allows you to actually have fun.

• 3:09:40Speaker 01

  Yeah, yeah. And it's like, so I'm actually like a very. The genre, one of the genres we used to play in was math rock. That's what they called it. It was just like, there's so many weird time signatures.

• 3:09:51Lex Fridman?

  What is math? Oh, interesting.

• 3:09:53Speaker 01

  Yeah, so.

• 3:09:54Lex Fridman?

  That's, that's the math part of rock is what the, the mathematical disturbances of it or what?

• 3:10:00Speaker 01

  Yeah, I guess it would be like, so instead of, you might go like, instead of playing four beats in every measure, na, na, na, na, na, na, na, na. You go, na, na, na, na, na, na, na, na, na, na, na, na, na, you know? Just do these things. And then you might arrange it in weird ways so that there might be three measures of verse and then one, you know, and then five measures, of course, and then two measures. So you could just mess around with everything, right?

• 3:10:25Lex Fridman?

  What does that feel like to listen to? There's, there's something about symmetry or, or like patterns that feel good and like relaxing for us or whatever. It feels like home and disturbing that can be quite disturbing.

• 3:10:39Speaker 01

  Yeah.

• 3:10:39Lex Fridman?

  So is that, is that the feeling you would have if you were to keep messing with math rock?

• 3:10:45Speaker 01

  I mean, yeah, yeah.

• 3:10:46Lex Fridman?

  That's stressing me out just listening.

• 3:10:47Speaker 01

  Well, yeah, yeah.

• 3:10:48Lex Fridman?

  Learning about it.

• 3:10:49Speaker 01

  So, I mean, it depends. So a lot of my style of songwriting is very much like in terms of like repetitive themes, but messing around with structure. Cause I'm not a great guitarist technically. And so I don't play complicated stuff. And there's things, you can hear stuff where it's just like so complicated, you know?

• 3:11:11Speaker 01

  But often what I find is, is like having a melody or, and then adding some dissonance to it just enough. And then adding some complexity that gets, gets you going just enough. But I have a high tolerance for, for that kind of dissonance and prediction. I think, I have a theory, a pet theory, that it's like, basically you could explain most of human behavior as some people are lumpers and some people are splitters, you know? And so it's like, some people are very kind of excited when they get this dissonance and they want to like go with it. So people are just like, no, I want to lump every, you know, I don't know, maybe that's even a different thing. But it's like, basically it's like, I think some people get scared of that discomfort.

• 3:11:52Lex Fridman?

  Yeah.

• 3:11:52Speaker 01

  And I really.

• 3:11:53Lex Fridman?

  Thrive on it.

• 3:11:55Speaker 01

  You know?

• 3:11:56Lex Fridman?

  I love it. What's, uh, I, what's the name of your band now?

• 3:11:59Speaker 01

  The cover band I play in is a band called Pavlov's Dogs. And so.

• 3:12:04Lex Fridman?

  Yeah.

• 3:12:05Speaker 01

  So it's a, it's a band unsurprisingly of mostly memory researchers, neuroscientists.

• 3:12:11Lex Fridman?

  I love this. I love this so much.

• 3:12:13Speaker 01

  Actually, one of your MIT colleagues, Earl Miller, plays bass.

• 3:12:16Lex Fridman?

  Plays bass. You play like, you play, do you play rhythm or leader?

• 3:12:19Speaker 01

  Compete if you want. Maybe we could audition you.

• 3:12:21Lex Fridman?

  For audition? Oh, yeah. I'm coming for you, Earl.

• 3:12:25Speaker 01

  Earl's gonna kill me. He's like very precise though.

• 3:12:30Lex Fridman?

  I'll play triangle or something.

• 3:12:33Lex Fridman?

  Or is it, where's the cowbell? Yeah. I'll be the cowbell guy. You got, what kind of songs do you guys do?

• 3:12:39Speaker 01

  Uh, so it's mostly, uh, uh, seven, late seventies punk and eighties new wave and, and, uh, post punk. Blondie, uh, Ramones, Clash. Uh, I do, I sing, uh, Age of Consent by New Order and, and Level Terrace.

• 3:12:55Lex Fridman?

  You said you have a female singer now?

• 3:12:57Speaker 01

  Yeah, yeah, yeah. Carrie Hoffman and also, um, uh, Paula Croxton. And so they do, uh, they do, yeah. So Carrie does Blondie amazingly well. And we do like Gigantic by the Pixies. Paula does that one.

• 3:13:11Lex Fridman?

  Which song do you love to play the most? What kind of song is super fun for you?

• 3:13:16Speaker 01

  Of someone else's?

• 3:13:18Lex Fridman?

  Yeah, cover, yeah.

• 3:13:19Speaker 01

  Cover, okay. And it's one we do with Pavlov's dogs.

• 3:13:22Lex Fridman?

  Mm-hmm.

• 3:13:24Speaker 01

  I really enjoy playing I Wanna Be Your Dog by Iggy and the Stooges.

• 3:13:29Lex Fridman?

  That's a good song.

• 3:13:29Speaker 01

  Which is perfect because we're Pavlov's dogs.

• 3:13:31Lex Fridman?

  Yeah.

• 3:13:32Speaker 01

  And Pavlov, of course, was like basically created learning theory. So, you know, there's that. But also it's like, but I mean, Iggy and the Stooges, that song. So I play and sing on it, but it's just like, it devolves into total noise. And I just like, uh, fall on the floor and generate feedback. I was like, I think in the last version, it might've been that or a Velvet Underground cover in our last show. I actually, I have a guitar made of aluminum that I got made. And I thought this thing's indestructible. And so I kind of like was just, you know, moving it around. I had it upside down and all this stuff to generate feedback. And I think I broke one of the, I broke one of the tuning pegs and.

• 3:14:09Lex Fridman?

  Oh, wow.

• 3:14:09Speaker 01

  Yeah. So I managed, I've managed to break an all metal guitar. Oof, go figure.

• 3:14:15Lex Fridman?

  A bit of a big ridiculous question, but let me ask you, we've been talking about neuroscience in general. What do you, you've been studying the human mind for a long time. What do you love most about the human mind? Like, when you look at it, we look at the FMRI, just the scans and the behavioral stuff, the electrodes, you know, the psychology aspect, reading the literature on the biology side, neurobiology, all of it. When you look at it, what, what is most like beautiful to you?

• 3:14:47Speaker 01

  I think the most beautiful, but incredibly hard to put your finger on, is this idea of the internal model. That it's like, there's everything you see, and there's everything you hear and touch and taste, you know, every breath you take, whatever. But it's all connected by this like, dark energy that's holding that whole universe of your mind together, right? And without that, it's just a bunch of stuff. And somehow, we put that together, and it forms our, so much of our experience. And being able to figure out where that comes from and how things are connected to me is

• 3:15:32Speaker 01

  just amazing. But just this idea of like, that the world in front of us, we're only sampling this little bit and trying to take so much meaning from it. And we do a really good job, not perfect, I mean, you know, but that ability, to me, is just amazing.

• 3:15:48Lex Fridman?

  Yeah, it's an incredible mystery, all of it. It's funny, you said dark energy, because the same in, in astrophysics, you look out there, look at dark matter and dark energy, which is this loose term assigned to a thing we don't understand, which makes, which helps make the equations work. In terms of gravity and the expansion of the universe, in the same way, it seems like there's that kind of thing in the human mind that we're like striving to understand.

• 3:16:14Speaker 01

  Yeah, yeah. You know, it's funny that you mention that. So one of the reasons I wrote the book amongst many is is that I really felt like people needed to hear from scientists. And like COVID was just a great example of this because like people weren't hearing from scientists. One of the things I think that people didn't get was the uncertainty of science and how much we don't know. And I think every scientist lives in this world of uncertainty. And when I was writing the book, I just became aware of all of these things we don't know. And so I think of physics a lot. I think of this idea of like overwhelming majority of the stuff that's in our universe cannot be directly measured. I used to think,

• 3:16:58Speaker 01

  haha, I hate physics. Physicists get the Nobel Prize for doing whatever stupid thing. It's like there's 10 physicists out there. I'm just kidding.

• 3:17:07Lex Fridman?

  Strong words.

• 3:17:08Speaker 01

  Yeah, no, no, no, I'm kidding. The physicists who do neuroscience can be rather opinionated. So sometimes I like to dish on that.

• 3:17:14Lex Fridman?

  It's all love.

• 3:17:15Speaker 01

  It's all love. That's right. This is the ADHD talking. So, but at some point I had this aha moment where I was like, to be aware of that much that we don't know and have a bead on it and be able to go towards it. That's one of the biggest scientific successes that I could think of. You are aware that you don't know about this gigantic section, overwhelming majority of the universe, right? And I think the more what keeps me going to some extent is realizing the changing the scope of the problem and figuring out,

• 3:17:56Speaker 01

  oh, my God, there's all these things we don't know. And I thought I knew this because science is all about assumptions, right? So have you ever read The Structure of Scientific Revolutions by Thomas Kuhn?

• 3:18:08Lex Fridman?

  Yes.

• 3:18:09Speaker 01

  That's like my only philosophy really that I've read. But it's so brilliant in the way that they frame this idea of like, he frames this idea of assumptions being core to the scientific process. And the paradigm shift comes from changing those assumptions. And this idea of like finding out this kind of whole zone of what you don't know, to me is the exciting part, you know?

• 3:18:33Lex Fridman?

  Well, you are a great scientist and you wrote an incredible book. So, thank you for doing that and thank you for talking today. You've decreased the amount of uncertainty I have just a tiny little bit today and reveal the beauty of memory. This fascinating conversation. Thank you for talking today.

• 3:18:54Speaker 01

  Oh, thank you. It's been blast.

• 3:18:56Lex Fridman?

  Thanks for listening to this conversation with Charan Ranganath. To support this podcast, please check out our sponsors in the description. And now, let me leave you with some words from Haruki Murakami. Most things are forgotten over time. Even the war itself, the life and death struggle people went through is now like something from the distant past. We're so caught up in our everyday lives that events of the past are no longer in orbit around our minds. There are just too many things we have to think about every day, too many new things we have to learn. But still, no matter how much time passes, no matter what takes place in the interim,

• 3:19:41Lex Fridman?

  there are some things we can never assign to oblivion, memories we can never rub away. They remain with us forever, like a touchstone. Thank you for listening. I hope to see you next time.