The Man Who Forgot How to Read and Other Stories imagine...

Imagine if you picked up the paper one morning but you couldn't read it.

The letters looked foreign, unrecognisable.

But you realised you could still write.

So, you can write but you can't read.

Imagine what it would be like

if you'd never been able to recognise anyone.

Not even your closest family and friends.

No matter how many times you'd seen them,

you still couldn't recognise their face.

And what if you couldn't see and you couldn't hear?

But you had to find a way to make sense of the world.

So your only way to communicate was through touch.

Wow, look at that! Look at that!

Or what if you'd only ever seen the world in 2-D,

and then, in your fifties, you developed 3-D stereo vision?

Imagine how you would react

if the world started popping out at you for the first time.

These are the questions neurologist and writer Oliver Sacks

has been trying to come to terms with for 50 years.

I wish I could do what Spock sometimes does in Star Trek,

when he puts his hand, I think, on the head and by a Vulcan trick,

is able to fuse minds and know what's going on.

What's going on?

Dr Oliver Sacks is the most famous neurologist in the world.

With his gift for storytelling, he's managed to cross over

from medical science into popular culture,

with bestsellers like The Man Who Mistook His Wife For A Hat, and Awakenings.

Three years ago, I made a documentary with Sacks.

We discussed how music can be used to overcome neurological conditions.

I met several of his case studies, including Matt,

whose love of drumming helped him control his extreme Tourette's.

CLEARS THROAT

DRUM ROLL

It's Sacks' humanity and his curiosity which have driven

and inspired him for over half a century.

Follow my finger with your eyes.

And he's often drawn on his own experience, his own ailments,

in order to understand the challenges facing others.

But it's only now, after discovering a cancerous tumour in his eye,

that he has finally chosen to explore the wonders

of sight and perception

and the catastrophes that ensue when things go wrong.

In his new book, The Mind's Eye, Sacks goes back to his own childhood,

and finally owns up to a lifelong inability

to recognise or remember faces.

It's been about three years since I've seen Sacks.

Having read about his severe face blindness,

I was wondering if there's any way that he'd recognise me.

When I came in right now, I was laying bets

as to whether you would recognise me or not.

How did you know it was me as I came in?

Erm...

Well, I didn't.

I experimentally said, "Nice to see you again,"

to the...to a plausible person, which happened to be you.

So, Oliver, I'm going to give you a little test here.

-I was afraid of that.

-All right, here's the first.

Do you recognise that person?

Erm...

I know I should, because otherwise you wouldn't be showing it to me.

Erm... Er...

She is young, she is black, she is famous, so I would infer,

I would think there's a good chance of it being Obama's wife.

OK, that's the first bit. Now here's the next one.

I don't know, no idea.

OK. Do you know who that is?

He's from a slightly unusual angle,

but I would think that that's the husband.

-That's a good way of putting it, the husband of whom?

-Of Obama's wife.

That's the husband of Obama's wife? Well, you done well there, that's true.

-That's one you've got right.

-I'm sorry, not two right?

No, you didn't get the first one right. Now what about this one?

Well, she's grey-haired,

she has an imperious look, I would guess, the Queen.

So you've done not badly.

-It was Elvis Presley who you hadn't recognised.

-I see.

And did you show me both Obama and Mrs Obama?

-No, I showed you Oprah Winfrey.

-Oh, yeah.

-You got Obama and the Queen.

OK.

Is it a strain not being able to recognise people?

Well, sometimes it's a relief! No.

People can be greatly offended and I think one needs to

out oneself in this respect to sort of diffuse situations.

And since I wrote on the subject, I've had lots and lots of letters

from people who have said they had something similar,

it had been lifelong and other people in the family had it, and I got the sense

that here was something not uncommon out there in the general population.

Face recognition is crucially important for humans,

most of us are able to identify thousands of faces

or easily pick out a familiar face in a crowd.

But severe face blindness is estimated to affect

at least six million people in the US alone.

There's a particular part of the brain,

towards the back of the right hemisphere,

which seems to be especially concerned with the recognition of faces.

There's argument as to how much this particular area

is a product of evolution and present at birth

and dedicated to the recognition of faces and how much it develops

through training and culture, because, of course, we're a social animal

and facial recognition is very essential for us.

At two-and-a-half months,

babies respond to smiling faces by smiling back.

This engages the mother to smile more, to talk, to hold the child.

In other words, to initiate the process of socialisation.

We interact in the world with the people we know and love

through the recognition of their faces.

So people with face blindness have to learn to be resourceful.

They find strategies, such as recognising people by an unusual feature, spectacles, facial hair,

a certain sort of clothing.

Then there's voice, posture or gait.

And, of course, context and expectation.

And Oliver's problem is not just confined to recognising other people's faces.

I often start apologising to a, er...

a large, clumsy, bearded man,

and then realise that it is a mirror.

Once, when I was at a table outside a cafe,

and I turned to the window next to me

and I started checking myself, checking my reflection,

but then I realised the reflection was not doing what I was doing,

but that on the other side, there was a puzzled man with a beard

who wondered why I was feeling myself in front of him.

So I can take others for myself as well as myself for others.

'But is there any circumstance, I wondered,

'where a deficit like this can be turned into an advantage?

'The New York-based painter Chuck Close is one of the world's most successful artists.

'His work sells for millions of dollars,

'but, like Sacks, Chuck Close has been face blind since childhood.

'Chuck also suffered a spinal artery collapse in his forties,

'and he's relied on a wheelchair ever since.

'But he continues to paint with a brush strapped onto his wrist.

'I've known Chuck for years.

'I spent time with him at his studio in New York,

'where I've watched him work.

'But I had no idea he was face blind.

'He never mentioned it, and I never noticed anything unusual.

'I only found out when I read about him in the footnotes of Sacks' latest book.

'It had been a while since I've seen him,

'so I wondered if Chuck would recognise me.'

DOORBELL BUZZES

-Hello, Alan.

-Chuck!

-How are you?

-I'm good.

How have you been?

-It's so good to see you.

-Great to see you. How are things?

-It's good.

-You're looking good. I like that look.

-Getting a little more hair.

-So tell me, honestly...

-Yeah?

Did you immediately recognise me, or did you just know...?

I knew you were here.

-That's not the same thing!

-No, it's not.

-When we first met a few years ago, and I spent days with you...

-Days, yeah.

I thought you'd never leave.

But you never told me.

Most people in my whole life never noticed

that I wasn't remembering their names or recognising them,

even though it was a tremendous struggle.

It came to some of my best friends as a total surprise.

But it is a nightmare.

It's one of the reasons why my stomach is tied in knots,

and why I'm a nervous wreck.

It takes a tremendous amount of energy.

When did you first realise?

When I go back to your childhood and think about that moment

when you had learning problems,

you found it difficult to absorb information.

As long as I can remember.

I remember being in kindergarten or first grade,

and I still, by the end of the year, didn't know who my classmates were,

and I also didn't know their names,

so between not recognising who they were or what their names were,

I was in big trouble.

-Did you realise that was unusual?

-Oh, yes.

'Yes.

'My mother was especially concerned, as you might imagine,

'and I went to see a lot of doctors.

'They had no explanation for it.'

Even learning disabilities didn't exist in the '40s.

'Overlooked at school,

'Chuck developed an early love for theatrical and creative arts.

'He eventually gained a place at Yale's art school,

'and emerged on the New York art scene in the 1960s.

'This was the time of abstract expressionism and pop art,

'but Chuck Close went against the grain.

'He painted huge realist portraits for which he's become famous.'

There is a wonderful irony or compensation

that someone who is so blind to faces is such a master at portraying them.

I wouldn't be a portrait painter had I not had face blindness, I'm sure.

'Every aspect of my work was determined by my disabilities and deficits.

'And that's driven everything that I do.'

Now, if you move your head half an inch, it's a whole new head.

-Perspective and angle changes, you see something completely different?

-Yeah.

It's like watching some organic process.

It's like looking at a...

at a bag full of cats or something.

It's going to poke out here, poke out there. Here, there, whatever.

It's going to constantly be changing its shape.

Most people, I think, see the continuum, see how it stays the same.

I think I see how it's changing, and how it's changing

somehow gets into my head and makes me think I'm seeing a new image.

'Whilst the rest of the '60s New York art scene was creating a collective movement,

'Chuck was a loner, making his art and dealing with his condition.

'But his work has evolved since those early realist portraits,

'though the basic technique remains the same.'

'He approaches the human face through a grid,

'breaking the face down into small square sections,

'and, most importantly, working from a flat image.

'Ironically, he's turned to abstraction

'in order to make sense of the whole,

'only gradually building up an image of the face.'

'I'm overwhelmed by the whole.

'I don't even know how you'd approach it as a whole,'

so I break it down into small, bite-sized decisions.

'The person is revealed only when you step back.'

'It is then that the face becomes recognisable.'

'These images are more than art works to Chuck.

'He only paints portraits of family and friends.

'This is how he remembers them.'

'Chuck Close has spent his entire career

'using his art to help him deal with his inability to recognise faces.'

'Vision is so complicated,

'it takes half of the brain to process what we see.

'Light, motion, shape, memory,

'context, are some of the things we take for granted.'

Vision is not seamless,

that although one might imagine one is given the visual world

with colour and depth and movement

and boundaries and contours and meanings all there,

in fact there must be many, many discrete elements,

any one of which can be knocked out.

'The consequence of just one thing going wrong

'demonstrates how many different elements are involved in the way we see.

'Take reading, which we take for granted,

'and we assume is connected with writing.

'But reading is, in fact, based on our in-built potential for shape recognition,

'and a separate process to writing.'

As Victor Hugo, the French poet, put it,

"Have you noticed how picturesque the letter Y is,

"and how innumerable its meanings are?

"The tree is a Y, the junction of two roads form a Y.

"Two converging rivers, the glass with its stem,

"the lily on its stalk, and the beggar lifting his arms are a Y."

'In January 2002, Sacks received a letter

'from the Canadian crime writer Howard Engel.'

At last!

Nice to meet you. I can see you like books, Howard!

Well, is there anything else?

-Come on in.

-Thank you.

'Engel was not just a bestselling author, but an avid reader, too.

'His house is full of books. Every surface is covered in books.

'They're his treasures.

'But this all changed one morning in 2001,

'when Howard woke up and realised

'his world didn't look the same as it always did,

'and his library of treasures had become useless to him.'

'It was a day like any other day.

'I got out of bed, came downstairs,

'and went outside to bring in the morning paper.'

'Took a look at the morning paper,

'and suddenly it seemed to be written in Serbo-Croatian

'or Cyrillic, or some kind of alphabet that I didn't recognise.'

And immediately I thought, "Somebody's having me on,

"there's a joke here,"

so I looked at an inside page to see how far they had carried the joke.

'They had been miraculously changed, as well.'

Then I started getting worried and I started looking at other things.

Everything that involved print had been changed into something unrecognisable.

And at the same time, that's what shocked me,

was that everything else looked exactly the way it normally looked.

The view out the window, the things in the kitchen,

everything looked as I expected it to look, except for print.

As soon as I decided that it wasn't a prank

and somebody wasn't joking with me, I knew that I'd had a stroke

and that I'd better get myself to the hospital.

Howard was told that his stroke had affected the visual parts

of his brain on the left side.

He spent the next week in the neurology department

at Toronto's Mount Sinai Hospital.

During this week,

Howard's memory suffered other disorientating symptoms.

It was a nurse that informed him that even though he'd lost

the ability to read, he could in fact still write.

I tested it, of course, because I didn't believe it to begin with.

Then I found that if I wrote something down,

I could read it immediately.

If I looked at it five, ten minutes later,

I'd have to sound it out word by word.

When you discovered that you could write, but you couldn't read,

you said, "It was like being told that the right leg

"had to be amputated, but I could keep the shoe and the sock."

Which I thought was...

So, you were bereft, really.

It was as though my library had been cleaned out

and suddenly there was all that empty space.

Being robbed of Dickens and Hemingway at the same moment,

it was difficult to fathom, to say the least of it.

He found himself unable to read and yet he can write,

explain that to me.

Much more of the brain is involved in writing than in reading.

There's a particular area which becomes specialised for visual reading.

They call it the Visual Word Form Area.

But you do not need to visualise letters to write.

One can write perfectly well with one's eyes closed.

The action of writing has independent neurological basis

from visual perception of letters.

Surprising as it may seem,

reading and writing are controlled by different areas of the brain.

And because Howard's stroke irreversibly damaged

the part of his brain used for reading,

he'll never be able to read in the same way again.

But this hasn't stopped him.

Since his stroke, amazingly,

Howard has painstakingly taught himself to read...

in an entirely new way.

Originally, when he looked at a page,

which might be visually unintelligible to him,

he would find himself, sometimes unconsciously,

copying what he saw with his finger.

-The shapes?

-The shapes of the letters.

This way, he was reading with his finger.

But now, this has gone a stage further

and he is reading with his tongue,

moving his tongue so that it copies the shapes of letters,

and doing this on the back of his teeth.

And this is an amazing example

of one sense moving in for another, and of human adaptability.

Did you just discover that procedure for yourself?

Yes, no one suggested it, no. It just seemed to come naturally.

I think it's evolved to simply making loop-to-loop figures with the tongue.

Although it's slow, so it may take him a month to read a book

which he would have read in a couple of nights, he can do it.

Although he mentioned to me fairly recently

that he had inadvertently bitten his tongue, while he was eating,

and he had a sore tongue, and with that,

became functionally illiterate for two weeks,

until the tongue got better.

Before his stroke,

Howard was famous for his Benny Cooperman series of crime novels.

Remarkably, only months after losing the ability to read,

he began work on another novel in the series,

which has become his most popular to date.

Writing was one of the things I could still do, so I continued writing.

Howard used his own experience as inspiration,

but he did change one crucial detail.

Private detectives don't have strokes.

That's one of the rules,

you have to hit a private detective over the head

to get him into the same position

that a stroke serves for the rest of the population.

It was the ancient Greek physician, Hippocrates, who famously said,

"It's more important to know what sort of person has a disease

"than to know what sort of disease a person has."

It's this thinking that has inspired Sacks throughout his career.

OK, nice to meet you.

'I am a neurologist.

'I explore disorders of the human brain and nervous system.

'But my approach has a particular emphasis.

'I am as interested in the person affected by a disorder

'as I am by the disorder itself.'

Now, erm...

Erm... Thanks.

Oliver Wolf Sacks was born in London in 1933,

the youngest of four boys.

Despite being obsessed with chemistry as a child,

he decided to follow the rest of his family into the medical profession.

After earning his medical degree from Oxford University,

he moved to America.

His first job was at the Beth Abraham Home For Incurables.

This is where his real love affair with his patients began.

It's here that he met survivors of the sleepy sickness pandemic.

Sacks gave them the drug, L-Dopa, which famously brought them

out of their catatonic states for a brief time.

Their stories became the subjects of his book, Awakenings,

which later inspired the Oscar-nominated film.

You describe yourself as a physician and a storyteller,

and, of course, that's what has captivated people.

Well, I love stories and storytelling,

and my parents, especially my mother...

My mother was a very good storyteller

and things would ray out from the particular surgical problem

or pathology, to the person and their social situation,

and I would see her talking to the gardener,

or the dustman, and enchanting them.

She was a sort of Ancient Mariner. She would hook people with stories.

It all starts with stories.

You came from a huge family, and your mother was a surgeon,

which was unusual for the time.

How many doctors were there in your family?

Both my parents were doctors, and as I was growing up,

my two older brothers were medical students.

Were cases discussed at the table?

Constantly, in a way which we, the four sons, loved,

but which, I think, sometimes terrified,

or appalled or disgusted strangers.

My mother, in particular, was a very good storyteller,

but somehow things would get synchronised

so that the puss would go with the soup.

And I partly learned brain anatomy through eating at that time,

which was long before mad cow disease, when one ate calf brains.

My mother would say,

"That finely structured thing, that's cerebellum, try it."

Since Sacks became a neurologist he's written 11 books

which have been translated into 24 different languages.

He receives hundreds of letters every year from all over the world.

This is a lady with musical hallucinations.

With the help of Kate Edgar, his close friend and assistant,

he goes through all of them.

Do you find people come to you as a last resort?

They think that maybe you will be able understand their predicament?

Yeah, I think they do, and it's sometimes heartbreaking,

because it seems to me

they've already seen all the best people, and very good people,

and all sorts of solutions have been attempted and tried,

and I may have to write back saying,

"I don't have any magic, I don't think I can help." And, um...

This, for example, was the situation when some years ago,

I got a letter from an artist who described having become

suddenly, totally colour-blind,

unable to perceive any colours,

following a head injury in a motor vehicle accident.

For him, the challenge, as an artist,

was to live in a suddenly black and white world.

But trying to show me what things were like,

he designed an entire room set up for a banquet, as he saw it.

And...I see Kate gesturing.

What are you gesturing for?

Because what we have here is a bowl of fruit painted by him.

Ah!

Oh!

So, the one thing I retrieved from his black and white room

and banquet was the fruit.

He said, "You want to know what it's like? It's like this."

And at that point, he found his world very ugly.

He didn't know how he could go on as an artist.

But then, a change occurred with him,

and what had been, for him, such an impoverished and abnormal

and ugly world, became a different sort of world.

Delicate and fine, not spoiled by garish colour.

15 years ago,

Sacks travelled the world for a BBC series called The Mind Traveller.

He met various people with all sorts of conditions, many of whom

he'd studied over the years and subsequently written about.

BOAT HORN BLARES

You feel a deafening noise, how do you sense it?

One of these case studies was Danny Delcambre.

Just feel the vibrations.

At the time Sacks filmed with Danny,

he was running a popular Cajun restaurant in Seattle,

but this was no ordinary restaurant.

To all appearances, it was just like any other good Cajun restaurant.

Spicy food, sizzling pans, enticing smells.

Yet there was something different about the place.

Everyone was communicating in ASL, American sign language.

The waitress gave Danny orders in ASL.

The customers were chatting in ASL.

I like your hearing aid, it's a nice colour.

The Ragin' Cajun was a restaurant for the deaf.

Danny is originally from Louisiana, which has the world's highest

concentration of a rare genetic disorder called Usher Syndrome,

a condition Danny was born with.

Usher syndrome destroys two of the senses, hearing and sight.

So Danny was born deaf, and would eventually go blind.

Right now, this is about my vision, a square. I'm limited to this.

When I become fully blind, I don't know what that will be like.

As Danny and Maria describe their failing sight,

I try to imagine what the future could hold for them.

What would it be like,

no longer being able to see all the beauties of nature around them?

Within ten years, Danny will be virtually blind.

Danny has since moved an hour and a half outside of Seattle.

I went to meet him.

And with the help of an interpreter,

found out what had changed for him over the last 15 years.

1996 was when the BBC came, and Oliver Sacks,

and we made the documentary, which was a very enjoyable,

interesting experience to do.

My goal had been to run the restaurant for about ten years.

That had been my plan.

I actually made it nine.

At that point, I sold the business,

and wasn't sure what I was going to do next,

if I was going to go into something else, or what.

About that same time, I met my wife, we got married,

and lo and behold, we began a family.

It started to make sense for me to be the stay-at-home parent,

to become what we call, Mr Mom.

You guys hungry?

Since they married, Danny's wife Debbie has learned sign language.

And the children, who are unaffected by Usher syndrome,

also talk to their father through basic sign language.

I did everything - the diaper changing, the feeding, the works,

playing with the children as they've grown.

And, oh, my goodness, that is a busy job.

I hadn't quite realised it, it is not an easy task.

I'm just interested to know where Danny's Usher Syndrome is today?

In this room, for instance, what can you see around us?

It's a pretty small tunnel. Looking at the interpreter, I can see...

I can't see anything on either side of her at all,

but I can see from her shoulders, inside of her shoulders,

most of her face, and down just the top of her chest,

sort of that area, that little circle or square.

And from this distance, this is a good distance for me.

If she were to come closer, I couldn't see enough of her.

But I'm functionally blind in the right eye, I have light perception,

but that is it, it's basically all dark with a little pinpoint of light.

And then at night, or if the light is dim, I'm basically blind.

He's still got...

He's still got some vision.

I was wondering, yes. It's probably very, very narrowed.

Very, very narrowed indeed.

And yet, there's a sort of optimism in Danny,

as his wife acknowledged to me, that he's not really prepared to concede.

Yes, perhaps there's all the difference

between a little vision and no vision.

He's a very resilient person, has a lovely sense of humour,

but he will always have language.

Even when he can no longer see, one can have sign-language on the hand.

When Sacks filmed with Danny, he met a whole community of people

with Usher Syndrome at a summer camp.

Here he witnessed the deaf-blind for the first time

and how they communicated with tactile sign language.

Denied sight as well as hearing,

these people were talking with touch.

I'm amazed at how much can be got sometimes

from just apparently feeling the wrist of the signing hand.

It's obviously a complete communication.

What else has so fascinated me has been the hunger for communication,

the hunger for language.

The world which can't be directly perceived,

which can't be seen or heard, must be narrated.

You can sometimes forget how central language is to being human.

You may have to come to deaf people, especially these Deaf-Blind people

to see that human beings can't live without language,

can't live without communication, and they will create it somehow.

As Danny's sight fails, he's relying more and more

on tactile sign language.

He'll eventually only see through touch.

But whilst he still has some vision left, he's taken up a new interest.

Of all things, photography.

As I watched him photograph his children,

I realized it helped him see things clearer.

He could capture a still frame

of something that most of the time was blurred.

He was capturing what he loved, things worth seeing

and honing in on.

He told me how he spent hours in his garden,

photographing details of flowers and the wildlife.

All small, beautiful creations.

Some of my favourite shots

are of the hummingbirds out here in our backyard.

I have to tell you, it was a trick figuring out

how to take a picture of a hummingbird, because they move

and I didn't want them just at the feeder

because that's just not natural,

I wanted them at the real flowers so I would just wait

and wait and wait and hold very still and, lo and behold,

I got some very nice shots.

Some of them very close where you can really see those long, long beaks.

I wasn't very good at it at first but now I've got some really,

really beautiful pictures.

Have you transferred your love of cooking to your love of photography?

Yeah, a little bit. That's what happened, I think.

Whether I could ever make a business out of it, selling my pictures or what not, I don't know.

I'm seeing in you, Danny, a camera-obsessive.

I think that's right. Yes. And I'm fascinated at some of the cameras you all have here, my goodness!

They far outstrip anything I could afford at this point.

I left Seattle surprised yet again by the resilience

of human beings and the resources they can command

both individually and communally.

At times, not knowing sign-language,

I had felt that I was the only impaired person there.

But the greatest revelation was the beautiful language of touch.

I would not have thought that touch alone

could be an adequate instrument for understanding a language,

but I was mistaken.

Yet, perhaps I should not be astonished.

The human brain, after all, is the most wonderful

and adaptable creation in the universe.

We are sensory creatures, it's how we make sense of the world,

and evolution has played a big part

in shaping our perception of what's out there.

The brain of all animals evolved to see the world

in a way that was most useful for survival.

For our primate ancestors,

the ability to distinguish reds and oranges

and thus the ripest fruit and leaves, was a huge advantage.

So colour vision developed in primates

where it's absent in most other mammals.

Similarly, forward-looking eyes allow good depth perception,

vital for swinging through the trees.

In general, prey animals have to have a panoramic vision

and be on the lookout for attackers anywhere.

Predatory animals need to focus in. Some animals have both.

My favourite, cuttlefish, and there are pictures of cuttlefish

all around the place. I am very fond of cuttlefish,

but cuttlefish eyes are usually set up for panoramic vision.

But when a cuttlefish goes in for the kill,

the eyes can be rotated around and then you have a big overlap of the visual fields.

And stereo vision and then they shoot out these tentacles.

And no fish will escape them then.

Stereo vision has its benefits for us, too.

It's our principal way of perceiving depth.

This is achieved by our two eyes receiving subtly different images.

The brain and then takes these images

and in a way that's still not fully understood,

mysteriously fuses them into one.

This is how we perceive depth.

I think you should put the glasses on, Sue.

When most of us view the world we see depth

and three-dimensionality.

But when we go to the cinema and see a 3D film, depth is exaggerated.

This is a novel experience for Sue Barry.

Whoa!

It's only in the last few years

that she's been able to see the three-dimensionality of 3D films...

-..And perceive depth in her everyday life.

-It's wonderful.

The beaks and everything!

Well everything is kind of on top of me now.

The scenes with the rifles coming out and so on.

It just pops out right at you, plus things go further back in space as well.

So it's like, wow, look at that!

So in a sense, for you, this 3D experience,

that's what the world out there is like for you?

That's right. That's right.

Every day it's sort of like a 3D movie and I'm constantly surprised.

I get a sort of butterflies-in-the-stomach kind of feeling.

-Like a whole visceral response.

-Mm.

-My whole body reacts to it.

It's like, "Wow! Look at that! It's different."

'Because Sue was born cross-eyed,

'she saw a very different view through each eye.

'This created a confusing double vision.

'So her brain adapted by taking in information from only one eye at a time,

'rapidly switching between the two.

'This meant Sue had no stereo vision -

'her world was flat and two-dimensional.

'As a child, she had operations to realign her eyes

'but it didn't change the way she viewed the world.

'It was still flat.'

Basically, when I looked at something in the past...

Let's say I was looking at your face.

I would see your face in detail

and that stuff behind you, would just sort of appear in one flat plane.

And now, everything's in layers and layers and layers of space.

'Sue grew up and became a neurobiologist.

'Then, in her late 40s, something remarkable happened.

'Sue acquired stereo vision.'

So what really surprised me was that everything was in 3D.

The whole world was in 3D. Even things that look ordinary were suddenly extraordinarily different.

Take, for example, the bumper of this car.

It's really coming out at me. It's popping out at me - boom! Like this.

I never saw it that way before.

Sure, I knew the bumper of the car was in front of the dashboard.

I could tell from various other kinds of cues,

but to actually experience it,

to have this real sense of it - boom - popping out at me,

was really different to the way I'd seen the world before.

-Was it quite shocking, in a way?

-It was.

I kept looking at things, like doorknobs or sink faucets,

all of a sudden, like, popping out at me,

and I would always do a double-take.

'In 1965, two Nobel Prize-winning scientists, Hubel and Wiesel,

'experimenting with kittens, got results that suggested

'that if a child's cross eyes were not realigned within one or two years of birth -

'the so-called critical period, that child would always lack stereo vision.

'Sue, the neurobiologist, was familiar with this research,

'and was reluctant to tell anyone about her own extraordinary breakthrough.'

I was afraid they would say, "Oh, it's impossible!

"You must be delusional. You must making it up."

Or, "So what's the big deal? If I close one eye,

"the world doesn't look all that different."

The reason why you can do this, cover one eye,

and the world won't look different is that you've always had stereo vision,

so even if you momentarily close one eye, your brain fills in the missing stereo information.

But if you've never had it and then you acquire it,

after half a century of living, it is a major revelation.

So I thought about this for about...

almost three years, and finally one night,

when I thought I was just going to burst, I sat down with my laptop

and I pounded out a letter to Oliver Sacks, because I thought

if anybody might at least read my letter and consider my story,

maybe it would be Dr Sacks.

Well, I was fascinated by her letter and I asked if I could visit.

I love extended house calls, getting a letter which excites me

and then going off on a sort of neurological adventure.

I confess I was a little doubtful.

I wondered if she could be kidding herself.

I took some pictures which gave no clue other than stereo to their depth.

She did well with this and I was convinced this was the genuine article,

and we went for a walk and this was a lovely example, in a way,

of the innocence of vision, almost a child's vision,

now being experienced by an adult who never had it before.

So Sue was absurdly delighted by everything.

When I first began, let's say, to see a tree in 3D,

the outer branches circle around and capture whole volumes of space

within which the inner branches permeate.

To me, that was a completely novel revelation.

In the past, trees just looked sort of flat, like they would

in a children's drawing, even though I knew they weren't flat.

Knowing and seeing are completely different.

People who have stereo don't know what they have,

and the people who don't have stereo don't know what they're missing.

As many as 500 million people worldwide,

for one reason or another, have little or no stereo vision.

For Sue, it wasn't initially a conscious decision

to try and acquire it.

As far as she was concerned, she never could.

But then, in her late 40s,

she started getting other problems with her vision.

I'll just have you look straight ahead.

So she booked in to see a developmental optometrist.

I went to see Dr Theresa Ruggiero when I was 48 years old,

not to develop stereo vision

but because my vision had become so jittery.

If you have two eyes and both of them are taking in information,

which was the case for Sue,

but they're not both taking in information at the same time,

what you have is a constant rivalry or sort of competition

between the information coming into the eyes.

And that creates instability and confusion.

So now look at the middle bead.

Having assessed Sue's vision,

Dr Theresa Ruggiero spent a year working with Sue,

doing simple vision exercises again and again

until Sue could master them.

The aim of these exercises was to teach Sue's brain

to see through both eyes at the same time, something she had never done.

Many people have, and many children will have, surgery to try to correct that, just as you had surgery.

So why doesn't surgery solve it?

Surgery alone is not enough because what it does is it disconnects

and reconnects the muscles of the eyes, but without that information being provided to the brain.

The problem is not muscle-based, the problem originates up here.

It's a brain problem. And so what has to happen is you have to work

with the visual pathways that control where the eyes are aiming.

For a year, Sue worked on various simple yet highly effective

vision exercises until she could, without thinking about it,

fuse the images from both eyes at the same time.

This stopped her jittery vision and gave her something

the rest of us take for granted - three-dimensional stereo vision.

You're taking those two different sets of information

and fusing them and seeing it as one combined image.

-Do you see that?

-Yes.

So you're seeing a virtual image.

Show me with your hand where it seems to be in space.

-That's where it is.

-Yeah, exactly.

-In fact, how dare anyone say it isn't?

-Yeah, exactly.

And the fact is it's all going up here.

That's right, vision is a brain process, vision does not happen in the eyeballs.

That the tip of the iceberg, the eyeballs.

Every week for about a year I would pass this tree and,

with each passing week, it became more and more three-dimensional.

So this tree was almost like a barometer of the change in my vision.

It's such a spectacular tree.

And you'll also notice, as you move, you get an increase in that sense of three dimensions.

That is due to something called motion parallax.

After I gained stereo, I found myself spending a lot of time doing

just what we're doing right now, which is just rocking back and forth under a tree

and enjoying all the depth that I could see.

-Do you know, I could get used to this?

-Yeah.

It's something we could do well into retirement.

After her initial reluctance to tell anyone,

Sue is now very open about her new stereo vision.

She even contacted David Hubel.

He's since followed Sue's case with great interest

and continues to explore the implications of her

development of stereo vision nearly 50 years after the critical period.

In contrast to Sue,

Sacks was acutely aware of his stereo vision from an early age.

As a boy, he loved using stereo viewers,

and as soon as he discovered photography

he was taking stereo photographs and experimenting with making his own viewers.

Even as a school kid, I would sometimes be caught closing one eye

and then the other and asked what I was doing.

I said I was seeing how the world flattened.

And I was told to spend my time more usefully,

but I loved playing with stereoscopy and making hyper stereoscopes.

I think I partly fell in love with America books

of stereo views of the Grand Canyon and Yosemite.

So this is a View-Master, which must be very familiar to you from your childhood.

I adored them.

You can have a look.

I think we've tried to get some great American views for you.

OK. Well, there's some very beautiful mountains,

snow-covered with a lake in front of them.

I would wonder whether it was a volcanic lake.

This is the American west or the north-west.

This is what I fell in love with.

The old days, if I looked through this I would have seen

the lake moving away

and the mountains palpably further away.

I would have been intensely conscious of the space between the foreground and the far ground,

whereas now it's all flat.

Six years ago, Oliver developed a large blind-spot in his right eye.

He went to see an opthalmologist

and his worst nightmare was confirmed:

he had a malignant tumour.

Despite radiation and laser treatment,

Sacks eventually lost all sight in his right eye,

and with it the stereo vision that he'd cherished since childhood.

Given how much you relish that stereo world,

how are you coping without it?

There is an overwhelming sense of loss,

and I occasionally have dreams

in which it seems to me that I have stereo,

in particular the dreams, I am looking into a stereoscope.

And when I wake up and see the fan in my bedroom

about to hit the bedside lamp, I know they are 6ft apart

but for me they are transposed and conflated onto the same plane.

and I miss stereo,

not so much in my day-to-day functioning as just

in the richness and beauty of the world.

So you have your stereo vision in your dreams then?

I think I do, in so far as one has any descriptions of dreams

that are reliable. I think I've had it in dreams and I think

I've had it, or a hallucination of it,

when I've smoked some pot.

-You'd better smoke a bit more pot then!

-Perhaps I should.

Oliver Sacks is now 77.

He still sees patients and publishes a new book every couple of years.

He loves plants, cuttlefish and the periodic table.

He swims almost every day and has done so for decades.

Subtitles by Red Bee Media Ltd

E-mail subtitling@bbc.co.uk