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Matt Walker: Sleep | Lex Fridman Podcast #210

2 hours 48 minutes 17 seconds

🇬🇧 English

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Speaker 1

00:00

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's putting out an audio series soon too.

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Speaker 1

00:32

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.

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Speaker 1

00:49

As a side note, let me say that to me, a healthy life is 1 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 on to and chase for years. Life should be lived fully. That to me is the priority. That to me is a healthy life.

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Speaker 1

01:12

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.

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Speaker 1

01:46

We agree on some things and disagree on others, but he's a great human being, a great scientist, and is 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.

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Speaker 2

02:04

You should try these shades on and see what you look like. So they are now your shades. And that's not a question.

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Speaker 3

02:14

It's the Same thing as Putin took the Super Bowl ring and it's now his ring.

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Speaker 2

02:20

Yeah, 1 wonders if he was offered it, but they are yours.

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Speaker 3

02:26

When did you first fall in love with the dream of understanding sleep? Like where did the fascination with sleep begin?

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Speaker 2

02:38

So back in the United Kingdom, you can sort of start doing medicine at age 18 and it's a 5 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.

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Speaker 2

02:57

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.

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Speaker 2

03:15

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.

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Speaker 2

03:36

No 1, as I recall, in the classroom when you're sort of 5 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.

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Speaker 2

04:00

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?

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Speaker 2

04:18

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.

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Speaker 2

04:38

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.

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Speaker 2

05:02

And at that point, which was, cough, cough, 20 years ago, no 1 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.

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Speaker 2

05:33

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?

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Speaker 2

05:50

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.

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Speaker 2

06:06

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.

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Speaker 3

06:30

So far the answer seems to be no. So why does the body and the mind crave sleep then? Why do we sleep?

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Speaker 3

06:42

How can we begin to answer that question then?

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Speaker 2

06:45

So I think 1 of the ways that I think about this or 1 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 1 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.

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Speaker 2

07:12

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. 1 is when they're in a condition of severe starvation. The second is when they're caring for their newborn.

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Speaker 2

07:31

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 1 is during migration when birds are flying trans oceanographic to 3000 miles.

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Speaker 2

07:51

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.

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Speaker 2

08:22

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?

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Speaker 2

08:42

Where is that sort of banking chip for sleep? And unfortunately, we don't seem to have 1 because she's never had to face that challenge. So even if there's not some kind of physics

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Speaker 3

08:52

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.

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Speaker 3

09:14

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?

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Speaker 2

09:30

We don't just sleep for 1 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 1 of those grounds, but especially as a collective, sleep should have been strongly selected against in the course of evolution.

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Speaker 2

10:00

But in every species that we've studied carefully to date, sleep is present.

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Speaker 3

10:05

Yeah, so it is important. So like, you're right. I think I've heard arguments from an evolutionary biology perspective that sleep is actually advantageous.

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Speaker 3

10:15

You know, 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. Like, why close your eyes?

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Speaker 2

10:27

Yeah, why? Because, and you know, 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.

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Speaker 2

10:45

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.

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Speaker 2

11:26

It's called lethargics. 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.

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Speaker 3

12:00

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?

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Speaker 3

12:13

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?

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Speaker 2

12:28

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 3 main states of consciousness.

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Speaker 2

12:44

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 3 states within which your brain could percolate and be conscious. You know, 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.

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Speaker 2

13:11

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.

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Speaker 2

13:56

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 microsleep events at the wheel.

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Speaker 2

14:34

Now, if you're traveling at 65 miles an hour in a two-ton vehicle, it takes probably around 1 second to drift from 1 lane to the next, and it takes 2 seconds to go completely off the road. So if you have 1 of these microsleeps at the wheel, you know, it could be the last microsleep 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 1 or A0I see it more

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Speaker 3

15:05

of a, as a continuum. Yeah. So I've for 5, 6 years at MIT, really focused on this human side of driving question.

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Speaker 3

15:17

And 1 of the big concerns is the micro-sleeps, drowsiness, these kinds of ideas. And 1 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?

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Speaker 3

15:41

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 1. Just because you're looking at something doesn't mean you're loading in the information.

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Speaker 3

16:00

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, you know, they say the eyes are the windows to the soul. Do you think

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Speaker 1

16:17

the eyes can reveal something about

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Speaker 3

16:21

sleepiness through computer vision, 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.

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Speaker 3

16:34

It's a fascinating problem. But drowsiness is a tricky 1. So there's what kind of information? There's blinking and there's eye movement.

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Speaker 3

16:42

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?

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Speaker 2

16:52

Yeah, I do. And I think there are a number of other features too. I think, you know, aperture of eye, so in other words, partial closures, full closures, duration of those closures, duration of those partial closures of the eyelid.

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Speaker 2

17:09

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.

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Speaker 2

18:00

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.

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Speaker 3

18:19

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.

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Speaker 3

18:40

So if you have to constantly correct the car, that's a sign of like you starting to drift into micro sleep. I think that's a very, very crude signal. It's probably a powerful 1. There's a whole nother component to this, which is it seems like it's so driver and subject dependent.

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Speaker 3

18:59

How our behavior changes as we get sleepy and drowsy seems to be different in complicated, fascinating ways where you can't just use 1 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.

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Speaker 2

19:23

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.

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Speaker 2

19:44

Some of those, let's say that there are 10 of them, for me, 7 of them are the cardinal features. For you, however, 6 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.

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Speaker 3

20:09

And it

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Speaker 2

20:10

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.

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Speaker 2

20:26

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 1 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.

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Speaker 2

20:54

But to start with, I think your approach is a great 1. Let's find something that covers 99% of the people, because the worrying thing about microsleeps, of course, unlike drugs or alcohol, which 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

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Speaker 3

21:29

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.

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Speaker 3

21:43

Elon Musk, is, and the human factors community, which is this community that 1 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.

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Speaker 3

22:21

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.

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Speaker 3

23:05

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.

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Speaker 3

23:36

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

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Speaker 2

23:43

the side. Right, or I need to do some of the heavy lifting here.

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Speaker 3

23:47

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.

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Speaker 2

24:09

I agree, yeah. I think there are far more sophisticated ways that we can solve that problem if we invest.

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Speaker 3

24:17

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.

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Speaker 3

24:36

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?

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Speaker 2

25:06

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're sort of, you know, you've risen above your physical being.

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Speaker 2

25:45

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.

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Speaker 2

26:04

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.

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Speaker 3

26:18

And

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Speaker 2

26:18

there are 5 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.

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Speaker 2

26:30

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.

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Speaker 2

26:51

So you're suffering from amnesia. If you had to experience any 1 of those 5 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.

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Speaker 2

27:24

And if it's that hard, you know, 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 1 thing that won't go away, that won't get perturbed or sort of, you know, manacled, is this your sense of conscious self?

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Speaker 3

27:58

Yeah, that'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.

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Speaker 2

28:15

I mean, it's like trying to launch a rocket. 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.

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Speaker 3

28:46

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.

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Speaker 3

29:02

I'm 1 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.

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Speaker 3

29:21

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.

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Speaker 3

29:50

But then we don't even know what consciousness is and we certainly don't know how to engineer it in our machines.

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Speaker 2

29:56

I love the fact that there are still questions that are so embryonic, because I suspect it's the same with you, answers to me are simply ways to get to more questions. It's questions where 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.

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Speaker 2

30:23

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 humans to mammals to sort of birds to reptiles, amphibians, fish, bacteria, whatever you want. And you can go through this and say, okay, where is the hard line of 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.

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Speaker 2

30:57

But to me, it's always been fascinating. So what is it then? 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 interconnected human brain then bingo.

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Speaker 2

31:17

All of a sudden it kicks into gear and we have consciousness.

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Speaker 3

31:21

Like a phase shift, phase transition of some kind.

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Speaker 2

31:23

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.

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Speaker 2

31:52

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 complimentary, more orthogonal.

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Speaker 2

32:24

So I'm sometimes perplexed that people are trying to mimic human consciousness rather than think about creating something that's different.

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Speaker 3

32:34

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.

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Speaker 3

33:01

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, that 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.

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Speaker 3

33:47

So like, 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 a word. 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.

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Speaker 3

34:13

And that's how I

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Speaker 2

34:15

see- Get me that t-shirt, please. I love that.

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Speaker 3

34:18

So, and you know, 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.

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Speaker 3

34:31

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

S2

Speaker 2

34:53

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.

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Speaker 3

35:01

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 Scent of a Woman is a better movie than John Wick. Because it's 1 of my favorite movies for many reasons. 1 is...

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Speaker 3

35:20

Or Scent of a Woman. Scent of a Woman. I didn't know that, by the way. You just tossed

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Speaker 2

35:27

that out there. I didn't know if you would actually know of the movie.

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Speaker 3

35:29

Awesome. I said I love the tango scene. I love Al Pacino's performance. It's a wonderful movie.

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Speaker 3

35:36

Then Joe was saying John Wick is better. So we to this day argue about this.

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Speaker 2

35:41

I think it depends on what conscious state you're in that you would be ready and receptive to. But, Sensible Woman, I think it has 1 of the best monologues at the end of the movie that has ever been written or at least performed.

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Speaker 3

35:57

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.

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Speaker 3

36:18

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.

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Speaker 3

36:30

To come in. Slade.

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Speaker 2

36:30

Yeah, to come in

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Speaker 3

36:33

on your side and scream at everyone and say, what the hell are we doing here? Being, you know, unfortunately British

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Speaker 2

36:41

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 2 minutes to lose it.

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Speaker 2

37:06

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.

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Speaker 2

37:25

And the irony relative to something like mathematics is that in science, you never find truth. What will 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, you know, from that point forward, there is truth in mathematics. And there's, 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.

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Speaker 3

38:07

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. 1 is like funding sources.

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Speaker 3

38:19

I've noticed this, that money affects everyone's mind, I think. I've been always somebody that I believe money, 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, you know, for a couple of decades publishing an idea and then realizing at some point that that idea was wrong all along.

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Speaker 3

38:58

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.

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Speaker 3

39:18

That's an all of that is integrity. When everybody in the room, you know, 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.

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Speaker 2

39:30

Yeah, and I think it comes down in some ways to the issue of ego, that you bond your, you know, correctness or your rightness, your scientific theory, with your sense of ego. You know, 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.

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Speaker 3

39:56

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.

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Speaker 3

40:10

Like some kind of weird drive, maybe like drive to be better. Like thinking of yourself as 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.

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Speaker 3

40:33

It seems to be a nice combination.

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Speaker 2

40:35

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

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Speaker 3

40:49

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.

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Speaker 3

41:06

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. How About talking to me? Yeah, yeah. Oh, I like.

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Speaker 3

41:18

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.

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Speaker 2

41:31

I have.

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Speaker 3

41:34

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?

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Speaker 2

41:59

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.

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Speaker 2

42:11

But with the podcast, I think really I have 2 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.

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Speaker 2

42:38

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.

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Speaker 3

42:53

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.

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Speaker 3

43:05

So he does like 2 hours of, I wonder how many takes he does, I don't know, but it looks like he doesn't do any. Yeah, I

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Speaker 2

43:13

suspect he's that magnificent of a human being.

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Speaker 3

43:16

When I talk to him in person, he always generates intelligent words, well-cited, nonstop for hours.

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Speaker 2

43:24

So I don't. He's a Gatlin gun of information and it's pristine.

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Speaker 3

43:28

And passion and all those kinds of things. That's an interesting medium. It's funny, because I wouldn't have done it the way he's doing it.

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Speaker 3

43:37

I wouldn't advise him to do it the way he's doing it. Because I thought there's no way you could do what you're doing. Because 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 and hardcore history.

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Speaker 3

43:53

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 2 episodes a year. So that pressure can be paralyzing. The pressure of like putting out like strong scientific statements that that can be overwhelming.

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Speaker 3

44:17

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 or 2 a week of just nonstop dropping knowledge. Any 1 sentence of which could be totally wrong.

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Speaker 3

44:40

It could be a mistake.

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Speaker 2

44:42

And there will be mistakes. And I, in the first edition of my book, there were errors that, you know, we corrected in the second edition too. But there will be probabilistically, you know, if you've got, you know, 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.

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Speaker 2

45:11

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

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Speaker 3

45:27

wanna say that I'm just kinda 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.

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Speaker 2

45:42

Oh, I hope so. David is another 1 of those very special people in the world.

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Speaker 3

45:47

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.

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Speaker 3

46:04

And so it's a really exciting medium to me. And it's cool that there's this like 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. Because I wonder, it'll be 2 a month.

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Speaker 2

46:20

Or devolve. Devolve. Is the answer to that.

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Speaker 3

46:24

Well, I mean, some of it is persistence through the challenges that we've been talking about, which is like.

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46:30

I think I've got a lot to learn.

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Speaker 3

46:32

Yeah. But I will persist. We can ask you some detailed stuff. You mentioned that 1.

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Speaker 3

46:38

0 my

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Speaker 2

46:38

goodness, go anywhere you wish with sleep.

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Speaker 3

46:41

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.

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Speaker 3

47:00

I seem to be not at all affected by it. It's almost, it feels like 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.

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Speaker 3

47:24

All that to say, what do you think is the relationship between coffee and sleep, caffeine and sleep? If There's

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Speaker 2

47:33

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.

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Speaker 2

47:43

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, you know, 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.

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Speaker 2

48:28

How on earth can you reconcile those 2? And the answer is that, well, the answer is very simple. It's called antioxidants. But 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.

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Speaker 2

48:51

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.

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Speaker 2

49:20

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 3 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.

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Speaker 2

49:44

But let's say that you are 1 of those individuals, and I think you are, and you can say, look, I can have 3 or 4 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.

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Speaker 2

50:22

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 3 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.

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Speaker 2

50:47

The second component is the timing though. Caffeine has half-life of about 5 to 6 hours, meaning that after 5 to 6 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, 1 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.

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Speaker 2

51:22

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 2 cups of coffee in the morning, I don't sleep as well at night. And I find it miserable because I love the smell of coffee.

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Speaker 2

51:40

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.

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Speaker 2

51:47

So I switched to decaf. There is a difference from 1 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.

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Speaker 2

52:17

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 2 hours rather than 5 to 6 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, you know, 8 to 9 hours.

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Speaker 2

52:47

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.

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Speaker 3

53:01

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 I drink a lot of coffee, it's just like habit, alters how your body's able to get rid of the caffeine.

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Speaker 2

53:27

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.

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Speaker 2

53:51

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 1 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, you know, 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.

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Speaker 2

54:30

This is too much. So I'm just going to, when normally I would coat my cell with, let's just say 5 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 2 of those receptors and downscale it to just having 3 of those. And now you need 2 cups of coffee to get the same effect that 1 cup of coffee got you before.

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Speaker 2

54:55

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

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Speaker 3

55:12

and

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Speaker 2

55:12

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.

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Speaker 3

55:33

But

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Speaker 2

55:34

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, you know, 10 weeks ago or 3 months ago, that dose can kill them.

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Speaker 2

55:56

They can have an overdose. Even though they were using the same amount at those 2 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.

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Speaker 3

56:10

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?

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Speaker 3

56:35

Or is this advice kind of impossible because there's so much variability? There is huge variability.

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Speaker 2

56:41

And I think everyone themselves, you know, to a degree knows it, although I'll put a caveat on that too, because it's slightly dangerous point. So the recommendation for the average adult and who, 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.

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Speaker 2

57:02

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.

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Speaker 3

57:17

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

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Speaker 2

57:35

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.

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Speaker 2

58:08

And without sleep, the memory circuits of the brain, and we know we've studied these memory circuits, will 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.

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Speaker 2

58:45

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.

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Speaker 2

59:22

So the brain has, in some ways by default, there is forget, and actually I would love to, I was going to say sleep is relevant for memory in 3 different ways, but I'm going to amend that and say there's 4 different ways, which is learning, maintaining, memorizing, abstraction, assimilation, association, then forgetting, which the last 1 sounds oxymoronic based on the former 3, but I'll see if I can explain. So sleep after learning then sort of, you know, sets that information like amber.