(dramatic music)
Welcome to my brain.
In here, I've got over 300 trillion files,
everything that makes me me.
This section has all the instructions on how I move.
And this is a really important section.
This is where all of my memories are.
There are some,
some old ones.
That's my childhood.
Some nice ones.
That's my boys when they were little.
Down here, I've got some basic but pretty important stuff.
There's breathing, and also,
there's fear.
This whole place comes together to form
both my operating system and my hard drive.
A supercomputer tried to replicate the human brain,
and it took it 43 minutes to recreate
just one second of the action in this place.
While our journey to fully understand
the human brain is in its infancy,
we've made major breakthroughs in discovering
what the brain is capable of.
Over the course of this series,
we're going to show you the astounding things
neuroscientists now know about our brain,
and we'll explore how these discoveries
could improve the way we live our lives
in this modern, busy, stressful world.
(mysterious music)
This is Maria.
Maria's brain has six main jobs to do,
and it's pretty much doing them all the time.
A really important job is keep her alive with some basics,
pumping blood around her body, making her heart beat,
and sending instructions on breathing to her lungs.
Her brain, floating in the dark inside her skull,
needs data from the outside world,
so it collects all the information from her senses,
what she can see, the smells, tastes, and sounds.
Her brain is also responsible for moving her body around.
Maria's brain is in charge of talking
and understanding language.
The brain also makes all of Maria's decisions.
Even though it's 2% of her mass, it uses 20% of her energy,
and when she's doing intense thinking,
it's using half of her energy.
The brain decides on Maria's emotions.
Right now, she feels peaceful.
Emotions, arguably, are what makes us human,
and they play a hugely important role in our lives.
I don't like spiders at all,
so what I'm about to do, to me, is completely horrifying.
Okay, go on.
Ah, Jesus!
Ah, for fuck's sake!
Oh my god!
This is a...
Okay, right now,
my brain is,
is doing some really complex things.
My brain is experiencing an enormous amount of stress.
Inside my brain, there are three main parts.
There's the oldest bit, known as the reptilian brain,
which is concerned with survival,
the mammalian brain, which deals with emotions,
and finally, my clever bit, the cortex.
The clever bit is trying to say that it's okay.
Ah, its little legs!
Its little legs, isn't it lovely?
Yeah, so, my prefrontal cortex is trying to keep me calm
so I can actually talk to you about this.
And I can feel an actual spider, like it's warm little,
creepy little body, just there on my hand.
But the almost overpowering message from the conversation
between the survival instincts of my reptilian brain
and the emotions of my mammalian brain is to run.
Oh, I think it's planning something.
I don't trust it.
I don't think its got...
Its motives are not...
Why is it doing this, why is it doing this?
The emotions from my mammalian brain in this case
are disgust and fear mixed together.
Oy, why am I doing this?
Oh man, oh my god!
There is some evidence that we
have this genetic fear of spiders,
and then my brain is also accessing
all of the memories that I have of spiders.
So, why am I so scared of spiders?
Fear is one of my emotions,
and emotions are incredibly complex things.
How could we ever hope to understand them?
(baby laughing)
This is Baby X, and she's helping scientists
unravel the mysteries of how our brains work.
She's one of the most advanced
brain simulations in the world,
and she's enjoying playing a peekaboo game with me.
Over the course of this series,
Baby X is going to help us see how our brains
shape and influence every aspect of our lives.
Now at first glance,
she may like just a very clever animation,
like you would see in a movie or a video game,
but Baby X is so much more than that.
In a movie or a video game, we watch the animation.
Baby X watches us.
Over here, hey, baby, that's it.
Peekaboo! (baby laughing)
What's happening here is that Baby X is responding
very much like a real baby would.
Boo! (baby laughing)
She gets a fun surprise, and that manifests as joy.
But where did she come from,
and how is she going to help us
figure out the mysteries of the brain?
Baby X is literally the brainchild
of computer scientist and two-time Oscar winner, Mark Sagar.
Together with his team of neuroscientists, psychologists,
engineers, and programmers, they've built Baby X.
Mark, how did you come to build something
as complicated as Baby X?
Well, I was always interested in the brain and the mind,
and I was also interested in human simulation,
and interested in human behavior in general.
So, I was thinking how I can put together
all these things that I've been interested in.
But the reason to make it a baby,
I just happened to have a real baby lying around.
My daughter, at that time, that it was modeled on,
was about three months.
Then I thought, okay, I'll try to scan the baby,
so I built a scanner at home when she was asleep,
and then started creating the first geometry
to then start putting the first brain models in.
The strange thing is that we're sitting here talking now,
and Baby X is over there,
and she's listening and watching us as well.
That's right, yeah, you can call here.
Hey, over here!
(baby laughing)
So, what is Baby X?
It's a virtual infant simulation.
What we're trying to do is build a LEGO-like system
which can encapsulate models of,
neuroscience models, models of human behavior,
models of social interaction, and learning.
It's trying to create the elements which put together
aspects of what makes something lifelike.
The only way to do that is to give it a brain
and sensory systems, and so forth.
That was the next step in what to do in simulating,
doing human simulation.
To understand the absolutely awesome power of the brain
and its remarkable ability to adapt to any situation,
we can look to an Australian teenager.
Karley Miller was having seizures daily, and they were bad.
How bad did it get when you were growing up?
It got pretty bad,
to the point where I had 9 1/2-hour seizure.
I was put in a coma three times to sustain my life.
When she was 15,
a neurosurgeon came up with an incredible idea
to remove half of her brain.
In that moment, it was just Mum and I,
and we looked at each, we were pretty shocked,
and we were just like, "What?"
The surgeon's words were,
"Karley, with simple surgery, I can cure you,"
and Mum and I were speechless.
We just looked at each other, we're like, "Simple surgery?"
It sounded like complicated surgery,
but I wasn't gonna live my life
knowing that one of my seizures were going to kill me,
so I decided to take a leap of faith,
entrust my life in the hands of a neurosurgeon.
Nobody could be certain what would happen
if they took out half of Karley's brain.
It was possible she could die.
When I got back down to ICU,
you're all wired up and lying there, still quite lifeless.
You hadn't spoke, so we were all thinking,
can you understand, do you know what's going on?
I was telling you about the dryers at Ronald McDonald House.
And when I started telling you about the dryers,
and that it wouldn't work, and this, that, and the other,
all of a sudden you opened your eyes, and you just said,
"Did you push the start button, Mum?"
I remember that clearly. -: Do you remember that?
I remember that clearly.
Yeah, I'll never forget it,
because then I stood there, and I think,
if you remember rightly, I was crying.
You were howling. -: Howling.
Like, that really ugly cry.
Karley survived because of the brain's plasticity,
its ability to change.
I mean, in Karley's case,
she's literally had half of her brain removed,
so most people would think that she would lose some memory,
that she would lose some movement, but she hasn't.
Why is that?
Well, if they came to me, and took out half of my,
or one of my hemisphere, cortical hemispheres,
that's exactly what would happen.
There would be immense impairments.
But the fact that this disorder has been going on
for quite a long time, through childhood,
when the brain is particularly plastic,
and particularly able to learn new information,
then actually, the memories haven't been stored
in that damaged hemisphere,
and that's evident because they're still there
when that hemisphere has been removed.
In a way, it sounds incredible.
Actually, it is incredible.
But whatever the normal brain tissue is, and wherever it is,
it can take over functions,
particularly if it's happening early in life.
Half of Karley's brain was damaged from birth,
and because of the plastic nature of the brain,
it wired all the functions it needed into the good side.
When the surgeon removed the misfiring side,
all that was lost was the constant seizures.
I'm living proof that you can live with half a brain.
Karley illustrates the power
and the ability of the brain to change and adapt.
But if the brain's trapped inside our skull,
floating in fluid,
what do our senses do to lend a helping hand?
(whimsical music)
This is Kevin.
He's a tuatara, and they've been around since the dinosaurs,
so clearly their small brains have served them quite well.
What's interesting is that the oldest part
of the human brain is also known as the reptilian brain,
and that's because it does pretty much
the same stuff as Kevin's brain.
It's responsible for hunger, breathing, and fear,
the stuff that keeps us alive.
But we've got a lot more inside our skulls than Kevin here.
We've got the mammalian parts of our brain,
which are responsible for feelings and emotions,
and the cortex, which does our thinking.
So, Kevin here is never going to feel
sadness or embarrassment.
But experts reckon that humans
have something like 34,000 different emotions.
So, what's the point of them?
(upbeat music)
Emotions are clearly expressed on our faces,
and they're universal.
There are seven major emotions.
(balloons popping)
We need emotions to survive.
Emotions act as signposts to tell us what's important.
If we think about the world, there are a million things
I could be paying attention to at any time.
Emotions tell me which are the ones that are most useful
or most valuable to pay attention to.
Emotions help me store the memories
that are going to be most important
for my future decision-making or survival.
Baby X isn't an animation, she's a virtual human,
and all of the behaviors are generated by neural networks.
And she can actually help us see emotions.
She watches and listens to what I do,
and makes her own decisions in realtime
about how to respond.
And because I've been talking to you and not to her,
she's starting to get upset,
and so, just like a real baby, I have to calm her down.
(baby crying)
That's it, it's all fine.
That's it.
Little smile.
There you go, good girl. (baby laughing)
Baby X is driven by a virtual nervous system.
It controls her breathing rate, her heartbeat,
her facial expressions,
and we could even see her facial nerves.
Deeper still is the virtual brain which drives it all.
Her brain triggers the production of cortisol
because she's upset and stressed.
Baby X is the result of combining neuroscience research
from all around the world,
and shows how sophisticated
our knowledge of the human brain has become.
(upbeat music)
We used to think our brains worked a bit like this.
Imagine this building represents my brain.
If I see a spider,
then the spider parts of my brain light up,
and if I see Jennifer Aniston,
then the Jennifer Aniston bits of my brain light up.
And it is a little bit like that,
because certain areas of our brain
do seem to be responsible for particular functions.
This bit does smell,
and this bit does taste,
but it's way more complicated than that.
Your brain has 86 billion neurons,
and each neuron has 10,000 connections to other neurons,
which means you have something like
100 trillion connections.
And that means that that best analogy for the brain
is actually the universe.
There are more connections in your brain
than there are galaxies in the known universe
and stars in the Milky Way.
I'm going to meet Distinguished Professor Sir Richard Faull.
He's been studying the brain for over four decades,
and is considered an international expert in the field.
We know a lot, and yet we know very little.
There is so much new to find out
about how the brain enables us to read, to write,
so see a picture, to store a memory,
to create an idea, to have love, and all the rest of it.
We are so primitive in that understanding.
I say that if you're a neuroscientist,
you're going to have a job for life.
But one thing that has profoundly advanced
our understanding of the brain is the MRI machine.
Morning, Nigel, Anna. -: Morning.
Hi, Anna.
Just do a final check before we bring you in the room.
Definitely not a pacemaker?
Nope. -: No injury to your eye
with metal fragments? Nope.
The MRI machine uses powerful magnets and radio waves
to produce a detailed scan of the brain.
Neuroscientists use this to look inside the human brain.
I'm going to see where my memories are kept.
(motor whirring)
The MRI was invented 40 years ago,
and is now one of the most important tools in neuroscience.
Previously, we could only look at the brains
of people who died or people that experienced
traumatic brain injuries or illnesses.
Hey, Nigel, can you hear me okay?
We're about to do the motor task, okay?
So, when you see a fixation cross, do nothing,
but when you see a zero or a circle,
you can tap your right hand.
Now we can look inside healthy functioning brains
and watch what happens in realtime
as it performs different tasks.
When you see a picture of yourself,
generate a very specific memory from your past.
The MRI machine shows my brain
responding to photos from my past.
You can actually see my hippocampus lighting up,
a structure deep in the brain associated with memory.
Memories are one of the important sources of data
your brain uses to help you react
to things happening around you.
We use things that happened to us in the past
to try and predict what's about to happen,
but those memories can only do half the job.
The only way that our brains can learn
about the outside world are through our senses,
sound, sight, smell, touch, and taste,
and then it has to filter all of that information
through our memories to try and figure out
what's going on and and what it should do next.
Right now, my brain is getting a whole lot
of tiger-related sensory information.
(tiger roaring)
But it's also getting a whole bunch
of fence-related sensory information,
and it's combining all of that to tell me that really,
I've got nothing to worry about.
So, how does our brain utilize all of that information
that's coming in from our senses?
Our senses literally tell the brain what's out there.
But what happens when they find things in the world
that our brain has never encountered?
We know from our memory that milk is white.
Given we use our senses to verify things in the real world,
what happens if we offer people gray milk?
So, this is our little drink.
What are your initial thoughts about that?
Looks a bit funny.
Would you like to taste that?
It doesn't look very appetizing.
Why is it gray?
It's a little gray.
Ah, well, a gray-green is not an appealing color.
Our senses send information to the brain
which figures out something's not right here.
Perhaps this gray liquid is poisonous.
Could you have some first?
After we see the gray milk,
our brain asks for more data, for the nose to smell it,
or for the braver ones, to use taste.
This new information is then returned
to the brain for evaluation.
It's milk.
What?
Our sense of taste sends massive amounts
of data to the brain, stuff we're not even aware of.
This miso is salty,
and that gives my brain important information
about the level of electrolytes, minerals, and water.
The rice tastes slightly sweet,
and that's all about carbohydrates.
The tofu tastes of umami, and that tells my brain
that there's some protein on the way.
The green tea is bitter, and the soy sauce is sour,
and back in the day that would've been a warning,
because lots of poisonous plants
are either bitter or sometimes sour,
and that's why you throw up
if you have stuff that's too bitter.
Like all of our senses,
taste sends information to the brain
so it can work on its most important job,
keeping us safe from harm.
All right, Marie, I'm gonna do a very simple thing.
I'm just going to use these two brushes.
I'm just going to brush your finger, like so,
and all I want you to do is just pay attention
to the feeling of the brush against your finger,
and just keep watching the brush.
And this strange experiment shows
how our brain relies on our senses.
It's a pretty strange sensation, isn't it?
Oh, it's getting weird not, yeah.
We have created a scenario
that our participants' brains have never come across.
The brain works hard to figure out what's going on.
One of the senses it's using is proprioception.
This is the same sense that allows you
to touch your nose with your eyes closed.
The brain is being sent mixed messages.
It can see a hand being stroked,
and it feels the hand being stroked,
but it mixes the two message,
and comes up with a faulty result.
I'm feeling a bit of an affinity with this hand, actually.
Our brain is convinced that the fake hand in front of us
is our actual hand.
(both laughing)
Floating in the dark inside your skull,
your brain is worried for a second.
Is that weird?
Yeah.
Was there an amount of alarm when I do that?
But then new data arrives from senses.
There was no pain.
And the brain uses memory to explain the lack of pain,
recalling the circumstances of the fake hand.
Your brain has instantly built a new
and accurate picture of the world,
one that will hopefully keep you safe.
But our newborn brain starts off
without any of these skills.
How does it actually develop?
How does our brain develop?
We know we're born with our full set of neurons, 86 billion,
but our brain gets four times bigger over our life.
And why is that?
Well, it's because of the increasing connections
between the neurons, called synapses,
which make the brain bigger.
Children under the age of three
make 7,000 new synapses a second,
so what happens to them all?
How come it doesn't all end up a great tangled mess?
Strangely, our brains work much the same way
as this field of tangled weed.
So, if this was a baby's brain,
and it wanted to move its hand,
it will have to get that thought from this part of its brain
all the way over to the motor part of its brain,
way over there, and it does that
through a combination of wearing in a new path
and pruning the synapses that it doesn't need.
(dramatic music)
Now, at first, it's slow and hard-going,
because there isn't a clear path,
and there's a lot of tangled stuff to fight through.
When we learn to do a new thing,
our brain has to make a new path and clear old synapses.
But as the messages go backwards and forwards,
something interesting starts to happen.
It gets easier and easier for the message
to travel between these two parts of the brain,
because they effectively create a path.
The connections between each cell
in the pathway are strengthened,
and the message can travel faster and easier.
The baby is learning a new skill.
Essentially, cells that fire together, wire together,
and the connections we don't need
are simply pruned and disappear,
which is why it's so important for babies
to interact with their caregivers and with the world.
That process of wiring in useful parts
and pruning the synapses they don't need
is crucial to their development.
But what happens to a developing brain
if instead of being nurtured it's neglected?
There's a very famous psychological experiment
called the still-face experiment,
and it shows in a simple but quite striking way
what happens if you stop interacting with a baby
even for a few seconds.
There we are, happy baby, that's it, nice and smiley.
Smiley, smiley, it's all good, there we are.
And now I let my face go completely still.
Baby X shows us how a lack of interaction can make us feel.
There you are, it's fine, happy, happy.
Smiling again, it's all good, happy baby.
There we are, a little smiley face.
There we are.
Now, obviously it's not gonna harm a baby
if you stop interacting for a few seconds,
but what happens if you neglect a baby for years?
So, if children have an attentive and interactive caregiver,
then those social circuits are constantly reinforced,
but if they're neglected for long periods of time,
then they effectively become
desensitized to social interaction,
and it's like they're a flat battery.
I'm going to simulate the effect
of years of neglect on Baby X's brain,
something we wouldn't want to do in the real world.
That's it, there we go.
Baby X no longer reacts to me.
The impact of neglect is complex,
and can affect areas responsible for memory,
self-control, and emotions.
Our brains change the most
in the first three years of our lives,
but the next major change happens around puberty,
and insurance companies recognized this
before neuroscience got there.
They saw that the evidence showed teens took more risks.
Do you ever make risky decisions, do you ever take risks?
It really just depends on the situation.
Usually, I like to play it safe.
I like to make sure that, like,
it's not gonna result in a bad consequence.
When you do take a risk,
does it make you feel good or bad?
I mean, in the moment, it does make me feel good,
and I do get that rush of adrenaline,
but if it's something that I wasn't 100% wanting to do,
then I'll overthink it,
and I won't feel that good afterwards.
The brain is fully developed,
but there's an intense period of pruning and strengthening.
In evolutionary terms,
getting the adolescent ready to set out on her own.
What we previously thought was that the teen's
decision-making part their brain wasn't properly formed,
so they weren't able to properly evaluate risk,
but it turns out that's wrong.
The latest evidence tells a different story.
Teens understand risk as well as adults,
but they do take more risks, so why?
Well, one theory is their nucleus accumbens,
their pleasure center, is the biggest it's ever going to be.
They do not what they're doing.
It's just that everything feels so good.
They get waves of dopamine after an ice cream,
sex, drinking with friends.
Their pleasure center is excited
when they take risks with friends.
They're awarding each other for trying new grownup things,
practicing for leaving the nest.
But when they're driving with their parents,
their pleasure center lights up when they follow the rules
because their parents are please with them
when they slow down for the orange light.
The brain has finished most of its development by age 25,
and everything is working at full speed.
But how exactly does it work?
How do we do something as simple as recognizing someone?
Ah, it's my daughter!
It's pretty tiring being your brain.
Your brain is only 2% of your body weight,
but it consumes 20% of your energy, which is a lot,
so it's always looking for shortcuts.
Now, most of the time we don't even notice these,
but occasionally we get to peek behind the curtains
to see what's really going on.
This square has some black dots,
but at a glance you can probably only see a few of them.
Your brain doesn't bother to draw them,
and saves energy by assuming a pattern.
But you can see all 12 when I point them out.
One, two, three, four, five, six,
seven, eight, nine, 10, 11, 12.
Our brains are always looking for patterns to save energy.
And a recent discovery suggests that energy-saving drive
applies to recognizing faces, too.
Our phones can recognize faces, even gorilla faces,
using some facial recognition code called an algorithm.
But could our brains work in exactly the same way
as our phones?
Recently, scientists showed monkeys this picture of a face,
and then they measured the activity in neurons
in the facial recognition part of the monkeys' brains.
The neuroscientists created photos
using just the signals from those neurons,
and incredibly, they were almost identical to the face
the monkey was looking at.
The scientists were literally mind-reading.
And when you really think about that, it is astounding.
What this seems to show is that just like our phones,
our brains use a facial recognition algorithm.
And it also seems to show that we use
just 200 of our 100 billion neurons
to recognize and recreate any face in the world.
A key feature of the human visual system
is that it's not a single general-purpose machine
that handles all kind of visual information,
but rather, it's a collection of many, many little systems,
subsystems, we call it,
and each of these subsystems is specialized
for handling a particular part of the visual world.
For a long time we knew
that there's a subsystem for processing motion.
Another one is for processing color.
More recently we've learned that there's subsystem
for recognizing special kinds of objects.
Professor Doris Tsau, an American scientist,
made this breakthrough.
There's about 200 neurons that she studies.
These neurons, they're like a concert,
so they sing a song together,
and by singing a particular song,
they can basically create an image
of any face you can imagine by combining,
mixing, and matching the right facial features.
That's study's a big deal,
because it's the first one that gives us
a pretty precise description
of how faces are actually encoded in the brain.
Taylor?
But what happens if that algorithm doesn't work?
Social Studies, she sits there.
Tenakwe, Gabi.
Teacher Joe Tapper suffers from prosopagnosia.
Joe, what's your understanding of prosopagnosia?
I can't even say it.
We just call it face blindness.
Face blindness, prosopagnosia?
Face blindness.
Basically, the part of the brain that's responsible
for face recognition doesn't work.
In class, when you've got lots of kids,
and they're all wearing the same clothes,
how do you recognize students in your class?
(laughs) I don't, I really don't, I fake it.
I notice who's got earrings.
I look at people's ears, the earlobes.
I get you mixed up with Georgia, but you're Elizabeth.
And I know it's you, Jade, 'cause you're wearing jade,
and I looked at your bag before.
Literally, it's just that central human face,
that's the bit that doesn't stick?
Yeah, making sense of the human face.
There's something in the processing
that just doesn't happen as it should do,
and it's such a tiny, fine, delicate thing.
So, if we were to pass in the supermarket tomorrow,
does that mean that you wouldn't recognize me?
Well, Nigel, I have to be honest,
you have some distinctive ears.
They're beautifully formed.
Camera crew are just having quiet hysterics there.
(crew laughing)
When you see your own reflection,
do you recognize your own face?
I don't always recognize myself.
And I remember, back in the '80s, I got a perm,
a spiral perm, and I kept looking, every shop window.
I just had to keep looking.
I mean, I wondered, too, sometimes
if this is why I've got long hair,
because it's really distinctive, you know,
'cause that's me, that's the hair.
That's something that's really strong for me,
your hair, your ears, your jewelry.
The things around the face, I recognize.
Do you have a problem recognizing objects or pets?
No, no, so it's something about the human face.
There must be something really special in our brains,
the way that we identify human faces.
If the facial recognition study
done with monkeys is correct,
then perhaps Joe's facial recognition algorithm
has some errors somewhere
in those 200 highly-specialized neurons.
One description that is used
by some people with prosopagnosia
is that it's like looking at a face upside down.
So, you know that it's a face.
You have access to all the same information
as when the face is right-side up,
but it's really hard to recognize who owns the face.
All right, Chris, I'm gonna show you
some photographs of people,
and you have to tell me if you know who they are.
No.
Nope.
Oh, Hillary Barry.
No.
Tony Street.
No.
Ah, (chuckles) you.
Ah, that's Gina, (laughs) my niece.
No.
Sure?
Yup.
Oh, it's my daughter!
So, it's kinda like your brain has a map of faces,
but a basis that, on the very reasonable assumption,
that the face is right-way up.
And so, when it encounters the upside-down face,
it applies the same map, and it does, flick, flick, flick,
"I don't recognize any of these people."
Yeah, correct.
But as soon as you do that, it goes, "Ah, yeah," clunk,
"I know exactly who that is."
So, we know how our brain develops,
the purpose of emotions, what our senses do,
but is there a bit in the brain that makes you you?
The first question in figuring out
what makes you you is a big one.
Are the brains of males and females different?
A very popular book from the '90s
reckon that men are from Mars and women are from Venus.
The theory is that men and women's brains
are very different, and if you walk into a toy store,
you can find evidence which seems to support that theory.
This is the boys' aisle of toys,
which is mainly cars and trucks and Nerf guns and war toys.
And this is the aisle for girls.
It's all pink and fluffy stuff and dolls.
Not a single gun or truck in sight.
Does neuroscience back this up?
Are boys' and girls' brains different?
It actually turns out that when you look
at younger children up to the age of about three,
and you put them in a lab setting,
have a range of boy toys and girl toys
and gender-neutral toys all around,
you actually find that there's a huge amount of overlap
in that age of what kind of toys kids will play with.
You'll often get boys playing with girl toys,
girls playing with boy toys.
Dr. Cordelia Fine is one of the world's
foremost experts on gender and the brain.
There would be some people who would say
boys are born with a tendency to be dominant,
risk-taking, competitive;
girls are born with a tendency to be more nurturant,
and to care more about their appearance.
And all that we're doing in gendered toy marketing
is really just sort of enhancing
or developing those initial predispositions.
There'd be other people,
and I include myself in this, who'll say, look,
the scientific data is really quite unclear on that point.
There are lots of reasons to think that that isn't the case.
There is one definitely difference
between male and female brains.
The male brain on average is larger, so what does that mean?
We know we have 20 grams of brain
per kilogram of body mass, generally speaking.
Differences in body weight, of muscle mass and bone mass,
are reflected in differences of whole-brain size.
Brain size does not equal intellectual capacity.
So, if you look at a brain,
you can't tell whether it's a male brain
or female from the outside.
You can't tell whether it's an intelligent person
who is a atomic physicist,
or whether the person was a carpenter,
or a netball player, or whatever.
You cannot tell that.
We're still very early on in our journey
of understanding how properties of the brain
translate into behavior, or how we think, how we feel,
so we have to be extremely careful
not to just project gender stereotypes
onto those ambiguous findings.
It's generally agreed that trying to separate
whether nature or nurture makes boys boys and girls girls
is as pointless as arguing whether a cake
is made out of flour or sugar.
So, what is it that makes you you?
If I could only answer this question,
I would be getting the Nobel Prize, I'm sure.
It's so complicated, but so incredibly fantastic,
that each person is a different personality,
every single person on Earth.
There's some people more similar to others,
but there is a total diversity,
and that is what's one of the most unique things,
I think, about human life.
Personality is an incredibly complicated thing.
We know that it's made inside our brains,
but how, and where?
In reality, there is no personality section of your brain.
It's probably more accurate to think of it
as different parts of your brain which all contribute
to the final product we think of as personality.
One way to think about this incredibly complex sequence
of interactions inside our brain
is in terms of of sensitivities.
So, for example, if you are an introvert,
then you're more sensitive to the negative effects
of being around people,
and if you're an extrovert,
you're more sensitive to the positive effects.
So, what'll happen if I take Baby X
and make her overly-sensitive to surprises?
What if I make her really afraid
of sudden and unexpected events?
(Nigel barks)
If Baby X's personality was like this.
There you are, it's fine, happy, happy.
Highly sensitive to sudden and unexpected events,
she might look for more certainty
and less risk throughout her life.
But what happens if I make her less sensitive to this?
(Nigel barks)
How much of our personality is shaped by our genes,
and how much of it is about the things
which happen to us along the way?
Ashleigh, Olivia, and Kimberly are identical triplets,
and so, if personality came just from our genes,
we'd expect these three to be all the same.
Hello, what's your name?
My name's Ashleigh Parkinson.
Hello, could you tell me what your name is?
(upbeat music)
Sure, Olivia Parkinson.
What's your name?
My name is Kimberly Princess Parkinson.
Whoa, that is a way cool name, eh?
♪ Do doo do doo do ♪
When they were young,
their parents saw minor differences in their personalities,
but as they grew,
they became more and more different from each other.
We had the same friend groups growing up,
and then, when we got to intermediate
was when we really took our own pathways.
We found out our interests. But even still,
we were quite similar. Yeah.
(people cheering)
You know, my sister got in with the nerd herd,
and then, the other sister got in with the sporto crew,
and then, I got in with my little other crew.
Kim would do, her friends were sporty, too,
but they'd do a bit more partying and stuff as well as it.
A lot of the stuff that I got into
was because of my friends.
I wasn't just saying randomly one day,
"Ah, I really need to start partying."
Some of the girls would be like,
"All right, let's drink when my parents are away,"
and I was like, "Ah, that's badarse, let's do that."
How are you different to your sisters now?
How we spend our time, and what we value in life,
what actually fulfills us.
Olivia gets up at 5:00, and sometimes I will come at 5:00.
That's kinda like the difference, I suppose.
Olivia is a dedicated Hare Krishna.
Yeah, Ashleigh is the more sporty one. (chuckles)
I'm more gentle, caring.
Kimberly is more, I don't wanna say more materialistic,
'cause it sounds like I'm begging,
but you you know what I mean, like,
put your own success in your job and career
and social circles.
Yeah, I don't take life as seriously, I don't think.
Kinda like two different ends of the spectrum, right,
Kim and Liv, and then I'm kind of just in the middle.
At its most simplistic level,
personality is simply patterns of behavior we repeat.
For example, Olivia regularly goes to Hare Krishna meetings.
So, her personality would include the description spiritual.
And we now know our personality is the result
of the interaction between nature and nurture.
Does everything that happens make us how we are?
To some degree, yes.
So, some things are gonna be more important than others.
Some things are entirely trivial,
and won't matter at all in determining who you are,
but other things are very important
in determining who you are,
to the extent that I would not be the same person that I am
if, for example, we didn't emigrate to New Zealand.
That's a big factor in determining
the kind of person that I've become.
Those kinds of big events,
or kind of important factors in one's life,
have a strong impact on the kind of person that you become.
The triplets may have begun their lives
with the same genes,
but over the course of their lives,
they've created their own identities.
Their brains, like all of ours, may look the same,
but they've each forged their own individual pathways
through all those trillions of synapses
as a result of the lives that they've lived.
And you have also created your own unique brain.
Those trillions of pathways you carve
through your plastic brain every single day of your life,
well, that's what makes you you.
(mysterious music)