Time Perception & Entrainment by Dopamine, Serotonin & Hormones

- Welcome to the Huberman Lab Podcast

where we discuss science and science-based tools

for everyday life.

[bright guitar music]

I'm Andrew Huberman and I'm a professor of neurobiology

and ophthalmology at Stanford School of Medicine.

Today we are talking about time perception.

Our perception of time is perhaps the most important factor

in how we gauge our life,

that is whether or not we think we are being successful,

whether or not we are failing,

whether or not we live in fear,

whether or not we live in relation to things

in a way that's positive, and the reason for that

is that our perception of time is directly linked

to the neurochemical states that control mood,

stress, happiness, excitement,

and of course it frames the way

in which we evaluate our past,

so whether or not we think of our past

as successful or unsuccessful.

It frames our present,

whether or not we think we are on track or off track.

And it frames our sense of the future,

whether or not we think we have a bright future,

a dim future,

or whether or not the future is very uncertain or not.

Today, we're going to talk about the science

of time perception and we are going to talk about tools

and protocols that you can use that can enhance your ability

to dilate and contract time.

What do we mean by dilate and contract time?

We can control the speed at which we experience life.

We can slow things down

or we can speed our experience of life up.

And we can do that in a very direct and dynamic way.

It's actually not that hard

once you understand how time perception works.

So that's where we're headed.

I think you're going to come away from today's episode

with a lot of new knowledge and certainly with many tools

that you can try in your daily life,

whether or not that's work, sport,

relational, emotional, and so on.

Before we begin our discussion about time perception,

I'd like to answer some questions that I received

related to the episode on fasting

and time-restricted feeding.

If you haven't seen that episode,

this information should still be of use to you.

Time-restricted feeding involves eating

for a particular period of time

in each 24-hour cycle that's fairly regular.

So this would be an eight-hour most often

or a 10-hour block.

Some people do shorter feeding windows, but regardless,

that feeding window is supposed to fall

at more or less the same period within each 24-hour day.

This has a number of positive effects on gene expression

that regulate a number of positive effects

on the different tissues of the body, and for some people,

not all, but for some people makes weight loss easier

because of the way that they are not eating

for large periods of each 24-hour cycle.

In any event, one of the major questions I got

after that episode was do supplements break a fast?

And during that episode,

I talked about what breaks a fast is highly contextual.

It basically boils down

to whether or not something you ingest,

whether it be liquid or food,

increases your resting blood glucose,

how much it increases that resting blood glucose,

and how long that increase lasts.

So you can check out the episode

for more about what breaks a fast,

but to address this issue about supplements

and whether or not supplements in particular break a fast,

many of the questions were about Athletic Greens.

Athletic Greens is a sponsor of this podcast.

It is also a terrific supplement that I'd been taking

for more than a decade before this podcast launched.

And many people have been using

and continue to use Athletic Greens.

Does Athletic Greens break a fast?

Well, that will somewhat depend

on whether or not your resting blood glucose

tends to run high or low, but for most people,

including me, because I've measured it,

ingesting Athletic Greens does not break a fast

and if it happens to break a fast,

it would be a very transient break in fast.

So without knowing your resting blood glucose levels

on an individual basis, there's no way I can say for sure

that it doesn't break a fast, but chances are it does not

because it doesn't contain much carbohydrate or sugar

and it doesn't tend to therefore pull you

out of the molecular mill you associated

with low blood glucose states.

The other question I get is whether or not things

like fish oil break a fast, and once again,

this will be contextual,

but because fish oil is a fat, an essential fat,

mainly essential fatty acids, in particular EPA and DHA,

those don't tend to raise blood glucose very much.

In my case, having measured

using a continuous glucose monitor my resting blood glucose,

fish oil does not in any way change

my resting blood glucose.

Chances are it won't do that for most people as well.

So does fish oil break a fast? Chances are it does not.

And of course people wanted to know

about pill-type supplements, you know,

caffeine and things that raise dopamine

and their vitamins and minerals.

In general, if something doesn't contain sugar

or much carbohydrate of any kind,

it's not going to raise blood glucose very much.

Now, of course, protein can raise blood glucose

and fat can too as well, although to a lesser extent.

So again, this is all contextual,

but at least by the logic that I just spelled out,

Athletic Greens, fish oil, and most forms of supplements,

provided they don't have any sugar or protein content,

should not quote unquote break a fast.

Before we begin, I'd like to emphasize

that this podcast is separate from my teaching

and research roles at Stanford.

It is however part of my desire and effort

to bring zero cost to consumer information about science

and science-related tools to the general public.

In keeping with that theme,

I'd like to thank the sponsors of today's podcast.

Our first sponsor is ROKA.

ROKA makes eyeglasses and sunglasses

that are of the absolute highest quality.

I've spent a lifetime working on the visual system

and one of the key things about our visual system

is that it's designed so that when you move into areas

where it's sunny or where there are shadows,

you can still see things with crystal clarity.

Many sunglasses out there have the problem

that you have to keep taking them off

and putting them back on

depending on the overall so-called ambient environment

that you're in.

ROKA sunglasses have solved this problem

and their eyeglasses also have super clarity

regardless of overall ambient lighting, as we say.

In other words, you see everything very clearly

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They also come in a number of different styles.

The aesthetics are really terrific.

So unlike a lot of performance glasses out there

that make people look like cyborgs,

you can wear them anywhere.

You can wear them to dinner.

You can wear them to school or work

or in social engagements and you can wear them running

and cycling and out doing your various activities.

If you'd like to try ROKA glasses,

you can go to ROKA that's R-O-K-A, .com

and enter the code Huberman

to save 20% off your first order.

Today's episode is also brought to us by Athletic Greens.

Athletic Greens is an all-in-one

vitamin mineral probiotic drink.

I started using Athletic Greens way back in 2012

and so I'm delighted that they're sponsoring the podcast.

The reason that I started using Athletic Greens

and the reason I still take Athletic Greens

once or twice every day is that it covers

all of my foundational needs for vitamins,

minerals, and probiotics.

In fact, when people ask me

what supplements they should take,

if I were going to recommend just one supplement,

it would be Athletic Greens because of the enormous number

of biological factors that it impacts in a positive way.

It has, as I mentioned, vitamins and minerals.

The probiotics are really important for the gut microbiome

and gut health which is important for the immune system

and for brain health and for mood

and a number of other important factors

including hormones and so on.

If you'd like to try Athletic Greens,

you can go to athleticgreens.com/huberman

to claim their special offer.

They'll give you five free travel packs

which make it really easy to mix up Athletic Greens

while you're on the road or in the car.

And they'll give you a year's supply of vitamin D3 K2.

Vitamin D3 and K2 have been shown to be really important

for a number of important aspects of your immediate

and long-term health including blood lipid profiles

and a number of other things.

Again, go to athleticgreens.com/huberman

to get the Athletic Greens, the five free travel packs,

and the year's supply of vitamin D3 K2.

Today's podcast is also brought to us by InsideTracker.

InsideTracker is a personalized nutrition platform

that analyzes data from your blood and DNA

to help you better understand your body

and help you reach your health goals.

I've long been a believer in getting regular blood work done

for the simple reason that many of the factors

that impact your immediate and long-term health

can only be analyzed from a quality blood test

and it's for that reason that I get my blood work done

once every four to six months.

Might seem like a lot, but it has been vital

in order to keep my health where I want it

and to ensure that my health trajectory is heading

in the direction that I'd like it to go

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Maybe you should be eating more of certain things,

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If you'd like to try InsideTracker,

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So let's talk about time perception

and the most fundamental aspect of time perception

is something called entrainment.

Entrainment is the way in which your internal processes,

your biology and your psychology,

are linked to some external thing.

And the most basic form of entrainment

that we are all a slave to all year round

for our entire life are so-called circannual rhythms.

We have neurons, nerve cells in our eye, in our brain,

and in our body that are marking off the passage of time

throughout the year,

literally a calendar system in your brain and body.

And the way this works is beautifully simple.

Light seen by your eyes inhibits, meaning it reduces,

the amount of a hormone released

in your brain called melatonin.

Melatonin has two major functions.

One function is to make you sleepy at night

and the other is to regulate some of the other hormones

of the body, in particular testosterone and estrogen.

When we view light,

we reduce the amount of melatonin released.

In fact, if you wake up in the middle of the night,

when melatonin typically is pretty high in your brain

and body and you flip on a bright light in the bathroom,

your melatonin levels crash down

to almost zero and stay there.

Light is a very powerful modulator of melatonin

and light inhibits melatonin.

Throughout the year, depending on where you live,

day length varies, and as a consequence,

the amount of light from the sun

that is available to you varies.

So when days are long, the amount of melatonin

in your brain and body that's released tends to be less.

There's less of it and it's released

for shorter amounts of time, okay?

Because light inhibits melatonin.

When days are very short, the amount of melatonin

that's released and the duration that that melatonin exists

in your brain and body tends to be much longer.

So melatonin correlates with day length.

And if we are viewing more light, we have less melatonin.

We view less light, we have more melatonin.

You see different amounts of light each day

but we have a process in our brain and body

that averages the amount of light that you're seeing

both from artificial sources and from sunlight

and measures that off, and it's so exquisitely precise

that for a given, say, eight-hour day in the spring,

'cause spring in the Northern Hemisphere or elsewhere,

you know, days are getting longer,

that means that the amount of melatonin

is getting progressively less and less

and that signal is conveyed to all the systems

of your brain and body.

And this is why most people, not all,

but most people feel like they have more energy

in the spring.

Conversely, when you have an eight-hour day

in the winter, the amount of melatonin

that corresponds to that eight-hour day

is getting progressively greater and greater because why?

Days are getting shorter so melatonin is increasing

from day to day to day.

Every cell and system of your body pays attention to this,

and as a consequence, most people, not all,

but most people feel they have a little less

or sometimes a lot less energy

and a slightly lower mood in the winter months.

Now, there are exceptions to this, of course,

but the melatonin signal is the way

in which your internal state, your mood,

your sense of energy, even your appetite is entrained,

is matched to some external event.

In this case, the event is the rotation

of the Earth around the sun.

There are other forms of entrainment,

meaning the matching of your brain and body

to things that are happening in your external environment.

One particularly interesting example of this

was published last year by Parikh et al. in "Cell Reports,"

Cell Press journal, excellent journal,

showing that across the calendar year,

the amount of testosterone and estrogen

that human beings make varies

such that in longer days,

they tend to make more testosterone and estrogen

than in shorter days.

And this was correlated with things like desire

to seek out romantic partners or have romantic interactions

with their existing partners, even aggression,

although not violent aggression,

but sense of kind of willingness to argue

and to get into kind of combative states

and overall energy and mood.

This is something that had been hypothesized for a long time

but it had never really been cleanly demonstrated.

And what they showed was that it's actually the skin

that's taking information about the amount of light

and converting it into these increases

in testosterone and estrogen.

Light exposure to the skin, turns out about two hours a day,

this was sunlight, in this case, to the upper body,

these people weren't naked, they were wearing clothes

but their arms were exposed,

their upper back and neck and face were exposed,

they were not wearing hats, resulted in large increases,

significant increases in testosterone and estrogen.

Now you could probably export a tool from that if you liked.

That's not really what this podcast is about

but it's very clear that because the skin is acting

as an endocrine orman, organ, excuse me,

as kind of a hormone-influencing organ,

that getting light on the skin, not just to the eyes,

can influence our sense of wellbeing

by these hormone pathways, and the threshold there again

seemed to be about two hours a day.

It doesn't have to be very bright outside.

There can be cloud cover and so on.

Many people will probably ask

will sunscreen inhibit this effect?

And it doesn't appear that it does.

Obviously prioritize skin health and avoiding skin cancer.

Sunscreen is kind of a controversial topic nowadays,

maybe the topic for another podcast episode at some point,

but nonetheless, what the Parikh et al. study shows

and that's most relevant to today's podcast

is that we are entrained, we are matched

to the external light-dark cycle

and as the day length changes, our hormones change.

And we can override that with exposure to bright lights.

You know, people go sit on tanning beds.

That's not a practice I particularly myself engage in,

but, you know, there are a number of different ways

that people can override these processes.

But the point is very simple.

The point is that our perception of time is both conscious,

you know, it's waiting, watching the clock tick down,

and there are these slower, what we call oscillatory,

meaning up and down repeatedly, slower oscillatory events

related to day length that are influencing our hormones

like melatonin, testosterone, and estrogen,

and therefore our mood, our outlook, and even our behavior.

The next level of time or bin of time, as we say,

that we are all entrained or matched to

is the so-called circadian time cycle,

which is 24-hour rhythm.

This is perhaps the most powerful rhythm

that we all contain and that none of us can escape from.

We all have this circadian clock

that resides over the roof of our mouth.

The cells in that circadian clock fire,

meaning they release chemicals into our brain and body

on a very regular rhythm.

So across the 24-hour cycle,

they will be very active at some periods

and less active at others.

Not surprisingly, there are periods of every 24-hour cycle

when we are very active and we tend to be alert

and others when we are asleep.

Now, I've talked a lot about circadian rhythms

and sleep on this podcast previously

and so I don't want to repeat too much of that information

in detail, but I'm just going to give a summary

of how circadian entrainment works

because I haven't really covered that

in the context of time perception.

We have the circadian clock. It oscillates.

It goes up and down once every 24 hours and then repeats.

Every cell of our body has a 24-hour oscillation

in the expression of various genes.

How that works is actually really simple,

elegant, and interesting.

DNA, genes, make RNA. RNA is converted into proteins.

Every cell in our body has this beautiful 24-hour timer

where a gene is expressed.

And the important thing to understand about a given gene

in this context is that that gene is inhibited,

meaning it's reduced, by a particular protein,

by a little biological molecule in that cell.

So the gene gets expressed when there's very little

of that other molecule around.

DNA then becomes RNA.

RNA is translated into a protein

and that protein goes way, way up and the gene shuts down.

But as that protein gets used up

and its levels eventually drop low, low, low, low, low

to zero, the gene cycle kicks in again

and the gene gets expressed.

The RNA gets expressed in the protein again.

This all happens on a 24-hour cycle.

So it's a little built-in timer

in each and every one of our cells.

And I didn't list off the genes,

but for the aficionados out there,

they go by names like PER for period, BMAL,

CLOCK, and all these different things.

We call them the clock genes and those clock genes regulate

a number of different functions.

So every cell in our body has a 24-hour cycle

of gene and protein expression

and the Earth rotates once every 24 hours

and the processes that are happening

in every cell of our body are linked.

They are entrained, as we say,

to the outside light-dark cycle

because morning sunlight, evening sunlight,

and the lack of light in the middle of the night

make sure that the changes,

these oscillations that are occurring

within the cells of our brain and body are matched

to the outside light-dark cycle.

Don't want to go into all the details of how that happens

but there's some very simple tools that one can use

to ensure that your entrainment,

your circadian entrainment, is precise.

And I cannot emphasize enough how important it is

that your circadian entrainment be precise, why?

Because disruptions in circadian entrainment

cause huge health problems.

They increase cancer risk. They increase obesity.

They increase mental health issues.

They decrease wound healing.

They decrease physical and mental performance.

They disrupt hormones.

You want your cells to be linked to the circadian cycle

that's outside you and the circadian cycle outside you

mainly consists of when there's sunlight

and when there is not.

And that's why the simple protocols

to fall out of this whole discussion

about circadian entrainment are the following.

View 10 to 30 minutes of bright light,

ideally sunlight, within an hour of waking

assuming that you're waking early in the day especially.

You wake up early in the day, get outside, see sunlight.

Do that again in the afternoon or around evening,

10 to 30 minutes, depending on how bright it is outside.

Artificial lights throughout the day,

or if you want to be awake and you wake up early

and there's no sunlight outside,

you can of course turn on artificial lights

if you want to be awake but basically you want

as much bright light, ideally from sunlight,

coming in through your eyes throughout the day.

And then in the evening,

you want as little bright light coming in through your eyes.

I've said this over and over and over again on this podcast.

There's always a lot of negotiations,

but I want to make a few things clear.

Try not to wear sunglasses if you can do it safely.

Fine to wear eye glasses or contacts.

That's not going be a problem.

The light viewing that you do and the avoidance of light

at night set the fundamental layer of your time perception.

One of the best ways to disrupt your perception of time

in the ways that we're going to talk about

in the subsequent portions of the podcast

is to disrupt your circadian clock

and that is not a good thing

for a number of different reasons.

There are other ways

to so-called entrain your circadian clock.

One of the best ways to do that is to engage

in physical activity at fairly regular times of day.

You don't have to do it every day

but if you're going to exercise,

try and exercise at a fairly consistent time of day.

Probably better to exercise than to not exercise,

even if you have to move that time of day,

but light activity and, we'll talk about the third

in a minute, food, are the major ways

that you entrain your internal perception of time

to the external events of the world,

meaning the turning of the Earth

and therefore the exposure to sunlight or not.

So in addition to sunlight viewing in the morning

and throughout the day and avoiding bright light

at night of any kind, not just blue light,

trying to get your activity,

your exercise at fairly regular,

within plus or minus two hours, from each day to the next

is going to have a very positive effect

on so-called circadian entrainment,

and also eating at fairly regular times.

However, this is exciting.

The data mainly point to the fact that you need to eat

within more or less the same time window each day,

not that you always need to eat your meals

at exactly the same time.

So you don't necessarily have to eat lunch at noon

and a snack at four and dinner at eight

in order to keep your circadian entrainment

aligned or sharp.

You could for instance have a small snack at noon

and then eat at two and then have dinner at six

and then a small snack at eight.

It doesn't so much matter when the exact meals fall

so much as that they fall more or less

within a consistent period or phase of each 24-hour cycle.

What happens when this circadian clock

starts getting disrupted?

I mean, this is after all an episode about time perception.

It's not an episode about circadian rhythms and entrainment.

Well, there's a classic study by Aschoff done in 1985

that's now been repeated many times

where they had people go into environments

where they didn't have clocks and they didn't have windows

and they didn't have watches

and they were sometimes even in constant dark

or constant light, and they evaluated

how well people perceive the passage of time

on shorter timescales

and what they found was really interesting.

What they found is that people underestimate

how long they were in these isolated environments.

So after 42 days or so, they'd ask people

how long do you think you've been in here?

And people would say 28 days or 36 days.

They generally underestimated how long they had been

in this very odd environment with no clocks

or watches or exposure to sunlight

or regular rhythms of artificial light.

In addition, they found that their perception

of shorter time intervals was also really disrupted.

So if they ask them to measure off two minutes,

normally people are pretty good

at measuring off two minutes.

People come within, you know, 5 to 15 seconds at most.

If you'd kind of have to sit there and just wait,

you have a pretty good idea of when two minutes is up.

You say two minutes is up.

Well, when people's circadian clocks

or circadian entrainment, I should say, was disrupted,

their perception of time measurement on shorter timescales

of minutes or even seconds was greatly disrupted.

And as we'll see in a couple of minutes,

that actually causes great problems

for how you contend with work,

how you contend with challenges of different kinds.

You want your circadian entrainment to be pretty locked in

or pretty entrained to the outside light-dark cycle

so that your perception of time

on shorter time intervals can be precise

because the ability to perceive time accurately

for the given task or given thing

that you're involved in turns out

to be one of the most fundamental ways that predicts

how well or poorly you perform that thing or task.

So we've talked about circannual entrainment,

the matching of the cells and tissues and organs of our body

to the 365-day journey that the Earth takes

around the sun each year

and we talked about circadian entrainment,

the way that the 24-hour genetic and protein clocks

of each and every one of our cells is matched

to the rotation of the Earth on its axis

and the exposure or lack of exposure to the sun

because of that rotation on its axis.

Next I'd like to talk about so-called ultradian entrainment.

Ultradian rhythms are rhythms of about 90 minutes or so

and all of our existence is broken up

into these 90-minute ultradian cycles.

When you go to sleep at night,

whether or not you sleep six hours or four hours

or eight hours or 10 hours,

that entire period of sleep is broken up

into these 90-minute ultradian cycles.

Early in the night, you tend to have more slow-wave sleep.

Later in the night, you tend to have more REM sleep.

But nonetheless, your sleep is broken up

into these 90-minute cycles.

However, when you wake up in the morning,

many of the things that you do are governed

by these ultradian rhythms.

For instance, if you were to work,

meaning do math or try and learn a language

or do physical work of any kind or work out,

the 90-minute time block seems to be the one

in which the brain can enter a state of focus

and alertness and do hard work and focus, focus, focus

and then at about 90 minutes, there's a significant drop

in your ability to engage in this mental or physical work.

Now, everybody from, you know, the self-help literature

to the business literature to the pop psychology literature

has tried to leverage these ultradian cycles

by saying if you're going to do something hard

and you want to focus on it, limit it to 90 minutes or less.

And I am one of those people

who's also joined that conversation

and indeed I use 90-minute work cycles,

and I think they are extremely powerful.

One should never expect

that you're going to drop immediately

into a state of high focus at the beginning

and then remain there for 90 minutes.

We all struggle to varying degrees to achieve focus

and motivation and drive within those 90-minute cycles.

But it is true, meaning there is ample literature

to support the idea that after about 90 minutes,

we tend to go into a state of less ability to focus.

So while this isn't time perception per se,

it is again an example of entrainment.

What are we entraining to, right?

Just because we can focus for 90 minutes

and then not so well at 100 minutes or 120 minutes,

what are we entraining to?

Well, what you're entraining to is the release

of particular neurochemicals,

in this case, acetylcholine and dopamine

that allow your brain to focus

for particular periods of time, 90 minutes or so,

and after about 90 minutes or so,

the amount of those chemicals that can be released

tends to drop very low,

which is why your ability to focus becomes diminished.

If one would like to explore more about the kind of backbone

and basis of these ultradian rhythms,

it goes by a different name.

This was originally called the basic rest-activity cycle.

This was proposed many years ago by Nathaniel Kleitman.

It was established to be true

within sleep states as I mentioned before.

Then it was debated for a long time

whether or not these 90-minute cycles also control

our ability to focus and perform work in wakeful states

and it turns out that they do.

Now there's a lot of literature to support that.

I always get the question how do you know

when the 90 minute cycle begins?

In other words, let's say you wake up at 8 AM

and you just finished a 90-minute sleep cycle.

Does that mean that your next 90-minute cycle

where you could do work begins right at 8:01?

No, the interesting thing

about these basic rest-activity cycles,

these ultradian rhythms,

is that you can initiate them whenever you want.

This is not like a circadian rhythm

which is a hardwired unerring signal of 24 hours.

The ultradian rhythms that occur

during sleep are hardwired, unerring.

You don't get the option of making your sleep cycles

120 minutes or five minutes.

You don't get that option.

But if you decide that you want to apply ultradian rhythms

to work and performance, you can set a clock

and decide, okay, now the focus begins.

Now the work begins and this 90-minute cycle is the period

in which I'm going to do work.

And I actually do this, you know,

mid morning and sometimes twice a day,

I do a 90-minute cycle where I limit all distraction

as much as possible, put away my phone,

often turn off the internet as well.

I talked about this in an episode

on kind of an optimal workday, at least for me,

just to give an example of how this might work.

But I want to emphasize again

that these ultradian rhythms are ones that you set.

So you decide I'm going to work for 90 minutes.

What you can't negotiate, however,

is that at about 100 minutes or 120 minutes,

no matter who you are,

you're going to see a diminishment in performance.

You're not going to focus as well.

And that's again because of the way

that these 90-minute cycles are linked to the ability

of the neurons that release acetylcholine and dopamine

and to some extent norepinephrine,

the things that give us narrow focus,

motivation, and drive, the way

that these 90-minute cycles are involved in those circuits.

After about 90 minutes,

those circuits are far less willing to engage

and therefore it's much harder to continue

to focus to a high degree.

Some people like to do multiple 90-minute cycles

per day of focus.

In that case, you need to separate them out.

You can't do one 90-minute cycle,

then go right into another 90-minute cycle,

then another 90-minutes cycle.

You can't cheat these circuits related to acetylcholine

and dopamine and norepinephrine unfortunately.

I suggest that people do no more than three

and ideally it would be two

or just one of these 90-minute cycles.

Why did I say ideally? Well, they are very taxing.

You are in a very narrow tunnel of focus.

So for me, I can do one mid morning.

I can probably do another one in the afternoon.

This is not the kind of work that's like checking email

or text messaging or social media.

This is very focused hard work,

working on hard problems of various kinds,

and this will be different for everybody.

So I recommend that they be spaced

by at least two to four hours

and most people probably won't be able

to handle more than two per day.

There are probably some mutants out there

that could do three or four, but that's exceedingly rare.

I think even one a day is going to feel

like a significant mental investment,

and afterwards you're going to feel pretty taxed.

So now we've talked about circannual,

circadian, and ultradian rhythms,

but we haven't really talked about time perception per se.

We've mainly talked

about the subconscious slow oscillatory ways

in which we are entrained or matched to the year

or to the day and these ultradian cycles

that we can impose on our work

and that we can leverage toward more focus if we like.

But what about the actual perception of time?

What actually controls how fast

or how slowly we perceive time going by?

There are basically three forms of time perception

that we should all be aware of.

One is our perception of the passage of time in the present,

how quickly or slowly things seem to be happening for us.

This is kind of like an interval timer ticking off time.

Tick, tick, tick, tick, tick, tick.

It's either fine-slicing like that,

or tick, tick, tick.

We have interval timers.

I'll discuss the basis of those interval timers.

We also engage in what's called prospective timing

which is like a stopwatch measuring off things

as they go forward.

That might sound a little bit like what I just described

but it's actually a little bit different.

For instance, if I told you to start measuring off

a two-minute time interval into the future,

you could do that pretty well.

But if I told you you had to measure

a five-minute time interval into the future

and you couldn't use any clocks or watches

or your phone or anything like that,

you would have to set the tick marks.

You'd have to decide how many times you were going to count off

during that five-minute time block.

There's also retrospective time

which is how you measure off time in the past.

So if I say, you know, last week,

I know you went to the park,

you did some things with friends, you know,

you went out in the evening.

How long was it between lunch

and when you went to dinner with friends?

You'd probably think, okay, well,

I remember I went to dinner at seven

and we had lunch right around two.

You're using memory to reconstruct certain sets of events

in the past and get a sense of their relative positioning

within time, okay?

So we have retrospective,

current time interval measurements,

and then prospective time measurement into the future.

The beauty of time perception in the human nervous system

is that it boils down to a couple of simple molecules

that govern whether or not we are fine-slicing time

or whether or not we are batching time in larger bins.

Those molecules go by names that maybe you've heard,

things like dopamine and norepinephrine,

neuromodulators, called neuromodulators

because they modulate, they change the way

that other neural circuits work.

Also things like serotonin.

Serotonin is released from a different site

in the brain than dopamine or epinephrin is

and has a different effect on time perception.

So just to give you an example of how things like dopamine

and serotonin can modulate our perception of time,

want to focus on a little bit of literature

that now has been done fortunately in animals and humans

and which essentially shows that the more dopamine

that's released into our brain,

the more we tend to overestimate the amount of time

that has just passed.

Let me repeat that.

The more dopamine that is released into our brain,

the more we tend to overestimate how much time has passed.

These experiments are very straight, straightforward,

excuse me, and they're very objective, which is really nice,

which is you can give people or an animal a drug

that increases the amount of dopamine

and then ask them to measure off

without any measurement device like a watch or a clock

when one minute has passed.

As dopamine levels rise in the brain,

people tend to think that the minute is up before a minute.

So they, at the 38-second mark, they'll say,

okay, I think a minute is up.

So they've overestimated how much time has passed, okay?

The higher the level of dopamine,

the more people tend to overestimate.

Now, it's also true that norepinephrine,

also called noradrenaline, plays a role

and its role is very similar to that of dopamine

and that's because norepinephrine

and dopamine are close cousins,

as some of you may recall

that they are actually manufactured from one another, okay?

So dopamine can actually make epinephrin

and norepinephrine biochemically.

There's a cascade in which dopamine can be made

into norepinephrine and epinephrin, which is remarkable.

How does having elevated levels of dopamine

and norepinephrine cause one to overestimate

how much time has passed?

Well, it does it because of the way

that it causes fine-slicing of your time bins.

So fine-slicing of time bins

is like increasing the frame rate on your camera, right?

Slow motion is achieved in movies

and elsewhere by increasing the frame rate.

So if you take a movie at 30 frames per second and watch it,

it will appear to have a certain speed, right?

'Cause those are just snapshots, 30 frames per second.

In contrast, if you took that same movie

at 4,000 frames per second, you are fine-slicing

and you're going to see every little detail

and as you play each one of those frames,

it's going to look like it moved slower, okay?

Whatever, so the kind of jump shot in basketball

that's done slowly, any slow motion

is the consequence of higher frame rate.

So dopamine and norepinephrine increase frame rate,

and as a consequence, they tend to lead us

to overestimate the amount of time that's passed.

Conversely, the neuromodulator serotonin causes people

to underestimate the amount of time that's passed.

So they've done these experiments.

They actually have done these experiments using,

in humans, with drugs that increase serotonin.

They've also done them with cannabis

which increases serotonin among other things

including the cannabinoid receptor activation.

And when people have elevated levels of 5-HT

or whether or not they've ingested cannabis,

they tend to underestimate how much time has passed.

You do the equivalent experiment.

You tell people that they have to guess

or tell you when five minutes, for instance, has passed.

Just use five minutes as an example this time.

And generally they will miss the five-minute mark.

They will think, they'll let six minutes pass

and they'll think it was five minutes

when they've underestimated how much time has passed.

And that's because serotonin

and some of the related molecules in the brain

tend to lead to slower frame rates, right?

They take the frame rate in the example I used before

from 4,000 frames per second down

to, say, 20 frames per second.

So this is very interesting.

It's interesting in terms of how pharmacology can be used

to adjust time perception but it's also interesting

in the context of that circadian rhythm.

There's some emerging evidence

that throughout the 24-hour cycle,

there are robust changes in the amount of dopamine,

norepinephrine, and serotonin that are present

in the brain and bloodstream and body

depending on time of day within the circadian cycle.

Now, I'm not talking about during sleep.

During sleep, there are definitely variations

in things like dopamine, norepinephrine, and serotonin.

I talked about that in the episodes on sleep.

Here I'm just talking about the role of these molecules

in time perception during wakefulness.

So much of the evidence points to the fact

that in the first half of the day,

approximate first half of the day,

dopamine and norepinephrine are elevated in the brain,

body, and bloodstream much more than is serotonin

and that in the second half of the day

and in particular towards evening and nighttime,

serotonin levels are going up.

I think that's fairly well-established now.

What that means based on what we just discussed

about the role of dopamine, norepinephrine, and serotonin

in setting the frame rate of time perception

is that our perception of the passage of time

will be very different in the early part of the day

and in the latter half of the day.

And there's starting to be some evidence

to support this, that early in the day,

people tend to overestimate how much time has passed

and later in the day,

they tend to underestimate how much time has passed.

And this is independent of taking any kind of substance

that would increase or decrease dopamine or serotonin.

Now, this is important in terms

of how one thinks about structuring their day,

because I know many people are thinking

about the various tasks that they need to do

throughout their day.

Many, or I should say all of the literature,

at least that I can find on productivity

and things of that sort point to the idea

that we should be doing the hardest task,

the thing that we want to do the least

or the most important task early in the day

as a kind of a psychological tool for getting it done

and feeling as if we accomplished something

and I think that's an excellent protocol, frankly,

but I'm not sure it's an excellent protocol

because of the way that we sense accomplishment

or at least it's not only an excellent protocol

because of the way that we sense accomplishment.

Another reason to move something that's very hard

into the early part of the day

is that if indeed the dopaminergic

and noradrenergic circuits are more active at that time,

we are actually in a better position cognitively

to parse that hard problem because of the way

that we are able to fine-slice our perception of time

and fine-slice all the perceptual events outside us.

So what I'm really saying is that early in the day,

you are a much more high resolution camera,

so to speak, than you are later in the day.

Now, different types of tasks and different types of things

require different frame rates

or different ways of perceiving time,

and indeed, this also lends itself to a tool

whereby for activities that involve

more kind of creative thinking that aren't as constrained

by particular answers or outcomes

and in which we need to kind of blend different aspects

of our memory, different aspects of task utilization,

in other words, for creative works, for brainstorming,

for things that are a bit more fluid, so to speak,

the more serotonergic second half of the day,

and because of the way the serotonergic second half

of the day lends itself to our time perception,

may actually be more beneficial for those sorts of tasks.

And I'll put a reference to a couple of the studies

that point to this idea

that in these higher dopaminergic states,

we are better at doing certain sorts of tasks

and in these more serotonergic states,

we're better at doing other sorts of tasks

and how the dopamine tends to be earlier in the day

and the serotonin later in the day, so to speak.

These are broad, I'm painting with broad strokes here,

but I think these lend themselves

to some really excellent tools

because I think we all understand the value

of doing something that's hard

or challenging early in the day,

but we should ask ourselves hard or challenging how?

What does that task actually really require

in terms of time perception?

Some people might appreciate some examples

of how this might work.

Basically what I'm saying is if you are doing work

that involves adhering to some rigid rules,

so math or a recipe or execution of musical scales

or physical skills or accounting

or something that requires a lot of precision

where there's a right and wrong answer and it's hard,

I would suggest that you do that

in the early part of the day because of the way

that dopamine and norepinephrine impact time perception.

You are literally better at slicing up time,

you are a higher resolution brain during those times,

and so that's going to lend itself better to events

and demands that require high resolution,

whereas in the afternoon

in this more what I'm calling serotonergic state,

that's when you're going to be better at brainstorming

and creative works where there's some flexibility

in terms of how you're batching time and perceiving time

and there isn't so much rigid oversight

of a right or wrong answer.

And as an aside to support what I said

but also to take us back

to this critical role of the circadian rhythm,

there is a lot of evidence

that when one's sleep is disrupted,

when sleep is either too short or is fragmented

or is not of high enough quality for enough days,

one of the first things to happen

is that there is a dysregulation

of these dopaminergic, noradrenergic,

and serotonergic states throughout the day.

They get kind of mish-mashed up.

It's not that they're a total mess

but they aren't as cleanly defined.

And I think this is one of the reasons why

when we haven't slept well or we haven't slept enough,

we tend to feel a little off, like we can't concentrate.

Part of that lack of concentration is due to other things

but part of that concentration could be due to the fact

that our sense of the passage of time is disrupted.

So there seems to be some value in keeping

the dopaminergic noradrenergic state kind of limited

to the early part of the day

and this serotonergic state, as we're calling it,

kind of pushed towards the second half of the day.

Now, there is a version of how dopamine and norepinephrine

can impact our perception of the passage of time

in ways that can be very disruptive or even maladaptive

and the best example that I'm aware of is trauma.

Many people who have been in car accidents

or who have experienced some other form of major trauma

do what's called overclocking.

Overclocking is when levels of dopamine and norepinephrine

increase so much during a particular event,

our level of alertness is increased so much

during a given event that we fine-slice.

In other words, the frame rate is increased so much so

that we perceive things as happening in ultra slow motion.

Now, that might not seem like a bad thing overall

but the problem with overclocking is the way

in which that information gets stamped down

into the memory system.

So the memory system, which involves areas of the brain

like the hippocampus but also the neocortex,

is basically a space-time recorder.

What do I mean by space-time recorder?

Well, your nervous system, of course,

is housed in the darkness of your skull.

It doesn't have a whole lot of information

about the outside world except light coming in

through the eyes and whatever happens to hit our ears

in terms of sound waves and skin and so forth

so it has to take all those neural signals

and it has to create a record of what happened.

Now, it doesn't create a record of everything that happened

but car accidents and trauma

and things of that sort oftentimes are stamped down

into our record of what happened.

And what gets stamped down,

what we actually mean by the phrase stamped down

is that the precise firing of the sequence of neurons

that reflected some events,

so let's say I'm in a car accident,

certain neurons are firing because of the flipping

of the car or their screams or there's blood,

or, you know, things of that sort,

all of that neural activity gets repeated

in the hippocampus and then the sequence

of the firing of those neurons is also remembered.

So it's not just that neuron one, two, three, four

fired in that sequence.

It's also that neuron one, two, three, four

fired at a particular rate.

So it would be one, two, three, four

during the actual event and then the memory is stored

as firing of those neurons as one, two, three, four, right?

If during the event, it was one, two, three, four

at that rate, the storage of the memory

is not going to be one,

two, three, four, okay?

In other words, there's both a space code, as we say,

meaning the particular neurons that fire is important,

and there's a rate code, how quickly those neurons fire

or the relative firing, the timing of the firing

of those neurons is also part of the memory.

This affords our memory system tremendous flexibility.

What it means is that you can take the same set of neurons

in the hippocampus and stamp down many, many more memories

because all you have to do is use a match

of the different rates of the different neurons

that were firing in order to set that code, right?

Otherwise, if you needed a different set of neurons

for every memory, you'd need an enormous hippocampus.

You'd need an enormous head.

So I think you get the basic idea.

Overclocking is a case in which the frame rate is so high

that a memory gets stamped down

and people have a very hard time shaking that memory

and the emotions associated with that memory.

And it's not the topic of today's conversation

but we will cover trauma in a future episode in detail,

but many of the treatments for trauma,

EMDR, nowadays there's a lot of excitement also

about ketamine therapies, exposure therapies,

you know, like cognitive behavioral therapies

involve not just trying to reduce the amount of emotion

associated with a memory, but also a deliberate speeding up

or slowing down of that memory.

In other words, trying to allow the person

who experienced the trauma to take control

of the rate of the experience in their memory,

not just whether or not the memory happened at all.

In fact, you know, one of the first things

that trauma victims learn

is that they aren't going to forget what happened.

What's eventually going to happen ideally

with good treatment is that the emotional weight

of the experience will eventually be divorced

from the memory of the experience.

And that's done again by trying to reduce

the amount of emotional activation

during the recall of that experience

and one of the best ways to do that

is to alter the rate of the memory playback.

In other words, taking that firing of neurons

that might've been one, two, three, four,

again, it would be much more complicated,

but one, two, three, four for the car crash

and getting the memory to play back at a rate

of one, two, three, four,

or even one, two, three, four,

one, two, three, four.

In other words, allowing the person

or instructing the person to take control

of the rate of the playback, and in that way,

there seems to be still yet unknown mechanism

by which people can uncouple some of the emotional weight

that's associated with that memory.

So overclocking is a kind of extreme example

of where the dopaminergic and the neurogenetic system

is ramped up so high that people have this,

unfortunately, what seems like indelible mark

in their brain of a particular event.

But again, trauma treatment is designed

to uncouple the emotional load of that event.

Some of you are probably saying why dopamine during trauma?

I thought dopamine was the feel-good molecule.

Well, in reality,

dopamine is not necessarily a molecule of reward.

It's a molecule of motivation, pursuit, and drive.

And because of the close relationship

between dopamine and norepinephrine,

oftentimes they are co-released.

So whether or not dopamine is released during car crashes

or other forms of trauma, we don't know

but what we do know is that both the dopamine system

and noradrenergic system, when we say noradrenergic,

we mean norepinephrine, those systems are greatly increased

anytime there's a heightened state of arousal.

And arousal can have negative valence,

like meaning associated with an event that we really hate,

that we would prefer not to be involved in,

or can positive valence, but dopamine and norepinephrine

are kind of the common hallmark

of all things of elevated arousal.

And so that's why we see evidence for dopamine

being associated with these changes in time perception

both for positive events and for negative events.

There's a very interesting relationship between arousal,

dopamine, time perception, and blinking,

and this is all supported by a really interesting paper,

first author, Terhune is the last name, T-E-R-H-U-N-E.

It's published in "Current Biology."

Cell Press journal. Excellent journal.

The title of the paper is

"Time Dilates After Spontaneous Blinking."

So heightened states of arousal are associated

with heightened levels of dopamine.

You now know that dopamine leads

to a kind of fine-slicing of time

and one of the ways that we fine-slice time is by blinking.

You know, we think of blinking as just a thing

to lubricate our eyes or to limit

the amount of light coming into our eyes,

but it's a shutter on our experience.

So much of the information coming into the brain

through our eyes impacts our attention.

I've said it before on this podcast,

that cognitive attention follows visual attention,

at least for sighted individuals.

Well, it turns out that dopamine

and increases in dopamine are associated

with increases in spontaneous blink rate.

So the more aroused we are, the more awake we are,

there are a number of effects.

Pupils dilate, heart rate increases, et cetera,

but also blink rate increases.

And every time we blink, this study cleanly shows,

we shift our perception of time, leading to,

as I mentioned before, overestimations of time.

So it seems as though in some way,

blink rate is actually related to frame rate.

So this is very, very interesting

and the way that you could think about leveraging this

would be if you wanted to actually slow down

your perception of time, you would blink less.

And if you want to speed up your perception of time,

you would blink more.

Now, you'd have to think of a scenario

in which that would be useful to you.

Obviously if you're going to blink,

you're going to miss things as well.

But I think it's a very interesting parameter

of our visual attention as it relates to time perception,

because what it really speaks to

is that these neuromodulators like dopamine

or serotonin that adjust frame rate,

they're not doing it through some magical mechanism.

In fact, there's no single brain area

that we can say controls time perception.

I haven't said today, oh, you know, it's the striatum.

Well, it involves the striatum but I'm not going to say,

for instance, oh, it's the cerebellum.

The cerebellum is definitely involved

in timing of movement, something for a future podcast,

but time perception is what we call

a distributed phenomenon.

It's a network of areas in the brain working together.

But dopamine and the way that it relates

to the shuttering of your eyes

seems to be controlling the frame rate on your experience.

Numerous times on this podcast,

I've talked about cold exposure

and nowadays there's a lot of interest

in things like cold showers, ice baths,

immersion in cold water tanks

and lakes and oceans and things of that sort.

There are a lot of different positive effects

of cold exposure provided it's done properly.

It can lead to increases in metabolism, brown fat stores,

which are the good fat stores that you want.

They're sort of like a furnace

that allow you to heat yourself up,

stay warm in cold environments, to reduce inflammation,

to increase resilience and so forth.

There's a study published

in the "European Journal of Physiology"

showing that cold exposure can increase

our baseline levels of dopamine robustly, 2.5x,

and it's a long-lasting increase in dopamine

and appears to be a healthy one,

meaning it doesn't seem to be addictive.

I'm sure there are some people out there addicted

to ice baths, but, you know, when you think about the range

of dopamine-inducing behaviors that are addictive,

it seems to be more on the health-promoting side.

What's interesting is that because cold water exposure

increases dopamine, it will also change

your perception of time and if you've ever done

one of these cold water exposures, you've experienced this.

You've experienced getting in and feeling like, wow,

making it three minutes is a really, really long time,

and you are fine-slicing time.

Your frame rate is going up.

Part of that, just at a kind of a coarse level

is you're thinking, this is painful.

I don't like this. I want to get out, right?

But part of it is also that your dopamine levels

are going up very quickly and therefore your perception

of that discomfort is also being fine-sliced.

And so you could leverage a tool, for instance,

where you try and entrain your thinking

to something other than your immediate experience, right?

This is a kind of a controversy, if you will,

in the cold exposure world.

The question is do you try and lean into the experience

and really feel it, or do you try and distract yourself,

you know, sing a song or count off,

you know, from one to a hundred.

Just know that whatever tactic you use

to get through the cold exposure

that the dopamine level that's now increased

in your system is going to cause you to fine-slice

or experience that at slow motion.

So a minute is going to seem like a lot longer

than a minute in reality.

So you could, for instance,

decide to pay attention to some external cue.

Maybe it's a metronome that ticks once every 10 seconds.

You could decide to think about something else.

You could decide to sing a song in your head

or sing a song out loud.

All of that will divorce you from the sensation

that you experience somewhat,

but more so it will divorce you

from the perception of your experience as governed

by that dopamine increase in frame rate.

If that isn't clear, just know this.

When you're in the ice bath, your dopamine levels are high.

When your dopamine levels are high,

your experience of the discomfort

of that ice bath is at higher resolution.

Now, up until now, I've been talking about how dopamine,

and to some extent, serotonin

can differentially impact your perception of how fast

or how slowly things are happening in the moment.

But remember, we have prospective time,

we have our experience of time in the moment,

and we have retrospective time

and there are beautiful studies that have showed

that the dopaminergic state changes the way

not just that we experience things now,

but that it changes the way in which we remember things

in the past and the rate at which those things occurred.

And those are in opposite direction.

So to make this very simple,

if something that you experience is fun or varied,

meaning it has a lot of different components in it

and is, in other words, is associated

with an increase in dopamine in your brain,

you will experience that as going by very fast.

Now, this is different than the ice bath

which I just said you experienced as going by very slowly,

but here I'm talking about something that's fun

and varied that you really like

and you feel like it goes by very, very fast.

Imagine an amazing day for a kid at an amusement park.

They can do a ton of things. It's all new.

They're very excited and they'll feel

like it goes by very fast,

but later they will remember that experience

as being very long,

that it was a long day full of many, many events.

And so there's this paradoxical relationship

between how we perceive fun, exciting, varied events

in the present and how we remember them in the past.

For those of you who've gone on vacation,

if you've had an amazing day on vacation, it'll seem like,

or an amazing vacation overall,

it will seem like it goes by very fast.

The last day of vacation, you sort of go, whoa,

it went by so fast 'cause there's so much happening.

But in memory six to eight months later, you remember, wow,

that just went, you know, that was a long, long thing.

We had this. Then we had that.

Then we did this. Then we had that.

It tends to spool out in a longer memory

than the actual experience.

Conversely, if you are bored with something

or it's something you really don't like,

it's going to seem like it takes a long time

to go through that experience in the moment,

but retroactively, looking back,

it will seem like that moment was very short.

So the other day I was waiting in the waiting room

for the dentist, it was pretty boring.

I was just kind of sitting there.

There wasn't much going on.

And it did seem like it was going on an awfully long time,

but indeed, looking back, it just seems like, okay,

I sat in that room, not much happened.

And so it seems like a very short time bin.

This seems to be an efficiency

of how the brain stores information,

dopamine being associated, of course,

with fun and varied experiences

and low dopamine being associated

with kind of empty, boring,

or what at the time seem like long experiences.

And this whole thing has been stamped down

into the scientific literature by those earlier experiments

where they take human beings and isolate them

in certain environments.

You know, take away all their clocks and watches and cues

and about what time of day it is

and what time of night it is and allow people to have a life

where they can either read and work and do things

or where they have very little to do.

When people are isolated in very boring environments

and they don't have access to time cues, time dilates.

They tend to assume that time has gone on very, very long.

And so the reason I bring this up is we aren't just driven

by these circadian clocks and these circannual clocks

and these ultradian clocks.

We are driven by these timers that vary

depending on our level of excitement

and they vary depending on our level of excitement

because of these neuromodulators, dopamine and serotonin.

So the way I like to think about it

is that you have two clocks, two stopwatches.

One is a dopaminergic stopwatch

that fine-slices really closely.

It's like, counts off milliseconds and it's grabbing a movie

of your experience at very high resolution.

And in the other hand, you have a stopwatch

that's gathering big time bins,

big ticks along the, you know,

the hand is moving at bigger intervals,

you know, marking off time.

And depending on whether or not you're excited

or whether or not you're bored,

you're using different stopwatches on time

and therefore you're perceiving your experience differently.

One very interesting aspect to the way

that neuromodulators like dopamine and novelty interact

with time perception and memory

is how we perceive our relationship to places and people.

So really interesting literature showing

that the more novel experiences we have in a place,

the more we feel we know that place, obviously,

but the longer we feel we've been there.

So here's the kind of gedanken or thought experiment

that illustrates what's in the literature.

Let's say I were to move to New York City.

I happen to really like New York City.

I've never lived there, but let's say I lived there.

I lived in a given apartment for a year

and I would have a number of different experiences

in this mental experiment.

Let's say I had 100 different exciting and new experiences.

I would at the end of that year feel as if I lived there

a certain period of time, one year.

I would actually know I lived there one year.

If however I lived in three different places

in New York City and I met three times as many people

and I had three times as many novel experiences,

I would actually feel as if I had been there much longer

than had I only lived in one location.

This is also true for social interactions.

When we move to multiple

or several novel environments with somebody else,

we tend to feel as if we know that person much better

and that they know us much better.

Now, of course, we get the opportunity to interact

with those people in different contexts

and so indeed we do get the opportunity to see them,

for instance, at the coffee shop, how they order coffee.

You maybe go to a sports event, how they act there.

Maybe how they interact with your family.

You're getting a sense of them in different contexts.

That's certainly playing a role,

but it seems as if the more novelty you experience

with somebody, not only the more familiar they are to you,

but the more time you feel you've spent with them,

even though the total amount of time

can be exactly the same.

And so that's a very interesting aspect

of how our perception of time and these neuromodulators

and novelty can shape the way not just that we perceive

a given event in our world, but how we relate

to a place or relate to a person.

So we've talked a lot about the different neurochemicals

and how those neurochemicals can influence

our perception of time.

We haven't talked a lot about the neural circuits

and the various areas of the brain that underlie this.

I do want to touch on that

by highlighting a really wonderful study.

This was a study published in "Neuron,"

also a Cell Press journal, excellent journal.

The title of the paper is "Behavioral, Physiological,

and Neural Signatures of Surprise

During Naturalistic Sports Viewing."

This experiment is really cool.

They did brain imaging on individuals

who are watching basketball games.

These were basketball games

that actually took place that were recorded

and the subjects watching these basketball games

in some cases, not all, had some interest

in who would win or lose, and in some cases, not all,

the subjects in these studies had some prior knowledge

of which team they thought was better,

which team was likely to win or not likely to win.

The basic findings of the study

were that they could measure surprise

by the release of dopamine in two areas of the brain,

part of what are called, is called, excuse me,

the mesolimbic reward pathway.

So the two areas of the brain that are important here

are the nucleus accumbens and the VTA,

the ventral tegmental area.

These are areas that release dopamine

as kind of a token of reward

any time something is surprising

or a positive expectation is met, okay?

So if I predict that my team dribbling down court

is going to score on this drive

and they get the ball in the basket,

a little bit of dopamine is released.

These two brain areas light up

in the functional imaging so-called FSRI,

functional magnetic resonance imaging

that they used in this study.

What's really interesting about this study

is not just that dopamine was released any time

that something the subject wanted to see happened, right,

any time they wanted to see their team score, they scored,

but also during surprise.

So if they thought for instance,

and they would hit a button to predict

that their team was going to score in this particular drive

and they didn't, well, then dopamine could also be released

in response to that surprise.

So this speaks again to dopamine being something

that's important not just for positive events,

but for unexpected events.

Now, that's all very interesting and speaks to the fact

that dopamine is a kind of flexible currency in the brain.

It's doled out, if you will, or released

when something that one hopes will happen happens

and it's released when there's a surprise,

even if it's a kind of a negative surprise.

It's not something that the subject wanted to happen.

But the more interesting thing

is how that relates to time perception.

What they found was regardless of what caused

the dopamine release, the frequency of dopamine release

predicted how the subjects parsed the time bins

of the game they were watching.

What do I mean by that?

Well, when you watch a basketball game

or you watch anything, children playing or talking

to your spouse or whatever, you're batching time.

How are you batching time?

Well, you could batch a meal by the, I don't know,

the appetizer, the main course, and the dessert,

but it turns out that's not what you're doing.

You're batching time according

to the frequency of dopamine pulses,

the frequency of dopamine release.

And that's what they saw in this study.

If they evaluated people's perceptions

of the passage of time,

what they found is that that matched

not whether or not the, you know,

it was a particular time point in the game,

not whether or not their team was going down court

or running back up court to play defense,

but the dopamine released served as markers

which would predict the frame rate

of their perception of the experience.

And if that sounds complicated, what I mean is how often

and when you release dopamine is actually setting

the frame rate on the entire perception of everything,

not just for positive events or negative events.

So what this means is as you're going through life,

dopamine and the release of dopamine is saying that's over

and now you're in a new phase of your life

even if it's very short, right?

So if I get up in the morning

and I really need a cup of coffee, as you probably all know,

I wait 90 minutes to 120 minutes before I drink my coffee,

but then I get my coffee

and surely there's a dopamine hit there, I promise you,

I actually am starting to carve up my day

according to dopamine hits.

Consciously or subconsciously,

I'm actually carving up my experience

according to when I'm getting dopamine throughout my day.

This governance over our perception of time

that dopamine has points to a very clear,

very actionable, and very powerful tool.

And that is a tool that many people have talked about before

which are habits.

People have discussed habits in a variety of contexts

but in the context of dopamine reward

and time perception, what this means

is that placing specific habitual routines

at particular intervals throughout your day

is a very, not just convenient,

but a very good way to incorporate the dopamine system

so that you divide your day into a series

of what I would call functional units.

What would this look like?

It would mean waking up and having one specific habit

that you always engage in that causes a release of dopamine.

You can say, well, great.

That'll make me feel good. And I would agree.

Dopamine released generally makes us feel motivated

But it would have an additional effect of marking

that time of day as the beginning of a particular time bin.

Then inserting another habit, perhaps the beginning of,

I don't know, your breakfast or something,

but recognizing that that's a habit

and being fairly habitual, you don't have to be, you know,

obsessively precise about the timing,

but that regular sequencing of things

is going to lead not just to dopamine release

as it relates to reward and motivation and feeling good,

but it actually becomes the way

in which we carve up our entire experience of our day.

And this is almost a circular argument.

You could say, well, of course, you know,

I do one thing, then I do the next,

then I do the next, and that's how I perceive my day.

That's my day. It's my list.

It's my to-do list, et cetera.

But what I'm saying is that on the basis of this study,

I should mention the first author, his last name is Antony.

It was Antony et al. It was published in 2020.

The study on basketball viewing, what it points to

is that by engaging in specific habits

that we know we can perform well,

we are actually setting the frame rate on our day.

And so I think there will soon come a time

where human beings are not just thinking of, okay,

my morning routine and my afternoon routine,

I think that can be useful, and in fact,

I used or mentioned a structure

of that sort earlier in the episode,

but rather thinking about what's actually going on

at the level of our biology,

which is that dopamine is marking time.

Habits are a very clear way

in which we can invoke dopamine release

and therefore provide time markers, and what this means

is that, for instance, during your morning,

you might insert habit one and habit two

at, say, I don't know, 8 AM and 10 AM,

and in doing that, that marks an epoch,

a little batch of time in your morning routine

that's distinct from the second half of your morning.

In other words, habits serve as flankers

or markers for the passage of your day.

Now, if that seems kind of hyper-neurotic

or why would I want to structure my life like that,

I would say that many people would do well

to structure their life like that and to utilize habits

not just for the sake of what you do during the habit,

but because of the fact that the habits serve as a marker

because of the way they can evoke dopamine release.

And in doing that, you are able to segment your day

into a bunch of smaller, if you want them to be smaller,

or larger functional units.

If anyone wants to experiment with this,

the Huberman Lab Podcast puts out a newsletter.

It's called the Neural Network Newsletter.

You can sign up for it at hubermanlab.com.

We put it out each month.

You can see the previous newsletters.

There's zero cost. We have our privacy statement there.

We don't share your email or anything.

And there you'll find the, you know,

12 steps to improving sleep was the first one.

There's another, the second newsletter

was all about neuroplasticity

and using scientific literature

to improve learning and teaching, and in the next newsletter

I intend to include an example protocol

of how one could use habits and the relationship

between habits and dopamine, dopamine and time perception,

to structure your day according to performance

of particular types of tasks.

Today we covered a lot about time perception.

We certainly didn't cover everything about time perception

but we covered things like entrainment,

the role of dopamine, habits and various routines

that can adjust your sense of time

for sake of particular goals.

If you're interested in learning more about time perception,

I'd like to point you to a really excellent book

called "Your Brain Is a Time Machine:

"The Neuroscience and Physics of Time."

The book was written by Professor Dr. Dean Buonomano

who's a professor at UCLA and a world expert

in the neuroscience and physics of time.

I do hope to get Dean on the podcast

in the not too distant future.

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[bright guitar music]