You Are What You Sense Inside the Animal Mind

I've spent most of my life watching animals.

And there's one question that obsesses me.

What's it like being an animal?

This is Itchy and Scratchy. I've had them

since they were 6 weeks old, I've raised them, I love them

so much and just like all dog owners I sometimes gaze into these

little chestnut eyes and wonder - what's going on inside that head?

And you know, I would give anything to be another

animal for just five minutes, to be able to experience the world

the way they perceive it, to know what they're thinking.

To be INSIDE the animal mind.

It's one of the great mysteries of the natural world

and now, new research is starting to give answers.

Wow.

In this series, I'm going to seek out

the most powerful animal minds on the planet

and find out what they're capable of.

Look at that!

If I'm really going to get inside the minds of other animals,

the first thing I need to do is to discover how

they experience the world around them.

I mean, imagine how different this world is to my dogs.

To them, this is a landscape of smell.

We both live in the same world

but we experience it in completely different ways.

In this first programme we'll investigate

the sensory secrets of the animal we know best of all.

Close your eyes.

Dogs.

Aww, what happened?!

WOLF HOWLS

And test them against their ancient ancestors.

THEY HOWL

We'll be discovering how the minds of very different animals

perceive their world through their senses.

And I'll come face-to-face

with an animal that most people wouldn't want to meet in

their nightmares as I learn about the remarkable sixth sense of sharks.

Animal senses define the way they think.

They're the gateway to the animal mind.

Castlewellan Lake in Northern Ireland.

I've come to its rain-swept shores to see a dog do something

that I thought impossible.

Now, obviously, Itchy and Scratchy

have got a pretty good pair of noses.

But what I've always wondered is

just how good is the dog's sense of smell?

Well, today we're going to put the dog's nose to the ultimate test.

Neil Powell trains sniffer dogs.

And one of his top performers is Fern.

Now, Fern usually works for the Search and Rescue Dog Association.

But today, she's going to try and sniff out something

that Neil has hidden.

What's extraordinary is that it's not on dry land.

It's in the lake.

It's underwater.

Here she is, Fern. Oh, oh. Looking keen and all dressed up.

What type of spaniel is she?

She's a mixture between Cocker and Springer Spaniel.

-So, she's known as a sprocker.

-A sprocker.

Now, let's get this straight. You've already been out this morning

and you've hidden a lure IN the lake?

-Hm.

-And we're going to go out and she's going to sniff it?

-Yeah.

-And find it?

-Yes, what we've done is,

about two hours ago we hid a small canister in 20 feet of water.

It's got some pork meat in it. I know where it is but she doesn't,

so we're going to search the lake now with her and, hopefully,

we'll get to within about 30 feet of it.

-Come in then, Fern.

-Let's go for it.

-I really do need to see this.

Can a dog really smell something on the bottom of a lake,

in driving rain and strong winds?

Sounds improbable.

Neil and the dive team know precisely where the canister

is hidden because they fixed a GPS position on it

when they dropped it into the lake.

The question is, can Fern find it?

Of course, this isn't a stunt that Neil and Fern pull off

for the joy of it, she's been trained to detect bodies that have come to rest

beneath the surface of the water, there's a very serious side to this.

Nevertheless, it's pretty counterintuitive, isn't it?

Here we're asking a dog to smell through six metres, 20 feet of water.

And when you think about it, in all those movies and cop shows

we've always watched, when the criminal's fleeing, they run up the stream

so they don't leave any scent because the dogs can't sniff them.

Well - criminals, if you're watching this,

you might have to think again.

The team's technique is to systematically crisscross the lake.

So, at some point,

Fern will find herself directly downwind of the sunken canister.

But will she pick up the scent?

The lake is a mile long and half a mile wide.

And only the tiniest quantities of chemicals from the meat

might reach the surface.

And of that minute trace, almost all of it will get blown away.

And yet, around ten minutes after we start...

DOG BARKS

..Fern senses something.

DOG BARKS

That's the scent.

Turn it up to the wind, John.

We start circling, narrowing down the location.

She's got the scent, how are you going to know when we're

in the closest possible spot?

When she arrives over the top of it you'll see her going over

the side a little bit more and she's really focused on the water.

-You're getting her right into the... see, there, see that?

-Yeah.

Bring her round there, John.

Right round, John. I'd put her there, John.

DOG CONTINUES BARKING

Fern has made it quite clear where she thinks

the source of the smell is.

Fern is confident which in turn means Neil is very confident

and they've dropped the marker in and the thought is that we

could be within just a few metres of where the lure is hidden.

But the one thing I will say is I'm sat here as any other human being

would be, with no sense at all, using a sense

of smell that we are in the right place. All I can smell is a

slightly fresh, rainy, damp,

very pleasant afternoon in Northern Ireland.

There's only one way to know if Fern's chosen the correct spot -

The dive team check it against the GPS fix they took

when they threw the canister into the water.

And, unbelievably, Fern is bang on top of it.

The divers' final job is to retrieve the canister.

But the lake bed has a surprise.

The bottom is a metre of soft silt

and the canister has sunk right into it.

So, amazingly, Fern hasn't just sniffed the lure through

six metres of water but also through a metre of mud as well.

What an absolutely astonishing thing.

Now, I've seen animals over the years pull off some remarkable feats

but this has been something else, it really has.

-There ye go, what a clever girl.

-Good girl.

-Clever girl

'And the reward for all her efforts? Just an old tennis ball.'

Fern's training might give her this special ability.

But all dogs have an extremely powerful nose.

They can smell in parts per trillion, the equivalent of being

able to taste a spoonful of sugar in two Olympic-size swimming pools.

So, how on earth can dogs do this?

Well, it's all down to a nose that's nothing like ours.

Each nostril can be controlled independently, allowing dogs

to detect precisely the direction a smell is coming from.

And what goes on inside is even more impressive.

You see, dogs split the flow of air into two separate streams,

one for breathing and one for smelling.

So they can do both at the same time.

It's a superb tool for gathering sensory information and it means

a dog's mind understands the world in a completely different way to us.

Their world is a complex smellscape in which they can sniff out

an animal that's too far off to see.

Or pick up the tiniest trace of odour left on a leaf.

But although smell is vastly more powerful for dogs than it is

for us, it's one of the five senses that we share

with them and most other animals.

And there's a reason for that.

The senses are the front line in the way that animals interact

with the physical world around them

and this goes a long to explain how those senses actually work.

Whatever kind of animal you are,

you experience the same physical properties.

I need vision to see light bouncing off objects -

I need touch to feel surfaces and sense temperature.

I need to smell and taste chemical substances.

And I need hearing to detect shockwaves in the air.

These are my five basic senses to guide me through the world.

Perhaps it's not surprising that I share these with the

vast majority of other animal species in some combination or other

for the very simple reason that we all inhabit the same physical world.

And yet - those five familiar senses can be used by

some animals in ways that are totally foreign to the human mind.

DOLPHINS CLICK AND CRY

I've come to the Dolphin Research Centre in Florida to see

something that dolphins can do with their sense of hearing.

Now, it's hard to study dolphins in the open ocean.

But keeping them in captivity is controversial.

WHISTLE BLOWS

And since 1988, aquariums in the United States

don't take dolphins from the wild.

DOLPHIN CRIES

Dolphins like Tanner were born in captivity.

Tanner, are you ready? No? Yes, you are ready.

Researchers Armando and Wade want to show me

an ingenious experiment to demonstrate how Tanner uses sound.

I have a list of behaviours right here now, I can't see them,

please don't show them to me...

I'm going to select an action from a list for Wade to

perform in the water.

Wade, go ahead in.

I'm only showing Wade,

Armando and Tanner have no idea which one he's about to do.

OK, Wade, let's go for this one, please? OK?

Tanner, imitate.

'With his eyes covered, Tanner will now attempt to imitate Wade.'

Then the other one will go on the left eye, but I have to give him

the signal first, which means imitate.

Are you ready?

Imitate...

'So, will Tanner know what Wade is doing?'

There he goes, Wade is upside down and Tanner is upside down as well.

'OK. That's one out of one.

'But for something this bizarre, I need a little more proof.'

-Shall we try another?

-Try another one?

Let me put the eyecup on.

Let's go for this one, Wade...

And here we go...

'Tanner appears to take a moment to listen before imitating

'Wade's exact movements.'

It's pretty impressive, I have to say.

'And for the piece de resistance, the bob.'

Next word...

-Now, watch. He's reading.

-He's reading, without

a shred of a doubt. He's reading without seeing.

There's no question of that, and getting it right.

WHISTLE BLOWS

-Good boy, Tanner.

-Thank you very much, thank you.

-Excellent!

Tanner, you're the best.

'So, how does Tanner do it?'

DOLPHIN CLICKS AND BEEPS

Scientists believe he's using sound in an unusual way.

It's called echolocation.

A specialised fat-filled organ called

the melon behind the forehead emits focused pulses of sound.

But the key to echolocation is listening to the

echoes of those sound waves as they come back.

Dolphins pick up and amplify those returning waves with

a cavity in their jaw, before sending them on to the inner ear.

They use echolocation to hunt down and pinpoint their prey

even in darkness.

Dolphins share this use of hearing with nocturnal animals like bats.

But just how detailed a picture of their world can

they build up in their mind, using this one sense?

When we hear that burst of sound being pumped out by the dolphins

it's no more than a rapid cacophony of random clicks as far as we're concerned,

but this I think will surprise you, because if we process

the return echo simply by slowing it down, this is what we can hear.

QUICK RHYTHMIC BEATING

This is a return echo from an Atlantic cod, whilst this...

DIFFERENT FREQUENCY BEATING

..is what's bouncing back to the dolphin from a mullet,

so clearly for the dolphin it's a very sensitive sense, it can

tell the difference between these two different species of fish,

perhaps even choosing which one it wants to eat.

The dolphin's echolocation is an extremely powerful sensory tool

which allows its mind to build up a picture of the world.

But at the moment I'm left thinking, what does a dolphin actually

do mentally? What does it think with all of that echolocation?

Does it turn it into a visual image?

We don't know, we may never know.

But one thing I'm sure of is that this will have

a profound effect on the way that these animals think.

Countless other animals use their five senses in ways which,

to us, are unfamiliar.

Starfish see, but not as we do.

A basic eye at the end of each limb can form simple images,

helping them find their way

back to their feeding grounds.

Butterflies and moths have no nose.

But their sense of smell is many times more sensitive than

even a dog's.

And it's thanks to their antennae.

In some species the antennae can respond to only a few

molecules of scent from a potential mate.

When I was a kid we called them "feelers"

but they're actually being used for smelling.

Across the animal world, species evolve the senses which give them

the best chance of surviving in the environment where they live.

But very often, individual species or groups of species will form

a sort of a sensory hierarchy in that one or two senses will become

far more sensitive than the others.

So, if two animals have a different dominant sense,

how far does that influence the way that they think?

WOLF HOWLS

I've come to Wolf Park in Indiana, to find out.

WOLF HOWLS

THEY HOWL

Scientists here are studying a group of ten wolves

that roam over a territory of a dozen acres.

Wolves are fascinating

because, biologically, they are the same as dogs.

Around 10,000 years ago, humans began domesticating some wolves,

and over time they created dogs.

Now, wolves haven't changed much in that time.

Dogs, on the other hand,

have evolved into an astonishing variety of breeds.

They look very different to wolves.

But how differently do their minds work?

To give us some insight, we're going to test dogs

and wolves in a battle of the senses.

So first, I want to establish the sensory abilities

these two animals share, starting with smell.

This couple of wolves down here are about, I don't know, 60m away

and I'm going to test that sense of smell.

They've got expensive tastes, these animals, because what I'm going

to use is this, Chanel No 5.

It's said that they have a real craving for it.

So, I'm just going to sneak down here...

..put some of this on the grass...

..and see what happens.

Well, there goes a tenner, at least,

let's see what happens.

But it's not so much picking up that scent, it's what they do

when they find it that we're interested in.

Oh, nose is up.

Yes...

Oh...

Look at that...

This is what we call scent rolling and I'm afraid to say that

many of you have probably seen your dogs doing this

in less pleasant things than expensive perfume.

HE CHUCKLES

It's brilliant, isn't it?

On the face of it, it seems that dogs and wolves live in the

same sensory world and it's a world dominated by the sense of smell.

Let's go!

But that's not the only sense that's important to dogs.

Let's go.

Any dog owner knows they watch us closely with their eyes.

So, what role does vision play in how dogs understand the world?

Dr Brian Hare has recruited dog owners from across the US to carry out

some simple tests that show how they use visual information.

OK, Sisu, stay.

-OK.

-One of the simplest is called the Pointing Test.

And now watch where her gaze goes. Right at me. Stay.

Right, so what we've got here is a very simple experiment.

We've got two people, we've got two cups, we've hidden food in both

cups and we have a dog, of course.

And all I'm going to do is I'm going to gesture at one of the two cups

and the question is, does the dog go where I gesture or to the other cup?

Now, it can't be that she's just using her smell

when she makes her decision because there's food in both cups.

So, let's see what she does.

Both cups smell equally appetising.

So, there's only one reason for Sisu to choose between them.

OK, Sisu, you ready?

-This.

-OK, Sisu.

It's the visual signal that Brian is giving her.

Good job. And there's one here too.

All right, so she did use my gesture there.

Sometimes I'll point to the right

and sometimes I'll point to the left.

But let's do it again because it could be chance.

Hey. OK, Sisu.

All right...

So, what we've seen is that Sisu really relies on my visual gestures,

she's not relying on her nose.

If I'm there and telling her something, she's much more

happy to use that information than to rely on her nose.

Most dog owners will be familiar with this ability.

-OK, Kai.

-Dogs will readily follow visual information.

-Callie, is it there?

-But we also know they have great noses.

So, which sense do dogs trust the most - vision or smell?

In a new test, Brian is going to put Dexter's nose

in direct conflict with Dexter's eyes.

So, we're going to actually show Dexter where we're going to hide

the food so he can remember where he saw it.

But then what we're going to do is we're going to close his eyes

and shift where it's hidden and move it to the other location.

That means he could potentially smell where it is, the question is,

does he use what he saw to find the food or does he rely on his nose?

So, let's see what he does... All right, Dexter.

Oh, look at that face. Oh, you're killing me.

All right, Dexter, are you ready, buddy?

OK, that's where it's going to be.

This time there's food under only one cup.

OK. Now close your eyes.

And without Dexter seeing,

Brian's now moving that food to the other cup.

Poor Dexter's senses are in direct conflict.

So, does he trust his eyes or follow his nose?

OK, Dexter, find it!

Aww, what happened? It's a trick!

It's over here, it was a trick!

Are you ready, Dexter? OK, we're going to put it over here.

Here it is. Now, close your eyes.

OK, Dexter, go get it.

Again and again, Dexter, like most dogs, goes not to where

he can smell the food but where he SAW the food.

OK, Dexter, get it!

Awww!

It tends to be that if they have visual information

they prioritise that, they actually put that in front of what

information they might be getting from their nose.

But what about wolves?

Do they prioritise their senses in the same way?

Well, back at Wolf Park, we're going to test them.

Kathryn Lord from the University of Massachusetts

reared this group of wolves

from birth and they're certainly familiar with humans.

THEY GROWL QUIETLY

I know, I'm going to stand up for a second

cos you're getting a little excited, I know.

So, this grey wolf Fi can understand certain types of information

that a wild wolf wouldn't.

SHE CALLS WOLF

WOLF HOWLS

She comes when her name is called.

Fi!

And, remarkably, Fi can also follow Kathryn's pointing.

She's just as capable as any dog of understanding what it means.

Hey.

We've seen that dogs trust this visual signal above smell.

So is this also true of wolves?

To find out, we're going to repeat the finger pointing test several times,

just as we did with the dogs, with a snack under each can.

Fi!

So, will Fi the wolf respond like a dog to a series of finger points?

She didn't appear to look then.

That time she just went for the cheese.

SHE LAUGHS

Fi has quickly learned that in this experiment,

the visual signal is irrelevant for finding the food,

instead she chooses to follow her nose.

What's interesting is what the wolf's doing in the approach

because there's no doubt at all that she's looking at Kathryn,

she can see her pointing.

But it seems that the nose wins over the eye, because she's looking,

but ignoring what she's seeing. But not what she's smelling.

The reason she's probably ignoring me

is because she's perfectly capable of solving the problem without my help.

So she doesn't need to pay attention to me.

So, visual information seems to have a lower priority for wolves

than it does for dogs.

Wolves give greater emphasis to smell.

Kathryn believes she might have discovered why.

It's all about what happens in the first few weeks of life.

You investigated this by raising wolf cubs from that

very young age and contrasting their behaviour with dogs.

I did, yeah,

so I actually hand-raised both wolves and dogs.

The wolf pups are great, so we get them at about ten days of age

so at that point they can't see, they can't hear, and they can't smell

and they can't really walk either,

they're just, kind of, little puddles of fur.

But as her wolf cubs developed,

Kathryn observed something fascinating.

There's a brief window of time soon after they are born

when the senses of both dogs and wolves are set for life.

The window starts early for wolves, at just two weeks old.

At this stage, only their sense of smell has fully developed.

So, they can only understand their world through smell.

But for dogs, this sensory window starts at four weeks, a small,

but crucial, difference.

Because by then, dogs have developed ALL of their senses.

When the dogs start to explore their world,

they can use their vision, they can use their smell

and they can use their sounds all at the same time.

So, it seems that since the process of domestication started,

the dogs have developed a greater flexibility to involve

all of their senses and to be able to prioritise more their vision

and their hearing than the wolves, so you might argue that they're

a slightly more successful animal when it comes to dealing with people.

The ability of dogs to be flexible is what allowed them to come

into our environment in the first place

and probably allowed them to be domesticated.

So, wolves are hard-wired to trust smell above all other senses.

But dogs use their senses far more flexibly.

The senses have shaped both these animals' minds.

They've helped define dogs and wolves as very different animals.

So far, we've seen how animal minds deal with sensory information

that's manageable.

But what happens if your mind is being BOMBARDED by your senses?

Take these birds for example, zipping around in the sky here.

For them and many other flying animals, it's all about economy of weight

and by necessity, therefore, they have to have smaller brains

and that will have an impact on how they perceive their world.

It will present its own very peculiar challenges.

Birds on the wing can move in any direction they choose.

But being able to fly brings with it the constant risk of collision.

And what's more, their predators in the air, like hawks,

can also attack from anywhere.

So bird brains need to take in visual information

from every direction.

Their eyes can see down, up, left, right,

in front and behind, all at the same time.

And yet, with nearly 300 degree vision, a swallow can pull complex

manoeuvres at 70kmph within centimetres of buildings.

It's an incredible amount of visual information to process...

all achieved with a tiny brain.

A swallow's brain weighs around one gram -

a thousand times lighter than ours.

So how on earth do birds do it?

To find out, we've decided to carry out a rather bizarre experiment.

It involves some big, stripy boards...

..and some starlings.

You ready?

And to help, we've brought in Martin Stevens -

an expert in animal senses.

Oh, it's looking beautiful.

Come on.

I'm hoping that this is going to reveal how birds' brains

process the vast amounts of visual information they need to handle.

Ready to go? Look at that. What a splendid animal.

Too keen. We weren't quite ready.

We like that. That's what we like with our trial birds.

Martin, what's the plan?

What we're going to do to try and understand how birds process

so much visual information,

is we're going to get him to fly down this corridor.

To begin with, we'll have these stripes horizontal,

and we'll time using these precision timing gates how long it takes him.

Then we're going to switch the boards, so that the stripes are

vertical, so that it's a different type of visual information,

and we'll see how that changes things.

Well, it's quite dazzling as it is, so let's see how he does.

We'll have to repeat this several times

to get some precise timings, I presume, but he's very keen.

So we can compare Arnie's speed down the horizontal

and the vertical stripes.

He'll have to break the light beam at the start...

..and again at the finish...

..to get a precise time for how fast he flies down the corridor.

-Did it work?

-Yes, that's successful. Got a time.

-Excellent.

Come on, Arnie.

Good boy. Top work, top work. Down you get. On the perch.

-Yes, that worked.

-Yes? Excellent.

Arnie is performing admirably.

His flight times from one end of the corridor to the other

are coming in at less than two seconds.

-Everything they do is quick. Every motion is speedy.

-Yeah.

Good lad.

-Excellent.

-Slightly faster.

-Yes, that worked.

-Yes! Ten! He's a champion.

Arnie's done well.

We've got timings for ten flights through the horizontal stripes.

Now we're flipping the stripes to vertical.

So, how will that affect Arnie's speed?

OK, we're ready here. We're going to repeat the whole thing

-and contrast the results?

-Exactly.

Typical science. Fire up the starlings, Lloyd. Let's go.

-Arnie? Good boy. Are you ready, Rose?

-Yep.

So we've started to get some readings from the verticals.

Come on, there's a little scrap there.

On you go. Look at that. Beautiful. On you go.

The funny thing is that, even to my eyes,

there's something very weird looking about those vertical stripes.

Martin, I'm not sure about the starlings, but looking down here,

this is certainly a far more dazzling environment.

It's quite unpleasant, isn't it?

And Arnie seems to agree.

He's definitely not going as direct as he was the first run.

-No, definitely.

-That was the slowest time so far.

Could Arnie really have slowed down?

The results are in and we can now compare Arnie's flight times

through the horizontals and the verticals.

OK, so we've got a graph of the results.

First of all, we've got the horizontal stripes,

which is the blue line here.

And then the red line shows how fast it flew through the vertical stripes.

One thing that immediately strikes me is that it's very clear that,

when it's flying through the vertical stripes,

it never reaches the speed that it did through the horizontals,

suggesting to me that it was easier for it to fly down here

when the stripes were horizontal.

That's right, and it comes down to a neat trick called optic flow.

And that really relates to how much information passes over

the eye as the animal is moving.

Optic flow is a way the bird brain processes visual information

so that it isn't overwhelmed.

It filters out nonessential detail,

so the bird perceives simple patterns.

When Arnie flies through horizontal stripes,

that pattern changes very little.

He perceives the lines as a distant horizon, so it's safe to fly fast.

The vertical stripes on the other hand, those stripes are passing over

the eye really rapidly and changing very fast,

and that's simulating a situation

where there might be lot of objects very close to the bird,

and so it has to slow down to avoid the risk of collisions.

So when Arnie flies through the vertical stripes,

the pattern changes constantly and he perceives it as nearby obstacles.

This makes him fly cautiously - almost a metre per second slower.

The bird's mind has evolved an elegant way

to know how fast it's safe to fly.

C'mon, Arnie.

It's always fantastic to learn something new,

and I've been watching birds for years now,

and I've always wondered,

how do they fly through such cluttered environments

without ever bumping into things?

And it's all about filtering information,

not overloading their little bird brains.

Every time I look at a new animal,

I am constantly surprised by the sheer power of their senses...

..and the ingenious ways that they use them.

Some species seem to be able to interpret that sensory information

to understand almost everything about the world around them.

But there is one thing that I've always wondered.

Can they use those senses to go beyond this, the physical world,

and grasp abstract concepts like we do?

Things like time, for example.

For humans, time is a concept.

To keep a close track of it, we depend on clocks.

But can animals use their senses to understand time?

To try to find out, I'm going to test an old myth about dogs -

that they can tell exactly when their owner is about to return home.

Meet the owners of Jazz, the Hungarian Viszla.

Now, they're convinced that Jazz knows exactly

when his master, Johnny, is about to come home.

And to witness this, we've left cameras

running all over their house for a week.

The family have a regular routine.

Christine and Johnny always leave the house

at the same time in the morning...

..leaving Jazz to his own devices.

And every evening, Christine comes home at four o'clock.

But it's what Jazz does next that really interests us.

You see, every evening at around 4:40,

20 minutes or so before Johnny comes home,

Jazz always leaps up onto the sofa as if he's waiting for him.

He's like a canine alarm clock.

Between half four and five, Jazz is always looking out for Johnny.

It seems Jazz somehow knows that Johnny's coming home.

And it's a claim made by many dog owners.

But how does Jazz do it?

Now it could just be that Christine coming home

sets Jazz's clock.

We know it's not because he needs dinner or his walkies,

because Christine's dealt with that.

There is a theory that a dog's sense of smell could play a role.

While Johnny is out of the house,

the smell he leaves behind fades at a regular rate.

So could it be that when Johnny's scent

drops to a particular level, Jazz senses he's about to return?

To test this theory, at the end of the week, we made a change.

On her way home, Christine swung by Johnny's football club to get

some of his freshly worn t-shirts.

And then, when she got back at her usual time, she wafted them

around the living room to spread Johnny's smell around.

If Jazz is using the fading smell of Johnny

to sense the passage of time,

then this should be the equivalent of re-setting the clock.

So will Jazz still know what time it is?

It's now less than half an hour before Johnny normally comes home,

but for the first time, Jazz stays dozing.

It's now 4:48.

Jazz only lifted his head for about 30 seconds.

He's lying flat out again, enjoying the heat at the radiator.

Now Johnny's back...

Are you coming a walk?

..and to Jazz, it seems to come as a complete surprise.

Now, let's not pretend that this is scientific.

There could be any number of things that Jazz is reacting to.

But it's an intriguing idea that dogs' sense of smell

might allow them to grasp something as abstract as time -

a concept that we tend to assume only the human mind can understand.

So how could an animal's mind take in information from the senses,

and draw from it an understanding of something

that's not physically present?

Well, now, for the first time, we are beginning to uncover

what might be happening inside their brains.

In Atlanta, neuroscientist Greg Berns is adapting a harmless

medical technique to study brain activity in dogs.

OK, stand by. We're going to start the noise.

LOUD DRONING SOUND

MRI is a technique that's been used in humans for over 20 years.

Normally, we use it to study what the brain looks like,

but with a few tricks, we can do what's called functional MRI

which looks at brain activity, and, by analysing the data,

we can figure out what parts of the brain are doing what.

But doing MRI on animals is an entirely different game,

mainly because of the requirement that the subject

has to hold absolutely still.

The need to keep still makes it impossible to scan most animals

unless they're sedated - not a good way to study their brains.

One, two, three, steps!

But Greg has teamed up with Mark Spivak to devise a programme

to train dogs for the bizarre conditions they'll face.

The key is a steady supply of snacks.

Well, a lot of humans have difficulty taking MRI.

First of all, there's the enclosure,

which provokes anxiety in many humans.

Second, there's the absolute motionlessness required.

And then there's the noise.

LOUD DRONING SOUND PLAYS

Without proper conditioning and training,

the dogs would just run scared from the MRI.

Come here, girl.

Those that pass the test graduate to the real thing, like Kady.

MRI is painless and it does no harm.

It's at the very cutting edge of animal science.

And it's beginning to give us some fascinating insights.

Patricia, we're going to begin the first scan with the localiser.

Are you ready?

One of Greg's earliest experiments is revealing important clues

as to what happens in a dog's brain

when it receives information from its senses.

First, he's looking at a visual signal.

So Kady's in the scanner right now

and Patricia's actually giving Kady hand signals.

We've already taught the dogs through lots of practice

that this means food.

OK? So every time Patricia makes this signal,

we're going to be looking in her brain, what that response is,

and we're actually going to be looking at a very specific area

called the caudate nucleus.

We also have another hand signal that looks like this,

and that means no reward.

After scanning many dogs,

Greg's results show the area of the dog's brain that responds.

If we look very closely, we find that the area that's common to all

the dogs corresponds exactly to the same part of the human brain

that responds to reward.

Rewards like money, music, food...

All the things that humans like, it's also activating in the dog's brain.

Even though Kady isn't actually seeing food, she can take

a piece of visual information and interpret it to anticipate

that she will receive food and she's responding emotionally.

Just like we do.

This was pretty amazing because it didn't have to be that way.

Dogs could be so different from us that they might have responded

completely differently, but that doesn't seem to be the case.

And when you think about what this requires the dog to do,

it reveals a complex chain of thought.

The results are showing that dogs, and probably most animals,

have brains and minds that are far more sophisticated

than we ever gave them credit for.

These are remarkable and tantalizing insights.

Yet, so far in this programme,

we've been exploring how the animal mind is shaped by the senses

we ourselves possess.

Vision...

hearing...

smell...

taste...

and touch.

But these are not the only senses in the natural world.

Out here, there are other physical forces that we simply haven't

evolved the ability to be able to detect.

So what I want to do now is take a look at a group of animals

that go beyond these five senses that we know,

to perceive the world in a way that would be entirely alien to us.

To do that, I've come to the island of Bimini in the Bahamas.

It's a hot-spot for an animal that's always fascinated me.

With me is scientist Eric Stroud.

He's spent years studying sharks.

Sharks are extremely successful predators.

They can smell tiny quantities of blood over huge distances

and follow minuscule vibrations of their prey in the water.

But the shark sense that I want to investigate is very different.

It's one that we humans have no experience of at all.

Try and push them into here, yeah?

If you can get him against the fence, you have a better shot.

Eric is going to demonstrate that sense with a strange experiment.

But first, we need our baby lemon shark to stay nice and still.

-OK, got him.

-Look at that!

OK, so we're going to roll it over and place it into tonic immobility.

Tonic immobility?

-Go on, explain that one.

-No-one's really sure why it happens,

but when the sharks are inverted like this, they kinda go to sleep.

Wow. It's just relaxed.

It's like yoga for sharks.

-Indeed.

-And there's nothing to suggest that it's stressed.

I'm barely holding it.

I'm going to hand him to do you, OK?

Just put your thumbs behind there and hold...

-OK, ready?

-These things obviously can bite. What would be the damage?

A laceration, at this age.

You might need stitches, actually, from this little shark.

So, if anything goes wrong, just let it go.

Let's do our experiment.

Eric's experimental kit is really simple.

Steel spoon and a magnet. Thanks.

I've been left holding the shark!

I'm not sure whether that's an enviable position to be in or not.

We have a strong magnet here we're going to use for the experiment,

and it's a pretty powerful magnet.

It'll attract the spoon out of my hand.

Eric wants to show me how our shark reacts to the magnet.

So what we're going to do is put a blinder by the shark's eye

so he can't see what I'm doing.

So the shark won't be able see the magnet coming.

OK, I'm going to put a blinder here.

But will he sense it?

I'm approaching...

Oh!

That was a reaction!

-Wow, he jumped out of your hands.

-He did.

Our little shark is completely unharmed,

but he's acutely sensitive to Eric's magnet.

Why?

Well, it's down to a clever piece of sensory anatomy.

Sharks have organs called the ampullae of Lorenzini,

which appear as dark openings along the front of their noses.

These are the ends of jelly-filled tubes that can detect

the voltage difference between the tube's opening and its base.

They are exquisitely sensitive,

able to pick up billionths of a volt.

Biologically, we humans have no mechanism like this.

To us, the ability is completely alien.

But why would a shark need such a sense?

It helps them to find food. It's predation.

They can locate the heartbeat of a crab or stingray underneath the sand.

When that animal is beating or moving,

the muscles generate a very weak electromagnetic field,

and that's what their noses are gearing in on.

We're, in a sense, simulating that.

The movement of the magnet across the shark's nose

induces that electromagnetic current,

but we're just doing it many times greater than a stingray or a crab.

-So, it's sensory overload.

-Exactly.

-Hence the struggle.

-Exactly.

At low levels, this sense allows sharks to find their prey.

But at high levels, it repels them,

just as we need light to see,

yet would recoil from dazzling headlights.

But is this effect powerful enough to change a shark's behaviour?

We're heading from Bimini to Triangle Rock -

a well-known gathering place for large Caribbean reef sharks.

We've been joined by marine biologist Pat Rice.

We're going to pit a shark's magnetic sense

against what must surely be their most powerful instinct -

their urge to eat.

Here they are. Look! Caribbean reef sharks.

Slap it on the water.

-Oh!

-Beautiful sharks, aren't they?

They're stunning. Absolutely stunning, aren't they?

So, they're here. Let's get going.

Stunning they may be, but to do the experiment,

I'm going to have to jump in with that lot.

I know they're only two metres, but they look a little bit bigger

than I imagine a two metre shark. Maybe it's the water.

Maybe it's acting as a lens and exaggerating their length.

Pat now needs to set up the experiment

eight metres down on the sea bed.

What we're going to do here is perform a very simple,

but hopefully effective, experiment.

And what I've got in my hand here is an extremely powerful magnet.

That's why I'm not coming too close to the camera or you will never

see this, it'll wipe everything in there.

And we're going to make a circle of these magnets on the bottom,

and in the centre of that circle, we're going to place some food.

On the sea floor, Pat and safety diver Vincent are setting up

the circle of magnets, into which we'll put our bait.

We need to be sure the sharks aren't simply

deterred by a circle of black objects, so Pat's made

a second circle of ordinary bricks covered in black tape.

We'll put bait in the two circles and see what happens.

The magnets are powerful, but will they repel the sharks?

Essentially, what we're trying to test here is whether the sharks'

sensitivity to these magnets will overcome their desire to feed.

Time for me to join Pat - and a whole load of sharks.

Jump!

I'm told the sharks in this spot have never yet attacked a human.

But to do this experiment, we need to deliberately

tempt them in very close.

We've arrived on the bottom.

On this side is the ring of bricks - the placebo, if you like.

And here on this side is the ring of magnets.

And now what we've got to do is introduce the bait.

OK, we've got sharks here already. They're coming in.

Pat's got some bait here, some tasty tuna.

We're going to try and fix this in the centre of each of the circles.

We're in the water with hungry sharks,

and in our bare hands, we've got some fish.

This is like a peculiar game of Russian roulette, isn't it?

All of those sharks up by the boat will now be able to smell

the bait down here with us.

Here comes a shark now.

It's bypassed the magnets...

and it's gone straight into the brick circle

and it's taken the bait.

Now there's no bait in the bricks,

will they show an interest in the bait in the magnet circle?

Look at that! It turned as if it could sense that bait,

and it turned away.

It can tell there's food there.

It must be able to see all of the other fish currently

feasting on it but it wouldn't go inside that ring of magnets.

Time to put fresh bait in the bricks.

And I've barely had a chance to retreat

when a shark makes straight for the brick circle again.

Look at that. It's a monstrous great animal.

But so far they haven't touched the bait in the magnets.

It's 2-0.

It tweaked them and definitely flinched away.

And yet, they're clearly hungry.

Not me. No, not me...

We're down to our last piece of bait for the brick circle...

and it doesn't last long.

It's snaffled the food from the brick circle.

But there's no doubt the magnets are repelling the sharks.

It seems almost confused by those magnets.

And the bait remains in the circle.

Although undetectable by us,

in the sharks' mind, our magnetic force-field is overwhelming.

So strong, it even overrides the shark's primal urge to feed.

This exploration of animal senses has been a first

and a fascinating insight into the animal mind,

and I've been surprised.

The way that they experience and understand their world

is far more sophisticated than I would have imagined.

But above all,

I've learned that it's the animal senses that shape the animal mind.

It's those senses that make every single species,

including our own, unique and special.

Next, we'll be meeting the animals with the most powerful

problem-solving minds on the planet.

How on earth did that crow do that?

We'll find out how apparently

simple animals can crack problems that would baffle humans...

..and pit them against other animals I'd like to think of as clever.

All you've got to do is lift the ball!