March 27, 2023 • 30 mins
When he was a child, Eagleman fell off a roof and time seemed to run in slow motion. When he became a neuroscientist, he grew curious about the experience and collected hundreds of similar stories from others. But is it true that your brain can actually see in slow motion, like Neo in the Matrix? And how would you test that? Hear how he dropped volunteers from a tower to put the science to the test, and what the answer reveals about our perception, memory, and experience of the world.
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Speaker 1 (00:04):
So you always hear people say things like I got
in a car accident and the whole thing seemed to
happen in slow motion. I saw the hood crumple and
the rear view mirror fall off, and I was watching
the other driver's expression. And it's the same thing with
gunfights or skiing accidents or motorcycle crashes. But from a
(00:26):
neuroscience perspective, is it true that time slows down? And
how could you test that? And why does your drive
to work on the first day seemed to take a
long time, but after a while it takes no time
at all. And why do the years seem to go
by faster as we get older? Welcome to inner Cosmos
(00:47):
with me, David Eagleman. I'm a neuroscientist and an author
at Stanford University, and I've spent my whole career studying
the intersection between how the rain works and how we
experienced life. The first time I experienced time slowing down,
(01:11):
I was eight years old. It was a Saturday, and
my brother and I left the house to find something
to do, and on the way out the door, our
father warned us not to go near the house under construction,
and so we told him we wouldn't, and being children,
we of course went straight to the house under construction.
So we poked around like kids do, and eventually we
(01:34):
found a ladder and we went up onto the roof,
and from there one could enjoy a wonderful view of
the mountains of Albuquerque, New Mexico. And my brother wandered
off to explore some other part of the roof, and
I stepped forward to stand at the edge. Now I
didn't know what tar paper was. I didn't know that
(01:55):
it was stiff and that it extended past the edge
of the roof on center construction. So when I thought
I was stepping to the roof's edge, I was actually
stepping on the tar paper, and I began to fall.
As I fell, I thought about grabbing for the roof's edge,
(02:18):
but some part of my brain recognized I was too
late for that. So I found myself in a spread
eagle position, looking way down to the red brick floor below,
And as I fell towards what was likely to be
my death, I was thinking calmly about how similar my
(02:39):
fall was to that scene in Alice in Wonderland when
she falls down the rabbit hole. It was totally calm
and peaceful. I didn't have any fear or panic. I
was just thinking about a moment from a children's story.
So it won't surprise you that I lived. But it
(03:01):
did surprise my parents and the emergency room physicians because
I'd fallen twelve feet and landed on my face, on
my nose, and I'd lost consciousness and a lot of blood,
and I'd shattered all the cartilage in my nose. But
what stayed with me wasn't anything about that or the pain.
It was a fascination with what had happened. So fast
(03:24):
forward seven years later, I'm in high school physics, and
I learned the formula D equals one half at squared,
and that allows me to calculate how long the fall took.
And I realized the fall had only taken point six
of a second. What that couldn't be right. It seemed
to have taken so much longer. So fast forward some
(03:46):
more years and I become a neuroscientist, and my graduate
thesis was a large computational model of a chunk of
brain tissue and the signaling that happens in there. But
the experience of my falls mysteriously long duration never left me.
So once I became faculty, I started looking into this
and I started collecting stories from people. So I'm going
(04:10):
to start with one from a police officer. So one
morning he got radio that two suspects were heading his
way in a police car chase and that he should
position his car in the middle of the road to
stop them. So he does that, and he sees the
car coming in from the distance, and he stands in
(04:31):
the middle of the street and raises his hand for
them to stop, but they just keep coming, and they're
coming right at him. So he draws his revolver and
he points it at the driver with the intention of
shooting him through the windshield. And the car is so close,
and for him, it seemed like time went into slow motion.
(04:52):
And here's how he reports his thoughts. Now, wait a second,
these are three fifty seven hollow points, and they should
go right through the glass. But since the glass is angled,
what if it ricochets off the glass and kills someone
on the second story of that house over there. Anyway,
he suddenly realizes that the car is almost on top
(05:14):
of him, so he jumps out of the way, and
at the same motion he squeezes off around at the
driver's door, bang, and as the car goes by, he
then pulls off a second round bang, and then as
the car is almost all the way past him, he
feels his finger pull off the third shot bang, and
he assumes that he'd fired at the rear window, but
(05:38):
he noticed that the glass hadn't broken, and so he
starts to worry that maybe he'd missed, and maybe he'd
shot a bystander down the road, and so he immediately
is thinking about how his career might be over, And
so his partner comes running up to him, and in
the conversation afterwards, he realizes that his partner had witnessed
(06:01):
a very different event. His partner said that the entire
incident from the car approaching to when it went by,
took maybe all of three seconds. And his partner said
that the three shots sounded like bang bay bang, but
it didn't feel that way to the officer firing the shots.
(06:22):
It seemed like he had taken a lot of time
to think about ricocheting, about people sitting in their living rooms,
about whether the shot had hit the back window, about
whether the shot would possibly hit a guy in a
bar or some distance away, and in his mind the
shots went bang bang bang, as though everything were happening
(06:45):
at a much slower pace. So how is it that
a bang bang bang from one guy is perceived by
someone else's bang bay bang? How does that happen? Now?
Here's another story from a doctor who got in a
motorcycle accident. So he's going forty five miles an hour
down the road. A car pulls out of the driveway
(07:06):
and he comes off his bike and he hits the
road and he rolls four or five times, and time
appears to slow down, and he feels like he's rolling forever.
So after he rolls twice, he thinks, gad, when am
I ever going to stop rolling? So it seemed like
(07:26):
time had slowed down for him. And when he was
thinking about this later, he estimated it would take him
about two and a half or three seconds to think
that particular thought, and so that provided him with a
timescale of the amount of time that a single roll
seemed to take. So when he calculated this later in retrospect,
(07:48):
he determined that the whole event seemed to have taken
about fifteen seconds, but it couldn't have taken any longer
than five or Another report I collected was from a
mother who saw her three year old child fall into
the shallow part of a lake at a little distance
away at a park. So, like any parent would, she
(08:08):
started immediately sprinting towards the lake, but it seemed to
take forever to reach there. Now, her child was fine,
and in fact it didn't take her that long, but
she was haunted by remembering her thoughts during what seemed
like a painfully slow process of reaching her child. And
this impression that time runs slowly is not an uncommon occurrence.
(08:33):
Other people I interviewed describe things like car accidents where
they watched the whole event unfold slowly with a kind
of inevitability, the car sliding towards them impacts and the
door crushes and so on, Or the victim of a
mugging describing the way that the mugger reaches into his
(08:54):
jacket to draw a weapon, or a person who's been
in an accident with a skateboard going towards the parked car.
All of these things involve very short time windows that
for some reason seem very lengthy, and these people, like me,
reported that the sensation of time had seemed to proceed
(09:15):
more slowly than normal, And so these reports made it
seem possible to me that the brain has a capacity
to operate at a higher frame rate, which is how
filming slow motion in the movies works. You capture information
at a higher frame rate and then you play it
back at normal speed. But what if there was another
(09:37):
possibility here? What if, for example, it's a trick of memory,
such that you're laying down denser memories and when you
read it back out, your brain's only conclusion is, well,
if I have that much memory, that must correspond to
five seconds, when in fact it only lasted one second.
So I wanted to understand what was happening here the brain,
(10:00):
So I scoured the neuroscience literature, but it turned out
no one had ever put the question of slow motion
perception to the test. Why not, Well, it's because it
would require placing volunteer subjects in life threatening situations, which
is not a clear path to tenure for an academic.
(10:21):
But without a rigorous scientific experiment, I realized it was
difficult to know how to interpret these experiences, including my own,
from a neuroscience point of view, and I was obsessed
with figuring out how to test this first I needed
(10:44):
something scary, so I packed up stop watches and pads
of paper, and I took all the members of my
laboratory to Astro World, which was the local amusement park,
and we set out to find the most terrifying roller coaster.
(11:04):
We had a fantastic time as a group, and we
did a lot of laughing, but at the end of
the day we couldn't find anything frightening enough to give
us the impression that time had moved in slow motion.
We needed something more terrifying, so we kept looking, and
three weeks later, and three hundred miles away, we found it.
(11:28):
SCAD diving Now SCAB stands for suspended catch air device.
Imagine a huge metal tower. It's one hundred and fifty
feet tall. It's kind of like a poor man's Eiffel Tower,
and you step on a small platform that pulls you
(11:50):
up like a small elevator, and you find yourself standing
at the very top of the tower, looking down on
the city. Now, you put a big leather harness on
your back, and then you click the front of your
harness into a bolet hook. You position yourself so that
you're hanging from the hook, cradled in that piece of
(12:12):
leather dangling in the air with a net one hundred
and fifty feet below you, and then the hook releases
and you are in free fall backwards, looking at the sky,
falling backwards, not even able to see where the net
(12:34):
is or how much time you have left. When you
finally hit the net below, you're going seventy miles an hour,
and the net catches you softly and you finally breathe again.
This was sufficiently scary. Now I'm going to get back
to the experiment in just a moment, but first I
(12:57):
want to specify that this isn't your typical in the
lab science experiments. So I had to do a lot
of convincing to get the university to sign off. It
took me seven months, but we were finally ready. So
before we tested anyone, I took the plunge myself three
times in a row, and I can tell you that
(13:17):
each time was equally terrifying as the previous. There's no
getting used to falling backwards from a height like that.
It goes against every Darwinian instinct that you have in
terms of staying alive. But back to the question, we've
now found something sufficiently scary. How do we do the
(13:37):
experiment to see if people are overclocking or having a
faster frame rate in the moment. So in my lab
we engineered a wristband that we called the eagle eye,
or more technically the perceptual chronometer, which is just a
fancy way of saying something that can measure the speed
(13:59):
of your perception, in other words, how fast you're taking
in information from the world. So picture this. It's like
a watch with a big face, and it has a
rectangular screen of small LED lights. So we can display
a number on it, let's say the number twenty seven,
by turning on the LEDs that make that number. But
(14:23):
here's the trick. We now switch the lights so that
in the next moment, all the LEDs that are on
turn off, and all the ones off turn on, So
that still shows you a twenty seven. But now it's
like a negative photograph where the background is lit but
the number isn't, so you can still easily read that
as twenty seven. Now what we do is we alternate
(14:46):
the positive and negative images rapidly, so all the lights
are blinking on and off and at a fast pace.
You can still easily see that the number being displayed
is twenty seven, But if we make it just a
little bit faster than that, you can't see any number
at all, because the speed is such that the positive
and negative images fuse together, and it looks like just
(15:08):
a bunch of LEDs that are on, and you can't
distinguish that number twenty seven from any other number that
might be displayed. So this speed is known as the
flicker fusion frequency. Things are flickering so fast that they
all fuse together. Perceptually, now we know that even though
you can't see the number anymore, there are cells in
(15:31):
your visual cortex that can follow flicker at much higher
rates than your consciousness can. So the question was this,
if you're in a terrifying event, can you actually see
in slow motion like Neo in the matrix who sees
in bullet time, and can you therefore distinguish the flashing
numbers at a faster rate than you would be able
(15:53):
to normally. In other words, we set the pace of
alternating lights just faster than you can normally see, just
beyond the flicker fusion frequency. So if your vision speeds
up like a slow motion camera taking in more frames
per second, then you should be able to report the
number that was being flashed. If, on the other hand,
(16:17):
you're not actually seeing in slow motion but instead just
laying down more memory, you'd be no faster at reading
the display and it wouldn't look like anything to you.
So we got twenty three volunteer participants to do the fall,
and here's how it works. Imagine you're the volunteer. First,
we measure your flicker fusion threshold under a normal relaxed circumstances,
(16:41):
in other words, how fast I can alternate these numbers
before you can't see them anymore. Then we put you
on the platform that's winched fifteen stories up above the ground.
You strap the perceptual chronometer to your wrist, and then
you're attacked to this bolet hook that's dangling way above
(17:02):
the net, and we set the speed of alternation of
the lights to just slightly faster than you can see
any number on there, and you're instructed to keep your
eyes on your wrist in front of you. And then
at a moment you're not expecting the hook releases during
the fall, your only job is to identify the random
(17:26):
number flashing on the watch. That's it. If you're having
higher temporal resolution. During the free fall, the rate of
alternation should appear slowed, which would allow you to read
the numbers that would otherwise be unreadable. But that was
only one part of the experiment. After the fall, we
had participants retrospectively reproduce how long they're fall took using
(17:51):
a stop watch. So you think back on your fall
and you start the stopwatch when you picture the hook
being released, and you stop when you think you hit
the net, so you're reproducing it in your mind. And
then what you also do is you watch other people
take the fall and you reproduce that memory on your
(18:12):
stop watch as well, so the moment they were released
to the moment they hit the net in your memory.
And what we found here, consistent with the verbal reports,
is that everyone estimates to the duration of their own
fall to be longer than when they're remembering someone else's
fall the same fall. On average, people felt that their
(18:33):
own falls took at least thirty percent longer. But the
surprise came with the results from the perceptual chronometer. No
one was able to read the numbers in free fall
at a faster rate than they could when they were
standing calmly on the ground. And it is not because
they closed their eyes or didn't pay attention. We monitored
(18:53):
for that carefully, but because they couldn't, after all, see
time and slow motion. So despite my subjective experience of
falling from the roof, I hadn't after all seen my
surroundings in bullet time like NEO. Now, this wasn't necessarily
the result I was expecting. So we analyzed this data
(19:15):
every which way to make sure there wasn't a mistake,
and there wasn't. People weren't actually seeing in slow motion,
and this was the first step to realizing the link
between time and memory. The reason participants reported a longer
duration for their own fall, even though they were seeing
(19:36):
no faster than normal, comes down to a walnut sized
area of the brain called the amygdala. When there's an
(20:06):
emergency situation, the amygdala kicks into high year and it
commandeers the resources of the rest of the brain and
it forces everything to attend to the situation at hand. Now,
what's emerged in neuroscience in the last few decades is
that when the amigdala gets involved, memories are laid down
(20:27):
on a secondary memory system. This is not your normal
memory system, for everyday stuff which is taken care of
by the hippocampus, but a secondary track because that's what
memories are. Four. In an emergency situation, when everything is
hitting the fan, that's when you want to make sure
(20:47):
that you write down all the details for future reference.
Now here's the key. When you play these memories back out,
your brain interprets the higher density of data as a
longer duration. So under normal everyday circumstances, most of what
(21:08):
happens to you passes right through your system and very
little gets retained. You don't remember much of anything about
the details of who you passed on the street today,
or all the billboards you saw on your drive, or
the color of the car in front of you, or
who is in front of you in line at the
coffee shop, or much else. When you're judging how long
(21:30):
something lasted, the only way you can do it is
by looking back and essentially counting up memories. Your brain
doesn't get time information for free. It's not like it
has a built in clock. It's made up of billions
of cells and that's all it has to work with.
So through experience it figures out how to make correlations.
(21:55):
If I have this much memory I can draw on,
then that event must have lasted ten seconds, or ten months,
or ten years. And in this way, duration is always
a retrospective estimate and is totally dependent on how much
memory you have, what landmarks you can identify in your
(22:15):
memory landscape. And this is why time and memory are linked.
But here's what's really important to know about this consciousness.
Your experience of the world right now, it's always a
story that's told retrospectively. You're not conscious of anything in
the moment in real time. But consciousness is always about
(22:38):
your brain asking itself what does happened? What has happened?
And it pulls the appropriate signals from whatever is available
to answer that question. So the reason that police officer
remembered his gunshots as being far apart in time is
because he was laying down so many details of the footage,
(22:58):
so many memories. The car is approaching him, he jumps
out of the way, he hits the ground, he's shooting
at the side, he shoots at the back window, the
closeness of the squealing tires, one hundred other details. All
that gets stored by this emergency memory storage system. And
(23:19):
so when his brain says, what has happened? What has happened?
He has such a density of memory that his brain
concludes naturally that the event must have been spread out
over a long time. And the same goes for that
doctor in the motorcycle accident. In a normal five seconds
of riding along on the road, not much as getting
(23:41):
written down in your memory. But when you're on the road,
rolling on the asphalt, and possibly about to die, your
brain is keeping track of everything it can. So when
your brain says what just happened, it has such a
density of memories that it assumes the event lasted long. Now,
(24:01):
getting back to the test that I conducted. After I
published these results, several people independently said to me, Hey,
I read your paper, but I think you're wrong because
I know that I experienced the car accident in slow motion.
So I just asked them, look, the person who was
sitting next to you on the passenger seat, did it
(24:23):
really sound like they were saying, Because if not, then
you weren't actually experiencing the world in slow motion. And
they have to allow that if time were really stretched out,
everything would have to be in slow motion like a movie.
So I want to add there are some interesting exceptions
(24:44):
to the slow motion effect. It only happens in certain circumstances,
and the reason is because it depends on whether or
not you are expecting or foreseeing the disaster that's heading
your way. This is what I call the sliding on
ice towards a brickwall phenomenon. If you're in that situation
(25:05):
and you see what's coming, then all of your attention
is riveted on the details, and so as we just saw,
you're capturing them for later analysis in your memory. So
you have the retrospective impression that it all must have
taken a long time. But interestingly, when something unexpected happens,
(25:27):
when you don't see it coming at all, you don't
have time to put your attentional systems on it and
write down the memories, and in retrospect, it seems like
it happened with no time at all. Once, when I
was biking, my front tire went into a pothole and
I went flying over the handlebars. But I don't remember
anything from the event because the whole thing came as
(25:49):
a surprise. I didn't see it coming. And this is
what happens when people are t boned in their car
by a vehicle that they didn't see the event doesn't
seem to run slow motion, but instead it's as though
time is gone. They were driving along through the intersection,
and in the next moment their car was pinned up
(26:09):
against the lamp post without any notion of what the
heck just happened. So I noticed when I interviewed people
that they described all the predictable things as though they
happened in slow motion because they had so many detailed
memories about them. But they don't describe the airbags coming
(26:29):
out in slow motion because that happens totally unexpectedly. Now,
let me get back to the big question. What is
this link between time and memory have to do with
our normal lives. Well, this is why time seems to
speed up for all of us as we get older.
(26:50):
We all have the impression that a childhood summer seemed
to last forever, But when you're older, the summers are
here and then they're gone, and years zip by and
decades zip by. Well, now you know why. It's because
the job of the brain is to build an internal
model of the world out there. Your brain is locked
(27:13):
in silence and darkness inside your skull, and all it's
trying to do is understand the structures of the world
so it can operate in it better, and whenever it
encounters a surprise, it writes that down and it makes
changes to your circuitry. But as you go through life
and your brain develops better models of the world, less
(27:36):
and less carries much surprise. And this is why you
lay down fewer memories as you age. It's because you've
seen that situation before, and you've met that personality before,
and you've done that job before, and so the memories
that you lay down are much thinner, they're more impoverished.
(27:57):
But in contrast, when you're in your childhood, everything is new,
and so the richness of that of your memories gives
you the impression of increased duration. When you are looking
back at the end of a childhood summer, it seems
to have lasted for such a long time because everything
was new. But when you're looking back at the end
(28:18):
of an adult summer, it seems to have disappeared rapidly
because you haven't written much down in your memory. So
I don't recommend emergency situations, but it sure does make
you operate like you're a child again. So here is
the take home lesson. We have to seek novelty because
(28:41):
this is what lays down new memories in the brain.
So one thing I do every day that I can,
I drive home a different route from work. It's not
that hard and it doesn't take much longer, but it
allows me to see things in a fresh way. Most
of us have had the experience that when you drive
to work for the first time, it seems to take
(29:02):
a really long time, but after that it shrinks. And
it's because you're becoming an automatized zombie and you're just
running this program unconsciously of driving to work. You're not
noticing new things anymore. And another thing I try to
do is rearrange my office every month or so. It's
really easy. You just push your desk over to the
(29:24):
other side. You maybe swap the artwork on the walls,
things like that. These are easy things to do. One
thing that I recommend is tonight brush your teeth with
your other hand. It's not that hard to do, but
it will make you seem as though you are extending
your time a bit because you're forcing your brain off
(29:46):
its hamster wheel of doing things a particular way every day.
And by the way, if you wear a watch or
a fitbit switch it to the other hand, so that
when you are looking at it, it's not just an
automatic thing, but it's something you have to put a
little bit of attention towards. So all these kind of things,
any version of this, it's the best thing that you
(30:06):
can do to perceptually extend your life. That's all for
this week. To find out more and to share your thoughts,
head over to eagleman dot com, slash Podcasts, and you
can also watch full episodes of Inner Cosmos on YouTube.
(30:26):
Subscribe to my channel so you can follow along each
week for new updates until next time. I'm David Eagleman,
and this is the Inner Cosmos.
So you always hear people say things like I got
in a car accident and the whole thing seemed to
happen in slow motion. I saw the hood crumple and
the rear view mirror fall off, and I was watching
the other driver's expression. And it's the same thing with
gunfights or skiing accidents or motorcycle crashes. But from a
(00:26):
neuroscience perspective, is it true that time slows down? And
how could you test that? And why does your drive
to work on the first day seemed to take a
long time, but after a while it takes no time
at all. And why do the years seem to go
by faster as we get older? Welcome to inner Cosmos
(00:47):
with me, David Eagleman. I'm a neuroscientist and an author
at Stanford University, and I've spent my whole career studying
the intersection between how the rain works and how we
experienced life. The first time I experienced time slowing down,
(01:11):
I was eight years old. It was a Saturday, and
my brother and I left the house to find something
to do, and on the way out the door, our
father warned us not to go near the house under construction,
and so we told him we wouldn't, and being children,
we of course went straight to the house under construction.
So we poked around like kids do, and eventually we
(01:34):
found a ladder and we went up onto the roof,
and from there one could enjoy a wonderful view of
the mountains of Albuquerque, New Mexico. And my brother wandered
off to explore some other part of the roof, and
I stepped forward to stand at the edge. Now I
didn't know what tar paper was. I didn't know that
(01:55):
it was stiff and that it extended past the edge
of the roof on center construction. So when I thought
I was stepping to the roof's edge, I was actually
stepping on the tar paper, and I began to fall.
As I fell, I thought about grabbing for the roof's edge,
(02:18):
but some part of my brain recognized I was too
late for that. So I found myself in a spread
eagle position, looking way down to the red brick floor below,
And as I fell towards what was likely to be
my death, I was thinking calmly about how similar my
(02:39):
fall was to that scene in Alice in Wonderland when
she falls down the rabbit hole. It was totally calm
and peaceful. I didn't have any fear or panic. I
was just thinking about a moment from a children's story.
So it won't surprise you that I lived. But it
(03:01):
did surprise my parents and the emergency room physicians because
I'd fallen twelve feet and landed on my face, on
my nose, and I'd lost consciousness and a lot of blood,
and I'd shattered all the cartilage in my nose. But
what stayed with me wasn't anything about that or the pain.
It was a fascination with what had happened. So fast
(03:24):
forward seven years later, I'm in high school physics, and
I learned the formula D equals one half at squared,
and that allows me to calculate how long the fall took.
And I realized the fall had only taken point six
of a second. What that couldn't be right. It seemed
to have taken so much longer. So fast forward some
(03:46):
more years and I become a neuroscientist, and my graduate
thesis was a large computational model of a chunk of
brain tissue and the signaling that happens in there. But
the experience of my falls mysteriously long duration never left me.
So once I became faculty, I started looking into this
and I started collecting stories from people. So I'm going
(04:10):
to start with one from a police officer. So one
morning he got radio that two suspects were heading his
way in a police car chase and that he should
position his car in the middle of the road to
stop them. So he does that, and he sees the
car coming in from the distance, and he stands in
(04:31):
the middle of the street and raises his hand for
them to stop, but they just keep coming, and they're
coming right at him. So he draws his revolver and
he points it at the driver with the intention of
shooting him through the windshield. And the car is so close,
and for him, it seemed like time went into slow motion.
(04:52):
And here's how he reports his thoughts. Now, wait a second,
these are three fifty seven hollow points, and they should
go right through the glass. But since the glass is angled,
what if it ricochets off the glass and kills someone
on the second story of that house over there. Anyway,
he suddenly realizes that the car is almost on top
(05:14):
of him, so he jumps out of the way, and
at the same motion he squeezes off around at the
driver's door, bang, and as the car goes by, he
then pulls off a second round bang, and then as
the car is almost all the way past him, he
feels his finger pull off the third shot bang, and
he assumes that he'd fired at the rear window, but
(05:38):
he noticed that the glass hadn't broken, and so he
starts to worry that maybe he'd missed, and maybe he'd
shot a bystander down the road, and so he immediately
is thinking about how his career might be over, And
so his partner comes running up to him, and in
the conversation afterwards, he realizes that his partner had witnessed
(06:01):
a very different event. His partner said that the entire
incident from the car approaching to when it went by,
took maybe all of three seconds. And his partner said
that the three shots sounded like bang bay bang, but
it didn't feel that way to the officer firing the shots.
(06:22):
It seemed like he had taken a lot of time
to think about ricocheting, about people sitting in their living rooms,
about whether the shot had hit the back window, about
whether the shot would possibly hit a guy in a
bar or some distance away, and in his mind the
shots went bang bang bang, as though everything were happening
(06:45):
at a much slower pace. So how is it that
a bang bang bang from one guy is perceived by
someone else's bang bay bang? How does that happen? Now?
Here's another story from a doctor who got in a
motorcycle accident. So he's going forty five miles an hour
down the road. A car pulls out of the driveway
(07:06):
and he comes off his bike and he hits the
road and he rolls four or five times, and time
appears to slow down, and he feels like he's rolling forever.
So after he rolls twice, he thinks, gad, when am
I ever going to stop rolling? So it seemed like
(07:26):
time had slowed down for him. And when he was
thinking about this later, he estimated it would take him
about two and a half or three seconds to think
that particular thought, and so that provided him with a
timescale of the amount of time that a single roll
seemed to take. So when he calculated this later in retrospect,
(07:48):
he determined that the whole event seemed to have taken
about fifteen seconds, but it couldn't have taken any longer
than five or Another report I collected was from a
mother who saw her three year old child fall into
the shallow part of a lake at a little distance
away at a park. So, like any parent would, she
(08:08):
started immediately sprinting towards the lake, but it seemed to
take forever to reach there. Now, her child was fine,
and in fact it didn't take her that long, but
she was haunted by remembering her thoughts during what seemed
like a painfully slow process of reaching her child. And
this impression that time runs slowly is not an uncommon occurrence.
(08:33):
Other people I interviewed describe things like car accidents where
they watched the whole event unfold slowly with a kind
of inevitability, the car sliding towards them impacts and the
door crushes and so on, Or the victim of a
mugging describing the way that the mugger reaches into his
(08:54):
jacket to draw a weapon, or a person who's been
in an accident with a skateboard going towards the parked car.
All of these things involve very short time windows that
for some reason seem very lengthy, and these people, like me,
reported that the sensation of time had seemed to proceed
(09:15):
more slowly than normal, And so these reports made it
seem possible to me that the brain has a capacity
to operate at a higher frame rate, which is how
filming slow motion in the movies works. You capture information
at a higher frame rate and then you play it
back at normal speed. But what if there was another
(09:37):
possibility here? What if, for example, it's a trick of memory,
such that you're laying down denser memories and when you
read it back out, your brain's only conclusion is, well,
if I have that much memory, that must correspond to
five seconds, when in fact it only lasted one second.
So I wanted to understand what was happening here the brain,
(10:00):
So I scoured the neuroscience literature, but it turned out
no one had ever put the question of slow motion
perception to the test. Why not, Well, it's because it
would require placing volunteer subjects in life threatening situations, which
is not a clear path to tenure for an academic.
(10:21):
But without a rigorous scientific experiment, I realized it was
difficult to know how to interpret these experiences, including my own,
from a neuroscience point of view, and I was obsessed
with figuring out how to test this first I needed
(10:44):
something scary, so I packed up stop watches and pads
of paper, and I took all the members of my
laboratory to Astro World, which was the local amusement park,
and we set out to find the most terrifying roller coaster.
(11:04):
We had a fantastic time as a group, and we
did a lot of laughing, but at the end of
the day we couldn't find anything frightening enough to give
us the impression that time had moved in slow motion.
We needed something more terrifying, so we kept looking, and
three weeks later, and three hundred miles away, we found it.
(11:28):
SCAD diving Now SCAB stands for suspended catch air device.
Imagine a huge metal tower. It's one hundred and fifty
feet tall. It's kind of like a poor man's Eiffel Tower,
and you step on a small platform that pulls you
(11:50):
up like a small elevator, and you find yourself standing
at the very top of the tower, looking down on
the city. Now, you put a big leather harness on
your back, and then you click the front of your
harness into a bolet hook. You position yourself so that
you're hanging from the hook, cradled in that piece of
(12:12):
leather dangling in the air with a net one hundred
and fifty feet below you, and then the hook releases
and you are in free fall backwards, looking at the sky,
falling backwards, not even able to see where the net
(12:34):
is or how much time you have left. When you
finally hit the net below, you're going seventy miles an hour,
and the net catches you softly and you finally breathe again.
This was sufficiently scary. Now I'm going to get back
to the experiment in just a moment, but first I
(12:57):
want to specify that this isn't your typical in the
lab science experiments. So I had to do a lot
of convincing to get the university to sign off. It
took me seven months, but we were finally ready. So
before we tested anyone, I took the plunge myself three
times in a row, and I can tell you that
(13:17):
each time was equally terrifying as the previous. There's no
getting used to falling backwards from a height like that.
It goes against every Darwinian instinct that you have in
terms of staying alive. But back to the question, we've
now found something sufficiently scary. How do we do the
(13:37):
experiment to see if people are overclocking or having a
faster frame rate in the moment. So in my lab
we engineered a wristband that we called the eagle eye,
or more technically the perceptual chronometer, which is just a
fancy way of saying something that can measure the speed
(13:59):
of your perception, in other words, how fast you're taking
in information from the world. So picture this. It's like
a watch with a big face, and it has a
rectangular screen of small LED lights. So we can display
a number on it, let's say the number twenty seven,
by turning on the LEDs that make that number. But
(14:23):
here's the trick. We now switch the lights so that
in the next moment, all the LEDs that are on
turn off, and all the ones off turn on, So
that still shows you a twenty seven. But now it's
like a negative photograph where the background is lit but
the number isn't, so you can still easily read that
as twenty seven. Now what we do is we alternate
(14:46):
the positive and negative images rapidly, so all the lights
are blinking on and off and at a fast pace.
You can still easily see that the number being displayed
is twenty seven, But if we make it just a
little bit faster than that, you can't see any number
at all, because the speed is such that the positive
and negative images fuse together, and it looks like just
(15:08):
a bunch of LEDs that are on, and you can't
distinguish that number twenty seven from any other number that
might be displayed. So this speed is known as the
flicker fusion frequency. Things are flickering so fast that they
all fuse together. Perceptually, now we know that even though
you can't see the number anymore, there are cells in
(15:31):
your visual cortex that can follow flicker at much higher
rates than your consciousness can. So the question was this,
if you're in a terrifying event, can you actually see
in slow motion like Neo in the matrix who sees
in bullet time, and can you therefore distinguish the flashing
numbers at a faster rate than you would be able
(15:53):
to normally. In other words, we set the pace of
alternating lights just faster than you can normally see, just
beyond the flicker fusion frequency. So if your vision speeds
up like a slow motion camera taking in more frames
per second, then you should be able to report the
number that was being flashed. If, on the other hand,
(16:17):
you're not actually seeing in slow motion but instead just
laying down more memory, you'd be no faster at reading
the display and it wouldn't look like anything to you.
So we got twenty three volunteer participants to do the fall,
and here's how it works. Imagine you're the volunteer. First,
we measure your flicker fusion threshold under a normal relaxed circumstances,
(16:41):
in other words, how fast I can alternate these numbers
before you can't see them anymore. Then we put you
on the platform that's winched fifteen stories up above the ground.
You strap the perceptual chronometer to your wrist, and then
you're attacked to this bolet hook that's dangling way above
(17:02):
the net, and we set the speed of alternation of
the lights to just slightly faster than you can see
any number on there, and you're instructed to keep your
eyes on your wrist in front of you. And then
at a moment you're not expecting the hook releases during
the fall, your only job is to identify the random
(17:26):
number flashing on the watch. That's it. If you're having
higher temporal resolution. During the free fall, the rate of
alternation should appear slowed, which would allow you to read
the numbers that would otherwise be unreadable. But that was
only one part of the experiment. After the fall, we
had participants retrospectively reproduce how long they're fall took using
(17:51):
a stop watch. So you think back on your fall
and you start the stopwatch when you picture the hook
being released, and you stop when you think you hit
the net, so you're reproducing it in your mind. And
then what you also do is you watch other people
take the fall and you reproduce that memory on your
(18:12):
stop watch as well, so the moment they were released
to the moment they hit the net in your memory.
And what we found here, consistent with the verbal reports,
is that everyone estimates to the duration of their own
fall to be longer than when they're remembering someone else's
fall the same fall. On average, people felt that their
(18:33):
own falls took at least thirty percent longer. But the
surprise came with the results from the perceptual chronometer. No
one was able to read the numbers in free fall
at a faster rate than they could when they were
standing calmly on the ground. And it is not because
they closed their eyes or didn't pay attention. We monitored
(18:53):
for that carefully, but because they couldn't, after all, see
time and slow motion. So despite my subjective experience of
falling from the roof, I hadn't after all seen my
surroundings in bullet time like NEO. Now, this wasn't necessarily
the result I was expecting. So we analyzed this data
(19:15):
every which way to make sure there wasn't a mistake,
and there wasn't. People weren't actually seeing in slow motion,
and this was the first step to realizing the link
between time and memory. The reason participants reported a longer
duration for their own fall, even though they were seeing
(19:36):
no faster than normal, comes down to a walnut sized
area of the brain called the amygdala. When there's an
(20:06):
emergency situation, the amygdala kicks into high year and it
commandeers the resources of the rest of the brain and
it forces everything to attend to the situation at hand. Now,
what's emerged in neuroscience in the last few decades is
that when the amigdala gets involved, memories are laid down
(20:27):
on a secondary memory system. This is not your normal
memory system, for everyday stuff which is taken care of
by the hippocampus, but a secondary track because that's what
memories are. Four. In an emergency situation, when everything is
hitting the fan, that's when you want to make sure
(20:47):
that you write down all the details for future reference.
Now here's the key. When you play these memories back out,
your brain interprets the higher density of data as a
longer duration. So under normal everyday circumstances, most of what
(21:08):
happens to you passes right through your system and very
little gets retained. You don't remember much of anything about
the details of who you passed on the street today,
or all the billboards you saw on your drive, or
the color of the car in front of you, or
who is in front of you in line at the
coffee shop, or much else. When you're judging how long
(21:30):
something lasted, the only way you can do it is
by looking back and essentially counting up memories. Your brain
doesn't get time information for free. It's not like it
has a built in clock. It's made up of billions
of cells and that's all it has to work with.
So through experience it figures out how to make correlations.
(21:55):
If I have this much memory I can draw on,
then that event must have lasted ten seconds, or ten months,
or ten years. And in this way, duration is always
a retrospective estimate and is totally dependent on how much
memory you have, what landmarks you can identify in your
(22:15):
memory landscape. And this is why time and memory are linked.
But here's what's really important to know about this consciousness.
Your experience of the world right now, it's always a
story that's told retrospectively. You're not conscious of anything in
the moment in real time. But consciousness is always about
(22:38):
your brain asking itself what does happened? What has happened?
And it pulls the appropriate signals from whatever is available
to answer that question. So the reason that police officer
remembered his gunshots as being far apart in time is
because he was laying down so many details of the footage,
(22:58):
so many memories. The car is approaching him, he jumps
out of the way, he hits the ground, he's shooting
at the side, he shoots at the back window, the
closeness of the squealing tires, one hundred other details. All
that gets stored by this emergency memory storage system. And
(23:19):
so when his brain says, what has happened? What has happened?
He has such a density of memory that his brain
concludes naturally that the event must have been spread out
over a long time. And the same goes for that
doctor in the motorcycle accident. In a normal five seconds
of riding along on the road, not much as getting
(23:41):
written down in your memory. But when you're on the road,
rolling on the asphalt, and possibly about to die, your
brain is keeping track of everything it can. So when
your brain says what just happened, it has such a
density of memories that it assumes the event lasted long. Now,
(24:01):
getting back to the test that I conducted. After I
published these results, several people independently said to me, Hey,
I read your paper, but I think you're wrong because
I know that I experienced the car accident in slow motion.
So I just asked them, look, the person who was
sitting next to you on the passenger seat, did it
(24:23):
really sound like they were saying, Because if not, then
you weren't actually experiencing the world in slow motion. And
they have to allow that if time were really stretched out,
everything would have to be in slow motion like a movie.
So I want to add there are some interesting exceptions
(24:44):
to the slow motion effect. It only happens in certain circumstances,
and the reason is because it depends on whether or
not you are expecting or foreseeing the disaster that's heading
your way. This is what I call the sliding on
ice towards a brickwall phenomenon. If you're in that situation
(25:05):
and you see what's coming, then all of your attention
is riveted on the details, and so as we just saw,
you're capturing them for later analysis in your memory. So
you have the retrospective impression that it all must have
taken a long time. But interestingly, when something unexpected happens,
(25:27):
when you don't see it coming at all, you don't
have time to put your attentional systems on it and
write down the memories, and in retrospect, it seems like
it happened with no time at all. Once, when I
was biking, my front tire went into a pothole and
I went flying over the handlebars. But I don't remember
anything from the event because the whole thing came as
(25:49):
a surprise. I didn't see it coming. And this is
what happens when people are t boned in their car
by a vehicle that they didn't see the event doesn't
seem to run slow motion, but instead it's as though
time is gone. They were driving along through the intersection,
and in the next moment their car was pinned up
(26:09):
against the lamp post without any notion of what the
heck just happened. So I noticed when I interviewed people
that they described all the predictable things as though they
happened in slow motion because they had so many detailed
memories about them. But they don't describe the airbags coming
(26:29):
out in slow motion because that happens totally unexpectedly. Now,
let me get back to the big question. What is
this link between time and memory have to do with
our normal lives. Well, this is why time seems to
speed up for all of us as we get older.
(26:50):
We all have the impression that a childhood summer seemed
to last forever, But when you're older, the summers are
here and then they're gone, and years zip by and
decades zip by. Well, now you know why. It's because
the job of the brain is to build an internal
model of the world out there. Your brain is locked
(27:13):
in silence and darkness inside your skull, and all it's
trying to do is understand the structures of the world
so it can operate in it better, and whenever it
encounters a surprise, it writes that down and it makes
changes to your circuitry. But as you go through life
and your brain develops better models of the world, less
(27:36):
and less carries much surprise. And this is why you
lay down fewer memories as you age. It's because you've
seen that situation before, and you've met that personality before,
and you've done that job before, and so the memories
that you lay down are much thinner, they're more impoverished.
(27:57):
But in contrast, when you're in your childhood, everything is new,
and so the richness of that of your memories gives
you the impression of increased duration. When you are looking
back at the end of a childhood summer, it seems
to have lasted for such a long time because everything
was new. But when you're looking back at the end
(28:18):
of an adult summer, it seems to have disappeared rapidly
because you haven't written much down in your memory. So
I don't recommend emergency situations, but it sure does make
you operate like you're a child again. So here is
the take home lesson. We have to seek novelty because
(28:41):
this is what lays down new memories in the brain.
So one thing I do every day that I can,
I drive home a different route from work. It's not
that hard and it doesn't take much longer, but it
allows me to see things in a fresh way. Most
of us have had the experience that when you drive
to work for the first time, it seems to take
(29:02):
a really long time, but after that it shrinks. And
it's because you're becoming an automatized zombie and you're just
running this program unconsciously of driving to work. You're not
noticing new things anymore. And another thing I try to
do is rearrange my office every month or so. It's
really easy. You just push your desk over to the
(29:24):
other side. You maybe swap the artwork on the walls,
things like that. These are easy things to do. One
thing that I recommend is tonight brush your teeth with
your other hand. It's not that hard to do, but
it will make you seem as though you are extending
your time a bit because you're forcing your brain off
(29:46):
its hamster wheel of doing things a particular way every day.
And by the way, if you wear a watch or
a fitbit switch it to the other hand, so that
when you are looking at it, it's not just an
automatic thing, but it's something you have to put a
little bit of attention towards. So all these kind of things,
any version of this, it's the best thing that you
(30:06):
can do to perceptually extend your life. That's all for
this week. To find out more and to share your thoughts,
head over to eagleman dot com, slash Podcasts, and you
can also watch full episodes of Inner Cosmos on YouTube.
(30:26):
Subscribe to my channel so you can follow along each
week for new updates until next time. I'm David Eagleman,
and this is the Inner Cosmos.
Host
David Eagleman
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