Ep35 "What sticks in your brain and what doesn’t? "

Published Nov 20, 2023, 11:00 AM

f you look at a brain, how can you immediately tell if it belongs to a piano player or a violinist? How can a dog learn how to walk on its rear legs? And what does this have to do with expertise, or the good news about the brains of digital natives, or how governments respond to change just like brains do? While we all like to talk about brain plasticity, the truth is that most of what happens in your life makes no meaningful change to your brain. So what’s the difference between the stuff that sticks and the stuff that doesn’t?

If you take a look at a brain, how can you tell immediately if it belongs to a piano player or a violinist? How can a dog learn to walk on its rear legs like a human? And what does this have to do with how you become an expert at something? Or what would happen if Venus and Serena Williams had a hypothetical brother, Fred who hated tennis? And how do governments respond to change just like brains do? And finally, why am I so optimistic about the brains of digital natives. Welcome to the inner Cosmos with me David Eagleman. I'm a neuroscientist and author at Stanford and in these episodes we sail deeply into our three pound universe to understand why and how our lives look.

The way they do.

Today's episode is about brain plasticity, which is the ability of the brain to change and adapt throughout your life. The word plasticity comes from the word plastic, which is a material that you can mold into any shape and then it holds onto that shape. And that is what is impressive about brains. You can expose them to any kind of situation or experience, and they hold on to the change. The vast forest of neurons in your head, These connections change their strength, and sometimes they unplug and they seek around and they replug in somewhere else. It's a living forest of eighty six billion neurons in your head, and this constant reconfiguration, this is how you learn and remember. The interesting part I want to address today is exactly when these changes in the brain happened, because it's not all the time. Most of the stuff that happens in your life makes no change at all to your brain. So what's the difference between the stuff that sticks and the stuff that doesn't. So let's start today in Hungary with an educational psychologist named Laslow Polgar. The thing about Laslow is that he loves chess, and he's written some well known chess books. But that's not the super interesting thing about him. The super interesting thing is that he got very interested in the theory of child rearing and he believed quote, geniuses are made, not born. So he started preparing himself for fatherhood even before he had a spouse, and he read the biographies of four hundred famous intellectuals like Socrates and Einstein, and he noted that what they all had in common is they started their intellectual pursuits at a young age and they studied intensively. So he concluded from this research the idea that he could, with the right effort, turn his future children into geniuses in a particular area which he and his wife could think about and pick. So they considered various domains, but they chose chess in part because the success of these children could be easily measurable with chess. So he and his wife had three daughters together, Susan, Sophia and Judete, and he made the move, which was unusual in Hungary at the time, to homeschool them, and he taught them German and English and Russian and high level math, but he primarily taught them chess from the moment that they were big enough to play with the pieces.

So what was the result.

By the time his eldest daughter, Susan turned fifteen years old, she was the top ranked chess player in the world. In nineteen teen eighty six, she qualified for the men's World Championship, which was a first time achievement for a female, and within five years she had earned the men's Grand Master title and then in the middle of Susan's astounding accomplishments, Her fourteen year old middle sister, Sophia, achieved fame for her sack of Rome, which was her stunning victory at a tournament in Italy, which ranked as one of the strongest performances ever by a fourteen year old. Sofia went on to become an international master and a woman grand master.

And then there was.

The youngest sister, Judite, who is widely considered the best female chess player on record. She achieved grand master status at the tender age of fifteen years and four months, and she remains the only woman on the World Chess Federation's Top one hundred list, and for a while she held a position in the top ten. So what accounts for their success, Well, their parents trained the girls every single day. They didn't just expose them to chess, they fed them on chess.

The girls received hugs.

And stern looks and approval and attention based on their chess performance, and as a result, their brains came to have a great deal of circuitry devoted to chess. Now, we've seen in other episodes how the brain is always rewriting itself in response to its inputs. But the fact is that not all information streaming into the pipelines is equally important. How brains adjust themselves has everything to do with what you're spending your time on, and that's why the Polgar sisters became biological chess machines. And it's the same thing with your brain. It'll reconfigure to whatever you're doing. So if you decide to make a career change to ornithology, the study of birds, more of your neural resources will become devoted towards learning the subtle differences between birds, like their wing shape, or their breast coloration, or their beak size, while maybe previously your neural representation of birds with something more crude, like is that a birder and airplane. So let's dive in to unpack how the brain makes changes and when it doesn't, which will tell us everything we need to know about how to make changes stick in your own brain. There's a great story about the violinist Yetsak Pearlman after one of his concerts and admiring concertgoer said to him, I would give my life to play like that, and Pearlman said, I did, Now what did he mean? Well, every morning, Pearlman drags himself out of bed at five point fifteen. He takes a shower and batakfast, and then digs into his four and a half hour morning practice. He then takes a lunch and an exercise session, and then launches his afternoon practice for another four and a half hours. He does this every day of the year, except for concert days, when he does only the morning practice session. And you know what, Brain circuitry comes to reflect what you do. So the cortex of Jasah Pearlman, or any highly trained musician changes through time into something different. And this isn't a metaphorical claim. You can see this with brain imaging, even with an untrained eye.

Let me tell you how.

If you look at the strip of brain right underneath where you wear headphones, that's an area called the motor cortex, and that's what directs your body how to move all of its six hundred exquisitely beautiful muscles. Now, if you zoom in on a region of the cortex involved in hand movement, you'll find something amazing, which is that musicians have a little puckered shape on their cortex where non musicians don't. So think of it like an extra wrinkle on the wrinkly outer bit of the brain, the cortex.

Why do the musicians have this.

It's because they use the muscles of their hands in an extraordinarily detailed way, much more so than non musicians, so their.

Brains devote more real estate to that task.

The thousands of hours of practice on the instrument physically molds their brains. And by the way, this is wildly specific. So imagine that you compare the brain of a violinist like Pearlman to the brain of a pianist like Vladimir Ashkenazi. What they both have in common is a deep dedication to their craft and countless hours of practice, and yet their brains look sufficiently different that you can easily see which brain belongs to whom. And that's because string players like Pearlman show that extra wrinkle mostly on one side and one hemisphere, because his left fingers are doing all the detailed work while the right hand mostly just runs the bow over the strings. In contrast, a pianist like Ashkenazi has that extra wrinkle in both hemispheres because both of his hands are performing meticulous patterns on the ivories. So simply by looking at the brain which used to be done in autopsy, but now you can do with a brain scan. You can tell what kind of musician you have in the scanner. You can discern this just by looking at the wrinkly bits on the motor cortex.

And we can read even more from the brain's patterns.

It represents not only that a hand is doing less or more, but sometimes what what in particular it's doing. So let's say you get a job at an assembly line and you're randomly assigned to one of two jobs. Either you put little marbles into jars, or your job is to screw the jar lid shut. Okay, so both jobs use your right hand, but the first requires fine use of your fingertips, while screwing the lid on makes use of your wrist and forearm. So if you're the jar filler, the real estate in your cortex that represents your fingers will increase, and this is at the expense of the real estate devoted to your wrists and forearms. If you are the lid turner, the opposite happens. You get more representation for your wrist and forearm and less for the detailed movement of your fingers. So in this way, what you do over and over becomes reflected in the structure of your brain, and these changes involve more than the motor cortex.

For example, if.

You spend months learning to read Braille, the bit of your cortex that represents touch from the index finger that will grow. If you take up juggling as an adult, the visual areas of your brain involved in that they increase. This is because brains reflect not simply the outside world, but more specifically your outside world, and this is what underlies getting good at something. Professional tennis players like Serena and Venus Williams they spend years training so that the right moves will come automatically in the heat of the game. Step, pivot, backhand, charge, fallback, aim, smash.

They train for.

Thousands of hours to burn the moves down into the unconscious circuitry of the brain. They craft their brains into overtrained machinery. He might have heard of the ten thousand hour rule, which suggests that you need to practice a skill for that many hours to become an expert, whether this is surfboarding or spelunking, or saxophone playing or whatever. Although we can't quantify the exact number of hours, the general idea is correct. You need massive amounts of repetition to dig the subway maps of the brain. There's a guy that I mentioned in an earlier episode. His name is Destin Sandlin, and he made a video where he tries to ride a bike that someone gave him with reversed steering, so when you push the handlebars to the left, the wheel turns to the right and vice versa. This is a super difficult thing to learn how to ride. So what he did is he spent every day working on this and trying it out, and he crashed and crashed, but eventually he got it. But the point I want to make here is that you know, he's an engineer, and it only took him a few seconds to cognitively understand how the bike worked, but that proved insufficient to ride it. He needed to invest weeks and weeks of practice.

Hence the ten thousand hour rule.

And this dynamic changing of the brain happens from intensive physical practice that you do, whether that's swimming or playing the harmonica, or swinging a tennis racket or using a rake or whatever. But these measurable brain changes, they don't just apply to the physical they apply to the mental also, so for example, when medical students study for their final exams over the course of three months, particular areas of their cortex changed so much that you can see this on brain scans with the naked eye. And you see something similar if you teach a person how to read backward through a mirror. And here's another example. Areas of the brain that are involved in spatial navigation are visibly different in London taxi drivers from the rest of the population. In each hemisphere, the taxi drivers have an enlarged region part of the hippocampus, which is an area involved in your internal maps of the outside world. So what you spend your time on changes your brain. You are more than what you eat. You become the information you digest. And this is how the Polgar sisters were able to blossom into world champion chess players. It's not because some gene codes for skill at chess. It's because they practiced over and over chiseling pathways in their brains to encode the powers and patterns of knights and rooks and bishops and ponds and kings and queens. So brains come to reflect their world.

But how does this happen? Exactly. Well, let's see the.

Answer by zooming in on a weird illusion that most of us have experienced, the phantom phone vibration. I recently saw a meme online. It was a picture of a human brain with the title that reads, Hey, I think your phone just buzzed in your pocket, and then on the bottom it reads, just kidding. Your phone isn't even in your pocket, you moron. Now, the phantom cell phone vibration is a menace that is unique to the twenty first century. It happens because of a momentary spasm or quivering or shaking, or a touch on your leg, And as long as the frequency and the duration of that feeling is vaguely similar to that made by your phone, your brain decides on your behalf, that's something interesting is happening with your phone. So thirty years ago, if you had noticed a leg twitch, you would have interpreted the feeling as a fly landing on you, or a movement of your clothing, or something accidentally brushing past you. So why does your interpretation differ from one generation to the next, Because your phone now serves as the optimal explanation for a whole range of twitchy feelings. So here's how to understand what's happening there in the brain. Think of a mountainous landscape. Now, picture a lake somewhere there that's encircled by mountains. For a rain drop to end up in that lake, it doesn't need to fall from the sky and land directly in the water. Instead, it only needs to hit the surrounding hillsides. It can land on the northern slope or the southern, or the eastern incline or the western and in any case it's gonna slide down into the lake. So the lake is what's known as an attractor state. Anything nearby will flow to that spot, and you have lots of such attractor states in your brain. So the feeling on your thigh doesn't have to be a buzzing phone.

It can be a slight shift.

Of your genes or a twitch of your thigh muscle, or an itch or graze past the sofa.

As long as the feeling is close, the signals.

Slide down the landscape to their attractor state, and then you reach to check for an important message. The landscape gets formed by what is important in your world. For another example, think about the way we interpret the sounds of language. It feels natural to you that you can understand the sounds of your native language, but foreign languages often have really close sounds that you can't hear the difference between.

Like ooh and eh. But why why can you not hear those?

As it turns out, there is something different about the brains of the people who speak those languages. But they weren't born that way, and neither were you. If you look at the space of all the possible sounds that humans can make with our mouths, it makes a relatively smooth continuum. You can kind of make any sound. But despite this, you learn from experience that specific sounds mean the same thing, whether they're uttered by your dad, or your babysitter or your teacher. Your brain figures out that a drawn out E and eclip to e both belong to the E category, or maybe your friend from Texas says a or whatever. But your experience teaches you that all the speakers mean the same sound, regardless of exactly how they're pronouncing it, and so your neural networks carve out a landscape in which all these sounds roll down the hillsides to the same interpretation. There's a lake in your brain that represents E, and all the inputs from all around end up in that lake and in neighboring valleys, you gather up sounds that are equivalent to A or I or O and so on. So with time, your landscape looks different from someone who's grown up in another language and who needs to distinguish the smooth continuum of sounds differently than you do. To think about an example of this, imagine a baby born in Japan call him Hyato, and a baby born in America call him William. From their brain's point of view, there is nothing different about them. But in Osaka, Hayato hears Japanese all around him.

From day one.

In Palo Alto, William hears the tones of English, where different sounds carry meaning. An example of what these two babies hear differently is the distinction between the.

R and L sounds.

So in English, these carry information like the word right versus light or raw versus law, But in Japanese there's no distinction between these two sounds. So as a result, William's internal landscape builds a mountain range between his interpretation of R and L, such that the difference between these two sounds is perceptually clear. In Hyato's brain, the landscape develops into a big valley, so that both R and L flow into a single lake because they have an identical interpretation. So as a result, Hyato can't hear the difference between those two sounds. Now, obviously, the children's brains were not born this way. Had William's pregnant mother moved to Osaka and Hyato's pregnant mother to Palo Alto, the boys would have had no trouble in becoming fluent speakers and listeners in their new language.

As opposed to a genetic issue.

Their neural landscapes are carved by what is relevant in their immediate environment. And what's fascinating is that you can see this carving happening even before the children learn how to speak. For example, make a continuous R sound and then switch it over to L. So L, now, how can you tell if an infant here's that change?

So it turns out the trick.

To the experiment is this, Infants will suck faster at the nipple when they detect a chain. When they hear a change from one sound to another sound, they go from suck suck suck to suck suck, suck, suck. So at the age of six months, both Hyato and William will both suck faster when the R changes to L. But by twelve months, Hyato stops detecting the change. R and L sound the same to him. Both sounds are sliding down into the same valley. Hyato's brain has lost the ability to distinguish these sounds, while William's brain, having passively listened to his parents speak tens of thousands of English words, has learned that there's information carried in the difference between these two sounds. Hyato's brain, meanwhile, has picked up on other sound distinctions, which to William would be indistinguishable. So your auditory system begins universally and then wires itself to maximize the distinction unique to your language, depending on where on the planet you happened to stick your head out of the womb. And similarly, the buzzing phone isn't something you were born to detect. Instead, it's high relevance carves your neural landscape such that you have a broad catch all for neighboring sensations, all of which you will interpret as a buzzing cell phone in your pocket. Like kyata. With the R and the L, you combine the twitches and vibrations and quiverings into a single interpretation of what just happened. Now, from what we've seen so far, we might think that repetition is the key to molding the circuitry in your brain. But in fact, there's a deeper principle at work. So now we're going to talk about relevance. There's an old joke that goes, how many psychiatrists does it take to change a light bulb? And the answer is only one, But the light bulb has to want to change. Now, if you listen to episode two, you may remember a dog that I talked about named Faith. She is very memorable because Faith was born with out front legs and she figured out how to walk by pedaly on her hind legs, sort of like a human.

Now.

When I told her story in episode two, I said it as though her brain had just figured out her unusual body plan. But we can now dig a little deeper for a hidden bone. Was there something special about Faith? Could any dog have pulled us off? And if they could have, why don't all dogs walk by?

Peeda Ly?

Faith's rewritten maps were all about relevance to her life. Her brain was shaped by her goals. Faith needed to get to her food. That required a solution. It wasn't going to be the same one that was used by her four legged siblings. She had to derive a novel solution, so her brain tried out various strategies until it found when that worked balancing on her two back legs and lurching forward step after step. This allowed her to get what she needed, and after a while, she became good at this method of locomotion. In the absence of finding an answer to her challenge, she would have starved and died. Her drive for survival allowed the flexible circuitry in her brain to try out a bunch of hypotheses and solve the problem getting her to food and shelter and loved ones.

So goals matter.

A brain's goals play a critical role in how and when it changes. For the Polgar sisters, achieving their expertise depended on a desire to achieve their expertise. Same with Yitzak Pearlman or Vladimir Ashkenazi. Imagine for a moment that Serena and Venus Williams had a brother, Fred, and that their parents had put a tennis racket in Fred's hands and forced him to go through all the years of practicing that his sisters went through. But imagine that he found tennis repulsive. He never got good feedback from his classmates about his performances, and he didn't win any contests, and his elders didn't lavish him with praise. The result of all that practice would be nothing. Fred's brain would show little reorganization. Although his body was going through the same motions as his sisters, the motions would be misaligned with his internal incentives. So this is easily shown in the laboratory. So imagine an experiment in which someone is tapping out Morris code on your foot while someone else totally separately is playing a sequence of sounds.

Now, if the.

Task is that you can win cash for decoding the message on your foot, then the brain regions involved in touch to that part of your body will develop higher resolution. The regions involved in your hearing won't change, even though that brain area is also receiving stimulation. Now imagine the reverse game. Now, answering questions about subtle differences between the sounds earns the cash while attending to your foot doesn't yield anything. Now we'll see changes in the auditory cortex where you're doing the hearing, but the touch in your somatosensory cortex won't change. The inputs from the world are exactly the same in both cases. But what changes in your brain depends on what is rewarded. And this is why Fred Williams gets no better on the tennis court. He derives no reward from it. In his brain, just like in yours, the maps of the neural territory reflect to the strategies that have won positive feedback. Now this kind of understanding about motivation and relevance leading to change in the brain. This understanding opens new pathways for recovery from brain damage. So imagine that a friend of yours suffers a stroke. That damage is part of her motor cortex, and as a result, one of her arms becomes mostly paralyzed. So after trying many times to use her weakened arm, she gets frustrated and just uses her good arm to accomplish all the necessary tasks in her daily routine. This is a typical scenario, and her weak arm becomes only weaker because she's never choosing to use it. Now, the lessons of brain plasticity that we've been talking about offer a solution that is counterintuitive. The solution is known as constraint therapy. You strap down her good arm so that she can't use it, and that forces her to employ the weak arm. Now, this simple method retrains the damaged cortex by forcing use of the bad arm and cleverly taking advantage of these neural mechanisms underlying desire and reward. Because she has inherent motivation to get the sandwich to her mouth, or to turn the key in her front door, or to raise the cell phone to her ear, and to perform all the other actions that underlie a dignified, self sufficient life. So while constraint therapy starts off as frustrating, the approach proves to be the best medicine because it forces the brain to try new strategies, and the reward locks in the methods that work. It seems paradoxical that the solution of the problem is to make things worse, but that's precisely what solves. So let's return to faith the dog. Are all dogs able to walk on their back legs? Sure, but most dogs will never have the reason or motivation to attempt it, and certainly no reason to master it. And that's why Faith became famous, not because she's the only dog in the world who could do it, but because she's the only one who made it happen. You may know that some blind people learn how to navigate using echolocation. They make sounds with their mouth and they listen for the echo to give them information. But it turns out that people with perfectly normal vision can learn how to echo locate. Also, the issue is just that most cited people simply are insufficiently motivated to pour the hours and hours into redefining their neural territory. Now, reward is a powerful way to rewire the brain, but happily, your brain doesn't require cookies or cash. More generally, change is tied to anything that's relevant to your goals. If you're in the far North and you need to learn about ice fishing and different types of snow, that's what your brain will come to encode. If instead your equatorial and you need to learn which snakes to avoid and which mushrooms to eat, your brain will devote its resources accordingly. Using relevance as it's north star, the brain flexibly picks up on important details. It's billions of neurons serve as a colossal canvas for painting the world that we happen to find ourselves in, and with it we develop expertise and whatever has relevance to us, whether that's basketball or theater or badminton or Greek classics or cliff jumping or video gaming or line dancing or wine making. Whenever a task is roughly aligned with our larger goals, our brain.

Circuitry comes to reflect that.

Now, with how brains rewire based on what's relevant, I realized really interesting analogy some years ago. Governments do the same thing. They continually self design based on what's happening in the nation. So just look at what happened. In response to the attacks of September eleventh, two thousand and one, the United States government altered its structure. It established the Department of Homeland Security, which absorbed and restructured twenty two existing agencies, And the same thing happened with the simmering Cold War. This initiated a large shift in nineteen forty seven, which spawned the Central Intelligence Agency, and in a thousand small ways, a government subtly mirrors the current aims of a nation and the events of its outside world. So you have budgets swelling and shrinking to echo priorities when external threats loom. The military pocketbook expands when peacetime follows. Social initiatives gain. Just like brains, nations respond to changing situations by shifting their resources and redrawing their organizational charts to meet the challenges that they face. So how does the brain know when something important has happened and that it should change its wire accordingly. Well, one strategy is to turn on plasticity when events in the world are correlated. So the idea here is to just encode only those things that co occur, Like you see a cow and you hear a move, and in this way related events become bound together in the brain tissue. Now, you generally don't want to implement these changes too quickly, because sometimes there are associations that are spurious.

You might see a cow.

But you hear the bark of an unrelated dog, and you wouldn't want your brain to permanently store every accidental cooccurrence.

So the brain solution is to change slowly, just a little at a time.

And in that way it comes to encode only those things that commonly coincide real matches distinguish themselves from noise by occurring together over and over and over. But despite the wisdom of slow and steady change extracting averages like this, that's not the whole story. Because just think about one trial learning in which you, let's say, touch a hot stove and you learn not to do that again. So you've got emergency mechanisms that exist to make sure that life threatening or limb threatening events are permanently retained. The story of one trial learning goes deeper than that. Think about when you were young and your aunt taught you a new word. She says, this is called a pomegranate. Now, you didn't need to learn that in an emergency situation, and you didn't need your aunt to say this association one hundred times. She calmly told you once, and you got it in one trial. Why It's because it was salient to you. You loved your aunt, and you derived social benefit from knowing a new word and being able to ask for the delicious fruit. This is one trial learning not because of threat, but instead because of relevance.

Inside the brain.

This relevance is expressed through these widely reaching systems that release chemicals called neuromodulators. By releasing these with high specificity, these chemicals allow changes to occur only at specific places and times instead of all over at every moment. An especially important chemical messenger here is called acetylcholine.

Neurons that release the.

Seedlcholine are driven by both reward and punishment, and they're active whenever you're learning a new task and need to make changes, but they're not active once the task is well established.

So here's what you need to know.

The presence of acetylcholine at a particular brain area tells it to change, It doesn't tell it how to change. In other words, when the neurons that spit out acetal coline are active, they simply increase plasticity in the target areas. When they are not active, there's little or no plasticity. So here's an example. Imagine I play for you a particular note on the piano, say D flat. The note triggers activity in your auditory cortex, but it doesn't change anything about how much territory is devoted to D flat.

Why not?

It's because the note doesn't mean anything in particular to you. Now, let's say every time I play the note, I give you a warm chocolate chip cookie. Now the note accrues a meaning, and the brain territory devoted to D flat expands. Your brain assigns more real estate to that frequency because the presence of reward suggests it's important. Now, let's say I don't have any cookies available, so instead of handing you the treat, I play the D flat. At the same moment that I stimulate neurons in your head that release a setal colin. The cortical representation for that tone expands, just like it did with the cookies. Your brain allocates more terrain to that frequency because the presence of the acetyl coline indicates that it must be important. So a setyl colin broadcasts widely throughout the brain, and as a result, it can trigger changes with whatever kind of relevant stimulus, whether that's a musical note or a texture or something verbal. It's a universal mechanism for saying this is important. Get better at detecting this. It marks relevance by increasing territory, and changes in neural territory map on to your performance. So as an example of that, imagine that you have to learn how to play some crazy new musical instrument. So a couple of weeks of practice improves your speed and your skill, and you have a correspondingly large increase in the brain areas that are involved. But if you are a seedyl colin release is blocked with a drug, those brain areas don't grow and your skill never improves. So the basis of the behavioral improvement is not simply the repeated performance of the task. It requires these neuromodulatory systems to encode relevance. Without the acetyl coline, the ten thousand hours is wasted time. So with the hypothetical Fred Williams, who hates tennis, why didn't his brain change even after the same number of hours of practice as his sisters. It's because these neuromodulatory systems were not engaged in his head as he drilled backhands over and over. He's like you practicing the instrument with no acetal colin.

As a quick side note, these acetal.

Colin neurons reach out widely across the brain. So when these start chattering away, why doesn't that turn on plasticity everywhere they reach, causing widespread neural changes. The answer is that acetyl coline's release and its effects are modulated.

By other neural modulators.

So while acetal colon turns on plasticity, other neurotransmitters like dopamine are involved in the direction of change, encoding whether something was punishing or rewarding. Researchers all over the planet are still working to decipher this very complex choreography of the neurotransmitter systems. But what we know is that collectively, these chemical messengers allow reconfiguration in some areas while keeping the rest locked down.

So let's go back to the London taxi drivers.

They're famous for having to memorize the entire map of the streets of London, and they train for months and months on this task, and I mentioned before there are physical changes in the structure of their brain as a result. These cavies are able to pull off this staggering feet because the map is relevant to them. This is their desired employment, which is going to pay for their home mortgage, or their child's tuition, or their upcoming marriage. But interestingly, since the study of the cabbys was first published in the year two thousand, the need for this kind of memorization has essentially gone away. Now it's just as easy to have Google memorize all the streets of London, and more generally, all the streets interlacing the planet. So the kind of brain changes that we saw at the turn of the century, we probably.

Won't be seeing in them anymore.

What's interesting is that AI algorithms don't care about relevance. They memorize whatever we ask them to, which is a super useful feature of AI, but it's also the reason that AI is not exactly human like, because AI just doesn't care which problems are interesting or germane. It just memorizes whatever we feed it, So whether that's distinguishing a horse from a zebra in a billion photographs or tracking flight data from every airport on the planet, it has no sense of importance except in a statistical sense. Contemporary AI could never by itself decide that it finds irresistible a particular sculpture by Michaelangelo, or that it hates the taste of bitter tea, or that it's aroused by signals of fertility. AI can dispatch ten thousand hours of intense practice in ten thousand nanoseconds, but it doesn't favor any zeros and ones over others. As a result, AI can accomplish super impressive feats, but not yet the feat of being anything like a human who cares about some things more than others. Now, how does the modifiability of the brain and its relationship to relevance bear on the way that we teach our young The traditional classroom consists of a teacher that's droning on, possibly reading from bulleted slides. This is totally suboptimal for brain changes because the students aren't engaged, and without engagement there's little or no plasticity. The information doesn't stick. Now, we are not the first generation to make this observation. The ancient Greeks had noted this. They didn't have the tools of modern neuroscience, but they had a sharp eye, and they defined seven different levels of learning, and the highest level where the best learning occurs, is achieved when a student is invested and curious and interested. Through a modern lens, we would say that a particular formula of neurotransmitters is required for neural changes to take place, and that formula correlates with investment and curiosity and interest this trick of inspiring curiosity. This is woven into several traditional forms of learning. So, for example, Jewish religious scholars will study the Talmud by sitting in pairs and posing interesting questions to each other, like why does the author use this particular word instead of a different word? Or why do these two authorities differ in their account? Everything gets cast as a question, which forces their learning partner to engage instead of memorize. And although this is an ancient study structure, I recently stumbled on a website that poses talmudic questions about microbial biology. Questions like, given that spores are so effective in ensuring survival of bacteria, why don't all species make them? Or do we know for sure that there are only three domains of life bacteria, Archaea and Eucaria, Or how come peptides made enzematically don't seem to get strung together to make a respectably sized protein.

This site has hundreds.

Of questions like this, which coaxes an active engagement in its readers instead of simply telling them answers and more generally, this is why joining a study group always helps. It doesn't matter if you're studying calculus or history or whatever. A study group activates the brain's social mechanisms to motivate engagement.

Now.

I saw a wonderful interview in the nineteen eighties where the author Isaac Asimov gave an interview with the television journalist Bill Moyers, and Asimov saw the limits of the traditional education system with really clear eyes. And here's what he said. He said, quote, today, what people call learning is forced on you. Everyone is forced to learn the same thing on the same day, at the same speed in class. But everyone is different. For some, class goes to fast, for some, it goes too slow, for some in the wrong direction. Asimov had a vision for individualized education, although he couldn't see the details. He was squinting into the future, and he anticipated the Internet. He said, quote, give everyone a chance to follow up their own bent from the start, to find out about whatever they're interested in by looking it up in their own homes, at their own speed, in their own time, and everyone will enjoy learning.

End quote.

It's through this lens of triggering interest that a lot of philanthropists like Bill and Melinda Gates are aiming to build adaptive learning. The idea is you leverage software that quickly determines the state of knowledge of each student, and then instructs each student on exactly what he or she needs to know next. It's like having a one to one student teacher ratio. This approach keeps each student the right pace, meeting him where he is right now, with the material that will captivate and This past May, Saul Kahn gave a great talk at TED where he talked about using AI to personalize learning. With AI, the students can learn at their own pace and in their own way, and he's increasingly making con Academy as a way to show how AI can create totally personalized learning experiences based on that student's individual strengths and weaknesses, like asm Off and Gates and con and many others. I am a cyber optimist on the topic of education. I always find myself on Wikipedia, where I'm just following my interest. I click on one link and I'm reading, and then I think, WHOA, what's that? And I follow that link and after about twelve links, I'm down some mole hole and I think, Wow, how did I get from that topic over here? I think that drilling down through these blind mole holes of wikiped without any pre specified plan may turn out to be a near optimal way to learn and more generally, what the Internet allows is for students and all of us to answer questions as soon.

As they pop into our heads.

We get the answer in the context of our curiosity. And this is the powerful difference between the way that many of us grew up with just in case information, like just in case you need to know it the Battle of Hastings occurred in ten sixty six, and what's happening now, which is just in time information, which is getting the information the moment that you seek the answer. Generally speaking, it's only in the latter case, when you're doing just in time information that you find the right brew of neuromodulators present.

The Chinese have.

An expression an hour with a wise person is worth more than one thousand busos, and this insight is the ancient equivalent of what the Internet offers.

When the learner can actively direct her.

Own learning by asking the wise person precisely the question that she wants to answer, the molecules of relevance and reward are present.

They allow the brain to reconfigure.

When you toss facts and an unengaged student, it's like throwing pebbles to dent a stone wall. It's like trying to get Fred Williams to absorb tennis. So in this light we have great opportunities because of the gamification of education. You have this adaptive software which keeps students working at their point of struggle, where finding the right answer is frustrating but achievable. If the student can't get the answer, the questions stay at the same level. When he gets the right answer, the questions get harder. So there's still a role for the teacher here to teach foundational concepts and to guide the path of learning. But fundamentally, given how brains adapt and rewrite their wiring, a neuroscience compatible classroom is one in which the students drill into the vast sphere of human knowledge by following the paths of their individual passions. So the future of education looks very favorable. But one question remains, and I just want to address this here because I get asked this so often. Given that the brain becomes wired from experience, what are the neural consequences of growing up on screens? Are the brains of digital natives different from the brains of the generations before them. Now, it comes as a surprise to many people that there aren't more studies on this than neuroscience. Wouldn't our society want to understand the differences between the digital and analog raised brain.

Yes, we would. But the reason there are no.

Good studies on this is because it's inordinately difficult to perform meaningful science on this. Why because there's no good control group against which to compare a digital native's brain. You can't easily find another group of eighteen year olds who haven't grown up with the Internet. You might find some Amish teenagers in Pennsylvania, but there are dozens of other differences with that group, such as religious and cultural and educational beliefs. Where else could you find young people of the same age who grew up without access to the Internet. You might be able to turn up some impoverished children in rural China, or in a village in Central America or in the Kalahari Desert, but there are going to be other major differences with those children and the digital natives whom you intended to understand, including wealth and education and diet, So it's not a useful control group. Okay, So maybe you could compare millennials against the generation that came before them, like their parents, who didn't grow up online, but who instead played street stickball and stuffed twinkies in their mouths as they watched The Brady Bunch. But this is also problematic because between two generations there are innumerable differences of politics and nutrition and pollution and cultural innovation, such that if you find differences in the brain, you have no idea what to.

Attribute it to.

So this is an intractable problem to pull off a well controlled experiment about the effect of growing up with the Internet. Nonetheless, I can tell you the root of my optimism about this. Never before have we had the entirety of humankind's knowledge in a rectangle in our pockets, with constant and immediate access. Some of you will remember taking trips down to the library and you look around for the Encyclopedia Britannica, and you find the letter and you hope there's an article there about what you're looking for, and if it's there, you hope that it's not too many decades old and that the information is still relevant. And if you can find an article there, then you have to go to the card catalog and you flip through it and hope that there's a book somewhere in the library that addresses what you want to know in a surprisingly brief period. This is all changed, and as a result, we've all seen the transition of dinner time debates, where the winner has transitioned from being the loudest or most pervasive to the person who can whip out the phone the fastest and google the fact in question. Discussions move really rapidly now, they leap from one solved question to the next, and even when we're by ourselves, there's just no.

End to the learning that goes on. When we look up.

The Wikipedia page, which cascades is down the next link in the next such that six jumps later, we're learning facts that we didn't even know we didn't know.

And the great advantage of this comes from a simple fact.

All new ideas in your brain come from a mashup of previously learned inputs, and today we get more new inputs than ever before. And so our children are living in a time unparalleled in richness. Our knowledge sphere has exploded in diameter, and as it grows, it offers more doors for entry. So young minds have the opportunity to cross link facts from completely different domains to generate ideas that previous eras couldn't even have imagined, and this partially explains the exponential increase in human scholarship. We have faster communication and more mashups than ever before. So it's not clear what all the social and political consequences of the Internet will be, but from a neuroscience perspective, it unlocks a much richer level of education. So in earlier podcasts we looked at brain changes resulting from changes to the body plan in terms of either new sensors or new limbs, and in this episode we turn to changes that result from practiced motor acts or rewarding sensory inputs. But the larger principle that ties all these scenarios together is relevance. Your brain adjusts itself according to what you spend your time on as long as those tasks have alignment with rewards or your goals. For a person who goes blind, expanding the other senses takes on a heightened relevance, and this is the deeper origin behind the changes that allow her visual cortex to get taken over. If a person passes her fingers repeatedly over the bumps of braille but has no motivation to learn it then no rewiring takes place because the right.

Neuromodulators just aren't present.

And in the same way, if you add a new telelimb to your body and it has relevance to you, your body will learn how to use that, just like Faith the dog mastered a unique body plan and learned how to walk on her back legs because it mattered to her. So the lesson I want to leave you today with is when you need to learn something, find some aspect of that that matters to you. My students ask me this all the time about advice on getting through their final exams, and I tell them it's all about relevance. Figure out what is the aspect that matters to you. You're facing this dumb exam that you might not care about, but you do care about getting into graduate school and this is one important wrong on the ladder to get there. Or you want to impress that girl or boy over there, and so you need to study so you can have this stuff on the tip of your tongue. Or you appreciate the sacrifice that your parents made in getting you here and you want to make them proud and that would be meaningful to you, or whatever the personal details don't matter, but the key is to remind yourself of the relevance so you can plug into that, so you can get the right neurotransmitters present, so they can make the impression, so that they can make the information stick, so that you're not like Fred Williams who swings at the tennis ball but whose brain doesn't change, but instead you're taking in the information and you're making these changes in your forests of neurons so that you can recall it later.

That's what brain plasticity is all about.

Go to Eagleman dot com slash podcast for more information and to find further reading on all of this. Send me an email at podcast at eagleman dot com with questions or discussion, and I'm making sporadic episodes in which I address those until next time. I'm David Eagleman, and this is Inner Cosmos.

Inner Cosmos with David Eagleman

Neuroscientist and author David Eagleman discusses how our brain interprets the world and what that  
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