Today, Explained - The sixth sense (the real one)

Episode Date: February 21, 2020

A study at the National Institutes of Health offers a window into some of science’s biggest mysteries, from the origins of pain to how consciousness works. (Transcript here.) Learn more about your ad choices. Visit podcastchoices.com/adchoices

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Visit connectsontario.ca. Close your eyes. Touch your chest. Reach your hand out. Touch your chest. Chest. Chest. Chest. chest, chest. Over the summer, I went to the National Institutes of Health in Bethesda, Maryland, to see a study take place. This is Brian.

And we go into a lab. It's a big white square room. On the walls are a dozen-plus infrared cameras, and they're all pointing at the center. And in the center. And in the center of the room, there's a desk and a chair, and a woman strapped to the chair. What they're investigating here is extremely rare and is something that really made me think a lot about, what does it mean to have a body? All eyes and all these cameras on this woman in the center of the room, and she's asked to do a pretty simple test.

So out on the desk in front of her, there's a cylinder. It's a black cylinder, and there's a little piece of plastic. It's kind of like a motion capture ball. And she's asked to... Touch her sternum, and then touch the ball. It's really unremarkable. Like, okay, she touched it. And then comes the hard part.

No. We're comes the hard part. And they have her close her eyes. And it's like it was erased from her mind. She suddenly starts groping, like to the left, to the right, kind of smacking it. And if she does, it kind of seems as though it was an accident. This woman was actually one of two sisters being studied at the NIH. And later on, I saw the other sister perform a walking test. Now that you have your eyes closed, do you need to rest first? And then they had her try to walk in a straight line with her eyes closed. And she just, like, gave this nervous smile. And really, it almost kind of looked like

she was being controlled like a marionette. And it's funny because she later told me that while she was doing that, she was cheating, that her eyes were open just a little smidgen. Because if she truly closed her eyes all the way, she doesn't know where her legs are. And she would just collapse. What they told me is that when they close their eyes, they lose their bodies. Sean? Sean?

Sean? Yeah, yeah, yeah, what? I kind of feel like we should give some context here. Okay, yeah, so that was our friendly neighborhood science reporter here at Vox, Brian Resnick. You are today's explained reporter, Noam Hasenfeld, Okay, yeah, so that was our friendly neighborhood science reporter here at Vox, Brian Resnick. You are today explained reporter Noam Hasenfeld, and you guys have been talking about this study he saw. And just listening to that, I'm wondering, like, when Brian said, touch your chest, now close your eyes and touch your chest, I had no problem doing that. But these women can't? They're struggling? Do I have something that they don't?

You do, yeah. It's a sense, and it's called proprioception proprioception yeah it's kind of like a sixth sense it's basically the sense of knowing where your body is in three-dimensional space okay you have a computer in front of you right yeah i got like a microphone and a computer so close your eyes and touch the computer okay easy right yeah you saw it you had a picture in your head of where it was and you remembered where and touch the computer. Okay. Easy, right? Yeah. You saw it, you had a picture in your head of where it was, and you remembered where it was. The harder question, though, is how do you know where your fingertip is? I guess I just have, like, an innate sense of it?

That's proprioception. Huh. That's not just memory. It's related. We have memories for all of our senses. We can envision what things look like. We can remember a smell. But for people without proprioception, they have nothing to remember. And that's what led to this experiment we were hearing about at the top at the NIH?

Yeah, exactly. They're basically studying proprioception there because it's sort of this doorway to a mysterious universe. We don't actually understand a lot about how proprioception works as well as it does in the body. And studying it could change the way we think about a lot of big scientific questions, like how touch works or how pain works or even how consciousness works. And this is what you spoke to Brian about? Yeah. And at first, he had some trouble putting it into words. You just know, right?

It's actually really hard to think about. It's just implicit. When you close your eyes, it's not like the world disappears. There's an impression of it. That's proprioception. Proprioception is critical for that type of coordination where you can close your eyes and you can reach out and you can touch something. Because how else would you know where it is? This is new for me.

I mean, I imagine it's new for a lot of people listening. Yeah. How do we not know that we have this sense? So with other senses, they attenuate, they go up and down. You can see bright things, you can see dim things. Perp reception never turns down. You can see bright things, you can see dim things. Proprioception never turns down. It's always at the same volume. It's always on. So you don't notice it.

So is this an everyday thing? Like, what do you actually use proprioception for? You use it to know, like, how far and how fast to reach out your arm. You use proprioception to keep your spine straight. These people without it, they have these horrible scoliotic postures. Every muscle in your back needs to work in concert to keep your spine straight. If you just had to look at your legs the whole time while you were walking, you couldn't look at anything else. There's actually one example of a patient. He lost his proprioception due to an illness. I tried to learn to sit up for days, weeks, and I had terrible tummy pains and pulled muscles, sort of, it felt like.

And it was exceedingly frustrating. I've been sitting up all my life until that point. And suddenly, I was deprived of the simple act of just sitting up. And he had to learn to walk again by watching his legs and seeing how far he would move them. I could move my hands a bit, but only if they were in vision. But as soon as I looked away, they would float off. Like if he wasn't looking at his legs, he couldn't walk. So how does proprioception actually work in our body? What are the mechanics here?

In every muscle of your body, you have this structure called a spindle, where there's sensory nerves in the spindle, which are sensing how far your muscle has been stretched. Kind of like the doorbell to your nervous system saying, hey, there's like a mechanical force here, like you should feel it, you should feel it. And every muscle of your body is sending this information to your spinal cord and your brain all the time. If each muscle is telling the spinal cord and brain how far it's stretched, then the spinal cord and brain can do this computation and figure out where it is. The wildest thing is that no one understands how the brain and spinal cord does this computation.

It's massive and enormous, and it happens nearly instantaneously. And these women that I saw are part of the research effort to try to figure some of this out. So these women, did they have an injury? No, they have a genetic condition. They're actually missing a receptor that is found on the nerves that enter the muscle spindle. And so they're missing this one thing, and it kind of makes them blind to proprioception. In a lot of ways, they're kind of like discovering the first blind or deaf people,

but they're the first people who are blind to proprioception. Hmm. How many of these people are there? So the NIH has been scouring the world, asking doctors around the world to look out for these people. And so far, they've found about 17. So if it's only a handful of people so far that have been discovered who are, say, blind to proprioception, what are scientists hoping to get out of the research? Well, the beauty of a lot of basic research in biology is just finding out how nature built something can help us learn how to build things. So a lot of the science at the NIH that they're doing is funded under the umbrella of pain

research. And these researchers kind of want to get this almost quantum-level view of how we feel things and how we experience our bodies to better understand pain and to better find ways to treat it. There are also potential applications down the road, like you can imagine in robotics, like having robots that have better fluid motion and they can do these complex computations to find out like where their pieces are and all that. There's also applications for prostheses. Scientists are getting better at giving people the ability to control like a prosthetic limb, but you don't close the loop, they're not getting proprioceptive information back from those limbs. And that would be like

really critical. And until we come up with some futuristic technology, these women, can they get around? They actually do have a proprioception of sorts. And the researchers I talked to do say they generate like a three-dimensional map of their bodies. They just do it in a different way than you and me. So you and me are using the muscle spindles and finding out exactly where our limbs are at all times. But these women can use their vision to compensate. If they're looking at their arms or legs, they can do just fine. And they had to learn how to do that. And that's the most remarkable thing the brain does, is compensate. In working on this story and talking to these neuroscientists,

I've begun to think of consciousness as a kind of wizard stirring a potion. You feed into this potion all these senses or sight or vision, proprioception. But it's not like if you're missing an ingredient the potion goes bad. This conjurer will always make consciousness, will always try to generate and compensate. If scientists

can make progress in this area, it can give us answers to the biggest question of all. What does it mean to be a human? After the break, the rest of that potion. And why it's lying to you. to help you save time and put money back in your pocket. Ramp says they give finance teams unprecedented control and insight into company spend. With Ramp, you're able to issue cards to every employee with limits and restrictions

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Today, today X-Line. It's today X-Line. All right, we're back. Noam, we have a better sense of where our bodies are now. What's next? So Brian was talking about how proprioception is just one part of this strange concoction that creates consciousness and basically makes us who we are. Yeah. We've got sight, smell, proprioception, all the senses,

and they're working together to shape our experience. But even when we think they're working perfectly, our senses come with these built-in flaws, which have some scary implications. Scary? Yeah. Take sight, for example. We think of our eyes as these cameras that capture the world exactly as it is.

But our vision doesn't work like a live feed camera. It's actually pretty slow. Sight is slow because it has a lot to do in your brain before it can get put together. So light enters our eyes. It's focused on the retina in the back of your eye. The retina is where we need to take the light and make it into something our brains can understand. So it makes this electrochemical signal.

Your visual processing center is actually all the way in the back of your head. So that signal needs to go to the front of your head to your back of your head. And then once it's in the back of your head, like, it's always communicating with the front of your head, too. And it needs to, like, go through all these different areas

to kind of put a scene together. Like, it looks for edges. It looks for faces. It looks for, like, salience. It looks for, like, understanding and context. It's doing so, so many things, and it's using so many different parts of your brain. It happens in a couple hundred milliseconds.

It's really quick, but it is delayed. It's not just sight that's delayed, though. You are sensing the world on a delay in every respect. Adam Hantman is a researcher who thinks big thoughts about sensory perception. There's no sensory system that's not on a delay. Properceptors are on the shortest delay, and actually vision's on one of the longest delays. Maybe 200 milliseconds, which doesn't sound like a lot, but if you're trying to control your limb and, you know, hit a baseball, you're in trouble

if you're going to try to rely on actually seeing the ball come to your bat. So our brain needs a shortcut. The nervous system invented a new mechanism by which it could get a little extra speed in order for it to try to move better so it doesn't get eaten by the cheetah as many times. Your brain essentially invented a prediction machine. You're like just a learning machine.

You're trying to learn the relationships of the world to future events in the world. You're trying to learn the relationships of commands to actions in your body. Sort of like, you know, the output of a neural network. You've built this understanding over time by learning the relationships between those things. And the fastest thing you can do is work on those relationships, not work on the actual events. When someone throws you a ball, your brain has this prediction machine

that's based on every time you've tried to catch a ball before. And the fastest way to catch it is your prediction machine, not your eyes. But even then, your prediction machine is still a little late. You believe that you are interacting with the world in the present tense. And that's just not really true. In reality, because of the limitations of our nervous system, most of the time you're dealing with guesses about the world, not actually the world. The fact is, we're often just guessing,

which makes it reasonable to start doubting our perception. Perception really starts with just light. Light comes into our eyes. But unless we have some sort of framework to scaffold the stimulations onto, we aren't going to make sense of it. And so in a very real sense, our cognitions are inherently tied into our perceptual experiences. Emily Balchettis, Psychology, NYU.

We are creating informed expectations of what the world is going to look like, and we're updating those as maybe we've thought we understood how far down that step is, and we got it a little bit wrong. So now the next time we step down that flight of stairs, we get it right. For the most part, we're going around this world getting it right. And if it's wrong, it's just slightly so. And we update, and we maybe don't make that mistake again. On a small scale, the worst problem created by your prediction machine might be a missed step. But the problem gets bigger.

I mean, there have been a number of high-profile cases where a police officer engages in an act of force against a civilian. And there's often a debate. What really happened? People's reactions have been, I wish that we just had a video. I wish we could just see for our very own eyes what happened so we don't have to rely on testimony. And now protesters are demanding footage of the shooting be released. And the

police department has that video. Why don't they release it? The bottom line is they want to see that officer's body cam video. But that video evidence that we have all cried out for actually hasn't brought society together. The jury acquitted former officer Michael Rossfeld for the 2018 shooting of the 17-year-old unarmed black teen. The shooting was caught on video and shows Rose and his friend running from police. The police officer says Hammond used his car as a weapon and that he shot in self-defense. But Hammond's family disagrees. I just don't understand how anybody could watch that video and then say not guilty.

Emily's research is showing that videos are an opportunity for our prediction machine to take center stage. Just as important as what we watch is how we watch. And so in an ongoing study, Emily uses videos of altercations between cops and citizens. And we are asking them, what happened in the video? And then we ask them to what happened in the video? And then we ask them to make punishment decisions as they might if they were a juror in a court of law. As you might expect, the people who say they have a lot in common with the cops

say he's justified, and vice versa. What's different about this study, though, is that Emily is tracking their focus. Their eyes are pointed at the very same thing. They're tracking the same person's movements, and yet that's where we see the most polarized decisions. And the weird thing is, if their eyes aren't focused on the cop, their bias, either pro or anti-cop, doesn't come out. If their eyes have instead followed the civilian or tracked the background

or the other objects that are in the scene, there isn't sort of room for their bias to be expressed and for them to maintain the belief that they've made an accurate decision. As part of this research, Emily is nudging people's prediction machines in a different direction, trying to help them see that step on a staircase as just a bit shorter than they might have thought. And she's found that that nudge can be as small as telling people to pay equal attention to the cop and civilian. When before we had seen a pre-existing attitude

predicting a biased punishment decision, that totally goes away. And we're among the first people to demonstrate that this is part of the problem. And the solution may not be, quote, objective video evidence. That isn't going to be the thing that makes us understand truth with 100% certainty.

Because at the end of the day, it's still people that are watching. You can't take bias out of the brain. It's built on bias. What Emily's suggesting is that the best we can do is nudge people into a different perspective. There's this idea called naive realism. And it's the simple idea that however we experience the world, it just feels so true. So, you know, the big viral illusions over the last few years, like the dress, blue and black or white and gold, that's the naive realism that whatever you experience

just feels so real. And it is real, but it's an approximation. It's a guess. And I think what this research should nudge us towards is curiosity. I think at the least, at the very least, the science of perception gives us an extremely interesting challenge for living. Brian says that on the one hand, we know our bodies can do incredible things, like direct our limbs in the dark using this sense most people don't even know they have. But we also know that this impressive machinery is flawed. We know now that our experience of the world isn't perfect. We can prove it.

So what do you personally do with that? For me, that leads me to feeling the value of a more intellectually humble outlook on things. You know, it's up to you to do with it as you do. It's a challenge. Okay, wait. Noam, it's a challenge? Yeah, I think Brian is getting at something really hard here, which is that it's a lot harder than you think to not trust yourself all the time. And so in order to deal with the imperfections of our very human senses, we should challenge ourselves to be more humble.

Yeah, and I think this doesn't just apply to, you know, when we're watching a video of an encounter with police. I mean, this applies to how we think about our relationships, how we deal with conflict, how we deal with really strong beliefs. And, you know, I think if we know that it's so easy for us to be fooled all the time, then I think the best way to go about the world, as hard as it is, is just to be a little less sure of yourself. Well, if you want people to take this challenge seriously, I'm pretty sure you need a hashtag.

I have no idea. The wizard challenge? The humble challenge 2020? Yeah, pour a bucket of humility on your head and see how good that does. That'll do the trick. No, I'm Hasenfeld, producer, reporter, Today Explained. Thanks so much for your reporting on this story. Thanks, Sean.

Today Explained is part of the Vox Media Podcast Network. You can get in touch with us. Our email address is todayexplained at vox.com. We're on Twitter at today underscore explained. The rest of the team includes Bridget McCarthy, Halima Shah, Aminal Saadi, Jillian Weinberger, and Afim Shapiro. The mysterious Breakmaster Cylinder makes music for us, and Cecilia Lay checks our facts, and we had extra help this week from Bird Pinkerton. For more on perception,

Emily Balchettis actually has a book coming out next week. It's called Clearer, Closer, Better, and it's all about how to leverage your own perception. I've been on the road this week, thanks to Little June Sale for letting me turn her Berkeley bedroom into a recording studio for an hour or two.

Thanks to the Stanford Journalism Program for letting me use their podcast cellar. Thanks to Vicky Pike for letting me use her pool. And thanks to Mama Chitz for letting me hang in my old closet. I sense that you're the best, Mom. you