Who Is in Control? The Brain with David Eagleman

Who's in control of what you do?

This sounds like a simple question, but the facts might surprise you.

Almost every action that you take...

PROTESTERS SHOUT

..and every decision that you make...

..and every belief that you hold...

..these are driven by parts of your brain that you have no access to.

We call this hidden world "the unconscious".

And it runs much more of your life than you would ever imagine.

In this film, I'm going to investigate the weird ways

our brain secretly controls everything that we do.

God, that was amazing!

How, without our awareness,

the brain controls the complex machinery of the body.

And makes decisions without our awareness.

This is the story of everything the brain does

that remains hidden from us.

It is the story of who's really in control.

It's first thing in the morning

and the streets here are almost completely silent.

But all around me,

one of the most remarkable events in the universe is taking place.

In all of these houses, one by one,

human consciousness is flickering to life.

One of the most complex objects in the known universe

is becoming aware that it exists.

ALARM BLEEPS

FAINT ALARM BLEEPS

ALARM GROWS LOUDER

RUSH OF TRAFFIC, SIREN BLARES

This is the birth of YOU and this little miracle happens every day.

Waking up is the moment when our conscious brains come online.

But it's also the beginning of a great deception.

It feels like YOU are in charge of all the decisions

you're about to make.

Like YOU are running the show.

But it's not quite that simple.

Take a moment to think about what it is to be conscious.

To be aware of the world around you.

Thinking about what you're going to have for breakfast...

or what you're going to do next.

When you're consciously aware,

it feels like that's all that's really going on inside your head.

But here's the surprise...

All of that conscious you

makes up the smallest bit of the activity in your brain.

The conscious you thinks it's the captain of the ship...

..but in truth it's nothing more than a stowaway.

So, what is all this hidden activity inside our heads?

A large part of it is dedicated to something

that most of us take for granted.

Operating the body.

Most of the actions we make, even those that seem intentional,

are automatic and unconscious.

CROWD YELLS

We can see this very clearly in a situation

that demands a fast response.

I'm about to face a fastball from Matt over there on the mound.

In order for me to hit the ball,

there's a very complex series of processes

that has to happen in my brain.

He pitches at 92mph,

so that doesn't give me very much time to hit the ball.

OK, ready!

HEAVY WARPING TONE AS TIME SLOWS

AMPLIFIED WING BEATS

The ball leaves the mound and starts on its way to the home plate.

This journey of 60 feet, six inches

will take place in around four tenths of a second.

And in that time, there's a huge amount for my brain to do.

The light from the baseball needs to hit my eye...

..work through the many miles of circuitry in my brain...

ELECTRIC PULSING

..and send signals to my muscles to swing the bat.

This entire sequence unfolds in just a fraction of a second.

BOOM!

But here's the surprise.

My conscious awareness hasn't yet had time

to register what's going on.

I strike the ball without thinking

and only become aware of what's happened after the event.

By the time the conscious mind gets the information,

it's already old news,

and this is because the ball simply travels too fast for me

to be consciously aware of its position.

And this is not just true of baseball,

but in all areas of our life.

NEON LIGHT BUZZES

Every day, behind the scenes, the unconscious parts of our brain

are hard at work helping us to accomplish

even the most basic of tasks.

Take drinking a coffee.

It seems incredibly simple

but, under the hood, our brains must unconsciously coordinate

and make sense of trillions of electrical impulses.

ELECTRIC PULSING

As I touch the cup,

my nerves transmit reams of information to the brain

and that helps me to estimate its weight...

..its position in space...

..its temperature.

My ability to control the cup relies on electrical impulses

going back and forth from my hands and muscles to my brain

and back again.

Many of these signals will be sorted and processed in the cerebellum.

Here, specialised neurons with up to 200,000 connections each

help calculate the millions of micro-adjustments needed

to achieve the smooth movement of the body.

RAPID ELECTRONIC BLEEPING

And yet, all of this remains completely hidden from me.

I simply enjoy the experience of drinking my coffee.

Every day as we move, hidden from view,

our brains unconsciously process

trillions upon trillions of calculations.

This unconscious processing is what allows us

to move with effortless grace through the world.

It's a feat so remarkable

that we have yet to build a machine

that comes anywhere close to it.

In fact, we've only just begun to discover

the techniques that the brain uses to make its many calculations.

There's so much that our brain does that's hidden from us,

we often take for granted what's going on up there.

But what would it be like if some of these unconscious skills

were taken away from us?

What amazes me, you know, you sit on a bench somewhere,

just watch people walking by

and you're sort of thinking,

"You're doing that so fluidly

"and so seamlessly, totally unaware of this amazing system

"that's managing that process for you."

At the age of 19,

Ian Waterman suffered a rare type of nerve damage.

Now every tiny detail of movement requires intense conscious effort.

I lost the ability to manage my body automatically.

That system that works in here somewhere,

that we develop as we stand and tumble and fall as a baby

and we develop as we grow - gone.

For most people,

this condition prevents any kind of coordinated movement,

but over time Ian has learned to treat his body

like a complex puppet.

Ian has spent years analysing movement and working out

how to perform each tiny flex and bend that the human body can make.

Mustering an incredible mental focus,

Ian is now able to put these all together to make himself walk.

For Ian, walking is a monumental triumph of skill, dedication

and concentration.

It's an amazing loss and it's a significant cognitive effort

to replace what comes automatically within us.

It's an astounding facility that the body has to manage itself.

You just don't know what it is until it goes.

Next time you see a person moving, take a moment to marvel.

Not just at the beauty of the human body,

but at the power of the unconscious brain that's orchestrating it.

Our unconscious brain is capable of some truly remarkable feats.

But why is so much of what we do buried out of reach?

To answer this question,

we can take a peek into the mind of a champion.

This is Austin Naber. He has set world records for cup stacking.

Nothing you are about to see has been sped up in any way.

Austin, that was terrific. How long have you been practising this?

Um, two years and ten months.

-And do you practise every day?

-Yep.

How many hours?

Um, at least three or four.

And when you first started this, how fast could you do it?

Um, two minutes, two and a half minutes.

-To do the same routine you were just doing?

-Yeah, the cycle.

OK, and how quickly can you do it now?

-Five seconds.

-Five seconds? Wow, that's quite an improvement.

So, when you're doing that, are you thinking about what you're doing?

-Not really.

-You're just letting your hands do the work?

Mm-hm.

Watching Austin stack cups,

you might expect that his brain is working overtime.

Having to coordinate these complex actions so quickly,

it seems like his brain must be burning a lot of extra energy.

HE LAUGHS God, that was amazing!

'But the real story's not quite that simple.

'To gain a better insight into what's happening here,

'we have to peek inside the brain.'

-Austin, how does the cap feel on you?

-Good.

'The skullcaps we're being fitted with are devices for measuring

'electroencephalography, or EEG.

'They read electrical signals from the scalp to reveal clues

'about the activity going on inside the brain.'

'Conductive gel is injected at various points

'to help boost the signal.'

So, all the lights on your head are turning green, which is good.

There's a good connection there.

'With both of us rigged up,

'we now have a window into the electrical world within our brains.'

So, now we're going to race.

'And we can see how much effort it takes our brains to cup stack.'

-You ready?

-Mm-hm.

Set, go!

Looking at the EEG, you can see that my brain is working full tilt.

My conscious mind is actively searching for ways

to best perform this task,

and figuring out what to do next.

It means there's a lot of electrical activity happening in my brain,

and a lot of energy being expended.

In contrast, Austin's brain is serene.

Despite the speed and complexity of what he's doing,

his brain is in an almost rest-like state.

HE LAUGHS

I'm...right there behind you!

'So, how is he able to do this?'

Austin's talent is a result of physical changes in his brain.

During his years of practice,

a specialised set of connections has been formed.

He's carved the skill of cup stacking into the structure

of his neurons.

This allows Austin's brain to perform this task rapidly

and efficiently.

As we learn new skills, they change the structure of our brains.

They move from software to become part of the hardware of the mind.

It means Austin can even do this...

blindfolded.

When we practise new skills, we physically hard-wire them.

Some people talk about this as "muscle memory".

But it doesn't have anything to do with our muscles.

All the changes are orchestrated across the vast seas of our brain.

It's not just about cup stacking.

As we develop from childhood,

we all begin to acquire these burnt-in circuits.

Everything from walking...

to tying laces.

Typing...

..to riding a bike.

All of these are skills that get hard-wired into the structure

of our brains,

making them automatic and energy-efficient.

Despite the vast amount of information it processes,

the human brain requires only as much energy

as a 60-watt light bulb.

But there's a consequence to hard-wiring.

These skills become hidden from us.

They become unconscious.

I don't know how I'm riding this bike.

The small corrections of the handlebars,

the micro-corrections of my balance.

And this is the same with all new skills that we learn,

whether it's cycling, or reading, or typing,

or driving a car, or playing the piano.

We lose access to the sophisticated programmes that we're running.

'And this can cause some odd effects for our conscious mind.'

HORN BLARES

Take the feeling commonly referred to as "autopilot".

Most of us will have experienced it while driving.

You're cruising along,

and suddenly you're halfway home,

with no memory of how you got there.

This sensation happens because the driving is being performed

unconsciously and automatically.

Brains can be trained to perform almost any skill automatically.

And some of them can seem almost superhuman.

Through intense practice, the brain's ability to run on autopilot

can be harnessed to achieve some extreme feats.

Free solo climbing is climbing without anything but your body.

There's no ropes, there's nothing holding you onto the rock

but your hands and your feet.

This is Dean Potter.

From the age of 12, he's dedicated his life to climbing.

These years of practice have hard-wired this incredible skill

into the structure of his brain.

But Dean's real challenge is to let these hard-wired skills

run without conscious interference.

A moment's hesitation, or stray thought, could spell disaster.

To stay alive,

Dean has to give over complete control to his unconscious.

HE GRUNTS

My most pinnacle moments are when I completely go away,

consciously, and I find myself at the top of the rock.

It's kind of like blackout.

I'm... Don't know what happened.

Um...

But I'm on the top of the rock.

As Dean climbs, he enters what's known as a "flow state".

It's a form of brain activity experienced by different

kinds of people, from meditation experts, to elite athletes,

to professional musicians.

It's sometimes referred to as "the zone",

and it arises during total immersion in a task.

In flow states, the neural circuits are able to run

without the conscious mind interfering.

When Dean enters a flow state, he operates without distraction

and without fear.

My perception is heightened.

What I'm seeing is much clearer.

The particles of dust in the air in front of me.

Very subtle noises,

or things that happen very fast become slowed down.

I'm no longer in my rational thought.

I'm in my...um...

unconscious thought, where I'm just moving on the rock.

I stop thinking about what I'm doing and I just do.

We all have chatter when we're thinking of all the things in life.

We all walk around with all this weight on us.

Things we're worried about, or things we're hopeful for.

Things that aren't...

Like, really, they don't have to do with where we're at.

And, for me, danger eliminates all that.

The reason I'm doing all these things isn't to climb the rock.

The reason I'm doing it is to enter the heightened state.

So, it doesn't matter what I'm doing.

If I can enter that heightened state, I'm happy.

Months after this interview,

Dean lost his life in a wingsuit accident in Yosemite National Park,

doing what he loved.

PULSE THROBS

The hidden parts of the brain can take total control over our bodies.

But it's also capable of shaping our lives in more profound ways.

The man who would begin to uncover this

revolutionised the way we think about who we are.

His name was Sigmund Freud.

In 1938, Sigmund Freud was fleeing from the Nazis in Austria.

And he moved here, to this house in London.

Freud was one of the 20th century's most influential thinkers,

and that's because he ushered in a new way of thinking about

why people behave the way they do.

Freud's fascination with the brain had begun at medical school

in Vienna, where he specialised in neurology.

After graduation, he set up a private practice,

treating patients with psychological disorders.

Fascinated by what he saw,

Freud soon began formulating radically new ideas

about the unconscious mind.

ARCHIVE RECORDING:

Freud would become the founder of psychoanalysis -

an approach that put the focus on understanding

what's beneath conscious awareness.

Ruth McCall is a psychoanalyst with a special interest in Freud's work.

Before Freud, there was very little help.

Freud pioneered a method of getting people just to talk.

To try and get people to expose themselves through words.

He would get people to lie on what he called a couch,

and he sat behind them.

Because when you break the linkage of eye-to-eye contact,

people stop speaking to another person

and they begin to speak a bit more to themselves.

And that, we feel,

leads to threads that have their end point in our unconscious.

In an era before brain scans or powerful computer simulations,

Freud's couch was his window into the world of the unconscious.

Freud paid close attention to the information that was contained

in slips of the tongue,

and he hypothesised that all of this

results from unconscious motivations.

So, by paying attention to what was poking above the surface,

Freud felt that he could get a good sense of what was lurking below.

Freud had seen that beneath the surface of each of us

lies a swirling sea of hidden motivations,

and drives, and desires.

The way we think, and feel, and act

is profoundly influenced by this unconscious.

Freud would be just one of many explorers of this brave new world.

As the 20th century progressed,

many other scientists began designing experiments

to shed light on the mysterious workings of the mind.

They were trying to uncover how much control

our consciousness really has.

But what they were to discover would be far stranger

than anyone imagined.

Take an experiment run in the mid-1960s by Eckhard Hess.

It was a simple experiment.

He asked men to look at photographs of women's faces

and make judgements about them.

How kind does she look?

How selfish or unselfish?

How friendly or unfriendly?

And how attractive?

It seems like a straightforward enough task,

but as is often the case with psychological experiments,

there was a catch.

Unbeknownst to the subject, the experiment had been manipulated.

In half of the photographs,

the women's eyes had been artificially dilated,

so it was the same woman, but with different-sized pupils.

Dilated eyes are, among other things,

a biological sign of sexual arousal.

This was to drastically influence the choices that the men made.

But without them being aware of it.

It turns out that the men found the women with dilated eyes

to be more attractive. Now, here's the important part -

none of the men explicitly noticed that there was a difference

in the size of the pupils and, critically, none of the men knew

that dilated eyes is a biological sign of sexual readiness.

But their brains knew and what they were doing was

running deeply-carved evolutionary programmes

steering their decision-making towards the right sort of mate.

The subject's brains were recognising and analysing

tiny details in the pictures

and acting on them.

All of this was happening without a flicker of conscious awareness.

This kind of experiment reveals something

fundamental about how brains operate.

The job of this organ is to gather information from the world

and steer your behaviour appropriately.

And it just doesn't matter whether your conscious awareness

is involved in that or not.

And most of the time, it's not.

Most of the time, you're not aware of the decisions

that are being made on your behalf.

Hess's experiment is just the tip of the iceberg.

LAUGHTER AND CHATTER

'Today, researchers have uncovered a whole range of scenarios

'in which our unconscious brains make decisions

'or change our behaviour without us realising what's happening.'

-Here you go.

-Thanks.

'Here are just a few of the stranger ones.'

If you're holding a warm cup of coffee,

you'll describe your relationship with your mother as closer

than if you're holding an iced coffee.

When you're in a foul-smelling environment,

you make harsher moral decisions.

If you happen to find yourself

sitting next to some hand sanitiser, that shifts your political opinions

a little bit more towards the conservative side,

presumably because it reminds your brain about outside threats.

Every day, we're influenced in countless ways

by the world around us and most of this flies

completely under the radar of our conscious awareness.

'Totally hidden from us, the unconscious brain is continually

'reacting to the outside world and making decisions on our behalf.'

So, all this might leave you wondering -

why aren't we just unconscious beings?

What exactly is the point of consciousness?

Well, we can gather the first clue by looking at what happens

when we encounter something unexpected.

Although most of the time, your brain can run on autopilot,

when you come across something you weren't expecting...

..your conscious mind is called into action.

It works to figure out if this new thing is a threat or an opportunity.

This is one of the jobs of consciousness -

to assess what's going on, to make sense of the situation.

When your expectations are violated,

consciousness is summoned up to work out the appropriate reaction.

BUZZING

But that's only part of the story.

Consciousness isn't just about

reacting to unexpected events in the outside world.

It also plays a vital role in resolving internal conflict

among the brain's many automatic subsystems.

To understand the role consciousness plays,

I'd like to imagine the brain as a vast sprawling organisation.

One with many thousands of divisions and subdivisions.

All collaborating and interacting and competing.

I think of consciousness like the CEO of a large corporation.

When a company is small, it doesn't need a CEO.

But once an organisation reaches sufficient size and complexity,

then it needs someone to rise above the daily details

and take the long view.

Within the brain, there are thousands of automated departments,

each working on its own task.

Some departments can overlap and collaborate,

but what happens if there's a conflict between them?

Say you're hungry, but you're on a diet?

Or you feel sleepy, but you have an important deadline?

When this happens, it's time for the boss to get a call.

TELEPHONE RINGS

In the event of an internal conflict, your conscious mind

tries to work out what's best and make an executive decision.

Consciousness is the arbiter

of conflicting motivations in the brain.

It has a unique vantage point,

one that no other part of the brain has access to.

Think of consciousness as a way for trillions of cells

to see themselves as a unified whole.

It's a way for a complex system to hold up a mirror to itself.

Consciousness is one of evolution's greatest creations.

It allows the brain to arbitrate the vast workings of the unconscious.

It allows the brain to react to unexpected events.

And it allows the brain to see itself.

In acting as a long-term planner, consciousness has led us to become

the most successful species on the planet.

But what happens if consciousness goes off-line?

If the unconscious parts of our brain

are given complete control of our actions?

In Toronto, in 1987, a 23-year-old man named Ken Parks would find out.

The incident began when he fell asleep in front of his television.

He went to sleep

and he woke up maybe, perhaps an hour later.

No, I shouldn't say he woke up.

Er, he got up - big, big difference.

He, er, left the house with his keys,

did not lock the door, which he normally does...

-ENGINE STARTS

-..got into his car.

He drove 23 or 24km...

BRAKES SCREECH

-..made four right-hand turns...

-INDICATOR CLICKS

..ended up in his in-laws's driveway,

entered through the basement, where they slept...

..strangled his father-in-law, not to the point of death,

but strangled him to the point where he was immobile.

He then went to the kitchen, er, found a long knife,

and stabbed his mother-in-law, er, five or six times,

and beat her with something, to the point where she fractured her skull.

Ken then left their house and drove about a block away

to the police station...

walked in, hands bleeding, and he went over to someone

who came to his assistance and said, "I think I've just killed somebody."

To most people, Ken's guilt seemed obvious.

But he appeared to have no memory of what had happened, or how.

Ken was lying in a bed, er,

with his hands completely bandaged,

um, and...was bewildered.

That's the way to describe him. Completely bewildered.

Lost. Unable to understand what had happened, why it had happened,

and some part of him wanted to ask the question, "Who did it?"

Ken had a good relationship with his in-laws

and everyone agreed he had no motive for the crime.

Marlys began to suspect that something must have gone wrong in

Ken's brain and she assembled a team of experts to help figure out what.

They soon began to suspect

the events might be connected to Ken's sleep.

In prison, Ken was visited by sleep expert Dr Roger Broughton.

His findings were to prove a revelation.

They wired him up...

..and they watched his sleep pattern for the first night.

And then, the second night, they woke him up occasionally

to see how fast he would go back to sleep.

And then, they determined that the profile of the sleep pattern

was consistent with that of a sleepwalker

that could, er, move involuntarily and do specific kinds of actions.

As the team began investigating,

they found sleep disorders of all kinds

throughout Ken's extended family.

With no motive, no way to fake his sleep results,

and such extensive family history of sleep problems,

Ken was acquitted of the murder charge.

The verdict was stunning.

It was a moral vindication for Ken.

It wasn't that he didn't do it,

but there was no fault associated with it.

He didn't wish it to happen, he didn't will it to happen,

there was nothing he could do to stop it,

it was completely outside of his control.

The judge leaned down and said, "Mr Parks, you're free to go."

He opened the door and walked out with me.

After the trial, Ken was prescribed medication for his sleep disorder

and it was decided that he no longer posed a risk to those around him.

The case illustrates that people can carry out

extreme and sophisticated behaviours with no conscious awareness.

Our unconscious brains steer our behaviour.

But how do our brains come to be the way they are?

Why are there differences between us,

making you and me behave differently when faced with the same choices?

To answer this, we need to look one level deeper,

to how our brains get built,

and that begins with our genes.

The genes you come to the table with

can have an enormous influence on your behaviour.

Consider this - about half of the population

carries a particular set of genes,

and if you have these, your chances of committing a violent crime

go up by 882%.

The overwhelming majority of prisoners carry these genes,

as does almost everyone on death row.

So we can't presume that everyone is coming to the table

equally equipped in terms of drives and behaviours.

By the way, we summarise this set of genes as the Y chromosome.

If you're a carrier, we call you a male.

Obviously, your gender is determined by your genes.

But from there, how your DNA relates to your behaviour

becomes a little more complex,

because although you come to the table with a fixed pattern of DNA,

not every one of your genes will get the chance to play a part.

Genetics is only part of the story of who you become,

because which of your genes express and when,

this is influenced by the details of your environment.

So the family that you are born into and the neighbourhood,

and the culture you find yourself in, all of these interact with your

genetics and this sends brains off on very different life trajectories.

LOUD CRACK AND RUMBLING

The activity of our billions of neurons

is shaped by the internal and external world.

Both our genetics and our environment collaborate

to build our brains and thereby steer our behaviour.

Put the same infant brain in a different time or place,

and it will mould to fit that setting.

Culture.

Ideas.

Belief systems.

All these variables in our environment interact

with our genes to physically change the structure of our brains.

And this, in turn, defines who we have the chance to become.

Our freedom is constrained by the world we happened to drop into.

When you look at the brain this way,

it seems clear that we are not the ones steering our own lives.

At least, not nearly as much as we would like to believe.

All this might leave you wondering

whether the conscious mind is ever truly in control.

Are there any decisions that can be made independently of your history?

Do you have free will of any kind?

It's a question philosophers and scientists have grappled with

for centuries, but in the last few years, a small number

of neuroscience studies have begun making inroads into the problem.

We generally think that when

we choose to do something,

that there must be some activity in the brain that has to do with

that thing of choosing.

But it appears that nothing in what we can record in brain activity

clearly points to something in the brain

ascribed to this thing of choice, of free will.

The mystery of free will has intrigued many neuroscientists,

but Alvaro and his team will be the first to explore it

using a technique known as transcranial magnetic stimulation,

or TMS.

TMS, it is really a way to induce current in a specific target

of the cortex of the brain,

without having to do surgery,

without having to open up the skull or the skin.

TMS can be used to initiate involuntary movement.

This would lead Alvaro to design a simple experiment

to explore free will.

What we want you to do is look at that computer screen...

When participants saw a red light on screen, they had to decide

which hand they were going to move, but not actually make the movement.

When the light turned yellow, they were given a burst of TMS.

When the light went green,

they simply had to move the hand that they had chosen.

Alvaro found that by targeting certain areas of the brain

with TMS, he could make participants change their mind.

So what happened there?

I seem to have planned to move my right but then at the last second,

I changed my mind. I'm not sure why.

This is the TMS response.

You see a little pause

and then this squiggly line is the voluntary movement.

It was clear that TMS was causing the participant's movements,

and yet many people remained convinced that they had made

choices with their own free will.

More often than not, a subject would say,

"I did that."

We would look at the recordings and say, "No, you didn't."

And they would say, "Oh, sure, sure, I did, I did."

So that was striking because it turned out subjects interpret

anything that moved as their own choice, even though it wasn't.

Alvaro's experiment reveals how good the conscious mind is

at telling itself that a free choice has been made,

even when it hasn't.

Demonstrations like these are tantalising, but the truth is,

science has yet to devise a conclusive experiment

that proves or disproves the existence of free will.

It may be that our science is just too young to know how to look for it

or it might turn out that free will IS simply an illusion.

But if we really don't have it at all,

what would that mean for our lives?

What if there is no free will?

What if we are just systems that move from one state to the next

in a completely predictable manner?

A life that is totally predictable like that wouldn't really be

worth living out, would it?

But the good news is this - in practice,

predictability is impossible.

Let me show you what I mean with a simple ping-pong ball.

As the ball enters the box,

it is possible to predict very accurately

where it is going to land.

But as it begins to trigger other balls,

things start to become more complex.

MUSIC: Blue Danube Waltz by Johann Strauss II

Any error in the initial prediction,

no matter how small, becomes magnified as balls collide

and bounce off the sides and trigger other balls.

Soon, it becomes completely impossible

to make any kind of prediction about how the balls will end up.

The balls have no choice in the direction they move.

They have no freedom to do it differently.

And yet, the system is completely impossible to predict.

MUSIC FADES

Your thoughts and your feelings and your decisions,

all of these emerge from the innumerable, ongoing interactions

in your brain.

This box has 150 ping-pong balls in it, but your brain

has billions of times more interactions than that every second,

and for your whole life, it never stops.

What's more,

each individual brain is embedded in a world of other people's brains.

The neurons of every human on the planet fire and interact

and influence each other, creating a system of unimaginable complexity.

This means that even though brains follow predictable rules,

in practice, it will always be impossible to know exactly

where any of us are going.

Our conscious minds play a much smaller role in our lives

than we once imagined.

Everything - from what we do,

to who we are -

is orchestrated by the unconscious brain.

The cosmos turned out to be larger

than we had ever imagined from gazing at the night sky.

And in the same way,

the universe inside our head

extends far beyond our conscious experience.

Today, we are getting the first glimpses

of the vastness of this inner space.

The human brain is nature's perplexing masterpiece.

It's the most wondrous thing we've discovered in the universe,

and it's us.

Next time on The Brain - I'm going to investigate the weird ways

our brains are constantly making decisions.

Some we are aware of,

most we are not.

OK.

Can you tell me what you're seeing? So this is very simple.

'Without him knowing it, his brain will decide

'whether this is a rabbit or an ostrich.'

STATIC BEEPING

This is the sound of a decision getting made.

We are eavesdropping on single neurons working in concert

with billions of other neurons to land on a choice.

And this is what every decision in the history

of the human species looks like.

Traditionally, we assume that humans are rational decision-makers.

They take in information, process it and come up with the best answer.

I'm wondering whether to eat this yoghurt at all,

because part of me wants it but part of me knows that it's fattening.

Deciphering what we hear or see or smell -

these are decisions.

Falling in love,

giving in, resisting.

Decision-making is what allows us to navigate a course through life.

And your lifetime of choices

has sculpted you into the person you are

right now.