Hi! This is an optional and very brief
look at how humans learn language. So how
do humans learn to talk or to sign their
sign language? There are many theories
and this is an area of research called
psycholinguistics, and the summary is
that there is no consensus. But I thought
might be illuminating to look at the
different theories that we have and how
they compare to what we do with
computers. The main question that we have is
whether being exposed to enough, to many sentences of a language is enough to
learn the language and this is
particularly important for babies: If you
talk enough of a language to a baby, what
are they gonna do with that?
In reality we see that babies learn
language almost miraculously and in two to
three years they're speaking a language.
The main question we have in
psycholinguistics is: Is being exposed to
many sentences enough to learn a
language? Some currents of thought say
"yes", that the input, the sentences that
you hear, are very rich. Rich enough that
you can get cognitive extrapolation
essentially statistical extrapolation of
patterns and that in time these patterns
will emerge as a human language. There's
many different theories for how this
could go, and from the past to the
present they have been called behaviorism,
structuralism, functionalism but in
essence they say that the input is all
you need. That somehow your brain is
going to pull together the cognitive
resources to compute language and to
acquire it. There's a second current of
thought that says "no". That being
exposed to many sentences of a language
is not enough. That somehow the input is
not rich enough. This is called "poverty
of stimulus" and that we have something
in our brain that fills in the blanks
and that essentially the input is a way
for us to fill in those blanks and that
those rules or mechanisms that we have in our brain
essentially will instantiate language.
This kind of thought is called
"generativism". You might be familiar
with Noam Chomsky, for example. He's one
of the proponents of these theories and
essentially what would happen is that
you could have something... theories that
are very aggressive in saying that
humans have a lot of principles and
parameters, for example, in your brain.
They have parameters that need to be
switched on and off depending on the
input that we get. There's some theories
like "Minimalism" and "Merge" that say that
we have a few operations to merge
cognitive objects and doing that we
string together structures in a language.
But essentially these theories say that
the input is not enough. That there's
something about us humans and about our
cognition that is dedicated to language
and that makes us very good at language.
Again, maybe this evolved. Maybe it's some
sort of separate module in our brain, but
that there's something language specific
in us, whereas theories like
functionalism think that we learn
language using a pooling of all of our
cognitive resources. There's one piece of
evidence in favor of generativism
which is that children learn languages
very fast but adults don't. If you've
seen a baby learn... Again, they, in three
years they will learn a human language
and if they're doing it at that rate
there must be learning about 50 words a
day. They can regularize patterns very
easily so for example what we see there
is an object called a "wug". And now
there's another one. There's two of them.
There are two ___, you're probably gonna say
"wugs", and children are able to
successfully do this exercise from a
very young age. They're very good at
generalizing and exploiting patterns in
the data or at filling in their
language acquisition device with the
data. However adults are not good at this.
They need instruction, concentration and
years to learn another language.
Generativists say that we have some sort
of language acquisition device in our
brain that is on from a very early age
and specialized towards language and
that then switches off as we have other
evolutionary focuses, worries in life, such
as socialization, for example. The
functionalists would say that when you're
a baby your priority is to learn language,
so we focus all of your cognitive
resources into this task. Whatever is
happening in your brain we do have a
clear idea of how babies learn, of  what the process is for them to learn how to
speak. They start with very simple
expressions: cooing, babbling, they go
through single words and then
telegraphic stages where they can just
have one or two words together, and then
suddenly their knowledge explodes and
they can put together many longer
sentences. The errors that they make are
fascinating because they over generalize.
When they make a mistake with a word,
it's usually a word that is a weird
exception and they try to say it with
the general pattern. So they are very
good at learning. They learn very fast and they,
whatever errors they make, are very
different from those of a computer so we
probably don't want to model our
computer learning of language in the
human learning. So in summary there are
several theories about how humans learn
languages. Some theories say that we
extrapolate from the data and using
general cognition arrive at knowledge
of the language. Some theories say that
the data is not enough, that there's
something unique about us as humans that
makes us particularly good about
languages.
And there are models for how children
learn how to speak but our computational
models not only are not related to them
but they don't need to be. We do not need
to imitate how humans learn language. All
we need to do is to imitate their
capacity at understanding language and
producing language. We don't necessarily
need to do it in exactly the same way
that humans are. Thanks.
