in: Fitness, Health & Fitness, Podcast

• Last updated: September 30, 2021

Podcast #599: The Physical Intelligence That Helps You Take Action

Ever wonder why you don’t walk into walls? How you know you have to step gingerly on ice? How you decide whether you can or can’t scale a certain rock? My guest today says the answer lies in our special sense of bodily know-how. His name is Scott Grafton, and he’s a neurologist and the author of Physical Intelligence: The Science of How the Body and the Mind Guide Each Other Through Life. We begin our conversation discussing how physical intelligence is the mutually responsive interaction between your body and your mind that allows you to interact effectively in the world. Scott then explains how our mind and body work together to build our conception of space and that without this ability we couldn’t create an area of operations in which to take action. We then discuss how our mind and body communicate with various types of terrain, how we can lose that ability by limiting our movements to simple, safe environments, and how that may explain why old people fall down more. We then discuss how problem-solving can be a very physical activity and whether the feeling of fatigue is more a matter of the body or the mind. We end our conversation discussing ways you can keep your physical intelligence sharp as you age. 

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Show Highlights

  • What is “physical intelligence”?
  • What is it that makes us human? What fulfills us most?
  • How our brain constructs the concept of space around us
  • What happens to people who have lost this ability?
  • Why do older people fall down, even when they have good strength?
  • What is “body schema”?
  • What bears can teach us about physical intelligence
  • What causes fatigue?

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Read the Transcript

Brett McKay: Brett McKay here and welcome to another edition of Art of Manliness Podcast. You ever wonder why you don’t walk into walls, how you know you have to step gingerly on ice, how you decide whether you can or can’t scale a certain rock? Well, my guest today says the answer lies in our special sense of bodily know how. His name is Scott Grafton and he’s an neurologist, and the author of physical intelligence, the science of how the body and mind guide each other through life. We begin our conversation discussing how physical intelligence is the mutually responsive interaction between your body and your mind that allows you to interact effectively in the world. Scott then explains how our mind and body work together to build our conception of space and that without this ability, we couldn’t create an area of operations in which to take action. We then discuss how are mind and body communicate with various types of terrain, how we can lose that ability by limiting our movements to simple safe environments, and how that may explain why old people fall down more.

We then discuss how problem-solving can be a very physical activity, and whether the feeling of fatigue is more of a matter of the body or the mind, and we end conversation discussing ways you can keep your physical intelligent sharp as you age. After the show’s over, check out our show notes at

Alright, Scott Grafton welcome to the show.

Scott Grafton: Well, thanks for having me, this is exciting.

Brett McKay: So you just came out with a new book called Physical Intelligence: The Science of How the Body and the Mind Guide Each Other Through Life. Before we talk about the book, let’s talk about your background ’cause you’re a neuroscientist, but it seems like you’ve focused on how the mind and body interact with one another.

Scott Grafton: Right. My background is actually, I started as a neurologist and went to medical school, have taken care of a lot of patients with neurologic problems, and when you do that it’s hard to separate mind and body. Patients come in with problems that are centered in the brain but really it’s… The problems involve both mind and body inevitably. And so just being a clinician and working with patients, you invariably think of the whole person and that just kind of frames the way you see the world. Then I got into brain imaging and was sort of an early pioneer and using functional brain scans to understand how the brain works and there too, it’s kinda amazing. You’re looking at these images of brains of living people thinking and doing things. So again, you kinda get this holistic view of the person both in terms of what they do and how their mind is working.

Brett McKay: So you’ve seen first-hand Descartes Error, the separation between mind and body?

Scott Grafton: Yeah, I see that as… That’s just, to me that’s an illusion created by the way we use language and the way our mind creates concepts. We create concepts of objects and things like bodies and we create very different kinds of concepts that are more abstract like minds and those inevitably get sort of separated at almost categorical level, but they’re never really actually separated in a brain.

Brett McKay: And as we’ll see in our conversation, what I thought was really interesting about this book is you’ll show how, we’ll talk about how the mind influences the body but also how the body influences the mind. And it’s just almost this cycle you can’t even disconnect from each other.

Scott Grafton: That’s right.

Brett McKay: Alright, let’s talk about this idea of physical intelligence. What do you mean by that?

Scott Grafton: Well, this is The Art of Manliness Podcast, so if you’re thinking about manliness as a set up here, one of the core ingredients I think of manliness sort of classically defined as action. A man of action, or the concept of what makes a person great in some sense is what they do, the actions they enable and the things they do in their world. And physical intelligence is just the underbelly of that. It’s the underpinnings you need to actually get things done. We don’t have a manliness area in our brain, we don’t have a isolated action area in our brain, we have lots and lots of parts or systems that together allow us to do great things with our bodies. Both sports-like activities or sort of extravagant physical behavior but also just creative things. Building a house, pouring a slab of cement, whatever it is, that’s the stuff of physical intelligence.

Brett McKay: Well, speaking of physical intelligence and manliness what I love about this book is that you explore these ideas of physical, these different concepts of physical intelligence by taking readers along with you on a backpacking trip you did in the Sierra Nevada and this isn’t just like a stroll. The way you describe it, it sounds very strenuous, very hard, very perilous. Before we get into why you chose that as sort of a framework for explaining these concepts, talk about how did you get into backpacking personally, how long have you been doing it?

Scott Grafton: I started high altitude mountaineering and rock climbing in high school. And by the time I was 16, I was climbing the face of Half Dome and I was really an enthusiastic climber. And there was a decision point where I was, “Are you gonna become a climbing bum or a dirt bag climber? Are you gonna go to college and go off to Medical School?” And I chose the latter. I kinda miss the dirt bag life ever since, so that’s real dualism for me. And so the way I get… To be a really good high altitude climber or any kind of rock climber, you gotta put a lot of time in it. And so as I grew older, I swapped in walking in the wilderness for the more extreme kinds of climbing ’cause I think what I savour the most is just being in very wild places.

Brett McKay: And so why did you decide to use frame your book and explain these concepts with this backpacking story?

Scott Grafton: Physical intelligence is one of those sort of magic capacities we have. Just sort of automatic and operates under the hood, and we don’t have much conscious access to the bits that are needed for physical intelligence, and so I wanted to create a set up where I’m in a place that’s very demanding, physically, that there is risk and that the problems, the physical problems are really clear and they’re unclouded by conversations with other people, social media, technology, it’s just pure raw human in the world and that’s a nice place to just reveal what physical intelligence is and also sort of what we evolved from.

Brett McKay: And I think one of the points you make about physical intelligence in the beginning of the book is that, physical intelligence really is what, often times we think that what makes us human, is that we think, but a big part of what makes us human, is our ability to act in the world and interact with the world.

Scott Grafton: That’s right. Just talk to anyone and say what’s the most satisfying thing you’ve done or experienced in the last month? And invariably, it’ll be something they did physically. It doesn’t have to be a super human feat or extreme sports, it could just be… I remember my daughter in middle school, she made a bird house in wood shop. She couldn’t have been happier. She was so satisfied with that activity compared to anything she’d done in terms of school work, so that’s the stuff that really, is the stuff that makes us happiest. And that’s what we evolved from. We didn’t evolve to sit around and talk or read books. That’s icing on the cake. We evolved from rough and tumble environments where we had to find food build shelter and find our way through vast rough environments, and we did that up until very recently, only about a thousand years ago.

Brett McKay: So the first concept you explore in physical intelligence is our ability to construct a sense of space and as you said, physical intelligence is one of those things that it’s going on under the hood. We often don’t even think about it, we don’t even know it’s going on. This chapter on how we construct space around us, it kind of blew my mind ’cause you talk about what’s going on all the same time to give us an idea of what’s in our environment.

Scott Grafton: Right. A good example of this would be, if you think of a worm crawling towards some food, it has no sense of space, it just has some sensors that are drawing its movements towards that food. Now I can say to you, “Okay I want you to think of how you would walk across the room.” So you have immediately created an operational space, the size of the room. But then I can say, “Think about walking to the other side of the house, think about walking across the street, think about walking across to the other side of the city you’re in.” In those moments, you’ve expanded your operational space, you can mentally stretch out and construct any of those volumes of space, and then plan and organize your action inside that volume. It’s amazing that you can do that and you have to do it. Just as a search and rescue team, doesn’t just willy-nilly wander into the wilderness looking for someone. They create a map and they lay out a grid and they say, “This is what we’re gonna do here. We’re gonna first set constraints on the space we wanna work in.” We do this all the time, mentally when we’re moving and acting in our environments.

Brett McKay: And the example you give in this chapter, is about just being in a tent, you’re down for the night and you talk about what is going on in your mind as your mind’s figuring out what to pay attention to and what not to pay attention to so you could hear rustling and your mind automatically knew, was like, “Well, that’s not a bear, it’s probably just a raccoon.” How’s our brain able to do that?

Scott Grafton: Well, I wish I knew. [chuckle] It’s funny, we can… A lot of this is phenomenology we can describe or we can measure in the lab, but there’s still a lot of magic about how brain circuits actually calculate and what the computation is inside the head that allows us to do this, what the algorithms are that enable this capacity. We know we have it… At a certain level, we really understand a lot, we know a lot about how the brain can zoom and filter and narrow in attention. We know far less about how it expands attention, how it can become more vigilant and bringing actually more information in these wild environments.

Brett McKay: So as a neurologist, you’ve probably seen people who’ve lost this ability. What happens to those individuals?

Scott Grafton: Well, the most dramatic example is patients with focal damage to the right brain, posterior right brain develop what’s called neglect and the word neglect is a little bit misleading. What they’ll do is ignore, unconsciously ignore the left side of the world and it can be quite severe. I refer to it as the most severe cases. It’s like a black hole, space simply isn’t created in the left side of their environment, in their mind. And so, if you’re standing there and talking, if you’re on the left side of their bed talking to them, you don’t exist, and then you walk around to the right side of their bed and they go, “Oh, hello. How are you doing? Oh you’re there.” So literally on one side of the bed there is a reality for them, and the other side, there is no reality, there’s no nothing there and there’s variations of this, and there’s minor forms that are more subtle.

It’s been called neglect for over 50 years, but it’s not like they’re intentionally neglecting that space, they can’t cook it up in the first place. So that just tells you at some point you gotta make space. If you’re gonna do this stuff we do as humans, one of the very first steps is making some kinda sense of space, ’cause if you don’t make it, you don’t interact in it you don’t reach into it, it’s just not there, you don’t move anywhere near it. The other thing about space, I think that’s really important to remember is, there’s a very strong argument in the cognitive developmental literature that it’s the way… When you’re a baby and then a child and you’re moving through space, it’s your understanding of what you can do in space that really shapes much of how you think, in other words we think spatially. If I think about relationships between ideas, I can put them in a row, spatially and organize them in my mind and space. People like Einstein are well known to have thought through their ideas in terms of spatial relationships, the physical spatial relationships. So much of how we construct the world is spatial.

Brett McKay: You’re talking about some people have these problems where they just go completely blank on a certain side. Is it possible for this ability to make space in our mind? Can that be dulled from just not using it on a regular basis?

Scott Grafton: I don’t know. I think… Well, what gets dulled is our ability to control how we’re gonna use attention in our environments. We’re pretty good at cooking up space in our minds. But the next step is, where are you gonna place your attention? And that actually can get dulled or it can get distracted, where it can never develop well in the first place and then you get attention deficit disorders and things like that. And clearly, meditation and mindfulness, and doing things in wild environments, all train us to be more disciplined in how we allocate our attention.

Brett McKay: So another idea, you talk about physical intelligences is that, both our mind and our body, we might not even know this when I think about it, but we’re kind of communicating with the environment around us. I use communicate like in quotation marks, but you talk about this idea of affordances, like an object or a surface can have an affordance and that tells something to our mind and body. I thought this is really interesting, can you elaborate on this idea?

Scott Grafton: So for surfaces I was thinking about, here’s a good example, I think everybody is familiar with the Half Dome in Yosemite Valley, it’s this big granite dome, and there’s the vertical face but then there’s the rounded faces on the side and the hikers goes up the rounded side and the surface, it’s just smooth granite, and it gets steeper and steeper and steeper, until… And you’re walking up this and there’s a point at which you begin to doubt whether your feet will even stick anymore ’cause it’s getting so steep. Can you continue to walk up this slope? And it gets scary because you are way off the deck, and that’s an affordances. It’s your relationship with the slope and it’s as pure and simple as it could be. Can you maintain footing and continue up this dome. Now, on flat surfaces, you can think about icy surfaces or slopes that are covered with marble, round rocks, things like that.

Can you maintain your footing? So those are kind of surface ideas. And then the more elaborative version of the same thing is, can you fit between two trees, if you’re just walking along and there’s… You’re in a dense forest, can you squeeze between two trees? That’s an affordance, that’s an opportunity, it’s this idea that the environment creates what’s possible and what’s impossible for you. We don’t accidentally walk into trees, and then around them. Our mind unconsciously and seamlessly just recognizes, this is an obstruction, this is something I cannot get through and it’s looking for opportunities in the environment that it can accomplish or can get through. It’s a little bit like a kayaker who’s weaving through the gates. They’re just seeing these… The gates are opportunities for how they’re gonna move in their environment, and we do this all the time, seamlessly.

And if you don’t have that, you walk into walls. [chuckle] You don’t understand the three-dimensional relationships between objects, just something on the floor in front of you, it can completely stymie your ability to move forward. So it’s an essential capacity and vision and it’s almost completely ignored in neuroscience. What we look at is, how we recognize objects or how we name things, or how we categorize things, but there’s very little work on how we understand the 3D world and navigate through it physically.

Brett McKay: It sounds like you can be more adept with some affordances than others. For example, the mountaineering you probably recognize affordances there on the mountain that some person who has never done that before, they wouldn’t be able to recognize that.

Scott Grafton: Totally. If you think about what are the ingredients that make a great athlete or a person adept at any skill, we always think about sort of the motor side, of like how graceful are they at movement. But just as important is their really precise knowledge about what’s possible and what’s impossible to do. Downhill skier knows really well what kinda slopes require what kind of movements, what’s possible, what’s impossible, and as you develop experience, all those affordances evolve with you. Yeah, a climber, a climber sees opportunity that a novice just doesn’t even know exists. They see handholds that we don’t see and so forth. So we all do this through experience, we completely change how we understand and perceive opportunities in the environment.

Brett McKay: And then something you highlight in this book that this ability to recognize affordances, this can actually dull and it might explain why old people fall down a lot as they get older.

Scott Grafton: Right. So this is a radical departure from the medical model that’s out there right now, which is the reason people fall is ’cause they can’t see, they’re weak or they have problems with the balance organs. So it’s either they can’t sense or they can’t… Or they’re weak. But lots of people fall down that are strong, that can see. [chuckle] They have good balance. So, why are they… Why are so many people falling? Remember falling is the number one reason people go to emergency rooms and it’s old people, young people, everybody’s falling down all that time, it’s amazing how many people fall. Probably every listener you have has fallen in a awkward circumstance somewhere along the way. And so you have to think there’s something else going on that’s making us fall and the affordance ideas is really that you get rusty. And that’s true with climbing, if you’ve been a climber for a while and you go away from it, you don’t know what’s possible anymore, you’ve gotta relearn what kinda handholds work for you, what kinda footholds work.

If you haven’t been walking much, it’s amazing. You actually kinda lose your skill of simply walking and then… And so you become more vulnerable to like a crack in the sidewalk, you’re more likely to trip on that. Just really simple little things can fool us. And so it actually leads to sort of a radical view about what to do with aging, which is kinda the opposite of what a lot of people recommended. People say, “Well, you gotta be super safe, you shouldn’t go on anything rough, you should only be on surfaces like linoleum floors like you’d find in the local mall.” Yeah, so that you absolutely minimize your risk of tripping on anything.

And the affordance idea would actually kinda argue the opposite, it would say, “Throughout life especially as you age, you should continue to constantly challenge yourself, giving your strength and vision which you have on the roughest surfaces you have. You should be out walking on gravel roads, you should be on trails rather than perfectly smooth sidewalks, change it up. The more variety and complexity there is in the kinds of surfaces you’re walking on, the more adapted you are and less likely to fall.” I always like to think of those 100-year-old Greek ladies on the islands going up and down the cliffs, no problem, they seem to be living forever and not falling at all. [chuckle] They’re there, they’re perfectly adapted to these really wild environments and the rest of us kinda forget about how valuable that is.

Brett McKay: And as you said, this doesn’t just happen to old people. I guess you’re seeing a lot of young people, because they’re not engaging with complex environments outdoors, they’re just… All they see is their house and maybe the playground asphalt, and the school floor, and that’s it. And then they encounter some sort of weird affordance, they don’t know how to deal with it and they fall down and sprain a wrist.

Scott Grafton: Yeah. The reality is everything we learn motorically, we’re also kinda unlearning, not completely. Once you learn to ride a bicycle, you know how to ride a bike, but if you haven’t ridden a bicycle in 10 years and you get on a bicycle, you’ll… Actually if you measure the person’s movements, they’re a little sloppy at it at first. It takes some… There’s relearning, there’s constant forgetting and relearning and adding grace and elegance to any kind of action or movement. So it’s really important I think to continue sort of this kinda general physicality throughout life.

Brett McKay: Now, that makes me think of what I remember when I was a kid, some of the… I was thinking about some of the crazy stuff that I was doing on my bike when I was like seven, eight, nine, like going up big dirt ramps and just flying. [chuckle] And if I think about doing that now, I wouldn’t do it. I would say, I could not do this. I would not know how to handle the slope, “What should I do?” I think that’s a perfect example of not using it and losing it.

Scott Grafton: Oh yeah. We’re constantly losing it. It’s subtle, the basic skills and the basic motor programs for the actions, they stick, but the elegance of the action is really vulnerable. If you stop doing it, you lose that grace very quickly.

Brett McKay: So another idea of physical intelligence is the idea of body schema, is that how you say it?

Scott Grafton: Yeah.

Brett McKay: Okay, body schema. What is body schema?

Scott Grafton: It’s really your map of where you are right now. If you were to draw a picture of your posture right now, what’s that posture? To do anything you gotta know… To do anything physically, you have to know your posture, so you need a way of tracking that. And it’s a hard problem because you’re this mushy three-dimensional object that’s constantly changing its posture and it’s… The sensors for tracking this are very noisy, they’re easily fooled, so it’s a real hard problem for the brain to keep track of simply the posture and it’s another one of these things that you would think, “Well, that’s just kinda we have that, we map it, we’re pretty good at it. No big deal.” But it’s a little bit like affordance, if you think about great athletes or great, any kind of great physical performer, schema is a huge, huge piece of their skill set. Again, it’s not just muscles and movements, it’s this awareness of your posture and pose. Just think of, just watch some Fred Astaire of him dancing, if you wanna see someone with absolute perfect control over their body position at any point in a dance, platform divers, anybody doing anything involving gymnastics, they all have an exquisite ability to track body pose. And it’s learned. It takes practice and experience to understand what those, where you are in space at any given moment in time.

Brett McKay: And that’s why it’s hard to teach kids like sports movements. I know I’ve had that trouble of trying to explain to my kids how to throw a ball, it’s like, “Well,” you try to tell it to them and you can tell they have no idea how their body is moving at all or they’re having a hard time.

Scott Grafton: Right. It’s absolutely true, yet when we talk about why is physical intelligence hard to get at, this is one of the places that’s probably the most difficult to get to, which is connecting your conscious verbal mind with your own posture. If you can look at it, but that’s kind of cheating, if you’re to close your eyes and just say, “Where am I in space?” They’re really disconnected, and so you really just have to do it experientially. Now, there’s exceptions to that, like there are elite athletes, really, really trained athletes who really can now consciously access specific attributes about their posture. Tiger Woods is a good example. At the height of his back swing, he can just stop in mid-swing and just say, “Oh, I need to just turn my wrist… Or I need to raise my elbows… ” He knows exactly kind of where he is in the super dynamic fast golf swing, but that’s the exception, not the rule.

Brett McKay: So it sounds like, okay, if someone thinks they’re clumsy, and they don’t… They’re awkward, they feel awkward and they move, it’s not like they’re inherently like that, it’s like they just need to practice more, this sounds like it’s a skill, if you wanna call it that, that can be developed?

Scott Grafton: Absolutely, this is pure skill. And in the book, I talk about some examples of how people do this, varied practice really helps. So not just doing your one sport, but shaking it up with a couple of different activities helps sort of a… You learn body schema more globally and that gives you some advantage. I have an example of Branko bull riders who do yoga. [chuckle] And it makes sense. Riding a bull has gotta be one of the most dynamic, complicated activities we’ve thought up, ’cause it’s super unpredictable, but they have to know exactly their posture and center of gravity to stay on this bull. And so, body-awareness is a big piece of that skill. And so just doing other activities where you enhance that, like yoga helps them.

Brett McKay: So yeah, mix it up, do diverse things.

Scott Grafton: Mix it up, yeah.

Brett McKay: So one of my favorite chapters was the chapters on problem solving and bears. Because we often think of problem solving as a… It’s like a human thing and humans, you just sit down and you think about the thing and you abstract and which we do, but you also made the case that problem solving can also be a very physical activity and bears show us that that’s the case.

Scott Grafton: Yes. You hit it absolutely right. If you say, “Okay, solve a problem,” you could sort of think of this like a computer program, “Okay, I’m gonna do some kind of hierarchical, logical, dynamic programming to look for all the possible solutions and we’ll work backwards and find out the optimal thing to do.” And sort of our war with bears over how we store food in the national parks shows that a lot of problem solving can be done without ever having to do that fancy kind of logical reasoning, that inside us and inside bears, there are these sort of learning engines that through trial and error figure out how to take care of a lot of problems. And so, that chapter explore sort of the arms race with the bears and how each time we think we’ve outsmarted them, they’ve kinda solved the problem, like you would think, “Well, they don’t have paw dexterity. So we’re gonna make bear boxes with funny handles.” Well, through trial and error, they just figure out how to use their hands in a new way, so they’ve got a learning engine for learning dexterity with their paw that we didn’t recognize existed.

And we have that same kind of learning engine so we can learn to do things with our hands as well, or we think, “We’ll put the food in this jar, this plastic jar and they are not gonna have the fortitude and endurance and willingness to work at the problem long enough to get through it.” Well, yeah, some bears will just chew through these plastic containers or, “Oh this has a tiny little tab on it and it requires a sequential movement. It has to do… First, it has to push this tab and then it has to turn the top of the jar, to get this thing open.” Well, sure they can learn to do a simple two-step action like that. [chuckle] Each solution we’ve come up with, through trial and error they’ve figured it out and that’s a really powerful learning engine that’s available to them.

And so, the chapter kinda ends with asking, well, there’s a point at which bears will get stuck, eventually there is something special about humans that bears and actually all the primates don’t have and kind of explore that. Some people thought that the chimps were really special in sort of abstraction that they could… They had sort of a basic form of reasoning that allowed them to go past kinda all the other species. The classic example is William Coller had this chimp and he hung a banana in a backyard environment, and there were some boxes sitting around and Coller watched as the chimp stacked all the boxes so he could get up high enough to get the banana. And he said, “Oh, this is the fundamental kind of reasoning in primates, it simply doesn’t exist in bears.” But I saw a bear do this same thing in the wild, in Yosemite it stacked logs, so it could get higher to reach for my food. [chuckle]

So other primates, and bears are very, very similar in what they can do in terms of problem-solving, what none of them can do is complicated sequential reasoning. So if I’ve gotta look at a problem and let’s say there’s three steps: Step one, step two, step three, and the only way I can solve it is to first figure out what the final action should be, and then work backwards to the first step. They can’t do that, they can figure out the first thing to do, then the second thing to do, then the third thing to do through trial and error, but they can’t do the reverse, what we would call dynamic programming. They can’t, “Oh yeah, I gotta set things up at the end and then work at the beginning.”

Brett McKay: Well just because we can do that, we also problem-solve like bears sometimes, we just keep doing different things until we figure out how to do it and find the thing that works.

Scott Grafton: Yeah, well in fact most of what we do is that. [chuckle] We really hate actually thinking very hard about a problem most of the time. Good example would be, we’re gonna have a breakfast for four, and I wanna have the food, the coffee all out on the table at the same time. I wanna have the table set. I have to organize cooking the eggs and timing that with cooking the toast and setting the table. I’ve got all these contingencies I’ve gotta sort out in time just right, so that when the guests arrive, everything is ready. And most people don’t think through, “Well, this is how long the eggs take, this is how long the toast takes.” They just kinda go for it. [chuckle] And they start scrambling. And through lots of experience and trial and error and many breakfasts they kinda learn unconsciously what the right timing relationships are so that the meal comes out at the same time.

Brett McKay: And it seems like that’s how we learn skills. I think you can watch instructional videos in step by step by step, but often, you just have to do something over and over until you find that groove, and you find what works.

Scott Grafton: That’s right, all this works great until the dimensionality gets too big. If you think about doing a task that has six steps, there’s 720 possible orderings of those six steps. And so, now who is gonna trial 720 steps, right? So there’s somethings where, eventually, you just have to think about it a little bit and try to get at least some of it organized in advance and that’s kinda what the literature is showing now, we don’t think through… If it’s a big problem, that has a lot of steps, we don’t necessarily plan all of them, but we chunk them into little groupings and then we try to just through trial and error, learn within each of those little groupings.

Brett McKay: So the final thing you talked about is fatigue. And this has been an ongoing debate in medicine and science. What causes fatigue? Because you talked about this one guy who looked at a bird like birds could fly thousands of miles and they’re just flapping their wings and they never get tired but a human walks a mile and they’re like, “Man, I’m feeling chafed here.” So what’s going on with our body and mind? Is the body get fatigued, does the mind get fatigued, is it both? What’s happened in there?

Scott Grafton: It’s both. I think what’s evolved in the last decade has been recognizing that it is both for a long time, in the ’70s, all the way going back to the 1920s I would say. We really focused on lactic acid and oxygen, the idea that you run around the track, as fast as you can. Your muscles make a lot of lactic acid, you don’t get enough oxygen on board and essentially, you have these toxins circulating that your brain senses and goes, “Wow, I’m really overdoing it with my muscles, I need to slow it down and take a break.” And so you generate a sense of fatigue based on sort of the pain that comes from that kind of intense exertion and that’s true. That’s all true. You go out to the track and you go sprint as hard as you can, you will feel pain and you will feel fatigued, there’s no doubt about it and you will have those biochemical changes in your blood stream. So, we’re not saying that doesn’t exist, but that doesn’t explain most of the fatigue that people day-to-day will describe which is, “I just walked five miles through a shopping mall. I’m tired of walking.” What’s that fatigue? So it’s definitely not, it’s not, I don’t have a ton of lactic acid built up in my blood stream, I haven’t been sprinting through the mall, I’ve just been strolling. So what’s going on there? And this goes back to, all the way back to Mosso, that’s the guy I was… You mentioned with the birds.

He’s really the first sort of neuro-physiologists that ever existed. He was really struggling in the 1870s with what is fatigue, what could this be? And he thought about it in lots of different ways, not just the chemical way. He did think about the chemical idea, so he did things like, he made frogs really tired by making them jump a lot and then he sacrificed the frogs, ground them up and injected them in dogs and then he claimed that the dogs got tired. Well, that’s kind of a weird experiment, but it shows you how primitive things were, but he’s searching for the chemicals that could do it, but then, ultimately, he realized that a lot of fatigue is not that, it’s essentially an emotion that the brain generates, independent of whatever the muscles are doing. And his idea was when you generate this emotion to hedge your bets. It’s like a governor on an engine that keeps it from spinning too fast. And from an evolutionary standpoint, it makes a lot of sense. The idea would be, okay, you’re a hunter gatherer, you’ve just walked half the day and you’re not really sure how much more you’re gonna have to walk that day.

It could be a little bit, it could be a lot, but you’re gonna set your defaults to assume that it’s gonna be a lot and so you always kinda keep a lot in reserve, you don’t wanna blow out all your gaskets and exert yourself to the point of true exhaustion. You always wanna keep a lot in reserve ’cause you don’t know what’s gonna happen in the wild and so your brain creates a sense of fatigue, an emotion that regulates how hard you’re gonna go and that assures that you’re gonna keep some energy in reserve just in case. And so we see this now, coaches have figured this out, and so if you look now at sports that do require long-distance exertion, particularly like, Nordic racing, long-distance rowing, those athletes train themselves right up to their lactic acid threshold and then they push themselves over long time periods, past the point, far, far past the point where they sense fatigue, they feel the fatigue, but they just learn to suppress it, the emotional fatigue, they just suppress that. And the funny thing is, you’ll see this all the time now in races, people get to the finish line and they collapse on the ground.

And it’s as if they’re trying to suppress this emotional sense all the way upto the finish line, they get to the finish line, they don’t need to suppress it anymore and so like this emotion just now, just wins and it just throws them to ground, but they’re back… It’s not like they’re actually truly exhausted because within a minute, they’re up on their feet and running around and waving to everybody if they won the race. So it really is a battle of multiple minds we have, one of which is persevering and pushing us as hard as we can and another one is creating this emotional sense and saying, “No, no, no, you don’t wanna go this fast, you’re gonna hold some… You wanna hold some in reserve, ’cause we don’t know if that really is the end of the race. Maybe you’re being tricked and the race is another hour, you’ve got another hour to go.” So your mind’s playing these games with you all the time when you’re out doing physical activities.

Brett McKay: That’d be a good race, you trick people about the finish line and then say, “No, actually, it’s the end… ” What do you hope readers walk away with after reading your book?

Scott Grafton: Well, I gotta go back once…

Brett McKay: Oh sure.

Scott Grafton: Before we get to that. I wanna mention the Barkley marathon.

Brett McKay: Okay, yeah.

Scott Grafton: Which kind of, the Barkley marathon is one of the most ingenious races because it’s an ultra-run in extreme wild Appalachian Wilderness and the athletes don’t know the route until one hour before the race and they don’t know when the race is even gonna begin for the day prior to when they all show up. So it really plays on this idea of fatigue as an emotion. Now, we’re really gonna mess them up by not letting them know where they’re gonna go, how far they’re gonna go for and what they need to do to plan their route until the very last second, so there’s, they’ve got no ability to mentally prepare or how to set their expected level of what a reasonable amount of fatigue is gonna be. It’s really ingenious.

Brett McKay: Yeah, I wonder who the kind of people would sign up for that?

Scott Grafton: Oh, they’re nuts. [chuckle] In the best possible way and that…

Brett McKay: Yeah, it’s possible.

Scott Grafton: They’re really testing themselves in a profound way.

Brett McKay: And so after talking about physical intelligence and writing about it, what do you hope readers walk away with after reading your book?

Scott Grafton: Well, I hope they go away with it, realizing that it’s not just use it or lose it, it’s use it in interesting ways, that physical intelligence is not the same as simple exercise, it’s really projecting yourself into really novel and interesting and challenging situations. It’s the difference between getting your exercise on a treadmill and getting your exercise on a trail in a park near your house. There’s just no comparison, right? There’s so much more that comes from real physical, complex and varied environments compared to simple exercise. I’m not saying we shouldn’t exercise, I’m saying we should double down and make that exercise even more interesting, even more physically interesting and demanding, and I think a person gets far more well-being from doing that, they age more gracefully and they experience much more of the world in a better way.

Brett McKay: And it also sounds like, even as an adult, try new stuff, take up dancing, join a softball team, learn a new sport, don’t be afraid of that.

Scott Grafton: Absolutely, yeah. Yeah, whatever your body will allow you to do, push it a little bit.

Brett McKay: Right. Well, Scott, this has been a great conversation, where can people go to learn more about the book and your work?

Scott Grafton: Well, the book’s on Amazon, it’s easy to find. I don’t have a big social media presence. [chuckle]

Brett McKay: That’s fine, that’s great. It’s always refreshing to find people like that.

Scott Grafton: You can come to my house and talk to me or [chuckle] email me. Anyway, yeah, the book’s on Amazon, and I’ve got a website for my lab and anybody can email me with questions.

Brett McKay: Well, fantastic. Well, Scott Grafton, thanks so much for your time, it’s been a pleasure.

Scott Grafton: Oh, you’re welcome, this is great.

Brett McKay: My guest today was Scott Grafton, he’s the author of the book, Physical Intelligence, it’s available on and in book stores everywhere. You can also check it in our show notes at where you can find links to resources where you can delve deeper into this topic.

Well, that wraps up another edition to the AoM podcast. Check it at our website at where you can find our podcast archives as well as thousands of articles that we’ve written over the years about pretty much anything you can think of, and if you haven’t done so already, I’d appreciate if you take one minute to give us a review on Apple Podcast or Stitcher, it helps out a lot. And if you’ve done that already, thank you. Please consider sharing the show with a friend or family member who you think would get something out of it, and if you’d like to enjoy ad-free episodes of the AoM podcast, you can do so on Stitcher Premium. Head over to, sign up, use code MANLINESS at check out to get a free month trial, and you’re signed up, you can download the Stitcher app on Android or iOS and start enjoying ad-free episodes of the AoM podcast. As always, thank you for the continued support. Until next time, this Brett McKay, reminding you not only listen to the AoM podcast, but put what you’ve heard into action.



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