Does touch strengthen your brain? with David Eagleman (Senses Miniseries #1)

0:00This episode is brought to you by Choiceology, an original podcast from Charles Schwab, hosted by Katie Milkman, an award-winning behavioral scientist and author of bestselling book, How to Change. Choiceology is a show about the psychology and economics behind our decisions. Hear true stories from Nobel laureates, authors, athletes, and everyday people about why we do the things we do. Listen to Choiceology at schwab.com slash podcast or wherever you listen. This episode is sponsored by Quince. After a busy summer, there's nothing quite like settling back into your routines and enjoying more meals at home.

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1:14Upgrade your everyday in the kitchen. Download the Quince app for app-exclusive offers or go to quince.com slash tedhealth. Get free shipping on your order and 365-day returns. now available in Canada and the UK too. That's Q-U-I-N-C-E dot com slash TED Health. Today's episode is sponsored by Kashi. Say hi to new Kashi Gut Health Granola, a straightforward, delicious way to fuel your gut made with prebiotics, fiber, and cultures. My favorite flavor, blueberry almond, has perfectly crispy clusters, delicious almonds, and bursts of whole blueberries. It's an easy fit for a daily routine, whether that's for breakfast or a snack.

1:54In a world of overwhelm, it's a straightforward, delicious choice. Try new Kashi Gut Health Granola. This is TED Health, a podcast from TED, and I'm Dr. Shoshana Ungerleiter. I'm a board-certified practicing internal medicine physician, and I'm your host for today's show. We all know about the five senses. It's often one of the first things we learn about in school. I remember reading about them in textbooks or seeing them on posters hanging in my classroom. always with a little icon next to each word. A little hand waving hello, or an unblinking eye, an ear, lips, a nose. It's a really literal way to learn about the senses, and it's effective.

2:36It gets the message across. You need eyes to see, ears to hear, and so on. But the truth is, sensory experiences, both big and small, are much more complex than that. The senses are woven into almost every part of our lives. They shape how we navigate the world, how we relate to other people, and how we make sense of ourselves. So today we're beginning a special series on the five senses. Over the next five episodes, we'll explore touch, sight, hearing, taste, and smell. We'll explore how these senses work, how they shape our lived experiences, and what modern science can teach us about the extraordinary ways our brains interpret the world around us.

3:17And we're starting with touch. when I think about the moments I feel the most alive, when I feel the most connected with the world around me, I think of the little details, the warm sunlight coming through a window, the comfort of someone squeezing your hand, the shock of stepping into cold air, even the familiar buzz of your phone before you look to see who's calling. And at the heart of it all is touch. Touch is something we often take for granted, but it's fundamental to being human. It can calm us, warn us, connect us, and even help us learn. Touch may also be capable of far more than we once imagined.

3:57My guest today is David Eagleman, a neuroscientist at Stanford University whose work explores brain plasticity, perception, and the remarkable flexibility of the human brain. You may know him from his books like Live Wired and Incognito, The Secret Lives of the Brain. He also hosted the PBS series The Brain with David Eagleman. David's work challenges the idea that our senses are fixed. Instead, he argues that the brain is far more adaptable and more creative than we tend to realize. And what I love about David's work is that it connects cutting-edge neuroscience with bigger questions that shape our lives.

4:35What does it really mean to perceive the world? How much of reality are we missing? And how might technology change the boundaries of human sensation in the years ahead? In our conversation, we talk about why touch is so essential for emotional and physical health, and how new forms of sensory technology could reshape the future of medicine and communication.

5:02David Eagleman, welcome to TED Health. Thank you. Great to be here. So when most of us think about touch, we think about physical sensation. But from a neuroscience perspective, what role does touch really play in helping us feel safe and connected and really human? So, you know, the reason we have touch in the first place is because your brain, which is the command center of the whole operation, is about three pounds and it's locked in silence in the dungeon of your skull. And it's controlling this massive body and it needs to get feedback from that body. It needs to know what's going on in the world out there with what it's communicating with physically and what signals it's getting back.

5:48Is this hot? Is this spiky? Is this cold? And so on. So what we have in our skin, which is the largest organ of the body, we've got this whole zoo of touch receptors. These are picking up on things like pressure or itch or temperature or stretch, all kinds of things. And these are bringing information back to the brain. So that's why we have this from an informational point of view. From a developmental point of view, what's very interesting is that we really require touch. Just as one example, after the fall of Ceaușescu in Romania, there were tens of thousands of kids who were orphaned and they were in these orphanages and the orphanages were just too crowded.

6:34They were overpacked. And so the staff said, look, if you touch the kids and you talk to them, they get too clingy. So we're not going to do that. We're not going to touch them and we're not going to talk to them. And these children developed with major cognitive problems because the brain needs lots of touch, lots of loving touch from a parent. you know, all over the skin so that you get these feelings in and it actually helps you wire up the map of your body when you're doing that. This is how we know that touch is very important from all these points of view. Yeah, I think that's such a helpful framing that touch isn't just a sensation, right?

7:14But part of the brain's social and emotional architecture. And it makes me think about the moments when touch seems to matter most. you touched on this, right? Especially in medicine and in caregiving as a physician, you know, I've seen how something as simple as touching a patient's hand can completely shift the emotional tone of maybe a difficult moment. So I want to dig into this. What does neuroscience tell us about why touch can be so calming or reassuring and important in the developmental process in real life? I think the importance of the developmental process has to do with allowing the brain to wire itself up because what the brain has is a map of the body in the brain.

7:56And people, when they originally discover that, this must be genetically determined. This is called the homunculus, the little man. But it turns out it's not genetically determined. It wires up because of activity in the body. So when you're touching the body, it turns out that the way the brain's able to make this map is because two neighboring points on the skin tend to be co-activated. Like it's much more likely that these would get touched at the same time rather than, you know, your elbow and your knee are less likely to get touched at the same time. So things that fire together, wire together, and what you get out of this is this map of the body.

8:36So that's developmentally. As far as why it's important for touch and love and communication, that drifts from the neuroscience into the realm of poetry. But, you know, again, brains are lonely and locked in these little chambers. And this is your way of communicating with another being. It's presumably the most primitive way of communicating with another brain. And you see this all through the animal kingdom. Animals will rub up against one another and tuck themselves into each other. I was just watching some tigers doing this. It just happened. I was watching this on YouTube the other day. And it's so great to watch because we empathize with them.

9:15We immediately put ourselves in their shoes and just feel so nice to touch and be touched. So if touch is shaping us that deeply every day, it seems like it also might offer us a window into something larger about how the brain learns and adapts. And I think that brings us to the idea of plasticity. And you've written a lot about brain plasticity, the idea that the brain is constantly adapting. So in plain English, what does touch teach us about how flexible the brain really is? Yeah, well, let's come back to this example about the homunculus, this little map of the body. There was actually a famous case that happened called the Silver Spring Monkeys, Silver Springs, Maryland.

9:57A researcher named Edward Taub in the 1970s was looking at what happens if he cut a nerve so that a monkey couldn't use its arm. And he was looking at how you could rehabilitate the monkey, what the best strategies were. But what happened was the animal rights group PETA had just started and a spy from PETA came into his lab and he took photographs and he brought this to the courts. And so what happened is for years, there were all these legal battles going on about whether Dr. Taub could continue these experiments or not. Now, what happened is during this court battle, one of the monkeys was going to die.

10:40And so some researchers petitioned the court and said, can we study what's going on in this monkey's brain? Because it's going to pass away anyway. And what they found from this is that the monkey's map of its body had changed. Because it couldn't use its arm anymore, the map no longer included that arm. And that's when we first started to realize, oh, the brain is really plastic and it is dynamically representing what the body looks like. We know a lot about brain plasticity, specifically from the touch that comes into the body. You've mentioned that the brain may be more sensory agnostic than we once thought.

11:18What does this mean and how does that change the way we think about maybe disability or rehabilitation or even human potential? Yeah. So it is exactly right that the brain doesn't care where the data comes from when it comes to sensory data. You've got these spheres embedded in your skull that we call eyes that are capturing photons and turning those photons into spikes, electrical spikes that travel into the darkness of the brain. You have eardrums that vibrate with air compression waves. Your inner ear turns that information into spikes that travel into the darkness of the brain. Your skin is full of all these receptors that translate information into spikes.

12:01So all you have in the brain are these electrical spikes running around. And the brain doesn't know and it doesn't care where those spikes come from. It just figures out what it can do with them. What is the maximally useful thing to do? And so it is the case that if you look at a neuroscience textbook 20 years ago or something, you know, it says, look, this part's for vision, this part's for hearing, this part's for touch, and so on. But what we know is that the whole system is much more flexible than that. For example, if you go blind, the area that we call the visual cortex will get taken over by hearing and touch and other things.

12:35If you go deaf, the part that we think of as the auditory cortex gets taken over for other tasks and so on. So the whole system is very plastic. And this led me to studies that I started in my lab 15 years ago, which was the question of, can we feed information into the brain via unusual channels and have that replace, let's say, a lost sense? This is the idea of sensory substitution. You're getting information into the brain in a way that, you know, it's not used to getting it, but as long as it gets the information, the question is, can it do something useful with it. So what we did in my lab is, for example, for people who are deaf, we built a vest with vibratory motors all over it.

13:18And the vest captures sound and breaks that sound up from high to low frequencies. And then it sends that up to the brain via vibration on the skin. So you're feeling vibration in different parts of your torso. And that is sending this information up to your brain about the sound of the world. Now, the reason it's so easy for the brain to learn this stuff is because all it's looking for is correlations. So it sees somebody's mouth move, and it hears the sound, or in this case, you feel the vibrations on your skin. And it says, oh, those two things must go together. By the way, this is how you learned how to use your ears when you were a child.

13:53When you were an infant, you're clapping, you're hitting the bars of the crib, you're doing whatever, and your brain is putting these things together. You see your mother's mouth move, and you have activity at your eardrums. And so that's how your brain puts this all together. Anyway, we were able to show that you can learn information coming in through touch that would substitute for a lost sense like hearing.

14:19We'll be right back with more of my interview after this quick break. Today's episode is sponsored by Kashi. Say hi to new Kashi Gut Health Granola, a straightforward, delicious way to fuel your gut made with prebiotics, fiber, and cultures. My favorite flavor, blueberry almond, has perfectly crispy clusters, delicious almonds, and bursts of whole blueberries. It's an easy fit for a daily routine, whether that's for breakfast or a snack. In a world of overwhelm, it's a straightforward, delicious choice. Try new Kashi Gut Health Granola.

14:55This episode is brought to you by Choiceology, an original podcast from Charles Schwab. Hosted by Katie Milkman, an award-winning behavioral scientist and author of best-selling book, How to Change, Choiceology is a show about the psychology and economics behind our decisions. Hear true stories from Nobel laureates, authors, athletes, and everyday people about why we do the things we do. Listen to Choiceology at schwab.com slash podcast or wherever you listen. Okay.

15:39David, I'm curious what happened when people actually started using these systems. What surprised you most about how quickly people's brains learned to interpret those signals? Well, what's interesting is that in some cases it was quick, in some cases it was slow. Here's an example. When it comes to people who are deaf, who are born deaf, it takes them a while. So they just get better every day, and it's a long, linear climb as they get better and better at distinguishing sounds from one another. One thing that was cool and surprising there was just learning all the sounds of our world that people who are deaf don't realize are there, like that microwaves beep or that car blinkers make a sound, things like that.

16:19They just didn't know that. And now that they had this technology, they were suddenly picking up on all kinds of things or like a toilet flushing, how loud that is. Most people didn't realize that if they were deaf. Okay, there's that. But we also did things with people who are blind. So we took LiDAR cameras and with that, we could tell the location of everything in the room in real time. And we put this vest on a person who is blind and he can now feel where everybody is. So if you're approaching him on his left, he can feel a vibration on his left and it's getting more and more intense as you're getting closer.

16:53And then if you go around behind him, he feels you moving around behind him. And, you know, he's essentially got 360 degree vision, which is better than what a sighted person has. He can tell exactly where people are moving and what's going on. The remarkable thing about that is there was zero learning curve there. And this brought me back to a question that I'd read from Immanuel Kant, the philosopher, when I was 20 years old, about this question of whether space is inherently something we understand or whether it's something we need to learn. And what this suggested is that for a blind person, the three-dimensional space was just something that was totally clear and easy to them, even though they'd never felt it before, they'd never seen it, they were nonetheless able to get that immediately with no extra learning required.

17:39So different things required different amounts of learning. Oh, fascinating. Stories like that can make the brain seem almost limitless in its adaptability. And at the same time, right, every scientific advance comes with important questions about where those boundaries actually are. Yeah. What do we know so far about the limits of the brain's ability to adapt and what scientists are still learning? So many things. One thing is, as the brain ages, it gets less and less plastic. Now, that might seem like a bad thing, but that actually represents a good thing, which is that you're figuring out how to operate in the world.

18:15The job of the brain is just to make an internal model of what is going on out there. And the better and better you get at that, as in, okay, here's how to walk, here's how to eat, here's how to talk to people. Here's how to drive a car and use a cell phone. The better you get at that, the more your brain is kind of locking into place and it's harder to adjust that. But what it represents is this transition from fluid intelligence as a baby to crystallized intelligence as an adult. So that's good that we can learn stuff and retain it. The bad news is that as people get older and older, it's harder to make plastic changes in their brains.

18:49What we do know, though, is that it all pivots on motivation and relevance. And let me give you a specific example. Let's say someone's had a stroke and they've lost the ability to use their left arm. The most important strategy we have is what's called constraint therapy, where you take their good right arm and you tie it down, you lock it down to their chest so they can't use their right arm. And now they have to use their left arm if they want to get the food to their mouth or if they want to get their pants down to go to the bathroom, or if they want to grab a cup of coffee. So they have to use their left arm.

19:28And this, it turns out, is the trick for making sure that their brain does the right moves to make the plasticity happen, and they can learn how to use their left arm again. But if you leave them with the capacity to use their right arm, then they're just not going to use the left one. So this is what I mean by making something relevant, or by motivating somebody is you have to make it tough for them where the only option they have is to take the weak arm and use it. Yeah, oh my goodness. But I can imagine how frustrating that probably feels for that person when they're like, I can't do it yet.

20:04Yes. I wanna talk a little bit about health technology. So a lot of new health technologies promise transformation, right? We talk about this on this show. You tend to speak about these ideas with both excitement and caution. What are the guardrails that matter most as we develop technologies that interact directly with perception? Yeah, I've been asked this a lot about my haptic technology. What's interesting is that it's really no different than headphones or a television set in that you're just putting information in through these senses. With headphones, you're just sticking information into ears.

20:44when I listen to Audible every day and I'm putting information in. I look at a YouTube screen, I'm putting information into my visual. It's the same thing with these haptic technologies. You're just putting information in through your sense of touch. So I think in that sense, the only thing we want to just generally keep an eye on is making sure we don't put bad information. For example, I don't watch horror movies because then I get nightmares later. But I think the ethical dimension is actually pretty limited here. It's a different question if you're asking about, let's say, doing an open head neurosurgery and implanting things into the brain, there you've got all the questions of how do you know that you can take it back out and that it'll work and then it won't cause infection and all that stuff.

21:25But in this case, I think it's pretty straightforward. That's a good framing here. And what's interesting is that while we're looking at cutting edge technologies, we're also talking about one of the oldest and most universal human experiences. And sometimes the most profound things are hiding in plain sight. And in my work with patients and families, especially during emotionally intense moments, touch often becomes one of the last and most meaningful forms of communication. Why do you think we sometimes overlook how powerful touch can be? You know, there's so much social meaning attached to touch.

22:02We're always caught in this thing of like trying to be really careful about not touching somebody who doesn't want to be touched. And on the one hand, for a lot of social reasons, we can see why that's good. And on the other hand, for this sort of very basic reason that you just brought up, we can also see what we're missing in society. I mean, you know, when you look at these tigers or cats or monkeys or whatever, they're always touching and rolling around with each other and just being in contact. And it's so lovely. And if you go to Burning Man, the people have cuddle puddles and stuff like that, where they just, it's not a sexual thing.

22:36Everybody's just touching and being in contact. And that's, I do feel that is missing a lot from our modern life. You know, part of why I realized there was this opportunity with this haptic technology is because I mentioned the skin is the largest organ of our body, but it goes wasted in modern life. And we really use it for very little. There's too little touch. So obviously it has to be with all the social guardrails to make sure people aren't uncomfortable, whatever. But for a physician, for example, laying hands on the patient, wonderful. For being at somebody's bedside when they're in their last days, holding onto their hand, wonderful.

23:13It's just, it's such an important part of how human brains work and what they expect in the world. That makes me wonder whether touch has become more valuable precisely because so much of modern life now happens through screens and devices. In a world that's increasingly digital, what role is touch playing in our lives? now compared to the past. I mean, what's interesting is when I think about, let's say, 100 years ago, was there more touching? I mean, if we worked on a factory and an assembly line, it's not necessarily the case that there was more touching. But certainly, if I think 500 years ago, I believe there was, mostly because families lived in very small little things, and often they would sort of share sleeping arrangement, where everyone was just sleeping together, all piled up like the tigers and how great.

24:03I mean, it's impossible to know since we don't have brain imaging from 500 years ago, what effect that would have. But I mean, imagine for a little kid growing up to sleep with the parents where they're constantly in contact or they've got a leg over them or an arm or whatever. What a great thing. We'll be right back with more of my interview after this quick break.

24:28This episode is brought to you by Choiceology, an original podcast from Charles Schwab. Hosted by Katie Milkman, an award-winning behavioral scientist and author of best-selling book, How to Change, Choiceology is a show about the psychology and economics behind our decisions. Hear true stories from Nobel laureates, authors, athletes, and everyday people about why we do the things we do. Listen to Choiceology at schwab.com slash podcast or wherever you listen. Hi, this is Becca Moore from For the Girls and this podcast is sponsored by Aerie, where you can find the right bra in 59 sizes, soft fabrics and good fits.

25:06If your bra strap is digging into your shoulder right now, it's the wrong bra. We get so used to being in pain as girls that we forget it doesn't have to be this way. Your clothes should not hurt. I got to the point where I stopped wearing bras altogether and now my life has changed, you guys. The only bras I have in my dresser right now are Aerie and I'm not kidding. Aerie's on a mission to make you feel good and that starts with your bra. Your bra should hold you in not back. Visit aerie.com to find the right bra for you.

25:42I'm always curious about the personal side of the story and I'm curious how this work has shaped your own life? Has studying touch and perception changed the way you connect with your family or your relationships or even the way that you move through ordinary moments? I mean, I think I've always been a hugger. I have two kids, 10 and 14, and I always hug them. I just, I love being in contact with them. I'm always hugging my wife. She's less of a toucher and so it probably drives her crazy. But I don't know if that's a result of my research or maybe my research stemmed from my love of touch. If somebody listening wants to become more aware of their sensory world, especially touch, is there a simple practice or maybe a mindset shift that you'd recommend starting with?

26:25I mean, the general thing is to attend to what is going on. So that's with touch, but also hearing and sight. You know, if you have an opportunity to go into a forest and sit and be aware of how the ground feels or the bark of a tree or the leaf of a plant or things like that and what it looks like and what sounds you're hearing. This is just generally one of the best things we can do in a modern world with a lot of Zoom calls and so on is to really spend time having sensory awareness. It turns out that because the job of the brain is to make an internal model of the world, it essentially says, yeah, I already know that.

27:08I know that. I don't need to pay attention to that. Which is why, for example, when you drive home from work every day, the drive seems shorter and shorter. Because the very first time you drove to work, it seemed to take a long time, but you become an automatized zombie on your drive and you're thinking about other things, not really paying attention anymore. So one thing I try to do is drive a different route home every day. I just always try to take different streets. And what I'm not telling you is how to live longer here. I'm telling you how to make it seem as though you've lived longer because now you're attending.

27:40Now you're in the present moment and you're paying attention to what's going on around you. Oh, I love that. And I'm somebody who's like directionally challenged. So I can imagine if I'm driving home a different way, that might be a problem if I'm paying attention to other things. But that's a really fascinating idea. Well, I know we haven't talked too much about what you're currently working on. But I would love to hear what's going on in your lab right now. What are you excited about? What I'm doing now is building a device for elderly people who want to stay in their own homes. So it's a little tiny robot that is both conversational, but it's also doing all these medical things under the hood.

28:20So it's constantly getting conversation out of you by forcing you to talk and being a good companion that way. But what it's really doing is monitoring all kinds of things in terms of whether you've had a stroke on a longer time scale, whether you're going into mild cognitive impairment, all sorts of things. And it can advise you and steer you. And I just feel like it's so important for people who want to stay at home to be able to have help doing that and have something that is there, keeping an eye on them, total privacy first, you know, nothing going off to a company, but it's able to keep them healthy.

28:54Oh, fantastic. Where can people learn more about that? Jojo.health is the website. Fantastic. So what do you hope people carry with them after thinking more deeply about touch, not just from the scientific perspective, but as part of living a more full life? It's just, it's important to figure out how to attend to what we're touching. I have a friend who got into olfaction recently, into smelling. So he bought a whole thing of different scents and he sits there and smells them all. He's 70 years old. It's just something he's doing. and I feel like we can always pay more attention with touch, just putting things between our fingers.

29:29Our fingers are such a remarkably dense set of receptors to pick up on information from the world and we can just touch everything around us and see what information we're getting that way. David, thank you. You've reminded us that touch isn't just something that we experience. I think it's one of the ways we understand ourselves and each other and the world around us, certainly. So I'm really grateful for your time and for helping us feel the science as much as understand it. Great. Thank you so much, Shoshana.

30:07Thanks again to Dr. David Eagleman for joining us today. And that's our show for today. Stay tuned for next week's episode in our mini-series on the senses. It's about the art and science of taste. I hope you'll join us. TED Health is a podcast from TED and I'd love to hear your thoughts about this episode send me a message on Instagram at ShoshanaMD this episode was produced by me Shoshana Unkerleiter and Jess Shane edited by Alejandra Salazar and fact-checked by Vanessa Garcia-Woodworth special thanks to Maria Lages Farrah Degrunge Daniela Balarezo Constanza Gallardo Tansika Sangmarniwang and Roxanne High Lash

30:58This episode is brought to you by Choiceology, an original podcast from Charles Schwab. Hosted by Katie Milkman, an award-winning behavioral scientist and author of best-selling book, How to Change, Choiceology is a show about the psychology and economics behind our decisions. Hear true stories from Nobel laureates, authors, athletes, and everyday people about why we do the things we do. Listen to Choiceology at schwab.com slash podcast or wherever you listen. Hi, this is Becca Moore from For the Girls, and this podcast is sponsored by Aerie, where you can find the right bra in 59 sizes, soft fabrics, and good fits.

31:36If your bra strap is digging into your shoulder right now, it's the wrong bra. We get so used to being in pain as girls that we forget it doesn't have to be this way. Your clothes should not hurt. I got to the point where I stopped wearing bras altogether and now my life has changed You guys the only bras I have in my dresser right now are aerie and i'm not kidding Aries on a mission to make you feel good and that starts with your bra Your bra should hold you in not back visit aerie.com to find the right bra for you