Is Seeing Believing? Horizon

Welcome to the strange and wonderful world of illusions.

Baa. Baa. Baa.

Illusions to deceive your eyes.

So I do take cheques.

Trick your tongue.

And fool your sense of touch.

Oh!

But don't worry, it's all in the name of a noble scientific quest.

These illusions hold the key to how our senses work.

When you open your eyes in the morning,

most people think, "I'm seeing the world as it is".

The beautiful thing about illusions is they tell us that that's not true.

They show us that our perceptions of the world are something different

from seeing it as it really is.

Illusions are providing a unique window into the inner workings of our minds.

Helping to reveal what our sensory brains are really capable of.

So this is a golden age in perceptual psychology.

The things we've learned over the last ten years have been absolutely phenomenal.

These new discoveries are opening up a whole new world of possibility.

Even enabling us to move beyond our sensory evolution altogether.

So watch, play along, and prepare to be amazed at what your senses can do.

Can you trust anything you see with your eyes?

Do you think seeing is really believing?

The beautiful thing about illusions is that they make us realise

things are not always quite as they seem.

So the question for you is, you see the surface here and the surface there?

Right? Do they look the same in terms of their colour.

That's what you see, they look different.

What if I told you that they're actually the same. Will you put money on it?

Would you bet your life on it?

You wouldn't be standing here, would you?!

-Do they look the same now?

-That's mad, ain't it?

-It looks it.

Are they the same physically?

To our amazement and delight, illusions are so powerful

that even when we know how they work we can still be fooled.

But for scientists like Dr Beau Lotto, they are far more than fun and games.

Now, how many people see four blue tiles on the left?

Yes? I see four blue. How many people see seven yellow tiles on the right?

I see seven yellow.

What if I told you they're all grey?

So if I take, for instance, this tile, what colour is it now?

Grey.

If I move it over here,

what colour is it now?

Yellowish grey.

So those tiles are all physically the same.

Illusions are crucial tools that reveal how the world out there

can be very different to the one in our heads.

And it's this gap between reality and what we perceive that holds the key to how our senses work.

So if you're unsure if seeing is really believing, you're not the only one.

Is seeing believing?

What do you mean by that?

Is seeing believing?

Is seeing believing?

No.

Yes.

I think it depends who you ask.

Seeing is literally believing.

We see what we believe.

So, yes.

So it's this question of whether seeing really is believing that's

helping scientists to open up the fascinating world inside our heads.

And one of the places they are turning to for inspiration is an ancient and untapped source.

Magic Singh is a master of illusion.

His livelihood depends on his ability to confuse, trick and deceive.

It's something magicians like him have been doing for millennia.

But now scientists want in on the act.

Magicians have developed

really powerful ways of manipulating what we see.

And many of these techniques have been tried and tested in front of live audiences.

So by doing so, magicians have sort of developed

a very solid understanding of how we see the world.

Psychologist Gustav Kuhn is well versed in the language of illusion.

In a former life, he was a professional magician.

Today he's swapped the magic circuit for the science lab,

but he's convinced there are some important lessons

to be learnt from plundering the magician's book of tricks.

So actually take the card out.

We're really interested in the magic tricks per se,

but what we focus on is the techniques that magicians use to manipulate your perception.

OK, I'm not going to put the eye-tracker on you, so if you could just wear these glasses.

In order to find out how these illusions work, Gustav Kuhn has developed

an eye-tracking experiment

to enable him to find out what's happening when we watch certain tricks.

Now in the vanishing ball illusion, the magician tosses the ball up a couple of times and then on the

final throw, he just pretends to toss the ball up in the air.

Yet most people actually experience an imaginary ball

leave the hand and then sort of disappear somewhere up there.

But when Gustav analysed his data,

he discovered the eyes and the brain told a very different story.

Now, the eye-tracking data showed us that whilst most people were fooled by the illusion,

the eyes weren't tricked.

So the eyes, rather than actually looking at the imaginary ball, just stayed on the face.

And what this showed us is that the illusion really happened in people's minds.

What this trick really demonstrates is that, rather than seeing what's physically present,

the way we see the world is based on our prediction of the world.

So we see things that we expect to see, so in this case,

we expect the ball to leave the hand, and that's why

we actually see the ball, even though physically it's not actually present.

When it comes to what we see, the brain often overrules the eyes,

even constructing events that may not have actually happened.

It's an important insight into how our visual system operates in the real world.

In the real world things happen incredibly quickly and we have to

respond at great speed and accuracy to visual information.

This information processing may take up to 150 milliseconds,

and that kind of delay would just be far too great for us to miss,

for example, catching a ball or so.

So rather than just relying on this information, what the visual system does,

is it predicts what's going to be happening in the future.

So in many ways, what we see is what's going to happen in the future rather than in the present.

So seeing may not always be believing.

But is our sense of hearing any more reliable?

At any one moment, we are being bombarded by sensory information.

Our brains do a remarkable job of making sense of it all.

It seems easy enough to separate the sounds we hear

from the sights we see.

But there is one illusion that reveals this isn't always the case.

Baa, baa, baa.

Have a look at this. What do you hear?

Baa, baa, baa.

Baa, baa, baa.

But look what happens when we change the picture.

Faa, faa, faa.

Faa, faa, faa.

-Faa, faa...

-And yet the sound hasn't changed.

In every clip, you are only ever hearing "Baa", with a B.

Baa, baa, baa.

Baa...

It's an illusion known as the McGurk effect.

Take another look.

-Baa, baa...

-Concentrate first on the right of the screen.

Now to the left of the screen.

-Baa, baa...

-The illusions occurs because what you are seeing clashes with what you are hearing.

In the illusion, what we see overrides what we hear,

so the mouth movements we see as we look at a face

can actually influence what we believe we're hearing.

If we close our eyes, we actually hear the sound as it is.

If we open our eyes, we actually see how the mouth movements can influence what we're hearing.

Baa, baa, baa.

It's a bizarre effect.

Remember, the only sound you're hearing is "Baa", with a B.

Faa, faa, faa.

Baa, baa, baa.

What's remarkable about this illusions is

even knowing how it's done doesn't seem to make a difference.

The effect works no matter how much you know about the effect.

I've been studying the McGurk effect for 25 years,

and I've been the face in the stimuli,

I've seen stimuli thousands and thousands of times, but the effect still works on me.

I can't help it, the speech brain takes in that information

and doesn't care about what outside knowledge you bring to bear.

Baa, baa, baa.

The McGurk effect shows us that what we hear may not always be the truth.

It also helps us to understand what happens when our senses conflict.

Baa, baa, baa.

When the brain has the conflicting information,

it tries to make sense of that conflict,

and depending on what type of modality is providing more, I guess, salient information,

that information might override or at least combine with the other information.

So we can't always trust what we hear because sometimes our sense of vision takes over,

enabling us to maintain a coherent view of the world.

But why do illusions have such power?

Scientist are finding answers in the most surprising of places.

For bees, colour is a matter of life and death.

They need to distinguish between colours to find the source of their food.

And the way bees learn this important lesson can offer us insights into how we perceive.

One of the great things about studying bees is that bees see colour much the way that we see it.

They see the same illusions that we see, yet they do it with only a million brain cells.

Which means that we can actually study how bumble bees see

and in doing so we can understand how we see.

Dr Beau Lotto has devised a unique experiment known as the bee matrix,

where he uses 64 coloured lights to represent flowers.

The aim of the game is to find the sugar reward.

We are training the bees to go to blue flowers, as opposed to purple flowers,

and the way we do that is we reward only the blue flowers,

reward being sugar water, and we don't put any reward into the purple flowers.

So if they land on a blue flower, they get a reward.

And then they associate that with the colour.

In the top part of the array we have blue flowers surrounded by white flowers, in the bottom part of

the array we have purple flowers also surrounded by white flowers.

Only the blue flowers have a sugar reward.

At first, the bees quickly find their reward by learning the difference between the colours.

But then things are made more difficult.

Using filters, Beau changes the colours, so now the blue and purple flowers look exactly the same.

But remarkably, the bees still fly straight to to the reward.

So as far as the bee's eye is concerned, those are exactly the same.

If the bees only remembered the colour of the stimulus,

they should go to both, because they're physically the same.

If, however, they've remembered the blue flowers in a context

and used that context, they should now go only go to the top.

What we've shown is that that's exactly what happens, which means they are using the context.

They have remembered and learned the relationships between the colours to solve the puzzle.

So, to solve the puzzle, the bees don't just look at the colours in the middle

they also look at the colours that surround them.

And it's by comparing the central colours to those on the outside

that they are able to detect the true colour.

It shows that, for bees, colour isn't just seen in isolation,

it's entirely dependent on the environment in which it's perceived.

And what applies to bees also applies to us, every day of our lives.

Here we have two cubes, except in this case

it looks as if the cube on the left is under yellow light,

and the cube on the right is under blue light.

On the left we have four blue tiles, and on the right we have seven yellow tiles.

What's amazing about this illusion

is that the blue tiles on the left are exactly the same, physically,

as the yellow tiles on the right.

They're all in fact grey.

So in this instance the brain has created colours that simply aren't there.

When the other colours are stripped away, we can see the blue and yellow tiles are just grey.

Put the scene back, and the colours change back to yellow and blue.

It shows that, in spite of our strongest instincts, colour is a purely subjective experience,

governed by the context in which we see it.

Redness is not a product of the world.

It doesn't exist unless we're there to make it.

Blueness is not a part of the world, wavelengths are not colour.

All they are is little packets of energy called photons, they are not colour.

We take that and we make perceptions of them, and those perceptions guide our behaviour.

Illusions fool us because, try as we might,

we cannot overcome our experience of how we think the world works.

It's these experiences we store in our heads that really determines what we see.

What's amazing is that that information, coming from the eyes

through the thalamus to the back part of the brain,

actually only makes up 10% of the overall information we use to see.

The rest of the information comes from other parts of the brain.

Only 10% of the information we use to see comes from the eyes.

But are these experiences only built up in the course of our own lives,

or are some illusions so powerful

their roots lie far in our distant past?

Janine Spencer and husband Justin O'Brien are hoping to find out

if seeing certain illusions is learnt in the course of our lives

or hard-wired from birth.

It requires several babies, and a great deal of patience.

Anybody who studies with babies will know they're notoriously difficult,

not because they're hard in themselves, they're lovely,

I love having babies in the lab, but we can't ask them anything.

There is a number of reasons why it takes such a long time to get baby data,

pretty normal reasons.

They cry, they get hungry, they don't like what they're looking at,

they want to move, they don't want to sit in their car seat,

so there are a number of reasons and because of that,

we have to test lots of babies to get enough data.

BABIES CRY

In order to find out they are using a famous piece of visual trickery

called the hollow mask illusion.

One side of the mask is hollow, but it doesn't necessarily look that way.

Even when we know it's an illusion, we see it as the convex face.

Even when we know it's hollow our visual system sees it, we interpret it, as being convex.

Essentially, our knowledge of faces is overriding what our visual system can see,

so our depth perception can see that it's hollow,

but our visual system is overriding that and saying, "no".

Not in those words,

it's unconscious of course, but that's a face, so it must be sticking out.

They've been testing the hollow mask illusion on babies at just four and a half months of age.

I think it's important to study babies to look at visual illusions

and any phenomenon where you want to find out if it's innate or not,

because they don't have that kind of experience we would get as adults.

The younger you can test them, the better it is.

It's known babies are good at recognising faces, but the question is,

do they still see a face when they look at the hollow side of the mask?

By carefully monitoring their eye movements, it's possible to detect if the babies see the illusion

by the way the mask captures their attention.

We measure the amount of interest the baby has in the experiment by looking at their eyes.

We monitor their eye movements and we time how long they look,

and when we get to a certain level where they're not looking very much at all,

we know they're bored of the experiment.

It's still early days, but 50 babies later a pattern is beginning to emerge.

From the data we have so far, it would suggest that babies can see the illusion,

giving an indication that face perception is an innate ability.

If this pattern continues, it will be the first significant evidence to suggest that seeing

certain illusions is so powerful it's an ability we've inherited from our parents.

What's exciting for us about the results we're finding at the moment

is that it doesn't just tell us about the way babies see, it tells us about our evolutionary past.

The experience of our ancestors of seeing faces and them being so necessary for survival

is now written into our DNA, so when a baby's born,

the first thing they'll look at and show interest in is a face.

The hollow mask illusion helps explain why seeing illusions may have come about in the first place.

We've learnt to see what best aids our chances of survival.

In our evolutionary past, it's important to see faces

because they could be our enemy.

It's also not just human faces, it's animal faces as well,

so we're very good at seeing animal faces.

So something staring at you through the trees could be a tiger,

so it's important you interpret something as being a face.

If it turns out to be a pattern of leaves in the sunlight, you haven't lost anything.

If you ignore it and it really was a face, then you're in trouble.

For Janine and Justin,

over five years of infinite patience is finally paying off.

Yes, very pleased, we need more babies but we're very pleased with the results we have so far.

It's only taken five and a half years but we're nearly there.

Illusions show us that we literally see the world through the lens of the past,

learning to see in the way that's most useful to us.

It's an ability that's so important

it's been handed down through the generations for thousands of years.

So if you thought being tricked by illusions was a weakness, then think again.

They may seem to be just a bit of fun, but it turns out they may be the key to our success.

So what if I told you they're exactly the same?

-Oh, my God.

-So, I do take cheques.

You just lost so much money!

Many people think that illusions in fact demonstrate the fragility

of the human senses, which is in fact completely rubbish.

Illusions don't tell us that our senses are fragile.

If they were, we wouldn't be here. Illusions tell us that actually,

our brains are incredibly capable of constructing meaning

from the meaningless. We're really good at doing that.

If we were to process all of the information

that we feel that we're aware of,

we would have to grow huge brains

and have massive heads that our bodies would just fail to support.

Rather than using this approach, we've evolved to, I think,

a very clever attentional system that only processes the information that is actually needed.

So, far from being a disadvantage,

illusions are a necessary and powerful shortcut

that lie at the heart of our most sophisticated human abilities.

And yet the insights we can get from illusions don't end there.

Scientists are now realising that illusions get even more fascinating

when the senses start to work together.

One of the things most of us can hold on to is that our five senses work separately.

We see with our eyes, hear with our ears,

taste with our tongue and touch with our skin.

But scientists have been studying a group of people

for whom this just isn't the case.

So when I hear the sea,

the big clunkiness, as it were of the wave,

has a kind of dark, dark blue.

And the pebbley bit has kind of oranges and yellows

and little bits of white.

I heard the wind earlier and it had these kind of long shapes,

a bit like, you know, mackerel fillets.

You know those shapes, but a bit... The little thin ones.

Like that, but blue, and quite a lot of them going across.

I have synaesthesia,

which means when I experience taste, smell, sound,

I get visual images.

Shape, colour and texture to accompany the sense.

Synaesthesia is a mixing of the senses.

A sensory experience in one sense can trigger an entirely different reaction in another.

Whenever Philippa hears, smells, or tastes something, she also sees colours and shapes.

If I was to have fish and chips, the fish -

the crispiness, that's angular and then the actually taste

of the fish is kind of speckeldy brown.

Nice brown, but yeah, kind of coffee-coloured brown.

While this experience isn't always pleasurable,

it's helped drive Philippa's artistic creativity.

This is a painting of the taste of English mustard.

It has such a distinctive colour as it is as a product,

it's bright yellow, but when you taste it, to me,

it has this massive red hit, which then just disappears into something else

that ends up, by the time the kind of fumes of it

are going up through your nose, it's actually quite...pretty.

So it starts off as a big, massive red hit of taste, which then disperses into something else.

For years, synaesthesia wasn't taken seriously...

but now scientists are realising that people like Philippa

provide important clues as to the way all our senses work.

We're going to present you with letters and numbers.

They're, um, going to be coloured either red or green.

Dr Noam Sagiv has spent his career studying synaesthetes

in an attempt to understand how their brains are connected.

So scientists have suspected

for a long time that what causes synaesthesia is extra connections

between different parts of the brain, particularly between the sensory areas that are involved.

For example, if someone has auditory-visual synaesthesia,

we expect that the auditory part of the brain and the visual part of the brain would be cross-wired.

And this understanding of how their brains are wired has led to

an exciting new idea about the way all our senses develop from birth.

OK?

-That's it.

-I got one wrong.

What we do know is that the brains of newborns are actually a lot more connected than the brains of adults.

We start our lives with a lot of connections in our brains and we lose some of them.

One of the ideas that is trying explain the difference

between synaesthetes' and non-synaesthetes' development

is that essentially, synaesthetes were able to keep

a little bit more of those many connections that we all started our lives with.

So this condition might have been something we've all had at one time in our lives, but since lost.

But the similarities between synaesthetes and the rest of us may not end there.

Scientists are now beginning to suspect that even as adults,

we may have far more in common with synaesthetes than we realise.

I can't imagine what it would be like to be alive

without it...

because it doesn't impose itself, it's just part of my being.

So I...

kind of don't believe that

people don't have it.

I think they're just not looking hard enough.

And this question of the way our senses are connected

is being answered with the help of another set of bizarre illusions.

Neuroscientist Charles Spence has recruited some willing volunteers for an unusual multi-sensory feast.

He's taken his science out of the lab and is going to attempt to trick

a group of trainee chefs, who rely on their senses more than most of us.

OK. You've got four coloured drinks in front of you and what I want you to do is to taste each one

and try and figure out what the flavour is.

The colours and flavours of the drinks have been mismatched,

resulting in a certain degree of confusion.

Just looking at some of the expressions on their faces, you can see confusion and puzzlement.

One of the people thinks that the yellow drink is apple.

It was actually strawberry.

And the red one, they smell like berries, but in fact was lemon.

I think the green one tasted more of lime.

Like lime cordial or something like that, rather than mint.

OK. Excellent.

Green lime, so it's completely lost the peppermint flavour

-and it's being completely driven by the eyes.

-The light green actually

reminded me of green washing-up liquid rather than mint.

Lady's convinced it's washing-up liquid smell.

And that expectation and knowledge that comes

from names, from labels, from colours, from textures,

from ways of presentation, our brains use that all the time

to tell us what the flavour is.

People will talk about you eat with your eyes, which is probably much more true than we realise.

So it's impossible to separate what we see from what we taste.

But what may be even more surprising is that when it comes to what you eat,

your ears may be just as important.

CRUNCHING

This time the chefs are eating crisps,

but they are also hearing the sound of their own crunch via headphones.

But what they don't realise is the noises they hear have been changed.

When they hear low frequencies, they are tricked into thinking the crisps

are significantly less crunchy than when they hear higher frequencies.

When anyone thinks about flavour, the first sense they think about is taste.

To think about it a bit more, some people say, "Well I suppose smell's involved, too."

Then they start, possibly if pushed they'll say, "Well maybe colour's got something to do with it."

And finally a bit of texture.

Is it soft and slimy or crispy or crunchy?

But virtually no-one ever thinks about sound.

The results show hearing can have a significant effect on taste.

Just playing higher frequencies makes people believe crisps to be over 15% crispier.

But all this culinary trickery has even more insights to offer.

The reason these tricks work is because it's impossible to separate one sense from another.

It's experiments like these that have enabled scientists

to piece together a revolutionary new understanding of the brain.

The traditional view was that you had five senses on the outside,

and the eyes are connected to one bit of the brain, your ears are connected to a different part,

your skin to somewhere else.

Each sense had its own bit of brain.

What we find now is in fact, the eye is talking to the ear almost as soon

as those signals get from the eye and the ear into the brain.

From very early on, there are multisensory interactions at work.

Scientists are saying there is no such thing as a visual brain,

no such part of the brain that is just doing hearing.

All of the brain is multisensory, all of the brain is combining all the different senses, all the time.

So it turns out we are all far more similar to synaesthetes than we've realised.

It's clear we should no longer think of our senses

as working independently but as working together as one.

It's a discovery that has truly revolutionary possibilities.

-Hi. I'm Larry.

-Hi, Edie.

Very nice to meet you. We're going to do little demonstration here called the rubber hand illusion.

This illusion may look like fairground fun, but it reveals

one of the most important new ideas in brain science.

Right there.

Good. Can you put this hand down right over here, and curl it up like the rubber hand is curled up

a little bit. I'm going to try to position the rubber hand so it looks like it's your own.

-Could you imagine that being your own hand?

-Yeah.

We're going to stroke your finger simultaneously, the rubber finger and your real finger.

Hopefully this will convince you that the rubber hand is your own. Your brain will adopt this hand.

In the illusion, simply watching the rubber hand being stroked at the

-same time as the real hand is enough to trick the brain into adopting it as its own.

-We like weird!

And slowly but surely, you should feel that the hand you're looking at is actually part of your body.

It feels like you're touching my hand with that one.

Right, so it feels like this is your hand I'm touching, right?

-Are you OK?

-Yeah.

-Good.

Try that at home with your kids!

The rubber hand illusion is a wonderful example of how

multisensory perception can influence how we perceive our own body.

That's how deep multisensory perception runs.

When you hold your hand out, it's generally thought that you know it's there because of the information

you're getting from your muscles and tendons and that sort of thing.

The rubber hand illusion shows how that can be overridden by visual information.

The rubber hand illusion shows the powerful connection between what we see and what we feel.

But it reveals even more than simply the way our senses are connected.

It hints that a fundamental change in the brain is taking place.

Oh!

-Isn't that strange?!

-Yeah, that's creepy.

What might be going on in this illusion is that

the brain is actually changing to accommodate the new rubber hand.

Going through some sort of structural change that we call neuroplasticity.

Neuroplasticity is an exciting new idea that suggests the brain can change in response to experience.

And this is what's taking place in the rubber hand illusion.

The brain may be temporarily re-wiring itself to adopt the plastic hand as its own.

-It really feeling like it's your hand now, huh?

-Yes.

Is that a little weird?

-Yes.

-We like weird in perceptual psychology!

Here we go.

-Was that scary?

-Yes.

Good, we like that!

'Brain plasticity is a terrifically exciting'

sort of phenomenon for perceptual psychology.

I think the rubber hand illusion shows that.

That the brain can change, based on a new experience.

This is important for somebody, say, who doesn't have vision, to know that they can compensate

through plasticity with another sense and use that to navigate the world.

This idea of a plastic, flexible brain is so exciting

because of the phenomenal possibilities it contains.

Not only do our senses work together, but it suggests one could be used to replace another.

CLICKING

I lost my first eye at the age of seven months, and my second

at the age of 13 months, to retinoblastoma, which is a retinal tumour.

I have no visual memories at all.

CLICKING

Although Daniel is completely blind, he's developed a remarkable ability

to see, using his sense of hearing alone.

CLICKS HIS TONGUE

People do express surprise

at a blind person cycling.

I think different people are good at different things.

I was good at cycling but I wasn't much for ball sports.

Using the sound of his tongue clicks, Daniel has learned to echolocate, just like a bat.

Echolocation is just another way of seeing.

It's a way of seeing with sound instead of light.

You extract images from the patterns of sound as they reflect off the environment.

When Daniel clicks, the sound waves he produces bounce off nearby objects.

From the returning echoes, Daniel creates an image in his mind, which he uses to navigate the world.

It's an ability that's enabled him to overcome the impossible.

I could cycle without echolocating for a brief while, and then it would end uncomfortably.

It's kind of like they say,

"Falling is really quite a blast, it's the striking the ground that's the real bummer." So, yeah...

But Daniel can show us far more than what one extraordinary man can achieve.

His remarkable bat-like abilities are helping scientists reveal the hidden potential of the brain.

Professor Lutz Wiegrebe is an expert in bat echolocation, but now in Daniel,

he's been given the unique opportunity to study his first human subject.

Wow. That is very cool.

There's another one!

Today, Lutz is conducting a series of MRI scans,

to find out what happens inside Daniel's brain when he echolocates.

For me personally, this has been a really great experience, because I've been working on the

echolocation of bats and we've only recently started working

on echolocation with humans.

Having Daniel around is like almost being able to talk to a bat, and Daniel is not only exceptionally

good at echolocation, he's also exceptionally good at verbalising how he does it.

Inside the scanner, Daniel is hearing virtual echoes.

This should enable the team to see which parts of his brain

are activated when he echolocates in the real world.

Lutz suspects that when Daniel clicks, something remarkable may be happening inside his brain.

Even though he can't see, the sounds he hears may still be activating parts of his visual brain.

What we are interested in is so-called cross-modal plasticity, which means that these parts

of the principal visual cortex are taken over by auditory information.

Lutz is looking for evidence to show just how malleable the human brain really is.

Not only can experience temporarily change the brain,

but as Daniel seems to suggest, these changes can also be permanent.

It means that at the extreme

extent of...

the cross-modal plasticity on a perceptual level that Daniel

has demonstrated, he can really see with his ears.

That it's not only that he can process spatial information acquired with his auditory system, but that

he can also recruit parts of his visual cortex to do this task.

It's just a demonstration how

plastic the system is, and how intelligently it's designed.

If one part of the brain has really no input any more because

of a sensory deprivation, then this part can be taken over by other modalities.

As unique individuals like Daniel seem to show,

the human brain can change and adapt in the most phenomenal way.

This has implications not only for people whose senses are impaired,

it has the potential to affect us all.

For Dr Angus Rupert, finding a way of replacing one sense with another has been a lifelong ambition.

It's something that for his colleagues at Fort Rucker Aviation Centre in Alabama

could mean the difference between life and death.

Since 1990 alone, we've lost between ten and 30 pilots and air crew per year,

just due to spatial disorientation.

These are the figures across our army, navy and air force.

We define spatial disorientation as occurs whenever a pilot misperceives

the position, motion or attitude of his aircraft, relative to the Earth or other significant objects.

In other words it's, "Which way is up?"

In normal circumstances, pilots can correct the problem of spatial disorientation by using their eyes.

But there are instances when they can't always rely on what they see.

When you are flying, there is no way for you to know where down is

unless you are actually looking at the horizon

or looking at an indicator

to give you the information in the aircraft.

But Angus Rupert thinks he has found the solution.

It comes in the form of the Tactile Situation Awareness System, or TSAS,

which uses touch to support or replace the sense of vision.

Together with research pilot John Ramiccio,

they've found a way of giving pilots spatial awareness by using a series of vibrating pads called tactors.

So, in this situation we have John wearing tactors incorporated into the shoulder harness.

These are the ones telling him if he is too high.

In the seat we have tactors letting him know if he's getting too low

as well as tactors around his waist here.

And you can see these tactors

giving information as to which way he is drifting in space.

So confident are they in how the system works, it's being put to the test

on a pilot who will attempt to fly with his eyes completely closed.

So it's at some risk that we are not successful

but that's the essence of science, is to experiment

and so this is raw...

and un-attempted-before footage.

We will have Captain Wingate close his eyes, and use the tactile cues to land

the helicopter so he is going to be fully reliant on feel for spatial orientation.

I would like you to take off down the runway.

Do you feel the upper tactor fire?

It's your shoulder harness telling you that you're above 100 feet, which is perfect.

Eyes closed.

Zero the tactor out on the belly button so you know you need a little bit of...

There is your belly button tactor. Keep your eyes closed.

Feel that increase, it means velocity is getting fast.

Slow it down a little bit. Very nice.

Don't dump power. You are on a nice descent right now.

I am not going to give you any warnings.

Your seat pad will tell you 10 ft.

That's not going around. That is me preparing cushion.

Right? You are on the ground.

LAUGHTER Nice job! Nice job!

That was a first for TSAS right there.

Eyes closed approach from over 100ft.

Straight to the ground

like crazy men. OK.

For pilots on the front lines, this ability to make more of their

other senses could make all the difference in the world.

I've done numerous dust landings sat roadsides where you have

zero reference with the ground because of the dust outside.

It's talcum powder - very thick and it envelops you.

So to be able to use your body and adjust appropriately,

not only are you saving the guy's life on the ground

but you also have the guys on board you are trying to protect.

It gives you another ability to...

adjust appropriately so that's amazing.

I am very excited and pleased to be able to say it is a wonderful feeling

in your heart to know you have an answer for a problem that will save

many lives under many different types of conditions, not just in aviation but in many other situations.

This new technology has profound implications,

helping to reveal what our senses are really capable of.

As we use touch, we will find there are more

and more applications in the future and they will be almost limitless, only limited by our imagination.

And it is up to us to come up with new and better ways to use this.

And I am sure there are people out there that will take this technology and carry it well into the future.

And that future may be just around the corner.

In the small German town of Osnabruck, a group of scientists

have been pioneering a groundbreaking new experiment.

They've been pushing the boundary of our sensory capability, attempting to give a man an entirely new sense.

They've been trying to see if humans can make use of the earth's magnetic field, just like birds.

So in the beginning we came up with the idea you

could use the magnetic field of the earth to augment the sensory system

and extend the sensory experience

you usually have.

For the past six years, they've been developing the feelSpace belt -

a vibrating sensory device that enables the wearer to feel the position of magnetic north.

So actually that's the prototype of the belt, so we did the first...

exploratory study with that belt

and it exists, basically

of a row of vibrators like in cell phones so these green things are vibrating.

And at the other side is the most important part.

The compass feeds information to the control box and the control box then controls

all these vibrators.

So if you put it around your waist, like this, there is always one of the vibrators vibrating.

This one is vibrating because there's north and if I turn like this,

the next one is vibrating and if I turn like this, the next one is vibrating.

So a signal's going around my waist.

I think it's not so important how it looks but it really works so...!

Udo Wachter was one of the volunteers who took part in the study.

For six weird weeks, he wore the belt every moment of his waking day.

In the beginning it was a little bit strange because one isn't very

used to having a constant buzzing on the body,

and I'm also a little bit ticklish in certain places!

But it didn't take very long to get used to it,

after a day or so, I didn't really realise it was there any more.

The first clue the team were on to something came when they noticed an important and unexpected phenomenon.

Strangely, wearers found it difficult to articulate what they were experiencing.

It was a sign something really significant was taking place.

It's a characteristic of senses that it's so specific and so special

that it's hard to communicate to someone who does not have it.

You can't communicate how it is to see red to someone who has never seen red.

It hints at the possibility that there is really integration of new sensory information going on.

In the modern world, there's no shortage of technology to find our way around.

But the feelSpace system was unlike any other kind of device.

For the first time it suggested new sensory

information could be absorbed without having to think about it.

You might say, you can just have a compass, and look at it and then you

can find your way anyways but this is what we do not want to find.

We want to help subjects integrate this kind of

information in a way which makes it available to them just intuitively.

Usually senses do not work or they do not need attention so you open your eyes and see,

you take out earplugs and you hear, and you just put your hand down here and you feel that it's sand here.

After six weeks of intensive training,

Udo and the other volunteers faced the ultimate challenge.

Using only his new magnetic sense, Udo had to navigate blindfold around a previously unseen shape.

And even when deliberately disorientated,

he still managed to find his way back to his starting position with remarkable accuracy...

an otherwise impossible task.

While wearing the belt, it felt like having a new sense and after a very short time it just felt like it

should always be there, and it felt like it always was there.

After its initial trial, the feelSpace belt offers us a glimpse of the future,

suggesting we may not be limited by the senses we are born with.

The team are already working on a more extensive trial,

where they will probe the system's impact on the brain in even greater detail

but it's clear that when it comes to creating new senses, this is just the beginning.

Just the idea that there are more ways

to experience the world is just fascinating.

I wouldn't say it's going beyond...

er...

evolution, it's more like...

I would say it's more like a part of evolution.

Because I would say evolution is nothing which stopped ten years ago,

or 100 years ago, or stopped just now,

but it's going on. And if it's going to work out and if we are successful with this study and we find out it is

working then it's an important step for science, but also for everyone who is a human being, in a way.

Over the past ten years, our understanding of the senses has undergone a revolution.

It's enabling us to finally unlock the extraordinary potential of our minds...

and promising to transform all our lives in the most weird and wonderful ways.

So next time you're not sure whether to believe what you see...

enjoy it, because these tricks of the mind are how you make sense of your world.

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