WEBVTT - Ep4 "Do people experience different realities?" 0:00:06.760 --> 0:00:10.080 Why do some people think that the Northern lights make 0:00:10.280 --> 0:00:13.640 noise and other people say that that's impossible. And why 0:00:13.640 --> 0:00:19.840 did Pythagoras think that numbers had colors and personality? And 0:00:19.880 --> 0:00:22.520 what does any of that have to do with creators 0:00:22.560 --> 0:00:26.360 like Vladimir Nabokoff and Billie Eilish, And why do you 0:00:26.360 --> 0:00:29.320 think that a high note on the piano is brighter 0:00:29.360 --> 0:00:34.400 than a low note. Welcome to Inner Cosmos with me, 0:00:34.640 --> 0:00:40.120 David Eagleman. I'm a neuroscientist and an author at Stanford University, 0:00:41.479 --> 0:00:45.639 and I've spent my whole career studying the intersection between 0:00:45.880 --> 0:00:55.000 how the brain works and how we experience life. On 0:00:55.080 --> 0:00:58.160 today's episode, we're going to talk about how we can 0:00:58.240 --> 0:01:02.959 all experience reality a little bit differently. Okay, so this 0:01:03.000 --> 0:01:06.920 story begins in the early nineteen thirties. You've heard about 0:01:06.920 --> 0:01:10.000 the Northern lights, or maybe you've even seen them in person. 0:01:10.040 --> 0:01:15.039 They're these rippling rivers of green blue light in the sky. 0:01:15.480 --> 0:01:18.520 But here's the really strange part. About one hundred years 0:01:18.560 --> 0:01:22.319 ago some people started to make the claim that the 0:01:22.360 --> 0:01:26.399 northern lights make noise. In nineteen thirty one, in the 0:01:26.440 --> 0:01:30.800 journal Nature, a scientist named Harold's Fairdrop wrote a short 0:01:30.840 --> 0:01:35.760 paper that he called Audibility of the Aurora polaris, and 0:01:35.840 --> 0:01:40.000 he wrote, quote, it cannot be doubted that many persons 0:01:40.000 --> 0:01:45.000 have heard a distinct sound when watching a brilliant display 0:01:45.120 --> 0:01:50.520 of aurora. Communications regarding the auroral sound appear now and then, 0:01:51.080 --> 0:01:51.800 and recently. 0:01:52.200 --> 0:01:53.320 Mister J. H. 0:01:53.440 --> 0:01:56.360 Johnson has collected a great number of reports on the 0:01:56.440 --> 0:02:02.520 auroral sound in his pamphlet concern the Aurora borealis. Then, 0:02:02.720 --> 0:02:06.280 in nineteen thirty three in the journal Science, someone named 0:02:06.320 --> 0:02:10.080 Clark Garber wrote another letter on the audibility of the 0:02:10.160 --> 0:02:15.320 Aurora borealis, and Garber wrote quote, some scientists have claimed 0:02:15.400 --> 0:02:19.639 with much positiveness that the aurora emits no audible sounds. 0:02:20.080 --> 0:02:22.880 In my own mind, there can be no doubt left 0:02:23.320 --> 0:02:27.320 as to the audibility of certain types of aurora, for 0:02:27.480 --> 0:02:30.480 I have heard them under conditions when no other sound 0:02:30.560 --> 0:02:34.440 could have been interpreted as such, for no other sounds 0:02:34.480 --> 0:02:37.680 were present. And he goes on to say that he 0:02:37.800 --> 0:02:41.440 first heard about the possibility that the aurora makes sounds 0:02:41.840 --> 0:02:44.720 from the eskimos, and he says he was skeptical at first, 0:02:44.760 --> 0:02:48.919 but then he experienced this sound himself. Now I stumbled 0:02:48.960 --> 0:02:51.680 on these papers a few years ago, and I was 0:02:51.720 --> 0:02:56.840 surprised because the problem is that it's not scientifically possible 0:02:57.000 --> 0:03:01.400 for the Aurora to make sound. The Northern Lights happen 0:03:01.520 --> 0:03:06.040 because photons from the Sun are banging into gases in 0:03:06.040 --> 0:03:09.720 the Earth's upper atmosphere, and that causes all that amazing light. 0:03:10.080 --> 0:03:13.720 But those collisions are happening eighty kilometers up in the sky, 0:03:14.600 --> 0:03:17.639 which means that even if there were sound, it would 0:03:17.720 --> 0:03:20.960 take about four minutes for that sound to get down here. 0:03:21.440 --> 0:03:24.600 And yet people who claim to hear the sound say 0:03:24.639 --> 0:03:28.240 they see it happening in lockstep with the lights. And 0:03:28.320 --> 0:03:31.760 more importantly, for sound to travel it needs a medium 0:03:32.120 --> 0:03:35.360 like air, and that's because sound moves as compression of 0:03:35.400 --> 0:03:38.240 the air. In other words, molecules in the air get 0:03:38.280 --> 0:03:41.240 pushed closer together and farther apart, and that's what a 0:03:41.360 --> 0:03:45.560 sound wave is. But at the altitude where the Northern 0:03:45.640 --> 0:03:49.960 Lights come into being, the atmosphere is essentially a vacuum. 0:03:50.520 --> 0:03:52.280 So this means there's probably no. 0:03:52.360 --> 0:03:56.040 Sound happening even up there, and if there were, it 0:03:56.080 --> 0:03:56.800 couldn't get all. 0:03:56.800 --> 0:03:58.520 The way to us until four minutes later. 0:03:58.920 --> 0:04:02.600 So this became a top of debate because as time 0:04:02.680 --> 0:04:07.280 went on, thousands of Arctic explorers listened carefully for these 0:04:07.280 --> 0:04:11.120 sounds but didn't hear anything. So this idea of the 0:04:11.160 --> 0:04:15.600 northern lights making noise came to be understood as a superstition. 0:04:16.279 --> 0:04:20.400 So what was happening here? Were some people simply lying 0:04:20.560 --> 0:04:25.240 in scientific journals It's happened before, But it seems that 0:04:25.320 --> 0:04:29.719 some people really believed and still believe, the lights make sound, 0:04:30.279 --> 0:04:33.400 even though the physics don't seem to allow that. So 0:04:33.600 --> 0:04:37.440 worse Ferdrup and Garber lying, were they looking for attention 0:04:38.120 --> 0:04:41.560 that they somehow have better hearing? Even today? This is 0:04:41.680 --> 0:04:46.880 contentious in geophysics. Some people argue from their personal experience 0:04:46.960 --> 0:04:51.480 that it happens, and others point out that it simply can't. 0:04:52.200 --> 0:04:56.320 To unpack this mystery, let's jump back even farther back 0:04:56.400 --> 0:05:01.800 another twenty five hundred years to Pythagoras. Pythagoras was one 0:05:01.839 --> 0:05:06.680 of Greece's most famous philosophers, and he massively influenced the 0:05:06.800 --> 0:05:11.680 trajectory of Western thought through his religious teachings his political teachings. 0:05:12.080 --> 0:05:14.880 In part this was due to his influence on Plato 0:05:14.960 --> 0:05:18.560 and Aristotle. But you've probably heard of Pythagoras because of 0:05:18.600 --> 0:05:24.159 his love of numbers. He loved geometry and theories about 0:05:24.240 --> 0:05:28.800 instrument tuning and the theory of proportions, and you'll probably 0:05:28.839 --> 0:05:33.880 remember the Pythagorean theorem from school in a right triangle, 0:05:34.360 --> 0:05:38.080 A squared plus B squared equals C squared. But there 0:05:38.120 --> 0:05:43.760 was something very odd about Pythagoras's relationship with numbers. I'm 0:05:43.800 --> 0:05:47.760 going to quote from the Yale historian Robert Brumbaugh, who 0:05:47.800 --> 0:05:53.800 notes that for Pythagoras quote, each number had its own personality, 0:05:54.560 --> 0:06:02.760 masculine or feminine, perfect or incomplete, beautiful or ugly. For Pythagoras, 0:06:02.839 --> 0:06:07.320 ten was the very best number. This feeling modern mathematics 0:06:07.320 --> 0:06:11.640 has deliberately eliminated, but we still find overtones of it 0:06:11.839 --> 0:06:20.159 in fiction and poetry. Now, how could numbers have gender 0:06:20.360 --> 0:06:25.880 and personality? Did Pythagoras have fundamental insight about numbers that 0:06:25.920 --> 0:06:29.080 the rest of us couldn't see? Or was he making 0:06:29.160 --> 0:06:32.240 up stuff to impress his followers, or was he mentally 0:06:32.279 --> 0:06:36.920 ill or taking drugs. The way that he personified numbers 0:06:37.080 --> 0:06:41.599 is traditionally discussed as an interesting oddity, or occasionally you'll 0:06:41.640 --> 0:06:46.400 find numerologists who cite Pythagoras's view as evidence that he 0:06:46.440 --> 0:06:49.800 had a cosmic insight into the true natures of numbers. 0:06:50.240 --> 0:06:55.919 I've seen websites that springboard from Pythagoras's number personalities to 0:06:56.080 --> 0:06:59.080 sell new age models of the nature of the universe. 0:06:59.400 --> 0:07:02.760 But most people don't believe that the number five has 0:07:02.800 --> 0:07:06.240 a gender or a personality. So what was going on 0:07:06.360 --> 0:07:08.719 here and what does this have to do with the 0:07:08.760 --> 0:07:12.560 scientists who claim to hear sounds from the Northern Lights. 0:07:12.840 --> 0:07:16.080 The answer to both these mysteries is related to something 0:07:16.440 --> 0:07:19.560 I'm going to discuss a lot across many episodes of 0:07:19.600 --> 0:07:25.320 this podcast, and that is the difference in people's internal worlds. 0:07:25.800 --> 0:07:28.160 We all like to believe that our experience of the 0:07:28.160 --> 0:07:31.239 world is the same as everyone else's. But the key 0:07:31.440 --> 0:07:35.440 to unlocking the mystery of the Northern Lights or Pythagoras's 0:07:35.520 --> 0:07:38.960 view of numbers is to understand that people can have 0:07:39.240 --> 0:07:44.840 very different realities on the inside. The interesting part, as 0:07:44.880 --> 0:07:49.200 we'll see, is that we accept the reality presented to us. 0:07:49.560 --> 0:07:53.160 Your brain constructs a story about what's going on out there, 0:07:53.680 --> 0:07:57.880 and you accept that as your reality. So imagine I 0:07:58.080 --> 0:08:00.680 showed you a picture of a crowd of people. If 0:08:00.680 --> 0:08:04.440 you're color blind, all you see are shades of gray. 0:08:04.600 --> 0:08:07.400 If you're not colorblind, you see it in full color. 0:08:07.800 --> 0:08:11.360 But either way, that's the reality that you know. And 0:08:11.400 --> 0:08:14.360 we now know that a very tiny fraction of the 0:08:14.400 --> 0:08:19.800 female population doesn't just have three types of color photoreceptors 0:08:19.840 --> 0:08:22.600 in their eyes, but they have four types because of 0:08:22.640 --> 0:08:27.440 a mutation, and as a result, they perceive colors that 0:08:27.520 --> 0:08:31.800 the rest of us can't even imagine. Their reality is different. 0:08:32.400 --> 0:08:36.840 So the key is we accept whatever reality our brains 0:08:37.080 --> 0:08:40.679 serve up to us. Okay, So this all leads to 0:08:40.720 --> 0:08:44.440 a very old philosophical question which I think everyone has 0:08:44.480 --> 0:08:47.080 asked at some point in their lives. How do you 0:08:47.320 --> 0:08:50.960 know that what I see as blue is what you 0:08:51.120 --> 0:08:54.840 see as blue? My parents taught me to call that 0:08:54.960 --> 0:08:58.960 thing blue, and your parents taught you to call it blue. 0:08:59.480 --> 0:09:01.760 Two. But inside your. 0:09:01.640 --> 0:09:05.640 Head and inside my head, it might be a different experience. 0:09:05.760 --> 0:09:05.960 Right. 0:09:06.080 --> 0:09:08.120 I might be seeing it as what you would think 0:09:08.160 --> 0:09:12.040 of as green, But it doesn't matter, and we'd never 0:09:12.160 --> 0:09:16.040 know as long as we can transact in the outside world. 0:09:16.320 --> 0:09:18.600 In other words, if I say, hey, can you pass 0:09:18.640 --> 0:09:21.640 me that blue thing, and we both call it blue, 0:09:22.240 --> 0:09:25.960 then the word suffices, even if we're having a different 0:09:26.280 --> 0:09:30.240 internal experience and it turns out. The situation might be 0:09:30.360 --> 0:09:32.760 even worse than that. It may be that what I 0:09:32.920 --> 0:09:36.400 call vision and what you call vision are totally different. 0:09:36.640 --> 0:09:39.800 I might see the world completely upside down from the 0:09:39.800 --> 0:09:43.160 way that you see the world, and it wouldn't matter 0:09:43.520 --> 0:09:46.160 as long as we can agree on things out there, 0:09:46.200 --> 0:09:48.360 and I can throw a ball and you can catch it. 0:09:48.679 --> 0:09:50.679 So what my colleagues and I have worked on for 0:09:50.840 --> 0:09:55.199 years is taking this question or we having different lives 0:09:55.240 --> 0:09:59.040 on the inside and elevating that from the realm of 0:09:59.600 --> 0:10:05.040 phys sophical speculation to actual scientific experiment. And one way 0:10:05.080 --> 0:10:07.640 to get at that this was something my lab is 0:10:07.679 --> 0:10:14.000 studied for fifteen years called sinnesthesia. Synesthesia is a condition 0:10:14.559 --> 0:10:18.040 in which one person might be seeing reality a little 0:10:18.040 --> 0:10:22.200 bit differently from another. So you know the word anesthesia, 0:10:22.280 --> 0:10:28.679 that means no feeling. Synesthesia means joined feeling. It's a 0:10:28.760 --> 0:10:33.560 blending of the senses. Now, there are many forms of synesthesia, 0:10:33.600 --> 0:10:35.959 and one of the most common is where a person 0:10:36.559 --> 0:10:40.800 looks at numbers or letters and that triggers an internal 0:10:40.840 --> 0:10:45.680 experience of color. So for a given synesthete, her eight 0:10:46.120 --> 0:10:49.800 might trigger the experience of blue. She still sees the 0:10:49.880 --> 0:10:52.160 number eight on the page. There if I were to 0:10:52.400 --> 0:10:54.880 write eight with black ink on a white page, she'd 0:10:54.920 --> 0:10:57.640 say that she can see the number, but seeing the 0:10:57.720 --> 0:11:02.800 number eight triggers a blue experience, an internal experience of blue. 0:11:03.679 --> 0:11:06.400 And it's just self evidently true for her that eight 0:11:06.800 --> 0:11:12.040 and blue are connected. Now this isn't just a memorized 0:11:12.080 --> 0:11:15.640 thing that she says, but it's an actual experience. And 0:11:15.760 --> 0:11:20.640 for her, maybe five is yellow, and Saturday is orange, 0:11:20.840 --> 0:11:27.000 and November is purple and so on. Now, the first 0:11:27.040 --> 0:11:30.360 thing to note is that sequences that we learn, like 0:11:30.559 --> 0:11:34.160 letters and numbers and weekdays and months, these are drilled 0:11:34.200 --> 0:11:36.600 into the brain really deeply. They're known in the field 0:11:36.640 --> 0:11:42.440 as overlearned sequences, and these are the things that trigger synesthesia. 0:11:42.800 --> 0:11:47.600 And interestingly, this often goes beyond color in when flavor 0:11:47.640 --> 0:11:52.839 of synesthesia, sequences come to have gender and personality and 0:11:52.920 --> 0:11:58.160 other qualities. So one cynesthete describes the number three as 0:11:58.480 --> 0:12:04.760 a vain, elitist girl, while seven is a shy, wimpy boy. 0:12:05.160 --> 0:12:08.640 This same cynisthe described by my colleague Sean Day. She 0:12:08.800 --> 0:12:13.000 also noted that she doesn't like certain number combinations, like 0:12:13.320 --> 0:12:14.079 ninety four. 0:12:14.840 --> 0:12:17.000 That quote result. 0:12:16.559 --> 0:12:20.960 In putting four, which is a plain but decent, hardworking 0:12:21.000 --> 0:12:25.480 older woman and nine together as they greatly dislike each 0:12:25.520 --> 0:12:28.440 other and do not get along well. And this is 0:12:28.480 --> 0:12:31.800 what was going on with Pythagoras. He had this not 0:12:32.120 --> 0:12:36.480 uncommon form of synesthesia, but his followers didn't know this, 0:12:36.920 --> 0:12:40.760 so they presumably thought he was tapped into some cosmic 0:12:40.840 --> 0:12:44.680 truth about numbers. He obviously liked numbers, but that doesn't 0:12:44.720 --> 0:12:49.400 mean he had access to some deeper significance that others didn't. 0:12:49.920 --> 0:12:53.000 How do we know that, Because each person with this 0:12:53.080 --> 0:12:57.760 particular type of synesthesia has a different association between a 0:12:57.760 --> 0:13:02.280 particular number and a gender personality. So you might think 0:13:02.480 --> 0:13:06.000 three is male and kind, and someone else might think 0:13:06.320 --> 0:13:09.160 three is female and a bit of a comic, and 0:13:09.200 --> 0:13:12.680 so on. There is no right answer. So we're gonna 0:13:12.720 --> 0:13:14.520 come back to this in a moment, But first I 0:13:14.559 --> 0:13:17.800 want to tell you about some other forms of synesthesia. 0:13:18.320 --> 0:13:22.120 It's not just colors or genders or personalities triggered by 0:13:22.559 --> 0:13:27.240 overlearned sequences. There's also a flavor of synesthesia in which 0:13:27.640 --> 0:13:32.160 what you hear causes a visual experience. So you might 0:13:32.559 --> 0:13:35.840 listen to music and that causes you to see moving 0:13:36.000 --> 0:13:41.640 shapes or colors. In my book, Wednesday's Indigo Blue. I 0:13:41.679 --> 0:13:44.040 have a picture of a shape that looks like a 0:13:44.080 --> 0:13:48.640 colorful caterpillar, and this is what one synesthete sees. She 0:13:48.720 --> 0:13:52.240 actually sees this when her furnace kicks on and goes whoosh. 0:13:52.600 --> 0:13:56.160 She has this visual experience that flashes for her. Her 0:13:56.360 --> 0:14:01.240 visual system gets tickled by the noise, and senses can 0:14:01.280 --> 0:14:05.000 be triggered in the other direction, where something visual leads 0:14:05.040 --> 0:14:08.720 to a sound. For some people, when they watch movement 0:14:08.920 --> 0:14:13.280 like a swarm of moving birds or an electric sign blinking, 0:14:13.880 --> 0:14:16.920 they feel like they hear a sound with it. They 0:14:16.920 --> 0:14:20.760 don't see the motion by itself. Their brain imposes sound 0:14:20.840 --> 0:14:24.320 on top of that. It's impossible to separate the motion 0:14:24.480 --> 0:14:27.160 and the sound. And I've proposed that this is the 0:14:27.280 --> 0:14:32.040 solution to the mystery of the Northern lights. It's impossible 0:14:32.040 --> 0:14:34.200 from a physics point of view for the lights to 0:14:34.240 --> 0:14:37.840 be making synchronized noise. But what is possible is for 0:14:37.960 --> 0:14:42.760 a small fraction of the population to be cinnesthetic, such 0:14:42.800 --> 0:14:47.400 that when they see the beautiful moving lights, they hear sound. 0:14:48.280 --> 0:14:51.320 And because of their assumption that our senses tell us 0:14:51.360 --> 0:14:54.920 the truth and that everyone should be having the same experience, 0:14:55.480 --> 0:14:58.000 this has led to over a century of debate about 0:14:58.000 --> 0:15:01.280 whether the lights make noise or not, because if your 0:15:01.600 --> 0:15:04.240 sphare drop or Gerber or any of the others who 0:15:04.360 --> 0:15:07.000 hear the sounds, you'll sit down and you'll write a 0:15:07.120 --> 0:15:11.120 letter to nature or science and insist that you can 0:15:11.160 --> 0:15:16.680 hear it. The important lesson is that we all assume 0:15:17.040 --> 0:15:20.680 our senses tell us the truth and that everyone is 0:15:20.720 --> 0:15:24.520 tapped into the same reality. But when we realize that's 0:15:24.520 --> 0:15:28.160 not necessarily the case, we can take a higher view 0:15:28.200 --> 0:15:31.200 on the scientific literature and look at all these papers 0:15:31.240 --> 0:15:34.440 going back and forth about whether the northern lights make noise, 0:15:35.040 --> 0:15:38.080 and we can understand the game at a different level. 0:15:38.720 --> 0:15:42.120 For most people the answer is no, they don't make noise, 0:15:42.560 --> 0:15:47.200 and for some it's yes. Beyond the relationship of sound 0:15:47.240 --> 0:15:51.560 and vision, there are dozens of forms of synesthesia. My 0:15:51.680 --> 0:15:54.680 colleagues and I have found that essentially any sense that 0:15:54.720 --> 0:15:57.880 you can imagine can be mixed with another. One form 0:15:57.920 --> 0:16:03.240 of synesthesia involves tastes shapes, So when people taste something, 0:16:03.320 --> 0:16:06.680 it makes them feel like they're touching something with their fingertips. 0:16:07.200 --> 0:16:09.880 So you might take a sip of soup and you 0:16:09.920 --> 0:16:13.160 feel something cold and pointy on your fingertips. Or one 0:16:13.200 --> 0:16:16.120 guy determines whether his chicken is cooked right this way. 0:16:16.200 --> 0:16:19.600 He tastes it and judges by what he's feeling on 0:16:19.680 --> 0:16:24.480 his fingertips, is it smooth or glassy or spiky. He 0:16:24.520 --> 0:16:26.720 comes to be a good cook that way. And there's 0:16:26.720 --> 0:16:31.600 also musical synesthesia. For a lot of people, different notes 0:16:31.600 --> 0:16:36.360 of the scale will trigger a color experience. For one 0:16:36.400 --> 0:16:39.680 cynisthee that I test in the lab, when she hits 0:16:39.720 --> 0:16:44.520 the note A on the piano, that's pink, the note 0:16:44.600 --> 0:16:51.440 B is blue. C is goldish white like sunlight. B 0:16:52.160 --> 0:16:58.240 is silvery white like moonlight. E is fiery orange, and 0:16:58.280 --> 0:17:02.480 so on, So she experiences very specific colors that get 0:17:02.520 --> 0:17:06.679 triggered when she hears specific notes. And I know a 0:17:06.680 --> 0:17:10.400 professional drum tuner who goes around for all the famous 0:17:10.480 --> 0:17:13.520 rock and roll bands and tunes their drums, and he 0:17:13.560 --> 0:17:16.560 does it with color, so he can tell if the 0:17:16.640 --> 0:17:18.560 drum is a little bit sharp or a little bit 0:17:18.600 --> 0:17:22.239 flat by the color that he sees in response to 0:17:22.359 --> 0:17:26.840 the sound. Now, not all people with music synesthesia have 0:17:27.000 --> 0:17:31.600 their percepts triggered by a pitch a note. For some people, 0:17:31.720 --> 0:17:36.360 it's the interval between notes like a chord that matters. 0:17:36.760 --> 0:17:41.720 So for one woman, different chords trigger different, very particular 0:17:41.880 --> 0:17:45.199 tastes in the mouth. In a paper in the journal Nature, 0:17:45.600 --> 0:17:50.640 she reported that she uses these sinnesthetic associations to identify 0:17:50.760 --> 0:17:54.240 which chord was just played. And synesthesia can also be 0:17:54.359 --> 0:17:57.880 triggered by an instrument's tamber, the way that it sounds. 0:17:58.359 --> 0:18:01.400 So when a person hears the music of a violin 0:18:01.760 --> 0:18:06.400 versus a tuba, versus a cello versus a flute, the 0:18:06.480 --> 0:18:11.159 timbre of the instrument can trigger very different experiences in 0:18:11.240 --> 0:18:15.800 terms of colors or visualized shapes or whatever. So two 0:18:15.840 --> 0:18:19.480 people might listen to a clarinet playing and that triggers 0:18:19.960 --> 0:18:24.320 different internal experiences. One of them sees it as a flat, 0:18:24.400 --> 0:18:28.639 horizontal shape with spring like protrusions sticking out, and the 0:18:28.760 --> 0:18:33.080 other person sees it as a thick ribbon that's oscillating, 0:18:33.600 --> 0:18:37.520 and so on. For different cinisthetes. And beyond shapes or colors, 0:18:37.560 --> 0:18:42.600 it can trigger other notions as well, like personalities. One 0:18:42.640 --> 0:18:47.720 cinis The reports that the obo is quote profoundly emotional 0:18:47.880 --> 0:18:54.520 and thoughtful, with drawn, introspective, and prone to melancholy, while 0:18:54.640 --> 0:19:00.480 she describes the flute as quote feminine, sweet, innocent, naive 0:19:01.280 --> 0:19:04.720 the personalities of the different instruments. They're not generic, they're 0:19:05.080 --> 0:19:09.639 rich and detailed. The triggered perception can also be a 0:19:10.040 --> 0:19:13.639 physical sensation, like a physical state of your body. For 0:19:13.760 --> 0:19:17.560 one Cyniceitt that I interviewed, different chords make her feel 0:19:17.560 --> 0:19:22.240 like her body is in different positions physically, So when 0:19:22.240 --> 0:19:26.200 she feels one chord, she feels like she's standing upright 0:19:26.240 --> 0:19:30.520 with her feet on the ground, or stepping onto a 0:19:30.560 --> 0:19:36.159 stare or soaring in the sky. She happens to be 0:19:36.200 --> 0:19:40.760 a professional musician, so when she's memorizing a piece of music, 0:19:41.200 --> 0:19:45.080 it's like memorizing a series of dance moves. And there's 0:19:45.080 --> 0:19:48.440 one more form, which is likely the most common, around 0:19:48.520 --> 0:19:52.200 ten percent of the population experience it. It's when people 0:19:52.280 --> 0:19:56.000 perceive sequences like the days of the week or the 0:19:56.000 --> 0:19:59.160 months of the year, as though they have a specific 0:19:59.640 --> 0:20:04.359 space location in relation to their body, like March is 0:20:04.400 --> 0:20:06.720 off here to the left, and April is next to it, 0:20:07.160 --> 0:20:09.400 and May is a little bit higher and off next 0:20:09.440 --> 0:20:13.480 to that. For every month or a weekday or numbered 0:20:13.640 --> 0:20:18.120 things like that, they have a specific spatial location that 0:20:18.119 --> 0:20:21.560 the person can identify where it seems to them that 0:20:21.600 --> 0:20:25.360 the thing exists. It's just self evidently true to them 0:20:25.760 --> 0:20:30.120 that that member of the sequence has that particular spatial location. 0:20:30.560 --> 0:20:34.240 This form of synesthesia is not a hallucination. It's not 0:20:34.280 --> 0:20:37.440 that you actually see April right there visually. 0:20:37.800 --> 0:20:39.879 It's that it's just obviously true to you. 0:20:40.200 --> 0:20:44.240 That April would occupy that spatial location to you. It 0:20:44.240 --> 0:20:46.840 would be like if I asked you to imagine an 0:20:46.960 --> 0:20:50.520 apple five feet in front of you. So you're picturing 0:20:50.560 --> 0:20:54.080 the apple there and it's got a particular spatial location 0:20:54.280 --> 0:20:56.760 with respect to your body, and you can imagine it, 0:20:57.040 --> 0:21:00.720 but you're not actually hallucinating it. But if I ask 0:21:00.760 --> 0:21:03.439 you where that apple is, that's the spatial location that 0:21:03.480 --> 0:21:05.679 it has. A lot of people have this form of 0:21:05.720 --> 0:21:10.640 synesthesia for years, like the year nineteen seventy nine has 0:21:10.680 --> 0:21:13.600 a specific spot in space and relation to your body, 0:21:13.920 --> 0:21:17.480 as does twenty twenty one or twenty fifty seven and 0:21:17.600 --> 0:21:22.280 everything in between, and the years sit on this spatial timeline. 0:21:22.800 --> 0:21:26.280 The timeline isn't necessarily straight. It can curve or take 0:21:26.359 --> 0:21:30.359 sharp turns, and it typically moves with the passing of 0:21:30.400 --> 0:21:33.960 each year. Now, what's interesting is that for many cinisthetes, 0:21:34.440 --> 0:21:37.919 a year in the past moves behind them, say the 0:21:38.000 --> 0:21:42.280 year twenty twenty one. Why because that year has already happened, 0:21:42.640 --> 0:21:45.600 so it moves behind you, while a year like twenty 0:21:45.680 --> 0:21:49.439 forty two is often the distance ahead of you. But 0:21:49.560 --> 0:21:53.360 for other cynisthetes, it's exactly flipped. A year in the 0:21:53.440 --> 0:21:57.000 past is in front of them because they already know 0:21:57.040 --> 0:22:00.359 what happened in twenty twenty one, but year like twenty 0:22:00.359 --> 0:22:03.520 forty two hasn't happened yet, so they don't know anything 0:22:03.560 --> 0:22:07.120 about it. It's as invisible to them as an object 0:22:07.119 --> 0:22:10.800 that is behind them. I'll just note that another research 0:22:10.880 --> 0:22:16.199 group called this form of synesthesia time space synesthesia because 0:22:16.240 --> 0:22:18.680 they looked at things like weekdays and months and years 0:22:18.720 --> 0:22:21.359 and said, hey, those all have something to do with time. 0:22:22.000 --> 0:22:24.080 But I want to emphasize that this is not the 0:22:24.119 --> 0:22:29.680 correct way to understand this, because this same spatialization happens 0:22:29.720 --> 0:22:33.359 with number lines like one, two, three is over here, 0:22:33.400 --> 0:22:35.800 that it takes a right turn here for four through seven, 0:22:35.960 --> 0:22:39.200 then eight, nine, ten climb straight up, then eleven through 0:22:39.200 --> 0:22:41.399 twenty shoot off in a straight line, and then twenty 0:22:41.400 --> 0:22:43.960 one through thirty are stacked above that like that. 0:22:43.840 --> 0:22:44.360 Kind of thing. 0:22:45.160 --> 0:22:50.520 And also we find cinisthetes who have spatialization for the 0:22:50.520 --> 0:22:57.200 Indian caste system, or shoe sizes, or temperatures, or historical 0:22:57.240 --> 0:23:01.840 eras or primetime television line. So it can be anything 0:23:01.920 --> 0:23:05.520 that's a sequence, and it just so happens that time 0:23:05.680 --> 0:23:09.880 is sequential, but it's just a subset of the sequences 0:23:09.920 --> 0:23:12.600 that you might learn in life. And that's why I 0:23:12.720 --> 0:23:17.399 named this spatial sequence synesthesia in the literature, which is 0:23:17.440 --> 0:23:19.920 the name now used in the field. It turns out 0:23:20.000 --> 0:23:24.120 there are many, many forms of synesthesia, and one group 0:23:24.160 --> 0:23:27.320 has estimated that there are one hundred and fifty two 0:23:27.400 --> 0:23:31.560 different forms that have been reported. So anything you can imagine, 0:23:31.600 --> 0:23:35.280 any kind of cross blending between the senses has been 0:23:35.400 --> 0:23:37.040 reported at one point or another. 0:23:37.560 --> 0:23:40.399 Beyond the spatial sequence synesthesia. 0:23:40.000 --> 0:23:43.359 The next most common one seems to be the letters 0:23:43.440 --> 0:23:47.280 or numbers mapping on to colors, or weekdays and months 0:23:47.280 --> 0:23:51.200 to colors, or musical sounds to colors, or smells to colors, 0:23:51.280 --> 0:23:55.600 or taste to colors. Most forms of synesthesia trigger color, 0:23:55.960 --> 0:24:02.200 but we also find triggered tastes, smells, sounds, temperatures, emotions, 0:24:02.280 --> 0:24:05.520 and so on. We find essentially any kind of cross 0:24:05.600 --> 0:24:25.760 sensory blending that you can think of. It appears that 0:24:25.800 --> 0:24:30.680 synesthesia is different for every synesthet Her associations are different 0:24:30.680 --> 0:24:33.080 from hers, are different from hers. So the color that 0:24:33.119 --> 0:24:37.520 gets triggered by the letter J or the number three 0:24:37.760 --> 0:24:41.600 is a different color for everyone. Now why is this. 0:24:42.440 --> 0:24:46.159 It could be that it's just about random wiring in 0:24:46.200 --> 0:24:48.879 the brain, so the particular letter that matches up to 0:24:48.920 --> 0:24:53.080 a particular color is arbitrary. But my colleagues and I 0:24:53.080 --> 0:24:57.520 started to wonder if instead of randomness, it could be 0:24:57.560 --> 0:25:02.120 about something that you imprinted on as a young child. Now, 0:25:02.160 --> 0:25:06.240 this would give essentially the same results as randomness, because 0:25:06.560 --> 0:25:10.199 you might, as a child see an alphabet quilt that 0:25:10.240 --> 0:25:13.199 your mother made, and your mother's choices were just her 0:25:13.280 --> 0:25:17.200 random choice, or an alphabet poster that your teacher made 0:25:17.240 --> 0:25:20.359 at your preschool with some random choice, or some ad 0:25:20.400 --> 0:25:24.280 in a magazine, and the idea is that those particular 0:25:24.440 --> 0:25:30.760 letter color associations stuck for you. For most brains, the 0:25:30.800 --> 0:25:34.080 statistics wash out, which means that one day you see 0:25:34.080 --> 0:25:35.760 an A that's red, and the next day you might 0:25:35.800 --> 0:25:37.879 see an A that's blue, and the next day yellow, 0:25:37.920 --> 0:25:41.080 and so on, and so your brain learns that A 0:25:41.520 --> 0:25:45.359 is not associated with any particular color, but in a 0:25:45.520 --> 0:25:50.479 synesthetes brain, for whatever reason, perhaps the first association that 0:25:50.520 --> 0:25:55.520 they see sticks and doesn't get washed out. Now, how 0:25:55.560 --> 0:25:59.880 could you possibly test for this imprinting given that there's 0:25:59.880 --> 0:26:03.480 no easy way to know what people saw in their childhoods? 0:26:04.160 --> 0:26:08.720 And this is where science comes in. I collected detailed 0:26:08.800 --> 0:26:12.760 colored alphabets from almost seven thousand cynisthetes who had these 0:26:12.800 --> 0:26:16.920 colored alphabets, and with two colleagues at Stanford, we analyzed 0:26:17.000 --> 0:26:20.679 those colors in detail, like person number one has a 0:26:20.720 --> 0:26:22.760 red A and a purple B and a yellow C 0:26:23.040 --> 0:26:26.520 and so on, and the next person has a brown 0:26:26.600 --> 0:26:29.520 A and a crimson B and a gold C and 0:26:29.560 --> 0:26:34.160 so on. So we analyzed this huge pool of cynisthetes 0:26:34.840 --> 0:26:38.159 and we found something amazing. At least six percent of 0:26:38.200 --> 0:26:44.320 the cynisthes had approximately the same colors. A through F 0:26:44.640 --> 0:26:51.440 went red, orange, yellow, green, blue, purple, and then this 0:26:51.640 --> 0:26:56.639 same sequence of colors was repeated G through L, and 0:26:56.680 --> 0:26:59.439 then M through R and so on till the end 0:26:59.480 --> 0:27:03.680 of the alphabet. This was so weird, and even more 0:27:03.720 --> 0:27:06.520 of a clue is that we looked at people's birth 0:27:06.600 --> 0:27:09.840