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The neuroscience behind synesthesia

Richard E. Cytowic

A bald man wearing round glasses and a dark sweater poses with his hand on his chin. The background is blurred.

For most people, Tuesday is just the name of a weekday. For 1 in 23 people, Tuesday is also brown, tilted to the left, and tastes metallic. Neurologist Richard Cytowic has spent decades studying synesthesia, the phenomenon where one sense involuntarily triggers another.

Cytowic makes the case that the cross-wiring synesthetes experience is present in every human brain, just quieter.

RICHARD CYTOWIC: I'm Richard Cytowic, professor of neurology at George Washington University and an author recently of “Synesthesia: A Union of the Senses.”

- [Narrator] Understanding synesthesia.

- You know, I got into synesthesia, totally by accident. I'm a writer, so of course I love words. And I came across a book called “The Mind of a Mnemonist” by A. R. Luria, a Soviet neuropsychologist. And this memory expert had a limitless memory because he had a five fold synesthesia. He had all these hooks that he could hang things on that he was supposed to remember. And I thought, oh, what a great word. Anesthesia. No sensation. Synesthesia. Joint sensation. So I filed it away in the back of my mind. All right, fast forward. I have a new neighbor who teaches lighting design at the school of the arts and he invited me to dinner. And he says, “Oh, it will be a few more minutes. There's not enough points on the chicken.” Now, his friends asked what he was smoking, and Michael Watson, who was the man who tasted shapes, looked at me beet red and said, “Oh my God, you're neurologist. Maybe you'll understand. When I taste something. I also feel it on my face and in my hands with an intense flavor, a feeling sweeps down my arm and I feel weight, shape and texture as if I'm actually grasping something.” And I nodded and said, “Oh, you have synesthesia.” I mean, I was just trying to be polite. And he, the look on his face. He said, “You mean there's a name for what I do?” And then I thought, how could he not know? And that's when the light bulb went off, that this could be something really interesting because it's an elevated function. A hyper connection among the senses. And, there is a small category of neurological phenomenon like that. So I told my my, colleagues, fellow residents about it, and they immediately said, well, what's this CAT scan show? And I said, no, he doesn't have a hole in his head. He's got something extra. This is an elevated function. And they said, man, you stay away from this. It is too weird, to New Age. It is going to ruin your career. Well, fast forward, it didn't. Obviously. Basically, I reintroduced it to modern science. It has, it had been very popular at the turn of the century, all the way up into the 1930s, when behaviorism came around and behaviorism said subjective experience was taboo. So that meant memory, language, certainly synesthesia was, you know, like like bogus. You couldn't do it. But then I said, well, I'll show you. I was intrigued by it first, I first thought it was because of my father, who was a physician, a magician, an archer, a raconteur. He was larger than life personality who introduced me to the unusual and the offbeat. And I thought, well, that's the reason that this appealed to me. And then it was years later that finally another light went off and I thought, oh, no, it's because I'm gay. So as a ten year old in New Jersey, my father's medical profession said that I was sick. The state said that I was a criminal. And the church said that I was doomed to hell. And I hadn't done anything. I was ten years old, and I thought, these people don't know what they're talking about. They don't know me. How dare they say that I shouldn't exist? And so when I heard people say, well, synesthesia is bogus. It can't exist. It can't possibly be real. I thought, oh, man, I've heard this before. And that's what prompted me to look into it. I mean, subjective experience is difficult to study. It's messy experimentally, but it can be done. It's tedious, but it can be done. And so I did it. My first papers came out in 1989, and then my first book about synesthesia also came out in 1989 by Springer-Verlag. So, of course, I had a lot of exposure in the press and on radio and all that. And so I remember one woman who now is the head of the American Synesthesia Association. She's an artist. She heard me on the WNYU’s book talk. And she, you know, she dropped your brush and she just cried and said, oh, my God, I can't believe somebody is talking about this. I can't believe it's real. I've had grown men call me on the phone in tears saying, nobody ever believed me. You made me feel heard for the first time in my life. So it's from a philosophical point of view. It's qualia, which is, let's say red is a qualia of color, and one qualia becomes linked to another. So, for example, suppose I show you a matrix of fives within which I've hid a geometric figure that's made up of twos. Now you and I will take a while to search and find that hidden figure. But for synesthetes, who see twos as differently colored than fives, a shape will instantly pop out without any effort on their part. The same thing for music. Days of the week are colored. Time units are color. I mean, it's involuntary for one thing. It happens to you. You can't. You can't make it happen. So in that sense, it's like perfect pitch, which is another kind of sensory, phenomenon. It's apparent at a very, very young age. You there's nothing you can do to make it happen. The associations are the same over the course of a lifetime. I read, one woman wrote, she said, well, I'm 65 years now, and the colors are as bright as ever, you know, when I, when I was a teenager. But for others, like take Sean Day, who's head of the International Synesthesia Association, who's got colored taste, among other things, he said, yeah, he likes blue foods, he says. But, you know, after after living through this all my life, you get used to the wow factor, so it's not so much. It's still there, but it's not so much of a wow. It's like when you first open the refrigerator and the light goes on. Wow. What a surprise that is. But, you know, every time I open the refrigerator now, the light coming on doesn't faze me in the least, because I know that's what's going to happen. The other thing is that synesthesia is almost always a one way street. So sound goes to sight, but not the other way. So music, environmental sounds, the clattering of dishes, a dog's bark, the sound of my voice. Those produce photisms which are colored shapes that arise and they scintillate or move around a bit, sort of like fireworks. And they keep up as long as the stimulus keeps up. So let's say the sound of my voice and you're seeing these puffs of steam and sparkle and it's geometric shapes. And when I stop talking, then they fade away. There's a handful of exceptions in which it does go by directional. So which, sight activates sound. So Liddell, who's profoundly hard of hearing, has it going both ways. So when he sees, like, those red lights and those towers that were, you know, warn airplanes to stay away. He says he has what he calls photonic hearing. And that red light flashing causes this this sound that he hears. And there's another woman who's studied extensively. She, Julie Roxburgh, she's a music teacher in, in rural England. And she has been studied extensively to show that her synesthesia goes in both directions. Now, she very bravely agreed to go into Piccadilly Circus at night, and she's there and she's saying, okay, I'm now entering the circle, and this, this harsh green light is flashing and it's making this terrible sound. And then I've got the motion of the traffic and the people around me. And then this other sign is flashing, and I'm starting to feel a little nauseous and and lightheaded. And if I don't get out of here soon, I think I'm going to faint. So basically, she had this sensory overload from the sights and sounds and movements in Piccadilly Circus in her bidirectional synesthesia. Some have it more than others. So, for some, it's simply the only association of color and numbers with with with one another with others, there's more of a wow factor. So they talk about a street name being gorgeous or a certain, food being, you know, unbelievable. The most mundane stimuli they describe in these highly affective laden terms. And I call that the wow factor. Synesthesia turns out to be fairly common, much more common than I expected when I began all this work. It occurs in 4% of the population worldwide. It doesn't matter what your nationality or content continent is. And so that's about 1 in 23 people inherit the gene. And I'll use the singular gene, although it's actually several genes are involved, so far as we know. Synesthesia is transmitted as an autosomal dominant trait that is either parent either gender parent can transmit it to their offspring, and they they have a 50% chance of transmitting that gene as an autosomal dominant. And initially they're turned out to be, too many women compared to men. And at first when it got up to 2.5, then we came up with, variations in how that could be, which is autosomal dominance with lethality, meaning that half of the female, half of their male embryos would be would be lethal and not survive. But then the ratio in all the way up to 6 to 1, I was like, oh my God, what do we do? How, we're not going to be like, explain this by genetics. But then Julia Sinner in Edinburgh did a study, at the Kensington Science Museum in London, where they asked people as they walked in the door, do you see colors with letters and numbers and all that? And was they did it random population like that? It turned out that it was basically 1 to 1. And the answer of why so many women initially was that women were much more willing to talk about unusual experiences, including having synesthetic orgasms, which they loved very much. You asked men this question and they hem and haw and they shuffle their feet. And so, but eventually, you know, men became around and the more men were around and talked about the experience, the more men were likely, willing to talk about them. There are some, musicians who refused to, you know, be studied. They won't talk about it, because they think they're going to be made fun of and, you know, they're they're very rigid in their resistance. Billy Joel, on the other hand, you know, he talks about his colors and his music. So 1 in 23 people had the genes, but because it's not expressed with 100% fidelity, a smaller number has then some kind of overt or outward synesthesia. And that comes about 1 in 90. And the most common forms are anything that has a sequence to it is going to have a color associated with it. So three days of the week for example, integers, other kinds of numbers, temperature, scales, shoe sizes. They can be anything that has a sequence to it. That's called grapheme synesthesia, grapheme being the written elements of of speech. And then there's spatial sequence synesthesia. So anything that has a sequence. So Monday to Wednesday, Thursday Friday takes on like a spatial map in three dimensions in front of you. So when you say where's the November. Oh it's down here. It's brown by my knee. And when I look at November then that opens up and I have a calendar I can put in all these dates that I remember. So when I need to look at like, okay, what am I doing, you know, next week? Your mind goes, your attention goes to that space, and you look up the data that you put there. So colored music is quite interesting because people say, I see music and, well, what is it? For some people it's the tone, an absolute tone. Joseph Long, a Scottish pianist who was blind, by the way, said he was astonished when he went to do music lessons and his his teacher's “A” was totally different than his “A.” Synesthesia is fairly common in blind individuals. Why might that be? Well, there V1 the primary visual cortex, is not getting a signal from the retina, so it's just sitting there unused. And if it says anything, it says, well, everything is black. So other areas of the brain can then encroach on this unused area. And then they, they there you've got synesthesia where the visual cortex is now responding to, tones or touches or other kinds of stimulation tastes, smells, whatever. Now, colored music, is interesting because there's some famous composers who are synesthetic. Olivier Messiaen for example, the French composer, he's been interviewed many times about this, and for him what it turns out to be is the, the spatial is the chord structure, the distance between notes and a certain chord and, Messiaen said that his, the colors of each chord structure are you could predict what the color was going to be, of the piece. So, for example, he was commissioned to write a piece for the US, Centennial and, he said, I went in Bryce Canyon and my eye went up to canyon wall and the music wrote itself. Color is very prominent perhaps because vision, it, accounts for about 85% of the inputs to the brain. So it's got its network goes all over the place, including the brain stem, let alone the cortex and the limbic system and the thalamus and whatnot. The other thing is that synesthesia is not just color. For example, in phoneme synesthesia. Phonemes are the spoken elements of speech. The sound of my voice might be something that people, not only see, but also they they think they tasted or feel it as a physical touch. Or having a certain taste and then feeling a warm sensation rising up from your from your belly. Hearing, a word like college is a certain color and shape, but so is sausage and message and other words, with the “ige” sounding. So it's the “ige” phoneme that's triggering the synesthesia. So when you have enough of these kind of people, you can then sort of predict what the taste is going to be, for example, we did this with James Wannerton in England who has this taste synesthesia. He was in the documentary called “Derek Tastes of Earwax.” We were able to give him a word and predict what it was, but he couldn't do that. He couldn't make a mnemonic association that would be very easy for the rest of us. He had to actually hear the word. So that's sort of interesting is that you don't have a, you don't have a mental picture of this. You've got to have a perceptual experience of it. So that's sort of the experience of synesthesia like. The other thing is that synesthetes have extraordinary memories. When you test them on a traditional memory quotion scale, they perform very close to the top of the range. And then the odd thing is they'll say things like, well, I don't remember her name. It was a green name. Let's see, green. D’s are green. It was the Doris, Denby, Dorothy... Dorothy. Oh, yes, it was Dorothy. So for you and me, like going through the mental gymnastics of how does that help you remember that her name is Dorothy, you know, it's almost, it has a logic of its own, but it works. So I already talked about you know, that they have they have excellent memories, because they have all these, these extra hooks to hang things on. Some things they're really poor at, for example, their sense of direction tends to be really bad. But for example, they might cook. Michael Watson cooked according to how he wanted a certain dish to feel, never relied on a recipe, was always cooking by feeling. It's also, synesthetes tend to be more creative than than other people, that is, as a group, they, they are more creative. And this is why I said the synesthesia gene is a gene for metaphor. So they've they play a musical instrument, they speak a foreign language or two. They engage in, sculpture or archery or a knitting or some other creative, endeavor, much more often than the general population does. So, for example, Kandinsky, the artist, is quite interesting. He had four different kinds of synesthesia, which involve taste and smell and touch. Like a midnight blue, he called that, a soft, angelic color, like stroking your hand across velvet. Orange was the prickly color, he said. It's hard to predict. So he never really sort of gave her a key for what he might, to which we could, like, translate back the other way and predict what, what these colors would be. But there they are. And this is what he said about it all his life. And, they were they were just there. Another one would be Vladimir Nabokov, the writer. He had colored hearing quite intensely. And he wrote about this in his novel “Speak, Memory.” And so, for him, the like the, the alphabet had not only, certain colors like I described the, you know, the black, the black was like the back of a hand hand mirror and had a certain sheen to it. Others had a certain taste to them. So that was his kind of synesthesia. And it ran in families. He wrote about “Portrait of My Mother,” who's got the same kind of synesthesia as he does. And then his son Dimitri, who wrote the afterword to “Wednesday is Indigo Blue.” But the families, each had their own letter associations were different from one another. So the mother’s and Vladimir's and the son’s were all different, even though they stayed constant throughout their life. So where do synesthetes see these things or experience these things? Is it in front of them on a screen? Is it in their mind's eye? And the answer is yes to both. There are what are called projector synesthetes, for example, people who see colored letters and numbers. Where do they see it? They see it in Technicolor on the page overlying the black, black and white printed letters. Then there are associative synesthetes. So if you say what color is “f”? Well, they they get an overall sense of pink, or else they see it in their mind eye or somehow they know. One woman says, “Well, I know it's two because it's white.” And I said, so there's something about two-ness and whiteness that is similar in her mind. Now to the rest of us, there's there's nothing in common about them. But to her there's almost an identity among them. And that really speaks to metaphor, which is seeing the, the similar in the dissimilar. So there is something about, two and whiteness for this woman that is identical. It's important to note that, synesthesia is not universal across people, so that for one person, when they have a certain letter or number or whatever, a certain color, that for another synesthesia, it'll be something totally different. Julia Simner, in Scotland, asked a bunch of synesthetes, you know what color is five? Five is green. But it wasn't just green, it was a particular shade of green. And so she ended up with a table of 63 different names for, you know, lime green, pea green, fog green, bright green, metallic green. I mean, Sir Francis Galton noticed this over 120 years ago is that when synesthetes say that a certain stimulus is a certain color, they mean it very specific color, which they struggle to articulate. And again, why is this? Well that's because, non optical inputs are going into the visual cortex. And so they're triggering these kinds of very specific colors colors that you can't see in the real world. I mean there's there's a there's a colorblind synesthetes, he has a M-cone deficiency. And that makes it hard or impossible for him to distinguish between blues and purples. But he says he speaks of seeing his martian colors, that is colors that he's incapable of seeing in the real world, and yet that are activated because his visual cortex is being activated by non optic means. The big question is, you know, are there cross connections among the senses in synesthetes and the answer is yes, of course there are. The question is how much crosstalk is there? Because crosstalk is present in all of our brains. There's a wonderful experiment where you, where you take volunteers and you blindfold them for two days, and after that you're doing evoke responses. You have electrodes on the back of their head, and you're recording the responses in V1, the primary visual cortex, and all of a sudden V1, which is now been blocked off from any kind of visual input, suddenly responds to sounds, to touches, to aromas, to tastes. Now, two days is too short of a time for new synapses to grow from these other sensory areas into V1. So the conclusion is that visual connections must have been already there, but unused as long as vision was inputting a signal. And to prove that that’s so, you take the blindfolds off and just two hours later, V1 reverts to responding only to visual input. Sight and sound are so tightly coupled that even bad ventriloquists convince us that the dummies is doing the talking. Cinema is another illusion where we are convinced that the dialog is coming from the actress mouths on screens and not on the speakers around us. Dance is another kind of synesthesia, where the we're we're impelled to move to the beat of the music, and move our body in this kinetic way, in response to the to the music. Also, you know, taste and vision go together. So, a darkly tinted liquid, taste and smell stronger than a pale liquid. So most things that we think of as tastes are actually smell that we taste in the rectal pharyngeal area. That is the back of our nose. So I can put a close pin on your nose and blindfold you and give you a piece of onion and say to taste this apple. And you might think, oh, this is onion. You'll think that you can't distinguish any taste to it at all. So I think one of the things synesthesia has shown us is it's not some weird outlier. It's like the foundation. Common misconceptions. Well, for one, that it's bogus, that they're making it up. They want attention, or else they're, artists and everybody knows that artists are crazy. Or they're having residual hallucinations from too much marijuana or LSD use. I mean, whenever you try to show that synesthesia is real, you get one excuse after another about why it can't be. And yet every one of those is very easily shot down. So it's not bogus. It's a real perceptual phenomenon. You do not need million dollar machines to prove that this is so. You show it by paper and pencil tests. So you ask them, okay, what is X? Know what is, what is, what is, what color is R and what gender is it? What personality is it? Over a year later, you do it again without giving them any warning that you're going to ask them again, and you ask them again and they give you, give you the same answer. Now people have tried to say that, well, these are learned associations, but you can't learn synesthesia. People have tried and you ask them, okay, we're going to do this. And now I'm going to ask you again. In one week you give them the warning. So you got to really remember what you're telling me about these color associations. And when you ask them again a week later, they they perform below chance level because they can't remember what they said because they're not having a synesthesia that's telling them what the answer is in front of them. One of the prime, problems with the did disbelief that I faced, my neurology colleagues saying, oh, this cannot possibly be a real brain phenomenon is that, they were they were demanding a third person technical explanation for a first person experience. And so you have to go to the first person, and then you have to go to the second person and sort of query the experience of what is it like. So for Michael Watson okay. So he takes shape okay. All right. How do we prove that. Because at the time we didn't have million dollar machines. I used a method called radioactive xenon 133, which is very early method of brain imaging. So I thought, okay, he sees shapes. So we do a pilot experiment, and I come out with a tray full of all these different flavors in a liquid form in syringes, and I squirt them in his mouth and he tells me what they are. And so he showed absolute effects where some shapes were, very much on the pointed dimension, and others were, if you're giving him something that was relatively sour, then it would be some other shape. So it all depended on the context of these 13 different flavors that we were giving him. So fast forward to more sophisticated imaging. We now have functional magnetic resonance imaging, where if you say, okay, you see colors in response to spoken words and you put them in that scanner and lo and behold, V4 the color in the human color area activates. So you can show what you know by theory. So basically just proving what theory says should happen. And so for people who insist on pictures of the brain, you know, we showed them that and that shut them up from saying that, okay, this is fake because there was the picture that they wanted. It's not fake. You've got your proof. I don't know what the next big leap is going to be from where we currently are in our state of consciousness. I would say if you, you know, you can ask synesthetes to interbreed with one another and produce more synesthetes and then we'll see what happens. Interestingly, though, is like is is there's a number of groups. There's five groups around the world that are tracking down the synesthesia genes to see what chromosome marker they lie on and they're getting better and better at this. David Eagleman was so funny when he started out. He said he was dealing with spatial sequence synesthesia, you know, the number forms. And he said, “Oh, it'll be just a couple of months. We'll we'll get the genes and knock it out and have an answer.” Well, that was decades ago. And he still hasn't gotten an answer, but we are getting better at it. And now once we have these markers, okay, we know that, you know, on chromosome four, on chromosome 16, these certain markers. Then we go out and we take a huge sample of people at random, let's say 1000 or 5000 people and we do their gene markers and say, who's got these markers? And okay, you've got you got the synesthesia gene markers, but you're not synesthesia. You're not synesthetic. So what do you like? Well, what what are these people like? You know, are they geniuses? Are they psychopaths? We don't know. We just have to do the work. But it's interesting, I think, is to be able to go in reverse and and say, here's the data, here are the genetic markers for synesthesia and these people have them. What are they like? Maybe we could teach that group synesthesia. I don't know, I don't I'm I'm doubtful, but I mean anything is possible. One of the things I love about school children doing book reports and things like that is that they say, oh, Joanne sees the world differently than the way I do. And yet she's still Joanne. She's my playmate, my classmate. And so this lightbulb goes off that, oh my God, other people know things too. My way isn't the one and only way. It's not the right way. And so it opens up people to being open to seeing that there are other kinds of points of view in the world, and being able maybe to do what I do in terms of resilience is letting go of needing to have my point of view always be right. You know? You know, I let go of that and, you know, surprising things happen. I learned something that I didn't think I would learn if I had clutched on to what I thought was the only real way of seeing things. You need to understand them. That that's the more important thing is not trying to correct them or argue with them, but trying to understand what it's like and nothing is better. Then tell me or tell me more.

For most people, Tuesday is just the name of a weekday. For 1 in 23 people, Tuesday is also brown, tilted to the left, and tastes metallic. Neurologist Richard Cytowic has spent decades studying synesthesia, the phenomenon where one sense involuntarily triggers another.

Cytowic makes the case that the cross-wiring synesthetes experience is present in every human brain, just quieter.

RICHARD CYTOWIC: I'm Richard Cytowic, professor of neurology at George Washington University and an author recently of “Synesthesia: A Union of the Senses.”

- [Narrator] Understanding synesthesia.

- You know, I got into synesthesia, totally by accident. I'm a writer, so of course I love words. And I came across a book called “The Mind of a Mnemonist” by A. R. Luria, a Soviet neuropsychologist. And this memory expert had a limitless memory because he had a five fold synesthesia. He had all these hooks that he could hang things on that he was supposed to remember. And I thought, oh, what a great word. Anesthesia. No sensation. Synesthesia. Joint sensation. So I filed it away in the back of my mind. All right, fast forward. I have a new neighbor who teaches lighting design at the school of the arts and he invited me to dinner. And he says, “Oh, it will be a few more minutes. There's not enough points on the chicken.” Now, his friends asked what he was smoking, and Michael Watson, who was the man who tasted shapes, looked at me beet red and said, “Oh my God, you're neurologist. Maybe you'll understand. When I taste something. I also feel it on my face and in my hands with an intense flavor, a feeling sweeps down my arm and I feel weight, shape and texture as if I'm actually grasping something.” And I nodded and said, “Oh, you have synesthesia.” I mean, I was just trying to be polite. And he, the look on his face. He said, “You mean there's a name for what I do?” And then I thought, how could he not know? And that's when the light bulb went off, that this could be something really interesting because it's an elevated function. A hyper connection among the senses. And, there is a small category of neurological phenomenon like that. So I told my my, colleagues, fellow residents about it, and they immediately said, well, what's this CAT scan show? And I said, no, he doesn't have a hole in his head. He's got something extra. This is an elevated function. And they said, man, you stay away from this. It is too weird, to New Age. It is going to ruin your career. Well, fast forward, it didn't. Obviously. Basically, I reintroduced it to modern science. It has, it had been very popular at the turn of the century, all the way up into the 1930s, when behaviorism came around and behaviorism said subjective experience was taboo. So that meant memory, language, certainly synesthesia was, you know, like like bogus. You couldn't do it. But then I said, well, I'll show you. I was intrigued by it first, I first thought it was because of my father, who was a physician, a magician, an archer, a raconteur. He was larger than life personality who introduced me to the unusual and the offbeat. And I thought, well, that's the reason that this appealed to me. And then it was years later that finally another light went off and I thought, oh, no, it's because I'm gay. So as a ten year old in New Jersey, my father's medical profession said that I was sick. The state said that I was a criminal. And the church said that I was doomed to hell. And I hadn't done anything. I was ten years old, and I thought, these people don't know what they're talking about. They don't know me. How dare they say that I shouldn't exist? And so when I heard people say, well, synesthesia is bogus. It can't exist. It can't possibly be real. I thought, oh, man, I've heard this before. And that's what prompted me to look into it. I mean, subjective experience is difficult to study. It's messy experimentally, but it can be done. It's tedious, but it can be done. And so I did it. My first papers came out in 1989, and then my first book about synesthesia also came out in 1989 by Springer-Verlag. So, of course, I had a lot of exposure in the press and on radio and all that. And so I remember one woman who now is the head of the American Synesthesia Association. She's an artist. She heard me on the WNYU’s book talk. And she, you know, she dropped your brush and she just cried and said, oh, my God, I can't believe somebody is talking about this. I can't believe it's real. I've had grown men call me on the phone in tears saying, nobody ever believed me. You made me feel heard for the first time in my life. So it's from a philosophical point of view. It's qualia, which is, let's say red is a qualia of color, and one qualia becomes linked to another. So, for example, suppose I show you a matrix of fives within which I've hid a geometric figure that's made up of twos. Now you and I will take a while to search and find that hidden figure. But for synesthetes, who see twos as differently colored than fives, a shape will instantly pop out without any effort on their part. The same thing for music. Days of the week are colored. Time units are color. I mean, it's involuntary for one thing. It happens to you. You can't. You can't make it happen. So in that sense, it's like perfect pitch, which is another kind of sensory, phenomenon. It's apparent at a very, very young age. You there's nothing you can do to make it happen. The associations are the same over the course of a lifetime. I read, one woman wrote, she said, well, I'm 65 years now, and the colors are as bright as ever, you know, when I, when I was a teenager. But for others, like take Sean Day, who's head of the International Synesthesia Association, who's got colored taste, among other things, he said, yeah, he likes blue foods, he says. But, you know, after after living through this all my life, you get used to the wow factor, so it's not so much. It's still there, but it's not so much of a wow. It's like when you first open the refrigerator and the light goes on. Wow. What a surprise that is. But, you know, every time I open the refrigerator now, the light coming on doesn't faze me in the least, because I know that's what's going to happen. The other thing is that synesthesia is almost always a one way street. So sound goes to sight, but not the other way. So music, environmental sounds, the clattering of dishes, a dog's bark, the sound of my voice. Those produce photisms which are colored shapes that arise and they scintillate or move around a bit, sort of like fireworks. And they keep up as long as the stimulus keeps up. So let's say the sound of my voice and you're seeing these puffs of steam and sparkle and it's geometric shapes. And when I stop talking, then they fade away. There's a handful of exceptions in which it does go by directional. So which, sight activates sound. So Liddell, who's profoundly hard of hearing, has it going both ways. So when he sees, like, those red lights and those towers that were, you know, warn airplanes to stay away. He says he has what he calls photonic hearing. And that red light flashing causes this this sound that he hears. And there's another woman who's studied extensively. She, Julie Roxburgh, she's a music teacher in, in rural England. And she has been studied extensively to show that her synesthesia goes in both directions. Now, she very bravely agreed to go into Piccadilly Circus at night, and she's there and she's saying, okay, I'm now entering the circle, and this, this harsh green light is flashing and it's making this terrible sound. And then I've got the motion of the traffic and the people around me. And then this other sign is flashing, and I'm starting to feel a little nauseous and and lightheaded. And if I don't get out of here soon, I think I'm going to faint. So basically, she had this sensory overload from the sights and sounds and movements in Piccadilly Circus in her bidirectional synesthesia. Some have it more than others. So, for some, it's simply the only association of color and numbers with with with one another with others, there's more of a wow factor. So they talk about a street name being gorgeous or a certain, food being, you know, unbelievable. The most mundane stimuli they describe in these highly affective laden terms. And I call that the wow factor. Synesthesia turns out to be fairly common, much more common than I expected when I began all this work. It occurs in 4% of the population worldwide. It doesn't matter what your nationality or content continent is. And so that's about 1 in 23 people inherit the gene. And I'll use the singular gene, although it's actually several genes are involved, so far as we know. Synesthesia is transmitted as an autosomal dominant trait that is either parent either gender parent can transmit it to their offspring, and they they have a 50% chance of transmitting that gene as an autosomal dominant. And initially they're turned out to be, too many women compared to men. And at first when it got up to 2.5, then we came up with, variations in how that could be, which is autosomal dominance with lethality, meaning that half of the female, half of their male embryos would be would be lethal and not survive. But then the ratio in all the way up to 6 to 1, I was like, oh my God, what do we do? How, we're not going to be like, explain this by genetics. But then Julia Sinner in Edinburgh did a study, at the Kensington Science Museum in London, where they asked people as they walked in the door, do you see colors with letters and numbers and all that? And was they did it random population like that? It turned out that it was basically 1 to 1. And the answer of why so many women initially was that women were much more willing to talk about unusual experiences, including having synesthetic orgasms, which they loved very much. You asked men this question and they hem and haw and they shuffle their feet. And so, but eventually, you know, men became around and the more men were around and talked about the experience, the more men were likely, willing to talk about them. There are some, musicians who refused to, you know, be studied. They won't talk about it, because they think they're going to be made fun of and, you know, they're they're very rigid in their resistance. Billy Joel, on the other hand, you know, he talks about his colors and his music. So 1 in 23 people had the genes, but because it's not expressed with 100% fidelity, a smaller number has then some kind of overt or outward synesthesia. And that comes about 1 in 90. And the most common forms are anything that has a sequence to it is going to have a color associated with it. So three days of the week for example, integers, other kinds of numbers, temperature, scales, shoe sizes. They can be anything that has a sequence to it. That's called grapheme synesthesia, grapheme being the written elements of of speech. And then there's spatial sequence synesthesia. So anything that has a sequence. So Monday to Wednesday, Thursday Friday takes on like a spatial map in three dimensions in front of you. So when you say where's the November. Oh it's down here. It's brown by my knee. And when I look at November then that opens up and I have a calendar I can put in all these dates that I remember. So when I need to look at like, okay, what am I doing, you know, next week? Your mind goes, your attention goes to that space, and you look up the data that you put there. So colored music is quite interesting because people say, I see music and, well, what is it? For some people it's the tone, an absolute tone. Joseph Long, a Scottish pianist who was blind, by the way, said he was astonished when he went to do music lessons and his his teacher's “A” was totally different than his “A.” Synesthesia is fairly common in blind individuals. Why might that be? Well, there V1 the primary visual cortex, is not getting a signal from the retina, so it's just sitting there unused. And if it says anything, it says, well, everything is black. So other areas of the brain can then encroach on this unused area. And then they, they there you've got synesthesia where the visual cortex is now responding to, tones or touches or other kinds of stimulation tastes, smells, whatever. Now, colored music, is interesting because there's some famous composers who are synesthetic. Olivier Messiaen for example, the French composer, he's been interviewed many times about this, and for him what it turns out to be is the, the spatial is the chord structure, the distance between notes and a certain chord and, Messiaen said that his, the colors of each chord structure are you could predict what the color was going to be, of the piece. So, for example, he was commissioned to write a piece for the US, Centennial and, he said, I went in Bryce Canyon and my eye went up to canyon wall and the music wrote itself. Color is very prominent perhaps because vision, it, accounts for about 85% of the inputs to the brain. So it's got its network goes all over the place, including the brain stem, let alone the cortex and the limbic system and the thalamus and whatnot. The other thing is that synesthesia is not just color. For example, in phoneme synesthesia. Phonemes are the spoken elements of speech. The sound of my voice might be something that people, not only see, but also they they think they tasted or feel it as a physical touch. Or having a certain taste and then feeling a warm sensation rising up from your from your belly. Hearing, a word like college is a certain color and shape, but so is sausage and message and other words, with the “ige” sounding. So it's the “ige” phoneme that's triggering the synesthesia. So when you have enough of these kind of people, you can then sort of predict what the taste is going to be, for example, we did this with James Wannerton in England who has this taste synesthesia. He was in the documentary called “Derek Tastes of Earwax.” We were able to give him a word and predict what it was, but he couldn't do that. He couldn't make a mnemonic association that would be very easy for the rest of us. He had to actually hear the word. So that's sort of interesting is that you don't have a, you don't have a mental picture of this. You've got to have a perceptual experience of it. So that's sort of the experience of synesthesia like. The other thing is that synesthetes have extraordinary memories. When you test them on a traditional memory quotion scale, they perform very close to the top of the range. And then the odd thing is they'll say things like, well, I don't remember her name. It was a green name. Let's see, green. D’s are green. It was the Doris, Denby, Dorothy... Dorothy. Oh, yes, it was Dorothy. So for you and me, like going through the mental gymnastics of how does that help you remember that her name is Dorothy, you know, it's almost, it has a logic of its own, but it works. So I already talked about you know, that they have they have excellent memories, because they have all these, these extra hooks to hang things on. Some things they're really poor at, for example, their sense of direction tends to be really bad. But for example, they might cook. Michael Watson cooked according to how he wanted a certain dish to feel, never relied on a recipe, was always cooking by feeling. It's also, synesthetes tend to be more creative than than other people, that is, as a group, they, they are more creative. And this is why I said the synesthesia gene is a gene for metaphor. So they've they play a musical instrument, they speak a foreign language or two. They engage in, sculpture or archery or a knitting or some other creative, endeavor, much more often than the general population does. So, for example, Kandinsky, the artist, is quite interesting. He had four different kinds of synesthesia, which involve taste and smell and touch. Like a midnight blue, he called that, a soft, angelic color, like stroking your hand across velvet. Orange was the prickly color, he said. It's hard to predict. So he never really sort of gave her a key for what he might, to which we could, like, translate back the other way and predict what, what these colors would be. But there they are. And this is what he said about it all his life. And, they were they were just there. Another one would be Vladimir Nabokov, the writer. He had colored hearing quite intensely. And he wrote about this in his novel “Speak, Memory.” And so, for him, the like the, the alphabet had not only, certain colors like I described the, you know, the black, the black was like the back of a hand hand mirror and had a certain sheen to it. Others had a certain taste to them. So that was his kind of synesthesia. And it ran in families. He wrote about “Portrait of My Mother,” who's got the same kind of synesthesia as he does. And then his son Dimitri, who wrote the afterword to “Wednesday is Indigo Blue.” But the families, each had their own letter associations were different from one another. So the mother’s and Vladimir's and the son’s were all different, even though they stayed constant throughout their life. So where do synesthetes see these things or experience these things? Is it in front of them on a screen? Is it in their mind's eye? And the answer is yes to both. There are what are called projector synesthetes, for example, people who see colored letters and numbers. Where do they see it? They see it in Technicolor on the page overlying the black, black and white printed letters. Then there are associative synesthetes. So if you say what color is “f”? Well, they they get an overall sense of pink, or else they see it in their mind eye or somehow they know. One woman says, “Well, I know it's two because it's white.” And I said, so there's something about two-ness and whiteness that is similar in her mind. Now to the rest of us, there's there's nothing in common about them. But to her there's almost an identity among them. And that really speaks to metaphor, which is seeing the, the similar in the dissimilar. So there is something about, two and whiteness for this woman that is identical. It's important to note that, synesthesia is not universal across people, so that for one person, when they have a certain letter or number or whatever, a certain color, that for another synesthesia, it'll be something totally different. Julia Simner, in Scotland, asked a bunch of synesthetes, you know what color is five? Five is green. But it wasn't just green, it was a particular shade of green. And so she ended up with a table of 63 different names for, you know, lime green, pea green, fog green, bright green, metallic green. I mean, Sir Francis Galton noticed this over 120 years ago is that when synesthetes say that a certain stimulus is a certain color, they mean it very specific color, which they struggle to articulate. And again, why is this? Well that's because, non optical inputs are going into the visual cortex. And so they're triggering these kinds of very specific colors colors that you can't see in the real world. I mean there's there's a there's a colorblind synesthetes, he has a M-cone deficiency. And that makes it hard or impossible for him to distinguish between blues and purples. But he says he speaks of seeing his martian colors, that is colors that he's incapable of seeing in the real world, and yet that are activated because his visual cortex is being activated by non optic means. The big question is, you know, are there cross connections among the senses in synesthetes and the answer is yes, of course there are. The question is how much crosstalk is there? Because crosstalk is present in all of our brains. There's a wonderful experiment where you, where you take volunteers and you blindfold them for two days, and after that you're doing evoke responses. You have electrodes on the back of their head, and you're recording the responses in V1, the primary visual cortex, and all of a sudden V1, which is now been blocked off from any kind of visual input, suddenly responds to sounds, to touches, to aromas, to tastes. Now, two days is too short of a time for new synapses to grow from these other sensory areas into V1. So the conclusion is that visual connections must have been already there, but unused as long as vision was inputting a signal. And to prove that that’s so, you take the blindfolds off and just two hours later, V1 reverts to responding only to visual input. Sight and sound are so tightly coupled that even bad ventriloquists convince us that the dummies is doing the talking. Cinema is another illusion where we are convinced that the dialog is coming from the actress mouths on screens and not on the speakers around us. Dance is another kind of synesthesia, where the we're we're impelled to move to the beat of the music, and move our body in this kinetic way, in response to the to the music. Also, you know, taste and vision go together. So, a darkly tinted liquid, taste and smell stronger than a pale liquid. So most things that we think of as tastes are actually smell that we taste in the rectal pharyngeal area. That is the back of our nose. So I can put a close pin on your nose and blindfold you and give you a piece of onion and say to taste this apple. And you might think, oh, this is onion. You'll think that you can't distinguish any taste to it at all. So I think one of the things synesthesia has shown us is it's not some weird outlier. It's like the foundation. Common misconceptions. Well, for one, that it's bogus, that they're making it up. They want attention, or else they're, artists and everybody knows that artists are crazy. Or they're having residual hallucinations from too much marijuana or LSD use. I mean, whenever you try to show that synesthesia is real, you get one excuse after another about why it can't be. And yet every one of those is very easily shot down. So it's not bogus. It's a real perceptual phenomenon. You do not need million dollar machines to prove that this is so. You show it by paper and pencil tests. So you ask them, okay, what is X? Know what is, what is, what is, what color is R and what gender is it? What personality is it? Over a year later, you do it again without giving them any warning that you're going to ask them again, and you ask them again and they give you, give you the same answer. Now people have tried to say that, well, these are learned associations, but you can't learn synesthesia. People have tried and you ask them, okay, we're going to do this. And now I'm going to ask you again. In one week you give them the warning. So you got to really remember what you're telling me about these color associations. And when you ask them again a week later, they they perform below chance level because they can't remember what they said because they're not having a synesthesia that's telling them what the answer is in front of them. One of the prime, problems with the did disbelief that I faced, my neurology colleagues saying, oh, this cannot possibly be a real brain phenomenon is that, they were they were demanding a third person technical explanation for a first person experience. And so you have to go to the first person, and then you have to go to the second person and sort of query the experience of what is it like. So for Michael Watson okay. So he takes shape okay. All right. How do we prove that. Because at the time we didn't have million dollar machines. I used a method called radioactive xenon 133, which is very early method of brain imaging. So I thought, okay, he sees shapes. So we do a pilot experiment, and I come out with a tray full of all these different flavors in a liquid form in syringes, and I squirt them in his mouth and he tells me what they are. And so he showed absolute effects where some shapes were, very much on the pointed dimension, and others were, if you're giving him something that was relatively sour, then it would be some other shape. So it all depended on the context of these 13 different flavors that we were giving him. So fast forward to more sophisticated imaging. We now have functional magnetic resonance imaging, where if you say, okay, you see colors in response to spoken words and you put them in that scanner and lo and behold, V4 the color in the human color area activates. So you can show what you know by theory. So basically just proving what theory says should happen. And so for people who insist on pictures of the brain, you know, we showed them that and that shut them up from saying that, okay, this is fake because there was the picture that they wanted. It's not fake. You've got your proof. I don't know what the next big leap is going to be from where we currently are in our state of consciousness. I would say if you, you know, you can ask synesthetes to interbreed with one another and produce more synesthetes and then we'll see what happens. Interestingly, though, is like is is there's a number of groups. There's five groups around the world that are tracking down the synesthesia genes to see what chromosome marker they lie on and they're getting better and better at this. David Eagleman was so funny when he started out. He said he was dealing with spatial sequence synesthesia, you know, the number forms. And he said, “Oh, it'll be just a couple of months. We'll we'll get the genes and knock it out and have an answer.” Well, that was decades ago. And he still hasn't gotten an answer, but we are getting better at it. And now once we have these markers, okay, we know that, you know, on chromosome four, on chromosome 16, these certain markers. Then we go out and we take a huge sample of people at random, let's say 1000 or 5000 people and we do their gene markers and say, who's got these markers? And okay, you've got you got the synesthesia gene markers, but you're not synesthesia. You're not synesthetic. So what do you like? Well, what what are these people like? You know, are they geniuses? Are they psychopaths? We don't know. We just have to do the work. But it's interesting, I think, is to be able to go in reverse and and say, here's the data, here are the genetic markers for synesthesia and these people have them. What are they like? Maybe we could teach that group synesthesia. I don't know, I don't I'm I'm doubtful, but I mean anything is possible. One of the things I love about school children doing book reports and things like that is that they say, oh, Joanne sees the world differently than the way I do. And yet she's still Joanne. She's my playmate, my classmate. And so this lightbulb goes off that, oh my God, other people know things too. My way isn't the one and only way. It's not the right way. And so it opens up people to being open to seeing that there are other kinds of points of view in the world, and being able maybe to do what I do in terms of resilience is letting go of needing to have my point of view always be right. You know? You know, I let go of that and, you know, surprising things happen. I learned something that I didn't think I would learn if I had clutched on to what I thought was the only real way of seeing things. You need to understand them. That that's the more important thing is not trying to correct them or argue with them, but trying to understand what it's like and nothing is better. Then tell me or tell me more.

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