Original subtitles

Ok. Let me see!

Come on, we'll go for a walk.

Tiki-tiki-tiki-tiki.

Oh, woo-hoo!

Hey.

As adults, we take walking for granted,

this incredibly weird and unique form of locomotion

that we find ourselves doing all the time.

But if you really sit and think about it,

there's a lot going on.

An incredible amount of things have had to come together

for humans to be able to do this.

How do you expect a tiny little body to stand up

and master that?

It's the most important moment of motor development

during the first year of life.

It's a particularly beautiful moment,

for the first time the baby takes...

these first steps with confidence.

One of the main things that we're interested in looking at is

not just when do kids walk...

but what happens to their world when they walk?

This is a really difficult question because...

really, walking changes every part of the babies' lives,

and so where do we even begin to untangle that whole mess of threads?

Oh, you are such a globe trotter!

I think they are very close to walking, both of them.

Eloisa pretty much is standing up all the time.

The only thing she doesn't do is just go ahead and walk.

It looks like she's more ready than him

because she is more stable.

Hello!

It's always funny to watch Augusto when he's jumping.

He just goes really quickly everywhere, and he looks so happy doing it

that it makes you laugh every time.

Didn't you get cared enough?

When you look at him,

I think, "Oh, he's a bit slow, he's not learning as quick as his sister."

But then he's very clever.

He can see there's more than one way to do it.

And one is more difficult for him,

so he's clever enough to choose the easy way

and just get on with whatever he wants to do.

Augusto was so far away from her

that I think Eloisa was kind of waiting,

and one Tuesday she just did her first steps.

It was a memorable moment.

Very Good

You did it!

I've always loved science

and how science helps you understand

what's around you.

Growing up I was fascinated by the laws of nature

and how humans and animals move.

I studied physics and then I turned to neurophysiology,

and I fell in love with studying how babies learn to walk.

When a baby is born

there's a movement

that anticipates and resembles walking.

We call it "newborn stepping."

So when I had my own babies it was

the first thing I tested and tried.

You support about 70% of the baby's weight

and you put its feet on a flat surface.

The baby moves its legs alternately,

one leg slowly in front of the other.

This is one of the reflexes it has. It's very mysterious,

because we don't know the origins of this reflex.

In 2010,

with colleagues at the Foundation Santa Lucia in Rome,

we wanted to investigate if babies are born

with an innate ability to walk.

We wanted to know, was newborn stepping the foundation

for when the baby walks on its own,

or was it just a strange behavior that disappears after birth

and independent walking is an entirely new kind of movement?

Our theory was that newborn stepping and the baby's first steps were connected.

- Hi, hello. - Hi.

- Thank you for coming, - Yes, you're welcome.

And who we got here today?

This is Benjamin,

and now he's three weeks old.

Oh, wow!

I will just explain a little bit

what will happen during the experiment.

So we will put really, like, small sensors

to record the muscular activity.

Okay.

Everything is safe,

and everything is properly done for babies.

Ready to work.

Yes?

That's... He can stay here.

We did this study in collaboration

with the Neonatal Department at the Sant'Eugenio Hospital, Rome...

where there were babies

who were two, three days old.

Oh, yeah.

We wanted to look at the muscular activity

used in newborn stepping

and see how it compared to the muscular activity

in independent walking.

Ready?

Okay.

We can start.

Number one.

So we needed small sensors

to capture the muscles electrical activity

of different muscles in the baby.

We also applied sensors

to see how the baby was moving.

Nobody had studied newborn walking like this before.

- Okay? - Yes.

Yes!

Oh, I do remember when they are so young.

Yes.

What we're gonna do now is we start the treadmill,

and we start to walk.

Okay.

Wow.

Yeah.

So, we go.

Walking.

That's right.

Yeah.

Where is your mommy?

- Where is your mommy? - I'm here.

Yeah! Mommy.

It was challenging research...

...but beautiful.

In the end we managed to record 46 babies.

Previously, technology wasn't advanced enough to perform such an experiment.

But we tried and we succeeded,

I'm happy to say.

Hey.

Now we have to test our theory

and collect more data on toddlers.

I want to compare them and see the relationship

in their stages of walking

and see if there was any connection

between newborn stepping and independent walking.

You like that.

That's Mummy's phone. Just ignore it.

He's absolutely shifting his weight

from the left leg to the right leg,

and he's trying to use his feet to get to his toy.

Good boy, keep coming.

Ah!

Nelson, come.

Come, Nelson. Come. Come.

Yeah, come.

Come. All right.

Do you want to let go, and you can walk to Mummy?

Do you want to do that?

Do you want to walk to me? Come on then. Come.

That's my boy. There you go, little Nelson.

Come on.

Nelson is a good boy.

He's walking now.

He's a big boy.

Yes. Yeah.

You've done such a great job, my son!

Well done, you. Well done, Nelson.

Good job!

Today he walked all the way from the sitting room,

and all the way up to here, babe.

Wow.

Without grabbing onto anything.

Proper little chap.

- Like proper walking. - Proper little chap!

I just can't get over... Look at this. I just can't get over it.

He's like a little Speedy Gonzales. Look at that.

That is just amazing.

He's gone from a few really tentative steps

to, like, just going nuts.

I hadn't quite grasped how terrifying this would be.

Boop!

Okay, select one of the baby children.

So different from the others.

You're so big.

- Yes. - A big boy.

We wanted to compare the muscular activity of newborn babies

with that of toddlers who could walk independently.

We tested ten toddlers in total.

Who is this?

Oh!

Well done.

After the recordings of all these newborns and toddlers,

we started analyzing the data.

Newborn stepping is very simple.

Only two patterns of muscle activation are needed

to deliver the entire muscle movement used in newborn stepping.

These patterns are connected to supporting weight

when the baby is in contact with the floor,

and the other is related to the movement of swinging.

When the toddler starts walking,

they keep these basic patterns that are present in newborns,

and this was surprising.

It's not completely different, it's not something created from scratch,

they keep these building blocks that the baby uses

to start walking independently.

The fantastic thing about these results

was the confirmation of our initial hypothesis,

that the baby is born with an innate walking skill.

What was surprising

was that we found the same muscular activity of these basic movements

but there were two additional patterns

which are needed for when the baby starts to walk on its own for the first time.

These two new patterns are...

The first is related to the moment of touchdown,

this phase in which the baby touches the floor for the first time.

And the second, during the phase of push-off,

the release and propulsion during the walking phase.

This way they can control the muscular force they used to walk,

and the speed of movement,

and exactly when and where they put the foot down.

This research received a lot of interest,

and this is fantastic because you think newborns aren't able to do anything,

but it's not like that.

This ability is already there

when they're born.

Oh, good boy!

Good boy.

You want to stand up? Stamp, stamp, stamp.

Stamp, stamp, stamp.

- Irish jig dancing? - Yeah.

At some point, all babies will start walking.

Ah!

It's important for parents to know that they can

possibly stimulate this stepping in newborns.

Sumo boy.

Our little man.

A baby needs to grow

and develop both its brain and physical strength

before it can walk alone.

That's it. Go on.

But the more you can encourage your baby to move and use its muscles,

the more you will support their physical development.

Good girl.

Oh!

Augusto doesn't seem too interested in walking yet.

Because he's a twin, I can obviously compare him all the time with Eloisa,

and I can see he's a late developer.

At the beginning I was really worried.

Um, when he was born,

I immediately noticed he had a weak side.

Eloisa was two kilos and 700 grams,

and Augusto was a little bit under two.

He was really tiny, so he had to stay in the incubator for ten days.

It felt really scary.

We had him checked, seen by a, um,

special pediatric development specialist,

and they gave us a lot of reassurance that he's fine,

he doesn't have any problem.

He's just lower in the development.

My area of particular interest is how exercise,

um, and physical activity

ends up reflected in skeletal remains.

I come from a long line of people who like to pick up very heavy objects

and put them down again.

In my spare time, I am a powerlifter and a CrossFit instructor.

My grandfather was a bodybuilder

and a gymnast.

He was one of the only people

to ever do a gymnastics routine on top of the Empire State Building.

One of the ideas that's fascinated me my whole life

is not only how exercise shapes and grows your muscles,

but the fact that it can also shape and grow your skeleton as well.

If you do a lot of activity, your body is gonna lay down more bone.

If you're a couch potato, it's gonna take away bone.

Infants were my big interest when I was in graduate school.

What I was really interested in knowing was,

how does the young human skeleton respond to the challenges

of standing upright and taking your first steps?

Hi. Do you want to come? Do you want to come to Mommy?

By the way, he can pick himself up now.

Like, if he fell on the floor, or if he sat down,

he can go from sitting position to standing position to walking.

In my field, people have always thought

that there was some sort of line in the sand

where, after a particular age, the activity that you did

was affecting your body, but before that, it wasn't.

We tended to ignore how activity affects the bones of very young children,

of infants and toddlers.

I realized that there was this huge, gaping hole, this deficit,

in our knowledge.

So in 2006, I visited about 15 different museums

throughout Europe and Africa and the United States and the Middle East,

essentially carrying about 130 pounds of scientific equipment

on my back,

to look at infant bones.

I was really interested in exploring developmental changes,

uh, but across a broad, uh, range of time and space.

Um, so I was looking at individuals as recent as the 20th century,

but also dating all the way back to 250,000 years ago

across multiple countries and continents.

One of the things about

working with the remains of very young individuals

is that the remains are very fragile,

and when you're handling them and studying them

it's easy to sometimes think about, um, the children that they were,

the children that died thousands, hundreds, decades ago. Right?

But if you pay attention to them, right,

those children get to speak to you again in a new way.

You can get these very brief snapshots at different phases of growth,

and that's incredibly valuable.

The data that I collect is bone cross-sections.

I mold the outside of the bone

to get a nice replica of the outside of the bone cross-section.

And then I take a couple of X-rays from different angles,

in order to reconstruct the inside of the bone.

I ended up collecting data on over 600 infants and children.

When I got back, what I ended up doing

was developing all these different films by hand.

It was such an enormous relief to see

the slow, hazy emergence of these young kids' bones

finally coming out on film.

Hmm.

Yeah, so this one...

This one's actually pretty small.

Uh, this one's probably around...

around one year old, actually.

Little.

As I looked at the data,

I could see that

there were interesting patterns in early childhood growth

that didn't look very much like adults at all.

When you look at the cross-section of an adult leg bone,

it looks like an upside-down teardrop.

So it's really long from front to back.

However, what I was looking at when I was seeing the kids,

they were not this upside-down teardrop shape,

they were sort of like a wide oval,

and then it started to normalize

and go back towards this adult-like pattern

by the time they're around five or six.

Seeing the bones get suddenly wide

was really surprising and was really exciting,

because it looked like there might be

unique patterns of bone growth

that you only see in little kids in response to walking.

At the time, this was kind of an unusual idea.

Uh, we were still stuck in this mindset

that it was really only adult bones

that responded to exercise.

I'll never forget Reviewer 2

on my very first paper of trying to publish this,

who left me a one sentence review that simply said,

"Children's bones don't respond to exercise."

So that was the kind of pushback that I was dealing with

from some members of the academic community at the time.

But once I had seen this pattern,

I really knew that I wanted to explore this further.

Um, a unique shape just wasn't enough.

Um, so I started talking to a few of my colleagues,

um, about how we could possibly add some data from living children,

um, to this issue.

Now let's see balancey-balancey.

You gotta come and get it.

That's it.

Turn yourself around. Good boy!

He just had no interest in crawling,

and then he sort of started cruising quite a lot,

sort of walking around the table or along the sofa.

Yeah, you've almost got it. Where's the buzzy bee?

You got it.

I still find that he needs that safety net.

Bzzz!

Even when he's walking up the corridor,

he's sort of got one hand on the wall,

just as a bit of a safety.

Round the corner.

Um, I don't feel like he's quite ready yet to take that hand away.

It's quite a nice sort of comfort for him, being able to hold onto the side of it.

Come over to Dada. Hey, buddy. Pas.

Hey. Come here.

Come to Dad.

Come on.

Hey!

He looks so happy with himself.

Good walking.

And then all of a sudden it was like,

"Oh! Oh, he's doing it."

And he sort of did about three or four steps, and then fell over.

And we were like, "Wow, that was his first steps."

Proud of you.

Yow!

It was a real proud moment. I feel like out of all the milestones

that a baby has in the first year of their life,

for me, walking was such... it was a really big one.

- Where's Daddy? - This one. Come on.

Oh! Hey!

Sometimes I do feel like a bone detective.

Um, it's interesting

because I'm always investigating this thing,

uh, the human skeleton,

that most people would not find that informative,

uh, but I had this hunch that the unique shape of the bone I was seeing

in individuals right after they started walking

had something to do with shifting their weight back and forth.

I needed more information.

I really needed some living babies.

Hi.

- You're gonna give it back? - No, we're gonna play with the bat.

- The bat is much more exciting. - Good job.

That's so nice.

I contacted Dr. Cara Ocobock.

She works primarily with locomotion and activity in living humans.

Yeah, right? It sure is hard. It's difficult.

You want it? You can stick it on your hand.

Boop!

So what we're gonna do

is put several of these kind of all throughout her body,

highlighting the major joints,

so we can see how they move when she walks across the floor.

Don't eat it.

We're gonna see how many will stay on before they get torn off

and put into mouths.

And basically, when the cameras look at them,

they're turned into this collection of dots,

and we'll get to see just specifically how those different joints are moving,

- uh, as they walk along. - That sounds fine.

Yeah.

Come back, Freddie. Come back. Yeah.

- Yeah? Big boy. - Yeah, come back.

You guys are doing great.

I think we're gonna have some great walkers.

Yeah.

I wanted to test the fact that babies' bodies can change,

that babies' bodies do actually respond to exercise and loading,

um, in the same way that adults do.

- Go in. All right, we're gonna... - We're just going in.

It'll be helpful for you to hold her when you do.

The type of data that I wanted to have is called "force plate data."

When you look at how adults walk,

the knees are underneath their center of mass,

underneath their bodies,

this allows them to lift up one foot

and not go toppling over and stay balanced on that stance leg.

One of the things that you see is that most of their force

is angled front to back.

What we're actually measuring

is something called "ground reaction force."

You can see, essentially, the ground pushing back up

at these individuals who are walking across the force plates.

- Look at Daddy. Go get Daddy. - Let's go see what Daddy's doing.

With these little toddlers, their legs just go straight down

from the thigh to the knee to the foot, which results in this really wide base.

You got it. Who is it? Don't let it go.

Where's Dad?

Where's Dad?

What we needed to measure was the relative amount

of front-to-back force,

also side-to-side force.

Go get him, go get him!

Perfect! That's a good one.

We use 3D imagery to capture how their body moves

as they walk across the force plate.

One more time, Mabel.

One more.

- Yay, Mabel! - Good job, Mabel.

- Those are perfect. - That's a beautiful shot.

- Beautiful shot. - You did so good!

Mabel is our all-star walker.

Each red line is the step that she's taking, and that's the force.

Oh.

She pushes down on the ground and the ground pushes back up at her.

And so that's what you're seeing.

No.

Look at that.

That's fantastic.

It's very seldom that we actually get to combine skeletal data

with data on living children,

and it couldn't have worked out more seamlessly.

With the 3D data, we could capture

how young walkers actually do shift from side to side,

and in addition to that, the force plates were actually capturing

this side-to-side motion.

Essentially what's happening is during this very unique,

brief period of development,

the body is laying down more bone

on the sides of the legs

in order to resist these forces of toddling back and forth.

It was a long path, but it was really exciting

to get to the point where I could finally confirm my original hunch.

Once they do manage to stand upright and start walking,

uh, that this enterprise actually changes the shape of their skeletons,

and we can actually see that.

You gotta jump.

And I have actually...

Your kid's bones

are affected by everything that child does on a day-to-day basis.

Um, exercise isn't just important for adults,

the bones that are actively forming in a child's body need that stimulus

in order to be healthy.

He got it.

Oh, dear.

So letting your kids run,

letting your kids jump, letting your kids play,

all those things are really important not only for their metabolic health,

but for the actual health of their skeleton.

Oh!

Thank you

Do you see the birdies? Nelson, do you see the birdies?

Yeah?

Okay, you want to walk by yourself? Fair enough.

You're a big boy now.

Good boy!

He's now the one who's dictating

what's happening around him,

so he's walking towards what he himself wants to see.

Bye-bye!

It's like he was sleeping

and he just, all of a sudden, woke up to this new, big, wild world.

Good, Nelson.

It's just fascinating to watch him

become his own person.

Although it's a little bit bittersweet,

because I see my little baby kind of just drifting into this toddler.

Travel broadens the mind.

It's true for adults, and it's also true for babies.

One thing that I've always been interested in...

When babies begin to walk, their whole world expands.

They can travel faster, travel further,

point at things in their environment.

Everyday occurrences become entirely different.

One of the big questions that I've been interested in

is what happens when children begin to walk,

and how does that change their world?

When I was a graduate student, I devised an experiment.

Okay.

All right, so we're just gonna come right in.

We were trying to test whether or not walking and crawling babies

remember objects differently.

You can just have a seat here on the couch.

Okay.

And Nadia can just play on the floor,

and I'll be back to check on you in ten minutes.

- Perfect, thank you. - All right.

We showed crawling and walking babies different objects,

we gave an emotion towards those objects,

then we just looked to see what object did the child play with.

Can you roll it?

There you go.

As part of that experiment,

I happened to give the parent a language survey.

Hi.

Yeah.

There you go.

And this was primarily just to distract the parents

so they wouldn't interfere during the actual experiments.

What have you got there?

Yeah.

That's good.

The main finding was not at all about emotion.

Oh, thank you so much.

Mobile give.

What we learned from the questionnaire was that

walking infants had significantly larger vocabulary sizes,

both in terms of how many words they understood,

but also how many words that they could say,

regardless of their age.

Are you playing fetch with yourself?

That's a doorstop. Can I have the ball?

That's good.

Finding this was a shock, to say the least.

This was something that we had never seen before.

The next decade or so of my life would be spent...

looking into why there was this difference

that I found by accident.

As a new professor at UC Merced

I knew that I really wanted to find out

what is it about walking babies that's different from crawling babies

that explains this difference in their language?

My first hypothesis was that the walking infants would hear more words.

I thought they'd be getting into more things,

and that would elicit more parent talk

about the things that they were getting into.

So we went into about 20 families' homes

to really capture how do parents and children talk

when they're just in their everyday home environments?

- Come on in, you want to chat out back? - Sure.

Let's go have a seat.

All right.

Oh, it's so nice out here.

Yeah, it's a lovely day.

So the idea for today's visit is to get a normal day in Penelope's world.

- Okay. - So what we want to see is

all the words that Penelope hears, and all the babbling that she does.

And to do that, we're gonna have her wear this LENA recording device.

Yeah. And so we're going to have Penelope wear this the whole day.

Once we turn it on, it just stays recording,

and we'll put it into this little vest

so she can simply wear the vest all day,

- and then you don't have to do anything. - Okay.

Okay. So I think it should fit.

- Yeah. - You want to give me a hand?

- Let's get you standing up. - Thank you.

The LENA recording device is a great tool that researchers can use.

It records all the words

that the child hears,

as well as all the babbling and talking that the baby might be doing,

and it really gives us kind of the quantity of language

that the infant is being exposed to in their day.

- There we go, you're ready. - Okay. And that's it.

You and Penelope just have a normal day, go about your daily life,

and then tomorrow I'll come by and pick it up.

Say "bye-bye."

Bye.

Hello, fox.

Do you see the coyote?

Wow.

Whoa!

They're fast, too.

Yeah, the fence.

Yeah, the goats.

- Goats. - Yeah, goats.

What do goats say?

Goats say "maah."

Kind of like that.

Yeah, that one's up on a log.

This is the output that we get from the little recording device.

It actually can extract all the words that the child heard during the day

as well as the words that she might have said.

What we see here are the ebbs and flows, the parent talking,

the number of words that the parent said in five-minute stretches.

So for example, at 10:50, the child heard 374 adult words.

The other thing that the software can do for us

is also look at the child's vocalizations.

The last thing that we can look at are what are called "conversational turn."

So this is almost like a discussion that might be happening.

A ping-pong happening.

That's a lion.

What does a lion say?

What are you doing, bear?

When we looked at the data, it was pretty clear.

In terms of how much the parents said,

walking and crawling babies seem to be hearing

the same number of words during a day.

Similarly, walking and crawling infants seemed to be making

the same number of vocalizations during the day.

Not at all what I was predicting.

So the next thing we wanted to do was to peel back another layer and say,

"Well, let's just not look at quantity, let's actually look at the quality

of the language environment."

Particularly those rich segments during the child's day.

You are a good walker.

So from Penelope's day at the zoo, we had some really nice interactions.

Oh, look at this black and white duck coming up.

Hello, duck.

What does the duck say?

Quack, quack, quack.

Is that a rooster?

Bunny.

This little bit really tells me, as a researcher, a whole lot more.

We hear Penelope trying to say "duck"...

Can you say "duck"?

- Du... - Duck.

...struggling with it. The parent then noticing that,

helping to shape that babbling and repeating the word, "Yes, duck."

- Duck. - Du...

Duck.

And then what does Penelope do? She learns in that moment

how to pronounce the word "duck."

- Duck. - Duck.

Good job! Duck.

Yeah, there are ducks in there.

What's really interesting with a lot of our findings so far

is that there are qualitative differences in how parents are interacting

with their child if they're crawling and walking.

And that, then, is one of the main predictors

of the child's vocabulary development.

Let's go this way.

It seemed as if, once they made that transition from crawling to walking,

no matter what age they were when it happened,

you saw this inflection in their vocabulary development,

and, really, this dramatic increase in terms of

the rate of word learning has a lifelong impact.

You don't go backwards, you only go forwards.

- Whoa, careful down the hill. - He's all right.

You're holding hands.

No matter the age of your child,

talking to your baby is important.

What our research is showing

is that when your child starts walking,

it matters even more.

What is this?

- That is a red river hog. - What is that?

I think it's really important to think about development

as interconnected.

This way.

How did something like language and motor development

and social interactions...

How did they work together

to foster this amazing creature that's unlike any other?

You're always after the camera.

Easy.

Oop-a-la! Oop-a-la!

The first year of life for these little guys

is incredibly challenging.

Oh my God! Oh, my God, Rich, he just walked!

- He just walked! - He just walked!

He did just walk. Oh, my God.

I think I dropped the camera there 'cause I was like, "Oh, my God."

He just walked!

But it's something that's going to shape their body and shape their anatomy

for the rest of their lives.

Thank you for my phone.

There we go. Finally we get you walking.

Walking is a complete game changer for the infant.

It's actually setting them

on a cascade of changes that are gonna happen.

Hi!

The baby's life is forever changed, the parent's life is forever changed,

and most importantly,

the way the baby and the parent interact is forever changed.

Go, go, go!

Kick, kick, kick!

Thank you

Thank you

Star!

"Star!" You're right, Nelson. "Star."

Yeah. And that's an orange walking line.

Learning to walk is the key moment in their development...

because from that moment the world is theirs

and they can go and conquer it.

Augusto was just jumping on his bottom, as usual.

And on one of those jumps...

he just stood up and kept on walking,

as if he had been doing that forever.

We're very happy.

It took him some time,

but, yeah, he caught up.

He's always dancing

and jumping and proving he can do things.