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PROFESSOR: So last week
Melissa told you--
or a couple days ago--
about vision.
And if there's two huge
messages, I think, out of that
lecture, it's first that even
the most simple aspects of
perception are based on a
synthesis between what's out
there and the rules
by which your mind
interprets the world.
And what you ultimately see
is that interaction, that
synthesis, that dialogue, that
construction between what's
out there and how your mind
chooses to interpret it.
The second big point is there's
a lot of organization
of the visual system
in our brain.
And we can track its
organization from the first
moment that photons enter your
eyes all the way through until
you recognize a loved one, a
word, or an object out there.
And we said that in the
neocortex, the world is
divided into two big channels
of visual processing, which
are what things are and
where things are.
So now I'm going to pick up on
that a little bit today.
As you go around and see things
all the time, what is
it that you mostly see?
On an average day, you wake
up in the morning.
I know you're all like,
what's he looking for?
What's the answer?
But just in everything.
You see people a lot.
So faces, we'll talk
about that.
You see objects, chairs,
tables in the morning.
A toothbrush and soap
is useful, right?
You see objects.
And another huge use of your
visual system is reading.
You see words, right, on
books, on computers.
So we're going to talk a little
bit about how we see
what things are, objects in the
world, faces in the world,
and words so that we can read.
And we'll talk about both some
processes that go on in our
mind and brain that let us
become terrific at recognizing
what's out there and knowing
who we're talking to, what
we're reading, what we're
holding, and so on, and then
about disorders in the brain
that illuminate, I think, a
little bit about those
processes.
So let me start with objects
and agnosia.
Agnosia means not knowing.
So we're going to talk about two
ways in which people seen
to not know.
And that gives us a hint,
then, about how
we actually do know.
And they've been called
apperceptive
and associative agnosias.
Apperceptive seems to be people
see the parts, but they
don't pull it together.
Associative agnosia,
they see the whole
thing pretty decently.
But they can't figure out what
it means, what it is in a
practical sense.
And, lastly, I'll talk to you
about a very surprising
finding where people lose
knowledge of some kinds of
objects in the world but not
others, and sort of give us a
new insight into how our brain
organizes knowledge.
So agnosia is a
modality-specific inability.
So we'll talk today
about vision.
There's agnosias in audition,
and in touch, and so on.
But I'll focus just on vision,
modality-specific.
These people are fine
if they hold
something or hear something.
And it's not explained by things
like you don't see so
well, or you're not paying
attention, or you can't speak.
It seems to be just that you
lose the ability to recognize
by sight what something is.
So again, apperceptive agnosia,
will link it to the
right hemisphere and associative
agnosia to the
left hemisphere.
And let me show you examples
of what these patients do.
So here's patients with right
hemisphere damage.
We're attempting, simply, to
copy this triangle or copy
these things.
It's right in front of them.
They're copying it.
And you can see that it's as
if they have almost no
appreciation for what the
thing is out there.
This is a pretty miserable 3.
Right in front of you, it's as
if the whole thing weren't
cohering for anything.
Even a shape is just a
mysterious bundle of stuff.
Or we can make it
multiple choice.
Well multiple choice,
we know it's easier.
So all they have to do is cross
out which of these four
things looks like this.
And they picked the
circle here.
Or instead of the x,
they picked the o.
They're really not getting
almost anything about the
quality of the shape.
They're really not recognizing
what they're looking at.
Or they'll see this.
But they'll read it as, when
they get this, 7415.
They won't take the first
interpretation, but will come
up with some other.
When these patients copy
something, they see, right in
front of them, that elephant.
You can label things.
But it's a pretty bad copy.
It's not just bad artistry.
It's a bad sense of what the
coherent shape is right in
front of them.
And their vision is
basically fine.
It's just the shape of it
doesn't make any sense.
Not surprisingly then, maybe
these patients also struggle
when you make things
a little harder.
So what letter is this?
You can get that.
You'd have to look a
little bit harder.
Or you might get that this is
a cow, or this is a car.
These patients are terrible
at those things.
As soon as you make
it a little bit
hard, they're finished.
They're also bad if they have
damage in the right
hemisphere, posteriorly,
at what they
call an unusual view.
So often we see something like
a stapler from this view.
We rarely quite see
it this way.
But if I showed you this, you
could probably make it out.
It might take you a
moment by itself.
An unusual view of an object
that you see, psychologists
call it a canonical view,
which is the usual one.
And what happens to patients who
have damage in the right
posterior cortex?
They're terrible at making this
unusual perception of a
common object.
They're also terrible if they
have to see something that's a
little bit challenging.
Again, like here's some
hats but with shadows.
Now normally, we don't
think about
shadows as a big problem.
It is for computers that
are meant to see.
And it is also a big problem
for patients with damage to
the right posterior cortex.
It's as if they can't pull out
the object from the shadow.
It's all one big glob to them.
Compare that difficulty just
getting basically what's there
to patients with left hemisphere
damage who can't
recognize an object.
So here's a patient who was
shown pictures of a key, a
pig, a bird, a train, and
was asked to copy them.
And the copies are actually
excellent.
I mean, they're much better
than I would do.
They're excellent
copies, right?
But even after the patient has
made that excellent copy of
the key, he's asked
what is that?
And the patient says,
I don't know.
Good copy of a pig, "Could be
a dog or any other animal."
That's a dog, but that's it.
The bird is kind
of interesting.
He draws a pretty good bird,
his copy, right?
But then he says, "It could be
a beach stump." And when you
say that, you can see that.
But you and I would never
come to that conclusion.
And the train, he gets
a little bit of wagon
or car of some kind.
It's a larger being pulled
by a smaller.
He vaguely knows
it's something.
But it's not quite
right either.
But he really gets what
it is, the shape.
But it's as if it's stripped
of meaning.
It just doesn't mean
anything to him.
Now we're going to do
a video in a moment.
All right, Tyler?
I'm going to show you
some videos today.
The problem is that these videos
are sort of grainy.
And there's not really high
quality Alan Alda talking on
Scientific American videos
of these patients.
So the unfortunate thing is
in a visual disorders
demonstration, it's almost as
if I'm forcing upon you that
same visual disorder.
OK?
Because you're looking at it,
and you go, like, gee.
No wonder he can't
recognize it.
I can't recognize it.
So let me tell you.
In a couple moments he's
going to look at a
picture of a clarinet.
And if it were a really
good video, you
would see it clearly.
But there's just not many
of these around.
And these patients are rare
that are this perfect.
So I'm going to make
this dark.
And we'll see-- thank
you, Tyler--
a patient with visual agnosia.
And you should be impressed
by two things.
First, he's very verbal.
He's speaking.
He's smart.
A lot of his brain is
working just fine.
And second, you're going to
see something kind of
interesting, which is
we talked about the
where system last time.
And sometimes people call
the where system,
the system for action.
Because pretty much like where
you grab something, where you
move, that has a lot to do with
the action, the physical
action in the world.
So you're going to can see this
man unable to recognize
by his what system, what
he's looking at.
But a little bit of information
is going to sneak
into his where system, and move
his hands in a way that
you'll see appropriate.
So thanks.
So it's so funny if
you work in--
this idea that we only
use 10% of our brain.
I can assure you this man has
95%, 98% of his brain.
He can speak.
He can move.
He can make jokes.
He can curse at the end
there a little bit.
He can do almost everything
that everybody can do.
But he cannot identify what
an object is by vision.
Because the injury has occurred
in the part of the
brain that's essential for that
final step of figuring
out what you're looking for.
It's a very specific
part of the brain.
And without it, the rest of
his brain can't figure out
what it's looking at.
So his sensation is fine.
He sees where it is.
And he gets the shape
even roughly.
He thought it was a pen.
There's something vaguely
about the shape.
His naming is fine.
But it's as if, again, this idea
of a perfect example of
what we call associative
agnosia.
He has all the shape information
it seems like you
ought to have, all the language
information you have.
But he can't make that move
from piecing together what
something is to knowing
what it means.
And if he doesn't know what
it means, he can't
come up with the name.
If he smells it or holds it,
he says, apple or pipe.
He knows the name.
But if he has to look at
something and then know what
it is to name it, if I show you
a piece of paper and ask
you to name it, you have
to say, what is it?
Then I name it.
He can't make that move in
vision to what it is.
Because so much processing
has to occur in your
brain to get there.
Even though it seems
instantaneous
and trivial to you.
It's instantaneous and trivial
to you because your brain is
so brilliant that it
accomplishes it.
Now, there are things out
there in the world like
animals that occur naturally.
Because they're from an
evolutionary tree, they share
a lot of shapes.
And there's things out there
that are not living, either
that occur like the moon and
the mountain-- they're out
there sitting--
or what we call manufactured
objects, things like locks,
pencils, motorcycles, bulbs,
things that humans have made.
And, of course, humans make
shapes as they need to
construct things.
They're not constrained by
evolutionary forces about what
shape something is.
We make a shape as we need it.
But it was still an amazing
discovery in the 1980s that
they found individual patients
who lost the ability to
recognize things and various
specific categories.
This seems so much like old
style, silly phrenology.
That I can tell you, my
colleagues sort of make fun of
me when I told them people in my
field were following this.
So they found patients who
could define by pictures
manufactured objects, things
like pencils, or typewriters,
or computers.
But they couldn't identify
foods or animals.
And then they found patients
just the opposite who could
identify foods and animals but
not manufactured objects.
So that's really weird.
That's as if you had organized
in your brain the manufactured
section here like in
a supermarket.
And here's the animal section.
And here's the fruit section.
Really, is that how our mind
is organized, like a
supermarket?
But then there were some
exceptions to these.
And there are the exceptions
that helped us
inform us on the rules.
So here's some patients who are
really good at identifying
manufactured things-- again,
pencils, things like that--
bad at foods and animals.
But now think about this.
They were good on body parts.
How were they good on body parts
when they were bad at
foods and animals?
Body parts are natural, right?
And they were bad a musical
instruments even though they
were good on other manufactured
things like
pencils and computers.
So these were two
wrong things.
And I'm going to try to convince
in a moment that the
way we now understand this is
they're good at body parts
because we know how
to use our body.
And they're bad at musical
instruments because musical
instruments look an awful lot
like one another just like
four-legged animals look
a lot like one another.
That's a funny category for us
if we start to divide up
instruments.
So the problem is not so much
one of natural versus
unnatural things.
It's things that we know through
vision versus things
that we know through physical
action and use.
And here's another example.
The patients who are bad at
objects that we use every day,
like pencils and stuff like
that, were pretty good on
things like billboards
and mountains.
Now only in science fiction
movies do you have creatures
big enough that they're picking
up billboards and
throwing it at helicopters
from the military.
You see that all the time.
You have the big creature.
And they pick it up,
and they hurl it.
OK.
So we don't mostly pick up huge
things like mountains and
large outdoor objects
like flag poles.
They're not things that
we pick up and use.
So it seems like the principle
of what's good or bad is more
about how we experience things
through sight or through
physical action.
So how do we know things in
the world through visual
experience?
Unless we're alligator
wrestlers, we don't get that
near that many animals.
And most of us have other things
that we use all the
time, like bulbs, and pencils,
and things like that.
And evidence for
that was this.
They put humans inside a scanner
and looked at their
brains as they named either
line drawings or words.
So let's think of words.
So it's just words, and you're
naming things like elephant
and tiger--
that's the animal--
or tools that you use, like
pliers or hammer.
Visually, they're words.
But what happens in the brain
as you're naming animals?
It seems like you turn on
the visual parts of
your brain a lot.
There's no animal in there.
There's not even a picture
of an animal.
It's just the word elephant
or the word cat.
What happens when you're
naming tools?
In the left hemisphere, we see
turned on an area here that's
involved in visual motion, and
here, in physical action of
moving things in the world.
All you're doing is
naming words.
But it's as if the knowledge for
naming them is located in
the part of your brain that
uses that information.
If there's things I recognize
by sight, the abstract
knowledge about those things
is near my visual system.
If there's things I recognize
by action, using them, the
abstract knowledge of that is
located in your brain near
parts of your brain that move
things and pick up things.
So all of a sudden, it makes
sense that you can get
separation in these forms
of knowledge.
Because they reside in your
brain near the parts of your
brain that use them and
communicate with them.
So again, this idea that if
it's a [INAUDIBLE] like a
scissors, your knowledge about
scissors will reside in the
parts of the brain that
act upon scissors.
If it's something like a bird
that you mostly see, knowledge
about that bird, not just how it
looks, but everything, will
reside in parts of the brain
that are focused on vision.
So it's as if your knowledge
is moved to the part of the
brain that interacts with
the form of knowledge.
So now let's talk about faces.
Faces are a huge thing for us.
There's at least two huge
things we do with faces.
We recognize who people are
and what their moods are,
angry, happy, nice, and so on.
So here's one person.
Here's another person.
When I first used this picture,
he wasn't a governor.
He was a movie star.
And now he's an ex-governor.
And you have the problem
that you have to
recognize a lot of people.
Because you have all your
classmates, and friends, and
family members, and a lot
of people out there.
And not only that, you have
to recognize the various
expressions they have, which are
terribly important for how
we communicate with people
moment to moment all the time.
So we could say with faces,
our big job is who are we
looking at.
A friend, or foe, somebody
loved, somebody we don't know.
Who is that person?
And then what's the expression
that we can
read from their face?
That's a huge part of our lives
as social animals, as
people who interact
with other people.
So you saw a film last time of
a patient with prosopagnosia.
Your book, this time, talks
about a Dr. P. He's the man
who mistook his wife
for a hat.
So he has bigger problems in
vision than simply faces.
But faces are very impressive.
He fails to recognize his
students by their face.
But he can recognize them
by their voice,
modality-specific.
His general vision is OK.
When Oliver Sacks visited him
in his house, he tries to
reach out his hand and took hold
of his wife's head, tried
to lift it off to put it on.
He had apparently mistaken
his wife for a hat.
His wife looked as if she
was used to such things.
You can see the head and the
hat, they're kind of close.
But not if you have
typical vision.
He might pat the head of water
hydrants and parking meters
mistaking them for the
heads of children.
There's a little bit of logic.
But it's pretty wrong
what he sees.
And it's pretty meaningless
to him.
So let me show you a
film of an example.
You saw one last time.
So let me say a word
about this.
Imagine that if you couldn't
recognize people
as you walked up.
So much of how we recognize
people-- we don't think about
this, because we instantly,
easily recognize
those we know well--
is by their faces.
So I want to say a
couple of things.
Usually there's posterior
cortical lesions
like in this woman.
I knew one man who was a
Unitarian minister, who I
worked with, actually, a couple
blocks away here,
He went up to Dartmouth for
the winter carnival.
He came back in a small
Volkswagen.
It turned over turned
over on the ice.
He had a huge brain injury
and became prosopagnosic.
He could only recognize his wife
by asking her to wear a
yellow bow in her hair.
Because otherwise he
couldn't pick her
out from other people.
When he went down the street
and passed his brother, he
completely failed to
recognize him.
Then the brother spoke.
Then he recognized him.
And he said-- and this was his
subjective experience--
because you wonder what
do these people
feel like they see.
He said that what it felt like
for his brother was, do you
when somebody has some bad
handwriting, and you can't
make it out at all?
And then somebody tells
you what it is.
And you go, oh yes.
That's that word.
Any now you see it.
He said, that's what it felt
like as he heard his brother's
voice and realized it
was his brother.
It's hard to know how to
relate these things.
But the ability to recognize a
person is completely wiped out
of these individuals.
In the last six or seven years,
something else has been
discovered.
Now let me tell you
a word about this.
Instead of people with acute
lesions that they got because
of a brain injury.
It turns out there's a couple
percent of our population
that's really bad at recognizing
faces, not the
occasional social embarrassment
that many of us
have when we see somebody, we
know we should know them, but
they're really, really,
really bad.
There's websites you can go to
that let you test yourself.
Because researchers want you
to work with them if you're
one of them.
It's about 1% of
the population.
They're really, really,
really bad.
There was one woman described
as, she says,
they can't watch movies.
Because all the characters
look pretty
much the same to them.
You can imagine that.
One parent who has this problem,
really terrible at
faces by formal testing, says
that when her kid comes out of
school, her own kid, if he is
not wearing the clothes that
she knows he's wearing, she
can't pick him out from the
other children very easily.
And these are not people with
big brain injuries.
These are people who have some
unusual difficulty in
recognizing faces.
So in a classroom this
size, there easily
could be one of you.
We don't understand
what that is.
It's not a brain injury.
Just like some of us can't carry
a tune, some individuals
are really terrible at
recognizing faces, really bad.
So there's a lot of research
into that to understand what
that reflects.
So let me tell you what we do
understand about the neural
circuitry in the typical brain
for recognizing a face of a
loved one, a person that
you care about.
So this is the fusiform gyrus.
It's a structure in the back of
the brain that extends from
the occipital into the
temporal lobes.
And that's an anatomical
description of this region.
Within that region, there's a
functional area that seems
very important for
face perception.
And Nancy Kanwisher, who's in
our department, pretty much
discovered this specific
functional area in the typical
human brain.
And so she did experiments where
she would present things
like faces or objects.
In this picture, left is right,
and right is left.
There's a spot in the fusiform
cortex that has
this following property.
Here's faces.
That turns on.
Here's objects which have
similar properties.
It has a lot of visual
information like a face.
But it's not a face.
It's part of the brain region
not so interested, faces,
objects, faces, objects.
So whenever faces come on--
this is, by our understanding--
the first part
of your brain that says,
I'm looking at a face.
Up until then, it's just treated
like other stuff.
This is the first part of your
brain that recognizes, I'm
looking at a face.
I'm starting to identify who
I'm looking at and what
feelings they might have
by their expression.
And Nancy and her colleagues did
all kinds of very clever
experiments to show the
properties of this.
Let me pick one.
You could say, well, it's
not about faces.
But faces are about humans.
Maybe it's a part of the brain
that tells you when there's a
human around you.
So they compared faces
versus hands.
Here's hands.
This part of the brain is
not that interested.
Faces, hands, faces, hands.
You see every time it moves to
faces, this part of the brain
gets very strongly engaged.
It's very much about faces
by many research studies.
So let me tell you a little bit
about what we understand
about faces in terms
of development
and things like that.
Because faces are such a big
part of our lives from the
first few moments we're born.
In fact, a colleague of mine,
Pawan Sinha, did a kind of a
biographical research study that
was on the front page of
The New York Times and earned
MIT faculty the continuing
names of being Frankenstein
faculty.
There was a number of faculty.
And what he did, kind of very
cleverly, was he put on his
newborn infant's head
a little camera.
And he said, if I leave
it on there and
record it all the time--
and apparently there was some
debate with his wife whether
he was allowed to do this.
But they checked it out.
It seemed OK by the
pediatrician.
He said, if I have the camera
on the infant's head, I can
see what the infant's experience
is like moment to
moment in the first months
of its life.
And I can also play with the
video so that it has, roughly
speaking, the properties of the
infant's visual system,
which is it can't see very
far after its birth.
They can only see very close
by, and not that well.
Over the next several months--
we'll talk about
this later in class--
he gets better and better
at seeing at a distance.
So here's the infant sitting
in his or her crib.
And this video makes incredibly
clear, beautifully
and fascinatingly clear,
something that I never thought
of until Pawan did this study,
this examination.
So the infant sitting there,
it can't move very much.
It can't go very many places
as a newborn infant.
So what does it see?
What gets close enough to it to
be visible to the infant?
People's faces.
Because all the other cute
things in the nursery, all the
other things that are there,
they are too far or too blurry
for the infant to process
almost at all.
Almost the only thing that
happens is the parent, the
grandparent, the siblings, the
friends that come over and go,
what a cute baby.
Baby, baby, baby, baby.
The face comes in.
The person's done, gone.
Now you're just sitting
in a world of blur.
Here comes another face.
So besides certain issues
related to perhaps the
feeding, the only thing
the infant sees are
faces all the time.
So it's a very important
social cue of who it's
interacting with and
what's out there.
And it's almost the only
one available to it.
So psychologists have known for
some time that if you show
a very young infant a face
versus something like an
object, like a car or anything
like that, they're much more
interested in faces if you put
them next to each other where
the infant can see them.
And they've been saying,
well, is the brain
born to process faces?
And it might be.
And I'll show you evidence
to suggest in some
general sense it is.
What is that infant's
brain drawn to?
What does it find fascinating
to learn about in the world?
And so they notice that one
thing about a face is in terms
of features, eyes, nose,
mouth, top-heavy.
Because we have two eyes, and
everything else is one and
one, the nose and the mouth.
So here you can move the
features like this.
And it turns out not only are
infants more interested in
this kind of face than this--
and they know that because
they'll put the two up, and
they'll measure how long the
infant looks at one versus the
other, which is interesting.
And the infant picks this one.
But get a load of this?
The infant also picks this one
versus this, this one versus
this, and this one
versus this.
Now these look very little
like a face.
But they're top-heavy.
It's as if maybe the infant's
brain to start with, maybe,
looks for some interesting,
top-heavy things and that
pulls it into the
world of faces.
Here's some more experiments
like that.
So here's an upside down,
right-side up.
Baby looks more at this
kind of face.
OK.
You could say, well, that's
a normal face.
But it's also top-heavy.
Then they'd make these kind
of scary-looking faces.
And now the baby, even though
these are nothing like a face
the baby ever sees, it
still likes this one
because it's top-heavy.
Now how about this one?
This is like a face they see.
This is a really weird face.
Right?
They'll never see a face like
this except in this
experiment.
Top-heavy.
Top-heavy.
And now the infant looks at
both of them with equal
interest and delight.
So that's a very clever
experiment to suggest that the
infant's mind is looking
for top-heavy things.
And you could say, is
it really top-heavy?
Or Is that what the infant's
mind and brain can look for?
And it goes with faces.
And evolution picked that.
It's hard to know how to think
about these things.
But it looks like the
top-heaviness draws an infant
to be fascinated by faces.
And luckily, you don't get
many faces like this to
confuse you in the real world.
Another thing that people
have studied a lot
about faces is this.
They use the word configural.
The relations among the parts
are more important than the
parts themselves.
So I need a volunteer
in their seat.
And this is going to be really
easy if you know the alphabet.
You have to put up your
hand and help me out.
OK.
Thank you very much.
I'm going to describe to you
a letter by its features.
OK?
It has a big line at the top.
And in the middle, there's
a line that
goes down to the bottom.
What's the letter?
AUDIENCE: T.
PROFESSOR: Awesome.
OK.
Featural description.
Now I'm going to describe to you
a super famous movie star.
And this person has two eyes to
the left and to the right,
a nose right below that, and
a mouth right below that.
And who is it?
Angelina Jolie.
So what's my point here?
It's the stuff that helps us
in many things, like the
letters-- thank you.
That was excellent.
We can describe those
by the parts.
And the parts pretty much
define the whole.
That's not true for faces.
It really is the precise
relations between eyes, and
nose, and mouth that tell us.
And there's an experiment that
shows this in a very empirical
direct way.
So they would show people
a face like this with a
particular nose or a house
like this with
a particular door.
And then they would test your
memory for that nose or that
door by itself as features or
with the whole face or a whole
house present.
And here's what happens for
people's performance.
The nose by itself, the door by
itself, the nose when you
see the whole picture, which
could be his nose.
It could be another nose.
Here's the door.
It could be that door
or a different door.
And here's what happens
in performance.
If it's houses, people are good
for doors, about the same
whether they've identified the
door by itself or the door in
the context of the house.
If it's noses, they were
a lot better off
seeing the entire face.
It's as if how we analyzed even
the parts of the face are
really integrated immediately
into the other
aspects of the face.
They don't stand alone.
They're a part of a context
all interacting together.
Now here's something pretty
striking and interesting.
And we'll talk about some social
implications of this at
the end of the lecture.
You can't ask infants
many things.
But you can record their
behavior and learn some things
about what their minds are
representing and thinking.
And here's how they test an
infant at say six months of
age, can't talk, can't walk,
can't be instructed to push
buttons or fill out surveys.
How do they get inside the mind
of what an infant knows?
What they'll do is they'll
show a face.
And pretend they show this
face all by itself.
Infant looks for a little bit.
Face disappears, and then they
see the face they just saw and
a new face.
And infants who saw this face
a few moments ago will spend
more time looking at the new
face than the old face.
You can track where
their eyes are.
And that's the evidence they
remember the face they saw
before, because they selectively
spend more time on
the new face.
And also they're hungry to
look at the new face.
I've seen this face, been
there, done that.
New face, check out
this person.
If you test them at six
months, they'll have a
preference for the new face.
But if you show them two
different monkeys--
and this might feel hard for
you to tell these apart--
if you show them two different
monkeys, they'll behave the
same with monkey faces as they
do with human faces.
They'll prefer the novel face,
which shows you they remember
what face they saw before and
want to look at the new face.
And at six months, it's the same
for humans and monkeys.
And don't forget, most of these
people are interacting a
lot with adults, and siblings,
and caretakers.
Not many of them are hanging
out with monkeys.
They start to get much more
accurate for human faces.
The experience they have with
human faces starts to make
them much better that.
At birth, faces from
one species
are as good as another.
But with practice and
experience, they become human
face specialists.
And they become much
better at that.
So it's not in our genes to
be awesome at human faces.
But there's something
about faces.
And then a lot depends
on what we see.
And we grow that part of
our mind and brain.
So here's a remarkable
experiment, that you couldn't
do with people, that was done
with infant monkeys.
These monkeys, after they were
born, were given no exposure
to faces, depending on the
monkey, for six to 24 months.
That's not quite completely
true.
Because at their birth,
they saw some faces.
So they couldn't start this
experiment at the
first moment of birth.
But as soon as they could from
birth, for six to 24 months.
So when they were being fed,
this is what they saw.
They were given an interesting
environment
to see lots of stuff.
And they would live in
something like this.
So they could not see
another monkey.
They could not see a human.
They never saw a face
except for the
first moments of birth.
Before they saw any living face
on a monkey or a human,
they would do these kinds of
experiments that you just
heard with infants.
And they would show that these
monkeys would preferentially
look at faces, both human
faces and monkeys.
And they had no preference
between them.
They would always go for a face
compared to an object, a
monkey face or a human face.
And they could do these kinds
of discrimination.
The first moment before they had
ever-- except for whatever
happens right a birth--
seen one.
So they never practiced
on anything.
Because they had not been
allowed to see a face.
But the first moment before they
saw any living face, they
already had this preference for
faces for both humans and
monkeys, as if it's in our genes
to be drawn to faces.
And what the mechanism is, the
top-heavy, something else, we
don't quite know.
But it's in our brain
to go for faces.
They're so important for us.
Then some monkeys hung
around people.
And some monkeys hung
around monkeys.
And what happened is really
quite striking.
They got better at the species
they hung around.
So if you did these kinds of
tests, the monkeys who hung
around monkeys got better
and better at monkeys.
And the monkeys that hung around
people got better and
better at people.
So what does that mean?
That means it looks like there's
a genetic preparation.
The first face that they see
with the slight asterisk of
the moment of birth, they are
already preferring faces.
The very first one they see,
even though they've gone six
months to two years without
seeing any face at all.
And then they get better
selectively on the species
they're exposed to.
So there's a genetic preparation
and then kind of a
sensitive period where you build
up a representation of
the species that you're
living with.
So let me slide there for
a moment to now writing.
As long as there's been mammals,
as long as there's
been people, we've been born to
things around us with faces
and interacted with people
who have faces.
So that's deep in our
evolutionary history.
Not deep in our evolutionary
history
is writing and reading.
The first visual language
of any kind is
about 4,000 years ago.
Not until the Gutenberg
Bible--
and that's about
600 years ago--
did large numbers
of people read.
So unlike faces and objects
which have been around
forever, not only for us, but
for other species, writing and
reading have been around only
for a few hundred years.
Our brains are not evolved
to be reading brains.
It's just an unbelievably
powerful cultural invention.
And people can read fast.
A typical reader can do this.
This is kind of amazing.
Most of us know somewhere
between
50,000 and 100,000 words.
We don't know all
of them well.
We can't spell all of
them correctly.
But we kind of can get
them if we see them.
And if we show you one word in
50,000ths of a second, you can
recognize which word you saw.
It's kind of amazing.
People read about 200 to 250
words per minute, a typical
reader cruising along when
they're focused.
These things can be measured
relatively simply.
Here's one that's a
little trickier.
But let me tell you.
Again, it shows you how
experiments can tell us
something we could not have
guessed without the
experiment, about how you read
every moment you've read
throughout your life.
So I'm going to tell you now
that you read about 12
letters at a time.
And then you move your eyes.
Whatever you're reading, a book,
on the computer, you'll
read about 12 letters.
That's where you're fixated.
Those will only be visible to
you, and then you'll move your
eyes to get the next set of
letters you need to read.
Now you go, no.
There's text there.
I'll give you, I move my eyes.
But what's really happening, let
me show you how blind you
are to everything but 12
letters at a time.
So here's the experiment
from McConkie & Raynor.
And many people have
found this since.
They tracked people's
eye movements.
You can have a machine that
tracks where your eyes are
fixated, where you're looking.
Every time you moved, what they
did is they took the text
that was written across a
monitor, they kept about 12
letters where you're looking.
And they made everything else
on the monitor x's.
You don't know this.
You're just reading.
So you're reading "people of."
This is where your eyes are.
The computer makes everything
else an x.
You move your eyes.
Now this becomes x's.
And these are x's.
You move your eye.
These become x's.
You move your eyes.
These become x's.
Does hat make sense?
Every time you move, where you
land, they give you the words
and letters.
But everything to the left
and right are all x's.
And the astounding thing is
nobody ever says hey, why are
there all the x's.
Because when you're reading,
unbeknownst to you, you only
see with good acuity 12
letters at a time.
And everything else, you barely
notice it's there.
You notice something is there.
If there's nothing there,
you would notice it.
But your mind is not really
seeing it at all.
And so people have tried
to represent this.
This, when you read, is
something like this.
Where you look, in your fovea,
or your high acuity, you see
about 12 letters.
Everything else is like this.
And that's why if I flip it to
x's, you don't even notice.
Because it's all pretty
crummy how you see it.
You notice something is there.
But it's pretty crummy.
You can say, I don't
believe it.
But people have done
this experiment
over and over again.
And when they flip everything
to x's to the left and right
of about 12 letters that you're
looking at, people just
don't know.
Because they don't really see
it as they read anymore.
Does that make sense?
12 letters at a time.
So again, we're trying to
understand some of these
things in regards to
difficulties people have.
So it turns out there's a part
of the brain that's also
involved in reading where, if
you damage, you get what's
called word blindness.
So these are adults
who are good
readers, no problem reading.
They get a stroke Hts left
visual cortex around here.
The most famous original case,
in 1887, all of a sudden one
day after a headache, this
man was unable to read.
His vision was otherwise
perfectly good.
He could hear words
and speak words.
He could see numbers.
He could write down words.
His writing was kind of
slow and laborious.
It wasn't typical writing.
But then you could show him a
few moments later what he had
written, and he would not be
able to read it aloud.
So here's a pathway where stuff
out there in the world
in vision meets how we read.
Amazing.
Now it turns out, just like
there's a spot in your brain
that's the first moment where
something you see is a face.
There's a part that's shown here
in red that's near that.
It's bigger in the left
hemisphere, the language
hemisphere.
It's pretty specific relatively
specific for words
compared to other things.
And so we end up with a
picture like this with
relatively specific areas in the
back of our brain that are
highly specialized for
recognizing where things are.
I didn't talk too
much about that.
But there's that area, faces,
words, and objects.
And if you have damage to any
of these pathways, for
whatever reason, the rest of
our brain can't compensate.
And it's all a big mystery, who
am I looking at, what word
am I looking at, what
object do I see?
Now, you might imagine that
for things like faces or
locations, we've had
evolutionary pressure for
forever to be good at that.
Where are we?
Who are we with?
Whereas things like words, or
nonsense words, and letters,
or chairs--
which are a recent cultural
invention--
our brains are not genetically
predisposed to those specific
categories.
So there's a very clever study
from Ted Polk in Michigan.
So we took twins.
And we'll talk more
about this.
But the way people try to get
at until we know the real
genes involved in things,
they'll compare twins who are
identical twins with the
identical genes and twins
which are so-called fraternal
twins who are born to the same
family but don't have
the identical genes.
And to the extent the identical
twins are more
similar to each other than the
fraternal twins, that's a
suggestion there's genetic
influences on whatever you're
looking at.
So what they did is they had
these people look at faces,
places, letter strings,
and chairs.
And they calculated how similar
was one twin to
another, either identically
genetic or not.
And what they found was that for
the faces and the places,
there was much more similar,
significantly more similarly
between identical twins
than fraternal twins.
That's the genetic
predisposition, in some way,
of how you will see a face
or know where you are.
If they compare reading
nonsense words, letter
strings, or chairs, the
two kinds of twins
were just the same.
It's as if there's no genetic
predisposition in you to know
where in your brain
you're going to
process words or chairs.
But that makes sense.
Because a couple thousand years
ago there were no words.
And a few more thousand
years than that,
there were no chairs.
So that's we don't have
the genes for recent
inventions in the world.
But our brain is brilliant at
becoming good at things like
reading as we invent them.
For the last part of the talk,
I want to talk about face
recognition.
So all of us know that when
we learn to read it was
a pretty big deal.
It was a while ago.
If you are a typical reader,
you're passionate.
If you're a struggling
reader, that can be
a persistent problem.
But you got through it,
and you're a reader.
None of us went to third grade
and said, today is the day
that we study faces.
And your parents are going, I
hope you're going at faces.
Because we really want you
to go to MIT someday.
This is the moment to get
ready for the face SAT.
But what I'm going to show you
is that in fact, through
experience, you're educated
for faces.
And there's some social
consequences for the faces
you're not educated
on, on average.
So let's talk about that.
So one way we see faces is we
see faces that are right-side
up, overwhelmingly.
So I'm going to show you
this upside down face.
I'm going to reverse it.
And that's what it is.
That's gruesome, right?
But can you tell that
when that turns,
it's going to be this?
So the way that we interpret
the weirdness of face
inversion, the fact that
we process upside
down faces so badly--
we don't have any hint of
what's really there--
it's because we didn't
practice on them.
It's as if I gave you a test in
a language that you never
spoke or read.
Well you can do badly.
So that shows you that
faces, it's a
so experienced dependent.
It's because you see upright
faces you get
good at upright faces.
All we have to do is turn
it upside down.
And all the knowledge and skill
you have, it's as if I
tested you in a different
language.
It's that specific.
Here's another example, side by
side, looks pretty similar.
But that's what you're
really seeing.
It's unbelievable.
Turn your head to believe me
in case you're suspicious.
This is legit.
We're so bad at upside down
faces because we don't
practice on them.
So what we are good at in faces
is so much dependent on
what we practice.
You may recognize this
person or not.
These are less dramatic.
People don't become as good
as they get at faces
until about age 16.
We don't consciously
practice it.
But the social experience
we have is practicing,
practicing, practicing how
you perceive a face.
One fun study from a Susan Carey
now at Harvard is she
took dog show judges.
Now, I don't know too much
about dog shows.
Some of you might
know something.
But a little bit of what
I know is this.
Sort of like in sports, you have
judges who work their way
up a ladder of experience
and reputation.
So in sports things, you
have the local judges.
And the really good ones
become the ones
for the bigger leagues.
And the big ones get to go to
the Super Bowl and World
Series who are really skilled
and thought to be excellent.
Dog show judges, similarly,
start locally.
The ones who seem pretty good
and persistent at it then
become the state judge show.
And then they go to the
big one in New York.
And so they did these face
inversion experiments on dog
show judges, people who were
just beginning to be a dog
show judge, people who have done
it for a while, people
who've done it for
a lot of years.
And they asked, when do you
get so much better at a
right-side up dog face than
an upside down dog face?
Now, most people are about
the same to start with.
Because we're not that
good at dog faces.
You might know a dog or two.
But you don't know hundreds
of dollars.
It took eight years for dog show
judges-- and they were
dog enthusiasts for many
years before they
became a dog show judge--
eight years of seeing many,
many dogs at dog show
competitions to develop the
upright face expertise that we
all have for faces as adults.
So for an adult, you have to
practice eight years to get
this kind of expertise.
You can't just do
it by cramming.
It's practice, practice,
practice in the most brutal
fundamental sense.
Now I'll say one last thing
about this then
go to the last topic.
The other thing is that we
understand also-- and we've
mentioned this before, but I'll
say it one more time--
that imagination and perception
use the same neural
territory in your mind.
So here's a study from Nancy
Kanwisher again.
Here's a part of the brain that
responds to faces, seeing
a face, seeing a house, seeing
a face, seeing a house.
Now, imagining a face, imagining
a house, imagining a
face, imagining a house.
So seeing one drives the
brain more strongly
than imagining it.
But when you imagine a face, you
seem to use the same brain
network as when you see it.
It's just not as vivid
and powerful.
So perception is the stuff
literally in your mind of
imagination.
You can imagine things, because
you've seen them
before, literally in
your brain It's the
same part of the brain.
So the last topic I want to talk
about is a sensitive and
difficult one.
So I'm going to do
it right, I hope.
But it's one that's a
practical one, and a
consequence, we believe, of the
fact that you're good at
faces that you practice.
So we're going to talk about
in these studies people
perceiving faces of European
Americans, or white Americans,
or African Americans.
And there's a huge amount
of research
that shows the following.
That whatever racial group you
see a lot of, you're pretty
good at remembering
those faces.
At whatever group you see
less, you're far worse.
We interpret this as a
consequence of the practice
that you have.
But social psychologists worry
it has a second consequence.
Let me tell you the
practice story.
So we did a study.
This is from us.
But it's very similar to other
people in terms of the
conclusion.
There's literally like 1,000
of these studies that show
that people are superior at
recognizing in an experiment
faces from their own group
than from other groups.
And here, an experiment that
was done with Stanford
students, a look in their mind
and then in their brain.
So these are Stanford students
just some years ago, maybe a
lot like you in many ways.
They saw some faces, and then
they got a memory test.
This is their performance
on the memory test.
So we had both European American
and African American
faces that they viewed.
And the participants in the
research were both African
American and European
American.
OK so there were white faces,
white subjects, black faces,
black subjects.
And what you can see is this.
The higher the bar, the
better the memory.
In both groups, they're better
in performance at remembering
faces from their own group.
But there's more to
it than that.
If you look at these bars, these
are the memory for the
white faces.
And it's about the same
in the two groups.
And look at the big
difference for the
African American faces.
So two things are
happening here.
One of them is there's superior
memory from faces
from your own group.
And the second story is that for
what we believed, and from
other research as
well, is this.
If you're a minority group,
you're still pretty good at
the majority faces.
If you're a majority group,
you're not so good at the
minority faces.
So these are European American
Stanford students.
And look how a miserable their
memory is for these African
American faces.
This is a difficult topic for
us, in part, because race is a
different topic for
good reasons.
But social psychologists worry
that the lack of practice that
many of us have on other groups
growing up at home, in
our community, and schools--
and it varies for people,
but on average--
makes us less able to
individuate in our memory one
person from another
in other groups.
And now this is not about
racial attitudes.
This is simple, objective
recognition of faces.
But it could certainly support
consideration of other groups
as if they were all the same.
Because they look
all the same.
I remember I had an
African American
colleague at Stanford.
And he was a dean.
And he went to China with a
Nobel laureate who is now the
Secretary of Energy
in the Obama
administration, Steve Chu.
And, of course, Nobel laureates
are a pretty big.
So this dean went to this Nobel
laureate all the time.
We're meeting Stanford donors
and other things.
He said they got on the plane.
They went to China,
the two of them.
And he went into a reception.
And he knew Steve Chu
was in there.
The African American dean said,
I could not pick him out
for my life.
When I saw him now, not with
other people I know, but with
a 500 other Chinese people
in a large reception.
So it's not about bad attitudes
in this case.
It's just literally the
experience you have.
And in the brain, this part of
this FFA, responds more to
groups from your own--
on average--
from your own racial group than
the other racial group.
And we think that's promoting
the ease with which to
identify individuals in your
group and the difficulty with
which you can identify I
individuals in another group.
And so we have strong reason
to think that this is all
about this particular phenomenon
about your
experience.
So let me tell you why.
One thing is we know that this
is not present at birth.
People have done these kinds of
experiments with infants.
These racial biases in what
kinds of faces we can remember
are not present at birth.
So they're not in our genes.
They're from our experience.
But they are present
by three months.
But by then you've seen a lot
of people in your family.
And the kind of experiment
that's very telling for this
is a study where there
were Korean children.
They were three to
nine years old.
They were adopted by European
Caucasian families, so, in the
sense, a cross-racial
adoption.
And then they tested their
memory for faces.
And for these Korean children
adopted by European Caucasian
families, they had better
memory for the Caucasian
faces, because that's who they
saw around them all the time.
And they were just like their
French peers who also saw
Caucasian faces all the time.
And the opposite of the findings
that you've got with
Korean children in
South Korea.
The inversion one is kind
of funny, amazing.
The fact that we can struggle
to individuate in memory one
African American from another,
or one Asian American from
another, or one Caucasian
American from another
depending on the environment
that we grew up in and were
exposed to, that could be
facilitating stereotyping and
lack of individuation of
people in other groups.
So the very last thing I want
to do-- and this is just a
couple minutes--
is talk about expression
in faces.
And I'll come back to
this in detail.
I just want to give you one last
example of recognition in
the amygdala and fear.
So we'll come back to this
in some detail later on.
But most researchers argue
there's about six basic
emotions that people around the
world transmit with their
facial expressions, happiness,
sadness, fear, anger,
surprise, and disgust.
You can show these pictures to
people around the world, and
they'll be, to some degree,
consensus about what they are,
universal expressions of
feelings transmitted by facial
expressions.
Now let's talk about
fear faces.
I'll just talk about
fear today.
And we'll talk about
the amygdala.
So we have one on the left and
one on the right, it's a very
small structure, almond shaped,
one inside each of the
temporal lobes right next
to the hippocampus.
So that's a view from the side
of where that's located, one
on the left and one
on the right.
And we know from a lot of animal
research-- and I'll
come back to this again--
the amygdala is essential
for learned
fear, for learned fear.
So here's an experiment
that shows you that.
One thing that mice know
is cats are bad news.
It's survival.
What they did in this
experiment is they
anesthetized the cat.
That's why the cat looks
glassy-eyed.
Obviously the experiment would
end too quickly for the mouse,
if the mouse had to come out
and play with the cat.
The experiment would be
brutal, and ugly,
and over too quickly.
But if the cat is breathing, the
cat's eyes are open, it's
anesthetized.
But it can't move.
Now a typical rat or mouse
will typically
still avoid the cat.
It's not worth figuring
out exactly what's
going on with the cat.
Are they faking me out?
I'll just go that way.
But this is not the mouse who
has the amygdala removed.
It's not fearful of what it
ought to be fearful of
anymore, even survival.
What we believe the most
important role of fear is not
fear of SATs or midterms.
Although we live
in that world.
It's fear of what injure
you and kill you.
Those are the things to learn.
Be fearful of what
can kill you.
Be fearful of what
can injure you.
Without the amygdala,
you lose that fear.
But here's the other-- this is
my last slide-- amazing thing.
There are humans who have
injuries selectively to the
amygdala, very few.
But there's a few.
And not only do they have some
problems with fear learning.
But they can't recognize
fearful
facial expressions anymore.
If they ask them to say, what
is this, without the word
present, they're very
bad at telling you
that's a fearful face.
They can recognize all the other
expressions pretty well
but not the fearful ones.
also
They're good of faces.
They're not prosopagnosia.
They're fine at faces.
They recognize their family.
But they can't recognize
fearful expressions
selectively.
This is actually a very good
drawing happy, sad, surprised,
disgusted, angry.
When she's asked to draw a
fearful facial expression,
this patient draws this,
a baby being afraid.
She understands the concept.
But it's not only that she
can't recognize it.
She can't imagine what a fearful
face looks like.
And we saw this over
and over again.
And there's one last
message in this.
Somehow our knowledge about
what a fearful face looks
like, we're not scared
of this.
You don't look at this
and go, oh my gosh.
I can't believe he showed
that in class.
I'll never sleep for 48 hours.
That's a social signal for
somebody telling you, whoa.
There's something terrible
happening here.
Look around you.
We better run.
It's a social signal.
And the part of your brain that
learns what can kill you
also is where the knowledge is
stored to recognize a social
signal about something that
could be very dangerous.
The same idea that we put our
knowledge in the parts of
their brain that act
upon the world.
