NARRATOR: Too often,
we take our bodies for granted,
but under pressure,
our bodies can show us
how extraordinary
they truly are.
This complex machine grew
out of millions of years
of evolution.
So intricate,
we're still mystified
by many of the things
going on inside us.
A hidden world,
but one we can now explore
in 3-D as never before.
Our sight relies on the most
complex system in our bodies.
Using three-quarters
of our brain power'
when we're challenged,
our eyes focus on the smallest
detail at lightning speed.
They allow us to see
in the dark'
even to see to the magic
of the impossible.
Our brain allows us to see
even while we sleep.
And someday, we may be able
to see without our eyes.
That's how extraordinary
our sight truly is
when we're pushed to the limits.
[ Siren wailing ]
[ l ndistinct talking on radio ]
A murder suspect races
through downtown Los Angeles.
[ Tires screeching ]
Pursuing him is LAPD officer
Stan Berry.
What he's got to do
in this superfast world
is to figure out what matters
and what doesn't
at 1 00 miles an hour.
MAN: 1 4, there's two occupants
in the car.
[ Horn blares ]
NARRATOR: And to keep up with
the suspect without crashing.
BERRY: l need to know about
the traffic to the right of me,
traffic coming
to the left of me.
But you also need to focus
on what's ahead of you.
ls there pedestrians
walking down the street?
And then also try to keep up
with the fleeing suspect'
as well.
NARRATOR: Nature designed the
eyes to let him do just that.
Sight guides the human body.
[ Tires screeching ]
[ Siren wailing ]
NARRATOR: Many animals
have special kinds of vision.
But in humans, we can do it all.
Like no other creature on Earth,
our vision can distinguish
around 1 0 million colors...
[ Horn blaring ]
...switch focus from infinity
to mere inches
in a fifth of a second...
... pinpoint detail
in the brightest sunshine
or darkest shadow...
...take in a wide-angle view
of almost 1 80 degrees.
All of this takes the massive
power of the human brain.
in some way subserve
the visual system.
lt's been given
an extraordinarily high degree
of emphasis
by all the mechanisms that
have gone into its creation.
[ l ndistinct talking on radio ]
NARRATOR: Human eyes function
as survival sensors,
giving us essential information
at the crucial time.
Berry constantly relies on them.
The eyes' mechanics are
the most complex in the body.
Their intricacy is unmatched.
As a ball, the eye pivots
in all directions,
locking onto moving targets.
lt does so with the help
of unlikely allies --
two cups of fat -- shock
absorbers for the eyeballs.
Light enters through an aperture
in the iris,
an elastic mesh
of interlocking fibers.
l n bright light' it snaps down
to the size of a pinhole
in a fifth of a second.
Light hits the lens --
not a hard disk'
but a bag of fluid.
The lens projects an image the
size of a large postage stamp
onto the retina
at the back of the eye.
Then the retina'
a mass of nerves,
sends impulses to the brain.
Surprisingly, the right eye
signals the left side
of the brain,
and the left eye transmits
to the right side.
Our eyes have evolved
a crucial feature
that still keeps us
from going extinct.
Officer Berry is about to test
that feature to its limits.
Speeding into a dangerous
intersection,
he faces questions literally
involving life or death.
[ Engine revving ]
ls anything moving?
Where is it?
What is it?
[ Siren wailing ]
A vehicle is stopped ahead,
blocking the way.
To the right' a car speeds
toward the intersection.
On the left'
a third driver about to move.
[ Horn blares ]
But suddenly,
something else comes into view.
And here's where
the human eye's design pays off.
At the back of the eye,
most of the retina consists
of millions of rods.
These cells see no color
or detail.
But let anything anywhere
in our field of view move,
and the rods spot it.
The eyes swivel
to look directly at the vehicle.
Now other cells at mid-retina
kick in.
A pinhead-sized dot holds
six million cells called cones.
They're all about color
and detail.
DR. D'AM l CO: That's why,
when we look at something,
we look directly at it --
because we have
our highest visual acuity
right in the center.
NARRATOR: Locking his eyes
on the moving object'
Officer Berry can judge speed,
direction, and danger.
The brain responds,
sending signals
at an amazing 1 80 miles per hour
to his hands and feet in time
to clear the intersection.
[ Horn blares ]
[ Siren wailing ]
This is one of hundreds
of life-or-death decisions
that Officer Berry makes
to bring the 40-minute chase
to a safe end.
[ l ndistinct talking on radio ]
He does this thanks to the eye's
incredible skill at adjusting
when information threatens
to overload what we're seeing.
This ability matters
as much today
as it did for our ancestors.
Evolution left us
with another skill,
one that's still priceless.
l n the dark'
we can make out the world
with only the smallest
of clues.
The will to live through a fire
depends on our skill
at navigating the murderous
darkness of smoke-filled rooms.
Firefighters reach a house
in Bradenton, Florida.
Agent 56, go ahead
and charge the line.
NARRATOR: But they don't know
if anyone's trapped inside.
l'm set.
Ready?
NARRATOR:
Now firefighter Dan Fleming
enters a dangerous world
of shadows and shapes...
...so murky and cloudy,
you'd think it impossible
to see anything.
Dan struggles to build a picture
of the whole house
from frag ments he makes out
in the haze.
[ Heavy breathing ]
How is the house laid out?
Where is the fire?
Are there any survivors?
You're trying to determine
what the house looks like,
what the occupants are about'
who would be inside this home.
NARRATOR:
Despite the darkness,
Dan's eyes im mediately start
to adjust.
They have amazing sensitivity.
l n complete darkness,
from 1 4 miles away,
we can detect the light
from a single candle.
You try to find bits and pieces
of light
to help you
find your way through.
[ l ndistinct talking on radio ]
NARRATOR: l n low light'
we rely on the rod cells
that cover most of the retina.
Highly sensitive, they only
register black and white.
But Dan needs to see in color.
He's searching for a fire.
FLEM l NG:
lt was very faint at first.
l thought to myself' "That must
be the seat of the fire."
very orange glow --
l mean, it was really orange.
NARRATOR:
To see color'
you use cone cells
at the retina's center.
We get all our color vision
from being able to distinguish
only three colors.
SADU N: The cones are sensitive
to different colors.
There's those that are
particularly sensitive
to blue light' those to green
light' and those to red light.
And they need a lot more light
to fire.
So if they get enough of
the photons of the right color'
they fire and say to you,
"There's a spot of green
or red or blue at this point."
NARRATOR: Using these red,
blue, and green signals,
the brain creates an impression
spanning the entire
visual spectrum...
...a range
of over 1 0 million colors.
[ l ndistinct talking on radio ]
Color vision leads Dan
straight to the fire.
FLEM l NG: To my surprise,
it went out very quickly.
And l started scanning around to
see what else was in that room.
Whenever you can get glimpses,
that's so important'
but l'm taking the whole room in
as l'm scanning.
NARRATOR:
l n a flash,
Dan's brain calculates
what has to be there,
even though he sees
only tiny frag ments.
This is what our brains do
constantly --
fill gaps with data
from our visual memory bank.
l n fact' our brain interprets
most of our vision
out of a lifetime
of stored images.
Then Dan recognizes something.
A white shape --
a cup of coffee.
Black and white squares --
a half-completed crossword.
Are these crucial signs
that someone could still be
in the house?
There, through the smoke,
Dan sees a blurred
and unusual shape.
FLEM l NG: My initial instinct was
there's something on the couch.
l'm not sure what it was.
Requesting backup!
We have a saying --
When in doubt' check it out'
and that's what l did.
Give me a hand!
l got a victim!
Get the gurney in here, guys.
NARRATOR: Dan Fleming has used
his brain's visual memory
to transform a blur
into the outline of a body,
saving a man's life.
The power of human sight
comes from millions of years
of evolution.
We can't even understand it.
And technology today can't begin
to match the sophistication
of our incredible eyes.
But for the first time,
science is pushing human vision
to new limits
by connecting directly
with the brain's vision center.
This means that one day,
we might even see
in the invisible worlds
of infrared, have X-ray vision,
or plug video games
straight into the brain.
Cheri Robertson from Missouri
is about to step
into this virtual world.
l was in a car accident
when l was 1 9 years old.
l was a passenger in the car.
And the driver fell asleep at
the wheel, and we hit head-on
with a small truck'
and both of my eyes
were just destroyed.
NARRATOR:
Hoping to regain her sight'
Cheri volunteers
for a pioneering procedure.
lt involves marrying technology
to the huge processing power
of the brain's visual cortex.
lt was a chance for me
to be able to see again
when the doctors had always told
me l would never see anything.
NARRATOR: Cheri is about to have
an extraordinary experience.
Doctors drill through both sides
of her skull,
exposing her brain.
Then they implant
two triangular plates,
each holding
directly onto Cheri's
visual cortex.
Finally, the surgeons
string cables
from the plates to terminals
sticking out of her skull.
Next' the electrodes run
through a computer
to a camera
on Cheri's eyeglasses.
All of this technology
is designed
to help Cheri regain some sight.
ROBERTSON: lt was, l guess,
quite a shock for me
when l felt my head
and l felt these terminals
sticking out behind my head.
'Cause l guess
l really wasn't expecting that.
NARRATOR: But for her to see
what the camera sees,
many things have to happen.
And that requires a step
into the unknown.
Each electrode touches a
different part of Cheri's brain.
When the system triggers
an electrode,
she sees a flash somewhere
in her visual field.
Where, the doctors don't know.
Now.
NARRATOR: So they trigger
each electrode one by one
to learn where in her visual
field Cheri sees flashes.
MAN: Now.
ROBERTSON: Oh, wow.
That was right there.
Okay.
NARRATOR:
When she sees a flash,
Cheri points to top, bottom,
left' or right.
[ Beeping ]
With every electrode mapped,
the doctors connect the camera'
making certain that what it sees
matches the flashes
in Cheri's brain.
ROBERTSON:
Yeah. Right in the same spot.
So it works for us.
NARRATOR: Finally,
with the camera mounted,
Cheri's mother helps connect the
gear to try the new settings.
WOMAN: Ready?
l think my computer
gained weight.
[ Laughs ]
NARRATOR: Has technology helped
bring Cheri's sight back?
Oh!
Wow!
Oh, wow.
[ Laughs ]
Oh, wow.
When l finally saw my first
light' it took my breath away.
l could not believe it.
We knew it worked,
and that was very,
very thrilling for me.
Oh, something's lighting me up.
NARRATOR:
We can't know what Cheri sees.
But we do know
what she describes.
Whoa. l'm seeing
two big dots of light.
And they are white with
a little bit of red in them.
Wow. Those were two really big
flashes, and they moved.
Wow. l saw a big flash
of light there.
NARRATOR:
This early in the project'
doctors have activated
only some of Cheri's electrodes.
Eventually, they hope to connect
many more,
vastly improving the scope
of her vision.
Oh, wow.
Because l can only use 1 0
of my electrodes,
whenever an object goes
in front of my camera'
l will see two flashes of light.
And they're about the size
of a big peanut M&M --
just one on top of the other.
Saw a couple more.
l'm not sure if it's the waves.
And that way, l know
that there is an object there.
Now, l'm not sure what it is.
They're sailboats?
ls that it still here?
That is cool.
When l am able to use
all of my electrodes, however'
l will be able to see
the outlines of things
l'm looking at.
So l'll know if l'm looking
at a tree or a person or a car.
So l'll actually know
what l'm looking at.
NARRATOR: No one pretends
that Cheri's vision is back.
But the fact she can sense
any of the visual world
makes her
an extraordinary pioneer.
l magine if one day we could feed
complete vision signals
directly to the brain.
What could we see?
We might see a world
that we've been blind to,
as if we were seeing
through night-vision lenses,
infrared cameras,
even X-ray vision.
l magine a sum mer weekend
on a California beach
dense with bodies.
But for one onlooker'
this seemingly calm scene
may be a series of accidents
waiting to happen.
How does a lifeguard know
when a raised arm means,
" l need help "'
not' "Hey, this is fun"?
The guard's skill at spotting
that one desperate person
among thousands is phenomenal,
truly testing his sight
and understanding.
We see the way we do so we can
spot danger to ourselves.
l call!
NARRATOR: But nothing
is threatening the lifeguard.
l n fact' the eye,
observing a harmless pattern
across its view,
normally relaxes.
Motion-sensing rod cells
switch off
when they detect action
that's consistent and constant.
So the lifeguard
has to trick his eyes.
He does this by scanning,
forcing his eyes to lock
onto small details.
TU RN ER: Our frontline defense
are the tower guards.
Their job is to scan the water'
so their eyes are moving
across the water
and letting their brain filter
out that information they see,
looking for something wrong,
looking for that odd one out
that truly is in danger.
NARRATOR: Taking in all
this information is hard work.
Human sight has only two degrees
of detail vision at the center.
To check the whole beach,
the lifeguard sweeps...
...jumping from point to point
for detail.
Each jump is called a saccade.
A saccade is the movement
that the eyes make together
when they're looking directly
at one thing
and all of a sudden,
they look at something else.
We have mechanisms that wire
the muscles that move our eyes
to the image.
And we can quickly lock
onto a new image all at once.
NARRATOR: The saccade function
lets him jump visually
from each potential risk
to the next.
He repeatedly scans
his field of vision,
updating his visual memory
every few seconds.
But even more is going on as
he uses another complex skill --
interpretation of detail.
KAF ORD:
Being a seasoned lifeguard,
l can recognize distressed
victims in the water'
whether they look
really labored,
whether they're comfortable
or not' by their body language.
Those are sort of indicators
that allow you to recognize
a rescue before it happens.
NARRATOR:
The muscles rotating our eyes
give us an astounding breadth
of view.
Even while perfectly still,
we can rotate our eyes
from far left to far right
in a quarter of a second.
So when a riptide
suddenly overcomes a swim mer'
Drew knows within moments.
Now he has to judge whether the
swim mer can get back to shore,
whether he's too far out
for a rescue attempt'
or whether' despite the riptide,
Drew has a chance
of reaching him.
That split-second call demands
an accurate sense of distance.
We have two eyes, and they're
separated by this distance,
and that permits each image
to be slightly different
than the other image.
And that slight dissimilarity
gives me a sense
of how far away something is.
NARRATOR: We constantly judge
shifting distances,
hardly giving the process
a thought.
But this special process
only occurs
in humans and other predators
for spotting and catching prey.
That's the hunting skill
the lifeguard uses
to home in
on the struggling swim mer.
We can all find the detail
we need in a busy scene
when it's for our own safety.
But when guarding the lives
of others,
that same skill requires
training and intense focus.
l n day-to-day life, we fill in
parts of the passing picture
as our visual memory
makes shortcuts and assumptions,
putting together a picture of
the world that seems complete.
What happens when
those assumptions prove wrong?
That's where we get the phrase
"smoke and mirrors "'
the tools of visual confusion
illusionists use
to exploit the science of sight
to fool our vision.
Movies present spectacular
sights and grand illusions.
This is a movie set'
but how big?
[ Alarm blaring ]
What looks like a space station
on an alien planet...
MAN: Cut!
NARRATOR:
... is a trick.
WOMAN:
NARRATOR:
A tiny model near the camera
and a full-size stage
further away.
Film makers are essentially
the masters of illusion.
Here we see the two actors.
We assume
they're in a massive set'
because we don't have
the ability
to think' "Hold on a second.
This is just a small set'
and the actors
are a considerable distance
away from it."
MAN: Cut!
visual illusions trip up
the perceptual system,
the system
that is normally right.
Here we're exploiting
the loopholes,
when suddenly,
we're very, very wrong.
NARRATOR: l llusions exploit
how we see the world.
They rely on the difference
between what the eye sees
and what the brain understands.
Magicians have always relied
on this delicate confusion.
Hi, there.
[ Echoing ]
l'm Marco Tempest.
l'm a magician.
Now, here's a little
optical illusion.
Now, let me show you just
how easy it is to fool the eye.
l have a three-dimensional
object right here.
And l also have
a two-dimensional object'
this paper disk.
Now, if l place
this three-dimensional object
next to
the two-dimensional object'
something very strange
is happening.
Check this out.
lt looks like
the two-dimensional object
has become three-dimensional.
But if we get rid
of the three-dimensional object'
something else is happening.
Check this out.
Do you see?
The cube now looks like
it's completely two-dimensional.
All right.
Here we go.
NARRATOR: From another angle,
the secrets reveal themselves.
l also have
a two-dimensional object'
this paper disk right here.
Now, if l place the...
NARRATOR:
Underlying the trick
is a genuine
scientific principle,
explaining how our brains
build a three-dimensional
visual world.
Check this out.
This is all about
how we read perspective.
The three-dimensional cube,
once established as being
three-dimensional,
stays three-dimensional
in our minds.
Even when we look
at the taped lines,
it still looks three-dimensional
to us.
lt's almost like our eye
fills in the missing information
and wants the object
to be three-dimensional.
And that's where l get you.
All right.
NARRATOR: Our world is filled
with visual information.
The brain copes
by creating shortcuts,
relying on experience to fill
gaps with informed guesswork.
Light and shadow.
The size, shape, and distance
of objects.
We assume the world operates
according to fixed rules.
But sometimes
we're just plain wrong.
Take this ordinary-looking room.
l look to be much, much larger
than Sarah.
And this isn't camera trickery.
l nstead,
it's an incredible illusion.
Because when l'm in this corner'
Sarah suddenly looks much,
much larger than me.
Now, in reality, the two of us
are roughly the same size.
lt's all to do
with the amazing way
in which this room
has been constructed.
NARRATOR:
Not regular in shape at all,
the room has a bizarre geometry
that's disguised as normal.
We see square rooms so often...
...we fool ourselves
into thinking this is one, too.
lt's amazing
how easily our eyes get fooled.
We see an umbrella' and we
im mediately think of rain.
But on a beautiful day
like today...
[ Echoing ]...we don't
really need an umbrella.
NARRATOR: Magicians exploit more
than our assumptions
about the objects and spaces
around us.
You're about to see
what looks like a simple trick.
But it has a deeper'
more elusive level.
Welcome to the color-changing
card trick'
using this blue-back deck
of cards.
Now, the idea is very simple.
l'm just going to spread
the cards in front of Sarah
and ask her to push any card
towards the front of the table.
SARAH: Okay.
l'm going to go for
this card here.
Wl SEMAN:
Excellent.
Sarah could've chosen
any of the cards in the deck'
but she selected the one
which is now laying facedown
on the table.
l'm going to ask her
to look at the card
and tell us what it is.
The card l chose was, in fact'
the 3 of clubs.
Wl SEMAN:
The 3 of clubs. Excellent.
That comes back into the deck.
l'm now going to spread
the cards faceup on the table.
A click of the fingers,
and Sarah's card
still has a blue back.
What's more surprising
is that all of the other cards
now have red backs.
And that is the amazing
color-changing card trick.
NARRATOR: But this trick really
doesn't involve cards at all.
lt clearly shows
how the brain picks up
only a tiny bit
of the available
visual information.
l n fact'
as the trick was occurring,
four other color changes
went on.
Welcome to the color-changing
card trick'
using this blue-back deck
of cards.
NARRATOR: As the trick unfolds,
the camera stays on the cards.
...which is now laying facedown
on the table.
NARRATOR:
Most of us don't notice changes
in clothing and background
made off-camera.
The color-changing card trick
exploits this idea
that we have a very good idea
of what's happening
right in front of our eyes.
l n fact' 90% of that information
we're just not seeing.
lt doesn't feel like that.
lt feels like,
as we look around,
we're perceiving the whole
of the world.
That's not the case.
We really are only just focused
on a tiny, tiny area.
NARRATOR: l llusions are about
more than entertainment.
They reveal how what we see
depends on assumptions
our brains make.
Our eyes and brain collaborate
to make sense of the world.
But our brains need years
of training
before they can turn
what our eyes see
into a meaningful image
in an instant.
F ollow a blind man as he uses
his eyes for the first time,
and hear him describe
what his brain can see.
Michael May has undergone
radical surgery
to repair eyes ruined
in a boyhood accident.
He hopes that when
the bandages come off'
he'll be able to see
for the first time in 40 years.
MAY: l didn't expect
anything to happen
for at least a couple of weeks.
So to go into that room and
have the bandages peeled back
and then to actually
see light coming in
was more than words
can really describe.
All of a sudden,
there's the overwhelming whoosh
of visual input'
things resolving into colors
and shapes,
images whooshing everywhere.
NARRATOR:
Rebuilt eyes allow light
to reach Michael's retinas.
First thing you should see
is your wife.
NARRATOR:
But Michael has a problem.
After 40 years in the dark'
his brain doesn't recognize
what his eyes can see.
vision wasn't as simple
as just turning on the sight
and all of a sudden
being able to read a book.
lt's much more complicated
than that.
vision isn't something
where you flip a switch.
Come here, baby.
NARRATOR: So, what visual sense
will Michael have
of a world he hasn't seen
in 40 years?
Once blind,
Michael May's repaired eyes
now work almost perfectly.
But surprisingly,
he can hardly see.
The reason is the age
at which Michael lost his sight.
A freak chemical explosion
at age 3 blinded him.
[ Monitor beeping ]
an experimental procedure
to restore his sight.
Doctors replaced a key part
of the eye
destroyed in the accident'
his cornea.
This clear' paper-thin coating
protects the eye
and helps it focus.
The damage to Michael's eyes
kept him from making out
anything.
He hoped that new corneas
would mean another chance
to see the world.
...you should see is your wife.
NARRATOR:
But 40 years of blindness
left him with a larger problem.
MAY: l was trying to
latch on to images
and make sense of the world.
lt wasn't as though l saw a face
and said, "Oh, that's a smile "'
automatically.
l had to intellectualize
this whole process,
dissect it'
and then figure it out.
NARRATOR: Michael May has
no visual memory of the world.
Are you making a funny face?
NARRATOR: lt's not something
we're born with.
At birth,
everything we see is new,
but we archive the images,
learning their content
and meaning.
We build our visual memory
through experience.
At the back of the brain,
over half a billion brain cells
make up our visual cortex'
the processor and storehouse
for vision.
Early in our lives,
we build our visual memory.
And as long as we live,
that library helps us
make sense of the world.
SADU N :
The interpretation
and therefore the recognition
of certain things
takes a tremendous amount
of experience.
l n this sense,
the brain is learning to see.
And this is taking place
over the first six years
or' to a smaller extent'
even the first nine years.
NARRATOR: But when Michael
was blinded at 3,
he'd only just started
to understand the things
that make up his ability
to see.
Size, shape, and distance,
light and shade.
MAY: ls that a curb, a step
down, a step up, or a shadow?
Just in terms of the brain's
ability to analyze the depth,
to see the edge and to realize
that there's a 6-inch drop
to the curb, l'm just not able
to perceive that information.
lf he had spent
a childhood seeing
and playing with his bicycle
and riding off curbs
of different sizes,
he would have learned subtle,
different cues
that lets him distinguish
between a 3-inch curb
at one distance,
a 6-inch curb a little further'
and a 9-inch curb
further than that.
Deprived of that experience,
it gets to be very hard to do so
on an optical basis alone.
NARRATOR: Now Michael's
adult brain has to struggle
to catch up on the learning
it missed as a child.
But Michael does recognize
and enjoy some things.
MAY: l'll use a cane to deal
with what's in front of me.
And then l can look around
and appreciate the things
that l can perceive --
bright-colored flowers,
landmarks, people walking by --
things like that
that l can use my vision for.
And l don't even think
about what's in front of me.
NARRATOR: Michael May inhabits
a weird world
between blindness and sight'
frustrated by his lack
of visual memory.
F or most of us,
this same visual memory
unlocks another universe,
the world of dreams.
When you're in a dream,
that is your reality.
You visually are seeing things.
You are hearing things.
You can literally feel things.
You can see your body moving,
et cetera.
And you can experience anything
that you would experience
in waking life in a dream.
NARRATOR: Dreams consist
of images we've collected
with our eyes.
Like a film editor'
the brain reassembles them.
M l LLER: l'm usually
on my stomach with my arms out'
kind of like Superman,
and l'm gliding
over different sceneries.
l find it a bit of a high to go
in between, dodge the buildings,
and go fast
and go up and down and over.
l feel like a bird soaring
in the air.
l've always wished l could fly.
NARRATOR: l nterestingly, many
people share the dream of flying
and endure the nightmare
of being pursued.
The brain can create
utterly realistic scenes,
even though
we've never experienced them.
WOMAN :
Someone's following me,
and l have this urge
to just run away.
MAN : l started running away
from it' seeking higher ground.
WOMAN #2 :
He was faster than me.
WOMAN #3: But l ran into
the back door of the hospital.
NARRATOR: Reports of such bad
dreams recur throughout history,
and the meaning
of these night visions
has always fascinated us.
compiled a book of dreams.
lt listed familiar dream images
and offered interpretations
of them.
DR. PARKl NSON :
Dreams were a sort of moment
when the boundaries between
this world and the next world
seemed very thin.
But for many of the dreams
in the dream book'
it's clearly a search for
what will happen in the future.
NARRATOR: Now we explain
bad dreams as useful
in helping us conquer deep,
often universal fears,
just as we see good dreams
as fulfilling our fantasies.
Sights seen in dreams
may well connect us
to our ancestors' instincts
and fears --
yet another example
of how our sense of vision
has always dominated our lives.
Our visual system shows
better than any other
how intricately our bodies work.
Throughout history, it has
supercharged human development'
and it could allow us
to take charge of our future.
Sight dates back
to our deep past --
unsung, unnoticed,
a faculty we take for granted.
But when revealed, sight shows
how everyday life depends on it.
Pushed to the limits, we can see
the superhero inside us all,
the human body.