Do You See What I See? Horizon

We live in a world made of a kaleidoscope of colours.

They are part of your everyday life and influence everything you do.

From what you wear

to what you eat, to how you live.

They delight us.

They guide us.

But are these colours quite what they seem?

Probably most people, when they open their eyes,

very naturally, think they're seeing the world as it really is.

Is the sky really blue?

Are the leaves actually green?

Is this definitely red?

That's what people think they are seeing

and it's useful to think that. But, in fact, none of that exists.

It's an unsettling idea that colours may not really exist.

And that's led researchers to ask a disarmingly simple question.

Do you see red in the same way that I do?

Is your green the same as mine?

Do people across the world even see the same colours?

Do we all see colour in the same way? Broadly speaking, that's true.

Absolutely not. No-one sees the same colours.

Now researchers may have a surprising answer to this age-old question.

When it comes to colour, do you really see what I see?

Dr Beau Lotto is fascinated by illusions.

He believes they hold clues to how our senses work.

To how we build the pictures of the world around us.

But the illusion he's most interested in is one of nature's greatest tricks - colour.

Colour is effectively an illusion, right?

It's an illusion that helps us to see the world

in a way that's useful to see.

To try and explain how it works, he's designed an array

of experiments, which will help explain how we each see colours,

and if we even see the same ones.

Do old people see colour in the same way as young people?

Do men and women, or people from different cultures see colour in the same way?

He's invited 150 members of the public, of different ages, gender

and nationality, to take part in his world-first experiment.

So my name is Beau and this is Rich here.

We work together, and today we're going to study the perception

of your colour vision, all right?

So, you're actually going to be subjects in real experiments,

so all the stuff we're doing today, we've never done before, literally.

We have no idea what's going to happen.

Over the course of the next few weeks, he'll put visitors to London's Science Museum

through experiments which will test if colours can change your perception of time,

which will look at how we feel about different colours,

and ultimately whether any of us see the same colours at all.

If we understand how the brain sees colour, we can understand how it does nearly everything else.

And the search to understand why colour is an illusion, and how it works,

begins with the colour red.

Red is deeply rooted in the human psyche.

It conjures up conflicting emotions, from passionate love

to danger and even violence.

But six years ago, a group of scientists

wanted to investigate what effect wearing red might have on us.

We started speculating about the role that it might play in humans,

and whether the clothes that we wear

could in some way manipulate our dominance in competitive situations.

Russell wanted to find solid evidence about what effect red

might be having, and it came from an unlikely source.

From the Olympic sport tae kwon do.

The Olympics offered a perfect situation for this.

In the Olympics, in combat sports such as boxing and tae kwon do,

and in the two forms of wrestling, individuals are randomly assigned

either red or blue to wear depending on their position in the draw.

And of course, if red has no effect, or colour has no effect

on the outcome of sporting contests,

then we'd expect to find an equal number of red and blue winners.

When he studied the results of the bouts, he found that red and blue didn't win equally.

We found, looking at the 2004 Olympics,

there were many more red winners than blue.

In these close contests, red individuals won nearly two thirds

of the bouts that we were looking at in that particular study.

So wearing red seemed to help people win in a competitive situation.

But this on its own wasn't enough to convince him, so he dug more deeply.

He came across an experiment by another group of scientists.

It too was looking at whether colour affected the outcome of a tae kwon do match.

They took the video of the tae kwon do and, in the original video,

you had a fighter in blue and another in red. They manipulated that so the original red fighter

was fighting in blue and the original blue fighter was fighting in red.

And when they showed this footage to tae kwon do referees,

in the original untouched footage,

the red fighter was perceived to have scored more points.

But in the manipulated film,

it was again the red fighter who was judged to have more points,

even though in the original footage they had been fighting in blue.

Again the judges tended to favour the player in red,

whether or not they deserved it.

So the colour the athletes were wearing was enough to override

the fundamental ability of the judges to give points.

Clearly, the colour signal there is manipulating the way

in which these contestants are being perceived by the referees.

Russell published a scientific paper with his findings.

Here was the first evidence that the colour you wear is more than just a fashion choice.

If you wear red, it could make you a winner.

But that raises a more fundamental question.

If red has an impact on sporting encounters,

a key question is to work out whether it's actually having an effect

on the wearer of the red or it's something perceived by the opponent.

The question was WHY wearing red might make you a winner.

To try and answer this question, he's assembled a group of footballers.

He's chosen football because there's a long-held belief,

among fans anyway, that wearing red helps teams to victory.

A lot of the top football teams that that have played over the last 30 or 40 years in England have worn red -

Liverpool, Manchester United, Arsenal - and so there was a suggestion that there might be something there.

His experiment is going to be a lot more scientific.

It starts with a red, blue and white penalty shoot-out.

This sort of experiment hadn't been tested in this way before.

We know from looking at actual sporting data that wearing red does seem to influence

the outcomes of sporting events, but what we don't really know

is the mechanisms by how that comes about.

What they'll be looking at is the effect of red on the physiology of the players.

He's teamed up with someone who was initially sceptical about his research, Dr Iain Greenlees.

I was really keen to do my own work,

to look at it within a more experimental context, to test

Russell's archival data within an experimental setting.

So, together they've devised today's experiment.

They've assembled 32 penalty-takers and 14 goalkeepers.

OK, lads, thanks for coming down.

Hopefully this will be an interesting and fun afternoon,

lots of penalties scored, lots of penalties saved.

Today, you'll be taking part in...

For the experiment to work, the players cannot know

that it's the colour red which is being scrutinised.

..In each of those, you'll face five penalties from three

or four different players.

Before they start, saliva samples need collecting,

heart rate monitors put on, and correct colour kit allocated.

What they're hoping to find out is whether wearing red

makes you feel stronger,

or if seeing red makes you feel threatened.

They're not expecting to see an obvious difference

in number of penalties scored.

They will be measuring two hormones in the footballers -

testosterone and cortisol.

If either of these changes in the men,

it could explain why wearing red makes you a winner.

Testosterone is a hormone that's related to dominance and status.

We'd be arguing that those wearing red might see elevated levels of testosterone.

If we go on the assumption that cortisol is a measure of stress,

then what we might find is that penalty-takers

wearing red would have lower levels of cortisol than penalty-takers

wearing blue and white.

We're hopeful. We expect the effects to be there but they are subtle.

Simply wearing red doesn't mean you'll be a winner.

There's no point me putting on red and hoping to play professional football,

so we're hopeful but you never know in these experiments.

Russell is about to reveal the true nature of the experiment

to the unsuspecting footballers.

It's been fantastic to have your involvement.

As with many psychology experiments, we didn't give you the full story

of what we were interested in looking at at the outset.

The players are a bit surprised that colour might be having an effect on their performance.

Being a Chelsea supporter, and they play in blue,

I don't know how I feel about that.

I paid no attention to what colour I had on. I don't like red. I support Tottenham.

I play in dark blue and we win all the time so...

It would be another four weeks before the hormone results came back.

The first results were the testosterone analyses.

If that was rising, it would suggest red was making the wearer more aggressive.

We didn't really detect any evidence that there were differences based

on the colour that the individual penalty-takers were wearing.

Then they analysed the cortisol.

The more modest its increase, the more confident the players were feeling.

We found that there were subtle differences in what the colour

was having on these cortisol responses.

Even though all competitors seemed to show an increase in cortisol levels in advance of the penalties,

this seemed to be suppressed by those individuals that put on the red shirts.

If we can substantiate this with further analysis,

it suggests that these individuals, by putting on the red shirt, may be going through an elevation

in confidence, and as a consequence this suppresses their cortisol levels

with cortisone being a marker of stress.

If red is leading to an enhance in confidence, then any individual

wearing red may experience that enhancement.

Russell and Iain's study is just one part of a growing picture of the effect colour can have on all of us.

At the Science Museum, neuroscientist Beau Lotto

has devised his own experiment to test another aspect of how powerful red can be.

Red in our society is an incredibly strong signal

for warning, for making mistakes.

People perform less well with an IQ test if they see red

just before taking the IQ test. It's amazing.

What Beau wants to find out is something which might seem

rather bizarre - whether colours can change our sense of time.

In order to do this, he's set up three colour pods.

One white, one red,

and one blue.

The white pod is used as a control to compare to the red and the blue.

OK, are you ready?

What we're going to do is we want to get a sense of how long you think a minute lasts.

Each of the 150 people taking part today are asked to stand in a pod

bathed in colour and give a sign when they think a minute has passed.

I'm going to turn you around, I want you to face the wall,

and I want you to turn back around as soon as you think

a minute's gone past.

Here we're looking to see, if someone is bathed in red,

it might increase their sense of anxiety

and whenever we're in a sense of anxiety,

we perform less well on pretty much anything.

In contrast to blue, where people get a sense of calmness,

we'll find out if that's true because, if it's true,

people will be better able to judge time.

In fact, they might even think a minute lasts two minutes. Who knows?

150 people,

young and old,

men and women...

All asked to estimate how long a minute took under different lights.

After analysis, the colour-pod experiment showed some interesting results.

So, this result, for me, was a bit of a surprise.

In fact, I had a bet on it and I've lost.

I thought red would do the opposite.

I thought I'd feel in a state of arousal

and time would go very quickly.

In fact, it does it just the opposite.

It turns out that colour can speed up time.

But it's not the colour red that does it.

If they are in a blue pod, a minute lasts 11 seconds shorter

than if they are in a red pod.

11 seconds is a phenomenally long time.

Yet, all they were doing is surrounded by blueness

and their perception of time sped up.

So, colour does significantly affect your perception of the passage of time.

One possibility is that red is altering our state of arousal.

It's making us highly aware of our environment.

So that would be very advantageous in a fight-or-flight response,

where you want to be really noticing that things are happening around you.

In a sense, you want time to slow down.

So, maybe that is one possibility for why, if you embed yourself in red,

time actually slows down in your mind.

For scientists, colour is more than just an expression of personal taste.

Red could be having an impact on your hormones,

making you more confident,

and blue seems to be able to speed up time.

The clues about the deeper meaning of colour have emerged from people

who we know don't see colour in the same way as most.

Meghan Sims is a photographer and artist from Ontario.

But she doesn't see colours the way you do.

In fact, she has never seen a colour in her life.

We live in a visual world and, more so, we live in a colour-coded world.

So, for instance, asking directions in a strange city,

people will use landmarks, such as "that red-coloured building".

And then, you know, I'll sort of look confused and say, "Which one?"

What makes Meghan unusual is that she lacks colour receptor cells called "cones" in her eyes.

Cells that react to red, green and blue wavelengths of light.

Favourite time of day is definitely dusk,

when the sun has gone down, there is just a glow of the sun in the sky.

It's just the perfect amount of light.

She does have the separate cells, "rods", that help all of us to see in low light.

When night rolls around, everything just comes alive

and, um, I could lead you through the forest, at night.

She sees the world in black and white.

But she has, in a way, learnt to see colours...

..by matching them to shades of grey.

I learnt about colours by comparison and memorisation.

So, I will learn a certain shade of grey.

Of a Granny Smith apple.

And, from that point on, that will be, to the best of my ability,

that green, that apple green.

Even though she can't see colour, it's an important part of her life.

Putting on clothes in the morning, putting on make-up,

erm, colouring my hair, you know, everyday things.

Painting my house.

You know, there's a billion different shades of green

and I tend to like the ones that are really bright

and make people want to be sick!

As a clue to the fundamental power of colour,

she experiences colours as linked to deep emotions.

Red I will attribute things like danger.

Blue brings out a sadness, or expresses a sadness,

erm, or loneliness.

Yellow...

..I'm not sure about.

I don't really understand yellow.

It seems all of us, whether we can see colour or not,

have a natural ability to link colour with emotion.

Colour is deeply embedded with how we make sense of the world.

It is the surprising power of the colour blue in our lives that is starting to be uncovered.

It's an investigation that has brought a leading neuroscientist

to a different sort of lab.

A rather well turned-out restaurant in London.

I think, increasingly, with so many hours of science,

information has been siloed.

What's happening, increasingly,

is different groups are talking to each other.

Neuroscientists are interacting with lighting designers, or architects.

Reds and browns are often used by restaurant designers

because they are colours that are believed to make you hungry.

The lighting is often set up

to give a warm and relaxing atmosphere to your eating experience.

But one lighting designer decided to try a new concept.

Instead of reds and browns, he chose blue.

Why would you put blue light into a space to make it feel warm?

It was a difficult concept to get across.

It's counter-intuitive.

You know, "We want to make your restaurant feel warm,

"so we want to put blue light in it."

It's very difficult to understand,

but it does come right back to the pure science of how we see.

It makes everything seem warmer, so your skin tones are warmer.

The phrase I used to the client was that it is about

making the beautiful people look more beautiful.

But what Mark hadn't predicted was an unexpected effect the blue light had on diners.

It seemed that night after night, at around ten o'clock,

their behaviour started to change.

Just at a time when you think people would start winding down,

people started to perk up.

There was a vibrancy to it, there was a texture to it

and we didn't understand why that was.

In trying to make the beautiful people look more beautiful, we also created

this second effect of creating a vibrant, enhancing space

that got better and better through the evening

as this blue light component that we had in the presentation increased.

To find out what was causing this behaviour, Mark turned to a scientist.

Professor Russell Foster studies how the changing cycle of night and day

creates a natural body clock within us.

He wanted to discover exactly how these circadian rhythms are created in our bodies.

We were fascinated, a few years ago,

in trying to understand the mechanisms

whereby the light-dark cycle

is detected by the eye and regulates internal time.

Scientists have long understood that the body clock exists,

but how exactly light regulates it has been a mystery.

We asked what we thought was a fairly naive question.

How does the eye grab light to regulate internal time?

He knew that clues lay somewhere in the biology of the human eye.

But he could find no links between the rod and cone cells

to the body clock.

The rods and cones are fantastic for grabbing an instant image

of the world,

but they're not so good at getting an overall appreciation of the amount of light in the environment,

hence time of day and hence for setting the clock.

We couldn't understand how the rods and cones could do this.

We wondered if we may have missed something.

Maybe there's something else in the eye regulating this part of our fundamental biology.

His team made a breakthrough.

They discovered a completely new cell in the human eye.

It's a cell called a photosensitive ganglion.

It plays no part in seeing the world,

but this elusive cell does seem to play a vital role in regulating the body clock.

This is more than a receptor regulating the clock.

These photo-receptors are plugged into a variety of structures in the brain.

The sleep structures, the arousal structures,

so what these photosensitive cells do is regulate broad areas of physiology.

Not only our body clock, but our levels of arousal, our levels of alertness and awake,

and, indeed, our propensity to go to sleep or wake up.

Crucially, this cell that sends a signal to your brain to wake you up

was sensitive to only one wavelength of light - blue.

This is why the people having dinner were waking up at ten o'clock.

For Russell, this new scientific understanding is set to change how we use colours.

-Hello, good to see you.

-Nice to see you again.

Together, they are using this new understanding of colour

to design lighting for where we work and where we live.

-OK, so what do you think?

-Well, it's blue.

-It's blue.

Scientists are now starting to understand that colours do more than show us how the world is.

They powerfully shape how we feel as well.

But to really understand the fundamental power colour has over our lives,

you have to look to clues from the very beginning.

To how and why we learnt to see colour in the first place.

I think you deserve a toast. Cheers!

In Washington state, Professor Jay Neitz has been trying to answer

the big questions about colour for the last 30 years.

There are so many different emotional reactions that people have to colour

and I would really like to understand why.

Probably my favourite scene in any movie is the scene in the Wizard Of Oz,

where the whole film is black and white

and then there is that scene

when suddenly it goes to Technicolor.

And just the impact it has on the audience is fascinating to me.

He believes the clues to the power colour exerts in our lives today,

lie deep in our evolutionary past...

..beginning at a time when our earliest ancestors were a humble, single-celled organism,

living in the murky depths of the oceans.

When the Earth was covered with water and all organisms had just one cell,

the only thing to see was the sky overhead.

Life on Earth is dependent on energy from the sun.

But these one-celled organisms had a problem,

and that is that they had to be able to harvest the energy

from the longer wavelengths -

the oranges, the yellows and the reds -

but they had to be able to avoid the damaging, lethal, ultraviolet rays.

It is the earliest signs of why colour mattered.

These single cells moved up and down in the oceans to avoid certain wavelengths of damaging light.

In the middle of the day, they used to send it away from the surface of the water,

down low enough where the UV was not intense.

Then, at dawn and dusk, they would come up to the surface

to capture those longer wavelength lights and that is how they got energy.

Our earliest sensitivities to colour were a simple two-colour system -

blue, yellow.

But as life on Earth evolved and changed,

the way our early ancestors processed colour changed, as well.

It was around 40 million years ago that primates developed

another set of structures in the eye.

These ones sensitive to red and green.

The main advantage of adding an extra dimension of colour vision is

colour is like a language.

It would be like adding to your vocabulary.

Hello.

There is an entire communication throughout the entire biological world

that's dependent on this very elaborate colour-vision system.

It was when it was useful to recognise the colours of fruits for food

and the warning signs of nature, that we gained the red-green colour cones.

One thing we can imagine, then, it was this that gave them

the huge advantage and was responsible for the explosion

of all the different kinds of primates we see now

that have exactly the same beautiful colour vision like humans do.

For us as a species, the way we learnt to see colours has a history.

To blue-yellow colour sensitivity, we added red and green,

expanding our very own language of colour.

It's that history that Jay believes plays out today.

And helps explain why we have such different reactions to colours.

Meet Dalton.

Meet Sam.

They are squirrel monkeys that Jay has been working with for the last four years.

Like all squirrel monkeys, when they arrived at Jay's lab,

they were colour-blind, and couldn't see reds or greens.

The squirrel monkeys have red-green colour-blindness.

So the thing that red-green colour-blindness means

is that these animals that have that, and humans too,

they completely lack the sensations of either red or green.

The big question was, does this change the way that the brain

interprets the signals from the eye, so they would have an experience of colour vision

that would be like what a human would?

His team did something remarkable to these monkeys.

They gave them the missing receptors in their eyes,

and allowed them to see the reds and greens which had been invisible.

He wanted to find out whether having these new cones in their eyes

would allow them to see new colours.

All of a sudden, they were able to pick out those red dots and green dots against the grey background.

Probably a thing that amazed us the most, besides the fact that it worked at all,

is that it seemed they were able to get this new colour sensation

immediately, as soon as the new thing turned on.

So somehow, the brain was able to make some kind of sense out of this immediately.

This was the moment when Jay could study in a lab

something that happened nearly 40 million years ago.

With their new sense of red-green colour vision, Sam and Dalton could,

for the first time, point to the green and red dots on the screen.

And crucially, when it came to feeding time,

they were able to associate colours with different coloured food.

And so over time, they learnt to associate different colours

with different objects, and now they take on lives for themselves,

they say, "Oh, this is a food I like, so I like red."

But this is the key to how colours became connected to emotions.

If the monkeys like red fruit,

then they learnt to associate the colour red more generally with pleasure.

And what that means for our sense of colour is that the earliest colours we learnt - blue and yellow -

have hard-wired emotional connections.

Our associations with red and green, we've had to learn.

So I think that maybe red-green colour vision

is very different than blue-yellow colour vision, that's so deep inside of us.

That those emotions are driven by something that we were born with.

The fact that the blues are kind of calming.

That's why people make such a strong distinction between cool colours and warm colours,

as opposed to red and green,

because those are very deep feelings that we're all born with.

Whereas red-green is a modern thing

that's completely a function of our cerebral cortex,

and it's a learning process, just a little different buzz inside your head,

but it takes a lifetime to be able to associate different colours with their real meaning.

This shows that all colours are not equal.

Blue digs in to our earliest evolutionary responses.

Red and green are colours which we have had to learn.

I think for all of us, the reason that we see red as the same

is because we have shared experiences.

Red is the colour of lipstick, red is the colour of blood,

the colour of stop signs and flashing lights.

And green is the colour of pastures.

Essentially, our earliest experience of these colours

was inextricably linked to pleasure and pain.

To see these colours meant we could function more successfully in the world.

This has stayed with us to the present day.

But this new understanding of why different colours have such powerful effects on our lives

raises another, more fundamental, question.

How do we create colour in the first place?

For Beau Lotto, colour is one of the most powerful illusions that nature plays on us.

While for physicists, colour may be simply wavelengths of light,

for Beau, his long fascination with illusions

has been powerful proof that colour is more than that.

I want to show you how quickly your brain can redefine normality.

See the world in a completely new way, based on its experience,

except in this case, it'll be an experience for one minute,

and you're going to see something completely different as a consequence.

Through this illusion,

Beau wants to show how easily the colours you see can change.

For now, the sky in both pictures is blue, and the sand is yellow.

Now, look up here.

Do you see a green square on your left and a red square on your right?

OK. What I want you to do is to stare at that dot

between the red and the green squares.

The illusion should work

if you carry on staring at the dot between the two top squares.

While you're looking at it,

I'll tell you what's happening inside your head.

Your brain is learning that the left side of its visual field

is under green light.

It's also learning that the right side of its visual field

is under red light. That's becoming its new reality.

For this to work, you must keep your eyes on the dot.

When I tell you, you're going to look at the dot

between the two desert scenes. Don't do it now, when I tell you.

5, 4, 3, 2, 1.

SURPRISED LAUGHTER

That's amazing.

For most people, this is how they see the colours change.

The sky that was blue is now pink on the left

and more green on the right.

In just one minute, the colours have changed.

Colour doesn't exist. Colour is a construct of your brain.

There is nothing literal about colour in the world.

And this understanding of how the signal from your eye becomes an experience of colour in your brain

is one of the most exciting and challenging questions in modern science.

Take a look at this trick of the brain.

It's one that happens every time you walk from an artificially lit room to daylight.

It's so good, you don't even know what's happening.

But the light outside is a range of different wavelengths.

The light may look the same, but it isn't.

This is closer to what it really looks like.

But your brain fixes the picture so the colour stays constant.

It's called colour constancy.

And it's something that has intrigued and baffled scientists for centuries.

Neuroscientist Anya Hurlbert studies colour constancy

because it may offer insight into how the brain processes colour.

Colour constancy is so fundamental to the way we see colours

that we don't think about it in everyday life, we don't know how we do it.

And in order to understand how the human visual system

achieves colour constancy,

we need laboratory measurements of just how good colour constancy is.

To do this, she set up an experiment involving a well-known set of objects.

Fruit.

And she's going to be asking people to try and estimate

the colour of the banana as the light changes.

Your task here is to match the colour of the banana.

I'd like you to make another practice match, this time to the banana.

There are in fact two yellows in the picture.

The banana, and a simple patch of the same yellow in the background.

As the light changes,

how will someone's perception of the colour of the banana and the patch change?

Is the match that a person makes to the yellow banana

different from the match the person makes to a yellow patch?

If the matches are different, that means the object is influencing colour perception.

Experiments show they are different.

People perceive the yellow patch as changing as the light changes.

But the yellow of the banana stays more constant.

And the reason this colour constancy works, Anya believes,

is because we should know what a banana looks like.

One of the factors that might contribute to colour constancy

in the human visual system is object knowledge.

So for example, the fact that we know that bananas are yellow,

and we've seen bananas under many different illuminations,

may enable us to perceive the yellow of a banana as more constant under changing illumination

because we know what colour it should be.

Colour constancy shows once again that your eye doesn't simply SEE colour.

Your brain creates it...

..by drawing on knowledge of what things should look like.

That raises the intriguing possibility

that many different aspects of what make you individual go into making colour.

Not just memories, but other complex operations that happen in your brain.

Even, it now seems, the language you speak.

It may seem a strange idea that language might affect the colours you see.

And some of the clues might lie in understanding

what happens inside your brain as you begin to learn words.

This is a subject that Dr Anna Franklin,

from the Surrey Baby Lab, has been looking at.

Colour vision is not something that you are automatically born with.

So newborns have got really, really limited colour vision.

And their colour vision develops over the first three months of life.

As the colour cells in their eyes develop over these three months,

they begin to see colour.

But what Anna has found is that something as simple as the words you learn

might be having an impact on how your brain processes colour.

Potentially, language could actually structure how the brain is structuring the visual world.

The first clues arose when Anna started looking at what happens to children's brains

when they learn to speak.

It was comparing the brains of children pre- and post-language

that they discovered something rather fascinating.

So, Claudia, thanks very much for bringing Max and Noah to the lab today.

What we're looking at today is how babies and toddlers categorise colour.

In the English-speaking world, we have 11 colour categories.

What Anna is looking for is how the brain processes these categories pre- and post-language.

First in the chair is Max, who has no concept of language.

Colour categories appear to be present in infants,

even before they have learnt the words for colour, so somehow,

infants are also dividing up the spectrum of colour into categories,

even though they don't have language to tell them how to do that.

By tracking Max's eye movement,

Anna is able to tell that it's the right side of the brain

which is processing the colour categories.

What's fascinating is what happens when three-year-old Noah,

who HAS learnt his categories, does the same experiment.

Their category effect is stronger in the right visual field,

and the right visual field initially projects over to the left hemisphere,

which is the hemisphere that's dominant for language.

So inextricably linked is colour to language

that it jumps across your brain as soon as you start acquiring words.

We're really excited about these findings, because it suggests,

potentially, that learning language or learning colour terms

can actually change the way in which your brain

is actually categorising the visual world,

the way in which your brain is deriving structure

from the world which it's seeing.

This suggests the way you process colour

and how you learn language are connected.

But to really understand how language might help shape colour,

scientists began looking at a group of people

with a colour vocabulary as different from most of ours as possible.

Northern Namibia.

A remote and barren landscape.

Home to a remarkable tribe, the Himba.

The Himba women are famous for covering themselves with ochre,

which symbolises the Earth's rich red colour,

and blood, which symbolises life.

But that's not what has brought Serge Caparros here.

He's here because there's something rather special

about how the Himba describe the colours they see.

What is the colour of water? >

HE SPEAKS IN NATIVE LANGUAGE

White. >

OK. And milk?

HE SPEAKS IN NATIVE LANGUAGE

Also white. >

For me, you see, where I come from, we say the water is blue,

and the sky is blue, and you say the sky is black, water is white.

So we have different words to talk about the same thing.

While we have 11 words to describe colour,

the Himba have half the amount.

They include "Zoozu", which is most dark colours,

and includes reds, blues, greens and purples.

"Vapa", which is mainly white, but includes some yellow.

"Borou", which includes some greens and blues.

And "Dumbu", which includes different greens, but also reds and browns.

They clearly describe colour differently, but do they see the same way?

Serge has been running experiments to find out.

OK, now you look at these squares, one of them has a different colour, which one?

He's testing how long it takes them

to spot a colour which is different from the others.

Can you do the same thing again?

This is what they're looking at.

For us, it's quite hard to spot the odd one out.

OK, can you point one more time towards the different colour?

Very good.

But for the Himba, it's easy to see the green which is different.

So you see, in this particular trial,

this green patch looks very much like the other ones,

at least to me, and I think to most other Westerners.

Whereas for the Himba, this is a different colour,

they have a different word for this type of green

compared to the other types of green,

and that allows them to more easily distinguish between these two colours

when they're next to each other, whereas for us it's very hard.

When Westerners do this exact same trial, they will spend much longer

and be much more likely to make a mistake than the Himba.

The next experiment is trickier for the Himba.

In this one, they're shown a circle of green squares,

which includes one blue square.

So again, 12 colours,

and you point towards the one that is different from the other 11 colours.

For us, we have separate words for green and blue.

But as the Himba have the same word for both,

it takes them longer to spot the blue.

It's not there. She can't see it.

OK, that was a difficult one for him.

The difference between the two categories of colour

are very close to each other - for us it's clear the one that is different,

but for them, they have to look very hard.

We measure the time they take to give a response, as well as errors.

And what we find is that the Himba will take much longer

to find the different colour in this version of the experiment with blue and green.

The Himba, with their five words,

do, in some ways, see the world slightly differently from us.

At Goldsmiths College, at the University of London,

Serge's professor, Jules Davidoff, is trying to get to the bottom of this difference.

I'm going to show you this.

Look at it carefully. Don't say anything.

He's been doing similar experiments with children.

Look at it carefully. Ready?

It seems that the number of terms a culture has for colours is all down to how much we need them.

There are many languages in Europe

that only had five or six colour terms until quite recently.

Welsh is one example, where there was no word for pink or brown.

But now these words are important,

and so the words have become imported into their language.

Language does have a subtle effect on how you see colour.

It really shows up, not with individual colours,

but when you compare two colours side by side.

For individual colours,

everybody sees the same sensation.

But when we have two colours,

we have to make a similarity judgment.

And making a similarity judgment, we believe,

differs according to whether you have different words for colours.

All this suggests that seeing colour

is about lot more than just opening your eyes.

Colour is created in your brain.

It's made from the language you speak.

The memories you carry.

Even the moods you feel.

It is one of nature's great illusions.

That's why Beau Lotto wants to test how each of us creates colours.

Because maybe we all do it differently.

Do we all see the same colours?

People have been asking this question for centuries, really.

And it's a fascinating question. Is one person's perception of red the same as someone else's,

or could your perception of red be my perception of green?

The first experiment was looking at how people arrange colours together.

They were given 49 different tiles,

and asked to place them in any pattern they liked on the board.

And the question is, what do they do?

They're going to create a pattern, but which pattern,

and why that one, as opposed to another?

There are hundreds of billions of different ways these colours could be arranged.

Rather a lot.

But he found that people didn't arrange them at random,

but in patterns that were so predictable

that Beau could generally work out how people were going to place them together.

So if you gave me a colour, I could predict the colours

that people would put around it, almost perfectly.

And yet each person there had no instruction,

just to take these colours, put them on this board,

and they all created something that was highly predictable.

The clue to predicting the patterns people were creating lay in nature.

People were creating structures that were similar to the natural images they saw every day.

So what that tells us is that when it comes to seeing colour,

we can't escape from our ecological history.

We can't but help impose that structure onto the world.

We all have, hard-wired into our brains, a natural sense of how colours should fit together.

A second experiment looked at how the way you feel

might affect what you see.

Beau used two different states often used in psychological experiments.

Feeling powerful and in control, or powerless.

Because of some of the manipulations we're doing to people during these experiments,

we're giving them a sense of power, by them remembering

a time in their life where they had a sense of control.

The experiment he gave them was to look at a coloured dot on grey,

and to say if they noticed the colours changing.

We then sat them down, and we altered the light,

and we asked them, how different does it have to be before you see it?

The question was whether the people placed in the powerful state could spot the difference in colour,

in the same way as people in a powerless state.

Now, you would have thought something as simple as that

could not be affected by how I feel. But in fact, it is.

He found that people feeling more powerful

were able to spot changes in colour more effectively than the powerless.

The more powerful, the more control they had, the more sensitive they were.

There's even a difference between men and women.

What was remarkable is that not only were women more sensitive

than men, but then, women who had a stronger sense of control

were even more sensitive than women who were not.

How these women felt about themselves actually caused them

to see the world more accurately, or less accurately.

The experiments looked at different aspects of colour perception.

Just push on forward.

Looking at how young and old people connected colour and emotion.

Looking at how they perceived patterns of light and dark.

And of course, at how colour affects the perception of the passing of time.

For those of you see the shades of grey different over here than over here,

you're going to be a bit surprised.

When he examined the results in detail,

he found consistent patterns in how groups of people perceived colour.

We discovered that in fact, people of different sex, different age,

different levels of status, actually perceive colour differently.

And that seems really quite remarkable, when we remember

that all we're dealing with is the light that falls on to your eye.

It's a remarkable finding. It suggests that in everyday life,

we could be experiencing colours differently from those around us...

..even experiencing colours differently from day to day.

So in thinking about whether, do you see what I see?

The answer really depends on what it is we're looking at.

So if what we're looking at is something that's been shaped by evolution itself, then yes,

we probably see something very similar.

But if it's something shaped by our own individual experiences,

then no, we can see the world very differently.

What's surprising for us is that our individual experiences,

the differences in our individual experiences,

in the way I feel at this moment,

can alter something as simple as colour.

So we can see colours differently, based on how I feel.

What that means is that the colours that are hard-wired

into our evolutionary history, we probably see these the same.

But for the others, like the colour you see in someone's eyes when you're in love,

or the colours you choose when you're feeling sad,

when it comes to these, you're probably not seeing what I see.

# Somewhere over the rainbow

# Way up high

# And the dreams that you dreamed of

# Once in a lullaby... #