#13 How we perceive the world

This episode is brought to you by LifeLock. Between two-factor authentication, strong passwords, and a VPN, you try to be in control of how your info is protected. But many other places also have it, and they might not be as careful. That's why LifeLock monitors hundreds of millions of data points a second for threats. If your identity is stolen, they'll fix it, guaranteed, or your money back. save up to 40% your first year visit lifelock.com slash podcast for 40% off terms apply

Hello, and welcome back to your weekly dose of escapism aboard the New Scientist Escape Pod. I'm Timothy Revel, New Scientist's comment and culture editor, and this week we'll be serving up perception three different ways. In the escape pod with me, we have editor of features, Anna Deming. Hi, Anna. Hi. Hi. What have you got for us this week? I'm going to delve into the science that explains with perfect precision how little we can know.

OK, that sounds great. And we've also pinched Claire Wilson from the news desk. Hi, Claire. Hello. Hiya. What will you be talking about this week? Well I will also be looking at knowledge because I will be exploring how much we can know about what we know. Oh sounds very interesting and I'll be talking about one way in which our perceptions can be tricked.

But before we get going, remember Escape Pod listeners can get a special discount to all of New Scientist's content. We've got fantastic articles and videos on everything from astronomy to zoology. If that sounds of interest, and how could it not, then visit newscientist.com forward slash escape 20 for a special discount code.

Right, I'm promoting myself up the order this week as I've got a clip I just can't wait to play you. We've got some tenterhicks now. What's this clip then? Well, so the area of perception I've been looking into is how we perceive the world using our ears. And many people have two of them, as you might have noticed. And that's incredibly important.

So it's not just redundancy. Instead, it gives us the ability to locate things. So this clip I've got illustrates this point really well. And I think it's quite something. But to get the most of it, you need to be wearing headphones or earphones. and ideally the best ones you've got. So if you're ready, let's play the clip.

That's awful because the one on the left just comes right from where my door is. So I literally thought somebody else in the house was knocking on my door then. And the other disturbing thing for me is that... The knocking on the right, there's just a big window on my right. So I feel a bit like I'm in one of those vampire movies when a vampire suddenly starts knocking on your window and I'm two floors up. So that was a bit disturbing for me.

Yeah, it sort of gave me the chills the first time I heard it. And when Ollie, our producer, listened to it the first time when I sent it over to him, he took off his headphones. and went to the door because he thought someone was there, which I think is pretty funny. Should we just have that clip once more? So surely stereo, the ability to play different sounds into our two ears has existed for a long time. So why is this so good? Well, so we're sort of being tricked.

And it comes down to really how we hear things and then just making the most out of that. So obviously, you've just got two earphones in or two speakers pointing into your ears. But it's a combination of sort of how our brain processes sound. and also a clever recording technique that comes together to produce this particular clip.

So the first bit you need to know about how it works is how we perceive sound comes down to the anatomy of our heads. So when you hear a sound, depending on where it's coming from, the sound reaches your two ears at slightly different times.

and is slightly louder in the ear that is most closely facing the noise. So for example, if you've got something coming from the left, like a knock, you hear it in your left ear first, and then you hear it in your right ear, but you also get a sort of reverberation where the sound interacts with your head and the...

squidgy bits in between your skull, and then reaches both of your ears again. So all of this produces a whole bunch of different sounds from a single knock. And all of these things combine to... produce particular sound waves that your brain then uses to determine where a sound comes from so in this clip it's using it's really like highlighting this feature and using it to convince you of

something sounding like it's coming from a different location. So normally when you record stuff, there's mono and stereo. So as you say, mono is like you just have a single microphone and stereo is two microphones, but they're normally placed. If you've got two microphones, they're normally just placed apart from each other and in front of whatever it is you're trying to record, so like an instrument or a person speaking. But with this particular sound, instead it's recorded...

like the sound has gone straight into your ears. So the person who recorded this is someone called Stefan Pidgeon, and he's featured on the show before, and he created a mannequin that he then puts two microphones inside the ear. And then that way you capture exactly what you would hear if you were in the place of the mannequin rather than just in front of something that you were listening to. So do you need special microphones for that?

Yeah. So you need very small microphones and ones with quite a lot of direction. So this technique is called binaural recording. So you do need to have it specifically so that it's sort of pointing outwards. You know, you wouldn't normally, if you were recording something, have two microphones pointing in complete opposite directions, like Stefan has done here. And the mannequin is actually, he fondly calls it Mike.

sent a picture of this, which we might be able to put on Twitter, of his mannequin called Mike that he uses to record these. So there are some microphones you can buy for it, but he's actually created his own microphones and then sticks them in the ear. So that means you get all of this stuff that the brain needs to process where sound is coming from. You get a slight difference in when the...

sounds arrive, but you also get some sort of reverberation inside the head also being picked up by the microphones. So it's quite a common technique. So you can get it where there are concerts recorded this way. And instead of sounding like you're just in front of it, like you would be at a concert, it's sort of like you're stood in the middle of the stage, hearing everyone around you. So I think maybe should we have that clip once more?

I wonder how many people have gone and checked the door again.

All right, Anna, so tell us, what does quantum mechanics have to do with perception? Yes, I was a little bit mysterious about the way I introduced it, but quantum mechanics is definitely one of those theories where... What science tells us is going on seems to clash with how we perceive the world around us in our everyday lives. So the term quantum mechanics comes from the idea that...

Energy can only be exchanged and so on in discrete chunks or quanta. So already that's not quite how we see things happening in the world around us. You don't feel yourself. sinking through abrupt levels of lower energy as you get tired or well speak for yourself suddenly dropping This might be more dangerous if you're driving a car. You don't find yourself adjusting the speed of your car by tens of miles per hour at a time. Those changes there, it's all continuous. But if you...

do look at the quantum level, you find all these energy levels have very definite gaps between them. So you are literally abruptly moving from one discrete level to another discrete level. So if you think of it as a kind of pixelation that smooths over as you zoom out, like the way the lines and colours on your computer or phone screen look smooth, although they are actually made of discrete dots and pixels.

then you can kind of see how something that is discrete at the very tiny scale kind of smooths over into a continuum as we perceive it in the world around us at a larger scale. Yeah, I think once you sort of get your head around the idea that the world is quantum, then that bit sort of makes some sense. You know, the idea that if you zoom out, then you just can't see the chunks, just like pixels on a screen.

Are there some other ways that quantum mechanics clashes with our perception of the world? Yeah, and I think some of the others are a little bit... less intuitive perhaps to get your head around so one of the other things that plops out of quantum theory is the inability to define things like like pairs of things like position and momentum or whatever with arbitrary position

So this follows on from Heisenberg's uncertainty principle. Heisenberg figured out that for certain pairs, like position and momentum, or there's also energy and time, the better you know one, the less you can know the other. So this seems completely counterintuitive to me. I cannot get my head around this because it feels like the way we perceive the world is that you can know both where you are and what the time is, or at least that's how it feels like most of the time.

Yeah, you kind of like to think that you could know where you are and where you're going at the same time. But not if you're a quantum particle. So Camilla Pang had a nice analogy for it in her book, Explaining Humans, when she said... The more you set your stakes for future gratification, so the more you're planning ahead, the less you're living in the present and vice versa.

similar kind of trade-off as you get with your quantum particles and knowing their position versus their momentum or whatever. So it might sound woolly but it's actually a really tight theorem with really precisely defined values for what these uncertainties will be and it's been rigorously tested so that's what i meant by saying how precisely we can know what we can't know

OK, but what does that really mean in reality? How does that take shape? It means that particles don't actually have a definite position. So you couldn't give a specific value for its position. quantum mechanics is saying instead is that you have something like a what we call a wave function or basically an equation that describes

What it really describes is your chances of measuring the particle and finding it in a particular position. So you end up with probabilities rather than a specific position. That's really weird that, isn't it? Well, for a lot of people, that idea went down like a French kiss at a family reunion. Einstein is quoted as, he was one of them, and he was quoted as famously saying, God does not play dice with the universe.

Well, it's just that's not how we see the world, is it? So I think that's why people like me, a biologist, just find it so hard to accept. I mean, if what you're saying is true, so why doesn't... Why don't we see the position of everything as kind of blurred out when you look at it, when we look at just things like tables and chairs around us?

Yeah, it does look a little bit like quantum mechanics has fallen out with observations at the first hurdle, because like you say, it turns out that's not how things are when you're looking at them. It turns out that when you measure a particle, all of a sudden it has a definite position and it's the value you measure. So it's a bit like when you're dithering over a menu and then the waiter comes.

And you just order anything. I do that all the time. So the particle kind of finally makes up its mind. So the story is that by the time you get to something like the size of a chair, you've got... loads of these particles all working together to form the chair and all the interactions between these fundamental particles are like

measurements forcing the particles to adopt specific values for whatever it is their position or spin or whatever so that way you end up with a chair being exactly where it is Yeah, it's sort of convenient, isn't it? The thing I always wonder about this is like, is the maths actually describing what's going on? Or is it just that...

the maths leading up to it maybe is not what reality is like. But once you solve the equations, the thing that pops out is what we see, and it is like reality. So maybe there's some sort of, maybe we don't understand the bit beforehand, but maybe it's still good at predicting. what we see in the real world. Yeah, this is definitely up for debate still. I think some people are thinking that...

The mass works, so don't worry about it. Some people say, yeah, but we don't actually know what's going on behind it. It's definitely hairy territory still. It could be that fundamental particles have multiple positions before you measure them. Or it could be that we end up with a parallel multiverses where each of the possible outcomes happens. So it's an ongoing argument. It's even an ongoing argument whether to...

to debate what's going on and whether to just trust the maths. So nonetheless, quantum mechanics challenges our perceptions for sure.

Now, Claire, you've been looking into metacognition, right? What is that? Well, cognition just means thought processes or the process of acquiring knowledge. So metacognition is knowledge about knowledge. So how much we know about what we know. Right. So is that something we know a lot about? I mean, I guess what I'm asking is how much do we know about how much we know about what we know? If you know what I mean. I have no idea.

Okay, well, this is very interesting to cognitive scientists, because this may be a trait that is, if not uniquely human, certainly much more developed in humans than in other species. So the example I like to use is... to think about dogs which are quite intelligent animals in some respects so um we used to have a dog called Tess and whenever she heard someone pick up their front door keys from a bowl before they left the house she would think that it was a sign she was going to be taken for a

a walk she would get all excited but of course sometimes when people picked up their keys to go out they were just going to work say and poor Tess was disappointed but she never seemed to learn so Tess was good at picking up cues from her environment and making it inferences but not good at judging how likely she was to be right or wrong about those inferences. But people on the other hand are better at judging the quality of their knowledge or their metacognition.

So knowing that sometimes we really are certain about something, but other times we only have a hunch. Yeah. So like I know when my girlfriend picks up her keys, I might be going on the walk, but she also might be going without me. You can judge that. Yeah, I can judge. Yeah, so metacognition, this is sort of about how we perceive our own knowledge. Exactly. Yeah, so it seems quite nebulous. How do you actually study something like that?

So to study this in the lab, you have to be quite cunning, actually, because if we just ask people how sure they are about their performance in a task, say, the results are going to be muddled by the variation in their ability to do that task. So are you measuring? ability or knowledge of that ability. So what you need is an extra step. You ask people to do a simple task.

So in the case of a study in 2012, it was a visual task. You showed people stripy patches in different shades of grey and asked them which has the greatest contrast. And after each question, you ask them to rate how confident they are that they got the right answer. So crucially, you can adjust the contrast of the stripes so that no matter how good their vision, everyone gets about 70% of the answers right.

means that for the confidence ratings the only variable is people's metacognitive abilities. So what did that tell us then? Well, one thing it told us is that there is variation in people's metacognitive abilities. So that might not sound surprising, but it was the first time that it had been shown in the lab and measured. Another thing was that this study may have managed to locate the place in the brain that is the seat of our metacognition, or at least one important area in the brain.

And that's because they did brain scans on the same volunteers. And they found that people with better metacognition had larger volume of gray matter or brain cells in a certain area of the brain called the anterior prefrontal cortex, which is just behind the forehead. I mean, this is all really pretty fascinating, but can we use it for anything? Are there some practical applications of it?

Well, there might be. So some people think that poor metacognitive abilities are a factor in some mental health problems, such as schizophrenia and obsessive compulsive disorder. So in OCD, for instance, imagine someone who has to... repeatedly check that they locked their front door. They know they have locked it on one level and yet they don't have enough confidence in that knowledge. So there are probably a lot of other things going on in OCD too. It's not a simple condition.

But that is one way to look at it. So do you think we might ever treat OCD by boosting people's metacognition? It's too soon to say for sure, but there are people trying to do just that, to look for ways to improve metacognitive abilities. So one group in the US is looking into training people to have better metacognition, perhaps using those same. kind of...

lab tests that we talked about earlier and giving them feedback on when they were right or wrong. Another group in London has found that a certain drug boosts metacognition in lab tests in healthy volunteers. So that's some way. from finding that it does help people with OCD, but that would be the next step. That would be amazing. That's all for Escape Pod this week.

Remember to subscribe and tell all of your friends. You can get in touch with any of us on Twitter at New Scientist Pod, and please send us your thoughts and your favourite escapisms. And remember, for a 20% discount on a subscription to New Scientist, go to newscientist.com slash escape20. Thanks for listening. Bye. Bye. This podcast is produced