days – our methods, our theories,

our ideas – are shaped, to some extent,

by Piaget's influence. And so, what I want to do is

begin this class that's going to talk about cognitive development

by talking about his ideas. His idea was that children are

active thinkers; they're trying to figure out

the world. He often described them as

little scientists. And incidentally,

to know where he's coming from on this, he had a very dramatic

and ambitious goal. He didn't start off because he

was interested in children. He started off because he was

interested in the emergence of knowledge in general.

It was a discipline he described as genetic

epistemology – the origins of knowledge.

But he studied development of the individual child because he

was convinced that this development will tell him about

the development of knowledge more generally.

There's a very snooty phrase that--I don't know if you ever

heard it before. It's a great phrase.

It's "Ontogeny recapitulates phylogeny."

And the idea of this--What that means is that development of an

individual mimics or repeats development of the species.

Now, it's entirely not true, but it's a beautiful phrase and

Piaget was committed to this. He was very interested in

saying, "Look. We'll figure how a kid develops

and that will tell us about the development of knowledge more

generally." So, Piaget viewed the child as

a scientist who developed this understanding,

these schemas, these little,

miniature theories of the world.

And they did this through two sorts of mechanisms:

assimilation and accommodation. So, assimilation would be the

act of expanding the range of things that you respond to.

Piaget's example would be a baby who's used to sucking on a

breast might come to suck on a bottle or on a rattle.

That's changing the scope of things that you respond to.

Accommodation is changing how you do it.

A baby will form his mouth differently depending on what

he's sucking on. And so, these processes where

you take in--I'm giving this in a very physical way,

but in a more psychological sense you have a way of looking

at the world. You could expand it to

encompass new things, assimilation.

But you could also change your system of knowledge itself –

accommodation. And Piaget argued that these

two mechanisms of learning drove the child through different

stages. And he had a stage theory,

which was quite different from the Freudian stage theory that

we have been introduced to. So his methods were to ask

children to solve problems and to ask them questions.

And his discoveries that--they did them in different ways at

different ages led to the emergence of the Stage Theory.

So, for Piaget, the first stage is the

sensorimotor stage or the sensorimotor period.

For here the child is purely a physical creature.

The child has no understanding in any real way of the external

world. There's no understanding of the

past, no understanding of the future, no stability,

no differentiation. The child just touches and

sees, but doesn't yet reason.

And it's through this stage that a child gradually comes to

acquire object permanence.

Object permanence is the understanding that things exist

when you no longer see them. So those of you in front,

you're looking at me and I go. It occurred to me it'd be a

great magic trick if I then appeared in back.

But no, I'm just here. That's object permanence.

If I went under here and then the people said,

"Where the hell did he go? Class is over," that would show

a lack of object permanence. So, adults have object

permanence. Piaget's very interesting claim

is that kids don't. Before six-month-olds,

Piaget observed, you take an object the kid

likes like a rattle, you hide it,

you put it behind something, it's like it's gone.

And he claimed the child really thinks it's just gone.

Things don't continue to exist when I'm not looking at them

anymore. And so he noticed they--they're

surprised by peek-a-boo. And Piaget's claim was one

reason why they're surprised at peek-a-boo is you go--you look

at a kid, the kid's smiling and go,

"Oh, peek-a-boo," and you close--and you cover your face

and the kid says, "He's gone."

"Peek-a-boo." "Oh, there he is.

He's gone." And you really--That's the

claim. Piaget also discovered that

older children fail at a task that's known as the A-not-B

task. And Peter Gray in his

psychology textbook refers to it as the "changing hiding places"

problem, which is probably a better name for it.

And here's the idea. You take a nine-month-old and

for Piaget a nine-month-old is just starting to make sense of

objects and their permanence. You take an object and you put

it here in a cup where the kid can't see it,

but it's in the cup. So the kid, if you were the

kid, will reach for it. You do it again, reach for it.

You do it again, reach for it. That's point A.

Then you take--you move it over here.

Piaget observed kids would still reach for this.

It's like they're not smart enough to figure out that it's

not there anymore, even if they see it move.

And this was more evidence that they just don't understand

objects, and that this thing takes a lot of time and learning

to develop. The next stage is the

preoperational stage. The child starts off grasping

the world only in a physical way, in a sensorimotor way,

but when he gets to the preoperational period the

capacity to represent the world, to have the world inside your

head, comes into being. But it's limited and it's

limited in a couple of striking ways.

One way in which it's limited is that children are egocentric.

Now, egocentrism has a meaning in common English which means to

be selfish. Piaget meant it in a more

technical way. He claimed that children at

this age literally can't understand that others can see

the world differently from them. So, one of his demonstrations

was the three mountains task. We have three mountains over

there. You put a child on one side of

the mountains and you ask him to draw it, and a four- or

five-year-old can do it easily, but then you ask him to draw it

as it would appear from the other side and children find

this extraordinarily difficult. They find it very difficult to

grasp the world as another person might see it.

Another significant finding Piaget had about this phase of

development concerns what's called "conservation."

The notion of conservation is that there's ways to transform

things such that some aspects of them change but others remain

the same. So, for instance,

if you take a glass of water and you pour it into another

glass that's shallow or tall, it won't change the amount of

water you have. If you take a bunch of pennies

and you spread them out, you don't get more pennies.

But kids, according to Piaget, don't know that and this is one

of the real cool demonstrations. Any of you who have access to a

four- or five-year-old, [laughter]

a sibling or something--Do not take one without permission,

but if you have access to a four- or five-year-old you can

do this yourself. This is what it looks like.

The first one has no sound. The second one is going to be

sound that's going to come on at the end.

But there's two rows of checkers.

She asks the kid which one has more.

The kid says they're the same. Then she says--Now she asks him

which one has more, that or that.

So that's really stupid. And it's an amazing finding

kids will do that and it's a robust finding.

Here's another example. So, they're the same.

So, it's a cool finding of that stage, suggesting a limitation

in how you deal and make sense of the world.

The next phase, concrete operations,

from seven to twelve, you can solve the conservation

problem, but still you're limited to the

extent you're capable of abstract reasoning.

So the mathematical notions of infinity or logical notions like

logical entailment are beyond a child of this age.

The child is able to do a lot, but still it's to some extent

stuck in the concrete world. And then finally,

at around age twelve, you could get abstract and

scientific reasoning. And this is the Piagetian

theory in very brief form. Now, Piaget fared a lot better

than did Freud or Skinner for several reasons.

One reason is these are interesting and falsifiable

claims about child development. So claims that--about the

failure of conservation in children at different ages could

be easily tested and systematically tested,

and in fact, there's a lot of support for

them. Piaget had a rich theoretical

framework, pulling together all sorts of observations in

different ways, wrote many, many books and

articles and articulated his theory very richly.

And most of all, I think, he had some really

striking findings. Before Piaget,

nobody noticed these conservation findings.

Before Piaget, nobody noticed that babies had

this problem tracking and understanding objects.

At the same time, however, there are limitations

in Piaget's theory. Some of these limitations are

theoretical. It's an interesting question as

to whether he really explains how a child goes from a concrete

thinker to an abstract thinker, or how he goes from not having

object permanence to understanding object permanence.

There's methodological limitations.

Piaget was really big into question and answer,

but one problem with this is that children aren't very good

with language, and this might lead you to

underestimate how much they know.

And this is particularly a problem the younger you get.

Methodology is going to loom heavy in the discussion of any

science and that includes psychology.

Often 90% of the game is discovering a clever method

through which to test your hypotheses.

We're going to talk a little bit about that regarding babies.

I'll give you another example from a very different domain.

There was a set of scientists interested in studying tickling.

So, when you tickle somebody, under what circumstances will

they laugh? Where do you have to tickle

them? Can you tickle yourself?

Does it have to be a surprise, and so on?

It turns out very difficult to study this in a lab.

You're not going to have your experimental credit.

You come into the lab and say, "Okay.

I'm the graduate student. Ha, ha, ha."

And [laughter] in fact, an example of a

methodological attempt was done by Henry Gleitman at University

of Pennsylvania, who built a tickle machine,

which was this box with these two giant hands that went

"r-r-r-r." This was a failure because

people could not go near the tickle machine without

convulsing in laughter. But we will discuss when we

have a lecture on laughter a bit of the tickle sciences.

And finally there's factual. What do infants and children

really know? It's possible that due to the

methodological limitations of Piaget, he systematically

underestimated what children and babies know.

And in fact, I'll present some evidence

suggesting that this is in fact--that this is the case.

So, I want to introduce you to the modern science of infant

cognition. Infant cognition has been

something studied for a very long time.

And there was a certain view that has had behind it a

tremendous philosophical and psychological consensus.

And it's summarized in this Onion headline here.

And the idea is that babies are stupid, that babies really don't

know much about the world. Now, the work that this

Onion headline is satirizing is the recent

studies, which I'm going to talk about,

suggested that on the contrary, babies might be smarter than

you think. And to discover the

intelligence of babies we have to ourselves be pretty smart in

developing different techniques. To study what a baby knows,