The Audio Illusion That Proves We Don't Experience Reality

11:15Hannah Fry:Is pitch just completely constructed in the human mind?

11:19Michael Stevens:That's right. Are we really just decorating the air with percussion and then our brains go, no, no, no, no, no. That, that is Pink Floyd's Dark Side of the Moon. You know, that is beautiful harmonizing tones. I mean, pressure waves can harmonize physically. We know how to describe that. But the qualia, the experience of the sound, the subjective thing that we hear, the thing that, you know, the famous Mary's Room experiment, which asks about a girl named Mary who lives her whole life inside a little house where there's no color. She's not allowed to see her body. Let's put her in a black and white bodysuit.

11:59Michael Stevens:She has no mirrors. Everything is just black or white. And she's got a lot of books, though. And so she can read about the color red. She can read about what wavelength is and electromagnetic radiation. and she can read that roses are red and she can read about how the retina works and the different vision parts of the brain. She knows everything there is to know about red. Here's the question. If she's ever allowed to leave that room and she sees a red rose, has she learned something new about red? It's that redness that I'm getting at, pitchness. Is it an illusion properly?

12:34Hannah Fry:Actually experiencing it is different to understanding what it is and where it comes from. I've always wondered, you know that thing about Mary's room. I've always wondered, A, why does it have to be a girl? B, why is she called Mary? I've never really understood those two things. But this, of course, is something that has come back around to the sort of forefront of the scientific mind with the advent of artificial intelligence, because this whole question of experiencing something as opposed to understanding it, or even understanding it as opposed to having loads of knowledge about it, What does it mean to conceptually grasp something if you can't really experience it?

13:14Hannah Fry:All of these questions are now incredibly prevalent in the scientific literature.

13:18Michael Stevens:Yeah, what's it like to be a bat? What's it like to be an AI model? Well, you can play a note for AI and it could tell you exactly what note it was or what its frequency was and it could play that frequency back. But maybe it's just its microphone is vibrating at a certain speed. It takes that speed, gives you the answer, and then it plays it back for you by moving its speaker at the same frequency. How do we know inside, in its subjectiveness, wherever that would be if it's there, that they're experiencing and not just whatever's really there? Let's look at some other audio illusions. Some of these are incredibly famous and have been for a long time, so we don't need to spend forever on them or pretend like, what?

14:02Michael Stevens:Yanni or Laurel? But I didn't know the stories behind them. So Yanni Laurel, I'm sure many listeners have heard of it before. We'll play it for you. Here it comes. Yanni Laurel. Okay. Did you hear Laurel or Yanni there?

14:18Hannah Fry:I can only hear Laurel. Yanni Laurel. And if I try really hard.

14:24Michael Stevens:Yanni Laurel. Yanni Laurel. Yanni Laurel. Yanni Laurel. Yanni Laurel.

14:29Hannah Fry:I can't hear Yanni at all.

14:31Michael Stevens:I can't hear Yanni at all either. Are we sure it's in there? I'm sure it's in there. I really do believe the people who say they hear it, because if you cut out all of the lower frequencies in the sound, it sounds just like Yanni. Listen. Larry. Larry. Okay, that's without, like, the lower half of the frequencies. Now let's take out the upper half. Listen to this. Laurel. Laurel. Clearly Laurel. So they're both in there. Which one you hear depends a lot on how your ears work and also what kind of sounds you've grown up around. In fact, it's been shown that geographically people in L.A. tend to hear Laurel, but people in the southern England apparently hear Yanni more often.

15:16Michael Stevens:That's why I thought maybe because you're from the same country.

15:20Hannah Fry:Wait, why? Why? Why?

15:22Michael Stevens:We don't totally know. But the hypothesis is that the types of sounds, like literally the speaking voice registers that you grow up around, train you to focus on certain parts of noises. And so if you're focusing on lower noises, you're going to hear Laurel. But if in your daily life you're experiencing higher pitched noises, that's what's relevant to your fitness and survival in the world, you're going to hear Yanni.

15:47Hannah Fry:Is that the reason why people in LA hear Laurel? Because there's so much around them of people going, oh my gosh, hi, that they just learned to tune it out.

15:56Michael Stevens:Look, it could be. It literally could be. And I think it's important to emphasize we do not understand this illusion well enough that we can just write it up, make a little two minute YouTube video and say, here's how it works. We can do that for some illusions. A similar illusion to Yanni Laurel is the famous blue and gold dress, right? This is one where it's also very hard for people to see it one way or the other. um there are other illusions where it's very easy to flip like the necker cube that's the little two-dimensional line drawing of a cube that can either be seen um inside out or right side out depending on how you look the brainstorm green needle one have you heard that one no i

16:39Hannah Fry:hang on the brainstorm can i ask you about the dress though while i'm looking this up

16:42Michael Stevens:yeah which one do you see i see blue and black do you i always have but you don't

16:49Hannah Fry:No, I see green and white. Green? What was I talking about? Green? Whoa! Okay, there's a third option, folks. I see gold and white. However, that one I can switch. You can switch. With difficulty, but I have seen both. If you really look at it, especially if you sort of squint at it, then I can switch. But that one, in the same way, the sort of research on it demonstrates that people who have grown up around artificial lighting tend to interpret it differently to people who have spent their life outdoors, right? So like farming communities, for example, will see it one way and people who grew up in cities will see it another.

17:24Michael Stevens:Exactly. It's like very, I don't want to say hardwired, but it's like over easy wired into our brains based on where we live. My wife saw gold and yellow. Why? She saw gold and white first. And I think it has to do with, yeah, the world around you, the kind of lighting you are used to, that affects how you assume the ambient lighting in a photograph is. And that changes how you perceive the colors of the dress.

17:53Hannah Fry:Because the question is, is this a blue and black dress, which is just overexposed in the background, and so kind of looks a bit washed out, or is it something that is a green, oh my gosh, what is wrong in this? We found a new illusion.

18:10Michael Stevens:We found a new one. It's impossible for us to talk about the dress.

18:15Hannah Fry:Yeah. Or is it a golden white dress that has been overexplored by artificial lighting?

18:20Michael Stevens:If you listeners out there haven't looked at it for a while, go take a look. I mean, it's still a phenomenal illusion. And the teams that I worked with at the University of Chicago when I was a psychology student, they were emailing me about this illusion because it really did lead to new questions and progress in vision research. Oh, yeah. The illusion is so strong, and we don't know exactly how it works.

18:42Hannah Fry:Have you seen the socks and crocs version of this? No, no. Tell me about it. Okay, so this is a direct result of the dress, and some researchers working on vision perception. But I think in particular, it comes back to this idea that it's like your lived experience ends up changing the way that you interpret the world around you. And what they were trying to do was to recreate the illusion that was there in the dress, but also, I mean, in a different way in Yanni Laurel. And they were looking for things that had ambiguity over their color that would allow them to sort of tap into people's lived experiences.

19:20Hannah Fry:And they came up with Crocs and socks that they took in sort of ambiguous lighting.

19:27Michael Stevens:Okay, so to me, it looks like seafoam green socks and beige brownish Crocs.

19:35Hannah Fry:Okay, so to me, it looks like I can see that those are actually white socks. I can see they're white socks and the lighting's a bit off. And then there's sort of a pinky tone to the Crocs.

19:47Michael Stevens:So if you assume that there's just like a more electric green light on the scene, you've got white socks and pink Crocs. Whereas I'm coming at this thinking, oh, the white is just a white. It's got all the colors in it. So the socks themselves are electric, seafoamy green. And those shoes are just kind of like a drab olive color.

20:07Hannah Fry:Right. But I think that what this managed to do was it really demonstrated this hypothesis that actually in any situation where there's ambiguity and requires your brain to make a sort of binary interpretation of a scene, right? Is this a particular lighting that is imposing and changing the colour of this and should I interpret it in the original way or do I take this image as fact? It's really your lived experience and how much you have witnessed those kind of environments of artificial lighting, say, in the past that changes your perception, changes your actual experience of the world. Going back to what you were saying at the beginning about qualia, right?

20:42Hannah Fry:About the hard problem of consciousness. Is your green my green? Is your experience of the world the same as mine? And this is like a tiny little crack in the sort of great wall that we've been unable to break through to answer this question.

20:55Michael Stevens:It's a tiny crack. It doesn't demolish the whole thing because we still know that we're disagreeing. You know, we both know that, wait, you think that it's pink? I know what pink is and that's not pink. Like the word still means something to both of us. By the way, look at the Crocs and Socks picture and look at the caption below. This image is from Pascal Walsh. That's exactly the guy I worked with at UChicago.

21:20Hannah Fry:Amazing.

21:21Michael Stevens:So this became a huge thing. Yeah. He was one of my teachers. And we talked on Facebook about the illusion. So I don't know. I'm just trying to Berg. I'm trying to Berg here. Bask in reflected glory.

21:31Hannah Fry:I knew that guy. Berg's a good name for it. Berg's a good name for it because it's like, hey, look, you guys, you're seeing the tip of the iceberg, but underneath is me.

21:41Michael Stevens:Yeah, but really Berg, B-I-R-G, basking in reflected glory. It's a thing people do a lot. The opposite is called corfine, cutting off reflected failure. Oh, I was never really for this, or I wasn't really there that

21:54Hannah Fry:Mistakes were made.

21:56Michael Stevens:Yeah, yeah. So back to illusions. There are other illusions that are multi-stable. It's very easy for everyone to flip between one perception and the other. So this is the famous brainstorm green needle illusion. What you're about to watch is a toy that says brainstorm. That's the Ben 10 character. It's saying brainstorm. And yet, just like the Stroop color illusion, where it's really hard to say the name of a color when you're reading a word printed in that color. Here, if text green needle is put on the screen, you hear green needle.

22:32Hannah Fry:That is absolutely wild. I almost don't believe it. I always sort of want to rewind and it's like, have I just by fluke managed to match? Is the actual audio changing? And by fluke, I've sort of been concentrating on the correct word at the correct time. But no, it really is. You listen to the... If you rewind and play the precise same piece of audio but concentrate on the other word, you hear something different.

22:58Michael Stevens:Let's set this up so that the listeners can have their own experience. So what you're going to hear is a sound. And it will either sound like brainstorm or green needle. Just as we loop it, decide which one you're going to hear. You will hear that one.

23:16Michael Stevens:But it was the same sound every single time. So here, again, we've got a kind of small, low-quality speaker producing a sound with a lot of noise in it. However, here, different modalities can get involved to shift the brain to perceive it one way or the other. So if you see green needle or brainstorm written out, whenever you hear it, your brain goes, oh, that's what I'm expecting. Even if you watch the video of the original toy and you see that the light blinks three times, that makes you go, oh, there must be three syllables. And you're more likely to hear green needle. But green needle and brainstorm sound like such different words.

23:57Michael Stevens:How could there be ambiguity between those? And yet there is because the stimulus is very complex. and the way we take what's out there and turn it into a little show in our brain is dramatic.

24:10Hannah Fry:What is going on there? Is it about attention? Is it about something particular in the way that sound is constructed? Like what is going on? Why is that possible? Can I make my own version? Can I do one that says Michael and Hannah at the same time?

24:25Michael Stevens:You could definitely. It might take some work. You might need to test it on a lot of people. But yeah, you can always add in noise and change around frequencies and overlay things to the point at which it becomes ambiguous. And maybe only children would hear one word and adults hear the other. And then maybe even like elderly people hear a whole third thing. It's not completely drag and drop because we still don't know all the mechanisms behind it. You can watch every video on these illusions and find audiologists describing different aspects of the waveform. though at the end of the day it all has to do with either what mindset you're in what other modalities are there if you're using your eyes to see the word brainstorm or you're thinking the word green needle that's what the audio sensation will be perceived as however with yanni laurel that's like a deeper mechanism in the brain at fault assuming these are illusions which we'll get to later, where your lived experience is affecting your ability or disability to hear one thing or the other.

25:32Hannah Fry:This is called the, um, brainstorm one is the McGurk effect, right?

25:37Michael Stevens:Yes, exactly. The McGurk effect is another example of how different modalities work together to create a different reality.

25:45Hannah Fry:Tell me if this is the wrong thing, because I don't know very much about this, right? But like, when you mouth the word colorful, but the person thinks you're saying, I love you.

25:52Michael Stevens:Yeah.

25:54Hannah Fry:Let's try that.

25:55Michael Stevens:Is that an example? Let's do a little experiment. Okay. I'm going to say either I love you or colorful. Those of you listening, you'll know the answer, but those of you who are watching the video, hit mute when I say so, and then write in the comments below what you think I said. Okay, here we go. And I'll put my hand up when you should turn it back on. Okay. Mute your audio in three, two, one. Colorful. Hey. Okay. Unmute. Come back. Come back. If you were only watching me, write down below what you thought. So, yeah, we don't have like a completely isolated hearing system in our brains. We are taking clues from everywhere and putting them together.

26:38Michael Stevens:And ultimately, that's what we should be doing. It doesn't matter what the truth is. Here's the truth. Okay. Is it Laurel or Yanni? Truthfully, it's Laurel. Because here's the true story behind it. A man named J. Aubrey Jones recorded the word Laurel. That's what you're hearing his voice when you hear that sound. He recorded the word Laurel for Vocabulary.com. He recorded thousands of words so that people could hear the pronunciations. Well, then in May of 2018, there was a high school student named Katie Hetzel who either recorded a computer playing back his sound or she downloaded a low-quality version of that file.

27:18Michael Stevens:And another classmate of hers was like, that sounds like Yanni. And she's like, no, no, no, this is a recording of someone saying Laurel. And her classmate put it up on social media and was like, Yanni or Laurel, it's the new dress. The dress, by the way, I want to tell a story about the dress because I've never told this story before and this might be where I finally get some help. So, I almost played a role in the dress.

27:44Hannah Fry:Go on.

27:45Michael Stevens:Here's what happened.

27:46Hannah Fry:Burgas, Michael.

27:47Michael Stevens:The famous dress illusion started back in 2015, in February of 2015. Two people were getting married, Grace and Keir Johnson of Colonsee, Scotland? Colonsee? Either or. Either or?

28:03Hannah Fry:Say it twice. We'll lay them both over each other. We can ask the audience which one they hear correctly.

28:09Michael Stevens:What does the colon say? That's all I can think of. But anyway, that's where they lived and they were getting married. And the brides, so Grace's mother went to, and I got the exact location here, she went to the Cheshire Oaks Designer Outlet north of Chester.

28:25Hannah Fry:That's Cheshire, but yeah. Cheshire. Cheshire. Cheshire. Cheshire. Cheddar.

28:33Michael Stevens:you americans with your glossedest shire anyway go on she went to this outlet and she saw the dress took took the photo the photo that we now has gone viral and put it up on facebook and all facebook friends were like whoa is is that you know gold and white or blue and black and people were like what how can you see it differently than me but it didn't go viral until the day of the wedding when a friend of the bride and grooms, whose name was Caitlin McNeil, saw it in person being worn by the now mother-in-law, the mother of the bride, and said, holy cow, it really is blue and black. But the photo didn't look that way.

29:12Michael Stevens:And she shared it to her Tumblr on the 26th of February, 2015. And then it got really popular. BuzzFeed wound up covering it. But at four in the afternoon on the 26th of February, 2015, I received an email from a girl named Lizzie Rhodes. I'm giving out her name because I need your help, Lizzie. Who are you? She wrote, Michael, my friends and I were stumped when we began to argue about the color of a certain dress taken by one of us. Some see the colors as white and gold. Others see blue and black. I see blue and black. One of my friends posted it and we were getting all different comments about it.

29:53Michael Stevens:Are we crazy? Is there any way to explain this? What do you see? So I remember getting this email a little after midnight, eight minutes after midnight. In fact, if you want to be specific on that day. And I was like bleary and sleepy and about to go to bed. And I'm like, this is one of the craziest fan emails I've ever received because it's obviously blue and black. But she says people see it as gold and white. I get a lot of emails that are just like, hey, how come my nose is floating? And I'm like, no, you don't need a Vsauce video. You need help. So I just didn't think anything of it. The next day I went into work and everyone's talking about this thing.

30:31Michael Stevens:And I'm like, what? Oh my gosh. If I had recognized the potential here, it wouldn't have been Buzzfeed that scooped it. It would have been me. It would have been you.

30:41Hannah Fry:But to be fair, you didn't have very long though, right? You didn't have very much time. No. So wait, who was the person that emailed you?

30:48Michael Stevens:I was emailed by a person named Lizzie Rhodes. And a few times since then, which this was 11 years ago, I have like done a deep dive through Facebook to figure out is she friends with the Caitlin McNeil who originally posted it or friends with Grace and Kier, the bride and groom. I've never replied to her email because of my social anxiety and because it feels almost like rude to be like, yo, what up? I thought 11 years was long enough to finally get to this email. Thanks for reaching out. Thanks for watching. But yeah, I just realized this podcast is my chance to say, here's what happened. Lizzie, if you're out there, reply to the thread.

31:27Michael Stevens:I still have it. You emailed me three times, actually. I have all three of them and I never replied, but I've got them all. Yeah, she emailed me some other visual illusions that might be related. It was really great. And I just, I think at first I didn't believe that there was any illusion in this dress. And then the next day I felt like I'd missed out. I think ASAP Science made a video about it immediately. And I was just, it was just sour grapes. I just felt like, you know what, I'm not going to talk about it because I missed the boat. So now I have to act like it's not cool. So that's a huge mystery.

31:57Hannah Fry:Wow. What a great story. But I also think there, Michael, I mean, I think that that really demonstrates how well regarded you are, right? I know. Someone would come across something that was a bit strange and unusual and their first thought is to email you about it. There's something really lovely about that.

32:16Michael Stevens:I know. You're right. That really is the first primary emotion. It's a kind of honor. It's also a kind of responsibility. And I fell short. I was reached out to and I just went to bed.

32:29Hannah Fry:Right. Here's the question. You've mentioned this before, but I also get a lot of like... I mean, some of them are frankly unhinged emails and letters from people. Yeah, I can imagine. Like lots of them are really, really lovely. Lots of them are so gorgeous. I've got like a little feel-good folder in my house where I put everything that's just really lovely stuff. But some of them, you're right. You filter the ambiguity through your own experience. and my experience of reading some of these letters is that there's some people who sort of claim to have solved, you know, the Riemann hypothesis and it's like, it's kind of a bit kooky.

33:05Hannah Fry:And so my expectation when there's ambiguity is that like, this is not going to turn out to be anything. And so it does genuinely play on my mind sometimes that I might have missed something really remarkable. Because while this dress story turned out to be like this global sensation that we're still talking about 11 years later, I can completely imagine in 20, 30, 40 years that people will still occasionally mention this dress. It's sort of become like a phenomenon that's kind of evergreen. I wonder about all of the emails in your inbox that just didn't get picked up by BuzzFeed, that just didn't get posted to Tumblr, but are just as valuable and just as interesting.

33:41Michael Stevens:I gotta take them all seriously. You'll never know. And taking them seriously is all we can do. We can't take them literally. I'll talk about what I mean after the break. We're gonna come back. I'm going to show you another audio illusion, and we're going to talk about perception, reality, and whether anything is an illusion.

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36:36Michael Stevens:All right, welcome back. We are back, and I have a correction to make. I mentioned that Yanni Laurel perception can be geographically distributed. That I don't think has actually been found. I was thinking of what's called the tritone paradox. That's the one where where someone is from correlates with how they hear the sound. So, Hannah, I'm going to play for you two notes. Ba, ba. And I want you to tell me if they're going down or up in pitch.

37:07Hannah Fry:All right. Here we go.

37:12Michael Stevens:Up. No kidding. That's what I expected because you are British. I hear them going down. To me, it sounds like ba-ba.

37:27Michael Stevens:Really? Yeah. So this was discovered by Dana Deutsch, and she calls it the tritone paradox. It involves tritones, which are sounds that are a half octave apart, and they're kind of sandwiched together. So you hear two of them, and then one pair goes down and one goes up. depending on what frequency you in your lived experience have had to learn to prioritize, you will either hear the ascending notes or the descending notes as being more operative in what's happening. When you answer the question, is this going up or down? I hear that as, bah, bah. So, hold on.

38:05Hannah Fry:Okay, this is South of England versus?

38:08Michael Stevens:Southern California. Southern California.

38:10Hannah Fry:Why? What, why? Why? Like, what possible thing could we be hearing that would be so different?

38:16Michael Stevens:I think it's the different vocal registers. This is not my guess. This is from researchers who say that apparently people in Southern California talk with a lower pitch. Oh. So they're all like, yo, you know, it was gnarly. I guess even like no matter what gender you are, you're lower in general. But in Southern England, they're all like, hey, governor, oh, give me some brown sauce. Right?

38:45Hannah Fry:The most British thing you could think of, governor and brown sauce.

38:49Michael Stevens:Oh, my gosh. I'm glad that was so bad because I did just do that off the top of my head. No prep. I enjoyed it. And I nailed it.

38:57Hannah Fry:That's so strange. Wait, are those the only two? Have they tried for other countries around the world or are those just the only two?

39:03Michael Stevens:Those are the only two that I've heard of in my limited research on the subject. But it's very cool because tritones also have a long history of being fascinating to people. Because of these weird effects, they were even seen as possibly demonic back in the Middle Ages or medieval period, I believe. I know at some point in history, people were like, don't use them. It's the devil's voice, right?

39:25Hannah Fry:In the comments, can you tell us which way you hear it and where you're from? Yeah.

39:31Michael Stevens:And maybe also tell us your age, because I think that as we age, we hear different frequencies better or worse, usually worse. So yeah, give us that info. Here are the two notes we're talking about. Okay, write down below what you heard. Were they going up in pitch or down in pitch?

39:49Hannah Fry:This is really interesting, though. I mean, it's coming back to a similar thing, right? Which is that like your perception of reality is sort of constructed in your own mind as a basis of your experience. Yeah, it's not just all of our brains do this one funny trick.

40:04Michael Stevens:No, they all do tricks in their own way based on what environment they have been raised in and learn to navigate. There are a lot of other really good videos online of audio illusions. Veritasium did one a year ago that's really good. I'll tell you what not to do, though. I watched the video last night with no headphones on at one and a half speed. Sorry, Derek. and if you have no headphones on and you've sped it up, instead of being a video of illusions, it is a video of no illusions. None of them work, right? I just took his word for it. But I also could not figure out what the opposite of an illusion was.

40:44Michael Stevens:What do you call that? So last night, I didn't want to look it up. I just tried to like ideate some things and I came up with, it's not an illusion, it's an elaborare. because laborare means labor, which is the opposite of luder, which is where we get illusion from. Luder means to play.

41:05Hannah Fry:Oh, really?

41:06Michael Stevens:And illusion is in play. Yeah. Illusions are playful. And if it's not playful, then it's labor, it's work.

41:13Hannah Fry:I like that a lot. That was me just thinking you were saying God would go, but actually it was well-researched.

41:19Michael Stevens:A lifetime of studying words. I did do the research. I don't know Latin off the top of my head, but I wanted to come up with my own antonym of illusion. So like an illusion is cool, but a in laberare would be look at this circle. It really is a circle. It's an anti illusion. Then I thought maybe unillusion, but that sounded like an illusion that you've undone. yeah then i thought well even though it's etymologically not correct to do this you could say it's not an illusion this is a illusion it's just the way it is because ill sounds like wrong ill sick um however there is a real word scientists use psychologists use for something that's just true are yours frankly better no mine are worse the what the word they use is veridical as in like truthful as in true yeah like veridically these lines are the same length But there's an illusion where one appears to be longer than the other.

42:17Hannah Fry:Nah, I'm going for illusion.

42:19Michael Stevens:Illusion for the rest of time. There are some places that are called something sound, aren't there?

42:24Hannah Fry:Yeah, like Puget Sound.

42:26Michael Stevens:Interestingly, this is completely unrelated, but let's just do it. The Mariana Trench was discovered, like, purely out of luck. it was discovered in 1875 by a research vessel called the challenger that was just measuring the depth of the ocean in different places one of the places they tested happened to be what we now know is the southern end of the mariana trench and they just dropped like a weight tied to a rope off the boat they were like this isn't this isn't stopping we haven't reached the bottom what the heck? And it went on and on and on. And they were like, dude, this is unbelievable.

43:06Michael Stevens:And they wrote it down and everyone's like, whoa, the ocean is a lot deeper than we thought. So they named it. It became a feature. They knew that it was a trench. But that was in 1875. Just by chance, that was one of the spots they checked. We didn't discover the second deepest trench in the ocean until 1952. That's the Tonga Trench. So the fact that like almost a hundred years prior, someone had just checked right at the Mariana Trench is like total, total coincidence that we got the deepest one. We just tried that right off the bat. The chances of that seem pretty,

43:43Hannah Fry:pretty insignificant.

43:44Michael Stevens:The ocean is a big place.

43:46Hannah Fry:The ocean is a very big place.

43:48Michael Stevens:There was one other really neat thing in Veritasium's video that I'm just going to share. You should go watch the whole video, but he talks about why our ear shapes are so weird. Why do we need to have this funky thing? Microphones don't look like these. Microphones are just, look at this. It's just like a cylinder or a ball or something. And it has to do with helping us localize the position, the location, the origin of a sound when it's not off to the side. because when a sound is off to the side, we have a lot of clues about where it's coming from because it gets attenuated when it passes through our head.

44:26Michael Stevens:So one ear hears it louder than the other. One ear hears it before the other. But if a sound is right in front of us along this line, either below or up above me, even behind me, it's symmetric about my ears. They both get the same stimulus. Yeah. But they don't because my ears are so unsymmetrical along that axis. So sounds coming from above me come in like this, and they're like going past my earlobe down past the top of my ear, and they're going to reverberate and be reflected differently than frequencies that come from below or from right in front of me. Those are going to hit, you know, I don't know how they hit, but they're hitting the ear in different ways.

45:08Michael Stevens:And different frequencies are better or worse reflected by the different weird spiral folds of the cartilage of our ear. And over time, from when we're little babies to when we're a bit older, we learn how to connect the perception we get because of what our ear does to the sound to where it is. And researchers have done experiments where they've put little like molds on top of people's outer ears to make them differently spiraled. I can have someone make ears that look like yours, stick them on top of mine. And now I'm hearing with your outer ear. By the way, this, the flap, the thing that we call an ear, like when you, when you say someone, oh, you didn't draw the ears yet.

45:45Michael Stevens:And they draw this outside thing that we can see. This is called the oracle or the pinna. Pinna is usually used in zoology. Like a pinna is a non-human animal ear, outer ear. But for humans, we call this an oracle. Anyway, they put prosthetic oracles on people that were different shapes. And the people suddenly could not tell where a sound was if it was symmetrically situated to their ears.

46:09Hannah Fry:Did the ear look like it could conceivably be another human person's ear. So it's just that you hadn't had the training of tuning your, I mean, because you sort of get to verify it, right? Like you think a sound is coming from over there and you get to verify it. You haven't had that training process essentially for your entire life with that particular ear shape. That's right.

46:30Michael Stevens:And it only takes a few days, like a week at most, for people to learn how to use their new ear shapes. And suddenly they're really good at picking out where a sound is that's right above them, right in front of them, right behind them. And then when they removed the prosthetics, people were able to go back to their normal ears very quickly. Yeah.

46:48Hannah Fry:Okay. I want to go and grab something that I have downstairs, because there are people who study ear shapes to an unbelievable degree. Just hold on a second for me. Oh. I'm going to get something too. So, this idea about people really caring about the shape of the ears, of course, if you design headphones, right? And particularly if you are designing headphones that are noise-cancelling, where you want to play a sound into the ear that exactly cancels out any external sounds, then the way that an ear is shaped becomes really, really integral to what you're doing. So anyway, a little while ago, I made this program where I got to go and visit Bose in Boston.

47:40Hannah Fry:Ooh. And literally all over the place, I'm just opening this as I go. What are you opening? Like some Japanese puzzle box? I know. It's like, I've had it framed, so I'm opening the frame. Oh. Okay, so anyway, in Bose, literally everywhere are these really weird little ears. Oh, cool. Is that your ear? No. They didn't do one of my ear, but they have like genuinely hundreds and hundreds and hundreds of these that they are continually testing for how sound changes, for how the different headphones work, for how it reflects sounds, for how it understands like, I mean, exactly what you were describing about how sound changes depending on the shape of your ear.

48:22Hannah Fry:And they attach them to these models that have microphones inside them essentially and run these like insane scientific experiments, like really, really sophisticated in order to make sure that they're making headphones that can actually be used by everybody rather than just a few people. I want to show you it because it's really fun.

48:41Michael Stevens:Okay, while she's opening it, I'm going to show off my new mechanical pencils. And editors, I dare you to leave this in. If you don't, I'll be so disappointed. So look, I hate long pencils. This is an unsharpened Ticonderoga. So long, I feel embarrassed to use it. But look at this. Look at this winner. This is the Koh-i-Noor 522-8. Look how much shorter it is.

49:03Hannah Fry:Koh-i-Noor? Is it like diamond?

49:05Michael Stevens:It's named after the diamond, the queen's diamond. There you go. Versatile. And they make an even thinner one. That's actually too thin, but it's metal. So this is wood. This feels good. But let me show you something else. Okay, here's the Koh-i-Noor 522-8. Look at this one. Oto W-N-O-2. It's a needle.

49:28Hannah Fry:dinky look at that dinkster okay i'm finally in it's in okay so i won't show myself once okay here

49:35Michael Stevens:we go i have one more small one and you guys will have to just subscribe and i'll show it off later when we do the club that's what the club could be yeah oh members only whatever's hiding behind my

49:47Hannah Fry:hand okay so here here's the little ear it's the most one look at that goodness that is some people Some people do have really flippy floppy ears. Whose ear is that floppy? Children's. Really? I reckon. I mean, they do get harder, sort of, the cartilage solidifies as you age. But anyway, when you are in Bose, I realised that they had just hundreds and hundreds and hundreds of these lying around all over the place, which are essentially silicon moulds of different ear shapes. This one, it's so much fun to play with. It's like, it's really floppy. You know, So you can kind of like tickle it and dangle it.

50:26Hannah Fry:Yeah. It's a mold of a human ear, right? So it looks exactly like a human ear. But you realize when you're in this company just how much variation there is in human ear shape. Because, I mean, the general structure is kind of the same. You have like the outer part. You have, this is the helix, is it? You've got the daith here. I think this is the conch. Oh, no, hang on. That's the tragus, isn't it? Sorry. I forget on which bit's which. Look how big your daith is. Oh my gosh. You could get a monster piercing on that if you wanted.

50:58Michael Stevens:Maybe I will. Talk about monster dates. Here's a monster ear.

51:04Hannah Fry:Look!

51:05Michael Stevens:Hey, look. My ear is not floppy.

51:08Hannah Fry:No, yours is not floppy.

51:10Michael Stevens:But it has a middle and inner ear, so... I'm holding up, by the way, a very oversized plastic model for like doctor's offices and medical schools of the ear and the inside parts of the skull, the ossicles, cochlea.

51:23Hannah Fry:But you know what? You can see the S shape of the ear canal in that, which I always think is really fascinating. That it's not just this straight tube. I'm a bit obsessed with the ear, you know. I'm going to bring up ears again, but not today.

51:37Michael Stevens:We're not done with ears. No, today we're talking about illusions or unillusions or enlaborares. Maybe, maybe. So look, we're not going to come to any answers about the true nature of reality today. But, you know, on this show, we bring this up a lot. It usually falls under the hard problem of consciousness. I've said a lot of times that I think illusions show us that being right doesn't really matter. What matters when it comes to existing is survival. It's fitness. Just because you're right doesn't mean you're alive. It's better to be wrong and alive than right and dead.

52:18Hannah Fry:And it's better to make your decisions quickly. than wait until you have complete information. It's better to update your guesses based on the evidence that's in front of you and have them as guesses rather than only proceed when you're certain.

52:34Michael Stevens:That's right. That's right. I mean, and this has been mathematically shown to be true when constructing little environments. So, like, of course we don't get everything right. Of course we listen to fast percussive beats and we perceive a tone. It's more helpful in some way, probably, because natural selection chose that to happen. And if instead we had the machinery in our brains and we had some kind of special nerve cell that could fire 20 ,000 times a second so that we could tell where each individual beat was, that would be a waste of resources. So instead, we're wrong. We as a species or as life invented, completely invented a completely made up thing called pitch that we experience in our own heads alone because I think it helps us survive.

53:23Michael Stevens:It helps us make decisions faster and process more efficiently.

53:27Hannah Fry:Well, thank goodness because it doesn't just help us survive. It also turns out to be one of the great sources of joy.

53:34Michael Stevens:Yeah, exactly. Exactly. It's beautiful as well. And I don't know if it was always beautiful, if we just learned to think it's beautiful. But Donald Hoffman talked about this in The Case Against Reality, which is a fantastic book. He actually gave this a name and I forgot about it until I was researching this morning, but he calls it the fitness beats truth theorem. He defines an illusion as a perception that fails to guide adaptive behavior. So he's like, look, let's look at insects that eat feces. Okay. To them, it's amazing. They love it when they smell it, they go to it and they consume it.

54:13Michael Stevens:So what's going on there? Are they under some kind of taste illusion where they think it's good? Or maybe it does taste good, and we all have an illusory experience of, ew, that's gross. Who's right? Which one's the illusion? And he's like, neither. If it's adaptive, if it helps your species survive, then it just is what it is. And the truth out there will never be accessed.

54:35Hannah Fry:Because there is no ground truth, because it is only via experience.

54:39Michael Stevens:All we have access to is a user interface, basically. What I call my office is actually the user interface my brain makes that I can then navigate without needing to worry about the complexities of all the electromagnetic wavelengths and all of the noisy signals that are coming at me right now. And so he has a name for that as well, and he calls that the interface theory of perception, where he's like, to ask whether my perception of the moon is veridical, like, is this an illusion? Does it really appear that large? It looks bigger at the horizon. And he's like, just give it up. Because whether I see the true color, shape, or position of a moon that exists even when no one looks is like asking whether the paintbrush icon in my graphics app reveals the true color, shape, and position of a paintbrush inside my computer.

55:29Michael Stevens:Right. Reality is the computer. The user interface is on a screen inside here, and we're just perceiving that. And it's very helpful and it has been built by natural selection to help us live, survive, make decisions as quickly as we should.

55:45Hannah Fry:I like that a lot. I like that a lot. I also just like anything that ends in give up.

55:51Michael Stevens:Just give up. Just embrace it. Yeah. We'll never know what veridical reality is. what we do have access to is even better it's what's kept us alive it's what's kept us safe

56:06Hannah Fry:and sound and and in play thank you very much and in play ludair lu illusion ludicrous they all come

56:17Michael Stevens:from to play you know sound sound meaning healthy like of sound mind to be safe and sound that's not redundant. Safe means there's no risk of injury. Sound means there are no current injuries. And that comes from a totally different etymological root. That comes from like old Germanic languages, gesund, like health. Like gesundheit. Gesundheit, right? Sound in the sense of healthy comes from there. Whereas sound that you hear comes from the Proto-Indo-European like swen or something, which just meant a sound. It's where we get resonate and sonic. But then there's a third meaning of sound, like Puget sound.

56:59Michael Stevens:Sound can also be a body of water. And that comes also from Germanic. It comes from sund, meaning swim. And that is why when we check how deep a body of water is, a sund, a channel of water, we're sounding the water. We have a sounding line. So sounding can mean making a noise. It can mean being healthy, but it can also mean measuring the depth of a water body.

57:27Hannah Fry:That brings this episode to a resounding end. Yeah, it sure resounding.

57:34Michael Stevens:Oh, it sure does. And I hope you all are safe and sound who are out there listening. We appreciate you listening to our sounds. If you have questions, please send them in to the rest is science at goal hanger dot com.

57:47Hannah Fry:And as ever, leave us comments, like and subscribe. I mean, I feel slightly sick saying that, but it genuinely does make a massive difference. And we will see you next time. Bye.

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