Lisa Feldman Barrett: Counterintuitive Ideas About How the Brain Works | Lex Fridman Podcast #129

The following is a conversation with Lisa Feldman Barrett, a professor of psychology at Northeastern University and one of the most brilliant and bold thinkers and scientists I've ever had the pleasure of speaking with. She is the author of a book that revolutionized our understanding of emotion in the brain called How Emotions Are Made, and she's coming out with a new book called Seven and a Half Lessons about the Brain that you can and should pre order now. I got a chance to read it already and it's one of the best short, whirlwind introductions to the human brain I've ever read. It comes out on November 17, but again, if there's anybody worth supporting, it's Lisa. So please do pre order the book now. Lisa and I agreed to speak once again around the time of the book release, especially because we felt that this first conversation is good to release now, since we talk about the divisive time we're living through in the United States leading up to the election. And she gives me a whole new way to think about it from a neuroscience perspective that is ultimately inspiring of empathy, compassion, and love. Quick mention of each sponsor followed by some thoughts related to this episode. First sponsor is Athletic Greens, the all in one drink that I start every day with to cover all my nutritional bases that I don't otherwise get through my diet naturally. Second is Magic Spoon Low Carb Keto, friendly, delicious cereal that I reward myself with after a productive day.

The cocoa flavor is my favorite.

Third sponsor is Cash App, the app I use to send money to friends for food, drinks, and unfortunately for the many bets I have lost to them. Please check out these sponsors in the description to get a discount and to support this podcast. As a side note, let me say that the bold first principles way that Lisa approaches our study of the brain is something that has inspired me ever since I learned about her work and in fact I invited her to speak at the AGI series I organized at MIT several years ago. But as a little twist, instead of a lecture, we did a conversation in front of the class. I think that was one of the early moments that led me to start this very podcast.

It was scary and gratifying, which is.

Exactly what life is all about. And it's kind of funny how life turns on little moments like these that at the time, don't seem to be anything out of the ordinary. If you enjoy this thing, subscribe on YouTube, review it with five stars on Apple Podcasts, follow on Spotify, support on Patreon, or connect with me on Twitter lexfriedman and now here's my conversation with Lisa Feldman.

Barrett. Since we'll talk a lot about the brain today, do you think. Let's ask the craziest question. Do you think there is other intelligent life out there in the universe?

Honestly, I've been asking myself lately if there's intelligent life on this planet. You know, I have to think. Probabilities suggest yes. And also secretly, I think I just hope that's true. It would be really. I know scientists aren't supposed to have hopes and dreams, but I think it would be really cool. And I also think it would be really sad if it wasn't the case. If we really were alone, that would be. That would seem profoundly sad. I think so.

It's exciting to you? Not scary?

Yeah, no. You know, I take a lot of comfort and curiosity. It's a great resource for dealing with stress. So I'm learning all about mushrooms and octopuses and all kinds of stuff. And so for me, this counts, I think, in the realm of awe. But also I think I'm somebody who cultivates awe deliberately, on purpose to feel like a speck. You know, I find it a relief occasionally to feel small, to feel small in a profoundly large and interesting universe.

So maybe to dig more technically on the question of intelligence, do you think it's difficult for intelligent life to arise like it did on Earth from everything you've written and studied about the brain? How magical of a thing is it in terms of the odds it takes to arise?

Yeah. So, you know, magic is just. Don't get me wrong. I mean, I like a magic show as much as the next person. My husband was a magician at one time. But, you know, magic is just a bunch of stuff that we don't really understand how it works yet. So I would say, from what I understand, there are some major steps in the course of evolution that at the beginning of life, the step from single cell to multicellular organisms, things like that, which are really not known. I think for me, the question is not so much could it, you know, what's the likelihood that it would happen again? As much as what are the steps and how long would it take? And if it were to happen again on Earth, would we end up with the same menu of life forms that we currently have now? And I think the answer is probably no. Right. There's just so much about evolution that is stochastic and driven by chance.

But the question is whether that menu would be equally delicious, meaning there'd be rich complexity of the kind of like, would we get dolphins and humans or. Or whoever else falls in that category of weirdly intelligent, seemingly intelligent, however we define that.

Well, I think that has to be true. If you just look at the range of creatures who've gone extinct. I mean, if you look at the range of creatures that are on the Earth now, it's incredible. And it's sort of tried to say that, but it actually is really incredible. Particularly. I don't know, I mean, animals. There are animals that seem really ordinary until you watch them closely and then they become miraculous. You know, like certain types of birds which do very miraculous things, build bowers and do dances and all these really funky things that are hard to explain with a standard evolutionary story. Although people have them.

Birds are weird. They do a lot of. For mating purposes. They have a concept of beauty that I haven't quite maybe, you know, much better, but it doesn't seem to fit evolutionary arguments.

Well, it does fit well, it depends. Right. So I think you're talking about the Evolution of Beauty. The book that was written recently by. Was it from. Was that his name? Richard Frum, I think, at Yale.

Interesting. No, I didn't.

Oh, it's a great book. It's very controversial, though, because he's making the argument that the question about birds and some other animals is why would they engage in such metabolically costly displays when it doesn't improve their fitness at all? And the answer that he gives is the answer that Darwin gave, which is sexual selection, not natural selection. But, you know, selection can occur for all kinds of reasons. There could be artificial selection, which is when we breed animals. Right. Which is actually how Darwin. That observation helped Darwin come to the idea of natural selection.

Oh, interesting.

And then there's sexual selection. Meaning. And the argument that I think his name is from makes is that it's the pleasure, the selection pressure is the pleasure of female birds, which, as a woman and as someone who studies affect. That's a great answer. I actually think there probably is natural. I think there is an aspect of natural selection to it which he maybe hasn't considered.

But you were saying the reason we brought up birds is the life we got now seems to be quite important.

Yeah. So you peek into the ocean, peek into the sky, there are miraculous creatures. Look at creatures who've gone extinct. And, you know, in science fiction stories, you couldn't dream up something as interesting. So my guess is that intelligent life evolves in many different ways. Even on this planet. There isn't one form of intelligence. There's not one brain that gives you intelligence. There are Lots of different brain structures that can give you intelligence. So my guess is that the menagerie might not look exactly the way that it looks now, but it would certainly be as interesting.

But if we look at the human brain versus the brains, or whatever you call them, the mechanisms of intelligence in our ancestors, even early ancestors that you write about, for example, in your new book, what's the difference between the fanciest brain we got, which is the human brain, and the ancestor brains that it came from?

Yeah, I think it depends on how far back you want to go.

You go all the way back, right, in your book. So what's the interesting comparison, would you say?

Well, first of all, I wouldn't say that the human brain is the fanciest brain we've got. I mean, an octopus brain is pretty different and pretty fancy. And they can do some pretty amazing things that we cannot do. We can't grow back limbs. We can't change color and texture. We can't comport ourselves and squeeze ourselves into a little crevice. I mean, these are things that we invent. These are like superhero abilities that we invent in stories. Right. We can't do any of those things. And so the human brain is certainly. We can certainly do some things that other animals can't do that seem pretty impressive to us. But I would say that there are a number of animal brains which seem pretty impressive to me, that can do interesting things and really impressive things that we can't do.

I mean, with your work on how emotions are made and so on, you kind of repaint the view of the brain as less glamorous, I suppose, than you would otherwise think or like, I guess you draw a thread that connects all brains together in terms of homeostasis and all that kind of stuff?

Yeah, I wouldn't say that the human brain is any less miraculous than anybody else would say. I just think that there are other brain structures which are also miraculous. And I also think that there are a number of things about the human brain which we share with other vertebrates, other animals with backbones, but that we share these miraculous things. But we can do some things in abundance. And we can also do some things with. With our brains together, working together, that other animals can't do, or at least we haven't discovered their ability to do it.

Yeah, this social thing, I mean, that's one of the things you write about. How do you make sense of the fact, like the book Sapiens and the fact that we're able to kind of connect, like network our Brains together. Like, you're right about. I'll try to stop saying that. Is that like some kind of feature that's built into there? Is that unique to our human brains? Like, how do you make sense of that?

What I would say is that our ability to coordinate with each other is not unique to humans. There are lots of animals who can do that, and we. But what we do with that coordination is unique because of some of the structural features in our brains. And it's not that other animals don't have those structural features. It's we have them in abundance. So, you know, the human brain is not larger than you would expect it to be for a primate of our size. If you took a chimpanzee and you grew it to the size of a human, that chimpanzee would have a brain that was the size of a human brain. So there's nothing special about our brain in terms of its size. There's nothing special about our brain in terms of the basic blueprint that builds our brain for. From an embryo is the basic blueprint that builds all mammalian brains and maybe even all vertebrate brains. It's just that because of its size and particularly because of the size of the cerebral cortex, which is a part that people mistakenly attribute to rationality.

Why mistakenly? Is that where all the clever stuff happens?

Well, no, it really isn't. And I will also say that lots of clever stuff happens in animals who don't have a cerebral cortex. But because of the size of the cerebral cortex and because of some of the features that are enhanced by that size, that gives us the capacity to do things like build civilizations and coordinate with each other, not just to manipulate the physical world, but to add to it in very profound ways. Like, you know, other animals can cooperate with each other and use tools. We draw a line in the sand and we make countries and we even then we create, you know, we create citizens and immigrants, but also ideas.

I mean, the countries are centered around the concept of, like, ideas.

It's, well, what do you think a citizen is and an immigrant. Those are ideas. Those are ideas that we impose on reality and make them real. And then they have very, very serious and real effects, physical effects on people.

What do you think about the idea that a bunch of people have written about Dawkins with memes, which is like ideas of breeding? Like, we're just like the canvas for ideas to breed in our brains. So this kind of network that you talk about of brains is just a little canvas for ideas to then compete against each other. And so on.

I think as a rhetorical tool, it's cool to think that way. So I think it was Michael Pollan. I don't remember if it was in the Botany of Desire, but it was in one of his early books on botany and gardening where he wrote about. He wrote about plants, sort of utilizing humans for their own evolutionary purposes, which is kind of interesting. You can think about a human gut, in a sense, as a propagation device for the seeds of tomatoes and what have you. So it's kind of cool. So I think. I think rhetorically, it's an interesting device, but ideas are, as far as I know, invented by humans, propagated by humans. So I don't think they're separate from human brains in any way, although it is interesting to think about it that way.

Well, of course, the ideas that are using your brain to communicate and write excellent books, and they basically picked you, Lisa, as an effective communicator and thereby are winning. So that's an interesting worldview to think that there's particular aspects of your brain that are conducive to certain sets of ideas, and maybe those ideas will win out.

Yeah. I think the way that I would say it really, though, is that there are many species of animals that influence each other's nervous systems, that regulate each other's nervous systems. And they mainly do it by physical means. They do it by chemicals, scent. They do it by, you know, so termites and ants and bees, for example, use chemical scents. Mammals, like rodents, use scent, and they also use hearing audition and that little bit of vision. Primates, you know, non human primates, add vision. Right. And I think everybody uses touch. Humans, as far as I know, are the only species that use ideas and words to regulate each other. Right. I can text something to someone halfway around the world. They don't have to hear my voice, they don't have to see my face. And I can have an effect on their nervous system. And ideas, the ideas that we communicate with words. I mean, words are, in a sense, a way for us to do mental telepathy with each other. Right. I mean, I'm not the first person to say, say that obviously, but how do I control your heart rate? How do I control your breathing? How do I control your actions? With words? It's because those words are communicating ideas.

So you also write, I think, let's go back to the brain. You write that Plato gave us the idea that the human brain has three brains in it, three forces, which is kind of a compelling notion. You disagree? First of all, what Are the three parts of the brain. And why do you disagree?

So Plato's description of the psyche, which for the moment we'll just assume is the same as a mind, There are some scholars who would say, you know, a soul, a psyche, a mind. Those aren't actually all the same thing in ancient Greece, but we'll just for now gloss over that. So Plato's idea was that. And it was a description of. Really about moral behavior and moral responsibility in humans. So the idea was that the human psyche can be described with a metaphor of two horses and a charioteer. So one horse for instincts like feeding and fighting and fleeing and reproduction. I'm trying to control my salty language, which apparently they print in England. Like, I actually tossed off a fairly.

F s. Yeah, F, F. Okay.

Yeah, yeah. I was like, you printed that. I couldn't believe you printed that without.

Like the stars or whatever.

No, no, no, it was full print. They also printed a B word and it was really. Yeah.

Anyways, we should learn something from England.

Indeed. Anyways. But inst. And then the other horse represents emotions, and then the charioteer represents rationality, which controls, you know, the two beasts. Right. And fast forward, you know, couple of centuries and in the middle of the 20th century, there was a very popular view of brain evolution which suggested that you have this reptilian core, like an inner lizard brain for instincts. And then wrapped around that evolved layer, on top of that evolved a limbic system in mammals. So the novelty was in a mammalian brain, which bestowed mammals with. Gave them emotions, the capacity for emotions. And then on top of that evolved a cerebral cortex, which in largely in primates, but very large in humans. And it's not that I personally disagree, it's that as far back as the 1960s, but really by the 1970s, it was shown pretty clearly with evidence from molecular genetics, so peering into cells in the brain to look at the molecular makeup of genes, that the brain did not evolve that way. And the irony is that the idea of the three layered brain with an inner lizard that hijacks your. Hijacks your behavior and causes you to do and say things that you would otherwise not, or maybe that you will regret later, that idea became very popular, was popularized by Carl Sagan in the Dragons of Eden, which won a Pulitzer Prize in 1977, when it was already known pretty much in evolutionary neuroscience, that the whole narrative was a myth.

So what? The narrative is on the way it evolved. But do you. I mean, again, it's that problem of it being a useful tool of conversation to Say like there's a lizard brain and there's a. Like if I get overly emotional on Twitter, that was the lizard brain and so on. But do you.

No, I don't think it's useful. I think it's a. I think that.

Is it useful, is it accurate?

I don't think it's accurate and therefore I don't think it's useful.

Got it.

So here's what I would say. I think that the way I think about philosophy and science is that they are useful tools for living. And in order to be useful tools for living, they have to help you make good decisions. The triune brain, as it's called, this three layer brain, the idea that your brain is like an already baked cake and the cortex, cerebral cortex, just layered on top, like icing. That idea is the foundation of the law in most Western countries. It's the foundation of economic theory. And it's a great narrative. It sort of fits our intuitions about how we work. But it also, in addition to being wrong, it lets people off the hook for nasty behavior. And it also suggests that emotions can't be a source of wisdom, which they often are. In fact, you would not want to be around someone who didn't have emotions. That's a psychopath. I mean, that's not someone you want to really have that person deciding your outcome. And I could sort of go on and on and on, but my point is that I don't think, I don't think it's a useful narrative.

In the end, what's the more accurate view of the brain that we should use when we're thinking about it?

I'll answer that in a second. But I'll say that even our notion of what an instinct is or what a reflex is, it's not quite right. Right. So if you look at evidence from ecology, for example, and you look at animals in their ecological context, what you can see is that even things which are reflexes are very context sensitive. The brains of those animals are executing so called instinctual actions in a very, very context sensitive way. And so even when a physician takes the. It's like the idea of your patellar reflex where they hit your patellar tendon on your knee and you kick. The force with which you kick and so on is influenced by all kinds of things. A reflex isn't like a robotic response. And so I think a better way is a way to think about how brains work is the way that matches our best understanding, our best scientific understanding, which I think is really cool because it's really counterintuitive. So how I came to this view, and I'm certainly not the only one who holds this view. I was reading work on neuroanatomy, and the view that I'm about to tell you was strongly suggested by that. And then I was reading work in signal processing by electrical engineering. And similarly, the work suggested that the research suggested that the brain worked this way. And I'll just say that I was reading across multiple literatures and they were. Who don't speak to each other, and they were all pointing in this direction. And so far, although some of the details are still up for grabs, the general gist, I think is I've not come across anything yet which really violates. And I'm looking. And so the idea is something like this. It's very counterintuitive. So the way to describe it is to say that your brain doesn't react to things in the world. To us, it feels like our eyes are windows on the world. We see things, we hear things, we react to them. In psychology, we call this stimulus response. So your face is. Your voice is a stimulus to me. I receive input and then I react to it. And I might react very automatically, you know, system one. But I also might execute some control where I maybe stop myself from saying something or doing something and in a more reflective way, execute a different action. Right. That's system two. The way the brain works, though, is it's predicting all the time. It's constantly talking to itself, constantly talking to your body, and it's constantly predicting what's going on in the body and what's going on in the world and making predictions. And the information from your body and from the world really confirm or correct those predictions.

So fundamentally, the thing that the brain does most of the time is just predict, like talking to itself and predicting stuff about the world. Not like this dumb thing that just senses and responds. Senses and response.

Yeah. So the way to think about it is like this. You know, your brain is trapped in a dark, silent box.

Yeah, that's very romantic of you.

Which is your skull. And the only information that it receives from your body and from the world. Right. Is through the senses, through the sense organs, your eyes, your ears. And you have sensory data that comes from your body that you're largely unaware of to your brain, which we call interoceptive, as opposed to exteroceptive, which is the world around you. And. But your brain is receiving sense data continuously, which are the effect of some set of causes. Your brain doesn't know the cause of these sense data, it's only receiving the effects of those causes, which are the data themselves. And so your brain has to solve what philosophers call an inverse inference problem. How do you know when you only receive the effects of something? How do you know what caused those effects? So when there's a flash of light or a change in air pressure or a tug somewhere in your body, how does your brain know what caused those events so that it knows what to do next to keep you alive and well? And the answer is that your brain has one other source of information available to it, which is your past experience. It can reconstitute in its wiring past experiences, and it can combine those past experiences in novel ways. And so we have lots of names for this in psychology. We call it memory, we call it perceptual inference, we call it simulation. It's also, we call it concepts or conceptual knowledge. We call it prediction. Basically, if we were to stop the world right now, stop time, Your brain is in a state and it's representing what it believes is going on in your body and in the world. And it's predicting what will happen next based on past experience. Right. Probabilistically, what's most likely to happen. And it begins to prepare your action, and it begins to prepare your experience based. So it's anticipating the sense data it's going to receive. And then when those data come in, they either confirm that prediction and your action executes because the plan's already been made, or there's some sense data that your brain didn't predict that's unexpected. And your brain takes it in, we say, encodes it. We have a fancy name for that. We call it learning. Your brain learns and it updates its storehouse of knowledge, which we call an internal model, so that you can predict better next time. And it turns out that predicting and correcting. Predicting and correcting is a much more metabolically efficient way to run a system than constantly reacting all the time. Because if you're constantly reacting, it means you have no. You can't anticipate in any way what's going to happen. And so the amount of uncertainty that you have to deal with is overwhelming to a nervous system.

Metabolically costly. I like it.

And so what is a reflex? A reflex is when your brain doesn't check against the sense data, that the potential cost to you is so great, maybe because you know your life is threatened, that your brain makes the prediction and executes the action without checking.

Yeah. So, but prediction's still at the core. That's a Beautiful vision of the brain, I wonder, from almost an AI perspective, but just computationally, is the brain just mostly a prediction machine? Then, like, is the perception just a nice little feature added on top, like the. Both the. The integration of new perceptual information. I wonder how big of an impressive system is that relative to just the big predictor, model, constructor?

Well, I think that we can, we can look to evolution for that for one answer, which is that when you go back, you know, 550 million years, give or take, you know, the world was populated by creatures really ruled by creatures without brains. And, you know, that's a biological statement, not a political statement.

You're calling dinosaurs dumb. You're talking about, like, oh, no, I'm.

Not talking about dinosaurs, honey. I'm talking way back, further back than that. Really. These, they're these little, little creatures called amphioxus, which is the modern. Or a lancet, that's the modern animal. But it's an animal that scientists believe is very similar to the common ancestor that we share with invertebrates, basically because of the tracing back the molecular genetics in cells. And that animal had no brain. It had some cells that would later turn into a brain, but in that animal, there's no brain. But that animal also had no head and it had no eyes and it had no ears and it had really, really no senses for the most part. It had very, very limited sense of touch. It had an eye spot for, not for seeing, but just for in training to circadian rhythm, to light and dark, and it had no hearing. It had a vestibular cell so that it could keep upright in the water. At the time, approximately, we're talking evolutionary scale here, so, you know, give or take some hundred million years or something. But at the time, you know, what are the vertebrate like when a backbone evolved and a brain evolved, a full brain, that was when a head evolved with sense, with sense organs. And when. That's when your viscera, like internal systems involved. So the answer, I would say, is that senses motor neuroscientists, people who study the control of motor behavior, believe that senses evolved in the service of motor action. So the idea is that, like, what triggered the, what triggered. What was. What was the big evolutionary change? What was the big pressure that made it useful to have eyes and ears and a visual system and an auditory system and a brain, basically. And, you know, and the answer that is, you know, commonly entertained right now is that it was predation that when at some point an animal evolved that deliberately ate another animal and this launched an arms race between predators and prey. And it became very useful to have senses, right? So these. These little amphiox, these little amphioxy, you know, don't really have. They. They don't have an. They're not aware of their environment very much, really. They. And so being able to look up ahead and ask yourself, should I eat that or will it eat me? Is a very useful thing. So the idea is that sense data is not there for consciousness. It didn't evolve for the purposes of consciousness. It didn't evolve for the purposes of experiencing anything. It evolved to be in the service of motor control. However, maybe it's useful. This is why scientists sometimes avoid questions about why things evolved. This is. Philosophers call this teleology. You might be able to say something about how things evolve, but not necessarily why. We don't really know the why. That's all speculation, but the why is.

Kind of nice here. The interesting thing is that was the first element of social interaction is am I going to eat you or are you going to eat me? And for that it's useful to be able to see each other, sense each other. That's kind of fascinating. There was a time when life didn't.

Eat each other or they did by accident. Right? So an amphioxus, for example, will. It kind of like gyrates in the water and then it plants itself in the sand like a blade of. Like a living blade of grass. And then it just filters whatever comes into its mouth. Right? So it is eating, but it's not actively hunting.

Hunting.

And when the concentration of food decreases, the amphioxus can sense this. And so it basically wriggles itself randomly to some other spot which probabilistically will have more food than wherever it is. So it's not really, you know, it's not guiding its actions on the basis of. It's not. We would say there's no real intentional action in the traditional sense.

Speaking of intentional action, and if the brain, if prediction is indeed a core component of the brain, let me ask you a question that scientists also hate is about free will. So how does. Do you think about free will? Much? How does that fit into this, into your view of the brain? Why does it feel like we make decisions in this world?

This is a hard. Scientists hate this because it's a hard question. We don't know the answer.

Have you taken aside? I think I have free will.

I think I have taken aside, but I don't put a lot of stock in my own intuitions or anybody's intuitions about the cause of things. Right. One thing we know about the brain for sure is that the brain creates experiences for us. My brain creates experiences for me. Your brain creates experiences for you in a way that lures you to believe that those experiences. Experiences actually reveals the way that it works. But it doesn't.

So you don't trust your own intuition about free will?

Not really, no. I mean, no. But I am also somewhat persuaded by. I think Dan Dennett wrote at one point, the philosopher Dan Dennett wrote at one point that I can't say it as eloquently as him, but it's. People obviously have free will. They are obviously making choices. So it's, you know, and so there is this observation that we're not robots and we can do some things like a little more sophisticated than an amphioxus. So here's what I would say. I would say that your predictions, your internal model that's running right now. Right. That your ability to understand the sounds that I'm making and attach them to ideas is based on the fact that you have years of experience knowing what these sounds mean in a particular statistical pattern. Right. I mean, that's how you can understand the words that are coming out of my mouth. Right. I think we did this once before too, didn't we? When we were.

I don't know, I would have to access my memory module, I think when.

I was in your Glenida class. Yeah, I think we did it just like that, actually. So bravo.

Wow. I have to go look back to the tape.

Yeah. Anyways, the idea though is that your brain is using past experience and it can use past experience in. So it's remembering, but you're not consciously remembering. It's basically re. Implementing prior experiences as a way of predicting what's going to happen next. And it can do something called conceptual combination, which is it can take bits and pieces of the past and combine it in new ways so you can experience and make sense of things that you've never encountered before because you've encountered something similar to them. And so a brain in a sense is not just. Doesn't just contain information, it is information gaining meaning. It can create new information by this generative process. So in a sense you could say, well, that maybe that's a source of free will. But I think really where free will comes from or the kind of free will that I think is worth having a conversation about involves cultivating experiences for yourself that change your internal model. When you were born and you were raised in a particular Context that your model, your brain, wired itself to your surroundings, to your physical surroundings, and also to your social surroundings. So you were handed an internal model, basically. But when you grow up, the more control you have over your. Where you are and what you do, you can cultivate new experiences for yourself. And those new experiences can change your internal model. And you can actually practice those experiences in a way that makes them automatic, meaning, it makes it easier for the brain, your brain, to make them again. And I think that that is something like what you would call free will. You aren't responsible for the model that you were handed. That someone you know, your caregivers, cultivated a model in your brain. You're not responsible for that model, but you are responsible for the one you have now. You can choose. You choose what you expose yourself to. You choose how you spend your time. Not everybody has choice over everything, but everybody has a little bit of choice. And so I think that is something that I think is arguably called free will.

Yeah, there's like the ripple effects of the billions of decisions you make early on in life are so great that even if it's not, even if it's like all deterministic, just the amount of possibilities that are created and then the focusing of those possibilities into a single trajectory that somewhere within that, that's free will. Even if it's all deterministic, that might as well be of just the number of choices that are possible. And the fact that you just make one trajectory to those set of choices seems to be like something like they'll be called free will. But it's still kind of sad to think, like, there doesn't seem to be a place where there's magic in there, where it is all just a computer.

Well, there's lots of magic, I would say, so far, because we don't really understand how all of this is exactly played out at a. I mean, scientists are working hard and disagree about some of the details under the hood of what I just described. But I think there's quite a bit of magic, actually. And also there's also stochastic firing of neurons, don't they? They're not purely digital in the sense that there's also analog communication between neurons, not just digital. So it's not just with firing of axons and some of that. There are other ways to communicate. And also there's noise in the system. And the noise is there for a really good reason. And that is the more variability there is, the more potential there is for your brain to be able to be information bearing so basically there are some animals that have clusters of cells. The only job is to inject noise into their neural patterns.

So maybe noise is the source of free will.

So you can think about stochasticity or noise as, As a source of free will, or you can think of conceptual combination as a source of free will. You can certainly think about cultivating. You can't reach back into your past and change your past. People try by psychotherapy and so on. But what you can do is change your present, which becomes your past.

Well, let's think about that sentence.

So one way to think about it is that you're continuously. This is a colleague of mine, a friend of mine said, so what you're saying is that people are continually cultivating their past. And I was like, that's very poetic. Yes, you are continually cultivating your past as a means of controlling your future.

So you think, yeah, I guess the construction of the mental model that you use for prediction ultimately contains within it your perception of the past, like the way you interpret the past, even just the entirety of your narrative about the past. So you're constantly rewriting the story of your past. Oh boy. Yeah, that's one poetic. And also just awe inspiring.

What about the other thing you talk about?

You've mentioned about sensory perception as a thing that like, is just. You have to infer about the sources of the thing that you have perceived through your senses. So let me ask another ridiculous question. Is anything real at all? Like, how do we know it's real? How do we make sense of the fact that just like you said, there's this brain sitting alone in the darkness trying to perceive the world. How do we know that the world is out there to be perceived?

Yeah. So I don't think that you should be asking questions like that without passing a joint.

Right. No, for sure. Yeah, I actually did before this. So I apologize.

Okay. No, well, that's okay. You apologize for not sharing. That's okay. So, I mean, here's what I would say. What I would say is that the reason why we can be pretty sure that there's a. There, there is that the, the structure of the information in the world, what we call statistical regularities in sights and sounds and so on, and the structure of the information that comes from your body, it's not random stuff. There's a structure to it. There's a spatial structure and a temporal structure. And that spatial and temporal structure wires your brain. So an infant brain is not a miniature adult brain. It's a brain that is waiting for Wiring instructions from the world. And it must receive those wiring instructions to develop in a typical way. So, for example, when a newborn is born, When a newborn is born, when a baby is born, the baby can't see very well because the visual system in that baby's brain is not complete. The, the retina of your eye, which actually is part of your brain, has to be stimulated with photons of light. If it's not, the baby won't develop normally to be able to see in a neurotypical way. Same thing is true for hearing. The same thing is true really for all your senses. So the point is that the physical world, the sense data from the physical world, wires your brain so that you have an internal model of that world so that your brain can predict well to keep you alive and well and allow you to thrive.

That's fascinating that the brain is waiting for a very specific kind of set of instructions from the world. Like not the specific, but a very specific kind of instruction.

Yes. So scientists call it expectable input. The brain needs some input in order to develop normally. And we are genetically, you know, as I say in the book, we have the kind of nature that requires nurture. We can't develop normally without sensory input from the world and from the body. And what's really interesting about humans and some other animals too, but really seriously, in humans is the input that we need is not just physical, it's also social. We, in order for an infant, a human infant, to develop normally, that infant needs eye contact, touch, it needs certain types of smells. It needs to be cuddled. It needs. Right. So without social input, that infant's brain will not wire itself in a neurotypical way. And again, I would say there are lots of cultural patterns of caring for an infant. It's not like the infant has to be cared for in one way. Whatever the social environment is for an infant, that will be reflected in that infant's internal model. So we have lots of different cultures, lots of different ways of rearing children. And that's an advantage for our species, Although we don't always experience it that way. That is an advantage for our species. But if you just feed and water a baby without all the extra social do dads, what you get is a profoundly impaired human.

Yeah. But nevertheless, you're kind of saying that the physical reality has. Has a consistent thing throughout that keeps feeding these set of sensory information that our brains are constructed for.

But yeah, the cool thing though is that if you change the consistency, if you change the statistical regularities, so prediction error Your brain can learn it. It's expensive for your brain to learn it, and it takes a while for the brain to get really automated with it. But you had a wonderful conversation with David Eagleman, who just published a book about this and gave lots and lots of really very, very cool examples, some of which I actually discussed in how emotions were made, but not, obviously, to the extent that he did in his book, which is. It's a fascinating book, but it speaks to the point that your internal model is always under construction, and therefore you always can modify your experience.

I wonder what the limits are, like if we put it on Mars or if we put it in virtual reality, or if we sit at home during a pandemic and we spend most of our day on Twitter and TikTok. Like, I wonder where the breaking point, like, the limitations of the brain's capacity to properly continue wiring itself.

Well, I think what I would say is that there are different ways to specify your question. Right. Like, one way to specify it would be the way that David phrases it, which is, can we. Can we create a new sense? Like, can we create a new sensory modality? How hard would that be? What are the limits in doing that? But another way to say it is what happens to a brain when you remove some of those statistical regularities? Right. Like, what happens to a brain. What happens to an adult brain when you remove some of the statistical patterns that were there and they're not there anymore?

Are you talking about in the environment or in the actual. Like, you remove eyesight, for example?

Well, either way, I mean, basically, one way to limit the inputs to your brain are to stay home and protect yourself.

I see.

Yeah. Another way is to put someone in solitary confinement. Another way is to stick them in a nursing home. Well, not all nursing homes, but, you know. But there are some. Right. Which really are. Where people are somewhat impoverished in the interactions and the sensory. The variety of sensory stimulation that they get. Another way is that you lose a sense. Right. But the point is, I think that the human brain really likes variety. To say it in a, you know, like a, you know, sort of Cartesian way, you know, variety is a good thing for a brain, and. There are risks that you take when you restrict what you expose yourself to.

Yeah. You know, there's always talk of diversity. The brain loves it to the fullest. Definition and degree of diversity.

Yeah. I mean, I would say the only thing, basically, human brains thrive on diversity. The only place where we seem to have difficulty with diversity is with each other. Right. But we. Who wants to Eat the same food every day. You never would. Who wants to wear the same clothes every day? I mean, my husband. If you ask him to close his eyes, he won't be able to tell you what he's wearing. He just. Right. He'll buy seven shirts of exactly the same style in different colors. But they are in different colors. Right. It's not like he's wearing.

How would you then explain my brain, which is terrified of choice and therefore I wear the same thing every time?

Well, you must be getting your diversity. Well, first of all, you are a fairly sharp dresser, so there is that. But. So you're getting some reinforcement for dressing the way to do. But. Well, your brain must get diversity in.

In other places.

In other places. But I think we, you know, the. So there, the two most expensive things your brain can do, metabolically speaking, is. Is move your body and learn something new. So novelty, that is diversity. Right. Comes at a cost, a metabolic cost, but it's a cost. It's an investment that gives returns. And in general, people vary in how much they like novelty, unexpected things. Some people really like it, some people really don't like it, and there's everybody in between. But in general, we don't eat the same thing every day. We don't usually do exactly the same thing in exactly the same order in exactly the same place every day. The only place we have difficulty with diversity is in each other. And then we have considerable problems there, I would say, as a species.

Let me ask, I don't know if you're familiar with Donald Hoffman's work about this. Questions of reality. What are your thoughts of the possibility that the very thing we've been talking about, of the brain wiring itself from birth to a particular set of inputs is just a little slice of reality? That there is something much bigger out there that we humans with our cognition, cognitive capabilities is just not even perceiving that the thing we're perceiving is just a crappy, like Windows 95 interface onto a much bigger, richer set of complex physics that we're not even in touch with.

Well, without getting too metaphysical about it, I think we know for sure it doesn't have to be the, you know, crappy version of anything. But we definitely have a limited. We have. We have a set of senses that are limited in very physical ways, and we're clearly not perceiving everything there is to perceive that's clear. I mean, it's just. It's not that hard. We can't. Without special. Why do we invent scientific tools it's so that we can overcome our senses and, and experience things that we couldn't otherwise, whether they are, you know, different parts of the visual spectrum, you know, the light spectrum, or things that are too microscopically small for us to see or too far away for us to see. So clearly we're only getting a slice and that slice. You know, the interesting or potentially sad thing about humans is that whatever we experience, we think there's a natural reason for experiencing it. And we think it's obvious and natural and it must be this way and that all the other stuff isn't important. And that's clearly not true. Many of the things that we think of as natural are anything but. They're certainly real, but we've created them. They certainly have very real impacts, but we've created those impacts. And we also know that there are many things outside of our awareness that have tremendous influence on what we experience and what we do. So there's no question that that's true. I mean, just, it's, it's. But the extent is how fantastic, really, the question is how fantastical is it?

Yeah, like what? You know, a lot of people ask me, I'm allowed to say this. I think I'm allowed to say this. I've eaten shrooms a couple times, but I haven't gone the full. I'm talking to a few researchers in psychedelics. It's an interesting scientifically place, like what is the portal you're entering when you take psychedelics? Or another way to ask is like dreams, what are.

So let me tell you what I think, which is based on nothing. Like this is based on my life, right? So I don't.

Your intuition.

It's based on my, it's based on my. I'm guessing now based on what I do know, I would say, but I think that, well, think about what happens. So you're running, your brain's running this internal model and it's all outside of your awareness for the. You see the, you feel the products, but you don't, you don't see sense. The, you have no awareness of the mechanics of it, right? It's going on all the time. And so one thing that's going on all the time that you're completely unaware of is that when your brain, your brain is basically asking itself, figuratively speaking, not literally, right? Like, how is the sense given? The last time I was in this sensory array with this stuff going on in my body and this chain of events which just occurred, what did I do next? What did I feel? Next. What did I see next? It doesn't come up with one answer. It comes up with a distribution of possible answers. And then there has to be some selection process. And so you have a network in your brain, a sub network in your brain, a population of neurons that helps to choose. I'm not talking about a homunculus in your brain or anything silly like that. This is not the soul. It's not the center of yourself or anything like that. But there is a set of neurons that weighs the probabilities and helps to select or narrow the field. Okay? And that network is working all the time. It's actually called the control network, the executive control network, or you can call it a frontoparietal, because the regions of the brain that make it up, or in the frontal lobe and the parietal lobe, there are also parts that belong to the subcortical parts of your brain. It doesn't really matter. The point is that there is this network, and it is working all the time. Whether or not you feel in control, whether or not you feel like you're expending effort, doesn't really matter. It's on all the time. Except when you sleep. When you sleep, it's a little bit relaxed. And so think about what's happening when you sleep. When you sleep, the external world recedes the sense data from. So basically your model becomes a little bit. The tethers from the world are loosened, and this network, which is involved in maybe weeding out unrealistic things, is a little bit quiet. So your dreams are really your internal model that's unconstrained by the immediate world. So you can do things that you can't do in real life in your dreams. Right. You can fly. Like I, for example, when I fly on my back in a dream, I'm much faster than when I fly on my front. Don't ask me why. I don't know.

When you're laying on your back in your dream?

No, when I'm in my dream and flying.