BBC Horizon Why Do We Talk?

It is probably the most amazing thing you do

and it defines you as being human.

And you do it with ease, so much so you barely notice you're doing it.

Apple! Yeah, apple!

THEY SPEAK IN NATIVE TONGUE

Your ability to talk.

Or more precisely, the way you use language.

THEY SPEAK IN NATIVE TONGUE

Language.

Hi, baby!

From the moment we're born, we have language in our lives.

Hi, baby!

A unique ability that defines us as human.

I can walk up to someone I don't know

and I can make a sequence of noises that I've never made before

by pushing air through my mouth.

I will take a thought in my head and make it go into their head,

and that's an incredible trick.

Other animals may use sounds to communicate

but we're the only ones on the planet who can talk.

Speech and language distinguishes us from all other species.

We are not only using words to be able to express ourselves

but we are really expressing our thought processes

that are unique to ourselves.

For most of us it just happens.

It's such a sophisticated skill

and yet children learn it so easily with minimal effort at all.

That's Mummy.

And when you start thinking about it,

it is quite miraculous how the brain does it.

But despite decades of research, how we learn to talk remains a mystery.

How did this ability evolve?

Why is it uniquely human?

And is it something we are born with or something that we learn?

It strikes me it's surprising and odd

that we know an enormous amount about, for example,

the first fractions of a second in the history of the universe,

but we really know very little at all about what makes us human

and where language comes from.

BABY BABBLES

Daddy.

The wonder of language may not yet be fully understood.

BABY BABBLES

But how we start to talk is now being observed

minute by minute for the first time.

Cognitive scientist Deb Roy realised

that to discover how a child learns to speak...

He'd have to be able to see and hear them 24 hours a day.

His solution was to take the extraordinary step

of turning his own home into a language laboratory,

and his guinea pig was his own son.

My wife and I were expecting our first child

and we had many conversations around, you know, would this be possible,

could we set up our home as an observation space

and actually capture this kind of rich longitudinal record

of our own child's development from birth?

And that's what we set out to do.

And so was born the Speech Home Project,

The most ambitious language observation experiment ever seen.

Cameras and microphones recorded every second of Deb's son's life

from the moment he was born until he was three-years-old.

Capturing in precise detail the process of how we learn to talk.

Baa!

Ball.

Blue ball. Blue ball.

Blue ball, yeah.

From the earliest unintelligible babble

to the emergence of a very first word.

Apple. Apple.

Yeah, apple.

My interest going in was really to understand

the earliest stages of language formation,

and the typical development stages in language,

a child will go from babbling to using single words

usually as a complete request and descriptions,

and then from that they will start what's called the two-word stage

where they'll put two words together like "more milk"

and from that, very quickly more complex grammatical structures emerge.

My focus and my aim was to capture the phase

up to the two-word utterance

and that could happen anywhere between second and third birthday.

It turned out my son was an early talker

so by the time his second birthday arrived

we had the main data set we wanted.

By the time recording was complete,

more than 240,000 hours of information

and 16 million words had been collected.

It's a lot of data but in its raw form it's useless

and so the challenges this now sets up for us

is how do you start extracting the right kind of metadata,

transcripts of who said what,

annotations of where those people were,

annotations of how they're moving

and the relationships that they were in as they were speaking.

And these are the, the tools that we are now building

to analyse the raw data,

and from that, we're starting to see some,

some early insights into the patterns of language development.

Despite the mountains of video footage,

Deb Roy is already uncovering the intricate effect

daily life has on language development.

It seems cooing to your baby is not just instinct, it's essential.

In the months leading up to their son's first words,

he and his wife unconsciously simplified their speech.

Then as their son's own speech develops,

they began to use longer sentences again,

mirroring the child's own development.

What's that over there? Over there, that ball?

Green ball. Oh!

For the very first time, the analysis has also enabled

Deb to piece together the precise emergence of individual words,

charting how a new word is born.

OK, water, water.

Gaga, gaga.

So my son, around his first birthday,

started using the sound "gaga" to indicate water,

and then over the next several months

learned to slowly approximate the proper speech form.

Water.

Just like time lapse video lets you capture a flower blossoming,

what we're going to hear is the blossoming of a speech form.

OK, water?

Water.

Water? Water?

Water.

That's water.

It will take years for Deb Roy and his team to analyse all of the data

but buried within this footage

are the secrets of how we learn language.

If the patterns can be unlocked,

then once this remarkable project is complete

we will have the clearest understanding yet

of how a child achieves the remarkable feat of learning to talk.

By the time a child is five, they'll know as many as 5,000 words.

THEY SPEAKS IN NATIVE TONGUE

My voice changes when I get in a situation.

That requires a rather precise placement of the tip of the tongue.

At the third stroke the time will be five...

Language is exclusively human

and it's something that comes naturally to us.

From their voice, so it's clear the voice is deeply expressive.

Despite decades of intense investigation,

we still know very little about the basic origins of language.

ELEPHANT ROARS

Sunlight.

While other creatures can communicate

their basic needs and emotions to each other,

we're the only species that can convey complex meaning and thought.

T or the D at the end of a word for, say, dot or dog.

It's remarkable that no other animal has ever developed speech.

What is it that makes us unique?

Do this, Vicky.

HE BLOWS RASPBERRY

Another sound resembles the letter K.

Vicky, sit up.

Not even our closest relatives, the chimps, can talk.

Psychologists spent nearly seven years

trying to teach Vicky to speak with little success.

Resembles the letter T.

And in this case they really tried to teach a chimp to say some basic words

and completely failed, and everyone knew of course that,

say, parrots can learn to imitate speech.

So it was kind of a very surprising and eye-opening experience

to see that these chimps with great big brains for an animal were not able to do this.

It was already very clear that chimpanzees

don't have the kind of control over their vocal tract that we do.

So once people knew that chimpanzees couldn't produce speech,

the big question was why?

Scientists believed they knew the answer.

It was all down to our unique anatomy.

We have a larynx, or voice box, that's fixed low down in our throat.

This makes the vocal tract longer

and gives us the physical ability to produce a wide variety of sounds.

The voice box of all other animals was found to be high in the throat,

leaving them incapable of making the complicated sounds of speech

in their short vocal tract.

But nobody had actually ever seen inside the throat of an animal

as it vocalised.

Tecumseh Fitch had a unique piece of equipment

to solve the problem, a video X-ray machine

that had been developed to study animals swallowing.

What we found was really astounding.

It wasn't anything we were prepared for by reading the literature

and here's what we saw.

So what this is is the larynx pulling down out of the nasal cavity

so that during the vocalisation

the animal was vocalising out through its mouth.

The image made no sense so Fitch looked at other mammals,

including Megan the dog.

So you can see the dog's jaw and the tongue.

This is the larynx right here.

And you can see that with each bark the larynx kind of jerks down,

so let's slow that down.

So here's the larynx.

You can see that it's really a quite pronounced descent

of the larynx during the barks. It pulls down.

What Fitch discovered has revolutionised our understanding

of why we can talk.

The mammalian vocal tract is incredibly flexible

so whether we're looking at dogs or pigs or goats or monkeys,