How Nature & Other Physical Environments Impact Your Focus, Cognition & Health | Dr. Marc Berman

Andrew Huberman: Welcome to the Huberman Lab Podcast, where we discuss science and science-based tools for everyday life. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. My guest today is Dr. Marc Berman. Dr. Marc Berman is a professor of psychology at the University of Chicago, where he directs the Environmental Neuroscience Laboratory. His research focuses on how our physical environments, particularly natural environments, impact our brain function, mental health, and cognitive performance.

During today's episode, we discussed the fascinating and actionable science of how your physical surroundings indoors, and in particular, your relationship and interactions with nature, can shape your biology and your cognitive abilities. Dr. Berman explains how exposure to very common features in nature, such as fractal patterns, increase your ability to focus, reduce your stress, and improve your mental and physical health metrics, and not just while you're in nature, but after you return indoors for many hours and even days afterwards.

During today's episode, you'll learn about something called attention restoration theory, which turns out to be very important for understanding how different types of indoor and outdoor environments either deplete or restore your cognitive resources. We also discuss practical science-based strategies that anyone can implement, regardless of where you live. So if you're in an apartment or a house, if you have ready access to nature or if you don't, today's episode explains how to design your indoor space, the optimal duration and timing of nature exposure, and the specific visual and auditory elements that will provide you with the greatest cognitive and health benefits.

So whether you're a student or a professional looking to enhance your learning capacity, focus, and reduce your burnout, or you're simply interested in optimizing your mental and physical health through exposure to different elements of nature, today's episode provides clear, actionable protocols based on rigorous scientific research. By the end of today's episode, you'll have a toolkit of evidence-based strategies that will transform your relationship with your indoor environment and outdoor environments, and you'll learn to harness those to improve your brain and body.

Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is, however, part of my desire and effort to bring zero cost to consumer information about science and science-related tools to the general public. In keeping with that theme, today's episode does include sponsors.

And now for my discussion with Dr. Marc Berman.

Andrew Huberman: Dr. Marc Berman, welcome.

Marc Berman: Great to be here, Andrew.

Andrew Huberman: I love being out in nature, so I'm excited about today's conversation, which is taking place indoors, but we're going to talk about the relationship between the mind, the brain, nature, stress, rumination, and this incredible power that interactions with the natural world can have on our brain. As we wade into this, I'd like to start with this issue of recapturing our attentional abilities, because I think nowadays everybody, whether they're clinically diagnosed with ADHD or they are just a human being on the planet, feels as if their attention is being pulled in different directions, sometimes without our awareness, sometimes with our awareness. What is this notion of recapturing attention?

Marc Berman: Yeah, I think it's a really fundamental concept. On the surface of it, people just think about it as kids trying to pay attention to school or trying to pay attention at work. But it's actually deeper than that. We think that elements of attention are sort of involved in controlling all of our behaviors. When our attention is depleted, we don't have as much impulse control. We might behave more aggressively. We may not be able to achieve our goals. With a lot of things in the modern world, our attention is just being fatigued and we're depleted. It's really hard to recharge the battery or know what to do to recharge the battery. I think that's the entry point for why I got interested in this.

One of my mentors, Steve Kaplan, would talk about this directed attention fatigue problem that a lot of us are facing. Our ancestors, thousands and thousands of years ago, were not bombarded with so much information like we are now. The modern human has to pick and choose what to pay attention to, and it's kind of overwhelming. Steve Kaplan had this idea that humans have two different kinds of attention. One kind is called directed attention, and that's the kind of attention where you as an individual are deciding what to pay attention to. Presumably, Andrew, you're deciding to pay attention to what I'm saying, even though there are many other things you could find that might be more inherently interesting. This is a unique human capability. There may be other species that can decide what to pay attention to, but we're really good at it. Humans are really good at being able to focus on this lecture, reading this paper, or trying to finish this math problem, but we can't do it forever.

Everybody has had that sensation where at the end of a long workday, maybe three or four o'clock, you might be staring at the computer screen and you can't focus anymore. We call that a directed attention fatigue state, where you can't really control your attentional focus anymore. I see this all the time when I'm lecturing at the University of Chicago. I think I'm a decent lecturer. First five minutes of class, all the students' eyes are on me. They're engaged. They're nodding along with me. Forty-five minutes into my lecture, I see people nodding back like this [mimics nodding off]. They're getting tired. It's just hard for people to direct their attention for long periods of time.

We think there's this other kind of attention that we call involuntary attention, and that's the kind of attention that's automatically captured by interesting stimulation in the environment. Bright lights, loud noises—those things automatically capture our attention, and we don't really have much control over it. We think that kind of attention is less susceptible to fatigue or depletion. You don't often hear people say, "Oh, I can't look at that beautiful waterfall anymore. It's just too interesting. I've got to step away." Or, "I have to stop watching this movie. It's just too interesting. I'm too tired out." So that's a different kind of attention. We think what's happening in modern times is that our directed attention is being fatigued, but maybe we can restore directed attention by going into environments that can softly capture our involuntary attention.

Andrew Huberman: Do we know the basis of attentional fatigue? I could imagine it's something in the noradrenergic dopamine, catecholamine world. Listeners of this podcast will recognize those terms, at least crudely. I could also imagine that it's literally a fatigue of the visual system or the auditory system. It's hard to maintain fixation, as we say as visual neuroscientists, to focus on a target. It's challenging. If we allow our eyes to rest, it actually gets easier to look back at it and fixate on a target. So what is the basis of the attentional fatigue for this focused attention or what you call directed attention?

Marc Berman: It's a really great question. I'm not sure I have a great answer yet. Maybe you'd have some ideas, Andrew. One thing that puzzles me a little bit about the brain is that brain metabolism is about 20% of overall metabolism, no matter what people are doing, except for really extreme exercise where brain metabolism goes down a little bit. If you're asleep or if you're doing a hard calculus problem, the brain is still using 20% of metabolism. So it's sort of a puzzle. Why do we get this mental fatigue state? It's got to have some kind of neurological component. At this point, I can't point to it, so I'll talk about it more at this psychological level. It's a sensation that we have that we can't focus anymore.

If I was to talk about brain areas, I would say this ability to direct attention is most likely in frontal cortex, whereas this involuntary attention, sometimes we call it more bottom-up attention or exogenous attention, where it's activated by external stimulation, is probably more activated by things in the parietal cortex or even occipital cortex or auditory cortex, depending on what that external stimulation is.

Andrew Huberman: I'm not going to lean everything on the visual system, but I've been listening to this book that unfortunately is only available as an audio book called *Daily Rituals*. It's got two-minute chapters and describes the daily rituals of writers, artists, and creatives. It's very interesting that across many of those chapters, you find the same thing: almost all of these people had a ritual of taking some stimulant, typically caffeine, sometimes more aggressive stimulants, but caffeine, and then something to restrict their visual world, make it more tunnel vision. There are certain painters who literally built cardboard blinders onto his glasses when things weren't going so well.

The reason I bring this up is not as a suggestion, although I suppose it could be. I used to read papers—maybe I need to go back to this—I'd put a baseball cap on, put a hoodie on, and restrict your visual world. It makes perfect sense if, in fact, involuntary attention, which presumably comes from the periphery, is inexhaustible. What's interesting about the digital interface that we exist in now is that the whole world is brought right in front of us. We evolved to move through space and direct our attention to particular locations and let the rest of the world fall away. Involuntary attention could grab us to alert us to people showing up or danger or the smell of something wafting by, calling us for dinner. But now it's all placed right in our central visual field. It makes sense that we would all be very challenged with maintaining directed attention within that small tunnel vision.

Marc Berman: Yes. I would say something else too. If you felt like you had to create an isolation chamber to focus your directed attention, that's where we would say it's probably time to take a break. That's when we might recommend that you go for a walk in nature to recharge this precious directed attention resource. That might be a signal. If you're just having a really hard time focusing, you can try to power through, but I think that might not be the most productive. That might be a signal to you to say, "Hey, maybe I've got to go take a break." And the break better not be scrolling on social media. A really good break is actually a walk in nature or some kind of interaction with nature.

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Andrew Huberman: I want to talk about interaction with nature. This isn't a pushback on what you just said, but maybe just a probe a little deeper. I think a lot of people struggle with getting into a focused state at the outset.

Marc Berman: Yeah.

Andrew Huberman: I myself am familiar with sitting down to do some work and it taking some time to warm up. There's that agitation—I always think about it as literally climbing over or through barbed wire. Sometimes it actually feels like that. On either side of the barbed wire is a steep slope. On one side is distraction that can come from surfing the web or social media. On the other side is any sort of drama. Then our mind starts creating all these things that we think we need to do. The idea is to get through the barbed wire, and on the other side of it is that focused state. For most people, what I described is not terribly different from that. I'm making a lot of assumptions here, but I don't know many people that can just sit down to work and drop in like a trench.

Marc Berman: That's right.

Andrew Huberman: Can you do that?

Marc Berman: No, but I can do it better after a walk in nature. I think the walk in nature is sort of like a preparatory process. Think about lifting weights. You wouldn't start off a workout and say, "Let's put 250 on the bench and start going." You warm up. You have to wake up your nervous system a little bit. I think that's what interacting with nature is doing. It's not a passive process. We're not saying go and sit in a dark room for 30 minutes and then start to go to work. We're saying we want you to be interacting with nature. We want you to notice nature. We want your involuntary attention to be automatically captured by the stimulation of nature. After you've been sufficiently recharged, then we think you're going to be able to go back to your desk, direct attention, and be able to focus.

Andrew Huberman: Let's talk about some of the data around what walks in nature and interactions with other components of nature can do for our cognition and our level of focus. Intuitively, people will appreciate that a nice walk in nature, not looking at one's phone, is very pleasant and relaxing, and then you get back to your desk and you can really focus. What about the laboratory data that support this or out-of-laboratory data that support this? Maybe you could describe a few of the incredible studies that you've done because they are really incredible and very pioneering in the way that you've brought real laboratory technology into nature as well. Pick your favorite study about this, and then I'll ask you about a few others.

Marc Berman: Sure, thanks. I think the seminal experiment that we did was back in 2008. At that time, when people did these nature walk studies, they would ask people, "How do you feel after the walk?" It was very subjective. I'm not against subjective accounts. People reported, "Yeah, I feel much more refreshed after the walk in nature." But I always felt a little bit dissatisfied by that. I wanted to see if objective performance changes. We would probably be dissatisfied if I gave you a pill and said, "This pill is going to get you stronger. You're going to be able to lift more weight." If we just had people say, "Yeah, I feel like I can lift more weight," I don't think that'd be satisfying. We'd actually want to see if people can actually lift more weight.

What we did is we designed a study that was experimentally controlled with objective measures: how did people perform cognitively before and after going on a walk in nature? We brought people into the laboratory and gave them some challenging working memory and attention tasks. One of the tasks was called the backwards digit span task, where you would hear digits out loud at a pace of about one digit per second, and then the participant would need to repeat them back in backwards order. If I said 5, 6, 7, the participant would have to repeat back 7, 6, 5. Pretty easy task at three digits, but we keep increasing the number of digits all the way to about nine digits. At about five digits, you're ready to pull your hair out—it's a challenging task.

We gave participants this backwards digit span task. Then we gave them a map of a walk. In the first studies, it could be through the Ann Arbor Arboretum, which was a nature walk by the psychology building at the University of Michigan. Or participants went for a walk on busy Washtenaw Street in downtown Ann Arbor. The walks were both about 2.6 miles, so it took people about 50 minutes to do the walk. We also took participants' cell phones because we didn't want them texting or chit-chatting on the walk. We wanted their attention to be fully focused on the environment. We also did one other thing: we gave them a GPS watch. We did it for two reasons. One, we wanted to make sure they went on the walk and didn't just go to Starbucks. Two, we wanted to see if people got lost, because if people got lost on the walk, maybe that wouldn't be restorative.

So people do the backwards digit span task. We send them on a walk in nature or we send them on a walk through an urban environment. They go on this 50-minute walk. They come back to the lab. We give them that same backwards digit span task again to see if there is any performance change. Then we have people repeat the whole procedure again a week later. So if they walked in nature the first week, they walked in the urban environment the second week, or vice versa. It's all within subject, very tight experimental control.

What we found was pretty incredible: people's working memory capacity and their ability to direct attention improved by about 20% after the walk in nature versus the walk in the urban environment. People might think, "Well, maybe it's just because the nature walk was more pleasant. They just liked the nature walk more." People did tend to like the nature walk more, and we did measure improvements in mood. But we didn't find a very strong correlation between improvements in mood and improvements in the working memory and directed attention performance, suggesting that people weren't just getting better because they were getting into good moods.

The even stronger demonstration that this wasn't mood driven is that we had people walk at different times of the year. Some of our participants walked in June when it was 80 degrees Fahrenheit. People said, "Mark, I can't believe you're paying me to go for a walk in nature." Really healthy mood benefits, really healthy working memory and attention benefits. We also had participants walk in January, 25 degrees Fahrenheit. People said, "Mark, I was freezing my butt off out there. I did not enjoy that walk." But incredibly, the people that walked in January when it was freezing cold and they didn't enjoy the walk obtained the same working memory and attention benefits as the people that walked in June. You didn't even have to like the nature interaction to get this directed attention benefit. I thought that was pretty interesting and counterintuitive, that this isn't just about liking or pleasantness. There's something deep about processing auditory, visual, and maybe even tactile stimulation of nature that is good for our brains and restores our ability to direct attention.

Andrew Huberman: Super interesting findings. It leads me back to this finite resource of directed attention, whatever the underlying networks and chemicals happen to be. Could we speculate what might be occurring in the nature walks that is enhancing or allowing restoration of directed attention? The neurobiologist in me wants to say, "Okay, I'm walking in nature. That probably means some greenery, some dirt, maybe some water." I could imagine one hypothesis is the kind of irregularity of nature environments. Trees might be spaced out in perfect spacing like on Palm Drive at Stanford—it looks like it speaks to the engineering department that they're set at such even intervals. But typically when you're in the forest or nature, there are things to break up that regularity. Indoor environments and city environments tend to have a lot of right angles. Buildings can be different sizes, but city blocks are pretty fixed for a given neighborhood in terms of their size. That's just one hypothesis I'm coming up with off the top of my head.

Do we have any data or do you have any preferential speculation as to what it is about nature in terms of its physical structure? As a corollary to that, is it that nature is relaxing people and therefore they're not having to use their directed attention, and therefore directed attention capability comes back or is set at a higher level? I realize this is two questions braided together, but that's what I'm curious about.

Marc Berman: Yeah, I think both elements are in play. Let me start with the resting directed attention element. Let's pretend we're on these walks in nature or the walk in the urban environment. The walk in the urban environment required people to cross a lot of streets, so you had to be vigilant. You still had to use directed attention. There was a lot of car traffic, so you're hearing the noise of cars whizzing by at probably 40 or 45 miles per hour. There's also advertising. You're going by shops and billboards. That requires some directed attention. You can't really just mind wander and let your mind go in those environments. You still have to be vigilant. You still have to use directed attention.

The walk through the Ann Arbor Arboretum—you didn't have a lot of those distractions. You only had to cross one or two streets, and then you're getting towards the arboretum. You don't have to cross any more streets. There's no advertising there. Then there's this idea of soft fascination. There are all the colors, fractalness, curved edges of nature that we think capture our involuntary attention in what we say is softly fascinating ways. We think that, in combination with not placing a lot of demand on directed attention, is why nature is able to restore directed attention.

What do I mean by softly fascinating stimulation? Let's pretend we're looking at a waterfall. The waterfall is really beautiful. You can hear the rush of the water going down. You can see the bubbles and maybe some of the froth of the water going down. It captures our attention, but we can still mind wander and think about other things at the same time. It doesn't harshly capture all of our attentional resources. If we're in Times Square, also super interesting, lots of interesting stimulation to look at, but it captures all of our attentional resources in an all-consuming way that doesn't allow for any reflection or mind wandering. While Times Square does capture our involuntary attention, we say it does so in a very harshly fascinating way, whereas the waterfall captures our involuntary attention in a softly fascinating way. We think that's the way that's going to be restful of directed attention.

So we think two elements created why the nature walk was restorative. One, it didn't place as many demands on directed attention. Two, it had this softly fascinating stimulation that activated this involuntary attention, but not in an all-consuming way. We think those two things are critical.

The other point you bring up is what causes soft fascination to be captured, or why does something capture involuntary attention in a softly fascinating way? That gets really interesting. We think it could be elements of the structure of nature. It's interesting, Andrew, that we can get these effects of nature improving cognitive performance from people just looking at pictures of nature versus looking at pictures of urban scenes, listening to nature sounds versus listening to urban sounds, watching nature videos versus watching urban videos. There you don't have to worry about getting hit by a car. There's something about the visual aesthetic of nature that we think is producing some of those benefits. Our brain maybe processes that fractal stimulation in more efficient or easier ways than the 90-degree angled built environment that we've constructed.

Andrew Huberman: I have to ask: if you are exposing people to nature images versus urban environment images in the laboratory and seeing some of these same effects, are you presenting that on a typical small screen right in front of somebody, or is it in panorama? I'm headed in a particular direction with this question because I have a pet hypothesis as to what nature could be doing to not deplete directed attention. But before I ask you about that, I'm curious what the experimental setup is. I'm also asking because I'm a little concerned that people are going to hear, "Great, I can just look at a picture of a forest. I don't have to get outside." As you mentioned, there are so many things in an actual nature environment that provide a rich experience of soundscape, et cetera. But what's the format?

Marc Berman: It's basically the same format as the walking study that I described. People come into the lab, we give them the backwards digit span task, but then we take them into a room in the lab where they just have a computer screen that's flipping through nature scenes or urban scenes. They look at the scene for a couple seconds. We also have them rate the scene on a scale of one to three for how much they like it, just to make sure that they're awake and engaged with the environment. That whole procedure takes about 10 minutes. They come out of the laboratory room that had the pictures, and then they take the backwards digit span task again to see if there are changes in performance. Then we'd have them come back to the lab a week later and repeat the whole procedure. If they saw the nature pictures the first week, they see the urban pictures the second week or vice versa. There, even just seeing the pictures of nature, we see improvements in working memory and directed attention. However, I would caution that the effects are not as large as they are for the actual walk. The intervention is not as strong as actually walking in nature.

Marc Berman: Just seeing 10 minutes of nature pictures, it's incredible that it works. You can get some of these benefits, but the benefits are not as strong as they are for the real thing. And the same procedure happens when we test sounds of nature versus urban sounds. We test people with the backwards digit span task. Then we put headphones on them, play a series of nature sounds or play a series of urban sounds. Then they do the backwards digit span task again. And we find that when people listen to nature sounds, they also show improvements on working memory performance and directed attention. We don't do anything special in terms of having it being a panoramic view. It's basically just looking at a slideshow of nature pictures or urban pictures on a computer screen.

Andrew Huberman: So I'm hearing this. I'm starting to wonder whether we have brain areas and or circuits that are devoted to nature, which first pass seems like kind of a crazy idea because visual perceptions and auditory perceptions are built up from their sort of elementary units, which is just nerd speak for, you know, your eye and low level visual system cares about circles and angles. And then your higher level cortex puts it into the recognition of a person or a building, et cetera, is literally built up from elementary units. In the sound domain, it's built up from different frequencies, et cetera. But there's something about this problem. Here's what's on my mind. If I walk through a neighborhood, an urban neighborhood, where it's a bunch of warehouses with some cyclone fence and some signs and it's a weekend, maybe it's a Sunday and they're all closed, there aren't trucks coming in and out and not a whole lot's happening. This reminds me of West Oakland near the shipyard on a Sunday. Not a place I recommend people go unless you really like kind of bland urban environments on a Sunday because not much is happening. It's a shipyard Sunday. It's closed. Versus a trail in Yosemite. I used to work up in Yosemite in the summers, but it's not one of the most magnificent trails. Meaning it's not Yosemite Falls, Half Dome, or Cloud's Rest, my favorite trail. It's a kind of barren environment, but there might be a meadow and there might be a mountain. You would never say, you know, this trail up in Tuolumne that I'm on right now is kind of boring. It's not as interesting as the peak of Cloud's Rest. And arguably it's not. I mean, when you get to the top of Cloud's Rest, it's like, whoa. I mean, it's a spiritual experience. But when we are in nature, we don't tend to think, oh, this is boring. There's nothing here. Even if it's fairly sparse visually. So as we dissect this, it can't just be density of visual stuff. There must be something additional. And we could say, well, maybe it's the greenery. But I was out in the Utah desert not that long ago, and it wasn't arches or the beautiful landscapes that definitely exist out there. It was just kind of like horizon sky, some sand, maybe a cactus or two, some rocks, but it's beautiful. And you would never say, oh, this is boring because it doesn't have arches. When you get to arches, you're like, it's that much better. You get the point here. So it can't be density of visual objects. And it's pretty quiet out there in the desert, except at night when it really is quite noisy in the desert actually with animals and stuff if you're lucky. So what's the deal?

Marc Berman: Part of it could be evolution to some extent. I mean our brains evolved in nature, right? So is it possible that our neural machinery is just more tuned to that kind of stimulation? I mean, there's no natural right angles in nature. We created right angles. That's pretty speculative, right? And I'd want to dig in a little more about that, but I can't ignore it. There's just something maybe fundamental with how our brains evolved. And we evolved in nature. There's just something about, we just maybe more fluently process natural stimulation and maybe we like that. But we started to have some ideas, soft fascination. I love it as a concept, but it still is a little bit squishy. I kind of wanted to get some kind of quantitative parameters around it. So one idea that we were thinking about was that maybe nature scenes are actually more compressible than urban scenes. Now, what do I mean by that? What I mean is that maybe because there's repeated patterns in nature, I don't need to store all of the information. I can kind of smush it down into fewer bits. And that might be easier for my brain to process. Whereas in a lot of urban scenes, it's not very fractal. And maybe I have to store all of that information. So we actually, this is one of my students, Nakwan. We actually ran a JPEG compression algorithm on thousands of nature and urban scenes. And it turns out nature scenes get compressed down into fewer bits.

Andrew Huberman: So we should, no pun intended, unpack a little bit of what you just said. I think for people that are not familiar with thinking about neural processing and JPEGs versus TIFF files, if I may, I'm just going to give my crude rendition of this because I was very interested in this and did some work related to this years ago. But just to keep it brief, people are probably familiar with the idea that some electronic files are larger than others. So if you have a picture that you take on a camera or your phone and you want to email it to somebody nowadays, you would just text it, but you might want to email it to somebody. You can send them the TIFF version or the Photoshop version, and it's going to be a very big image or a big movie for that matter. There's another way to send it, which is at a lower file resolution, but therefore takes up less memory. It doesn't come through as this massive file that you need to go to a second party site to download or something. And that's a JPEG. The whole basis of JPEG is to take the average of pixels near one another and compress them. Kind of take a best guess as to what a black pixel is probably next to another black pixel or probably a gray pixel, but probably not a white pixel. It could, but what it does, it takes a local averaging and then it compresses it into a JPEG and then you send it to the other side. But on the other side, you can also unpack that image to its original high resolution value. The brain does a similar thing. And the best example that I have from the brain is the olfactory system. Where in the olfactory system, you're breathing in tons of volatile chemicals, meaning volatile makes it sound like they're about to throw a tantrum, but they're moving through the air, you inhale them, and they're activating millions probably of different odorant receptors. But your brain compresses those down into coffee. This is coffee. And then you unpack it as coffee. Now, if you're a coffee connoisseur, or in the case of wine or a food connoisseur, you can get into the subtle nuance and say, oh, you know, there's a little bit more of this and a little bit more of that. But you're not thinking about the individual chemical molecules. You'd say, oh, it's a little bit of a cherry flavor or this chocolate has a little bit of a citrus. So that's essentially what the brain does with visual images as well. So that's my very crude and certainly not complete description of how bits of information are compressed as they go into the brain and then unpacked into what you call a perception.

Marc Berman: That's right. Or an experience. And the same thing is true of a TIFF or Photoshop file compressed to a JPEG.

Andrew Huberman: Yes. And then you can literally uncompress that file if you have the sort of computational capability.

Marc Berman: So one thing I just want to add to it, the kind of compression that we were doing with the JPEG compression was lossy, meaning that the information was thrown away. You couldn't recover it, but that didn't really matter. So if you showed people the image at its high resolution versus the image at its compressed or lower resolution, the human eye can't really tell the difference. But for the urban images, you couldn't get away with that trick. You needed to keep all of the original pixel values. So that's kind of what computers and our iPhones are actually doing. And the reason why we think they can get away with that is because nature has a lot of this repeated structure like you were talking about before about predicting the pixel's value and you can capitalize on that. That means there's a lot of redundancy so you don't need all of that information. Natural images also tend to have, maybe this is going to get a little bit technical too, a lot of high frequency spatial content. It's a lot of little changes, little contrast changes that we don't really need. Whereas in the urban environment, there's more of these big contrast changes that we do need. So we think maybe the brain is, like you're saying, there's all this evidence that the brain is basically doing that. And in nature, because you can smush it, you're walking through the nature, you can kind of throw away a lot of the information. And so we think that actually might be why it's sort of more softly fascinating and easier to process versus the urban environment. There's another element here too, which we haven't got completely yet, but which I'm very interested in. So that's looking at sort of complexity of the images at the very, very low level. But you could also think about semantics, like the language that we use to describe a scene. And when I see a nature scene, I don't have a huge language repertoire. I can say lake, tree, river, shrub, sand, desert. But when I'm in the urban environment, I can say Volkswagen Beetle, BMW M3, gothic architecture. Like my vocabulary is so much more complex for an urban scene. So one thing that we're also thinking about is like maybe nature might also be more semantically simple, from a linguistic level that I can just label it really easily. And then it allows my brain to just not have to store as much information. Whereas in the urban environment, maybe I'm forced to sort of label all of these objects and it just takes up more room in our brain. So we also do these studies where we show people a bunch of nature scenes and urban scenes and then test their memory for the scenes. And it turns out that people's memory for the nature scenes is worse than the urban scenes. So people remember...

Andrew Huberman: Exactly. It fits. It fits.

Marc Berman: And you might think, oh, well, you want to remember stuff. But actually, in some sense, it's measuring how difficult it is to process. And if it's so easy to process nature, you're just not going to remember it. And that, in this case, is a good thing. So we think that's also part of it, that that's also saying to us that, yeah, it's just easier to process this natural stimulation versus this urban stimulation where you just have to attend to more stuff. It's more sticky.

Andrew Huberman: Do you have any data as to whether or not people track time better or worse when they are in natural versus urban environments?

Marc Berman: So I don't have direct evidence to this, but I have a few other little pieces of evidence that I think will kind of get us there. So we've done some studies where we send people. This one was actually sending people to a nature arboretum, an indoor nature arboretum, the Garfield Conservatory, a really beautiful conservatory in Chicago, versus the Chicago Water Tower Mall, a very fancy indoor mall in Chicago. And we actually gave participants cell phones that we had in the lab that would ping them and ask them questions while they were going on the walk in the conservatory, the walk in the mall. And we asked them, what are you thinking about? And it turns out when people are walking in nature, they actually think more about the past than walking in the mall. So that was kind of interesting. This is also kind of interesting: people also said that they felt more impulsive in the mall than in the conservatory, which makes sense, mall designers want people to be buying things. But this idea about thinking about the past to me suggested a little bit that time might be going a bit slower. Other people have found in cities that the larger the city is, people walk faster, like the pace of everything is a little bit faster. So my hunch is that based on those two findings, I think time does probably slow down in nature, but I don't have direct evidence for that. I think that's something that'd be really super interesting to study, but that would be my hypothesis: in nature, time does slow down a bit.

Andrew Huberman: If you had to wager a guess, would you assume that going into an art gallery is more similar to taking a walk in nature or an urban environment? I mean, it's so rich with information. You have options. You have to decline certain things, certain rooms, certain paintings, certain sculptures. It's a lot of decision-making. And yet most people find galleries, big galleries to be extremely calming. Maybe it's also because everyone's quite quiet in them.

Marc Berman: I would say the gallery would have a similar effect to nature, would be my guess. Because Kaplan's attention restoration theory really is not specific to nature. It basically just says you got to find an environment that doesn't place a lot of demands on directed attention while simultaneously having softly fascinating stimulation. And an art gallery might meet those two criteria. If you don't have to be tested on the artwork and you can just kind of go there and you don't have an agenda, I think there's going to be a lot of very softly fascinating stimulation in an art gallery. So my hunch would be that, yeah, walking through an art gallery might have a similar kind of effect. This is going to be a little bit of a jump. There are some studies that we did where we were looking at the relationship between park visits and crime and going to a museum versus crime. So there's been a lot of actually interesting studies suggesting that interacting with nature can make people less aggressive. And we think it has to do with attention. So we had this incredible data set, the cell phone trace data set, where from 100,000 people in Chicago, we knew where they lived. And we knew where they went for an entire month. So what we did is we quantified how many times did people leave their neighborhood and go and visit a park versus leaving their neighborhood and going to a museum or something like that. And we wanted to correlate that with crime. And sure enough, we found that neighborhoods where people leave their neighborhood and go and visit a park, that actually predicted less crime in those neighborhoods, but the museum visits didn't predict that. And this was controlled for socioeconomic background. I mean, more or less, again, it's a correlational study, so I can't claim causality, but we also controlled for age, education, income, all those demographics. So there, it seemed like there was something special about the park visit versus the museum visit on at least aggression. But I do believe that going through a museum might have a similar effect to nature. I'm not sure it'll be strong, but I think the museum maybe has a lot of the same elements that a nature walk might have.

Andrew Huberman: I think I'm just obsessively starting to drop into the trench of what sorts of things are attention depleting and what sorts of things are attentionally restorative. Because I personally believe that our ability to attend is like the hallmark of building a great life. I've so much so that on hikes and walks, I will listen to audio books and podcasts. But there are times when, for instance, I will exercise with silence. And then I'll use music as something to push me through some particularly hard moments in the exercise, but then I'll turn it off and bring it back. I don't just kind of head out the whole time blasting music. Sometimes I'll do that. But I'm starting to become kind of an experimentalist with this idea of attention as this resource that we deplete each day, sleep, it's restored mostly. Looming in the backdrop of this conversation is a conversation about social media. But before we go there, if you were at this point to give a kind of a best recommendation in terms of how to reset one's attentional abilities, what are the basic requirements?

Marc Berman: I think there's a lot there too. I think you have to be really mindful about directed attention fatigue. So if you're trying to study or you're at work and you're having a really hard time concentrating, I would recommend not just trying to power through. If you have the ability and the time to take a break, I recommend that you stop and you take a break. And what kind of break do I recommend you do? I recommend that you go and try to find some nature and walk in nature.

Andrew Huberman: What if you're having a hard time getting into a focused state at all? It's not that you fatigued it that day. So many people that I hear from who listen to the podcast and elsewhere will say, they get up. They did their best to get their sleep. They get their morning sunlight. They hydrate. They drink their caffeine. They sit down to their computer and they just can't focus. And then they start thinking like, do they have brain fog? Do they need a nootropic? All these questions start to arise. What are your thoughts?

Marc Berman: I think in some sense, even though you might be very well slept and very well fed, you could still be in a directed attention fatigue state. So I think, yeah, if you can't concentrate right in the beginning of the morning, then you should go for a walk. That should be the first thing you should do. Or if you don't have access to nature, maybe listen to some nature sounds or watch a nature video or something like that. We find that all those things can be beneficial. Even looking out the window to nature can be beneficial. Looking at a picture of nature can be beneficial. So I would say anytime you're having trouble concentrating, it doesn't matter if it's at the beginning of the day or the end of the day or the middle of the day, I would recommend that you take some kind of break with nature. And it could be simulated nature, like listening to nature sounds, watching a nature video, looking at nature pictures, or even better is if you can actually get out and interact with nature. Because Steve Kaplan used to also talk about these other elements that might be important for a restorative environment. One was that the environment had to have extent, meaning that it had to have enough interesting things to look at. Now, it doesn't mean that it has to be Yosemite Valley, which has incredible spatial extent. I mean, it's huge. It's enormous. But near my office at the University of Chicago, we have this Japanese garden, the Garden of the Phoenix. It might be only like 100 square meters. It's pretty small. But it's still got a lot of extent. It's got a walking path. It's got a little waterfall. You can see Lake Michigan. So that's one element. Another thing about nature is that you want it to be compatible with your goals. So what do I mean by that? If you've got a big exam and you haven't studied, I'm not sure going for the walk in nature is going to work. You better use that time to study. But if you can't concentrate, trying to power through, I don't think it's going to be compatible with your goals. I think going in for the nature walk is compatible with your goals. So that's another thing that's going to be really important. And the other concept that Steve used to talk about being important is that the environment needs to give you the sense of being away, that you're kind of removed from your current environment, almost like a change of mindset. And again, that doesn't mean you have to go really, really far away, but you might want to go to a location that's not at your desk. So maybe don't sit at your desk and look at the nature picture. Maybe you want to go somewhere else and look at the nature pictures. And this kind of distance, I think, could be helpful. I don't know if Cal Newport talks about this in his deep work, but I've heard people talking about in an office, you might want to have like a separate area of your office for deep work. And I think this kind of sense of being away is related to that. You kind of want to get out of your current state and go into this other environment that might be able to replenish those resources.

Andrew Huberman: So I'm hearing that there are two sides of the coin. One is to designate an area for work that's truly for deep work.

Marc Berman: Yes.

Andrew Huberman: I followed Cal's recommendation and now I have an area in my basement, believe it or not. And there has never been a phone in that basement. No phones allowed in that basement. That's not a rule. It's not a protocol. It's a policy. And I remember he talked about in his, he has this library office that he goes to and I very much agree with that. Now I do get internet access down there a little bit if I need to look for papers, but I've been turning off wifi on my computer when I go down there to work and I get more done in three hours down there than I would in three weeks above ground. I swear, it's a huge effect. The other side of the coin is this business of getting out into a different environment. And it sounds like these walks or these ventures into nature don't take terribly long. How long does one need to do this in order to get the enhancement and focus and working memory? Like, what do the data say?

Marc Berman: Yeah, I mean, when we did our walking study was 50 minutes, but I've seen other studies with as little as 20 minutes. You can get the effect.

Andrew Huberman: For cognitive enhancement.

Marc Berman: For cognitive enhancement. And there's actually been some interesting studies with kids with ADHD and they find attention benefits for these kids with ADHD after just a 20-minute walk in nature that actually was similar to a dose of Ritalin, so that was pretty incredible. So it doesn't have to be super long. And when we were doing the slideshow of nature pictures, that was only for about 10 minutes. So it doesn't have to be a really, really long immersion. There have been other studies that have suggested, like overall, you might want to get about two hours a week in nature.

[Break for sponsor acknowledgment]

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[Discussion resumes]

Andrew Huberman: You know, I've been long obsessed with this difference between what happens in our brain stem, the areas involved, as you know, with levels of arousal and stress versus calm, when we look at a fixation point versus a horizon or when we go into panoramic vision. And there are now ample data to support the idea that when we fixate on a small box like a phone or a computer or we're fixated on something, we're reading or paying attention to it, that our level of autonomic arousal creeps up. It doesn't creep up indefinitely, but this makes sense, right? Visual attention matches the cognitive attention. You need arousal, aka alertness to get cognitive attention. But that when we go into panoramic vision, which is for the aficionados, you can look up magnocellular vision. What you're essentially doing is you're taking bigger pixels of the visual environment.

Marc Berman: Yes.

Andrew Huberman: And when we look at a horizon, we naturally go into panoramic vision, unless we're looking at our phone and taking a picture of that horizon.

Marc Berman: Yes. So take note.

Andrew Huberman: It's interesting to me to think about visual environments such as nature that have us taking larger bins, pixels if we're talking about visual space, but that we're also perhaps – this is a question I'm obsessed with – perhaps taking larger time bins. What do you think about a kind of a general idea that what we need to do in order to be focused is to allow our mind to go into these kind of like time drift states?

Marc Berman: Yeah. And I kind of think, you're talking about it from a visual perspective, but I think it's also from a cognitive mental perspective. So I think also too, being in nature kind of widens your cognitive landscape. And that's why I think people sometimes, you hear all these anecdotes where people are struggling to solve a problem, they can't figure it out, they go for a walk in nature, and then boom, they solve the problem. Because the brain is still churning on that, right? But maybe being out in nature sort of inspires this widening of attentional space internally.

Andrew Huberman: We had a guest on this podcast, Michael Platt from the University of Pennsylvania. He's a neuroscientist, and he told us about this experiment. It's pretty wild. This still blows me away. You're probably familiar with it, but I wasn't, which is that if you have human subjects in a lab, do a connect the dots task where the dots are placed very close together versus a connect the dots task where the dots are placed much further apart, and then you give them a creativity task, the people who do the task, and it's well-controlled for folks, connecting dots that are further apart in physical space show significantly elevated levels of creative insight to solving problems. And so there's something about visual space and time and our ability to link things in cognitive space and time. This is why when you said earlier that when you're out in nature, there aren't as many words to describe things. What that means to me, if I think about the results that Platt was talking about, is that perhaps it isn't just that there's a dearth of language, but perhaps then your brain starts to drop into other modes of cognition. I don't want to sound too nerdy just to sound nerdy here, but there are all sorts of things in your brain that can't have words assigned to them. Like, for instance, your childhood, you could give the whole story, but it still wouldn't capture it, right?

Andrew Huberman: But there was your trauma, there was your wins, there was your falling in love. We have these words, but they don't capture the experience. They don't capture the visceral experience, the smells, the taste. And so I love the idea that in nature, things are sparse enough yet rich enough that maybe these networks get triggered.

Marc Berman: Right. And I think this is another area where we can get into the neuroscience a little bit. We have some of these ideas about what a brain looks like when it's kind of at rest. And when we talk about fractalness, most of us think about a spatial fractal. So if there's a snowflake, it's got a characteristic shape. If you put that snowflake under a microscope and zoom in, it still kind of has that same shape. If you zoom in some more, it's still got that same shape. So it doesn't matter what scale you look at the snowflake, it's got the same shape. That's called scale-free spatially, or another way to say it is that it's fractal. It's got this repeated patterning at these different spatial scales. And nature is filled with fractals.

Andrew Huberman: Could you tell us more about some of those? I recall hearing about fractals from Mandelbrot, who came up with fractals. But despite the fact that I remember Mandelbrot's name, all that tells you is that my brain is filled with meaningless information, because what I want to know is not who came up with it. This is the problem with the hippocampus, you can encode perfectly useless information, no discredit to Mandelbrot. But where in nature, aside from snowflakes, do fractals show up? Are they in tree bark?

Marc Berman: Everywhere. I mean, a tree is also quite fractal. You have the trunk of the tree, and then it breaks off into branches, which breaks off into smaller branches, which breaks off into leaves, and the leaves have the veins that also branch off. So it's very, very fractal. It's got the same branching structure at all these different scales.

Andrew Huberman: Really? So when I look at sand in the desert, you're telling me that this regularity exists at every scale?

Marc Berman: Yeah, pretty much. I think a desert would also be fractal in terms of how the wind shapes it, because the wind is also a kind of fractal process. So the sand will be somewhat fractal. A mountain scape will also be quite fractal. A coastline will be fractal.

Andrew Huberman: Well, tell me for a mountain. Where am I going to look at a smaller scale? I can imagine a mountain. Now, if you zoomed in on a different portion of the mountain, it would have some of the same structural properties as the zoomed out version?

Marc Berman: Really? Yeah.

Andrew Huberman: Wild. Yeah.

Marc Berman: So, to return back to compression, if you have this repeated patterning, that might be easier for our brain to process because you really only have to encode one structure, since that structure is repeated at all these different scales. Whereas human beings and advertisements and all that, there's this thing in science, as you know, people are either lumpers or splitters. Many a career has been made by splitting when lumping would have been sufficient. Human behavior, human advertising, music—I'm sure there's immense regularity—but when we're bombarded with that, now I'm making the segue to something like social media, where you're just bombarded with sensory information. One movement of my thumb takes me from one cognitive landscape to a completely different cognitive landscape.

Andrew Huberman: If it were my preference, my entire feed would be dogs. But I'm going from dogs to politics to fitness to stuff that the algorithm is testing on me. It's amazing that we can do this. And yet, the more we talk about nature and how restorative it is, or reading a book and following a common narrative, drilling down into that, or watching a movie which hopefully has some continuity to the plot, the more I realize that social media is, for lack of a better word, chaos. It's cognitive chaos. It's definitely not fractal.

Marc Berman: It's definitely not fractal. And if we return to fractalness, we talked about fractalness in terms of space, like a shape where you zoom in and see the same shape. You can also talk about fractalness in time. You can have a signal oscillating in time, fluctuating in time, and you can quantify how fractal that signal is in time. If you look at the signal at one millisecond, 10 milliseconds, 50 milliseconds, 10 seconds, 30 seconds, an hour, does that signal look the same or does it look different? If the signal looks the same at all those different temporal windows, we say the signal is fractal in time.

Andrew Huberman: Can you give me an example from a nature environment and one by comparison from an urban environment? I'm thinking a car alarm in an urban environment is the most alerting. It grabs our involuntary attention. And it's not fractal. It's periodic. It's just over and over again.

Marc Berman: A fractal signal will have low frequency stuff with a lot of power, but it also has all the different frequencies represented. How their amplitude is—this is going to get a little nerdy—is proportional to their frequency. So low frequency stuff will have higher amplitude or higher power, and high frequency stuff will have lower amplitude or lower power. A lot of natural sounds are also more fractal. But what's interesting is that you can also look at brain signals. I can put a person in an MRI machine and look at how the brain areas are fluctuating, or I can have an EEG cap on them and look at how their electrical activity is fluctuating. It turns out that when brains are more fractal in time, brains are exerting less effort, less cognitive effort. It's kind of depressing, but as we age, our brains get less fractal. If you're learning a new task for the first time when it's harder, the brain is less fractal than when you're well at the task. If you're doing an easy task, the brain is more fractal than when you're doing a harder task. So we think that maybe nature is pushing the brain into this higher fractal state that might be this sort of critical rested state that's going to allow you to have a lot of directed attention when you need it.

Andrew Huberman: When you need it. Versus the social media stuff is just pulling, grabbing. It's not letting you get into this fractal rested state. It's driving fractalness down.

Marc Berman: Right.

Andrew Huberman: Well, the social media platforms—not to paint them as evil because I teach on social media, learn on social media, enjoy social media—but it's a business. They're not doing it for free. They're not doing it out of the goodness of their hearts. I basically think of social media as the reality TV show that we've all either chosen to be a part of. We've cast ourselves in it. The idea here is that it is not designed to be relaxing.

Marc Berman: No. It's designed to capture your directed attention. That's right. If it just grabbed your involuntary attention, it wouldn't work.

Andrew Huberman: That might seem a little bit counterintuitive because I and everybody else has the experience of picking up your phone. You're like, "I'm only going to spend a minute. I'm going to just check what's on Instagram." And all of a sudden you're going down this rabbit hole of one thing, and then it's 30 minutes later and you're like, "Goodness, I got to get ready for work."

Marc Berman: But the involuntary attention that you were talking about before is the kind of thing that cues you to something and then you go down that direction. Or I would say that social media is not softly fascinating. It's harshly fascinating. It's grabbing you and not letting you mind wander or think about anything else. It's grabbing all of your attentional resources. And I would say it does that not by taking us typically down rabbit holes, but it's not like you spend a lot of time on one post. You might go into the comment section if you're interested in that, but it's the fact that you have—

Andrew Huberman: I'm imagining now that there's some resource in the brain that's a combination of catecholamines, dopamine, norepinephrine, certainly, plus a bunch of neural network metabolism stuff. It will never be one thing, it's not going to be like a molecule. And depending on how well rested we are, we go into the day with a certain amount of directed attention units that we can spend. Everything you're telling us today is that going into a fractal, a.k.a. nature environment, allows us to come off the spending of our directed attention.

Marc Berman: That's right.

Andrew Huberman: And it also seems to reset the directed attention account. Are there any data that speak to whether or not it just allows us to not spend, or whether or not it actually replenishes this directed attention capability?

Marc Berman: Yeah, it's a good question.

Andrew Huberman: Or does it even extend capabilities? Does it take you above your baseline? Is it an investment? Lately, I think not so much about dopamine per se. I think about are you spending your dopamine down or are you investing your dopamine? I would say, unfortunately, I don't have a good answer for it. I'm not sure. It might actually expand your store. You might be getting interest.

Marc Berman: So one of the things we kind of struggle with a little bit is, is nature boosting us a lot, or is urban fatiguing us, depleting us? And I think both things are kind of at play there.

Andrew Huberman: I have a whole set of questions popping to mind about sleep states and deep sleep being more like fractal environments and rapid eye movement sleep being more like reality and therefore more challenging. But I'm going to just shelve those and maybe we'll get back to them. Maybe we won't. I want to make sure that I understand correctly what the protocol, for lack of a better word, would be. Get out into nature. Ideally move.

Marc Berman: Yes.

Andrew Huberman: For about 20 minutes minimum.

Marc Berman: Yep.

Andrew Huberman: And ideally you remove yourself from phone. What if you have to make a phone call while you're doing it?

Marc Berman: You don't want to do it. And I'd even say, I know you were saying you like to put the earbuds in. Sometimes I would say you don't want the earbuds in. You want all of your attentional capacity or involuntary attention to be captured by that environment.

Andrew Huberman: Okay. Great.

Marc Berman: I kind of joke with my students about this a little bit. I would say, "How many of you study with listening to music?" And a lot of students raise their hand. I said, "Okay, how many of you want to take the exam listening to music?" Nobody raised their hand. I would say, "Well, that's not consistent." It's not because the students are not smart. It's that studying sucks, and listening to music just makes it more pleasurable, but you're taking away attentional resources that could be used for the studying by listening to music. On the flip side, I want you to be fully engaged with nature. I want your involuntary attention to be just automatically captured by this nature stimulation. I don't want anything else interfering with that. I think that's how you're going to get the most bang for your buck. In fact, we did these studies where I wasn't sure how it was going to work. We took participants who are diagnosed with clinical depression. And this was kind of mean, but I think important. We had them walk in nature too. But before these participants went for a walk in nature, we had them think about a negative thought or memory that's been bothering them to try to induce rumination, to get them ruminating. We thought, maybe if you go for a walk alone in nature and you're restoring your attention, maybe they're going to ruminate even more. That is going to hurt performance. And we found just the opposite. Actually, these participants with clinical depression who we had induced to ruminate got even stronger benefits walking in nature than our non-clinical sample.

Andrew Huberman: On working memory?

Marc Berman: On working memory. You can imagine participants that are struggling with depression and rumination, their working memory is not as good because you've got cognitive resources devoted to these negative thoughts that are just repeating over and over again. You don't have your full bank account of attention because you're spending it on the rumination. We found that for these participants, the effects were stronger in improving their attention and working memory. I think part of that might be that it's actually giving them some of the attentional resources necessary to deal with the rumination.

Andrew Huberman: Super interesting. I know rumination is something that many people, depressed or not, struggle with. I've long thought, and I'm certainly coming to this conclusion with each successive year of my life, that distraction is the enemy. The ability to drop into work, creative work, or prepping a podcast, or reading papers, or taking a walk with somebody, having a conversation with somebody because relationships are important too, and just being able to be fully present to that is the basis of a great life. Even if you're dealing with challenge. It's that when we spread ourselves out across all these different modalities, no good comes of it.

Marc Berman: That's right.

Andrew Huberman: And like any destructive force that's really bad, it's the fact that we don't notice that we were absent for large swaths of it. And that it becomes so pervasive in society that it's not also frowned on. I actually put social media on an old phone. That's the only way I can access social media. Somebody sends me something by way of social media, I don't do it. Because, I don't know what the best analogy is. It's like someone who's trying to eat clean and you're constantly handing them junk food. I enjoy social media, but I like to make it a designated time. So getting out for a walk in 20 minutes. And put the phone in a box. Put the phone away. The whole basis here seems to be allowing your brain to go into its necessary state to reset.

Marc Berman: Maybe.

Andrew Huberman: This state of getting into nature, high fractal environments, is similar or should be similar to the way that we've started to talk about sleep. Prior to 2015, maybe it was 2018, the notion was sleep when you're dead. Matt Walker from UC Berkeley with the book *Why We Sleep* transformed what we now understand. I and others have been arguing that people need sleep. Now I think everyone understands if you don't sleep, your mental health, your physical health, your performance drops dramatically. You need sleep. Matt has educated us that you need slow wave sleep, you need rapid eye movement sleep. Maybe we also need these high fractal environments. And the fact that they come in their best form through walks in nature when we're not doing anything else, just like you wouldn't want to bring the phone into the bedroom late at night because you're not going to get your deep sleep. I love the idea that these waking states become better understood as requirements. We understand so much about sleep, slow wave sleep, growth hormone, REM sleep, emotional repair. Everyone now is like, "Cool, we need sleep. Here are the different states of sleep." We actually know very little about waking states and the requirement for different waking states. If you stay up all night, you entirely expect to not be at your best the next day. But I have a feeling that based on your work, we are doing all sorts of things that are making us far less than our natural best.

Marc Berman: That's right.

Andrew Huberman: And that some of us who are clinically diagnosed with things—I haven't been clinically diagnosed with ADHD. If anything, I'd probably veer more towards the OCD side of things when it comes to work. But my guess is that if we understand and engage in the proper waking states, our lives are going to improve markedly, irrespective of whether or not we need medication. That can only be determined when we're doing the right behavioral things. So what are your thoughts? This is a big question, but what are your thoughts on really starting to understand what the different waking states are and our requirements for waking states? Because I feel like that's pretty much what your work is about.

Marc Berman: Yeah, that's right. I think the social media and things on the phone are kind of like the junk food. They're just ruining our waking states to a large extent. What we're talking a lot about with this attention restoration theory and walking in nature is that we need breaks during your waking time. If we want to get into a state where we are going to be able to concentrate well, maybe you have to take the nature walk first to kind of recharge the battery at the beginning of the day. So I think there are two elements. One is that there's a lot of stuff that we're doing during our waking hours that's depleting directed attention, and we want to mitigate a lot of that stuff. The other thing is that you can't work 10 hours straight. I don't think people really can direct their attention for 10 hours straight.

Andrew Huberman: Not continuously.

Marc Berman: Not continuously.

Andrew Huberman: In talking to a lot of writers, because I've been working on this book, most writers who are career writers will say that the most number of hours that they can do really focused writing per day on a regular basis is four. Some even say three. Some say five, but four seems to be the average. Their entire day and night is dedicated to creating that four hours, typically in the morning, although some wrote at night, most wrote early in the morning. After four hours, they are saturated. The brain just can't do it.

Marc Berman: Right.

Andrew Huberman: So I think there's this element of during our waking hours, protecting directed attention, and then also doing these nature interventions as your breaks. I love this. I'm big on getting sunlight in the morning. I try to see a horizon when I do it. The reason I don't talk about that so broadly is many people don't live in environments where they can catch a horizon. I go up on my roof through a trap door. I don't want people falling off roofs, and you'd be amazed what people do with information. At the same time, if I don't do that, I find it very difficult to ratchet into work in the same way.

Marc Berman: I think, again, to take a step back, what I think is so important about your work is that you've identified at least one and clearly several ways that we can reset our levels, maybe even improve our abilities at directed attention. I don't want to demonize social media. But social media is a commercial product that we're engaging in. We get returns in likes, follows. Some people get paid on there, but for the most part, it's a business. We're the customer. They're the owner. It's using directed attention. It's not a restful activity. You can choose to spend your directed attention allocation on that, but then you're going to have less for your work or for other things.

Andrew Huberman: So is it fair to say that low cognitive demand activities are not always restorative?

Marc Berman: That's right.

Andrew Huberman: I think people need to really understand that and hear that. I think because when I think about, like, yesterday I recorded a solo on the podcast and those are extremely—I don't use a teleprompter except for ads because those have proper wording for legal reasons. The amount of attentional demand is immense. I didn't do this, but in the past I would finish up, go home, and I would find that scrolling social media feels relaxed. You can do it recline. It's passive participation unless I'm posting or commenting. It's like maybe use my thumb. But even though it's low cognitive demand, it's draining. That's what you're saying.

Marc Berman: Exactly. Steve and I wrote this paper back in 2010. Back then, television was still the kind of low cognitive load activity that we thought was not restful. There are all these studies on television. People watching television after they watch for a couple hours report being fatigued and being irritable.

Andrew Huberman: Does cognitive performance decline after watching?

Marc Berman: Cognitive performance decline. So even though it's low cognitive load, it's depleting of directed attention.

Andrew Huberman: I'm really extreme about this stuff, and I'm excited to be able to incorporate more knowledge toward creating better opportunities for directed attention to the right things and not depleting that. I'm so maniacal that before I'll do a solo, I'll tell my assistant when he comes to the house in the morning, "Please don't talk to me today. I'm sorry, I don't want to be rude, but I need to keep rehearsing it in my head." I need to keep not the specific words but the concepts in mind. I'm literally thinking about the structure of the vagus nerve constantly for usually about 48 hours before, in the same way that you would obsess over something. Once it's done, it's done. But anything that's introduced there, like having to make a decision about what to eat for breakfast, is interference. The brain is amazing, but we're not that great at using our brain to its best advantage always.

Marc Berman: Well put.

Andrew Huberman: I want to make sure that we get back into this discussion about rumination. So you discovered that depressed people ruminate about their problem in nature in a way that allows them to dump the problem.

Marc Berman: We don't know if people with depression ruminate about the problem. In the experiment, we kind of forced them to ruminate to see if people are in this ruminative state, would nature still have a benefit? And it turns out that it did. One thing that we were wondering about is, do people just think less about their problems in nature than the urban environment? We found that wasn't true. This is actually work that we did with Ethan Cross, and my wife, Catherine Kirpin, was also an author on the study. We also thought that maybe interacting with nature might put you in this more third-party distance kind of state. So instead of saying "I'm so unhappy," you'd say "Mark is unhappy," this distanced state. We didn't find evidence of that either. It wasn't that people thought about their problems from a more distanced perspective in nature. So what I think is happening is that we just increased their directed attention. And when you increase directed attention, you're able to do lots of things. Maybe they could just deal with the ruminations better because they had more cognitive resources to deal with those problems.

[Andrew Huberman takes a break to acknowledge a sponsor.]

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[Discussion resumes.]

Andrew Huberman: You mentioned impulsivity, aggression, and the probability of committing a crime. You have some data that there are these ways of reducing impulsivity more broadly. I don't think impulsivity is something that most people think they deal with. But I'll tell you, if you've ever found yourself picking up your phone just because everyone else did, that's impulsivity. By the way, I think perhaps I've been a little bit unfair to social media, and I've spared that equally or maybe even more pernicious thing of modern life, which is texting. It's amazing to me on a plane how hard it is for people to disengage from texting. It's also amazing to me how we can all get into three or four conversations over text, or three or four conversations with one person within a text thread. If that were converted into actual dialogue, it would be crazy. It would be like switching back and forth between four different conversations. That party is nuts. But in the form of texting, it's like we're doing it. Are there any data on what texting is doing to directed attention?

Marc Berman: I haven't seen any on it, but again, I would say it's got to be depleting. There was some interesting work, actually, I think by one of your colleagues at Stanford, Anthony Wagner, who did work on these multimedia multitaskers. So people that text and are doing email or social media and something on the computer, like you're using multiple media devices simultaneously. Does that train attention or does it deplete attention?

Marc Berman: And I think those studies are quite evident that it depletes attention. It's not training people's attention. It's just depleting their attention. So I would say, yeah, managing all those conversations is going to be very taxing of directed attention.

Marc Berman: Again, I'm not somebody who's totally against smartphones. I have a smartphone. I don't do social media, but I do text a lot. I guess I try not to always be so fast. I say sometimes I'm just going to have my time and not always be so fast to respond. But it's hard. It's very difficult. You have to be really mindful and protective of your directed attention.

Andrew Huberman: And people get angry if they have an expectation of response latency and then you depart from that. Which is just nerd speak for sometimes I'll text back fast. Sometimes it will take me several weeks or months.

Marc Berman: Right.

Andrew Huberman: I think that's starting to normalize a little bit because of the sheer volume of communication that people are getting. A few years ago, that was considered rude. I've heard more and more discussions about it. There's a very popular podcast for women where the host was talking about this the other day. Someone sent it to me. They said, "The texting three weeks later thing is becoming a norm." I think some people are just bombarded with text messages.

Marc Berman: Right.

Andrew Huberman: I guess our species is really good at creating technologies and then figuring out we need to backtrack a little bit.

Marc Berman: Right. Because all the programs to like – the program Freedom, for instance, which shuts down the internet for a certain interval of time on your computer. That was great. Hardly anyone uses it anymore.

Andrew Huberman: Yeah. And hardly any of the people I know who used to use it use it anymore. Forgive me, Freedom designers. But it starts to just disappear because the culture drifts in a new way.

Marc Berman: Right.

Andrew Huberman: And people like Cal Newport or you who don't have social media, or me who put social media on a separate phone and takes a month to reply to a text unless it's urgent, we're considered the weirdos.

Marc Berman: Yeah. So it's hard. But again, it's you know, I've seen people that like an email where they'll have an auto reply that just says, "I'm not going to respond really quickly" or "only respond to email at this time and this time." And I think that makes sense, because we have to protect our directed attention. We're just not going to be good functioning humans if we're just constantly being depleted.

Andrew Huberman: I read a study from Wendy Suzuki's lab at NYU a few years ago that people that do 13 minutes a day of mindfulness meditation, so basically sitting or lying down, closing one's eyes, focusing on their breathing and constantly refocusing their attention as it drifts back to a location kind of like right in the middle of their forehead. They observed improvements in memory tasks, but actually decrements in sleep were mentioned there, especially if they did it too late in the day. And meditation to me always seemed like a focusing exercise. So while it's relaxing because you're not jogging or socially engaging, it's cognitively demanding because you have to constantly bring your attention back. So for many years, we thought of meditation as a reset. I think of meditation as focus training.

Marc Berman: Yes. Not a reset. What you're talking about with nature walks is a reset.

Andrew Huberman: Yeah.

Marc Berman: And it's interesting because there was a paper, Tang, I can't remember first name, and Michael Posner. They did some meditation results and they found these improvements in attention after meditation. And they contacted me because I was doing this nature stuff. They asked me, "Do you think it's the same mechanism?" And I said, "No, I don't think it's the same mechanism." As you're saying, Andrew, this meditation is very, very focused, lots of directed attention. Whereas what I'm talking about in nature is eliminating the need for any directed attention, that it's all just mind wandering and involuntary attention. So I think even though maybe you can get some of the same results at the end, I think they're very different mechanisms.

Marc Berman: What I do find fascinating is that in a lot of ancient meditation practices, often they try to do it in beautiful nature. And I wonder if they knew something, that they could meditate better in this beautiful nature, because while they were using directed attention to meditate, being immersed in the beautiful nature was also restoring directed attention at the same time. So I do wonder sometimes if combining them could get some really interesting results. But being in nature to me is not a meditative process. It's a much more passive cognitive process. So I think we need to distinguish between passive and restorative and passive and depleting.

Andrew Huberman: Yep. And it should be obvious which things fall into which categories.

Marc Berman: Right.

Andrew Huberman: And then there are things that are perhaps passive and restorative, but go beyond restorative. They might even be passive, restorative, and cognitive enhancing when you get back to work.

Marc Berman: Right. Back to focused attention on the real stuff.

Andrew Huberman: And then the scary thought, which is probably true based on just real-world observation, is that passive and depleting activities, when you repeat them over time, aren't just taking away your ability to engage directed attention later that day or the next day, but that over time, the circuitry for directed attention in the brain is probably subject to plasticity in both directions. This is something that I've long been obsessed with. Every neural circuit that we are aware of is available for plasticity. It requires focus, it requires alertness, and it requires sleep. Those are the requirements. But it's also possible that the circuits for focus can strengthen, so you can get better at focusing by focusing.

Marc Berman: Right.

Andrew Huberman: I certainly see that. The more I do focused work, the better I get at it and the longer I can do it. There's a threshold there.

Marc Berman: Yeah.

Andrew Huberman: But also if I take time away from it for a while, I can replenish, but just like exercise, eventually you start to atrophy.

Marc Berman: Right.

Andrew Huberman: And it could be that passive and depleting stuff repeated for enough years brings you to a state of like really true ADHD.

Marc Berman: Yeah. Maybe. Like maybe you fall into clinical ADHD that probably existed before, but maybe we see it so much more now because people... I mean, this is the equivalent of mental obesity.

Andrew Huberman: Basically. Or mental metabolic syndrome. Let's just be direct. Mental obesity. If you don't exercise enough for long enough, chances are you're going to end up overweight or obese. Certainly with metabolic syndrome. Unfortunately, these technology things are addictive. And most addictions just are not healthy. So then it's hard to get out once you start.

Marc Berman: That is an interesting term, mental obesity. There was this interesting paper that looked at how our collective intelligence, how our collective attention span has changed. They've looked at a short time window, but like a tweet hashtags, maybe they used to last for 40 hours, be popular. Now it's down to 20 hours. If you look at movie ticket sales, the most popular movies were popular for three months. Now it's like one and a half months. Maybe our collective attention span is shrinking a little bit. And we've been wondering, does that mean our individual directed attention has shrunk a little bit, or is there just too many other possibilities that we're too overwhelmed that's causing that? But it is something that is a bit worrisome.

Andrew Huberman: It's not just that we have a lot of things vying for our directed attention. But if we're being so bombarded so much, and as you say, we're getting into these bad modes of thinking, could our directed attention span actually shrink?

Marc Berman: I believe it can and it is out there.

Andrew Huberman: To borrow from the mighty David Goggins, who's the author of *Can't Hurt Me*, and he's been on this podcast and a real proponent of doing hard things every single day, not because he wants to do them, but precisely because he doesn't want to do them. Forcing upon himself real discipline. He's emblematic of that. He's also said, and this should be reassuring to people, that nowadays it's easier than ever to be exceptional because all you have to do is overcome the urge to be on your phone as much, run a bit more. Maybe what we're going to select for are the people who are very organized about their engagement with phones and social media. I will say coming from the Bay Area, I know a number of people who work for and have founded very large social media platforms. They're not on their phones all day.

Marc Berman: Right. They're definitely not. And their kids aren't either.

Andrew Huberman: Their kids aren't either. So you're a father of four. Are there things that you do with your kids to encourage the buildup and reinforcement of these circuits? Their brains are still plastic. And a lot of people listening to this have kids or are kids and would like to know what they should do. Is it exactly what adults should do?

Marc Berman: I try to practice what I preach. It's hard because all of their friends have the technologies too. My oldest daughter does have a smartphone, but she doesn't have any social media. She uses it mostly to text her friends and play Duolingo or something like that. I try to get them to go out in nature as much as possible. Sometimes they're hesitant, they don't want to do it, but we definitely try to get them outside as much as possible. Even when we get to go on vacation once in a while, my wife's family, we're fortunate, they have a little cabin in Northern Ontario that we go to and there's really no internet there. The kids are just running around with their cousins and playing in the lake and doing just normal kid things.

Marc Berman: I think you had Jonathan Haidt on the podcast and he talked about this. He said the kids have to have more free play. The thing that I would add to what Jonathan is saying is I would say you want them to have more free play in nature. And we want them getting out of nature more. And I think, back to David Goggins, I do agree that we should do hard things. And I think taking breaks in nature actually allows us to do more hard things. Just like you can't lift weights continuously all day long, every day, you've got to rest and you got to take good rest. And I think the nature breaks are the good mental rest, which is going to allow you then to later do the heavy cognitive work better. But many of us are not taking good rest breaks. We're taking bad rest breaks. And I think if we can eliminate those bad rest breaks and substitute in the good nature rest breaks, people are just going to be much healthier cognitively, physically, and socially.

Andrew Huberman: I'm going to offer something controversial, but with a purpose. I did an episode on alcohol where the conclusion was zero is better than any and two a week is probably fine. And yes, it's poison. And it remains one of our most popular episodes. But even though I'm not a drinker, you have to wonder whether the doing away with happy hour, which used to be every day at the end of work, created this gap for passive depleting stuff to come in. It raises the question of, was happy hour restorative?

Andrew Huberman: To give people a clear sense of how pervasive happy hour with alcohol was, when I was a graduate student at Berkeley and was at Tolman Hall, I was told that up until just three years before, so that was in 1998, it was customary for people to gather in the library for drinks every day at the end of the day. For many decades prior, the founders, Frank Beach and all those guys, used to get together and get really drunk at the end of each day and go home, walk home hopefully, not drive home, and then spend time with their families and then get up the next morning, drink coffee and go back to work. So alcohol culture, drinking culture was a big part of how people socialized and decompressed at the end of the day. We know it's not good for you. You'll live a shorter life and it has a bunch of other issues. But the point is, I think for many people who have families, but especially who don't have families, the number of healthy ways to reset in the evening, to reset on a weekend in non-destructive ways, has become more limited. In part because what's offered to us as passive restoration, I'm realizing today is passive depletion. So do we bring back happy hour? Maybe with non-alcoholic beverages or something.

Marc Berman: I think the happy hour is probably good socially, but I'm not sure it was so good for directed attention. Do they still do a happy hour in your department? You're chair of a department at University of Chicago.

Andrew Huberman: They used to do graduate student happy hour every Friday when I was a graduate student.

Marc Berman: Wow. And a volleyball game. And then people would go out to dinner.

Andrew Huberman: Yeah. And this was prior to smartphones. Right as smartphones showed up because it was 2000 when I started my PhD. It was really nice. I didn't always go. I was often in lab late working, but I would go sometimes. I feel like being on one's phone is not that. It's not a volleyball game with friends. It was a friendly volleyball game, meaning if you weren't good at volleyball, people didn't give you a hard time. And then people would go out for dinner and drinks.

Marc Berman: We do do happy hours once in a while. I think it's kind of funny. After COVID, I felt like students didn't always know how to interact with faculty anymore. There was this weird dynamic. So the happy hours have been a good way to reset and show that we're all colleagues and help students to interact more with faculty and faculty to interact more with students.

Marc Berman: I think one thing about the reset is, I didn't say this, but I think the going in nature also has to be solitary to really get the benefit. If you're going with a friend, you're going to be chit-chatting with a friend. That's going to take directed attention. When I take my kids in nature, it's good for my kids, but I don't count that as necessarily a restorative experience for me.

Andrew Huberman: You're tracking their positions. You've got four little ones. So that's your evolutionary task.

Marc Berman: So I have to carve out time where I can go on my own. I think there's different buckets. There's a bucket for getting the good social interaction. So I'm not advocating that people build a cabin in the woods and just be there solo. I'm more advocating for these micro doses of nature to bump directed attention up.

Andrew Huberman: Can you bring a dog?

Marc Berman: I think a dog would work well. A dog doesn't require a conversation, no words, no language. As long as a dog is pretty well behaved, I think that would work too. Dogs are part of nature. And some elements to me too, I think dogs are kind of softly fascinating and interesting. But to get the most bang for your buck for these nature experiences, they do have to be solitary.

Andrew Huberman: So minimum 20 minutes. But perhaps on the weekend you can get out for longer if you can't do it every day. I'm not going to say I can't, but I think many people aren't going to manage 20 minutes in nature every single day by themselves.

Marc Berman: Right.

Andrew Huberman: But if you can, it sounds like a terrific thing to do. And certainly people are going to start thinking about new concepts like soft fascination and directed attention and the ability to restore directed attention if something is actually restorative versus passively depleting.

Andrew Huberman: I want to make sure that I ask you about stroke, diabetes, and heart disease. You have some really interesting data that people who take on this practice of getting into nature can actually improve their health outcomes beyond just being able to focus better.

Marc Berman: Right. So there's all this incredible work on physical health benefits of nature. Now, of course, mind and body are united. That's one thing that we talk about in the book, that mind and body are united, and then we have to deal with the environment too. But it's interesting that there have been these studies about these incredible physical health benefits that people get from interacting with nature.

Marc Berman: One of the most incredible ones was a study done by Roger Ulrich in the 1980s. Roger Ulrich was looking at a hospital corridor in this hospital in Philadelphia. He looked at what view did they have out of the window of these hospital rooms. Some of the hospital rooms had views of modest nature like a tree and some shrubs, others were just looking out to a brick wall. It was interesting that patients who were recovering from gallbladder surgery, when they had the view of nature out of their window, this modest view of nature, they recovered from gallbladder surgery a day earlier and they used less pain medication compared to the people that had the view of the brick wall.

Marc Berman: What's cool about this study is that Ulrich didn't have the power to randomly put people in different rooms, but essentially patients were just randomly put into these different hospital rooms. So it's not like healthier people got the views of nature or wealthier people got the views of nature. These patients were just randomly placed into these different hospital rooms. The ones that have the modest view of nature recovered faster from gallbladder surgery and used less pain medication. You got to be thinking, what's up with that? What's the mechanism there? I don't think it's air quality. I don't think the people with the views of nature somehow exercised more. There's something about the aesthetic of nature that can also be physically healing. That's pretty wild.

Marc Berman: We followed up on that in a study that we did in Toronto, which was kind of cool. We had health data from about 30,000 people in Toronto. And then we had two incredible data sets to quantify green space in people's neighborhoods that we then could relate to health. The University of Toronto Forestry Department had a data set where they cataloged every single tree on public land in the city of Toronto. So we had data for 580,000 trees in the city of Toronto. We knew the species of the tree and the diameter of the tree at breast height, basically saying how old the tree was. Then my student Omid Cardan calculated basically how much tree canopy each individual tree provided. Then we had this other data set that was satellite imagery of the whole city of Toronto where we could quantify all the other trees that were in people's backyards.

Marc Berman: From those data, we related the health data to the tree data. For one variable, subjective health: how healthy do people think they are? How healthy do they feel? We found that if you just added one tree on their city block, that was related to a 1% increase in people's health perception. Now that sounds pretty modest, but to get that equivalent benefit monetarily, you'd have to give everybody in that neighborhood $10,000 and have them move to a neighborhood that had a median income that was $10,000 wealthier, or it was also related with being seven years younger. And the tree effect was controlling for age, education, income. So that was pretty interesting.

Marc Berman: We also had data on more objective health measures. Does somebody have a stroke? Do they have diabetes or heart disease? There we found if you increased the amount of trees on the street by one tree per neighborhood, that was related to a 1% reduction in stroke, diabetes, and heart disease. Again, sounds pretty modest, but to get that equivalent benefit monetarily, you'd have to give every household in that neighborhood $20,000, have them all move to a neighborhood that's $20,000 wealthier, or it was also related to being one and a half years younger. Pretty incredible. I can't say causality because it's correlational, but I'm fairly confident in the direction because the worst case scenario is just healthier people choose to live in neighborhoods that have more trees, but they can't be younger, they can't be wealthier, they can't be more educated because we controlled for that. For that study, maybe the mechanism could be air quality, or maybe people are more willing to exercise if there's more trees on the street. But pretty incredible stuff that just increasing the tree canopy a little bit could give these physical health benefits.

Andrew Huberman: That is impressive. For people that don't have the opportunity to plant more trees in their neighborhood, does getting and tending to an indoor plant have any positive effects?

Marc Berman: People have found some effects of having indoor plants, not necessarily to these physical health benefits, but there's some attention benefits of having indoor greenery. There's also been some benefits. Hospitals now are starting to take this seriously, that patients subjectively feel better when there's this greenery around. I've seen other work too that people that are having some procedures that are very painful, bringing greenery into the hospital rooms can be helpful for reducing feelings of pain.

Andrew Huberman: Interesting. I'm about to embark on putting a bunch of plants in my place. I'm also a big fan of fish tanks. As long as you take good care of them, underwater scapes are really cool.

Marc Berman: Yes.

Andrew Huberman: And I like to think, I don't have any data on this, but I like to think that they are passive and restorative. Staring at a fish tank is a lot like being in a dream.

Marc Berman: Yeah. In Toronto, there's a Ripley's Aquarium and they have this tank that's got kelp. You can see the kelp moving in the water. It definitely feels very restorative. And watching the fish swim around also feels very, very restorative.

Andrew Huberman: The feeling that might be familiar to people that visited the Monterey Bay Aquarium or this aquarium that you're describing is when the tanks are at eye level or higher, it puts you into this other world. Like you're at the bottom of the ocean or you're in the ocean.

Marc Berman: Yes.

Andrew Huberman: But the feeling that's always striking to me is when you leave an aquarium and you're out into the real world again, it feels so different. It's what you take away from it. That's equally interesting in the same way that when you walk out of a really great movie, the world feels different. It feels lighter, brighter. It's physically brighter, but there's really something to it. The contrast between experiences, which is so much of what we're talking about today.

Andrew Huberman: I think a lot of people who have some aesthetic sense will be familiar with the experience of seeing a building or walking into a space and feeling, "Oh, this feels good" or "This doesn't feel right." Sometimes they can point to the clutter or the lack of whatever it is. Some people are more design oriented. What's this phrase? It's the feng... feng shui.

Marc Berman: Feng shui.

Andrew Huberman: Feng shui. What do we know about nature and physical spaces and how they impact how we feel or even how we think?

Marc Berman: It's a really interesting question. There are a couple of interesting things that we've done that are related to this. One design concept that people talk about quite a bit now is this idea of biophilic design. That's trying to mimic patterns of nature in architecture. You can imagine a Gaudi building in Barcelona that's got all the curves. Gaudi was trying to mimic nature in a lot of his buildings and people really like that kind of architecture.

Marc Berman: We collaborated with an architect, Alex Coburn, and we took a bunch of building facades and had people look at these facades and rate how much they like these buildings and building interiors. Then we also had them do a game on the computer where we'd show them a few of these architectural scenes on the screen and they'd have to move them around, lumping the ones that are most similar together and lumping different ones somewhere else. When we analyzed the data, we saw something really interesting. People lumped together a lot of this architecture that had a lot of the fractal patterns on one side and other kinds of architecture that was more brutalist with the straight lines on the other side. When we had another set of people rate these images for how natural they thought they were, people were actually using naturalness to make these similarity judgments. This suggests that even in an architectural scene, people will see nature in a building and it may not even be conscious, and they like that kind of architecture better, they find it more comforting. So when we're talking about a nature revolution like we do in the book, it's maybe not just about putting real nature in, but even building spaces trying to mimic the patterns of nature might also have some benefits.

Marc Berman: Another student of mine, Kate Schertz, led another set of studies where we collaborated with a foundation that was called TKF Foundation, now it's called Nature Sacred. This foundation built many parks in the Baltimore, D.C., Annapolis, Maryland area. They built like a hundred of these parks. What they also do in these parks is they would put a bench, this characteristic bench, in the park and underneath the bench was a journal. People could write things in the journal. I found this foundation and I got a small grant from them to do some research. They transcribed all these journal entries digitally and we also had pictures of these parks.

Marc Berman: One thing we did is we ran a topic model on these journal entries to see what are some themes that people are talking about. A lot of these parks were actually near churches or hospitals. So people wrote concepts related to religion. They wrote things about nature. And they also wrote things related to spirituality. In one analysis, we had another set of people rate the parks for how natural they were based on the pictures. We found that if the park was rated as being more natural, people actually wrote more about things related to naturalness. Not too surprising, but a nice sanity check.

Marc Berman: What was even more surprising is with computer vision algorithms, we could quantify the amount of curved edges in these park pictures. It turns out if the park had more curved edges in it, people wrote more about topics related to spirituality and their life journey.

Andrew Huberman: Wild.

Marc Berman: Pretty wild. It gets wilder. That was very correlational. We thought, maybe there's some confounding variables there. So we did another study where we actually manipulated. We had images that had more curved edges or less curved edges, and also images that were more natural and less natural. We did an online study where we would show people one image and then had them select, when you look at this image, do you think it's related more to nature or time or spirituality?

Marc Berman: And it turns out if the picture had more curved edges in it, people were more likely to say, "Yeah, this picture kind of has me thinking about spirituality in my life journey." So that's causal.

Marc Berman: It gets even crazier because we were kind of wondering, when we looked at some of the images, we were thinking, some of the images that don't have as much curved edge structure, they have more water in them. So maybe there's something about having water that makes you think less about spirituality. I don't know if I believe that, but maybe there's something in there.

Marc Berman: So we did something even crazier. We took these images and we scrambled them. We have this image that looks like a park with trees and some water, and then we scramble all the pixels. Now you can't really tell what it is anymore. It just looks kind of like a Jackson Pollock painting. It turns out if those scrambled images have more curved edges, people also say they think more about spirituality and their life journey. So there's something—we don't know the mechanism—but there's something interesting there about just perceiving these curved edges that has people thinking more about spirituality. So it can't be object related because they're scrambled.

Andrew Huberman: That's right. This is almost reminiscent of the connect-the-dot experiment where if the dots are more distantly placed, it seems to trigger some different form of cognition related to creativity.

Marc Berman: Right.

Andrew Huberman: If nothing else, it's becoming increasingly clear that visual scenes have a profound impact on our cognition. I don't even know what brain network to think of when we think about spirituality. Probably somewhere down the temporal lobe, because if you don't know where something is in the brain, you almost always say it's down the infrotemporal lobe where all the other mysterious stuff is. Super interesting. This also tells me that I need to introduce more curved edges to my home environment.

Marc Berman: And people seem to really like curved edges. Even other species tend to prefer curvature and curved edges.

Andrew Huberman: If you had a magic wand and you could wave that magic wand and have people change one, maybe two behaviors on a daily and weekly basis, on the basis of everything that you've learned from your work and related work, what would you wish with that wand?

Marc Berman: I think a couple of things. One, the easy one is just people need to get out into nature more, and they need to do it especially when they feel mentally fatigued. I think that's easier than saying get off of the devices. It's not going to happen entirely. So forget about that for a moment. But go out in nature and do it without your phone and be engaged with it. If you don't have access to nature, try these simulations. Bring nature into your home. You can even have fake plants in your home. There's been some evidence that even fake plants can work. Get some nature sounds going. Maybe think about where you're going to take your next vacation. Maybe think about going to a national park.

Marc Berman: The other thing—and it's kind of building up in the book—I want to start this nature revolution where we really take this work seriously. I think everybody has this intuition that nature is good for us, but it's sort of like it's an amenity, not a necessity. It would be nice to have, but we don't really need it. If I wanted to wave my magic wand, I would want to change that to know that these experiences are a necessity, not an amenity. It's not just a necessity because of climate change. It's a necessity for us as humans to reach our full potential. We can't reach our full potential without nature.

Marc Berman: When people start feeling the effects, then we need to start changing a lot of things. Schools want to take away recess and playtime outside. That's almost exactly counter to what I would recommend. I would recommend that we actually want to have more recess, and more recess out in nature. Think about this, Andrew. What if school is like an eight-hour day? What if instead of eight hours of instruction, it was six hours of instruction and two hours of a nature break?

Andrew Huberman: I'd go back to school.

Marc Berman: Kids might perform better. It might be revolutionary. Now, sometimes people talk to me about nature schools and doing all the learning in nature. I'm not so sure about that—doing calculus when wind is blowing my papers around—but definitely take a break out in nature. Give the kids a break in nature. They might actually learn more. It might be this win-win where they would actually learn more from less.

Marc Berman: Same thing with work. We would need to redesign schedules around work. Maybe your employees will be more productive if you can give them some of these nature breaks. We have not built the built environment to improve people's psychological well-being. We built the built environment to move goods efficiently, house people efficiently. But when have you ever been in a place where they said, "We built this school to increase people's directed attention" or "We built this school to make people more cooperative"? What we're finding is that interacting with nature does both things. We need to incorporate these natural elements into all built spaces.

Marc Berman: Going on even more, in a city, you want to jam as much nature as possible into cities. I love cities. Cities are great. They're beacons of innovation, wealth. We even find that bigger cities have lower racial biases, and depression is lower in bigger cities per capita. But we can do a lot more. Naturizing cities can be really beneficial. A lot of people don't live in cities. I have family that live in rural areas. They're surrounded by nature, but it's not really nature they can use. It might be more agricultural. So even in these more rural places, you need to think about whether the nature that's actually there is really usable for people to get restoration.

Andrew Huberman: Listen, I absolutely love the work you're doing. I especially love it because it's grounded in data. It's grounded in laboratory data and it's grounded in real world data. I just asked you for two, and I'm very gratified that you offered six, I think. That's very much the sort of answers I tend to give. I'm going to ask you one question, but I end up asking you four. So that's not just welcome, it's invited and encouraged here.

Andrew Huberman: I think the work you're doing is extremely important because it's highlighting these principles of brain function and psychological health that are unaware to most people about themselves and others. Even as a neuroscientist, I like to think of myself as psychologically minded. This notion of passive but depleting—it has never occurred to me until I got familiar with your work and more so during today's conversation.

Andrew Huberman: I also am delighted that you didn't use the word "forest bathing." I want to be very clear—it's not because I don't think forest bathing is a wonderful concept. What is more lovely than bathing in a forest? People maybe with clothes, minimal clothes, maybe no clothes, in the forest, greenery everywhere. We've heard of this incredible set of discoveries from Japanese laboratories about forest bathing. But the problem with the term is that it implies you need a forest, and it implies that you need to bathe, which sounds like a vacation. It sounds like something you have to devote a ton of time to. I'm a big fan of forest bathing as a concept and as a practice, but I really appreciate that your work is focused on what people can do in a real practical sense as we bring more nature into cities, into homes, into rural areas that's accessible.

Andrew Huberman: Hopefully people will forest bathe, continue to, or go out and forest bathe. But what you're talking about is very practical and very feasible for people to get 20 minutes alone, nature walk, maybe with a dog, maybe just alone, disconnect as a way to be able to engage focused attention better. Or who knows, maybe just to get back into life and enjoy non-focused attention, hanging out with your kids or your spouse or friends.

Marc Berman: Right.

Andrew Huberman: Very excited about the book, which comes out soon. We'll put a link to the book in the show note captions. I'm delighted you're doing this work and that you're going to continue to do this work, even though you have the unfortunate honor of being a chair, which means you get a lot of administrative duties. You've still kept up your research. If ever there was an example of where research can really be put to practical use for people, and the book is helping disseminate that, certainly this conversation will as well. It's you and what you're doing. So thank you. I really appreciate it. Come back again and update us on the latest data when there are more data.

Marc Berman: Great. Thanks so much for having me on the podcast.

Andrew Huberman: Great. Will do, and I'll get into nature today.

Marc Berman: Great. Thank you.

Andrew Huberman: Thank you for joining me for today's discussion with Dr. Marc Berman. To learn more about his work and to find a link to the presale of his new book, please see the show note captions.

Andrew Huberman: If you're learning from and enjoying this podcast, please subscribe to our YouTube channel. That's a terrific zero-cost way to support us. In addition, please follow the podcast by clicking the follow button on both Spotify and Apple. On both Spotify and Apple, you can leave us up to a five-star review, and you can now leave us comments. Please also check out the sponsors mentioned at the beginning and throughout today's episode. That's the best way to support this podcast.

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Andrew Huberman: For those of you that haven't heard, I have a new book coming out. It's my very first book. It's entitled *Protocols: An Operating Manual for the Human Body*. This is a book that I've been working on for more than five years, based on more than 30 years of research and experience. It covers protocols for everything from sleep, to exercise, to stress control, protocols related to focus and motivation. I provide the scientific substantiation for the protocols that are included. The book is now available by presale at protocolsbook.com. There you can find links to various vendors. Again, the book is called *Protocols: An Operating Manual for the Human Body*.

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Andrew Huberman: Thank you once again for joining me for today's discussion with Dr. Marc Berman. And last, but certainly not least, thank you for your interest in science.