Hey, 42 here. Why did you click on this

video?

Perhaps it was the thumbnail, or maybe

the title caught your eye. Whatever it

was, you made a conscious decision to

click. Hey, 42 here. Why did you click

on this video?

Or did you? What if I was to tell you

that you didn't really make that

decision at all? It was already made in

parts of your brain you have no access

to

before you were even aware you wanted to

click.

The only reason it felt like your

decision is because your brain lied to

you, and not for the first time. It

pulls this trick constantly, and it does

so so seamlessly

you'd never even notice. The motivations

you think drive your decisions are

actually just stories your brain invents

to explain actions it's already started

to take. And in this video, I'm going to

prove it to you.

To do so, we're going to see how cutting

a living human brain in half revealed

the presence of a second silent mind

living inside all of us. How your brain

starts preparing to take action up to 7

seconds before you're consciously aware

of it.

>> No!

>> And how your brain's built-in narrator

stitches all of this nonsense together

into the illusion of a single unified

you.

And by the time we're done, you'll be

left wondering who's really in charge

inside your own head, and whether the

entire concept of free will

is merely an illusion.

Fair warning, this is a wild one.

It's September 1944, somewhere in the

skies over the Netherlands.

>> An entire airborne army, British and

American, was dropped into Holland just

ahead of General Montgomery's steadily

advancing British army.

>> A US paratrooper is plummeting towards

the ground.

>> [groaning]

>> As part of Operation Market Garden, one

of the largest airborne operations of

the entire Second World War, he's one of

tens of thousands of men in the sky that

day. He successfully lands behind enemy

lines, but at some point during the

fighting, he's captured

and taken to a POW camp.

Whilst there, he sustains a serious head

injury from the butt of a rifle when

he's beaten by the guards.

The soldier, known to history only as W.

J., would eventually make it home. But

that head injury would stay with him for

the rest of his life. It would also

change everything we thought we knew

about our own minds.

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In the years that followed the war, W.J.

began experiencing severe epileptic

seizures, devastating electrical

misfires in his brain that left him

convulsing and unconscious.

He tried various treatments, but the

seizures continued to worsen. By the

early 1960s,

he was getting desperate.

Desperate enough to sign up for a new

and utterly insane medical treatment.

Epileptic seizures, specifically the

focal variety,

don't affect the brain all at once. Like

an earthquake, they trigger in one

location before spreading outwards like

a wave.

Los Angeles-based neurosurgeons Joseph

Bogen and Philip Vogel believed that if

they could somehow stop the propagation

of that wave,

they might be able to reduce or even

eliminate its effects. But how do you

stop an electrical wave from spreading

through something as complex and

interconnected as the human brain? The

answer can be found here.

The corpus callosum,

a thick bundle of nerve fibers that acts

as the communication bridge between the

brain's two hemispheres.

If your brain was a data center, the

corpus callosum would be the only real

single point of failure.

Bogen and Vogel

wanted to cut it.

The procedure was known as a corpus

callosotomy and it had first been

attempted as far back as the 1940s

with limited success. But Bogen and

Vogel believed these early surgeries had

been incomplete, limiting their effect.

In W.J.'s case, they intended to sever

at the corpus callosum entirely,

splitting his brain clean in two.

You probably don't need me to tell you

this, but cutting your brain in half

is a risky business.

But W.J. was out of options. If he

didn't do something about his seizures,

sooner or later,

they would kill him.

He agreed to the surgery, and in 1962,

he went under the knife, becoming the

first well-documented split-brain

patient in history. Given his status as

a medical guinea pig, nobody was really

sure whether the surgery would work.

>> That pencil-like instrument in his hand

is an electrode. Each time he applies it

to the patient's brain, a weak electric

current stimulates that part of the

brain.

>> Left hand is shaking. Left wrist is

twitching.

>> He's awake through it all. He can tell

the surgeon things that will be helpful

to the surgeon in terms of his brain

mapping. And he has a 50/50 chance to be

entirely normal afterward with no

seizures.

>> But amazingly, the procedure was a near

total success, with both the frequency

and severity of W.J.'s seizures

decreasing significantly.

Even more amazingly, he reported no

negative side effects from having his

brain sliced in half like a piece of

cheese. That might have been the end of

the story, were it not for Caltech

neuroscientist Roger Sperry, who'd been

following the case with interest.

Sperry's research focused on something

called hemispheric lateralization,

the extent to which the brain's two

hemispheres are responsible for

different tasks. In most people, it's

tricky to study because the two halves

of our brains are so closely integrated,

but W.J. was no longer most people. The

two halves of his brain were operating

entirely independently, and that made

him the perfect test subject for

Sperry's research.

Sperry asked graduate student Michael

Gazzaniga to design experiments that

tested each of W.J.'s brain hemispheres

individually.

>> And our duty [snorts] was to

figure out what had happened to these

patients. What kind of phenomenon could

you see? Was one brain knowledgeable

about what was going on in the other?

And all these other kind of spooky

questions. [music]

>> Now, testing half a brain might sound

like a tricky proposition, but thanks to

a quirk in the way our eyes are wired,

it was actually quite straightforward.

As long as your eyes are fixed on a

single point, all the visual information

to the left of that point is routed

exclusively to your right brain

hemisphere, and everything to the right

of it goes exclusively to your left

hemisphere. In a normal brain, that

doesn't matter. The corpus callosum

shares this information between the two

hemispheres near instantaneously.

But, in W.J., that bridge was gone,

which meant Gazzaniga could, for the

first time in history, communicate

directly with just one half of a human

brain.

But, nobody, not even Gazzaniga himself,

had any idea just how mind-blowing the

results would turn out to be.

>> Dr. Gazzaniga now reconstructs the test.

>> Using a device called a tachistoscope,

Gazzaniga would briefly flash an image

on one side of a screen.

>> So, that a split-brain person can be

sitting here, and when we flash on a

picture, say an orange, into the right

visual field, that information is only

projected into the left hemisphere. And

no matter what the stimuli, words,

pictures, uh they describe in a correct

manner.

>> But when the image went to his right

hemisphere, he claimed he'd seen nothing

at all.

>> If a similar visual stimuli are flashed

into the left visual field, which go to

the right hemisphere, the patient will

say, uh "I didn't see anything."

>> That was an intriguing start. There was

nothing wrong with W.J.'s eyesight, so

he should have had no trouble seeing the

images. And [music] yet, the results

were the same every single time.

>> Do you see anything now?

>> You know.

>> Any fingers? Any fingers?

>> No.

>> Show me with your left hand what you

see.

Mimic with your left hand.

Good.

>> Language processing is predominantly a

left brain hemisphere activity. So, was

it possible that W.J.'s right brain

hemisphere

was seeing the images, but it had no

access to the language it needed to name

what it saw?

He ran a second experiment, this time

asking that W.J. simply point at

anything he saw on screen.

>> Such as a fork like you see here, and

sure enough, the patient goes out very

calmly and points to the word fork. What

happens in the split-brain patient is

that all the sensory information that is

projected and and and arrives in the

left hemisphere can be talked about, but

all that information that arrives in the

right hemisphere is perceived and acted

upon, but it is not talked about.

>> His right hemisphere had been seeing

everything all along.

It just had no access to any language.

It was mute. Encouraged by these

startling early results, Gazzaniga

continued to refine his experiments.

>> We have all these kind of abilities that

are separated and spatially represented

in different parts of the brain. These

all have different neural networks,

different systems.

>> In one experiment, Gazzaniga asked W.J.

to recreate a pattern using colored

blocks.

His right hemisphere, working through

his left hand, could do it with ease.

>> As he tries to copy this pattern with

blocks, we discover his ability is

confined to his right half brain.

>> But his left hemisphere, using the right

hand, couldn't manage it even for simple

patterns.

>> When the patient tries to solve the

problem with his right hand, which is

governed from the left hemisphere, we

find that he is not capable of doing it.

Namely, that the right hand, which is

governed from the left hemisphere, is

intrinsically incapable of performing

this kind of visual constructional

tasks.

>> At one point, his right hand was

struggling so badly that his left hand

reached over to try and help it out.

>> You can see the left hand wants to keep

helping the right and and and is

interfering.

>> W.J. had to sit on it to stop it from

interfering with the experiment.

>> Now the question becomes, what happens

when you allow both hands together to

try to solve the problem? And what we

find out is that they fight over each

other. One hand knows how to do it, and

one hand does not, and so they more or

less squabble. And these are almost

mutually independent systems. It was as

if two people were fighting over

performing this task.

>> This kind of intrabody interference,

known as alien hand syndrome,

is relatively common among split-brain

patients. Though the alien hand isn't

always quite as friendly as W.J.'s was.

One patient claimed her alien hand

refused to let her smoke, throwing her

cigarettes away whenever she tried to

put them in her mouth.

And another sufferer woke up in the

middle of the night to find he was being

strangled by his alien hand. Gazzaniga

was fascinated by his work with W.J. He

was watching two separate minds at work

inside one skull in real time.

>> People will ask me something very simple

question. Okay, you've created two

people here. What about their

personalities? And then you ask a

question and say point to a box, yes,

no, I don't know. Are you at Caltech?

The right hemisphere pointed to yes. Are

you on the moon? No. Then I said, are

you a woman? And patient was male. And

he pointed to yes.

And then started chuckling and laughing.

So at least the right hemisphere has a

sense of humor.

Okay. So now comes the big question.

What if you ask, do you believe in God?

The right hemisphere went straight to

yes. Ask the same question to the left

hemisphere, yes, no, I don't know. It

went to no. But here is a human being

whose right hemisphere is an atheist and

left hemisphere on the other hand

believes in God.

>> The implications were staggering. After

all, W.J.'s procedure didn't create

those two minds.

They'd always been there. All the corpus

callosotomy did was allow Gatt and

So does that mean we all have a second

silent mind living inside our heads

without us ever realizing it?

Neuroscientists still aren't sure. But

at the very least, there do appear to be

two centers of agency inside each

standard issue human brain. One you have

conscious access to and one you do not.

It's kind of creepy to think you might

have been sharing your skull with a

silent observer your entire life. One

that, for the record, is considerably

better at puzzles than you are. But

believe it or not, things are about to

get considerably stranger. In the years

after W.J.'s corpus callosotomy, several

other patients underwent the same

treatment, giving Sperry and Gatt and I

a new batch of test [music] subjects.

And it was whilst working with one of

them, known in medical literature as

P.S., that Gatt and I stumbled onto

something

that would change everything we thought

we knew about our own minds

yet again. Using the same tachistoscope

setup as before, Gazzaniga flashed two

different images on screen at the same

time. To P.S.'s left hemisphere, he

showed a chicken claw, and to his right,

a snowy scene.

P.S.'s right hand pointed to a picture

of a chicken, and his left hand to a

snow shovel. That made perfect sense.

>> [music]

>> Each brain hemisphere responding

independently through the hand it

controlled had an image that fit what it

had seen.

>> We said, in this case, Paul,

"Why did you do that?" And he said,

"Well, that's simple. The chicken claw

goes with the chicken." And then looking

down at his left hand, pointing at the

shovel, he says, "And you need a shovel

to clean out the chicken shit."

>> Let's just take a second to appreciate

how batshit insane that answer actually

was.

P.S.'s left brain hemisphere, the one

doing all the talking,

had no knowledge of the snowy scene

whatsoever. But, instead of telling the

truth, the left hemisphere invented a

plausible-sounding reason out of thin

air on the spot.

>> They now have had this bizarre kind of

answer come forth from them, and [music]

their interpreter has to go to work to

pull this thing together to make it seem

sensible.

>> This was something completely new, and

it left Gazzaniga stunned.

>> He picks the red pen, that's left

hemisphere making an easy decision.

>> He tried it with different split-brain

patients, and again, same result. When a

test subject's speaking left brain was

asked to explain behaviors it hadn't

initiated based on information it had no

access to,

>> What do you got there?

>> A banana.

Red.

Okay, I couldn't think of how else she

was going to draw red things, went

wrong, the red pen.

>> It's never said,

"I don't know."

>> Why did you pick banana?

>> It's just easiest to draw with this hand

cuz this hand can pull down and use the

hand.

>> Every single time, without fail,

it made something up. Gazzaniga called

this the left brain interpreter, and

neuroscientists are pretty confident it

isn't a quirk of split-brain patients.

This interpreter is hardwired into every

single one of us.

And there may well be a very good reason

for that.

To understand exactly what it was, we

need to fast-forward to a San Francisco

lab in the 1980s

to look at the work of another

neuroscientist, Benjamin Libet. Libet

wasn't interested in split brains. He

wanted to understand the precise moment

at which conscious decisions are made.

>> First I make up my mind, then my brain

controls my body to do the movement.

Traditionally, we tend to think we make

decisions about movements in this way.

>> To test that, he sat volunteers in front

of a specially designed clock with a dot

that swept around its face once every 2

and 1/2 seconds. He asked them to flick

their wrist at a random time of their

choosing, and to note the position of

the dot at the exact moment they decided

to act.

What this deceptively simple experiment

revealed

seemed to defy all logic. Using an EEG

that measured the brain activity of his

subjects,

Libet detected a signal building in the

motor cortex a full half second before

the volunteers reported deciding to

move.

In other words, it appeared the test

subjects' brains were preparing to move

before they knew they wanted to.

Libet's findings sent shockwaves through

the neuroscience community, but not

everyone was convinced. Half a second is

a fairly narrow margin, especially given

that the moment of conscious decision

was self-reported by the test subjects.

But, in 2008, a follow-up experiment by

neuroscientist John Dylan Haynes blew

that objection out of the water.

Haynes ran basically the same experiment

as Libet,

only with significantly more advanced

tech.

>> We revisited this issue using a new

brain imaging technique that's more

sensitive and can tell you more about

where things in the brain happen.

>> He stuck his test subjects inside a

brain-scanning fMRI machine, giving him

a real-time view of brain activity. In a

slight twist to the Libet methodology,

he gave his volunteers two different

buttons and asked them to press

whichever they wanted at a time of their

choosing.

>> So, we got people to make decisions

between these two alternatives,

and to memorize there was a stream of

consonants presented on a screen. They

might say, "Okay, now I see the letter Z

was up on the screen when I made up my

mind." So, we know when they made up

their mind.

>> But, this time, it didn't really matter

because Haynes was able to see the

decision forming in the brain up to 7

seconds before the test subject reported

deciding to act.

Incredibly, he was also able to predict

which button they were going to press

at a rate of about 60%.

That might not sound like much, but

think about it. If your decisions were

truly made in the conscious moment you

experience them, that number should have

been exactly 50%, no better than a coin.

Right. Okay, so where does all of this

madness leave us?

Michael Gazzaniga's split-brain work

showed us that the brain's left

hemisphere will confidently explain

actions it hasn't even initiated. And

both Libet and Haynes showed us that the

brain is busy preparing our actions long

before we decide to make them. Put these

two findings together, and it's easy to

reach an incredibly unsettling

conclusion. Your conscious mind, the

voice in your head that you call you,

isn't making decisions at all. Your

unconscious mind has already chosen the

path. You're simply walking down it.

Earlier, I said there may be a good

reason the left brain interpreter exists

inside all of us, and this is it. It's

there to make us feel like we're in

control of our own decisions.

>> [music]

>> When in reality,

we probably aren't. In Gazzaniga's

chicken claw experiment, P.S.'s left

brain interpreter smoothly invented a

story to explain why he was pointing to

the snow shovel. So, the patient's doing

this. They're sitting [music] there.

When in reality, he had no idea why.

That's exactly what happens inside all

of us

all of the time. Every decision you

think you've made, every reason you've

given for your own actions,

maybe it's all just the interpreter

doing its job.

Social psychologist Jonathan Haidt put

it best. The conscious mind thinks it's

the Oval Office, the place where

decisions are made.

In reality,

it's the press office. Decisions arrive

from elsewhere, and the press office's

job is to explain them convincingly to

the outside world and to you.

>> You didn't just have a donut?

>> No.

>> Oh.

>> I need one donut.

>> You need one. Oh, what's on your mouth?

>> And if we aren't making conscious

decisions,

that can only mean one thing. Free will

doesn't exist.

Or does it? The truth is, free will is a

seriously complicated topic.

To what extent it does or doesn't exist

is still hotly debated. Between them,

Gazzaniga, Libet, and Haynes

have shown us something genuinely

remarkable about our own minds.

That many of the decisions we think we

make may have already been made for us

by parts of our brains we have no access

to.

>> Well, Mr. Thinwitz gives us really

making progress.

Pretty well along now.

>> Some scientists view that as strong

evidence that free will is an illusion.

A story our brains tell itself so we can

pretend we're in charge.

>> The late Christopher Hitchens, when

asked does he believe in free will,

replied, "I have no choice."

>> But not everyone agrees. And whilst the

evidence is undeniably compelling,

[music] we're yet to have anything that

constitutes definitive proof. Benjamin

Libet believed the conscious mind

possesses a sort of veto power over

subconscious decisions.

>> He says he has two kinds of evidence of

veto power. One kind of evidence is just

that many subjects said, "You know,

sometimes I had urges to flex, and I

just decided not to do it. I decided to

wait for another urge." And then the

other kind of evidence is he did [music]

a veto study. And the instruction was to

prepare to flex, but don't do it.

>> Then there's the question of what kind

of decisions we're talking about in the

first place.

Pressing a button at random in a lab is

about as trivial as human

decision-making gets.

>> I mean, how can I drive on my bike in

Berlin if it would take me 7 seconds to

respond to a taxi

>> see swerving into the bike lane?

>> Obviously, this is not what these

experiments show.

>> You simply can't compare it to quitting

your job or moving abroad. Those kinds

of decisions might require months of

contemplation

and would be near impossible to measure

in an fMRI machine.

>> These brain signals that I mentioned

before are present in experiments where

we make up our mind on our own time

frame.

>> As for me,

I've tied my brain up in knots

researching this video, but ultimately,

I'm reminded of Cypher eating that steak

in The Matrix. If it looks like free

will, and it feels like free will, does

it actually matter that maybe it isn't?

Then again,

I was always going to say that, wasn't

I?

Thanks for watching.