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1. Introduction to Psychology: Foundations: This Is Your Brain
Poziom:
Temat: Społeczeństwo i nauki społeczne
Professor Paul Bloom:
We're going to begin the class
proper, Introduction to
Psychology, with a discussion
about the brain.
And, in particular,
I want to lead off the class
with an idea that the Nobel
Prize winning biologist,
Francis Crick,
described as "The Astonishing
Hypothesis."
And The Astonishing Hypothesis
is summarized like this.
As he writes,
The Astonishing Hypothesis is
that:
You, your joys and your
sorrows, your memories and your
ambitions, your sense of
personal identity and free will
are in fact no more than the
behavior of a vast assembly of
nerve cells and their associated
molecules.
As Lewis Carroll's Alice might
have phrased it,
"you're nothing but a pack of
neurons."
It is fair to describe this as
astonishing.
It is an odd and unnatural view
and I don't actually expect
people to believe it at first.
It's an open question whether
you'll believe it when this
class comes to an end,
but I'd be surprised if many of
you believe it now.
Most people don't.
Most people,
in fact, hold a different view.
Most people are dualists.
Now, dualism is a very
different doctrine.
It's a doctrine that can be
found in every religion and in
most philosophical systems
throughout history.
It was very explicit in Plato,
for instance.
But the most articulate and
well-known defender of dualism
is the philosopher Rene
Descartes,
and Rene Descartes explicitly
asked a question,
"Are humans merely physical
machines,
merely physical things?"
And he answered, "no."
He agreed that animals are
machines.
In fact, he called them "beast
machines" and said animals,
nonhuman animals are merely
robots, but people are
different.
There's a duality of people.
Like animals,
we possess physical material
bodies, but unlike animals,
what we are is not physical.
We are immaterial souls that
possess physical bodies,
that have physical bodies,
that reside in physical bodies,
that connect to physical
bodies.
So, this is known as dualism
because the claim is,
for humans at least,
there are two separate things;
there's our material bodies and
there's our immaterial minds.
Now, Descartes made two
arguments for dualism.
One argument involved
observations of a human action.
So, Descartes lived in a fairly
sophisticated time,
and his time did have robots.
These were not electrical
robots, of course.
They were robots powered by
hydraulics.
So, Descartes would walk around
the French Royal Gardens and the
French Royal Gardens were set up
like a seventeenth-century
Disneyland.
They had these characters that
would operate according to water
flow and so if you stepped on a
certain panel,
a swordsman would jump out with
a sword.
If you stepped somewhere else,
a bathing beauty would cover
herself up behind some bushes.
And Descartes said,
"Boy, these machines respond in
certain ways to certain actions
so machines can do certain
things and,
in fact," he says,
"our bodies work that way too.
If you tap somebody on the
knee, your leg will jump out.
Well, maybe that's what we are."
But Descartes said that can't
be because there are things that
humans do that no machine could
ever do.
Humans are not limited to
reflexive action.
Rather, humans are capable of
coordinated, creative,
spontaneous things.
We can use language,
for instance,
and sometimes my use of
language can be reflexive.
Somebody says, "How are you?"
And I say, "I am fine.
How are you?"
But sometimes I could say what
I choose to be,
"How are you?"
"Pretty damn good."
I can just choose.
And machines,
Descartes argued,
are incapable of that sort of
choice.
Hence, we are not mere machines.
The second argument is,
of course, quite famous and
this was the method.
This he came to using the
method of doubt.
So, he started asking himself
the question,
"What can I be sure of?"
And he said,
"Well, I believe there's a God,
but honestly,
I can't be sure there's a God.
I believe I live in a rich
country but maybe I've been
fooled."
He even said,
"I believe I have had friends
and family but maybe I am being
tricked.
Maybe an evil demon,
for instance,
has tricked me,
has deluded me into thinking I
have experiences that aren't
real."
And, of course,
the modern version of this is
The Matrix.
The idea of The Matrix is
explicitly built upon
Cartesian--Descartes' worries
about an evil demon.
Maybe everything you're now
experiencing is not real,
but rather is the product of
some other, perhaps malevolent,
creature.
Descartes, similarly,
could doubt he has a body.
In fact, he noticed that madmen
sometimes believe they have
extra limbs or they believe
they're of different sizes and
shapes than they really are and
Descartes said,
"How do I know I'm not crazy?
Crazy people don't think
they're crazy so the fact that I
don't think I'm crazy doesn't
mean I'm not crazy.
How do I know," Descartes said,
"I'm not dreaming right now?"
But there is one thing,
Descartes concluded,
that he cannot doubt,
and the answer is he cannot
doubt that he is himself
thinking.
That would be self-refuting.
And so, Descartes used the
method of doubt to say there's
something really different about
having a body that's always
uncertain from having a mind.
And he used this argument as a
way to support dualism,
as a way to support the idea
that bodies and minds are
separate.
And so he concluded,
"I knew that I was a substance,
the whole essence or nature of
which is to think,
and that for its existence,
there is no need of any place
nor does it depend on any
material thing.
That is to say,
the soul by which I am,
when I am, is entirely distinct
from body."
Now, I said before that this is
common sense and I want to
illustrate the common sense
nature of this in a few ways.
One thing is our dualism is
enmeshed in our language.
So, we have a certain mode of
talking about things that we own
or things that are close to us
– my arm,
my heart, my child,
my car – but we also extend
that to my body and my brain.
We talk about owning our brains
as if we're somehow separate
from them.
Our dualism shows up in
intuitions about personal
identity.
And what this means is that
common sense tells us that
somebody can be the same person
even if their body undergoes
radical and profound changes.
The best examples of this are
fictional.
So, we have no problem
understanding a movie where
somebody goes to sleep as a
teenager and wakes up as
Jennifer Garner,
as an older person.
Now, nobody says,
"Oh, that's a documentary.
I believe that thoroughly true"
but at the same time nobody,
no adult, no teenager,
no child ever leaves and says,
"I'm totally conceptually
confused."
Rather, we follow the story.
We can also follow stories
which involve more profound
transformations as when a man
dies and is reborn into the body
of a child.
Now, you might have different
views around--People around this
room will have different views
as to whether reincarnation
really exists,
but we can imagine it.
We could imagine a person dying
and then reemerging in another
body.
This is not Hollywood invention.
One of the great short stories
of the last century begins with
a sentence by Franz Kafka:
"As Gregor Samsa woke one
morning from uneasy dreams,
he found himself transformed in
his bed into a gigantic insect."
And again, Kafka invites us to
imagine waking up into a body of
a cockroach and we can.
This is also not modern.
Hundreds of years before the
birth of Christ,
Homer described the fate of the
companions of Odysseus who were
transformed by a witch into
pigs.
Actually, that's not quite
right.
She didn't turn them into pigs.
She did something worse.
She stuck them in the bodies of
pigs.
They had the head and voice and
bristles and body of swine but
their minds remained unchanged
as before, so they were penned
there weeping.
And we are invited to imagine
the fate of again finding
ourselves in the bodies of other
creatures and,
if you can imagine this,
this is because you are
imagining what you are as
separate from the body that you
reside in.
We allow for the notion that
many people can occupy one body.
This is a mainstay of some
slapstick humor including the
classic movie,
All of Me--Steve Martin
and Lily Tomlin – highly
recommended.
But many people think this sort
of thing really happens.
One analysis of multiple
personality disorder is that you
have many people inside a single
body fighting it out for
control.
Now, we will discuss multiple
personality disorder towards the
end of the semester and it turns
out things are a good deal more
complicated than this,
but still my point isn't about
how it really is but how we
think about it.
Common sense tells us you could
have more than one person inside
a single body.
This shows up in a different
context involving exorcisms
where many belief systems allow
for the idea that people's
behavior,
particularly their evil or
irrational behavior,
could be because something else
has taken over their bodies.
Finally, most people around the
world, all religions and most
people in most countries at most
times,
believe that people can survive
the destruction of their bodies.
Now, cultures differ according
to the fate of the body.
Some cultures have the body
going to--sorry--the fate of the
soul.
Some cultures have you going to
Heaven or descending to Hell.
Others have you occupying
another body.
Still, others have you
occupying an amorphous spirit
world.
But what they share is the idea
that what you are is separable
from this physical thing you
carry around.
And the physical thing that you
carry around can be destroyed
while you live on.
These views are particularly
common in the United States.
In one survey done in Chicago a
few years ago,
people were asked their
religion and then were asked
what would happen to them when
they died.
Most people in the sample were
Christian and about 96% of
Christians said,
"When I die I'm going to go to
Heaven."
Some of the sample was Jewish.
Now, Judaism is actually a
religion with a less than clear
story about the afterlife.
Still, most of the subjects who
identified themselves as Jewish
said when they die they will go
to Heaven.
Some of the sampled denied
having any religion at all--said
they have no religion at all.
Still, when these people were
asked what would happen when
they would die,
most of them answered,
"I'm going to go to Heaven."
So, dualism is emmeshed.
A lot rests on it but,
as Crick points out;
the scientific consensus now is
that dualism is wrong.
There is no "you" separable or
separate from your body.
In particular,
there is no "you" separable
from your brain.
To put it the way cognitive
scientists and psychologists and
neuroscientists like to put it,
"the mind is what the brain
does."
The mind reflects the workings
of the brain just like
computation reflects the working
of a computer.
Now, why would you hold such an
outrageous view?
Why would you reject dualism in
favor of this alternative?
Well, a few reasons.
One reason is dualism has
always had its problems.
For one thing,
it's a profoundly unscientific
doctrine.
We want to know as curious
people how children learn
language, what we find
attractive or unattractive,
and what's the basis for mental
illness.
And dualism simply says,
"it's all nonphysical,
it's part of the ether," and
hence fails to explain it.
More specifically,
dualists like Descartes
struggle to explain how a
physical body connects to an
immaterial soul.
What's the conduit?
How could this connection be
made?
After all, Descartes knew full
well that there is such a
connection.
Your body obeys your commands.
If you bang your toe or stub
your toe you feel pain.
If you drink alcohol it affects
your reasoning,
but he could only wave his
hands as to how this physical
thing in the world could connect
to an immaterial mind.
Descartes, when he was alive,
was reasonable enough
concluding that physical objects
cannot do certain things.
He was reasonable enough in
concluding, for instance,
as he did, that there's no way
a merely physical object could
ever play a game of chess
because--and that such a
capacity is beyond the capacity
of the physical world and hence
you have to apply--you have to
extend the explanation to an
immaterial soul but now we
know--we have what scientists
call an existence proof.
We know physical objects can do
complicated and interesting
things.
We know, for instance,
machines can play chess.
We know machines can manipulate
symbols.
We know machines have limited
capacities to engage in
mathematical and logical
reasoning,
to recognize things,
to do various forms of
computations,
and this makes it at least
possible that we are such
machines.
So you can no longer say, "Look.
Physical things just can't do
that" because we know physical
things can do a lot and this
opens up the possibility that
humans are physical things,
in particular,
that humans are brains.
Finally, there is strong
evidence that the brain is
involved in mental life.
Somebody who hold a--held a
dualist view that said that what
we do and what we decide and
what we think and what we want
are all have nothing to do with
the physical world,
would be embarrassed by the
fact that the brain seems to
correspond in intricate and
elaborate ways to our mental
life.
Now, this has been known for a
long time.
Philosophers and psychologists
knew for a long time that
getting smacked in the head
could change your mental
faculties;
that diseases like syphilis
could make you deranged;
that chemicals like caffeine
and alcohol can affect how you
think.
But what's new is we can now in
different ways see the direct
effects of mental life.
Somebody with a severe and
profound loss of mental
faculties--the deficit will be
shown correspondingly in her
brain.
Studies using imaging
techniques like CAT scans,
PET, and fMRI,
illustrate that different parts
of the brain are active during
different parts of mental life.
For instance,
the difference between seeing
words, hearing words,
reading words and generating
words can correspond to
different aspects of what part
of your brain is active.
To some extent,
if we put you in an fMRI
scanner and observed what you're
doing in real time,
by looking at the activity
patterns in your brain we can
tell whether you are thinking
about music or thinking about
sex.
To some extent we can tell
whether you're solving a moral
dilemma versus something else.
And this is no surprise if what
we are is the workings of our
physical brains,
but it is extremely difficult
to explain if one is a dualist.
Now, so what you have is--the
scientific consensus is that all
of mental life including
consciousness and emotions and
choice and morality are the
products of brain activities.
So, you would expect that when
you rip open the skull and look
at the brain;
you'd see something glorious,
you'd see – I don't know –
a big, shiny thing with glass
tubes and blinding lights and
sparks and wonderful colors.
And actually though,
the brain is just disgusting.
It looks like an old meat loaf.
It's gray when you take it out
of the head.
It's called gray matter but
that's just because it's out of
the head.
Inside the head it's bright red
because it's pulsing with blood.
It doesn't even taste good.
Well, has anybody here ever
eaten brain?
It's good with cream sauce but
everything's good with cream
sauce.
So, the question is,
"How can something like this
give rise to us?"
And you have to have some
sympathy for Descartes.
There's another argument
Descartes could have made that's
a lot less subtle than the ones
he did make,
which is "That thing
responsible for free will and
love and consciousness?
Ridiculous."
What I want to do,
and what the goal of
neuroscience is,
is to make it less ridiculous,
to try to explain how the brain
works, how the brain can give
rise to thought,
and what I want to do today is
take a first stab at this
question but it's something
we'll continue to discuss
throughout the course as we talk
about different aspects of
mental life.
What I want to do though now is
provide a big picture.
So, what I want to do is start
off small, with the smallest
interesting part of the brain
and then get bigger and bigger
and bigger – talk about how
the small part of the brain,
the neurons,
the basic building blocks of
thought, combine to other mental
structures and into different
subparts of the brain and
finally to the whole thing.
So, one of the discoveries of
psychology is that the basic
unit of the brain appears to be
the neuron.
The neuron is a specific sort
of cell and the neuron has three
major parts, as you could see
illustrated here.
Neurons actually look quite
different from one another but
this is a typical one.
There are the dendrites –
these little tentacles here.
And the dendrites get signals
from other neurons.
Now, these signals can be
either excitatory,
which is that they raise the
likelihood the neuron will fire,
or inhibitory in that they
lower the likelihood that the
neuron will fire.
The cell body sums it up and
you could view it
arithmetically.
The excitatory signals are
pluses, the inhibitory ones are
minuses.
And then if you get a certain
number, plus 60 or something,
the neuron will fire and it
fires along the axon,
the thing to the right.
The axon is much longer than
the dendrites and,
in fact, some axons are many
feet long.
There's an axon leading from
your spinal cord to your big toe
for instance.
It is so shocking the lights go
out.
Surrounded--Surrounding--To
complete a mechanical metaphor
that would have led Descartes to
despair-- Thank you,
Koleen.
Surrounding the axon is a
myelin sheath,
which is actually just
insulation.
It helps the firing work
quicker.
So, here are some facts about
neurons.
There are a lot of them –
about one thousand billion of
them – and each neuron can be
connected to around thousands,
perhaps tens of thousands,
other neurons.
So, it's an extraordinarily
complicated computing device.
Neurons come in three flavors.
There are sensory neurons,
which take information from the
world so as you see me,
for instance,
there are neurons firing from
your retina sending signals to
your brain.
There are motor neurons.
If you decide to raise your
hand, those are motor neurons
telling the muscles what to do.
And there are interneurons
which connect the two.
And basically,
the interneurons do the
thinking.
They make the connection
between sensation and action.
It used to be believed,
and it's the sort of thing I
would--when I taught this course
many years ago I would lecture
on--that neurons do not grow
back once you lose them.
You never get them back.
This is actually not true.
There are parts of the brain in
which neurons can re-grow.
One interesting thing about
neurons is a neuron is like a
gun.
It either fires or it doesn't.
It's all or nothing.
If you squeeze the trigger of a
gun really hard and really fast,
it doesn't fire any faster or
harder than if you just squeezed
it gently.
Now, this seems to be strange.
How could neurons be all or
nothing when sensation is very
graded?
If somebody next to you pushed
on your hand--the degree of
pushing--you'd be able to notice
it.
It's not either pushing or not
pushing.
You can--Degrees of pushing,
degrees of heat,
degrees of brightness.
And the answer is,
although neurons are all or
nothing, there are ways to code
intensity.
So, one simple way to code
intensity is the number of
neurons firing;
the more neurons the more
intense.
Another way to increase
intensity is the frequency of
firing.
So, I'll just use those two.
The first one is the number of
neurons firing.
The second one is the frequency
of firing in that something is
more intense if it's "bang,
bang, bang, bang,
bang, bang" then "bang,
bang, bang" and these are two
ways through which neurons
encode intensity.
Now, neurons are connected and
they talk to one another and it
used to be thought they were
tied to one another like a
computer,
like you take wires and you
connect wires to each other,
you wrap them around and
connect them.
It turns out this isn't the
case.
It turns out that neurons
relate to one another chemically
in a kind of interesting way.
Between any neurons,
between the axon of one neuron
and the dendrite of another,
there's a tiny gap.
The gap could be about one
ten-thousandths of a millimeter
wide.
This infinitesimal gap--and
this gap is known as a
synapse--and what happens is
when a neuron fires,
an axon sends chemicals
shooting through the gap.
These chemicals are known as
neurotransmitters and they
affect the dendrites.
So, neurons communicate to one
another chemically.
These--Again,
the chemicals could excite the
other neuron (excitatory) bring
up the chances it will fire,
or inhibit the other neuron
(inhibitory).
Now, neurotransmitters become
interesting because a lot of
psychopharmacology,
both of the medical sort and
the recreational sort,
consists of fiddling with
neurotransmitters and so you
could see this through some
examples.
There are two sorts of ways you
could fiddle with
neurotransmitters,
and correspondingly two sorts
of drugs.
There are agonists.
And what an agonist does is
increases the effect of
neurotransmitters,
either by making more
neurotransmitters or stopping
the cleanup of
neurotransmitters,
or in some cases by faking a
neurotransmitter,
by mimicking its effects.
Then, there are antagonists
that slow down the amount of
neurotransmitters,
either because they destroy
neurotransmitters or they make
it hard to create more.
Or in some cases they go to the
dendrite of the neuron and they
kind of put a paste over it so
that the neurotransmitters can't
connect.
And it's through these clever
ways that neurons can affect
your mental life.
So, for instance,
there is a drug known as Curare
and Curare is an antagonist.
It's a very particular sort of
antagonist.
It blocks motor neurons from
affecting muscle fibers.
What this does then is it
paralyzes you because your motor
neurons--You send the command to
your arm to stand,
to lift up.
It doesn't work.
You send the command to your
leg to move.
It doesn't work.
The motor neurons are
deactivated and then,
because the way you breathe is
through motor neurons,
you then die.
There's alcohol.
Alcohol is inhibitory.
Now, this may be puzzling to
people.
It's mildly paradoxical because
you may be thinking,
"alcohol is not inhibitory.
On the contrary,
when I drink a lot of alcohol I
lose my inhibitions and become a
more fun person.
I become more aggressive and
more sexually vibrant and simply
more beautiful.
And so in what way is alcohol
inhibitory?"
Well, the answer is it inhibits
the inhibitory parts of your
brain.
So, you have parts of your
brain that are basically telling
you now, largely in the frontal
lobes, that are--"Okay.
Keep your pants on.
Don't hit me, buddy.
Don't use bad words."
Alcohol relaxes,
shuts down those parts of the
brain.
If you take enough alcohol,
it then goes down to inhibit
the excitatory parts of your
brain and then you fall on the
floor and pass out.
Amphetamines increase the
amount of arousal.
In particular,
they increase the amount of
norepinephrine,
a neurotransmitter that's
responsible for just general
arousal.
And so, amphetamines include
drugs like "speed" and "coke."
There are--Prozac works on
serotonin.
When we discuss clinical
psychology and depression we'll
learn the extent to which
neurotransmitter disorders are
implicated in certain disorders
like depression.
And one problem is that – for
depression – is that there's
too little of a neurotransmitter
known as serotonin.
Prozac makes serotonin more
prevalent and so in some extent
might help alleviate depression.
Parkinson's disease is a
disease involving destruction of
motor control and loss of motor
control, difficulty moving.
And one factor in Parkinson's
is too little of a
neurotransmitter known as
dopamine.
The drug L-DOPA increases the
supply of dopamine and so there
is something to alleviate,
at least temporarily,
the symptoms of Parkinson's.
So, you have neurons and
they're clustered together and
they fire and they communicate
to one another.
So, how does this all work to
give rise to creatures who could
do interesting things like talk
and think?
Well, again,
it used to be believed that the
brain is wired up like a
computer,
like a PC or a Mac or something
like that, but we know this
can't be true.
It can't be true because
there's two ways in which the
brain is better than a computer.
For one thing,
the brain is highly resistant
to damage.
If you have a laptop and I
persuade you to open it up for
me and I take the pliers and
kind of snip just about
anywhere,
your laptop will be destroyed
but the brain is actually more
resilient.
You can take a lot of brain
damage and still preserve some
mental functioning.
To some interesting sense,
there's some sort of damage
resistance built in to the brain
that allows different parts of
the brain to take over if some
parts are damaged.
A second consideration is the
brain is extremely fast.
Your computer works on wires
and electricity but your brain
uses tissue and tissue is
extremely slow.
The paradox then is how do you
create such a fast computer with
such slow stuff?
And you can't.
If the brain was wired up like
a personal computer,
it would take you four hours to
recognize a face but,
in fact, we could do things
extremely quickly.
So, the question then is how is
the brain wired up?
And the answer is,
unlike manys,
unlike commercially generated
computers, the brain works
through parallel processing,
massively parallel distributed
processing.
There's a whole lot of research
and this is research,
some of which takes place
outside psychology departments
and in engineering departments
and computer science
departments,
trying to figure out how a
computer can do the same things
brains can do.
And one way people do this is
they take a hint from nature and
they try to construct massively
distributed networks to do
aspects of reasoning.
So, there's a very simple
computational network.
That is interesting because it
kind of looks to some extent
like the way neurons look and
this is often known as neural
networks.
And people who study this often
claim to be studying neural
network modeling to try to build
smart machines by modeling them
after brains.
And in the last 20 years or so,
this has been a huge and
vibrant area of study where
people are trying to wire up
machines that can do brain-like
things from components that look
a lot like neurons and are wired
up together as neurons are.
One consideration in all of
this is that this is a very
young field and nobody knows how
to do it yet.
There is no machine yet that
can recognize faces or
understand sentences at the
level of a two-year-old human.
There is no machine yet that
can do just about anything
people can do in an interesting
way.
And this is,
in part, because the human
brain is wired up in an
extraordinarily more complicated
way than any sort of simple
neural network.
This is a sort of schematic
diagram – you're not
responsible for this – of
parts of the visual cortex,
and the thing to realize about
this is it's extraordinarily
simplified.
So, the brain is a complicated
system.
Now, so, we've talked a little
bit about the basic building
blocks of the brain – neurons.
We've then talked about how
neurons can communicate to one
another;
then, turned to how neurons are
wired up together.
Now let's talk a little bit
about different parts of the
brain.
Now, there's some things you
don't actually need your brain
to do.
The study of what you don't
need your brain to do has often
drawn upon this weird
methodology where--This was
actually done in France a lot
where they would decapitate
people and when--After they
decapitated people,
psychologists would rush to the
body of the headless person and
sort of just test out reflexes
and stuff like that.
It's kind of gruesome but we
know there are some things you
don't need your brain for.
You don't need your brain for
newborn sucking,
limb flexation in withdrawal
from pain.
Your limbs will pull back even
if your head is gone.
Erection of the penis can be
done without a brain.
Vomiting also is done without a
brain.
Oh.
I need a volunteer.
Very simple.
This will not involve any
of--excellent--any of the above.
Could you stand up just--Okay.
This is a new shirt so I want
to stay away.
Just--No.
This is--If you'll hold out
your hand and--one hand flat.
Excellent.
That's the textbook,
5th edition.
Now.
Perfect.
What you'll notice is--Thank
you very much.
What you'll notice is this hit
and this hand went back up.
This is something automatic,
instinctive,
and does not require your
brain.
So your brain isn't needed for
everything.
What does your brain do?
Well, some things that your
brain does involve very
low-level internal structures.
And these are called
subcortical structures because
they're below the cortex.
They're underneath the cortex.
So, for instance,
what we have here is a diagram
of the brain.
The way to read this diagram is
it's as if it were my brain and
I am facing this way.
My head gets cut in half down
here and then you could see the
brain.
So, this is the front over here.
That's the back.
Some key parts are illustrated
here.
The medulla,
for instance,
is responsible for heart rate
and respiration.
It's very deep within the brain
and if it gets damaged you
could--you are likely to die.
The cerebellum is responsible
for body balance and muscular
coordination.
And to give you,
again, a feeling for the
complexity of these systems,
the cerebellum contains
approximately 30 billion
neurons.
The hypothalamus is responsible
here for feeding,
hunger, thirst,
and to some extent sleep.
And here is the same brain
parts in close-up.
Now, all of these parts of the
brains are essential and many of
them are implicated in
interesting psychological
processes but where the action
is is the cortex.
Isn't this beautiful?
The cortex is the outer layer
and the outer layer is all
crumpled up.
Do you ever wonder why your
brain looks wrinkled?
That's because it's all
crumpled.
If you took out somebody's
cortex and flattened it out,
it would be two feet square,
sort of like a nice--like a
rug.
And the cortex is where all the
neat stuff takes place.
Fish don't have any of that,
so no offense to fish but
it's--fish don't have much of a
mental life.
Reptiles and birds have a
little bit about it--of it--and
primates have a lot and humans
have a real lot.
Eighty percent of the volume of
our brain, about,
is cortex.
And the cortex can be broken up
into different parts or lobes.
There is the--And,
again, this is facing in
profile forward.
There is the frontal lobe,
easy to remember.
This part in front,
the parietal lobe,
the occipital lobe,
and the temporal lobe.
And one theme we're going to
return to is--this is half the
brain.
This is, in fact,
the left half of the brain.
On the other half,
the right half,
everything's duplicated with
some slight and subtle
differences.
What's really weird--One really
weird finding about these lobes
is that they include topological
maps.
They include maps of your body.
There is a cartoon which
actually illustrates a classic
experiment by some physiologists
who for some reason had a dog's
brain opened up and started
shocking different parts of the
brain.
You could do brain surgery
while fully conscious because
the brain itself has no sense
organs to it.
And it turns out that the
dog--When they zapped part of
its brain, its leg would kick
up.
And it took Dr.
Penfield at McGill University
to do the same thing with
people.
So, they were doing some brain
surgery.
He had a little electrical
thing just on--I don't know how
he thought to do this.
He started zapping it and
"boom."
The person--Parts of their body
would move.
More than that,
when he zapped other parts of
the brain, people would claim to
see colors.
And he zapped other parts of
the brain;
people would claim to hear
sounds;
and other parts of the brain,
people would claim to
experience touch.
And through his research and
other research,
it was found that there are
maps in the brain of the body.
There is a map in the motor
part of the brain,
the motor cortex,
of the sort up on the left and
the sensory cortex of the sort
that you could see on the right
and if you--and you could tell
what's what by opening up the
brain and shocking different
parts and those parts would
correspond to the parts of the
body shown in the diagram there.
Now, two things to notice about
these maps.
The first is they're
topographical and what this
means is that if two parts of
the--two parts are close
together on the body,
they'll be close together on
the brain.
So, your tongue is closer to
your jaw than it is to your hip
in the body;
so too in both the motor cortex
and the somatosensory cortex.
Also, you'll notice that the
size of the body part
represented in the brain does
not correspond to the size of
the body part in the real world.
Rather, what determines the
size in the brain is the extent
to which either they have motor
command over it or sensory
control.
So, there's a whole lot of
sensory organs,
for instance,
focused along your tongue,
and that's why that's so big,
and an enormous amount on your
face but your shoulder isn't
even--doesn't even make it on
there because,
although your shoulder might be
bigger than your tongue,
there's not much going on.
In fact, if you draw a diagram
of a person, what their body is
corresponding to the amount of
somatosensory cortex,
you get something like that.
That's your sensory body.
Now, so, you have these maps in
your head but the thing to
realize is--And these maps are
part of your cortex,
but the things to realize is
that's an important part of what
goes on in your brain but less
than one quarter of the cortex
contains these maps or
projection areas.
The rest is involved in
language and reasoning and moral
thought and so on.
And, in fact,
the proportion as you go from
rat, cat, and monkey,
humans--less and less of it is
devoted to projection and there
is more and more to other
things.
So, how do we figure out what
the other parts of the brain do?
Well, there's all sorts of
methods.
Typically, these are recent
imaging methods like CAT scan
and PET scan and fMRI which,
as I said before,
show parts of your brain at
work.
If you want to know which part
of your brain is responsible for
language, you could put somebody
into a scanner and have them
exposed to language or do a
linguistic task or talk or
something and then see what
parts of their brain are active.
Another way to explore what the
brain does is to consider what
happens to people when very bad
things happen to their brain.
And these bad things could
happen through lesions,
through tumors,
through strokes,
through injury.
For the most part,
neuropsychologists don't like
helmet laws.
Neuropsychologists love when
motorcyclists drive without
helmets because through their
horrible accidents we gain great
insights into how the brain
works.
And the logic is if you find
somebody--Crudely,
if you find somebody with
damage to this part of the brain
right here and that person can't
recognize faces for instance,
there's some reason to believe
that this part of the brain is
related to face recognition.
And so, from the study of brain
damage and the study of--we can
gain some understanding of what
different parts of the brain do.
And so, people study brain
damages--brain damage that
implicates motor control such as
apraxia.
And what's interesting about
apraxia is it's not paralysis.
Somebody with apraxia can move,
do simple movements just fine
but they can't coordinate their
movements.
They can't do something like
wave goodbye or light a
cigarette.
There is agnosia and agnosia is
a disorder which isn't blindness
because the person could still
see perfectly well.
Their eyes are intact but
rather what happens in agnosia
is they lose the ability to
recognize certain things.
Sometimes this is described as
psychic blindness.
And so, they may get visual
agnosia and lose the ability to
recognize objects.
They may get prosopagnosia and
lose the ability to recognize
faces.
There are disorders of sensory
neglect, some famous disorders.
Again, it's not paralysis,
it's not blindness,
but due to certain parts of
your--of damaged parts of your
brain,
you might lose,
for instance,
the idea that there's a left
side of your body or a left side
of the world.
And these cases are so
interesting I want to devote
some chunk to a class in the
next few weeks to discussing
them.
There are disorders of language
like aphasia.
The classic case was discovered
by Paul Broca in 1861.
A patient who had damage to
part of his brain and can only
say one word,
"tan,"
and the person would say,
"tan, tan, tan,
tan," and everything else was
gone.
There's other disorders of
language such as receptive
aphasia where the person could
speak very fluently but the
words don't make any sense and
they can't understand anybody
else.
Other disorders that we'll
discuss later on include
acquired psychopathy,
where damage to parts of your
brain,
particularly related to the
frontal lobes,
rob you of the ability to tell
right from wrong.
The final--I want to end--We're
talking about neurons,
connection between neurons,
how neurons are wired up,
the parts of the brain,
what the different parts do.
I want to end by talking about
the two halves of the brain and
ask the question,
"How many minds do you have?"
Now, if you look at the
brain--If you took the brain out
and held it up,
it would look pretty
symmetrical, but it actually is
not.
There are actual differences
between the right hemisphere and
the left hemisphere.
How many people here are
right-handed?
How many people here are
left-handed?
How many people here are sort
of complicated,
ambidextrous,
don't know, "bit of the right,
bit of left" people?
Okay.
Those of you who are
right-handed,
which comprises about nine out
of ten people,
have language in your left
hemisphere.
And, in fact,
we're going to be talking about
right-handed people for the most
part, making generalizations in
what I'll talk about now.
Those of you who are
left-handed are more
complicated.
Some of you have language in
your right hemisphere,
some in your left hemisphere,
some God knows where.
It's complicated.
Now, the idea is that some
things are duplicated.
So, if you were to lose half
your brain, the other half can
actually do a lot but some
things are more prevalent and
more powerful in one part of the
brain than the other.
And I want to show you a brief
film clip from "Scientific
American" that illustrates the
differences between the
hemispheres,
but before doing that,
I want to provide some
introductory facts.
Some functions are lateralized.
So, typically,
language in the left.
Again, this is a right-handed
centric thing but if you're
right-handed – language on the
left, math and music on the
right.
There is a crossover and this
is important when we think about
the studies that will follow but
the crossover is that everything
you see in the left visual field
goes to the right side of your
brain;
everything in the right visual
field goes to the left side of
the brain, and similarly,
there's a crossover in action.
So, your right hemisphere
controls the left side of the
body.
Your left hemisphere controls
the right side of the body.
Now, finally,
the two halves are connected.
They're connected by this huge
web called the corpus callosum.
And I'm just going to skip this
because the movie illustration
will go through some of this.
This illustrates certain themes
that are discussed in detail in
the Gray book,
concerning the lateralization
of different parts of different
mental capacities,
some in the left hemisphere,
some in the right hemisphere.
But it also serves as a useful
methodological development,
which is a nice illustration as
to how looking at people who are
incredibly unusual,
such as this man who had his
brain bisected so his left
hemisphere and his right
hemisphere don't communicate
with one another--how looking at
such people,
such extreme cases,
can provide us with some
understanding of how we normally
do things.
And this, again,
is a theme we'll return to
throughout the course.
This is generally the general
introduction of the brain that I
wanted to provide,
giving the framework for what
I'll be talking about later on
throughout the course so that I
might later on make reference to
neurons or neurotransmitters or
the cortex or the left
hemisphere and you'll sort of
have the background to
understand what I'm talking
about.
But I want to end this first
real class with a bit of
humility as to what
psychologists know and don't
know.
So, the idea behind a lot of
psychology – particularly a
lot of neuroscience and
cognitive psychology – is to
treat the mind as an information
processor,
as an elaborate computer.
And so, we study different
problems like recognizing faces
or language or motor control or
logic.
The strategy then often is to
figure out how,
what sort of program can solve
these problems and then we go on
to ask,
"How could this program be
instantiated in the physical
brain?"
So, we would solve--We study
people much as we'd study a
computer from an alien planet or
something.
And I think--This strategy is
one I'm very enthusiastic about
but there still remains what's
sometimes called the "hard
problem" of consciousness and
this involves subjective
experience.
What's it like?
So, my computer can play chess.
My computer can recognize
numbers.
It can do math.
And maybe it does it kind of
the same way that I do it but my
computer doesn't have feelings
in the same sense.
These are two classic
illustrations.
This is from a very old "Star
Trek" episode.
It illustrates angst.
I think a starship's about to
go into the sun or something.
And that's my older kid,
Max, who's happy.
And so the question is,
"How does a thing like that
give rise to consciousness and
subjective experience?"
And this is a deep puzzle.
And although some psychologists
and philosophers think they've
solved it, most of us are a lot
more skeptical.
Most of us think we have so far
to go before we can answer
questions like Huxley's
question.
Huxley points out,
"How it is that anything so
remarkable as a state of
consciousness comes about as a
result of irritating nervous
tissue,
is just as unaccountable as the
appearance of the Djinn…" –
of the genie – "…when
Aladdin rubs his lamp."
It seems like magic that a
fleshy lump of gray,
disgusting meat can give rise
to these feelings.
The second bit of humility
we'll end the class on is I am
presenting here,
and I'll be presenting
throughout this semester,
what you can call a mechanistic
conception of mental life.
I'm not going to be talking
about how beautiful it is and
how wonderful it is and how
mysterious it is.
Rather, I'm going to be trying
to explain it.
I'm going to be trying to
explain fundamental aspects of
ourselves including questions
like how do we make decisions,
why do we love our children,
what happens when we fall in
love, and so on.
Now, you might find this sort
of project in the end to be
repellant.
You might worry about how this,
well, this meshes with humanist
values.
For instance,
when we deal with one another
in a legal and a moral setting,
we think in terms of free will
and responsibility.
If we're driving and you cut me
off, you chose to do that.
It reflects badly on you.
If you save a life at risk to
your own, you're--you deserve
praise.
You did something wonderful.
It might be hard to mesh this
with the conception in which all
actions are the result of
neurochemical physical
processes.
It might also be hard to mesh a
notion such as the purported
intrinsic value of people.
And finally,
it might be hard to mesh the
mechanistic notion of the mind
with the idea that people have
spiritual value.
Faced with this tension,
there are three possibilities.
You might choose to reject the
scientific conception of the
mind.
Many people do.
You may choose to embrace
dualism, reject the idea that
the brain is responsible for
mental life, and reject the
promise of a scientific
psychology.
Alternatively,
you might choose to embrace the
scientific worldview and reject
all these humanist values.
And there are some philosophers
and psychologists who do just
that, who claim that free will
and responsibility and spiritual
value and intrinsic value are
all illusions;
they're pre-scientific notions
that get washed away in modern
science or you could try to
reconcile them.
You could try to figure out how
to mesh your scientific view of
the mind with these humanist
values you might want to
preserve.
And this is an issue which
we're going to return to
throughout the course.
Okay.
I'll see you on Wednesday.
