WEBVTT - Ep35 "What sticks in your brain and what doesn’t? " 0:00:05.200 --> 0:00:07.320 If you take a look at a brain, how can 0:00:07.360 --> 0:00:11.080 you tell immediately if it belongs to a piano player 0:00:11.480 --> 0:00:15.200 or a violinist? How can a dog learn to walk 0:00:15.280 --> 0:00:18.320 on its rear legs like a human? And what does 0:00:18.360 --> 0:00:21.840 this have to do with how you become an expert 0:00:21.920 --> 0:00:25.800 at something? Or what would happen if Venus and Serena 0:00:25.840 --> 0:00:30.400 Williams had a hypothetical brother, Fred who hated tennis? And 0:00:30.480 --> 0:00:35.120 how do governments respond to change just like brains do? 0:00:35.880 --> 0:00:39.639 And finally, why am I so optimistic about the brains 0:00:39.840 --> 0:00:46.519 of digital natives. Welcome to the inner Cosmos with me 0:00:46.680 --> 0:00:50.599 David Eagleman. I'm a neuroscientist and author at Stanford and 0:00:50.720 --> 0:00:54.280 in these episodes we sail deeply into our three pound 0:00:54.360 --> 0:00:58.480 universe to understand why and how our lives look. 0:00:58.360 --> 0:00:59.120 The way they do. 0:01:08.200 --> 0:01:12.520 Today's episode is about brain plasticity, which is the ability 0:01:12.560 --> 0:01:16.240 of the brain to change and adapt throughout your life. 0:01:16.760 --> 0:01:20.840 The word plasticity comes from the word plastic, which is 0:01:20.840 --> 0:01:24.000 a material that you can mold into any shape and 0:01:24.040 --> 0:01:26.679 then it holds onto that shape. And that is what 0:01:26.760 --> 0:01:30.320 is impressive about brains. You can expose them to any 0:01:30.360 --> 0:01:34.360 kind of situation or experience, and they hold on to 0:01:34.560 --> 0:01:38.480 the change. The vast forest of neurons in your head, 0:01:38.840 --> 0:01:43.640 These connections change their strength, and sometimes they unplug and 0:01:43.680 --> 0:01:46.960 they seek around and they replug in somewhere else. It's 0:01:47.000 --> 0:01:51.360 a living forest of eighty six billion neurons in your head, 0:01:51.680 --> 0:01:57.840 and this constant reconfiguration, this is how you learn and remember. 0:01:58.960 --> 0:02:01.680 The interesting part I want to address today is exactly 0:02:02.240 --> 0:02:04.960 when these changes in the brain happened, because it's not 0:02:05.560 --> 0:02:08.280 all the time. Most of the stuff that happens in 0:02:08.280 --> 0:02:11.360 your life makes no change at all to your brain. 0:02:12.040 --> 0:02:14.920 So what's the difference between the stuff that sticks and 0:02:14.960 --> 0:02:19.280 the stuff that doesn't. So let's start today in Hungary 0:02:19.720 --> 0:02:23.959 with an educational psychologist named Laslow Polgar. The thing about 0:02:24.040 --> 0:02:27.920 Laslow is that he loves chess, and he's written some 0:02:27.960 --> 0:02:31.200 well known chess books. But that's not the super interesting 0:02:31.240 --> 0:02:33.640 thing about him. The super interesting thing is that he 0:02:33.720 --> 0:02:38.080 got very interested in the theory of child rearing and 0:02:38.160 --> 0:02:43.440 he believed quote, geniuses are made, not born. So he 0:02:43.520 --> 0:02:47.320 started preparing himself for fatherhood even before he had a spouse, 0:02:47.720 --> 0:02:52.160 and he read the biographies of four hundred famous intellectuals 0:02:52.160 --> 0:02:55.799 like Socrates and Einstein, and he noted that what they 0:02:55.880 --> 0:03:00.000 all had in common is they started their intellectual pursuits 0:03:00.120 --> 0:03:04.160 at a young age and they studied intensively. So he 0:03:04.240 --> 0:03:08.360 concluded from this research the idea that he could, with 0:03:08.480 --> 0:03:13.240 the right effort, turn his future children into geniuses in 0:03:13.280 --> 0:03:16.280 a particular area which he and his wife could think 0:03:16.280 --> 0:03:19.960 about and pick. So they considered various domains, but they 0:03:20.080 --> 0:03:25.200 chose chess in part because the success of these children 0:03:25.240 --> 0:03:28.480 could be easily measurable with chess. So he and his 0:03:28.520 --> 0:03:33.440 wife had three daughters together, Susan, Sophia and Judete, and 0:03:33.480 --> 0:03:36.280 he made the move, which was unusual in Hungary at 0:03:36.280 --> 0:03:39.640 the time, to homeschool them, and he taught them German 0:03:39.680 --> 0:03:42.280 and English and Russian and high level math, but he 0:03:42.360 --> 0:03:46.520 primarily taught them chess from the moment that they were 0:03:46.520 --> 0:03:48.119 big enough to play with the pieces. 0:03:49.080 --> 0:03:50.720 So what was the result. 0:03:51.400 --> 0:03:55.280 By the time his eldest daughter, Susan turned fifteen years old, 0:03:55.920 --> 0:03:58.960 she was the top ranked chess player in the world. 0:03:59.520 --> 0:04:01.960 In nineteen teen eighty six, she qualified for the men's 0:04:01.960 --> 0:04:05.600 World Championship, which was a first time achievement for a female, 0:04:05.920 --> 0:04:08.720 and within five years she had earned the men's Grand 0:04:08.840 --> 0:04:14.720 Master title and then in the middle of Susan's astounding accomplishments, 0:04:14.760 --> 0:04:18.960 Her fourteen year old middle sister, Sophia, achieved fame for 0:04:19.120 --> 0:04:23.000 her sack of Rome, which was her stunning victory at 0:04:23.040 --> 0:04:25.800 a tournament in Italy, which ranked as one of the 0:04:25.920 --> 0:04:30.000 strongest performances ever by a fourteen year old. Sofia went 0:04:30.040 --> 0:04:34.480 on to become an international master and a woman grand master. 0:04:35.480 --> 0:04:36.200 And then there was. 0:04:36.160 --> 0:04:40.320 The youngest sister, Judite, who is widely considered the best 0:04:40.320 --> 0:04:45.160 female chess player on record. She achieved grand master status 0:04:45.640 --> 0:04:48.240 at the tender age of fifteen years and four months, 0:04:48.640 --> 0:04:51.160 and she remains the only woman on the World Chess 0:04:51.200 --> 0:04:54.200 Federation's Top one hundred list, and for a while she 0:04:54.680 --> 0:04:58.960 held a position in the top ten. So what accounts 0:04:58.960 --> 0:05:03.000 for their success, Well, their parents trained the girls every 0:05:03.040 --> 0:05:05.880 single day. They didn't just expose them to chess, they 0:05:06.400 --> 0:05:07.560 fed them on chess. 0:05:07.920 --> 0:05:10.839 The girls received hugs. 0:05:10.320 --> 0:05:15.120 And stern looks and approval and attention based on their 0:05:15.200 --> 0:05:19.120 chess performance, and as a result, their brains came to 0:05:19.240 --> 0:05:24.200 have a great deal of circuitry devoted to chess. Now, 0:05:24.279 --> 0:05:27.719 we've seen in other episodes how the brain is always 0:05:27.800 --> 0:05:32.400 rewriting itself in response to its inputs. But the fact 0:05:32.520 --> 0:05:36.719 is that not all information streaming into the pipelines is 0:05:36.800 --> 0:05:42.280 equally important. How brains adjust themselves has everything to do 0:05:42.400 --> 0:05:46.880 with what you're spending your time on, and that's why 0:05:46.920 --> 0:05:51.880 the Polgar sisters became biological chess machines. And it's the 0:05:51.880 --> 0:05:56.680 same thing with your brain. It'll reconfigure to whatever you're doing. 0:05:56.839 --> 0:06:02.160 So if you decide to make a career change to ornithology, 0:06:02.200 --> 0:06:06.160 the study of birds, more of your neural resources will 0:06:06.200 --> 0:06:10.960 become devoted towards learning the subtle differences between birds, like 0:06:11.000 --> 0:06:15.719 their wing shape, or their breast coloration, or their beak size, 0:06:16.120 --> 0:06:21.080 while maybe previously your neural representation of birds with something 0:06:21.120 --> 0:06:24.760 more crude, like is that a birder and airplane. So 0:06:24.880 --> 0:06:28.640 let's dive in to unpack how the brain makes changes 0:06:28.720 --> 0:06:31.680 and when it doesn't, which will tell us everything we 0:06:31.720 --> 0:06:35.159 need to know about how to make changes stick in 0:06:35.279 --> 0:06:39.839 your own brain. There's a great story about the violinist 0:06:39.920 --> 0:06:44.880 Yetsak Pearlman after one of his concerts and admiring concertgoer 0:06:45.000 --> 0:06:48.440 said to him, I would give my life to play 0:06:48.560 --> 0:06:53.320 like that, and Pearlman said, I did, Now what did 0:06:53.360 --> 0:06:57.120 he mean? Well, every morning, Pearlman drags himself out of 0:06:57.120 --> 0:07:00.360 bed at five point fifteen. He takes a shower and batakfast, 0:07:00.680 --> 0:07:03.839 and then digs into his four and a half hour 0:07:04.080 --> 0:07:07.720 morning practice. He then takes a lunch and an exercise session, 0:07:08.160 --> 0:07:12.480 and then launches his afternoon practice for another four and 0:07:12.480 --> 0:07:15.400 a half hours. He does this every day of the year, 0:07:15.880 --> 0:07:18.640 except for concert days, when he does only the morning 0:07:18.680 --> 0:07:23.600 practice session. And you know what, Brain circuitry comes to 0:07:23.640 --> 0:07:28.520 reflect what you do. So the cortex of Jasah Pearlman, 0:07:28.800 --> 0:07:33.760 or any highly trained musician changes through time into something different. 0:07:33.840 --> 0:07:38.120 And this isn't a metaphorical claim. You can see this 0:07:38.240 --> 0:07:41.160 with brain imaging, even with an untrained eye. 0:07:41.520 --> 0:07:42.400 Let me tell you how. 0:07:42.720 --> 0:07:46.000 If you look at the strip of brain right underneath 0:07:46.000 --> 0:07:49.560 where you wear headphones, that's an area called the motor cortex, 0:07:50.000 --> 0:07:53.080 and that's what directs your body how to move all 0:07:53.120 --> 0:07:58.000 of its six hundred exquisitely beautiful muscles. Now, if you 0:07:58.200 --> 0:08:01.360 zoom in on a region of the cortex involved in 0:08:01.840 --> 0:08:05.880 hand movement, you'll find something amazing, which is that musicians 0:08:06.360 --> 0:08:09.800 have a little puckered shape on their cortex where non 0:08:09.880 --> 0:08:13.920 musicians don't. So think of it like an extra wrinkle 0:08:14.160 --> 0:08:16.960 on the wrinkly outer bit of the brain, the cortex. 0:08:17.440 --> 0:08:18.880 Why do the musicians have this. 0:08:19.280 --> 0:08:23.680 It's because they use the muscles of their hands in 0:08:23.720 --> 0:08:28.280 an extraordinarily detailed way, much more so than non musicians, 0:08:28.880 --> 0:08:29.560 so their. 0:08:29.360 --> 0:08:32.680 Brains devote more real estate to that task. 0:08:33.200 --> 0:08:37.880 The thousands of hours of practice on the instrument physically 0:08:37.960 --> 0:08:42.400 molds their brains. And by the way, this is wildly specific. 0:08:42.640 --> 0:08:46.760 So imagine that you compare the brain of a violinist 0:08:46.880 --> 0:08:51.640 like Pearlman to the brain of a pianist like Vladimir Ashkenazi. 0:08:52.160 --> 0:08:56.000 What they both have in common is a deep dedication 0:08:56.120 --> 0:08:59.360 to their craft and countless hours of practice, and yet 0:09:00.160 --> 0:09:04.520 their brains look sufficiently different that you can easily see 0:09:04.920 --> 0:09:10.040 which brain belongs to whom. And that's because string players 0:09:10.120 --> 0:09:14.000 like Pearlman show that extra wrinkle mostly on one side 0:09:14.000 --> 0:09:17.600 and one hemisphere, because his left fingers are doing all 0:09:17.600 --> 0:09:20.680 the detailed work while the right hand mostly just runs 0:09:20.720 --> 0:09:24.760 the bow over the strings. In contrast, a pianist like 0:09:24.840 --> 0:09:29.600 Ashkenazi has that extra wrinkle in both hemispheres because both 0:09:29.640 --> 0:09:33.760 of his hands are performing meticulous patterns on the ivories. 0:09:34.520 --> 0:09:38.079 So simply by looking at the brain which used to 0:09:38.120 --> 0:09:39.800 be done in autopsy, but now you can do with 0:09:39.840 --> 0:09:44.160 a brain scan. You can tell what kind of musician 0:09:44.240 --> 0:09:46.480 you have in the scanner. You can discern this just 0:09:46.520 --> 0:09:51.199 by looking at the wrinkly bits on the motor cortex. 0:09:51.840 --> 0:09:55.160 And we can read even more from the brain's patterns. 0:09:55.600 --> 0:09:58.720 It represents not only that a hand is doing less 0:09:58.800 --> 0:10:01.280 or more, but sometimes what what in particular it's doing. 0:10:01.559 --> 0:10:04.240 So let's say you get a job at an assembly 0:10:04.320 --> 0:10:07.520 line and you're randomly assigned to one of two jobs. 0:10:07.559 --> 0:10:12.400 Either you put little marbles into jars, or your job 0:10:12.480 --> 0:10:16.240 is to screw the jar lid shut. Okay, so both 0:10:16.320 --> 0:10:20.480 jobs use your right hand, but the first requires fine 0:10:20.720 --> 0:10:24.360 use of your fingertips, while screwing the lid on makes 0:10:24.440 --> 0:10:27.679 use of your wrist and forearm. So if you're the 0:10:28.240 --> 0:10:32.160 jar filler, the real estate in your cortex that represents 0:10:32.200 --> 0:10:36.360 your fingers will increase, and this is at the expense 0:10:36.400 --> 0:10:38.559 of the real estate devoted to your wrists and forearms. 0:10:39.240 --> 0:10:42.680 If you are the lid turner, the opposite happens. You 0:10:42.760 --> 0:10:47.360 get more representation for your wrist and forearm and less 0:10:47.559 --> 0:10:51.240 for the detailed movement of your fingers. So in this way, 0:10:51.600 --> 0:10:55.760 what you do over and over becomes reflected in the 0:10:55.800 --> 0:11:00.360 structure of your brain, and these changes involve more than 0:11:00.400 --> 0:11:01.520 the motor cortex. 0:11:01.600 --> 0:11:02.960 For example, if. 0:11:02.800 --> 0:11:06.760 You spend months learning to read Braille, the bit of 0:11:06.800 --> 0:11:10.640 your cortex that represents touch from the index finger that 0:11:10.720 --> 0:11:14.720 will grow. If you take up juggling as an adult, 0:11:15.160 --> 0:11:18.800 the visual areas of your brain involved in that they increase. 0:11:19.640 --> 0:11:23.720 This is because brains reflect not simply the outside world, 0:11:23.800 --> 0:11:28.800 but more specifically your outside world, and this is what 0:11:29.080 --> 0:11:34.680 underlies getting good at something. Professional tennis players like Serena 0:11:34.720 --> 0:11:37.679 and Venus Williams they spend years training so that the 0:11:37.800 --> 0:11:47.880 right moves will come automatically in the heat of the game. Step, pivot, backhand, charge, fallback, aim, smash. 0:11:48.240 --> 0:11:49.000 They train for. 0:11:49.200 --> 0:11:53.040 Thousands of hours to burn the moves down into the 0:11:53.120 --> 0:11:57.640 unconscious circuitry of the brain. They craft their brains into 0:11:57.679 --> 0:12:01.920 overtrained machinery. He might have heard of the ten thousand 0:12:02.000 --> 0:12:04.839 hour rule, which suggests that you need to practice a 0:12:04.920 --> 0:12:08.319 skill for that many hours to become an expert, whether 0:12:08.360 --> 0:12:12.360 this is surfboarding or spelunking, or saxophone playing or whatever. 0:12:13.160 --> 0:12:16.960 Although we can't quantify the exact number of hours, the 0:12:17.080 --> 0:12:21.120 general idea is correct. You need massive amounts of repetition 0:12:21.679 --> 0:12:26.280 to dig the subway maps of the brain. There's a 0:12:26.320 --> 0:12:28.719 guy that I mentioned in an earlier episode. His name 0:12:28.720 --> 0:12:32.000 is Destin Sandlin, and he made a video where he 0:12:32.080 --> 0:12:35.400 tries to ride a bike that someone gave him with 0:12:35.720 --> 0:12:39.680 reversed steering, so when you push the handlebars to the left, 0:12:40.000 --> 0:12:42.680 the wheel turns to the right and vice versa. This 0:12:42.840 --> 0:12:45.839 is a super difficult thing to learn how to ride. 0:12:46.520 --> 0:12:49.439 So what he did is he spent every day working 0:12:49.480 --> 0:12:52.920 on this and trying it out, and he crashed and crashed, 0:12:52.960 --> 0:12:56.520 but eventually he got it. But the point I want 0:12:56.559 --> 0:12:59.080 to make here is that you know, he's an engineer, 0:12:59.400 --> 0:13:02.719 and it only took him a few seconds to cognitively 0:13:02.960 --> 0:13:08.440 understand how the bike worked, but that proved insufficient to 0:13:08.640 --> 0:13:13.000 ride it. He needed to invest weeks and weeks of practice. 0:13:13.679 --> 0:13:16.160 Hence the ten thousand hour rule. 0:13:17.160 --> 0:13:21.599 And this dynamic changing of the brain happens from intensive 0:13:21.920 --> 0:13:24.680 physical practice that you do, whether that's swimming or playing 0:13:24.720 --> 0:13:28.000 the harmonica, or swinging a tennis racket or using a 0:13:28.120 --> 0:13:32.199 rake or whatever. But these measurable brain changes, they don't 0:13:32.240 --> 0:13:35.079 just apply to the physical they apply to the mental also, 0:13:35.480 --> 0:13:39.720 so for example, when medical students study for their final 0:13:39.800 --> 0:13:43.480 exams over the course of three months, particular areas of 0:13:43.520 --> 0:13:46.559 their cortex changed so much that you can see this 0:13:46.720 --> 0:13:50.600 on brain scans with the naked eye. And you see 0:13:50.640 --> 0:13:54.360 something similar if you teach a person how to read 0:13:54.559 --> 0:13:59.680 backward through a mirror. And here's another example. Areas of 0:13:59.679 --> 0:14:04.040 the brain that are involved in spatial navigation are visibly 0:14:04.200 --> 0:14:08.439 different in London taxi drivers from the rest of the population. 0:14:09.160 --> 0:14:13.280 In each hemisphere, the taxi drivers have an enlarged region 0:14:13.360 --> 0:14:16.800 part of the hippocampus, which is an area involved in 0:14:16.840 --> 0:14:38.600 your internal maps of the outside world. So what you 0:14:38.680 --> 0:14:42.720 spend your time on changes your brain. You are more 0:14:43.120 --> 0:14:47.280 than what you eat. You become the information you digest. 0:14:47.680 --> 0:14:50.240 And this is how the Polgar sisters were able to 0:14:50.320 --> 0:14:54.560 blossom into world champion chess players. It's not because some 0:14:55.320 --> 0:14:59.120 gene codes for skill at chess. It's because they practiced 0:14:59.280 --> 0:15:04.000 over and over chiseling pathways in their brains to encode 0:15:04.080 --> 0:15:07.840 the powers and patterns of knights and rooks and bishops 0:15:07.840 --> 0:15:11.480 and ponds and kings and queens. So brains come to 0:15:11.960 --> 0:15:13.720 reflect their world. 0:15:14.400 --> 0:15:17.680 But how does this happen? Exactly. Well, let's see the. 0:15:17.640 --> 0:15:21.160 Answer by zooming in on a weird illusion that most 0:15:21.160 --> 0:15:26.120 of us have experienced, the phantom phone vibration. I recently 0:15:26.120 --> 0:15:28.320 saw a meme online. It was a picture of a 0:15:28.400 --> 0:15:31.760 human brain with the title that reads, Hey, I think 0:15:31.800 --> 0:15:34.200 your phone just buzzed in your pocket, and then on 0:15:34.240 --> 0:15:37.400 the bottom it reads, just kidding. Your phone isn't even 0:15:37.480 --> 0:15:41.800 in your pocket, you moron. Now, the phantom cell phone 0:15:41.880 --> 0:15:45.560 vibration is a menace that is unique to the twenty 0:15:45.560 --> 0:15:50.280 first century. It happens because of a momentary spasm or 0:15:50.400 --> 0:15:53.480 quivering or shaking, or a touch on your leg, And 0:15:53.560 --> 0:15:56.640 as long as the frequency and the duration of that 0:15:56.720 --> 0:16:00.760 feeling is vaguely similar to that made by your phone, 0:16:01.040 --> 0:16:04.760 your brain decides on your behalf, that's something interesting is 0:16:04.760 --> 0:16:09.080 happening with your phone. So thirty years ago, if you 0:16:09.160 --> 0:16:12.520 had noticed a leg twitch, you would have interpreted the 0:16:12.560 --> 0:16:16.160 feeling as a fly landing on you, or a movement 0:16:16.200 --> 0:16:21.160 of your clothing, or something accidentally brushing past you. So 0:16:21.360 --> 0:16:25.480 why does your interpretation differ from one generation to the next, 0:16:26.120 --> 0:16:31.320 Because your phone now serves as the optimal explanation for 0:16:31.360 --> 0:16:35.560 a whole range of twitchy feelings. So here's how to 0:16:35.600 --> 0:16:39.080 understand what's happening there in the brain. Think of a 0:16:39.280 --> 0:16:45.080 mountainous landscape. Now, picture a lake somewhere there that's encircled 0:16:45.080 --> 0:16:48.960 by mountains. For a rain drop to end up in 0:16:48.960 --> 0:16:51.360 that lake, it doesn't need to fall from the sky 0:16:51.560 --> 0:16:55.400 and land directly in the water. Instead, it only needs 0:16:55.440 --> 0:16:59.280 to hit the surrounding hillsides. It can land on the 0:16:59.320 --> 0:17:02.960 northern slope or the southern, or the eastern incline or 0:17:03.000 --> 0:17:07.119 the western and in any case it's gonna slide down into 0:17:07.240 --> 0:17:10.080 the lake. So the lake is what's known as an 0:17:10.119 --> 0:17:15.520 attractor state. Anything nearby will flow to that spot, and 0:17:15.600 --> 0:17:19.320 you have lots of such attractor states in your brain. 0:17:19.920 --> 0:17:23.439 So the feeling on your thigh doesn't have to be 0:17:23.600 --> 0:17:24.600 a buzzing phone. 0:17:24.640 --> 0:17:26.760 It can be a slight shift. 0:17:26.400 --> 0:17:29.159 Of your genes or a twitch of your thigh muscle, 0:17:29.680 --> 0:17:33.000 or an itch or graze past the sofa. 0:17:33.160 --> 0:17:37.359 As long as the feeling is close, the signals. 0:17:37.080 --> 0:17:41.760 Slide down the landscape to their attractor state, and then 0:17:41.800 --> 0:17:46.399 you reach to check for an important message. The landscape 0:17:46.600 --> 0:17:51.879 gets formed by what is important in your world. For 0:17:51.960 --> 0:17:55.560 another example, think about the way we interpret the sounds 0:17:55.600 --> 0:17:58.400 of language. It feels natural to you that you can 0:17:58.560 --> 0:18:03.040 understand the sounds of your native language, but foreign languages 0:18:03.400 --> 0:18:06.359 often have really close sounds that you can't hear the 0:18:06.400 --> 0:18:07.880 difference between. 0:18:07.600 --> 0:18:11.560 Like ooh and eh. But why why can you not 0:18:11.720 --> 0:18:12.280 hear those? 0:18:13.040 --> 0:18:16.320 As it turns out, there is something different about the 0:18:16.480 --> 0:18:20.480 brains of the people who speak those languages. But they 0:18:20.520 --> 0:18:24.359 weren't born that way, and neither were you. If you 0:18:24.400 --> 0:18:27.439 look at the space of all the possible sounds that 0:18:27.520 --> 0:18:30.959 humans can make with our mouths, it makes a relatively 0:18:31.080 --> 0:18:34.399 smooth continuum. You can kind of make any sound. But 0:18:34.560 --> 0:18:39.360 despite this, you learn from experience that specific sounds mean 0:18:39.440 --> 0:18:42.800 the same thing, whether they're uttered by your dad, or 0:18:42.840 --> 0:18:47.159 your babysitter or your teacher. Your brain figures out that 0:18:47.359 --> 0:18:52.280 a drawn out E and eclip to e both belong 0:18:52.359 --> 0:18:55.679 to the E category, or maybe your friend from Texas 0:18:55.680 --> 0:19:00.399 says a or whatever. But your experience teaches you that 0:19:00.640 --> 0:19:04.600 all the speakers mean the same sound, regardless of exactly 0:19:04.640 --> 0:19:08.080 how they're pronouncing it, and so your neural networks carve 0:19:08.119 --> 0:19:12.160 out a landscape in which all these sounds roll down 0:19:12.160 --> 0:19:16.840 the hillsides to the same interpretation. There's a lake in 0:19:16.880 --> 0:19:20.560 your brain that represents E, and all the inputs from 0:19:20.560 --> 0:19:25.120 all around end up in that lake and in neighboring valleys, 0:19:25.160 --> 0:19:28.320 you gather up sounds that are equivalent to A or 0:19:28.520 --> 0:19:32.920 I or O and so on. So with time, your 0:19:33.080 --> 0:19:37.199 landscape looks different from someone who's grown up in another 0:19:37.280 --> 0:19:41.800 language and who needs to distinguish the smooth continuum of 0:19:41.920 --> 0:19:46.440 sounds differently than you do. To think about an example 0:19:46.480 --> 0:19:50.880 of this, imagine a baby born in Japan call him Hyato, 0:19:51.320 --> 0:19:55.280 and a baby born in America call him William. From 0:19:55.320 --> 0:19:59.080 their brain's point of view, there is nothing different about them. 0:19:59.720 --> 0:20:04.320 But in Osaka, Hayato hears Japanese all around him. 0:20:04.320 --> 0:20:04.920 From day one. 0:20:05.800 --> 0:20:10.320 In Palo Alto, William hears the tones of English, where 0:20:10.400 --> 0:20:14.120 different sounds carry meaning. An example of what these two 0:20:14.200 --> 0:20:17.000 babies hear differently is the distinction between the. 0:20:17.400 --> 0:20:19.480 R and L sounds. 0:20:19.920 --> 0:20:24.160 So in English, these carry information like the word right 0:20:24.400 --> 0:20:29.480 versus light or raw versus law, But in Japanese there's 0:20:29.520 --> 0:20:33.040 no distinction between these two sounds. So as a result, 0:20:33.680 --> 0:20:39.359 William's internal landscape builds a mountain range between his interpretation 0:20:39.640 --> 0:20:44.200 of R and L, such that the difference between these 0:20:44.200 --> 0:20:50.040 two sounds is perceptually clear. In Hyato's brain, the landscape 0:20:50.080 --> 0:20:53.480 develops into a big valley, so that both R and 0:20:53.760 --> 0:20:57.320 L flow into a single lake because they have an 0:20:57.400 --> 0:21:03.639 identical interpretation. So as a result, Hyato can't hear the 0:21:03.760 --> 0:21:08.200 difference between those two sounds. Now, obviously, the children's brains 0:21:08.200 --> 0:21:12.280 were not born this way. Had William's pregnant mother moved 0:21:12.359 --> 0:21:16.119 to Osaka and Hyato's pregnant mother to Palo Alto, the 0:21:16.119 --> 0:21:19.080 boys would have had no trouble in becoming fluent speakers 0:21:19.119 --> 0:21:20.640 and listeners in their new language. 0:21:21.240 --> 0:21:23.560 As opposed to a genetic issue. 0:21:24.080 --> 0:21:29.359 Their neural landscapes are carved by what is relevant in 0:21:29.400 --> 0:21:32.800 their immediate environment. And what's fascinating is that you can 0:21:32.960 --> 0:21:37.520 see this carving happening even before the children learn how 0:21:37.560 --> 0:21:42.320 to speak. For example, make a continuous R sound and 0:21:42.359 --> 0:21:47.320 then switch it over to L. So L, now, how 0:21:47.359 --> 0:21:51.680 can you tell if an infant here's that change? 0:21:51.800 --> 0:21:53.680 So it turns out the trick. 0:21:53.400 --> 0:21:57.560 To the experiment is this, Infants will suck faster at 0:21:57.560 --> 0:22:00.640 the nipple when they detect a chain. When they hear 0:22:00.640 --> 0:22:03.159 a change from one sound to another sound, they go 0:22:03.240 --> 0:22:06.480 from suck suck suck to suck suck, suck, suck. So 0:22:06.520 --> 0:22:10.560 at the age of six months, both Hyato and William 0:22:11.240 --> 0:22:14.760 will both suck faster when the R changes to L. 0:22:15.040 --> 0:22:20.840 But by twelve months, Hyato stops detecting the change. R 0:22:20.920 --> 0:22:23.840 and L sound the same to him. Both sounds are 0:22:24.000 --> 0:22:29.080 sliding down into the same valley. Hyato's brain has lost 0:22:29.119 --> 0:22:33.200 the ability to distinguish these sounds, while William's brain, having 0:22:33.560 --> 0:22:36.760 passively listened to his parents speak tens of thousands of 0:22:36.800 --> 0:22:41.720 English words, has learned that there's information carried in the 0:22:41.760 --> 0:22:45.960 difference between these two sounds. Hyato's brain, meanwhile, has picked 0:22:46.040 --> 0:22:50.720 up on other sound distinctions, which to William would be indistinguishable. 0:22:51.680 --> 0:22:57.720 So your auditory system begins universally and then wires itself 0:22:57.760 --> 0:23:02.359 to maximize the distinction unique to your language, depending on 0:23:02.720 --> 0:23:05.560 where on the planet you happened to stick your head 0:23:05.600 --> 0:23:10.080 out of the womb. And similarly, the buzzing phone isn't 0:23:10.119 --> 0:23:15.680 something you were born to detect. Instead, it's high relevance 0:23:15.920 --> 0:23:19.639 carves your neural landscape such that you have a broad 0:23:19.960 --> 0:23:23.080 catch all for neighboring sensations, all of which you will 0:23:23.359 --> 0:23:27.520 interpret as a buzzing cell phone in your pocket. Like kyata. 0:23:27.640 --> 0:23:30.760 With the R and the L, you combine the twitches 0:23:30.800 --> 0:23:35.040 and vibrations and quiverings into a single interpretation of what 0:23:35.359 --> 0:23:39.520 just happened. Now, from what we've seen so far, we 0:23:39.600 --> 0:23:43.439 might think that repetition is the key to molding the 0:23:43.480 --> 0:23:47.320 circuitry in your brain. But in fact, there's a deeper 0:23:47.359 --> 0:23:51.680 principle at work. So now we're going to talk about relevance. 0:23:52.119 --> 0:23:55.360 There's an old joke that goes, how many psychiatrists does 0:23:55.400 --> 0:23:57.679 it take to change a light bulb? And the answer 0:23:57.760 --> 0:24:01.160 is only one, But the light bulb has to want 0:24:01.200 --> 0:24:05.000 to change. Now, if you listen to episode two, you 0:24:05.040 --> 0:24:08.320 may remember a dog that I talked about named Faith. 0:24:08.560 --> 0:24:12.359 She is very memorable because Faith was born with out 0:24:12.359 --> 0:24:15.400 front legs and she figured out how to walk by 0:24:15.560 --> 0:24:18.000 pedaly on her hind legs, sort of like a human. 0:24:18.560 --> 0:24:18.840 Now. 0:24:18.960 --> 0:24:21.920 When I told her story in episode two, I said 0:24:21.920 --> 0:24:24.640 it as though her brain had just figured out her 0:24:24.720 --> 0:24:27.920 unusual body plan. But we can now dig a little 0:24:27.960 --> 0:24:32.520 deeper for a hidden bone. Was there something special about Faith? 0:24:32.560 --> 0:24:35.439 Could any dog have pulled us off? And if they 0:24:35.440 --> 0:24:37.399 could have, why don't all dogs walk by? 0:24:37.480 --> 0:24:37.879 Peeda Ly? 0:24:39.240 --> 0:24:44.280 Faith's rewritten maps were all about relevance to her life. 0:24:44.760 --> 0:24:49.399 Her brain was shaped by her goals. Faith needed to 0:24:49.440 --> 0:24:52.920 get to her food. That required a solution. It wasn't 0:24:52.920 --> 0:24:54.959 going to be the same one that was used by 0:24:55.000 --> 0:24:58.919 her four legged siblings. She had to derive a novel solution, 0:24:59.560 --> 0:25:03.600 so her brain tried out various strategies until it found 0:25:03.600 --> 0:25:07.119 when that worked balancing on her two back legs and 0:25:07.200 --> 0:25:11.439 lurching forward step after step. This allowed her to get 0:25:11.480 --> 0:25:14.520 what she needed, and after a while, she became good 0:25:14.560 --> 0:25:18.840 at this method of locomotion. In the absence of finding 0:25:18.880 --> 0:25:21.879 an answer to her challenge, she would have starved and died. 0:25:22.680 --> 0:25:27.320 Her drive for survival allowed the flexible circuitry in her 0:25:27.320 --> 0:25:31.119 brain to try out a bunch of hypotheses and solve 0:25:31.480 --> 0:25:34.919 the problem getting her to food and shelter and loved ones. 0:25:35.800 --> 0:25:37.359 So goals matter. 0:25:37.880 --> 0:25:42.120 A brain's goals play a critical role in how and 0:25:42.160 --> 0:25:47.200 when it changes. For the Polgar sisters, achieving their expertise 0:25:47.280 --> 0:25:52.080 depended on a desire to achieve their expertise. Same with 0:25:52.200 --> 0:25:56.760 Yitzak Pearlman or Vladimir Ashkenazi. Imagine for a moment that 0:25:57.040 --> 0:26:01.919 Serena and Venus Williams had a brother, Fred, and that 0:26:02.000 --> 0:26:04.720 their parents had put a tennis racket in Fred's hands 0:26:04.720 --> 0:26:07.240 and forced him to go through all the years of 0:26:07.359 --> 0:26:11.320 practicing that his sisters went through. But imagine that he 0:26:11.480 --> 0:26:15.760 found tennis repulsive. He never got good feedback from his 0:26:15.840 --> 0:26:19.960 classmates about his performances, and he didn't win any contests, 0:26:20.440 --> 0:26:24.600 and his elders didn't lavish him with praise. The result 0:26:24.680 --> 0:26:29.680 of all that practice would be nothing. Fred's brain would 0:26:29.760 --> 0:26:34.159 show little reorganization. Although his body was going through the 0:26:34.240 --> 0:26:39.160 same motions as his sisters, the motions would be misaligned 0:26:39.200 --> 0:26:43.720