All language subtitles for The Mind Explained - Memory 2019 .S01E01.eng

Some moments feel so important,

we believe there is
a perfect recording of them

etched in our minds.

That's one small step for man...

Tear down this wall!

Diana, Princess of Wales, is dead.

For many, 9/11 was one of those moments.

I was getting ready
to go to class, and I put on the TV...

And the newscaster stopped
and said, "This just in."

Two planes hit the Twin Towers.

Every single channel had
a building that was on fire.

This businessman was
covered in dust.

And I saw the big hole
in the side of the building.

Yeah, it was sort of surreal.

Very confusing and disorienting.

I felt a sense of dread.

I remember my mom was working
in the city and I remember

smoke billowing out over the water
of the Long Island Sound

behind the building where I went
to elementary school.

I was just talking with my parents
about it one day and my mom goes,

"No, you know in 2001,

I was working in Connecticut."

And there were other problems
with Melanie's memory of that day.

Her classroom windows didn't look out
over the water,

the World Trade Center
was over 40 miles away,

and the smoke was drifting
in the opposite direction.

How could I possibly have seen the smoke
billowing from over the water?

Like, how would I see that?

Your memories for 9/11 are
probably not as accurate as you think.

We know about 50% of the details
of that memory change in a year

even though most people are convinced
they're a hundred percent right.

They might correctly remember
the gist of the day,

but not details like
who they were with,

what they were doing when they heard,
and what exactly they saw.

Even our most significant memories,

the ones that form the foundation
of our life story,

aren't perfect recordings.

They can shift and warp over time.

It feels like the whole purpose of memory
should be to preserve the past.

So why are memories so unreliable?

How exactly does remembering work?

Wait a second now,
I do remember, you're... Um...

Memory, that everybody has,

is a gold mine of unexplored
and untapped potential.

Our memory just mediates
our interaction with the world.

Memory is one of our
most fundamental activities,

and it is only when it fails us
that we think about it at all.

Yanjaa Wintersoul
is a grand master of memory.

Alright, here we go.

Five years ago, she discovered
the world of memory competitions.

When I first started,

it was mostly, like,
a bunch of white guys from Europe

in very, like, sad-looking
competition rooms.

They memorize decks of cards in seconds,

thousands of digits in an hour.

It looks like we're all taking
very speedy SATs.

I have three world records:

one for images, one for names and faces,
and one for words.

And she's demonstrated
her skills on TV shows around the world.

Okay, page 38.

Starts mid-sentence.

"Information effectively by using humor."

We gave her ten minutes
to memorize these 500 numbers, and...

Five, three, nine...

one, six, six...

- nine, seven...
- ...four, seven, eight...

- ...seven, six, five, eight...
- ...four, seven, seven, nine...

...one, seven... two...

- ...two, two, five...
- ...nine, zero, two...

- ...six, four, eight, two...
- ...one, six, one, one, two.

How does she do that?

Yay!

It all comes down to the peculiar way
our brains store memories.

And perhaps no brain has taught us more
about memory than this one.

It belonged to a man
named Henry Molaison.

When Henry was 27,
he had brain surgery to treat epilepsy

and the surgeon removed this little piece
of his brain.

The surgeon noted that the procedure
resulted in no marked behavioral changes,

with the one exception of
a very grave recent memory loss.

It was so severe, it prevented Henry
from navigating his own house

and recognizing his doctors.

But Henry still had other types of memory,

habits that don't require
conscious thought,

like how to ride a bike,

so-called "implicit memories."

He also kept some conscious,
or "explicit," memories.

He discussed historical events
with his doctor

in this recording from the early '90s.

What happened in 1929?

- The stock market crashed.
- It sure did.

That's an example of semantic memory:

facts, dates, numbers, words, the kinds
of things that memory athletes memorize.

The real damage was
to Henry's episodic memory,

his memory for personal experiences.

When his doctor asked,
"Do you know what you did yesterday,"

he replied...

No, I don't.

How about this morning?

I don't even remember that.

Without this one small part of his brain,

Henry had trouble forming new memories.

But that doesn't mean memories
are stored in one specific place.

When you have an experience,
say performing at a recital,

sensory information is processed
to many different parts of your brain.

The sound of the cello.

The feeling of the strings
under your fingers.

The face of your friend in the audience.

The pang of stage fright.

And the part of the brain that pulls
all of these elements together,

the part that Henry's surgery
badly damaged,

is the medial temporal lobe,

which includes an important structure
called the hippocampus.

When you relive that moment later,

the medial temporal lobe
helps combine those elements once again.

Your life story is all the moments
like this that you can relive.

In this graph is the life story
of a typical 70-year-old.

There are lots of memories
from the recent past,

but as you move backward in time,
they start to fall off.

There are only a few memories
from childhood,

and nothing before around three,

but there's this surprising bump
in our teens and 20s.

When you're getting through high school,
you're having a lot of momentous occasions

in that stage of your life.

And when we think about our life stories,

those change moments are the ones
that stand out

as the ones that kind of define us

and define our lives going forward.

Some people have
more memories than others,

and you can improve your memory by just
living a healthier and more active life.

I try to, like, not drink as much,
sleep a lot, and eat well.

The one thing that I've seen
in every single study

that's like "this is gonna work"
is honestly meditation.

Undergraduates were able
to increase their score on the verbal GREs

from 460 to 520, just by taking
a mindfulness meditation class.

Probably because meditation
improves focus and focus improves memory.

And when it comes to personal experiences,

there are certain features that make us
remember some better than others.

First, emotion.

If you show a person a string of faces,

they'll remember
the most emotional ones best.

When we have an emotional experience,
our amygdala,

the emotional center of the brain,
which sits right next to the hippocampus,

actually up-regulates the hippocampus

and allows it to form
a more detailed and stronger memory.

One of the things we wanted to do
after 9/11

was look into the brains of individuals
who were in New York that day.

So about half the people were,
on average, around Midtown,

and the other half of people were
much closer to the World Trade Center.

Three years after the attacks,

they asked those people to remember
their experiences.

The individuals who were closer
to the World Trade Center that day,

the 9/11 memories were more vivid
and we saw more activity in the amygdala.

Memories are also connected
to a sense of place.

One of the things we know from our study
of 9/11 memories is that

the thing that people were
most consistent about was where they were.

- I had just gotten home.
- Gym class.

I was living in London
at the time.

In New Smyrna Beach, Florida.

The Upper East Side.

So we think place
has a particularly strong role in memory.

And if you actually look
in the hippocampus,

there seem to be cells that are
specifically responsive to time and place.

Here's a representation
of these "place" cells

in the hippocampus of one particular rat.

And here's a video of that rat
moving along a simple track.

His head is in this green circle,
and here's his tail.

Each place cell is associated with
a particular location along the track

and these cells have been color-coded
by scientists.

When the rat is at the start of the maze,
this green place cell fires.

But as it moves along,
a different cell is activated,

and then another, and another.

When the rat pauses, the cells fire in
rapid succession as he recalls his route.

London cabbies must navigate
their own rat maze.

To get their licenses, they have to pass
a century-old test called simply

"the knowledge."

They spend years memorizing
London's 25,000 streets.

Scientists scanned the brains
of would-be cabbies

before and after this process.

In the brains of people
who didn't end up getting their licenses,

the size of the hippocampus
didn't really change.

But those who passed, interestingly,
their hippocampi actually grew.

Finally, memories can be strengthened
by story.

Our brains pay much closer attention
to information

when it's in the form of a narrative.

In one study, 24 people were asked
to memorize 12 lists of ten words.

Half the people
studied and rehearsed the list,

and they remembered, on average,
13% of the words.

The other half wove the words
into stories of their own invention,

and they remembered 93%.

The more that you can associate
things you want to remember

with structures you already have
in your mind,

the easier it's going to be to remember.

You know, you're creating a narrative.

When we go to retrieve that memory,

we have almost many multiple ways
of getting into that memory.

Story, place, and emotion
are the foundation

of some of our strongest memories.

And those same features can be hijacked
to help you, say,

memorize 500 random digits.

Yes, let's do it.

Starting with the first three digits,

she converts numbers into sounds
using her own personal code.

So 5 is an "s,"

3 is an "a," and 9 is a "g," 'cause...
just because of the shapes.

So then it's basically like
you're reading something

instead of looking at all these numbers.

So 539 is SAG.

And the next triplet, 166,
becomes TBB.

And I think of
the Middle Eastern dish of tabbouleh.

She pairs the two words
to create a striking scenario.

This saggy, half-naked person
is covered in, like, tabbouleh rice,

and because it's disgusting,
I remember it more.

Anything that has, like, visceral
or, like, very emotional things,

your brain is like, ugh.

She translates
the rest of the digits the same way.

Gimli from Lord of the Rings,
he is running for office.

Rami Malek buying boots.

My spleen turns into the Lourve.

Next, Yanjaa harnesses the power of place

with an ancient technique called
"the memory palace."

She imagines herself walking through
a neighborhood she knows well,

adding surreal imagery along the route.

It helps in putting...

very random abstract things in order

when you attach it to something
you already know.

So I come out of the High Street metro.

So a saggy-skinned person

is just covered in tabbouleh.

And a little further on...

In that tunnel, 478, that's a reef,

and 468, that's ravioli,

so it's a tunnel that's now a reef
and full of ravioli.

On the carousel,
we'll have a big alpaca llama

and it's, like, eating this tube
of, like, melted cheese.

That dull list of numbers
became an epic travel log

full of surprising images
that she could revisit later.

Memory athletes aren't necessarily
smarter than everyday people

and they don't have bigger brains.

But they change the connections
within their brains

by training with techniques
like the memory palace.

We are more...

wired to remember that
than to remember random sets of digits.

In general, we're like emotional
and visual learners.

And storytellers.

Only a dozen people in the world have
memorized more than 20,000 digits of Pi.

But lots and lots of people
have played Hamlet

and memorized all his lines...

Words, words, words.

...which contain nearly 50,000 letters.

Remember thee!

Ay, thou poor ghost, while memory
holds a seat in this distracted globe.

But that's not the full story.

Some of the same things
that strengthen our memories

can also warp them.

And typically with emotional memories,

we tend to remember the central aspects.

So, our attention kind of zooms in
on the core of that experience,

so we might forget
some of the peripheral details,

like, you know, perhaps what a perpetrator
was wearing, but we'll remember the gun.

Emotional 9/11 memories are
just as inaccurate as everyday memories.

They both deteriorate at the same rate.

What was different is that
people were highly confident

their memories for 9/11 were correct.

Memories aren't high fidelity recordings
that we store away.

They're more like live performances,

created with input from different parts
of the brain in the present moment.

We can't remember every single detail
of every experience.

And so we use pre-existing knowledge,

such as semantic memory
or facts that we have...

Or our pre-existing biases and beliefs.

...to fill in those gaps.

That could explain the errors
in Melanie's memory of 9/11.

My mom worked in New York City
growing up all my life,

so, of course she was in the city.

And after 9/11, maybe Melanie
saw billowing smoke on TV,

and that's how it entered her memory.

So the fact that wereconstruct
our episodic memory

so we piece them back together

means that our episodic memories
are actually very flexible.

Scientists have been able
to exploit this flexibility

to plant false childhood memories
of being left at a shopping mall,

taking a hot air balloon ride,

even having tea with Prince Charles.

In one study, young adults
were asked to try to remember

a crime they had supposedly committed
in their teens,

even though these crimes
were completely fake,

made up by researchers.

After a couple of interviews
full of leading questions,

70% of the subjects accepted
that they had committed those crimes

and many came up with
rich, detailed memories

that were completely false.

One of the places where this plays out

that is unfortunate is things like,
um, eyewitness identifications.

They said they were gonna take you
into a room, we're gonna have seven men,

and that if I saw the suspect,

I was to write his number
on a piece of paper

and hand it over to the detective.

More than two decades
after she was raped,

Jennifer Thompson appeared on television
with the man she had identified

as her attacker.

After I picked out
Ronald Cotton's photograph,

that's when they said to me,
"We thought that was him."

We can boost the confidence
in a false memory

by confirming it or by
at least repeating it multiple times.

By now, Ronald's image had
completely contaminated, so to speak,

the original memory of that night,
and so...

the face of my rapist
had become Ronald Cotton,

so much so that seeing
the actual perpetrator right there...

I didn't have one memory of it.

Years after Ronald was imprisoned,

DNA evidence proved that Jennifer
had been raped by another man.

In the U.S., DNA has helped to overturn
hundreds of convictions,

and 70% of those involved
eyewitness testimony.

It's not just our memories of crimes
that can become contaminated.

It's the memories that tell us who we are
and where we came from.

Researchers interviewed
a group of 14-year-olds,

and then, decades later, asked them
to recall their teenage years.

What their relationship with their parents
was like,

how they had felt about sex
and religion,

what activities they had enjoyed.

Their memories, it turned out,
were uniformly poor.

For most memories, no better than chance.

So this poses the question:
Why would we have a memory system

that is so unreliable and error-prone
if it was designed to remember the past?

That's the big question.

And once again, those recordings
of Henry Molaison

point to a possible answer.

What do you think you'll do tomorrow?

Whatever is beneficial.

Henry often struggled
to answer questions like this.

It seemed to scientists
that he hadn't just lost his past,

he could no longer imagine the future.

Three decades after Henry's surgery,

another patient's medial temporal lobe
was severely damaged

in a motorcycle accident.

In this interview from 1988,
the patient was asked by his doctor...

Do you feel hopeful about the future?

I guess so. I don't really think much
about the future.

You don't think much about the future?

That same patient
once described thinking about the future

as being asked to find a chair
in an empty room.

The future and the past seem to be
somehow linked in the mind.

We decided to put people into the scanner

and have them remember past experiences

and imagine future experiences.

And...

we really didn't know what to expect.

When people remembered,
a particular network lit up, and...

That same network was engaged,
pretty much identically

when people were having to imagine
future events.

When you let your mind wander,
you switch back and forth all the time,

remembering and imagining.

Your mind is a time machine.

In Lewis Carroll's
Through the Looking-Glass,

the Queen of Hearts remarks,

"It's a poor sort of memory
that only works backwards."

It turns out... she's right.

The same machinery that brings all those
pieces together to relive the past

can bring some of those pieces together
with other pieces

to simulate possible futures.

Now, the flexibility that leads us
to remember things that never happened,

that undermines the justice system,

that corrupts our most vivid memories,

it starts to look like a superpower,

the key to our success as a species.

It allows us to troubleshoot
upcoming experiences,

to think through the ways in which
events might unfold,

potential obstacles that might come up

and the ways in which
we might deal with those obstacles.

And some scientists say
the simulation engine between your ears

does something even more profound:

It weaves together memories of the past
and dreams of the future

to create your sense of self.