you'll ever accomplish as a human being already happened,

and that is language development.

I mean, think about it.

When you're a baby, all these sounds are coming at you,

and somehow, you're able to figure out

which sounds are words, where there are breaks

between the words, general grammatical rules,

and you're able to apply them without

any real formal training.

This is amazing.

So naturally, a lot of research has

been done into how this ability develops.

And I'm going to tell you about the three main theories that

look at language development.

So first, we start out with the nativist,

or innatist perspective.

And what this perspective says is

that children are born with the ability to learn language.

And the main guy associated with this theory is Noam Chomsky.

And he thought the humans had something called a language

acquisition device, or LAD, in their brains

that allowed them to learn language.

And this isn't really supposed to be

in a specific part of the brain.

It's just an idea that this ability exists.

And this works because he thought

that all languages shared a universal grammar,

or the same basic elements, so all languages would

have nouns, verbs, things like that.

So the language acquisition device

enables the child to pick up on and understand

those types of words and their organization

within a sentence for any language.

This goes along with the idea that there

is a "critical period" or a "sensitive period."

The "critical period" is usually thought

to be from birth until about age eight or nine,

and it's the period of time in which

a child is most able to learn a language.

So if you try to learn a language after that age,

it's a lot harder.

It's not impossible.

It's just a lot harder.

And nativists like Chomsky would say

that that's because the LAD only operates

during that critical period.

Once you start using it, then it specializes to your language,

and it becomes unable to detect other sounds and grammar

from other languages.

The second theory I want to tell you about

is the learning theory.

Learning theorists think that children

aren't born with anything.

They only acquire language through reinforcement.

So a learning theorist would say that a child learns to say

"mama" because every time it makes it sound that approaches

that-- so "ma-something"-- then Mom starts smiling,

hugging the child, so over time, the child learns, oh,

the more I make this sound, the more I get hugs and smiles.

And so then, eventually, it learns to say "ma,"

and then say it again, and learns to say "mama."

So this makes sense.

But a strict learning theory doesn't

explain how children are able to produce words they've never

heard before or produce unique sentences.

So we have another theory called the interactionist approach.

Sometimes this is called the social interactionist approach,

because these theorists believe that biological and social

factors have to interact in order for children

to learn language.

So they would say that children strongly

desire to communicate with others,

such as the adults in their lives,

and that desire motivates them to learn

to communicate via language.

And the main theorist associated with this school of thought

is Vygotsky.

He was a big proponent of the importance

of social interaction in the development of children.

All three of these theories have made big contributions

to our understanding of how children develop language.

So the next time you look at a baby, be impressed.

They're actually working really hard.