The following is a conversation with Matt Walker, sleep scientist, professor of neuroscience and psychology at Berkeley, author of "Why We Sleep" and the host of a new podcast called the Matt Walker Podcast. It's 10 minute episodes a couple of times a month, covering sleep and other health and science topics.

I love it and recommend it highly. It's up there with the greats like the Huberman Lab Podcast with Andrew Huberman and I think David Sinclair is putting out an audio series soon too. I can't wait to listen to it. I'm really excited by the future of science in the podcasting world.

To support this podcast, please check out our sponsors, Stamps.com, Squarespace, Athletic Greens, BetterHelp and Onnit. Their links are in the description. As a side note, let me say that to me, a healthy life is one in which you fall in love with the world around you, with ideas, with people, with small goals and big goals, no matter how difficult, with dreams you hold onto and chase for years.

Life should be lived fully. That to me is the priority. That to me is a healthy life. Second to that is the understanding and the utilization of the best available science on diet, exercise, supplements, sleep and other lifestyle choices. To me, science in the realm of health is a guide for we should try, not the absolute truth of how to live life.

The goal is to learn to listen to your body and figure out what works best for you. All that said, a good night's sleep can be a great tool in making life awesome and productive. And Matt is a great advocate of the how and the why of sleep. We agree on some things and disagree on others, but he's a great human being, a great scientist and as of recently, a friend with whom I enjoy having these wide ranging conversations.

This is the Lex Friedman podcast and here is my conversation with Matt Walker. You should try these shades on and see what you look like. - So they are now your shades. And that's not a question. - It's the same thing as Putin took the Superbowl ring and it's now his ring.

(both laughing) - Yeah, one wonders if he was offered it, but they are yours. - When did you first fall in love with the dream of understanding sleep? Like where did the fascination with sleep begin? - So back in the United Kingdom, you can sort of start doing medicine at age 18 and it's a five year program.

And I was at the Queen's Medical Center in the UK. And I remember just being fascinated by states of consciousness and particularly anesthesia. I was thinking, isn't that incredible? Within seconds, I can take a perfectly conscious human being and I can remove all existence of the mentality and their awareness within seconds.

And that stunned me. So I started to get really interested in conscious states. I even started to read a lot about hypnosis and all of these things, hypnosis, even sleep and dreams at the time, they were very esoteric. It was sort of charlatan science at that stage. And I think almost all of my colleagues and I are accidental sleep researchers.

No one, as I recall in the classroom when you're sort of five years old and the teacher says, "What would you like to be when you grow up?" No one's putting their hand up and saying, "I would love to be a sleep researcher." And so when I was doing my PhD, I was trying to identify different forms of dementia very early on in the course.

And I was using electrical brainwave recordings to do that. And I was failing miserably. It was a disaster, just no result after no result. And I used to go home to the doctor's residence with this sort of a little igloo of journals that at the weekend I would sort of sit in and read.

And which I'm now thinking, do I really want to admit this? 'Cause it sounds like I had no social life, which I didn't, I was social leper. But, and I started to realize that some parts of the brain were sleep related areas. And some dementias were eating away those sleep related areas.

Other dementias would leave them untouched. And I thought, well, I'm doing this all wrong. I'm measuring my patients while they're awake. Instead I should be measuring them while they're asleep. Started doing that, got some amazing results. And then I wanted to ask the question, is that sleep disruption that my patients are experiencing as they go into dementia, maybe it's not a symptom of the dementia.

I wonder if it's a cause of the dementia. And at that point, which was, cough, cough, 20 years ago, no one could answer a very simple fundamental question. Why do we sleep? And I at the time didn't realize that some of the most brilliant minds in scientific history had tried to answer that question and failed.

And at that point, I just thought, well, I'm going to go and do a couple of years of sleep research and I'll figure out why we sleep. And then I'll come back to my patients in this question of dementia. And as I said, that was 20 years ago. And what I realized is that hard questions care very little about who asks them.

They will meter out their lessons of difficulty all the same. And I was schooled in the difficulty of the question, why do we sleep? But in truth, 20 years later, we've had to upend the question rather than saying, why do we sleep? And by the way, the answer then was that we sleep to cure sleepiness, which is like saying, we eat to cure hunger.

That tells you nothing about the physiological benefits of food, same with sleep. Now we've actually have to ask the question, is there any physiological system in the body or any major operation of the mind that isn't wonderfully enhanced when we get sleep or demonstrably impaired when we don't get enough?

And so far, for the most part, the answer seems to be no. - So far, the answer seems to be no. So why does the body and the mind crave sleep then? Why do we sleep? How can we begin to answer that question then? - So I think one of the ways that I think about this or one of the answers that came to me is the following.

The reason that we implode so quickly and so thoroughly with insufficient sleep is because human beings seem to be one of the few species that will deliberately deprive themselves of sleep for no apparent good reason, biological. And what that led me then to was the following. Mother nature as a consequence, so no other species does what we do in that context.

There are a few species that do undergo sleep deprivation, but for very obvious, clear biological reasons. One is when they're in a condition of severe starvation. The second is when they're caring for their newborn. So for example, killer whales will often deprive themselves. The female will go away from the pod, give birth and then bring the calf back.

And during that time, the mother will undergo sleep deprivation. And then the third one is during migration when birds are flying trans oceanographic to 3000 miles. But for the most part, it's never seen in the animal kingdom which brings me back to the point. Therefore, mother nature in the course of evolution has never had to face the challenge of this thing called sleep deprivation.

And therefore she has never created a safety net in place to circumnavigate this common influence. And there is a good example where we have, which is called the adipose cell, the fat cell. Because during our evolutionary past, we had famine and we had feast. And mother nature came up with a very clever recipe, which is how can I store caloric credit so that I can spend it when I go into debt?

And the fat cell was born, brilliant idea. Where is the fat cell for sleep? Where is that sort of banking chip for sleep? And unfortunately we don't seem to have one because she's never had to face that challenge. - So even if there's not some kind of physics fundamental need for sleep, that physiologically or psychologically, the fact is most organisms are built such that they need it.

And then mother nature never built an extra mechanism for sleep deprivation. So it's interesting that why we sleep might not have a good answer, but we need to sleep to be healthy is nevertheless true. - Yeah, and we have many answers right now. In some ways, the question of why we sleep was the wrong question too.

It's what are the pluripotent many reasons we sleep? We don't just sleep for one reason. Because from an evolutionary perspective, it is the most idiotic thing that you could imagine. When you're sleeping, you're not finding a mate, you're not reproducing, you're not caring for your young, you're not foraging for food, and worse still, you're vulnerable to predation.

So on any one of those grounds, especially as a collective, sleep should have been strongly selected against in the course of evolution. But in every species that we've studied carefully to date, sleep is present. - So it is important. So you're right. I think I've heard arguments from an evolutionary biology perspective that sleep is actually advantageous.

Maybe like some kind of predator-prey relationships. But you're saying, and it actually makes way more sense what you're saying, is it should have been selected against. Why close your eyes? - Yeah, why? Because, and there was an energy conservation hypothesis for a while, which is that we need to essentially go into low battery mode, power down because it's unsustainable.

But in fact, that actually has been blasted out the water because sleep is an incredibly active process. In fact, the difference between you just lying on the couch, but remaining conscious, versus you lying on the couch and falling asleep, it's only a savings of about 140, 150 calories. In other words, you just go out and club another baby seal or whatever it was, and you wouldn't worry.

So it has to be much more to it than energy conservation, much more to it than sharing ecosystem space and time, much more to it than simply predator-prey relationships. If sleep really did, and looking back, even very old evolutionary organisms like earthworms, millions of years old, they have periods where they're active and periods where they're passively asleep.

It's called lethargics. (laughs) And so what that in some ways suggested to me was sleep evolved with life itself on this planet, and then it has fought its way through heroically every step along the evolutionary pathway, which then leads to the sort of famous sleep statement from a researcher that if sleep doesn't serve an absolutely vital function or functions, then it's the biggest mistake the evolutionary process has ever made.

And we've now realized mother nature didn't make a spectacular blunder with sleep. - You've mentioned the idea of conscious states. Do you think of sleep as a fundamentally different conscious state than awake-ness? And how many conscious states are there? So when you're into it, you're understanding of what the mind can do.

Do you think awake state, sleep state, or is there some kind of continuum? There's a complicated state transition diagram. Like how do you think about this whole space? - I think about it as a state-space diagram, and I think it's probably more of a continuum than we have believed it to be or suggested it to be.

So we used to think absent of anesthesia that there were already three main states of consciousness. There was being awake, being in non-rapid eye movement sleep or non-dream sleep, and then being in rapid eye movement sleep or dream sleep. And those were the three states within which your brain could percolate and be conscious.

Conscious during non-REM sleep is maybe a stretch to say, but I still believe there is plenty of consciousness there. I don't believe that though anymore. And the reason is because we can have daydreams, and we are in a very different wakeful state in those daydreams than we are when we are, as we are now together, present and extraceptively focused rather than intraceptively focused.

And then we also know that as you are sort of progressing into those different stages of sleep during non-REM sleep, you can also still dream. Depends on your definition of dreaming, but we seem to have some degree of dreaming in almost all stages of sleep. We've also then found that when you are sleep deprived, there are even individual brain cells will fall asleep.

Despite the animal being, you know, behaviorally from best we can tell awake, individual brain cells and clusters of brain cells will go into a sleep-like state. And humans do this too. When we are sleep deprived, we have what are called micro-sleeps where the eyelid will partially close and the brain essentially falls lapses into a state of sleep, but behaviorally you seem to be awake and the danger here is road traffic accidents.

So these are the, what we call these sort of micro-sleep events at the wheel. Now, if you're traveling at 65 miles an hour in a two ton vehicle, you know, it takes probably around one second to drift from one lane to the next. And it takes two seconds to go completely off the road.

So if you have one of these micro-sleeps at the wheel, you know, it could be the last micro-sleep that you ever have. But I don't now see it as a set of, you know, very binary distinct, you know, step function states. It's not a one or a zero. I see it more of a, as a continuum.

- Yeah, so I've for five, six years at MIT really focused on this human side of driving question. And one of the big concerns is the micro-sleeps, drowsiness, these kinds of ideas. And one of the open questions was, is it possible through computer vision to detect, or any kind of sensors?

The nice thing about computer vision is you don't have to have direct contact to the person. Is it possible to detect increases in drowsiness? Is it possible to detect these kinds of micro-sleeps or actually just sleep in general? Among other things, like distraction. These are all words that have so many meanings and so many debates, like attention is a whole nother one.

Just because you're looking at something doesn't mean you're loading in the information. Just because you're looking away doesn't mean your peripheral vision can't pick up the important information. There's so many complicated vision science things there. So I wonder if you could say something to, they say the eyes are the windows to the soul.

Do you think the eyes can reveal something about sleepiness through computer vision, through just looking at the video of the face? And Andrew Huberman and I, your friend, have talked about this. I would love to work on this together. - You should do. - It's a fascinating problem. But drowsiness is a tricky one.

So there's what kind of information? There's blinking and there's eye movement. And those are the ones that can be picked up with computer vision. Do you think those are signals that could be used to say something about where we are in this continuum? - Yeah, I do. And I think there are a number of other features too.

I think aperture of eye, so in other words, partial closures, full closures, duration of those closures, duration of those partial closures of the eyelid. I think there may be some information in the pupil as well, because as we're transitioning between those states, there are changes in what's called the automatic nervous system, or technically it's called the autonomic nervous system, part of which will control your pupillary size.

So I actually think that there is probably a wealth of information. When you combine that probably with aspects of steering angle, steering maneuver, and if you can sense the pressure on the pedals as well, my guess is that there is some combinatorial feature that creates a phenotype of you are starting to fall asleep.

And as the autonomous controls develop, it's time for them to kick in. - Some manufacturers, auto manufacturers, sort of have something, beta version, or maybe an alpha version of this already starting to come online, where they have a little camera in the wheel that I think tries to look at some features.

- Almost everybody doing this, and it's very alpha. So, you know, the thing that you currently have, some people have that in their car, there's a coffee cup or something that comes up that you might be sleepy. The primary signal that they're comfortable using is a steering wheel reversals.

So basically using your interaction with the steering wheel and how much you're interacting with it as a sign of sleepiness. So if you have to constantly correct the car, that's a sign of you starting to drift into micro sleep. I think that's a very, very crude signal. It's probably a powerful one.

There's a whole nother component to this, which is it seems like it's so driver and subject dependent. How our behavior changes as we get sleepy and drowsy seems to be different in complicated, fascinating ways where you can't just use one signal. It's kind of like what you're saying, there has to be a lot of different signals that you should then be able to combine.

The hope is there's the searches for like universal signals that are pretty damn good for like 90% of people. But I don't think we need to take necessarily quite that approach. I think what we could do in some clever fashion is using the individual. So what you and I are perhaps suggesting here is that there is an array of features that we know provide information that is sensitive to whether or not you're falling asleep at the wheel.

Some of those, let's say that there are 10 of them. For me, seven of them are the cardinal features. For you, however, six of them, and they're not all the same sort of overlapping, are those for you. I think what we need is algorithms that can firstly understand when you are well slept.

So let's say that people have sleep trackers at night and then your car integrates that information. - That would be amazing. - And it understands when you are well slept. And then you've got the data of the individual behavior unique to that individual, snowflake-like, when they are well slept.

This is the signature of well-rested driving. Then you can look at deviations from that and pattern match it with the sleep history of that individual. And then I don't need to find the sort of, you know, the one size fits all approach for 99% of the people. I can create a very bespoke, tailor-like set of features, a Savile Row suit of sleepiness features.

You know, that would be my, if you want to ask me about moonshots and crazy ideas, that's where I'd go. But to start with, I think your approach is a great one. Let's find something that covers 99% of the people. Because the worrying thing about microsleeps, of course, unlike, you know, drugs or alcohol, which, you know, certainly is a terrible thing to be behind the wheel, with those, often you react too late.

And that's the reason you get into an accident. When you fall asleep behind the wheel, you don't react at all. You know, at that point, there is a two-ton missile driving down the street and no one's in control. That's why those accidents can often be more dangerous. - Yeah, and the fascinating thing is, in the case of semi-autonomous vehicles, like Tesla Autopilot, this is where I've had disagreements with Mr.

Elon Musk, and the human factors community, which is this community that one of the big things they study is human supervision over automation. So you have like pilots, you know, supervising an airplane that's mostly flying autonomously. The question is, when we're actually doing the driving, how do microsleeps or general, how does drowsiness progress and how does it affect our driving?

That question becomes more fascinating, more complicated, when your task is not driving, but supervising the driving. So your task is to take over when stuff goes wrong. And that is complicated, but the basic conclusions from many decades is that humans are really crappy at supervising because they get drowsy and lose vigilance much, much faster.

The really surprising thing with Tesla Autopilot, it was surprising to me, surprising to the human factors community, and in fact, they still argue with me about it, is it seems that humans in Teslas with Autopilot and other similar systems are not becoming less vigilant, at least with the studies we've done.

So there's something about the urgency of driving. I can't, I'm not sure why, but there's something about the risk, I think the fact that you might die is still keeping people awake. The question is, as Tesla Autopilot or similar systems get better and better and better, how does that affect increasing drowsiness?

And that's when you need to have, that's where the big disagreement was. You need to have driver sensing, meaning driver facing camera that tracks some kind of information about the face that can tell you drowsiness. So you can tell the car if you're drowsy so that the car can be like, you should be probably driving or pull to the side.

- Right, or I need to do some of the heavy lifting here. - Yeah, so there needs to be that dance of interaction of a human and machine. But currently it's mostly steering wheel based. So this idea that your hands should be on the steering wheel that's a sign that you're paying attention is an outdated and a very crude metric.

- I agree, yeah. I think there are far more sophisticated ways that we can solve that problem if we invest. - Can I ask you a big philosophical question before we get into fun details? On the topic of conscious states, how fundamental do you think is consciousness to the human mind?

I ask this from almost like a robotics perspective. So in your study of sleep, do you think the hard question of consciousness, that it feels like something to be us, is that like a nice little feature, like a quirk of our mind, or is it somehow fundamental? Because sleep feels like we take a step out of that consciousness a little bit.

So from all your study of sleep, do you think consciousness is like deeply part of who we are or is it just a nice trick? - I think it's a deeply embedded feature that I can imagine has a whole panoply of biological benefits. But to your point about sleep, what is interesting if you do a lot of dream research, and we've done some, it's very, very rare at all, in fact, for you to end up becoming someone other than who you are in your dreams.

Now, you can have third-person perspective dreams where you can see yourself in the dream as if you've risen above your physical being. But for the most part, it's very rare that we lose our sense of conscious self. And maybe I'm sort of doing a sleight of hand because it's really what I'm saying is it's very rare that we lose our sense of who we are in dreams.

We never do. Now, that's not to suggest that dreams aren't utterly bizarre and I mean, when you slept last night, which I know may have been perhaps a little less than me, but when you went into dreaming, you became flagrantly psychotic. And there are five essentially good reasons. Firstly, you started to see things which were not there, so you were hallucinating.

Second, you believe things that couldn't possibly be true, so you were delusional. Third, you became confused about time and place and person, so you're suffering from what we would call disorientation. Fourth, you have wildly fluctuating emotions, something that psychiatrists will call being affectively labile. And then how wonderful, you woke up this morning and you forgot most, if not all of that dream experience, so you're suffering from amnesia.

If you had to experience any one of those five things while you're awake, you would probably be seeking psychological help. So I place that as a backdrop against your astute question, because despite all of that psychosis, there is still a present self nested at the heart of it, meaning that I think it's very difficult for us to abandon our conscious sense of self.

And if it's that hard, the old adage in some ways that you can't outrun your shadow, but here it's more of a philosophical question, which is about the conscious mind and what the state of consciousness actually means in a human being. So I think that that to me, you become so dislocated from so many other rational ways of waking consciousness, but one thing that won't go away, that won't get perturbed or sort of, you know, manacled is this your sense of conscious self.

- Yeah, there's a strong sign that consciousness is fundamental to the human mind. - Or we're just creatures of habit. We've gotten used to having consciousness. Maybe it just takes a lot of either chemical substances or a lot of like mental work to escape that. I mean, it's like trying to launch a rocket.

You know, the energy that has to be put in to create escape velocity from the gravitational pull of this thing called planet earth is immense. Well, the same thing is true for us to abandon our sense of conscious self. The amount of biological, the amount of substances, the amount of wacky stuff that you have to do to truly get escape velocity from your conscious self.

What does that tell us about then the fundamental state of our conscious self? - Yeah, it also probably says that it's quite useful to have consciousness for survival and for just operation in this world. And perhaps for intelligence. I'm one of the, on the AI side, people that think that intelligence requires consciousness.

So like high levels of general intelligence requires consciousness. Most people in the AI field think like consciousness and intelligence are fundamentally different. You can build a computer that's super intelligent. It doesn't have to be conscious. I think that if you define super intelligence by being good at chess, yes.

But if you define super intelligence as being able to operate in this living world of humans and be able to perform all kinds of different tasks, consciousness, it seems to be somehow fundamental to richly integrate yourself into the human experience, into society. It feels like you have to be a conscious being.

But then we don't even know what consciousness is and we certainly don't know how to engineer it in our machines. - I love the fact that there are still questions that are so embryonic because, you know, I suspect it's the same with you. Answers to me are simply ways to get to more questions.

You know, it's questions where, you know, questions turn me on, answers less so. And I love the fact that we are still embryonic in our sense of arguing about even what the definition of consciousness is. But I also find it fascinating, I think it's thoroughly delightful to absorb yourself in the thought.

Think about the brain and we can move back across the complexity of phylogeny from, you know, humans to mammals to sort of birds to reptiles, amphibians, fish, and you can, bacteria, whatever you want. And you can go through this and say, okay, where is the hard line of, you know, what we would define as consciousness?

And I'm sure it's got something to do with the complexity of the neural system, of that I'm fairly certain. But to me, it's always been fascinating. So what is it then? You know, is it that I just keep adding neurons to a Petri dish and I just keep adding them and adding them and adding them.

At some point when I hit a critical mass of interconnected neurons, that is the mass of the, you know, the interconnected human brain, then bingo. All of a sudden it kicks into gear and we have consciousness. - Like a phase shift, phase transition of some kind. - Correct, yeah.

But there is something about the complexity of the nervous system that I think is fundamental to consciousness. And the reason I bring that up is because when we're trying to then think about creating it in an artificial way, does that inform us as to the complexity that we should be looking at in terms of development?

I also think that it's a missed opportunity in the sort of digital space for us to try to recreate human consciousness. We've already got human consciousness. What if we were to think about creating some other form of consciousness? Why do we have to think that the ultimate in the creation of, you know, an artificial intelligence is the replication, you know, of a human state of consciousness?

Can we not think outside of our own consciousness and believe that there is something even more incredible or more complementary, more orthogonal? So I'm sometimes perplexed that people are trying to mimic human consciousness rather than think about creating something that's different. - I think of human consciousness or consciousness in general as this magic superpower that allows us to deeply experience the world.

And just as you're saying, I don't think that superpower has to take the exact flavor as humans have. That's my love for robots. I would love to add the ability to robots that can experience the world and other humans deeply. I'm humbled by the fact that that idea does not necessarily need to look anything like how humans experience the world.

But there's a dance of human to robot connection, the same way human to dog or human to cat connection. There's a magic there to that interaction. And I'm not sure how to create that magic, but it's a worthy effort. I also love, just exactly as you said, on the question of consciousness or engineering consciousness, the fun thing about this problem is it seems obvious to me that 100 years from now, no matter what we do today, people, if we're still here, will laugh at how silly our notions were.

So it's almost impossible for me to imagine that we will truly solve this problem fully in my lifetime. And more than that, everything we'll do will be silly 100 years from now. But it's still, that makes it fun to me because it's like you have the full freedom to not even be right, just to try, just to try is freedom.

And that's how I see-- - Get me that T-shirt, please. (laughing) I love that. - So, and human robot interaction is fascinating because it's like watching dancing. I've been dancing tango recently. And just, it's like, there is no goal. The goal is to create something magical. And whether consciousness or emotion or elegance of movement, all of those things, aid in the creation of the magic.

And it's a free, it's an art form to explore how to make that, how to create that in a way that's compelling. - Yeah, I love the line in "Sense of a Woman" with Al Pacino where he's speaking about the tango. And he said, "Really, it's just freedom "that if you get tangled up, you just keep tangoing on." - I still to this day, I think, well, first or second time I talked to Joe Rogan on his podcast, I said, "We got into this heated argument "about whether 'Sense of a Woman' "is a better movie than 'John Wick'." Because it's one of my favorite movies for many reasons.

One is-- - "Sense of a Woman." - "Sense of a Woman." - Partially, I didn't know that, by the way. I was just gonna-- - You just-- - Yeah, I didn't know if you would actually know of the movie. - Awesome, awesome. No, yeah, I said, "I love the tango scene.

"I love Al Pacino's performance. "It's a wonderful movie." Then Joe was saying, "John Wick is better." So we, to this day, argue about this. - I think it depends on what conscious state you're in that you would be ready and receptive to. But "Sense of a Woman," I think it has one of the best monologues at the end of the movie that has ever been written or at least performed.

- When Al Pacino defends the younger. Yeah, I often think about that. There's been times in my life, I don't know about you, where I wish I had an Al Pacino in my life, where integrity is really important in this life. - It is. - And sometimes you find yourself in places where there's pressure to sacrifice that integrity.

And you want, what is it, Lieutenant Colonel or whatever he was-- - (laughs) Slade. - Yeah, to come in on your side and scream at everyone and say, "What the hell are we doing here?" - Being, unfortunately, British and sort of having that slightly awkward sort of Hugh Grant gene, it's very, very, very at the opposite end of the spectrum of the remarkable feat of Al Pacino at the end of that scene.

But, and yeah, integrity is, it's a challenging thing and I value it much. And I think it can take 20 years to build a reputation and two minutes to lose it. And there is nothing more that I value than integrity. And if I'm ever wrong about anything, I truly don't want to be wrong for any longer than I have to be.

That's what being in some ways a scientist is. You're just driven by truth. And the irony relative to something like mathematics is that in science, you never find truth. What all you do in science is you discount the things that are likely to be untrue, leaving only the possibility of what could be true.

But in math, when you create a proof, it's a proof for, from that point forward, there is truth in mathematics. And I think there's a beauty in that. But I kind of like the messiness of science, because again, to me, it's less about the truth of the answer and it is more about the pursuit of questions.

- But their integrity becomes more and more important and it becomes more difficult. There's a lot of pressure, just like in the rest of the world, but there's a lot of pressures on a scientist. One is like funding sources. I've noticed this, that money affects everyone's mind, I think.

I've been always somebody that I believe money can't, you can't buy my opinion. I don't care how much money, billions or trillions. But that pressure is there and you have to be very cognizant of it and make sure that your opinion is not defined by the funding sources. And then the other is just your own success of, for a couple of decades, publishing an idea and then realizing at some point that that idea was wrong all along.

And that's a tough thing for people to do, but that's also integrity is to walk away, is to say that you were wrong. That doesn't have to be in some big dramatic way. It could be in a bunch of tiny ways along the way. Like reconfigure your intuition about a particular problem.

And all of that is integrity. When everybody in the room believes a certain thing, everybody in the community believes a certain thing to be able to still be open-minded in the face of that. - Yeah, and I think it comes down in some ways to the issue of ego, that you bond your correctness or your rightness, your scientific theory with your sense of ego.

I've never found it that difficult to let go of theories in the face of counter evidence, in part because I have such low self-esteem. - Well, I kind of like that. I've always liked that combination. I have the same. I'm like very self-critical, imposter syndrome, all those things, putting yourself below the podium, but at the same time, having the ego that drives the ambition to work your ass off.

Like some kind of weird drive, maybe, like drive to be better. Like thinking yourself is not that great and always driving to be better. And at the same time, because that can be paralyzing and exhausting and so on, at the same time, just being grateful to be alive. But in the sciences, in the actual effort, never be satisfied, never think of yourself highly.

It seems to be a nice combination. - I very much hope that that is part of who I am, and I remain very quietly motivated and driven, and I, like you, love the idea of perfection, and I know I will never achieve it, but I will never stop trying to.

- So similar to you, which sounds weird because there's all these videos of me on the internet. So I think I just naturally lean into the things I'm afraid of and I'm uncomfortable doing. Like I'm very afraid of talking to people, and just even before talking to you today, just a lot of anxiety and all those kinds of things.

- About talking to me? - Yeah, yeah. - Oh, I like. - Nervousness. Fear in some cases, self-doubt and all those kinds of things but I do it anyway. So the reason I bring that up is you've launched a podcast. - I have. - Allow me to say, I think you're a great science communicator.

So this challenge of being afraid or cautious of being in the public eye and yet having a longing to communicate some of the things you're excited about in the space of sleep and beyond. What's your vision with this project? - I think firstly to that question, like you, I am always more afraid of not trying than trying.

- Yeah. - That to me frightens me more. But with the podcast, I think really, I have two very simple goals. I want to try and democratize the science of sleep. And in doing so, my goal would be to try and reunite humanity with the sleep that it is so desperately bereft of.

And if I can do that through a number of different means, the podcast is a little bit different than this format. It's going to be short form monologues from yours, Julie, that will last usually less than just 10 minutes. And I see it as simply a little slice of sleep goodness that can accompany your waking day.

- It's hard to know what is the right way to do science communication. Like your friend, mine, Andrew Huberman, he's an incredible human being. - Oh gosh. - He does like two hours of, I wonder how many takes he does, I don't know. But it looks like he doesn't do any.

- Yeah, I suspect he's that magnificent of a human being. - When I talk to him in person, he always generates intelligent words, well cited nonstop for hours. So I don't. - He's a Gatlin gun of information and it's pristine. - And passion and all those kinds of things.

So that's an interesting medium. It's funny 'cause I wouldn't have done it the way he's doing it. I wouldn't advise him to do it the way he's doing it 'cause I thought there's no way you could do what you're doing. 'Cause it's a lot of work, but he is like doing an incredible job of it.

I just think it's the same with like Dan Carlin in hardcore history. I thought that the way Andrew's doing it would crush him the way it crushes Dan Carlin. So Dan has so much pressure on him to do a good job that he ends up publishing like two episodes a year.

So that pressure can be paralyzing. The pressure of like putting out like strong scientific statements, that can be overwhelming. Now, Andrew seems to be just plowing through anyway. If there's mistakes, he'll say there's corrections and so on. I just, I wonder, actually I haven't talked to him too much about it.

Like psychologically, how difficult is it to put yourself out there for an hour to a week of just nonstop dropping knowledge? Any one sentence of which could be totally wrong. It could be a mistake. - And there will be mistakes. And I, in the first edition of my book, there were errors that we corrected in the second edition too.

But there will be probabilistically, if you've got 10 facts per page of a book and you've got 350 pages, odds are it's probably not going to be utter perfection out the gate. And it will be the same way for Andrew too. But having the reverence of a humble mind and simply accepting the things that are wrong and correcting them and doing the right thing, I know that that's his mentality.

- I do want to say that I'm just kind of honored to be, it's a cool group of like scientific people that I'm fortunate enough to now be interacting with. It's you and Andrew and David Sinclair has been thinking about throwing his hat in the ring. - Oh, I hope so.

David is another one of those very special people in the world. - So it's cool because podcasts are, it's cool. It's such a powerful medium of communication. It's much freer than more constrained. Like publications and so on, or it's much more accessible and inspiring than like, I don't know, conference presentations or lectures.

And so it's a really exciting medium to me. And it's cool that there's this group of people that are becoming friends and putting stuff out there and supporting each other. So it's fun to also watch how that's going to evolve in your case. 'Cause I wonder, it'll be two a month.

- Or devolve is the answer to that. - Well, I mean, some of it is persistence through the challenges that we've been talking about, which is like- - I think I've got a lot to learn. - Yeah. - But I will persist. - Luke, can I ask you some detailed stuff?

You mentioned that one. - Oh my goodness, go anywhere you wish with sleep. - So I'm a big fan of coffee and caffeine. And I've been, especially in the last few days, consuming a very large amount. And I'm cognizant of the fact that my body is affected by caffeine different than the anecdotal information that other people tell me.

I seem to be not at all affected by it. It's almost, it feels more like a ritual than it is a chemical boost to my performance. Like I can drink several cups of coffee right before bed and just knock out anyway. I'm not sure if it's a biological chemical or it has to do with just the fact that I'm consuming huge amounts of caffeine.

All that to say, what do you think is the relationship between coffee and sleep, caffeine and sleep? If there's an interesting distinction there. - There is a distinction. So I think the first thing to say, which is going to sound strange coming from me, is drink coffee. The health benefits associated with drinking coffee are really quite well-established now.

But I think that the counterpoint to that, well, firstly, the dose and the timing make the poison, and I'll perhaps come back to that in just a second. But for coffee, it's actually not the caffeine. So a lot of people have asked me about this rightful paradox between the fact that sleep provides all of these incredible health benefits and then coffee, which can have a deleterious impact on your sleep, has a whole collection of health benefits, many of them, Venn diagram overlapping with those that sleep provides.

How on earth can you reconcile those two? And the answer is that, well, the answer is very simple. It's called antioxidants. That it turns out that for most people in Western civilization, because of diet not being quite what it should be, the major source through which they obtain antioxidants is the coffee bean.

So the humble coffee bean has now been asked to carry the astronomical weight of serving up the large majority of people's antioxidant needs. And you can see this if, for example, you look at the health benefits of decaffeinated coffee. It has a whole constellation of really great health benefits too.

So it's not the caffeine, and that's why I liked what you said, this sort of separation of church and state between coffee and caffeine. It's not the caffeine, it's the coffee bean itself that provides those health benefits. But coming back to how it impacts sleep, it impacts sleep in probably at least three different ways.

The first is that for most people, caffeine can make it obviously a little harder to fall asleep. Caffeine can make it harder to stay asleep. But let's say that you are one of those individuals, and I think you are, and you can say, "Look, I can have three or four espressos with dinner, and I fall asleep just fine, and I stay asleep soundly across the night, so there's no problem." The downside there is that even if that is true, the amount of deep sleep that you get will not be as deep.

And so you will actually lose somewhere between 10 to 30% of your deep sleep if you drink caffeine in the evening. So to give you some context, to drop your deep sleep by let's say 20%, I'd probably have to age you by 15 years, or you could do it every night with a cup of coffee.

I think the fourth component that is perhaps less well understood about coffee is its timing, and that's why I was saying the timing and the dose make the poison. The dose, by the way, once you get past about three cups of coffee a day, the health benefits actually start to turn down in the opposite direction.

So there is a U-shaped function. It's sort of the Goldilocks syndrome, not too little, not too much, just the right amount. The second component is the timing, though. Caffeine has half-life of about five to six hours, meaning that after five to six hours, 50% of that, on average, for the average adult, is still in the system, which means that it has a quarter-life of 10 to 12 hours.

So in other words, if you have a coffee at noon, a quarter of that caffeine is still circulating in your brain at midnight. So having a cup of coffee at noon, one could argue, is the equivalent of tucking yourself into bed at midnight, and before you turn the light out, you swig a quarter of a cup of coffee.

But that doesn't still answer your question as to why are you so immune? So I'm someone who is actually, unfortunately, very sensitive to caffeine, and if I have, you know, even two cups of coffee in the morning, I don't sleep as well that night, and I find it miserable because I love the smell of coffee, I love the routine, I love the ritual, I think I would love to be invested in it.

It's just terrible for my sleep, so I switch to decaf. There is a difference from one individual to the next, and it's controlled by a set of liver enzymes called cytochrome P450 enzymes, and there is a particular gene that if you have a different sort of version of this gene, it's called CYP1A2, that gene will determine the speed of the clearance of caffeine from your system.

Some people will have a version of that gene that is very effective and efficient at clearing that caffeine, and so their half-life could be as short as two hours rather than five to six hours. Other people, hands up, Matt Walker, have a version of that gene that is not very effective at clearing out the caffeine, and therefore their half-life sort of sensitivity could be somewhere between eight to nine hours.

So we understand that there are individual differences, but overall, I guess the top line here is drink coffee and understand that it's not the caffeine, it's the coffee that's the benefit, and the dose makes the poison. - Is there some aspect to it that's it's like a muscle in terms of the, all the combination of letters and numbers that you just said, is there some aspect that if I can improve the quarter-life, the half-life, could decrease that number if I just practice?

Like drink a lot of coffee, is this like habit, alters how your body's able to get rid of the caffeine? - Not how the body is able to get rid of the caffeine, but it does alter how sensitive the body is to the caffeine. And it's not at the level of the enzyme degrading the caffeine, it's at the level of the receptors that caffeine will act upon.

Now, it turns out that those are called adenosine receptors, and maybe we can speak about what adenosine is and sleep pressure and all of that good stuff. But as you start to drink more and more coffee, the body tries to fight back, and it happens with many different drugs, by the way, and it's called tolerance.

And so one of the ways that your body becomes tolerant to a drug is that the receptors that the drug is binding to, these sort of welcome sites, these sort of picture myths, as it were, that receive the drug, those start to get taken away from the surface of the cell.

And it's what we call receptor internalization. So the cell starts to think, gee whiz, there's a lot of stimulation going on, this is too much. So I'm just going to, when normally I would coat my cell with, let's just say five of these receptors for argument's sake, things are going a little bit too ballistic right now.

I'm going to take away at least two of those receptors and downscale it to just having three of those. And now you need two cups of coffee to get the same effect that one cup of coffee got you before. And that's why then when you go cold turkey on coffee, all of a sudden the system has equilibrated itself to expecting X amount of stimulation.

And now all of that stimulation is gone. So it's now got too few receptors and you have a caffeine withdrawal syndrome. And that's why, for example, with drugs of abuse, things like heroin, when people go into abstinence, as they're sort of moving into their addiction, they will build up a progressive tolerance to that drug.

So they need to take more of it to get the same high. But then if they go cold turkey for some period of time, the system goes back to being more sensitive again. It starts to repopulate the surface of the cell with these receptors. But now when they reuse and they fall off the wagon, if they go back to the same dose that they were using before 10 weeks ago or three months ago, that dose can kill them.

They can have an overdose. Even though they were using the same amount at those two different times, the difference is that it's not the dose of the drug, it's the sensitivity of the system. And that's the same thing that we see with caffeine. In terms of training the muscle, as it were, is the system becomes less sensitive, can calibrate.

- Is there a time, the number of hours before bed, that's a safe bet to most people to recommend you shouldn't drink caffeine this many hours? Like, is there an average half-life that you should be aiming at? Or is this advice kind of impossible because there's so much variability?

- There is huge variability. And I think everyone themselves, to a degree, knows it. Although I'll put a caveat on that too, because it's a slightly dangerous point. So the recommendation for the average adult, and where is the average adult in society? There is no such thing. But for the average adult, it would be probably cutting yourself off maybe 10 hours before.

So assuming a normative bedtime in society, I would say try to stop drinking caffeine before 2 p.m. and just keep an eye out. And if you're struggling with sleep, dial down the caffeine and see if it makes a difference. - Can I ask you about sleep and learning? So how does sleep affect learning?

Sleep before learning, sleep after learning, which are both fascinating kind of dynamics of the mind's interaction with this extra-conscious state. - Yeah, sleep is profoundly and very intimately related to your memory systems and your informational systems. The first, as you just mentioned, is that sleep before learning will essentially prepare your brain almost like a dry sponge ready to sort of, you know, initially soak up new information.

In other words, you need sleep before learning to effectively imprint information into the brain, to lay down fresh memory traces. And without sleep, the memory circuits of the brain, and we know we've studied these memory circuits, will, you know, they essentially become waterlogged as it were for the sponge analogy, and you can't absorb the information as effectively.

So you need sleep before learning, but you also need sleep, unfortunately, after learning too, to then take those freshly minted memories and effectively hit the save button on them. But it's nowhere near as quick as a digital system. It takes hours because it's a physical biological change that happens at the level of brain cells.

But sleep after learning will cement and solidify that new memory into the neural architecture of the brain, therefore making it less likely to be forgotten. So, you know, I often think of sleep in that way as, it's almost sort of future-proofing information. - In what way? - Well, it means that it gives it a higher degree of assurance to be remembered in the future rather than go through the sort of degradation that we think of as forgetting.

So the brain has, in some ways by default, you know, there is forget, and actually I would love to, I was going to say sleep is relevant for memory in three different ways, but I'm going to amend that and say there's four different ways which is learning, maintaining, memorizing, abstraction, assimilation, association, then forgetting, which the last one sounds oxymoronic based on the former three, but I'll see if I can explain.

So sleep after learning then sort of, you know, sets that information like amber in, you know, in solidification. The third benefit, however, is that sleep, we've learned more recently is much more intelligent than we ever gave it credit for. Sleep doesn't simply just take individual memories and strengthen them.

Sleep will then intelligently integrate and cross-link and associate that information together. And it's almost like informational alchemy so that you wake up the next morning with a revised mind wide web of associations. And that's probably the reason that, you know, you've never been told to stay awake on a problem.

You know, and in every language that I've inquired about that phrase or something very similar seems to exist, which means to me that this creative associative benefit of sleep transcends cultural boundaries. It is a common experience across humanity. Now I should note that I think the French translation of that is much closer to, I think you sleep with a problem, whereas the British, you sleep on a problem.

The French, you sleep with a problem. I think it says so much about the romantic difference between the British and the French, but let's not go there. - That's brilliant. So such a subtle, but such a fundamental difference. Yeah. - Oh, goodness. Yeah, goodness me. - Sleep with the problem.

- Yes, exactly. - That's how I love the French. So, and we can just sort of double click on any one of these and go into detail, but the fourth I became really enchanted by about eight years ago in our research, which was this idea of forgetting. And I started to think that forgetting may be the price that we pay for remembering.

And in that sense, there is an enormous benefit to letting go. And you may be thinking that sounds ridiculous. I don't want to forget. In fact, my biggest problem is I keep forgetting things, but the brain has a, well, we believe, has a finite storage capacity. We can't prove it yet, but my suspicion is that that's probably true.

It doesn't have an infinite storage capacity. It has constraints. If that's the case, we can't simply go through life being constantly informational aggregators, unless we are programmed to say we've got a hard drive space of about 85 to 90 years and we're good and we can do that. Maybe that's true.

I don't think that's true. I think forgetting is an incredibly good and useful thing. So for example, it's not beneficial from an evolutionary perspective for me to remember where I parked my car three years ago. So it's important that I can remember today's parking spot, but I don't want to have the junk kind of DNA from a memory perspective of where I parked my car two years ago.

Now, I actually have, in some ways, a problem with forgetting. And again, I'm not trying to sort of be laudatory, but I tend not to forget too many things. And I don't think that that's a good thing. And there's a wonderful neurologist, Luria, who wrote a book called "The Mind of the Mnemonicist." And it was a brilliant book, both because it was written exquisitely, but he was studying these sort of memory savants who basically could remember everything that he gave them.

And he tried to find a chink in their armor. And the first half of the book is essentially about him seeing how far he can push them before they fail. And he never found that place. He could never find a place where they stopped remembering. And then in his brilliance, he turned the question on its head.

He said, "Not what is the benefit "of constantly remembering, "but instead what is the detriment to never forgetting?" And when you start to realize his descriptions of those individuals, it's probably a life that you would not want. - But it's as fascinating, both from a human perspective, but also AI perspective.

There's a big challenge in the machine learning community of how to build systems that are able to remember for prolonged periods of time, lifelong continuous learning. So where you build up information over time. So memory is one of the biggest open problems in AI and machine learning. But at the same time, the right way to formulate memory is actually forgetting because you have to be exceptionally selective at which kind of stuff you remember.

And that's where the step of assimilation, integration that you're referring to is really important. I mean, we forget most of the things. And the question is exactly the cost of forgetting at the very edge of stuff that could be important or could not be, how do we remember or not those things?

Like for example, I've, you know, doing a podcast, I've become cognizant of one feature of my forgetting that's been problematic, which is I forget names and titles of books and so on. So when I read, I remember ideas, I remember quotes, I remember statements and like that's the space in which I'm thinking.

But when you communicate to others, you have to say this person in this book said that. So it's the same thing with like Andrew Huberman is masterful at this. It's this important academia, remembering the authors of a paper and the title of the paper as part of remembering the idea.

And I've been feeling the cost of not being able to naturally remember those things. And so that's something I need to sort of work on. But that's an example. - Are you good with faces? - Yes, very good at faces. - But not good with names. So I'm exactly like you.

And there is, you know, an understanding of that in the brain too. We understand that there is partitioning of those in terms of the territory of the brain that takes care of faces and facts and places and they can be separate. So I will never forget a face, but, you know, and as I said, I usually forget very little, but for some reason names are a struggle.

I think in some ways because I'm probably just a slightly anxious person. So when you first meet someone, which is usually the time when a name is introduced, you know, you were saying you were sort of anxious maybe about sort of sitting down with me, but I find that a little bit, you know, activating.

And so it's not as though there's anything wrong with my memory. It's just the emotional state I'm in when I'm first meeting someone, you know, it's a little bit perturbing, but I will never forget that face. - I completely relate to that because I almost don't hear people's names when they tell me because I'm so anxious.

- Yeah. - But I think there's certain quirks of social interaction that show that you care about the person, that you remember that person, that they matter to you, that they had an impact on you. And one of the ways to show that is you remember their name. But that's a quirk to me because there's a lot of people I meet have a deep impact on me, but I can't communicate that unless I know their name, unless I know some of the details that we humans seem to use to communicate that we remember each other.

What I remember well is the feeling we shared, is the experience we shared. What I don't remember well is the detailed labels of those experiences. And I need to certainly work on that. - I don't know. I think it's, you know, just allowing yourself to be innate and who you are is also a beautiful thing too.

I'm not suggesting it's not important to try and better oneself, but I also sometimes worry about the misery that that puts us in. But like you, I will. I do struggle with it. But I know the first time when we met in the lobby, I know exactly what you look like.

I know that you were wearing headphones. I know the shape and the size of those headphones. You didn't have your black jacket on. I know exactly what the weave of your shirt looked like. I know what your shoes look like. And I knew exactly the height of your, the end of your pants from the top of your shoes.

And so those things I don't forget, you know, and I can remember when people, I met people, you know, two years ago and I'll say, oh yes, we met there. And I remember you had those fantastic, you know, boots on. I thought they were a bloody great pair of boots, you know, and they're like, how do you, I didn't even remember what I was wearing that day.

- It's fascinating. Yeah, I'm the exact the same way, but you can't until we have Neuralink or something like that, we can't communicate that you remember all those things. - I know, that's what I want. - So you have to be able to use tricks of human communication for that.

But so that, I mean, that's the, it's ultimately is a trick of like, which to remember, which to forget. - Right. - And the forgetting is so, it's so fascinating you say this. I mean, it seems to be deeply connected to that assimilation process. So forgetting, you try to fit all the new stuff into this big web of the old stuff and the things that don't fit, you throw out.

- I think the assimilation, the way I've been thinking about it with sleep and it's particularly sort of dream sleep that we think can help with this assimilation is that during wake, we have one version of associative processing. And what I mean by that is we see the most obvious connections.

So I think of wakefulness as a Google search gone right. Whereas I see dream sleep as doing something very different. I think dream sleep is a little bit like group therapy for memories, that everyone gets a name badge and sleep gathers in all of the individual pieces of the day.

And it sort of starts to get you to, forces you in fact, to speak to the people, not at the front of the room that you think you've got the most obvious connection with, but to speak with the people all the way at the back of the room, that at first you think I've got no obvious connection with them at all.

But once you get chatting with them, you learn that you do have a very distant non-obvious connection, but it's still a connection on the same. And it's almost as though you're doing a Google search where I input Lex Friedman and it doesn't take me to the first page of your home site.

- Page 20. - It takes me to page 20, which is about some like field hockey game in Utah. - Yeah, exactly. - It turns out that there actually is a link if I look at it, it's a distant non-obvious one. And to me, I find that exciting because when you fuse things together that shouldn't normally go together, but when they do, they cause marked advances in evolutionary fitness.

It sounds like the biological basis of creativity. And that's exactly what I think DreamSleep and the algorithm of DreamSleep is designed to do. You know, it's not a Boolean like system where you have, you know, the sort of assumptions of true and false, you know, maybe it's more fuzzy logic system.

And I think REM sleep is a perfect environment within which we do, you know, it's almost like memory pinball. You know, you get the information that you've learned during the day, and then you pull the lever back and you shoot it up into the attic of your brain. You know, this cortex filled with all of your past historical knowledge, and you start to bounce it around and see where one of those things lights up and you build a new connection there and you build another one there too.

You're developing schemas. And so in that way, I think you could argue, you know, we dream, therefore we are. (laughing) - Yeah, so in terms of this line between learning and thinking through a new thing that seems to be deeply connected, there's this legendary engineer named Jim Keller who keeps yelling at me about this.

He says it's very effective. He likes to, for difficult problems before bed, think about that difficult problem. We're not talking about like drama at work or all that kind of stuff. No, like a scientific, for him, engineering problem. He likes to intensely think about it and to prime his mind before sleep and then go to sleep.

And then he finds that the next day, he's able to think much clearer and there's new ideas that come, but also just, I guess it's more well-integrated. And sometimes during the process of, like he's able to like wake up and like see new insights. - That's right. - If he's deeply sort of aggressively thinking through a problem.

- So there's many scientific, you know, demonstrations of this, you know, the Mendeleev with the periodic table of elements, you know, he was trying for months to understand. I mean, talk about an ecumenical problem of epic proportions. Here's your question today. You have to understand how all of the known elements in the universe fit together in a logical way.

Good luck, take care. It was non-trivial at the time. And he would try and try, he was so obsessed with it. He created playing cards with all of the different elements on. And then he would go on these long train journeys around Europe and he would just sort of deal these cards in front of them and he would shuffle them, shuffling and shuffling.

And he would just try to see if he could find what the answer was. And then, so the story goes, you know, he fell asleep and he had a dream. And in that dream, you know, all of these elements started to dance and play around and they snapped into a logical grid, you know, atomic weights, et cetera, et cetera.

And it wasn't his waking brain that solved the problem. It was his sleeping brain that solved the impenetrable problem that his waking brain could not. And there's been count, you know, even in the arts and in music, some wonderful dreams, you know, Frankenstein, Mary Shelley's epic Gothic novel came to her in a dream at Lord Byron's home.

And then we've got, you know, Paul McCartney. Yesterday, the song came to him in a dream. He was filming, gosh, what was the movie? I don't recall it. I should be shot because I'm from Liverpool myself. And, but he was on Wimpole Street in London and filming. And they, he came up with that song, the melody in his sleep, not to be outdone by the Beatles.

And by the way, "Let It Be" also came from a dream that McCartney had. People usually give it, you know, religious overtones. You know, mother Mary comes to me speaking words of wisdom, let it be. If you've ever asked who mother Mary is, it's not the, you know, the biblical content.

It's his mother. It's Mary McCartney. And she came to him in a dream and gifted him the song. But the best story I've heard is not to be outdone by the Beatles, the Stones, Keith Richards, who I think once was suggested, who was it? It was a comedian who was saying that in an interview with Rolling Stone, Keith Richards suggested or inferred that young kids should not do drugs.

And they said, well, look, young kids can't do drugs because you've done all of them. - All of them, yeah. - And I always thought that, but Keith Richards described, he would always go to bed with his guitar and a tape recorder. And then probably he would have a whole set of other things in the bed with him.

And who knows how many other people, but anyway. And then he said in his autobiography, and I'm paraphrasing here, but one morning I woke up and I realized that the tape had recorded all the way to the end. So I rewound the tape and I hit play. And there in some kind of ghostly form were the opening chords to "Satisfaction," the most famous successful Rolling Stone song of all time.

Followed by then 43 minutes of snoring. - That's awesome. - But that riff came to him, one of the most famous riffs in all of rock and roll came to him by way of a dream inspired insight. So I think there is too many of those anecdotes and we've now got the science, I don't rely on anecdotes as science.

We've now done the studies in the laboratory and we can reliably demonstrate that sleep inspires creativity, inspires problem solving capacity. - Well, the interesting thing is, is it possible to some of the ideas that you talk about to turn them into a protocol that could be practiced rigorously? So what Jim Keller espouses is saying, not just the fact that sleep helps you increase the creativity, but turn it into a process.

Like literally, like don't do it accidentally. You know, like an athlete does certain things to optimize their performance. They have a training routine, they have a regimen of like cycling and sprints and long distance stuff. In the same way, thinking about your job as an idea generator in the engineering space is like, this is good for my performance.

So like for an hour before bed, think through a problem like every night and then use sleep to work through that problem. I mean, he's the first person that I heard like of the people I really respect that do like what I do, which is like programming engineering type work, like using sleep, not accidentally, but with a purpose, like using sleep.

You know, that's just basically the difference between, as you said, a passive approach to it versus an active deterministic or hope for a deterministic approach to it. In other words, that you are actually trying to harness the power of sleep in a deliberate way rather than an unthoughtful way.

I still think that, you know, mother nature through it, you know, 3.6 million years of evolution has probably got it mostly figured out in terms of what information should be uploaded at night and worked through. I think her algorithm is probably pretty good at this stage. It's not to suggest though that, you know, we can't try to tweak it and nudge it.

You know, it's a very light hand on the tiller is what he's doing. I don't think there's anything wrong with that. - You know, just like, for example, for me, fasting has improved my ability to focus deeply and productivity significantly. And in that same way, you know, it's possible that playing with these ideas of thinking before bed or some hours before bed, or some playing with different protocols will have a significant leap over what mother nature naturally does.

So if you let your body do what it naturally does, you may not achieve the same level of performance 'cause mother nature has not designed us to think deeply about chip design or programming artificial intelligence systems. - Well, she's gifted us the architecture and the capacity to do that.

What we do with that is, you know, is what life's experience dictates. She gives us the blueprint to do many, you know. - Well, if I were to sort of introspect and self-analyze what mother nature wants me to do, I think given my current lifestyle that I have food in the fridge and a bed to sleep on, I think what mother nature wants me to do is to be lazy.

(both laughing) And so I think I'm actually resisting mother nature because so many of my needs are satisfied. And so I have to resist some of the natural forces of the body and the mind when I do some of the things I do. So there's that dance. You know, like I've been thinking about doing a startup and that's obviously going against everything that my body and mind are telling me to do because it's going to be basically suffering.

But the only reason I want-- - As you know it, we'll be over. (both laughing) - Yes. But nevertheless, there's some kind of inner drive that wants me to do it. And then you start to ask the question, well, how do you optimize the things you can optimize like sleep, like diet, like the people that you surround yourself with in order to maximize happiness and performance and all those kinds of things without also over-optimizing.

And that's such an interesting idea from an engineer. So as you may know, you don't often get those kinds of ideas from engineers. Engineers usually just don't read books about sleeping. They're usually like, they're not the healthiest of people. I think that's changing over time, especially with Silicon Valley, especially with the tech sector, people are starting to understand what's a healthy lifestyle.

But usually they're kind of on the insane side, especially programmers. But it's nice to hear somebody like that use sleep and use some of the things you talk about, strategically, on purpose. - You know, to that idea of not just trying to use what mother nature gave, but seeing if you can do something more or different.

In a conservative mindset, I would then pose the question at what cost? Because when you do something perhaps that deviates from the typical pre-programmed, you know, mother nature's program, I suspect it usually comes at the cost of something else. So maybe he is able to direct and focus his sleeping cognition on those particular topics that will gain him better problematic resolution the next day when he wakes up.

The question is though, at what cost of the other things that didn't make it onto the menu of the finger buffet of sleep that night? And is it that you don't process the emotional difficulties or events, and therefore you are less emotionally resolved the next day, but you are more problem resolved the following day?

And so I always try to think, and I truly don't want to sound puritanical either about sleep. And I think I've come off that way many a time, especially when I started out in the public. The tone of the book in some ways, you know, I look back and think, could I have been a little softer?

And the reason was I was that way back in, but when I started writing the book, which was probably something like 2014 or '15, sleep was the neglected step-sister in the health conversation of the day. And I was just so sad to see the amount of suffering and disease and sickness that was caused by insufficient sleep.

And for years before I'd been doing public speaking and I'd tell people about the great things that happen when you get sleep, people would say, that's fascinating. And then they would go back and keep doing the same thing about not sleeping enough. And then I realized you can't really speak about the good things that happen.

It's like the news, what bleeds leads. And if you speak about the alarmingly bad things that happen, people tend to have a behavioral change. And so the book as a consequence, I think probably came out a little bit on the strong side of trying to convince people. - You were trying to help a lot of people and that's a powerful way to help a lot of people.

- I was genuinely trying to help people, but certainly for some people for whom sleep does not come easy, then it was probably a tricky book to read too. And I think I feel more sensitive to those people now and empathetically connected to them. So I think the, again, the point was simply that I don't mean to sound too puritanical in all of this.

And the same way with caffeine and coffee, I am just a scientist and I am not here to tell anyone how to live their life. That is not my job at all. And life is to be lived to a degree. And life is to be lived if you want to do a startup.

All I want to do is empower people with the understanding of the science of sleep. And then you can make an informed choice as to how you want to live your life. And I offer no judgment on how anyone wishes to live their life. I just want to try and see if the information that I have about sleep would alternatively change how you would think about your life decisions.

And if it doesn't, no problem. And if it does, I hope it's been of use. Well, maybe this is me trying to justify my lifestyle to you. But Dr. Seuss said, "You know you're in love "when you can't fall asleep because reality "is finally better than your dreams." - I love that quote too.

- Okay. My sleeping schedule is complicated. And it has to do primarily with the fact that I love basically everything that I do. And that love takes a form that may not appear to be love from the external observer perspective. 'Cause it often includes struggle. It often includes something that looks like stress, even though it's not stress.

It's like this excitement, it's this turmoil and chaos of passion, of struggling with a problem, of being sad and down to the point even depressed of how difficult the problem is, the disappointment that the last few weeks and months have been a failure and self-doubt, all that mix. But I love it.

And a part of that is sometimes staying up all night working on a thing I'm really passionate about. And that means sleep schedules that are just like, sometimes sleeping during the day, sometimes very often sleeping very little, but taking naps that are like an hour or two hours or so on, that kind of weird chaos.

Now, I'll also try to give myself backup. I was trying to like research yesterday, is anybody else productive while like this? And there's of course a lot of anecdotal evidence and some of it could be just narratives that people have told to the public when in reality they sleep way more, but there's a bunch of people that are famous for not sleeping much.

So on the topic of naps, I read this a long time ago and I checked this, Churchill was big on big naps and is actually just reading more about Winston Churchill's sleep schedule is very much like mine. So I basically wanna give myself the opportunity to at night, to stay up all night if I want to.

And a good nap is a big part of that in the late evening. Like I'll often, that just destroys social life completely, but I'll often take a nap in the late afternoon or the evening and that sets me if I want to stay up all night. And things like that, like I read that Nikola Tesla slept only two hours a night, Edison the same three hours, but he actually did the polyphasic sleep like where it's just a bunch of naps.

What can you say about this madness of love and passion, of loving everything you do and the chaos of sleep that might result in? - I love the Seuss quote. And I've had that experience too, like you, I adore what I do. If someone gave you enough money to live the rest of your life, got a roof above my head, rice and beans on the table, and they said, "You don't have to work anymore," I would do nothing different.

I would do exactly, you know, this sounds a little crass and I hope it doesn't sound this way, but being a scientist is not what I do, it's who I am. It's not what I do, it's who I am. And when that's the case, sleep, working out, showering and eating are the things that I do in between my love affair with sleep.

I fell for sleep like a blind roofer. And it was a love affair that started 20 years ago and I remain utterly besotted today. It's the most beguiling thing in the world to me. And I could easily, and I have, you know, it's kept me up at night. When my mind is fizzing with experimental ideas or I think I've got a new hypothesis or theory, I will struggle with sleep, I really will.

It doesn't come easy to me because my mind is just so on fire with those ideas. So I understand the struggle, but I couldn't advocate from a scientific perspective the schedule because the science just doesn't, I would feel as though I'm doing you a disservice to say it's okay, that won't come with some blast radius, some health consequences.

You can add Margaret Thatcher and Ronald Reagan to that list too. Both of them were very, you know, proud chess beaters of how little sleep that they get. Thatcher said four hours, Reagan, something similar, you know, and I, knowing the links that we now know between sleep and Alzheimer's disease, I've often wondered whether it was coincidental then that both of them died of the terrible disease of Alzheimer's meaning, you know, maybe it doesn't get you by way of, you know, being popped out of the gene pool in a car accident 'cause you had a microsleep at the wheel at age 32, or it doesn't get you at 42 with, you know, heart attack or even 52 with cancer or a stroke, maybe it gets you in your 70s.

I think the elastic band of sleep deprivation can stretch only so far before it snaps and it ultimately seems to snap. You know, Nikola Tesla, I think he, Nikola Tesla, he, I think died of a coronary thrombosis, I believe, and there was a wonderful study done out of Harvard where they took a group of people who had no signs of cardiovascular disease.

And what they found is that when they track them for years afterwards, they were completely healthy to begin with, those people who were getting less than six hours of sleep ended up having a 300% increased risk of developing calcification of the coronary artery, which is the major sort of corridor of life for your heart when someone says, you know, he died of a massive coronary, it's because of a blockade of the coronary artery, you know, and Tesla, you know, passed away from a coronary thrombosis.

We also know that insufficient sleep is linked to numerous mental health issues. We know that Churchill had a wicked battle with depression. Gosh, my goodness, he used to call it black dog that would come and visit him. And I think many of his paintings, he was exquisite painter, but some of them would depict his darkness with depression as well.

You know, Edison is interesting. People have argued that he would short sleep and he didn't put much value in sleep, whether or not that's true, we don't know, but he was a habitual napper, you're right, during the day, I've got some great pictures of him on his inventor's bench taking a nap.

And in fact, I believe he set up nap cots around his house so he could nap. But what we also know is that he, again, coming out of Harvard just a couple of months ago, demonstrated very clearly that polyphasic sleep is associated with worse physical outcomes, worse cognitive outcomes, and especially worse mood outcomes.

So from that sense, you know, sleeping like a baby is not perfect for adults. - There's a fascinating dance here of the mean and the extreme, like the average and the high performers. So I, this gets to like the meaning of life kind of discussion, but let's go there.

So, well, and also happiness. So when studying sleep and when studying anything like diet and exercise, I think you have to really get a lot more data about individuals to make a conclusive statement. When people talk about like, is meat, red meat good for you or bad for you, right?

It's just so often correlated with other life decisions when you choose to eat meat or not. My sense is that whatever life decisions you make, if they reduce stress and lead to happiness, that's also going to be a big boost that needs to be integrated into the plots in the science.

Right? So I'll give you an example of somebody who is unarguably seen as unhealthy. My friend, Mr. David Goggins. So he's clearly, obviously, almost on purpose destroying his body. And to say that he's doing the wrong thing or the unhealthy thing feels wrong. But I'm not sure exactly in which way he feels wrong.

One of the things I'm bothered by, and again, I apologize for the therapy sessions, a framework of this, but I'm bothered by the fact that a lot of people tell me or David that they're doing things wrong. A lot of people in my life, when they see me not sleep, they'll tell me to sleep more.

Now they're correct. But one fundamental aspect that I'd like to complain about is not enough people, almost nobody, especially people that care for me, will come to me and say, "You have a dream, work harder." It's like the healthy thing should be a component of a life well-lived. - Right.

- But not everything. And I don't know what to do with that because you certainly don't want to espouse it. And just like you said, when you were working in your book, there is a belief, sleep was a secondary citizen in the full spectrum of what's a healthy life.

But at the same time, I'm bothered by in Silicon Valley and all these kinds of work environments that I get to work with with engineers is there's, to me, too much focus on work-life balance. What that usually starts meaning is like, yeah, yeah, of course, it's good to have a social life, it's good to have a family, it's good to eat well and sleep well, but we should also discover our passion.

We should also give ourself a chance to work our ass off towards a dream and make mistakes and take big risks that in the short term seem to sacrifice health. - And I think, to come back to how you started about David Goggins, who I've never met, but who I admire incredibly and have an immense reverence for the man, you said two things.

Is it wrong to do those things to yourself? And is it unhealthy to do those things to yourself? - I disagree with the former and I agree with the latter. So from a health biological medicine perspective, sleeping in the way that you've described or that other people may be sleeping in terms of insufficient amounts, now, to your point, too, about inter-individual differences, usually when I see a bar graph and a mean, I usually say, show me your variance.

I want to see your variance. In other words, show me the distribution of that effect. How many people were below the mean? How many, is it all tightly clustered around this one thing? So it's a very robust effect. Or was this huge fan of effect where for some people, there was no effect at all and other people, there was a whopping effect and everything in between.

So I don't discount inter-individual variability. But, and I will come back to those two points about is it wrong and is it unhealthy in just a second. When it comes to sleep, we have found huge amounts of inter-individual differences in your response to a lack of sleep. But one of the fascinating things, so let's say that I take you and we're going to measure your attention, your emotion, your mood, your blood pressure, your blood sugar glucose regulation, your autonomic nervous system, and your different gene expression.

Let's say I'm just going to measure a whole kaleidoscope of different outcomes, brain and body. And I find that on our measure of cognition, on your attentional ability to focus, you are very resilient. You just don't show any impairments at all, even after being awake for 36 hours straight.

Does that mean that you are resilient in all of those other domains as well? The answer is no, you're not. So you can be resilient in one, but very vulnerable in another. And we've not found anyone who isn't at least vulnerable in one of those domains. Meaning that it's somewhat safe to say that not getting sufficient sleep will lead to some kind of impairment in anyone given individual.

It may not be the same impairment, but it's likely to be an impairment. But to come back to the question, I think it's wrong to tell anyone that it's wrong to do what they're doing, even if they are compromising their sleep, even if they're compromising their mental health. As long as they're not hurting anyone else, then I think the answer is that's that person's choice.

- Yeah, but that's that person's life. - I'd like to push back further. So see the way you kind of said it, yes, you're absolutely right. But I would like to say a stronger statement, which is you should let go of that judgment of somebody is wrong and allow yourself to be inspired by the great heights they have reached.

So take yourself out of the seat of being a judger of what is healthy or not, and appreciate the greatness of a particular human. You watch the Olympics, the kind of things that some athletes do to reach the very heights. The Olympics are taking years off their life. They suffer depression after the Olympics often.

- Their physiology is disastrous. - Everything, their personal life, their psychology, their physiology, everything. It's a giant mess. So the question is about life. Healthy now means longevity, quality of life over a prolonged period of time, optimal performance over a prolonged period of time. But to me, beauty is reaching great heights.

And there's a dance there that sometimes reaching great heights requires sacrifice of health and not like a calculation where you sat down on a sheet of paper and say, I'm going to take seven years off my life for an Olympic gold medal. No, it requires more chaotic journey that doesn't do that kind of calculus.

And I just want to kind of speak to the, in the culture that struggles of what is healthy and not, we want to be able to speak to what is healthy and at the same time be inspired by the great heights that humans reach no matter how healthy or unhealthy they live.

- Yeah, I agree with that. I think if that's a flag you're hoisting, I will definitely salute it because it really depends, what are you trying to optimize for in your life? And if you are, I think the only danger potentially with that mindset is that if you look at many of the studies of old age and end of life, most people say, I never look back on my life and wish I worked harder.

I wish instead I'd spent more time with family, friends and engaged in that aspect. Now I'm not saying though, coming back to your point, that that is the standard rubric for everyone. I don't believe it is too. And there are many things that you and I are both benefiting from today, even in the field of medicine, where people have sacrificed their own longevity for the quest of solving a particular medical problem and they died quicker because of their commitment, because they wished to try and solve that problem in their pursuit of greatness scientifically.

And I now benefit. Am I grateful that they did that? Incredibly grateful. A simpler demonstration is this, if tonight at 4 a.m. in the morning, I have a ruptured appendix, I have an appendicitis, I am incredibly grateful that there is an emergency team that will take me to the hospital at 4 a.m.

in the morning. They are awake, they're not sleeping and they save my life. And that's part of what their life's mission and quest is. And they saved another's life by, in some ways, shaving a little of their own off. So I don't take, I have no umbrage with that mentality at all.

I think you just have to be very clear about what you're optimizing for. And my worry is that most people fall into the rat race and they never actually ask the question, why am I doing this? - If you're just working nine to five, and you allow that nine to five to stretch into much longer, but it's nevertheless a job that's kind of like, wears you down, that's one thing.

Another thing is when it is a lot like, it's a dream. - Your life mission is to accomplish. And for that, I think as long as you know what it is that you could be doing to yourself and you are comfortable and A-okay with that, I have no problem with that at all.

Again, as I said, as a scientist, I cannot, should not, and will not tell anyone what they should do with their life. All I want you to be able to do is say, okay, now I understand more about the, previously these were the known unknowns and these were the unknown unknowns.

And now I am slightly more cognizant, I have more knowns than I had before regarding my sleep and my health, knowing that information, do I still choose to make this decision? And if that's what I offered, then I think I've done my job. That's all I want to offer is just added information into the decision algorithm and what you end up choosing as an output of that algorithm has nothing to do with me.

It's not my business and I will never judge anyone for it. And as I said, I'm immensely grateful for people who have sacrificed much in their lives to give me what I have. - So you're saying as long as the sacrifice, sort of grounded in knowledge of what the sacrifice is, that sleep is important, all those kinds of things.

- And that you're comfortable with it, that it is your conscious choice rather than feeling as though you're trapped or that you are just, you haven't thought about it. And you start that job at age 32 and then you wake up the next morning and you're 65 and you think, where did my life go?

What was I doing? That to me, I would feel, I would want to hug you and I would say, I'm just, and I'm not sounding, I don't mean to sound belittling here at all. I would just not wish that for you. I would wish that you could have thought about what it was that you're doing and not have that regret.

- Yeah, so I guess I'm, this is for you, the listener. I'm coming out of the closet here a little bit. The fact that I enjoy the madness I live in. So please do not criticize me, embrace me. I understand the sacrifices I'm making. I enjoy sleeping on the floor when I'm passionately programming all night and just pass out on the carpet.

I love this life, okay? So it's, but it's definitely something I think about that there's a balance to strike where-- - I just want you to have as much of it though. - Of life. See, quality of life is important. - I should have said, I want you to have as much high quality life.

And if high quality of life means I spend five decades on this planet, but yet in that time, I am thrilled every day. I'm turned on every day by what I do. And I reveled in this thing called my life's work. I think that that is a 50 year journey of absolute delight and fulfillment that you should take.

- I think about my death all the time. I meditate on death. I'm okay to die today. So to me, longevity is not a significant goal. I'm so happy to be alive. I don't even think it would suck to die today. I'm as afraid of it today as I will be in 50 years.

I don't wanna die as much today as I will in 50 years. There's of course all these experiences I would like to have, but everything's already amazing. It's like that Lego movie. So I don't know. So to me, I just wanna keep doing this. And there's of course things that could affect, like you mentioned dementia and these deterioration of the mind or the body that can significantly affect the quality of life.

And so you want to- - As long as you're aware of that. And that's the price you pay for the entry of into this magical kingdom that you are experiencing, which is a lovely thing. I feel privileged too. I can't believe the life that I live. It's incredible. And just like you, I think about mortality a great deal.

I think a lot about death, but I don't worry about death. I probably, with the exception of the potential pain that comes before it, that some people, many people can suffer, that maybe concerns me. But I actually think about mortality as a tool, as I use it as a lens through which I can then retrospect.

And by placing myself at the point of future mortality, I can then use it as a retrospective lens to focus and ask the following question, is there anything I feel I would regret and therefore change in the life that I currently have now? That's the way I meditate and use mortality as a question, is to try and course correct and focus my life.

I worry not about dying, but I like to think about death as a way to prioritize my life, if that makes sense. I don't know if that makes sense. - No, it makes total sense to decide how do you want to live today so that in the future, you do not regret the way you've lived today.

- Right, and to place yourself in the future at your point of mortality is one way to, I think, as an exercise to retrospectively look back and not lose out on informed choices that you could otherwise lose out on if you weren't thinking about mortality. - Yeah, it clarifies your thinking.

Is there, so I mentioned I sleep on the floor, take naps and power naps, and it's just kind of madness. Is there weirdnesses to your own sleep schedule as a scientist that does incredible work, has a lot of things going on, has to lead research, has to write research, has to be a science communicator, also have a social life, all those kinds of things.

Is there certain patterns to your own sleep that you regret or you participate in that you find you enjoy? Is there some personal stuff, quirks, or things you're proud of that you do in terms of your sleep schedule? - The funny thing about being a sleep researcher is that it doesn't make you immune to the ravages of a difficult night of sleep, and I have battled my own periods of insomnia in my life too.

And I think I've been fortunate in ways because I know how sleep works and I know how to combat insomnia. I know how to get it under control because insomnia in many ways is a condition where all of a sudden your sleep controls you rather than you control your sleep.

- Wow, yeah, that's a beautiful way to put it, yeah. - And I know when I'm starting to lose control and it's starting to take control, I understand how to regain, but it doesn't happen overnight. It takes a long time. - So you've struggled with insomnia in your life?

- I have, not all of my life. I would say I've probably had three or four really severe bouts, and all of them usually triggered by emotional circumstances, by stress. - Stress that's connected to actual events in life or stress that's unexplainable? - Well, externally triggered, yeah. It's sort of what we would call reactive stress.

And so that's sort of point number one about the idiosyncrasies. The point number two is that when you are having a difficult night of sleep, as a sleep researcher, you basically have become the Woody Allen neurotic of the sleep world. Because at that moment, I'm trying to fall asleep and I'm not, and I'm starting to think, okay, my dorsolateral prefrontal cortex is not shutting down, my noradrenaline is not ramping down, my sympathetic nervous system is not giving way to my parasympathetic.

At that point, you are dead in the water for the next two hours and nothing is bringing you back. So there is some irony in that too. I would say for myself though, if there is something I'm not proud of, it has been at times railing against my chronotype.

So your chronotype is essentially, are you a morning type, evening type, or somewhere in between? - Yeah. - And there were times because society is desperately biased towards the morning types. This notion of the early bird catches the worm. Maybe that's true, but I'll also tell you that the second mouse gets the cheese.

- Yeah. - So I think one of the issues-- - That's a good line. - Around, firstly, people don't really understand chronotype because I'll have some people when I'm sort of out in the public, they'll say, look, I struggle with terrible insomnia and I'll ask them, is it problems falling asleep or staying asleep?

And they'll say falling asleep. And then I'll say, look, if you are on a desert island with nothing to wake up for, no responsibilities, what time would you normally go to bed and what time would you wake up? And they would say, I'd probably like to go to bed about midnight and wake up maybe eight in the morning.

And then I'd say, so what time do you now go to bed? And they'd say, well, I've got to be up for work early, so I get into bed at 10. I'd say, well, you don't have insomnia, you have a mismatch between your biological chronotype and your current sleep schedule.

And when you align those two, and I was fighting that for some time too, I'm probably mostly right in the middle. I am desperately vanilla, unfortunately, in many aspects of life, but this included, I'm neither a strong morning type nor a strong evening type. So ideally, I'd probably like to go to bed around 11, 10.30, 11, probably somewhere between 10.30 and 11 and wake up, I naturally wake up usually most days before my alarm at 7.04.

And it's 7.04 because why not be idiosyncratic in terms of setting an alarm? - I love it. - And so I-- - That's kind of awesome, I've never heard about that. That's amazing, I'm gonna start doing that now, setting alarms like a little bit off the-- (laughing) - Yeah, I'm never quite sure why we all-- - It's a celebration of uniqueness.

- Yeah, and I am quite the odd snowflake in that sense too. So I would usually then try to force myself because I had that same mentality that if I wasn't up at 6.30 and in the gym by seven, that there was something wrong with me. And I quickly abandoned that.

But if I look back, if there was a shameful act that I have around my sleep, I think it would be that for some years until I really started to get more detailed into sleep. And now I have no shame in telling people that I will probably usually wake up around 6.45 naturally, sometimes seven, when people are looking at me thinking, you're a sloth, you're lazy.

And I don't finish my daily workout until, I'm not working until probably nine o'clock in the morning. They're thinking, what are you doing? Now I will work late into the day. If I could, I would work 16 hours. It's my passion just like yours. So I don't feel shame around that, but I have changed my mentality around that.

- It's complicated because I'm probably happiest going to bed, if I'm being honest, like at 5 a.m. - That's fine, you're just an extreme evening type. - But the problem is, it's not that I'm ashamed for it. I actually kind of enjoy it 'cause I get to sleep through all the nonsense of the morning.

- Isn't that a beautiful thing? - Like people are busy with their emails and I just am happy as a cow. And I wake up, after all the drama has been resolved. - Yeah, and cows are happy and the drama has been resolved. - Exactly, but in society you do, especially, I mean, this is what I think about is, when you work on a larger team, especially with companies, you are, everybody's awake at the same time.

So that's definitely been a struggle to try to figure out, just like you said, how to balance that, how to fit into society and yet be optimal for your chronotype. - Yeah, you have to sleep in synchrony with it and harmony. Because normally what we know is that if you fight biology, you'll normally lose.

And the way you know you've lost is through disease and sickness. - You said you suffered through several bouts of insomnia. Is there, aside from embracing your chronotype, is there advice you can give how to overcome insomnia from your own experience? - Right now, the best method that we have is something called cognitive behavioral therapy for insomnia or CBTI for short.

And you work with, for people who don't know what it is, you work with a therapist for maybe six weeks and you can do it online, by the way, I recommend probably jumping online, it's just the easiest. And it will change your beliefs, your habits, your behaviors and your general stress around this thing called sleep.

And it is just as effective as sleeping pills in the short term. But what's great is that unlike sleeping pills, when you stop working with your therapist, those benefits last for years later. Whereas when you stop your sleeping pills, you typically have what's called rebound insomnia where your sleep not only goes back to being as bad as it was before, it's usually even worse.

For me, I think I found a number of things effective. The first is that I had to really address what was stressful and try to come up with some degree of meaningful rationality around it. Because I think one of the things that happens, there's something very, talking about conscious states to come all the way back to, gosh, I don't know, I feel like we've only been chatting for like 20 minutes, but you're gonna tell me it's been a while.

- Yeah, it's been a while. - Okay, I'm desperately, I feel terribly sorry. But let's come back to conscious states which is where we started. There is something very strange about the night that thoughts and anxieties are not the same as they are in the waking day. They are worse, they are bigger.

And I at least find that I am far more likely to catastrophize and ruminate at night about things that when I wake up the next day in the broad light of day, I think it's no one near that bad man. What were you doing? It's not that bad at all.

So to gain firstly, some rational understanding of my emotional state that's causing that insomnia was very helpful. The second thing was to keep regularity, just going to bed at the same time waking up. And here's an unconventional piece of sleep advice. After a bad night of sleep, do nothing.

Don't wake up any later, don't go to bed any earlier, don't nap during the day, and don't drink any more coffee than you would otherwise. Because if you end up sleeping later into the morning, you're then not going to be tired at your normal time at night. So then you're gonna get into bed thinking, well, I had a terrible night of sleep last night.

And yes, I slept in this morning to try and compensate, but I'm still gonna get to bed at my normal time. But now you get into bed and you haven't been awake for as long as you normally would. So you're not as sleepy as you normally would be. And so now you sit there lying in bed and it's another bad night.

And the same thing is, if you go to bed any earlier, so don't wake up any later, wake up at the same time, don't go to bed any earlier, because then you're just probably, your chronotype, your biological rhythm doesn't want you to be asleep. And you think, well, terrible night, I'm gonna get into bed at 9 p.m.

rather than my standard 10. You're just gonna be lying in bed awake for that hour. Naps will take our double-edged sword. They can have wonderful benefits. And we've done lots of studies on naps for both the brain and the body, but they are a double-edged sword in the sense that napping will just take the edge off your sleepiness.

It's a little bit like a valve on a pressure cooker. When you nap during the day, you can take some of that healthy sleepiness that you've been building up during the day. And for some people, not all people, but for some people, that can then make it harder for them to fall asleep at night and then stay asleep soundly across the night.

So the advice would be, if you're struggling with sleep at night, don't nap during the day. But if you are not struggling with sleep and you can nap regularly, naps are just fine. And we can play around with optimal durations depending on what you want. Just try not to nap too late into the day because napping late into the day is like snacking before your main meal.

It just takes the edge off your sleep hunger, as it were. But that would be, so that's my unconventional second piece of advice regarding insomnia. The third is meditation. I found meditation to be incredibly powerful. I started reading about meditation as I was researching that aspect of the book many years ago.

And as a hard-nosed scientist, I thought this sounds very woo-woo. This is sort of, we all hold hands and sing "Kumbaya" and everything's going to be fine with sleep. I read the data and it was compelling. I couldn't ignore it. And I started meditating. And that was six years ago and I haven't stopped.

And I find meditation before bed incredibly powerful. The meditation app companies were perplexed at this at first. They want people to meditate during the day. But when they looked at their usage statistics, they found that they would have people in the morning meditating. And then there's a huge number of people using the meditation app in the evening.

What they were doing was self-medicating their insomnia. And they finally, rather than railing against it, they started to see it as a cash cow, rightly so. So I found meditation to be helpful. Having a wind down routine is the other thing that's critical for me. I can't just go from, because when my mind is switched on, and I think you may be like this too, if I get into bed, that rolodex of thoughts and information and excitement and anxiety and worry is just whirling away.

And it's not gonna be a good night for me. So I have to find a wind down routine. And that makes sense when you realize what sleep is like. Sleep is not like a light switch. Sleep is much more like trying to land a plane. It takes time to descend down onto the terra firma that we call sound sleep at night.

And we have this for kids. I don't have children, but a lot of parents will say, we have to have the bedroom, sorry, the bedtime routine. You bathe the kid, you put them in bed, you read them a story. You have to go through this routine, this wind down routine for them.

And then they fall asleep wonderfully. Why do we abandon that as adults? We need that same wind down routine. So that's been the other thing that's been very helpful to me. So don't do anything different. If you have a bad night of sleep, keep doing the same thing. Manage your anxiety, understand it, rationalize it.

Then meditation. And then finally having some kind of disengagement wind down routine. Those are the four things that have been very helpful to me. - That's brilliant. So the regularities really do a lot of work against insomnia. Is it possible to have a healthy sleep life without the regularities?

- I say that because I'm all over the place and I've gotten good at being all over the place. So I'll often, like what happens, I'll go stretches of time. There'll be some times a month where my days are like, this is embarrassing to admit, but they're like- - It's just you and I here.

Just you and I. - It's like 28 hours or 30 hour days. I'll just go all the way around comfortably and happily. I love it. And then there'll be a nap. I mean, if you add up the hours, when I'm just sleeping as much as I want, it'll probably be like six hour average per 24 hours.

So it works out nicely. Maybe even seven hours, I don't know. But it's obviously irregular and there's chaos in the whole thing. So sometimes it's shorter sleep, sometimes it's longer. Is that totally not a good thing, do you think? - The best evidence that we have to speak to this question is people who are doing rotating shifts.

And unfortunately, the news is not good. They usually have a higher instance of many diseases such as depression, diabetes, cardiovascular disease, obesity, stroke, and (silence) And again, that's just me communicating the data that we have and I'm not telling you that you should do anything different. The other thing is that there's nothing in your biology that suggests that that's how your body was designed to sleep.

It is a system that loves habit. If your circadian clock in your brain, it's called the suprachiasmatic nucleus, sits in the middle of your brain, had a personality trait, it would be a creature of habit. It loves habit. That's how your biology is designed to work is through very archetypal, prototypical, expected cycles.

And when we do something different to that, then you start to see some of the pressure, stress, fractures in the system. But again, to your point, if that's something that you don't mind, adopting and understanding, then I think you should keep doing what you're doing. - It's complicated. Of course, you have to be a student of your own body and explore it.

One of the reasons I wanna have kids is kids enforce a stricter schedule. (laughing) I think I definitely-- - So I've heard. - I definitely feel that I'm not living the sort of data-wise, scientifically speaking, the optimal life. And me just living the way I wanna live day-to-day is perhaps not the optimal way.

And there's certain things that I've seen, very successful people that I know in my life, when they have kids, they actually, their productivity goes up, they get their shit together. There's a lot of aspects that-- - Regularity, yeah. - Yeah, the regularity. I mean, that creatures a habit. That's the thing, that's power.

And then you start to optimally use the hours you have in the day. Let me ask you about-- - Well, actually, I just have one quick point on that too. We often think about sleep as a cost, but instead I think of sleep as an investment. And the reason is because your effectiveness and your efficiency when you're well-slept typically exceeds that when you're not.

And to me, it's the idea of, if I'm going to boil a pot of water, why would I boil it on medium when I could boil it in half the time on high? - Yeah. - And I sometimes worry that when I speak to Fortune 500 companies, and they're of this mentality of long hours, getting people to rise and grind.

The first point is that after about 20 hours of being awake, a human being is as cognitively as impaired as they would be if they were legally drunk. And the reason I bring that point up is because I don't know any company or CEO who would say, I've got this great team, they're drunk all the time.

But we often lord the airport warrior who's flown through three different time zones in the past two days is on email at 2 a.m. and then is in the office at six. And I think there is some aspect, not in all people, but there is sort of some aspect of that slight sleep machismo.

And that's not what, you are very different. You are driven by a purity of passion and a very authentic, incredibly genuine goal of wanting to do something remarkable with your life. That's not the issue I think I'm speaking about. It's just simply that I think the, this notion of wanting to be awake for longer to try and get more done can sometimes be at odds with the fact that you can actually get so much more done if you're well slept.

And it's this trade off. - I actually admire people that take the big risk and work hard, whether that means staying up late at night, all those kinds of things, but it cannot be in the framework, in the context, like what Edison said, which is sleep feels like a waste of time.

So like, if you're not sleeping because you think sleep is stupid, that's totally wrong. But if you're not sleeping because you're deeply passionate about something, that to me, it's a gray area, of course, but that to me is much more admirable. And everything you're espousing is saying like, whatever the hell you're doing, you better be aware that sleep, long-term and short-term is really good for you.

So if you're not sleeping, you're sacrificing, just make sure you're sacrificing for the right thing. I see vodka and getting drunk the same way. I know it's not good for me. I know I'm not gonna feel good days after. I know it's gonna decrease my performance. There's nothing positive about it, except it introduces chaos in my life that introduces beautiful experiences that I would not otherwise have.

It creates like this turmoil of social interaction that ultimately makes me happy that I've experienced them in the moment. And later the stories, you get to meet new people. So like alcohol in this society is an incredible facilitator of that. So like, that's a good example of like not sleeping and drinking way too much vodka.

- Again, it's this notion of life is to be lived to a degree, but if you do have children, I think one of the other things that then maybe comes into the picture is the fact that now there are other people that you have to live for than yourself.

- Yeah, but come on, like once they're old enough, like if you can't defend for yourself, you're too weak, get stronger. - It's gonna be that kind of fatherhood. I got it. I'm understanding so much more about like screaming than I did before. - That's why you have to have, for me that'd be, my wife would be probably softer.

It's good cop, bad cop. 'Cause I think I'm... But of course, actually, 'cause I don't have kids, I've seen some tough dudes when they have kids become like the softies. They become like, they do everything for their kids. It becomes like, it totally transforms their life. I mean, Joe Rogan is an example of that.

I've just seen so many tough guys completely become changed by having kids, which is fascinating to watch 'cause it just shows you how meaningful having kids is for a lot of people. - Although I would say having, chatted with Joe for some time, I think he is a delightful sweetheart, independent of children.

I think, don't get me wrong, I don't wanna be in a ring with him. He would face me five ways till Tuesday, but I think he's a desperately sweet man and a very, very smart individual. - Yeah, I mean, but he talks about the compassion he's gained from realizing, just watching kids grow up, that we were all kids at some point.

You get a new perspective. I think just like me, I still get this with him. He's super competitive and there's a certain way to approach life. Like you're striving to do great things and you're competitive against others and that intensity or that aggression, that can lack compassion sometimes and empathy.

And when you have children, you get a sense like, oh, everybody was a child at some point. Everybody was a kid. And you see that whole development process. It can definitely enrich, expand your ability to be empathetic. Let me ask about diet. So what's the connection between diet and sleep?

So I do intermittent fasting, sometimes only one meal a day, sometimes no meals a day. Is there a good science on the interaction between fasting and sleep? - We have some data. I would prefer more, but we have data both on time-restricted eating and then we have some data on fasting to a degree.

On time-restricted eating, I think that it has some benefits, although the human replication studies have actually not borne out quite the same health benefit to the extent that the animal studies have. There've been some disappointing studies, one here close to where we are right now at UCSF recently. So I think time-restricted eating can be a good thing.

And there are many benefits of time-restricted eating. Is sleep one of them? No, it doesn't seem to be because there are probably at the time that we're recording this, three pretty decent studies that I'm aware of. Two out of the three were in obese individuals. One out of the three were in healthy weight individuals.

And what they found was that time-restricted eating in all three of those studies didn't have any advantageous benefit to sleep. It didn't necessarily harm sleep, but it didn't seem to improve it. When it comes to fasting though, which is a different state, we don't have too many studies, experimental studies with long-term fasting.

The best data that we have is probably from religious practices. And probably the most data we have is during Ramadan where people will fast for 29 to 30 days from sunrise to sunset. And under those conditions, there are probably five distinct changes that we've seen. None of them seem to be particularly good for sleep.

The first is that the amount of melatonin that you release, and melatonin is a hormone. It's often called the hormone of darkness or the vampire hormone, not because it makes you look longingly at people's necklines, but it's just because it comes out at night. Melatonin signals to your brain and your body that it's dark, it's nighttime, and it's time to sleep.

Those individuals, when they were undergoing that regimen to fasting, the amount of melatonin that was released and when it was released, the amount of melatonin decreased and when it was released came later. That was the first thing. The second thing was that they ended up finding it harder to fall asleep as quickly as they normally would otherwise.

The third thing was that the total amount of sleep that they were getting decreased. The fourth fascinating thing was that a wake-promoting chemical called orexin increased. And this is why a lot of people will say, when I'm fasting, it feels like I can stay awake for longer. And I'm more alert, I'm more active.

And I'll come back to, from an evolutionary perspective, why we understand that to be the case. And then the fourth factor is that fasting didn't decrease the amount of deep sleep that seemed to be unaffected. It did, however, decrease the amount of REM sleep or dream sleep. And we know that REM sleep dreaming is essential for emotional first aid, mental health, it's critical for memory, creativity.

It's also critical for several hormone functions. It's when, you know, if you, there's direct correlations between testosterone, you know, testosterone release peaks just before you go into REM sleep and during REM sleep too. So REM sleep is critical. But, so those are the five changes that we've seen. None of them seem to be that advantageous for sleep.

But the fourth point that I mentioned, which was orexin, which is this wake-promoting chemical, and a good demonstration or a very sad demonstration of its power is when it becomes very deficient in the brain and it leads to a condition called narcolepsy, where, you know, you're just unpredictable with your sleep and you, so, so orexin when it's in high concentrations keeps you awake when you lose it, it can, you know, it can put you very much into a state of narcolepsy where you're sleeping a lot of the time in unpredictable sleep.

Why on earth, when you are fasting, would the brain release a wake-promoting chemical? And our answer is right now is the following. The, one of the few times that I mentioned before that we see animals undergoing insufficient sleep or prolonged sleep deprivation is under conditions of starvation. And that is an extreme evolutionary pressure.

And at that point, the brain will forego some, it won't forego all, but it will forego some of its sleep. And the reason is so that it can stay awake for longer because the sign of starvation is saying to the brain, you can't find food in your normal foraging perimeter, you need to stay awake for longer so you can travel outside of your perimeter for a further distance, and maybe you will find food and save the organism.

So in other words, when we fast, it's giving our brain this evolutionary signal that you are under conditions of starvation. So the brain responds by saying, oh my goodness, I need to release the chemical that helps the organism stay awake for longer, which is a rexin, so that they can forage for more food.

Now, of course, your brain from evolutionary perspective doesn't know about this thing called Safeway that you could easily go to and break the fast. But that's how we understand fasting. And I think, my dear friend, Peter Atiyah has done a lot of work in this area too. I think fasting and David Sinclair's brilliant work, goodness me, what an individual too.

The work is pretty clear there that time-restricted eating and fasting have wonderful health benefits. Fasting creates this thing called hermesis, just like exercise and low-level stress and sauna, heat, shock, and hermesis is a biological process, I think, as David Sinclair has once said, in simple layman's terms is, what doesn't kill you makes you stronger.

And I think there is certainly good data that fasting and time-restricted eating has many benefits. Is sleep one of them? It doesn't seem to be, it doesn't seem to enhance sleep. - But it's interesting to understand its effects on sleep. I've, like, I've fasted, it's a study of NF2, I've once fasted 72 hours and another time, 48 hours.

And I found that I got much less sleep and was very restful though. I hesitate to say this, but this is how I felt, which is I needed less sleep. I wonder if my brain is deceiving me because it feels like I'm getting a whole extra amount of focus for free.

And I wonder if there's long-term impacts of that. Because if I fast 24 hours, get the same amount of calories, one meal a day, there's a little bit of discomfort, like just maybe your body gets a little bit colder, maybe there's just, I mean, hunger, but the amount of focus is crazy.

And so I wonder, it's like, I'm a little suspicious of that. I feel like I'm getting something for free. I'm the same way with sweetener, like Splendor or something. It's like, it's gotta be really bad for you, right? 'Cause why is it so tasty, right? - And I think, yeah, as we said before, with biology, you don't get, if there's a gain, there's, yeah, there's often a cost too.

So, but we at least understand the biological basis of what you're describing. It's not that you actually don't need less sleep. It's that this chemical is present that forces you more awake. And so subjectively you feel as though, I don't need as much sleep because I'm wide awake. And those two things are quite different.

It's not as though your sleep need has decreased. It's that your brain has hit the overdrive switch, the overboost switch to say, we need to keep you awake because food is in short supply. - So you mentioned during sleep, there's assimilation, all those kinds of things for learning purposes, but there's also these, you mentioned the five ways in which we become psychotic in dreams.

What do you think dreams are about? Why do you think we dream? What place do we go to when we dream? And why are they useful? Not just the assimilation aspect, but just like all the crazy visuals that we get with dreams. Is there something you can speak to that's actually useful?

Like why we have such fun experiences in that dream world? - So one of the camps in the sleep field is that dreams are meaningless, that they are an epiphenomenal by-product of this thing called REM sleep from which dreams come from as a physiological state. So the analogy would be, let's think of a light bulb, that the reason that you create the apparatus of a light bulb is to produce this thing called light in the same way that we've evolved to this thing called REM sleep to serve whatever functions REM sleep serves.

But it turns out that when you create light in that way, you also produce something called heat. It was never the reason that you designed the light bulb, it's just what happens when you create light in that way. And the belief so too was that dreaming was essentially the heat of the light bulb.

That REM sleep is critical, but when you have REM sleep with a complex brain like ours, you also produce this conscious epiphenomenon called dreaming. I don't believe that for a second. (laughs) And from a simple perspective is that I suspect that dreaming is more metabolically costly as a conscious experience than not dreaming.

So you could still have REM sleep, but absent the conscious experience of dreaming was probably less metabolically costly. And whenever mother nature burns the energy unit called ATP, which is the most valuable thing, there's usually a reason for it. So if it's more energetically demanding, then I suspect that there is a function to it.

And we've now since discovered that dreams have a function. The first, as we mentioned, creativity. The second is that dreams provide a form of overnight therapy. Dreaming is a form of emotional first aid. And it's during dream sleep at night that we take these difficult, painful experiences that we've had during the day, sometimes traumatic, and dream sleep acts almost like a nocturnal soothing balm.

And it sort of just takes the sharp edges off those difficult, painful experiences so that you come back the next day and you feel better about them. And so I think in that sense, dreaming, it's not time that heals all wounds. It's time during dream sleep that provides emotional convalescence.

So dreaming is almost a form of, you know, emotional windscreen wipers. (both laughing) And I think, and by the way, it's not just that you dream, it's what you dream about that also matters. So for example, scientists have done studies with learning and memory where they have people learn a virtual maze.

And what they discovered was that those people who then dreamed, but dreamed of the maze, were the only ones who, when they woke up, ended up being better at navigating the maze. Whereas those people who dreamed, but didn't dream about the maze itself, they were no better at navigating the maze.

So it's not just that you, it's not, it's sort of necessary, but not sufficient. It's necessary that you dream, but it's not sufficient to produce the benefit. You have to be dreaming about certain things itself. And the same is true for mental health. What we've discovered is that people who are going through a very difficult experience, a trauma, for example, a very painful divorce, those people who are dreaming, but dreaming of that difficult event itself, they go on to gain resolution to their clinical depression one year later.

Whereas people who were dreaming just as much, but not dreaming about the trauma itself, did not go on to gain as much clinical resolution to their depression. So it's, I think to me, those are the lines of evidence that tell me dreaming is not epiphenomenal. And it's not just about the act of dreaming.

It's about the content of the dreams, not just the fact of a dream itself. - It's, first of all, it's fascinating. It makes a lot of sense, but then immediately takes my mind to, from an engineering perspective, how that could be useful in, for example, AI systems. If you think about dreaming as an important part about learning and cognition and filtering previous memories of what's important, integrating them, maybe you can correct me, but I see dreaming as a kind of simulation of worlds that are not constrained by physics.

So you get a chance to take some of your memories, some of your thoughts, some of your anxieties, and play with them, construct virtual worlds and see how it evolves, to play with those worlds in a safe environment of your mind, safe in quotes, 'cause you could probably get into a lot of trouble with the places your mind will go.

But this definitely is applied in much cruder ways in artificial intelligence. So one context in which this is applied is the process called self-play, which is reinforcement learning, where agents play against itself or versions of itself. And it's all simulated of trying different versions of themselves and playing against each other to see what ends up being a good.

The ultimate goal is to learn a function that represents what is good and what is not good in terms of how you should act in the world. - Right, you create a set of decision weights based on experience, and you constantly update those weights based on ongoing learning. - But the experience is artificially created versus actual real data.

- That's right. - So it's a crude approximation of what dreams are, which is you're hallucinating a lot of things to see which things are actually-- - No, I think it's been a theory that's been put forward, which is that dreaming is a virtual reality test space that is largely consequence-free.

What an incredible gift to give a conscious mind each and every night. - Now, the conscious mind, the human mind, is very good at constructing dreams that are nevertheless useful for you. Like, they're wild and crazy, but they're such that they are still grounded in reality to a degree where anything you learn in dreams might be useful in reality.

This is a very difficult thing to do 'cause it requires a lot of intelligence, it requires consciousness. This has been effectively recently been used in self-supervised learning for computer vision with the process of what's called data augmentation. That's a very crude version of dreams, which is you take data and you mess with it and you start to learn how a picture of a cat truly represents a cat by messing with it in different ways.

Now, the crude methods currently are cropping, rotating, distorting, all that kind of stuff, but you can imagine much more complicated generative processes that start hallucinating different cats in order for you to understand deeply of what it means for something to look like a cat. - What is the prototype of a archetype of a cat?

- Yeah, the archetype. That's a very difficult process for computer vision to go from what are the pixels that are usually associated with a cat to what is a cat in the visual space? In the three-dimensional visual space that is projected on an image, on a two-dimensional image, what is a cat?

Those are fundamentally philosophical questions that we humans don't know the answer to, like linguistically, but when we look at a picture of a cat and a dog, we can usually tell pretty damn well what's the difference. And I don't know what that is because you can't reduce that to pointy ears or non-pointy ears, furry or not furry, something about the eyes.

- It's been a longstanding issue in cognitive neuroscience, cognitive neuroscience too, is how does the brain create an archetype? How does it create schemas that have general applicability but yet still obtain specificity? That's a very difficult challenge. I mean, we can do it. We do it. It's rather bloody amazing.

- It seems like part of the toolbox is this controlled hallucination, which is dreams. - Well, it's a relaxing of the rigid constraints. I often think of dreaming as, it's from an information processing standpoint, the prison guards are away and the prisoners are running amok in a delightful way.

And part of the reason is because when you go into dream sleep, the rational part of your brain called the prefrontal cortex, which is the part, it's like the CEO of the brain. It's very good at making high level, rational, top-down decisions and controlled actions. That part of the brain is shut down during REM sleep.

But then emotional centers, memory centers, visual centers, motoric centers, all of those centers actually become more active. In fact, some of them are more active than when we're awake in the dream state. - That's fascinating. - So your brain from a neural architecture perspective is radically different. Its network feature is not the same as wakefulness.

And I think this is an immensely beneficial thing that we have at least two different rational and irrational conscious states that we do information processing in. The rational, the veritical, the page one of the Google search is wakefulness. The more irrational, illogical, hyper-associative, Google page 20 is the REM sleep.

Both I think are critical, both are necessary. - That's fascinating. And again, fascinating to see how that could be integrated in the machines to help them learn better and to reason better. - And in some ways, we also know it from a chemical perspective too. When you go into dream sleep, it is a neurochemical cocktail like no other that we see in the rest of the 24-hour state.

There is a chemical called noradrenaline or norepinephrine in the brain. And you know if it's sister chemical in the body called adrenaline, but upstairs in the brain, noradrenaline is very good at creating a very hyper-focused, attentive, narrow, it's sort of very convergent way of thinking to a point, sharp, focus, that's the only thing.

The spotlight of consciousness is very narrow. That's noradrenaline. When you remove noradrenaline, then you go from a high SNR, high signal to noise ratio, where it's just you and I in this moment. I don't even know what's going on elsewhere. I am with you, noradrenaline is present. But when you go into REM sleep, it is the only time during the 24-hour period where your brain is devoid of any noradrenaline.

It is completely shut off. And so the signal to noise ratio is very different. It's almost as though we're injecting a greater amount of noise into the neural architecture of the brain during dream sleep, as if it's chemically brute-forced into this relaxed associative memory processing state. And then from an anatomical perspective, just as I described, the prefrontal cortex goes down and other regions light up.

So it is a state that seems to be very, I mean, if you were to show me a brain scan of REM sleep and tell me that it's not REM sleep, just say, "Look, based on the pattern of this brain activity, what would you say is going on in this person's mind?" I would say, "Well, they're probably not rational.

They're probably not having logical thought because their prefrontal cortex is down. They're probably feeling very emotional because their amygdala is active, which is an emotional center of the brain. They're definitely going to be thinking visually 'cause the back of the brain is lit up, the visual cortex. It's probably going to be filled with past experience and autobiographical memories because their memory centers are lighting up.

And there's probably going to be movement because their motor cortex is very active." That to me sounds very much like a dream. And that's exactly what we see in brain scanners when we've put people inside of them. - One of the things I notice sleep affects is my ability to see the beauty in the world.

- Yeah. - So what do you think is the connection between sleep and your emotional life? Your ability to love other human beings and love life? - Yeah. I think it's very powerful and strong. So we've done a lot of work in the field of sleep and emotion and sleep and moods.

And you can separate your emotions into two main buckets, you know, positive and negative. And what's interesting is that when you are sleep deprived and the more hours that you go into being awake and the fewer hours that you've had to sleep, your negative mood starts to increase. And we know which individual types of emotions are changing.

I've got a wonderful postdoc in my lab called Etty Ben-Simon, who's doing some incredible work on trying to understand the emotional, individual emotional tapestry of affective meltdown when you're not getting sufficient sleep. But let's just keep with two dimensions, positive and negative. - Yes. - The negative, most people would think, well, it's the negative that takes the biggest hit when I'm sleep deprived.

It's not. By probably a log order magnitude larger is a hit on your positive emotions. In other words, you stop gaining pleasure from normally pleasurable things. And it's a state that we call anhedonia. And anhedonia is the state that we often call depression. So depression to most people's surprise isn't necessarily that you're always feeling negative emotions.

It's often more about the fact that you lose the pleasure in the good things in life. That's what we call anhedonia. That's what we see in sleep and insufficient sleep. And it happens quite quickly. - Yeah, it's kind of fascinating. I think I do, it's not depression, but like it's a stroll into that direction, which is when I'm sleep deprived, I stop being able to see the meaning in life.

The things that gave me meanings starts to lose meaning. Like stupid, it makes me realize how enjoyable everything is in my life. Because when I start to lose it, when I'm severely sleep deprived, you start to see how much life sucks when you lose it. But that said, I'm just cognizant enough that like sleep fixes all of that.

So I use those states for what they're worth. In fact, I personally like to pay attention to the things that bother me in doing that time. 'Cause they also reveal important information to me. - That's an interesting method to use like a Rorschach. - Yeah, I mean, there's, so I find this when I fast combine with sleep deprivation, am clear to see with people, clear in identifying the things that are not going right in my life, or people that I'm working with are not doing as good of a job as they could be doing.

Like people that are negative in my life, I'm more able to identify them. So I don't act on that. It's a very bad time to act on those decisions. But I'm like recording that information because I usually when I'm well rested and happy, I see the beauty in everybody, which can get you into trouble.

So you have to balance those two things. But yes, it's fascinating. - But there's irony there too, which is the fact that when you're well rested and well slept, as you said, you see the beauty in life and it sort of enlivens you and sort of gives you a quality of life that's emotionally very different.

Yet then we are contrasting that against the need for not getting enough sleep because of the beautiful things that you want to accomplish in life. And I don't actually see them as, sort of completely counterintuitive or paradoxical because I still think that you can strive for all of the brilliant things that you are striving for to have the monumental goals, the Herculean challenges that you wish to take on and solve.

They can still enthrall you and excite you and stimulate you. But because of the insufficient sleep that they can or that goal can produce, it will shave off the beauty of life that you experience in between. And again, this is just about the trade-off. I will say though that, and this is not applicable to your circumstance, we do know that insufficient sleep is very strongly linked to suicide ideation, suicide attempts and tragically suicide completion as well.

And in fact, in 20 years of studying sleep, we have not been able to discover a single psychiatric condition in which sleep is normal. And I think that that is a profound state. I think it tells us so much about the role of sleep as a potential causal agent in psychiatric conditions.

I also think it's a potential sign that we should be using sleep as a tool for the prevention of grave mental illness. - Yeah, it's both a cause and a solution. So, I mean, me personally, I've gone through a few dark periods quite recently and it was almost always sleep is not the cause, but sleep is the catalyst from going to a bad time to a very bad time.

- Yeah. - And so it's definitely true. And it's funny how sleep can just cure all of that. - There's actually a beautiful quote by an American entrepreneur called E. Joseph Kosman, who once said that the best bridge between despair and hope is a good night's sleep. And I spilled so much ink and hundreds of pages inelegantly trying to say the same thing in my book.

And he said it in one line and it's beautiful. - What do you think is, we've been talking about how to extend this life, how to make it a good life. We've been talking about love. What do you think is the meaning of this whole ride? - Of life?

- Of life. Why do we want to make it a good one? Do you think there's a meaning? Do you think there's a answer to the why? - For me personally, I think the meaning of life is to eat, is to sleep, is to fall in love, is to cry, and then to die.

Oh, and probably race cars in between. - Race cars. Well, there's a whole topic of sex we didn't talk about, so that's probably in there somewhere. - Should we do that? - Maybe if you'll have me back, I would love to do it. I will go around. - Next time we will do another three hours on sex alone.

- Yeah. - It has been over three hours, yes. - Okay. - Matt, I'm a big fan of your work. I think you're doing really important work, even despite all the things I've been saying about the madness of my own sleep schedule. I think you're helping millions of people.

So it's an honor that you spend your valuable time with me. And I can't wait until your podcast comes out. I'm a huge fan of podcasts. I'm a huge fan of you. And it's just an honor to know you and to get a chance, hopefully in the future, to work together with you.

- You're a brilliant man and you're doing amazing things. And I feel immensely honored to have met you, to now know you, and to start calling you a friend. Thank you for what you do for the world and for me included. - Thank you, Matt. - Take care. - Thanks for listening to this conversation with Matt Walker.

And thank you to stamps.com, Squarespace, Athletic Greens, BetterHelp, and Onnit. Check them out in the description to support this podcast. And now let me leave you with some words from Nikola Tesla, who we discussed in this podcast as sleeping very few hours a night. "All that was great in the past was ridiculed, "condemned, combated, and suppressed, "only to emerge all the more powerfully, "all the more triumphantly from the struggle." Thank you for listening and hope to see you next time.

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