Discussion Board Philosophy In Humanites

FSCJ Center for eLearning | PHI2010-Mod4-Right_Brain_vs_Left_Brain

We began our journey into the human brain here on the campus of Dartmouth College in New

Hampshire. I’d come to meet one of the world’s leading brain scientists, Mike Gazzaniga, and a man

he’s worked with for over a decade. A man with two brains.

You’ve been working a long time with Dr. Gazzaniga.

14 or 15 years.

Doesn’t seem like that long, does it?

The collaboration began when Joe had surgery.

And you had this procedure to correct an epileptic problem, is that right?

Yes. Trying to stop the seizures. I was having seizures every day or so, or sometimes two or three a

day.

To control Joe’s epileptic seizures, a surgeon severed the connection between the two halves of his

brain. Cutting the corpus callosum like this prevented the spread of the electric storms that caused his

seizures. But it also prevented the left and right halves of his brain from communicating with each other.

In the years since the operation, Joe’s epilepsy has been under control. He now earns a living at an egg

farm, and in his everyday life, he’s largely unaffected by the fact that his left and his right brains work

independently.

Do you feel any different, when you think about something, than you did– differently from the way you

felt before the procedure?

I’ve just got a backup brain, that’s all.

[LAUGHTER]

That’s something everybody could use, right?

I found out how true that was right away, when I was asked to draw a different shape with each hand. In

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a brain like mine– roughly speaking, normal; at least, all in one piece– the left half of my brain controls

the right side of my body, while the right brain controls the left side.

Oh no!

But because the two halves are connected–

Nothing wrong with that.

–getting each hand to work independently isn’t easy.

Well, we’re seeing that the fact that Alan’s hemispheres are connected, and that the motor messages

from one are confusing the motor messages in the other–

I was just drawing an upside-down duck.

But when Joe is given the same task, his two hands operate as if controlled by two separate brains.

What’s happening is that each half of Joe’s brain is given a separate instruction. He’s asked to fix his

eyes on the cross in the center of the screen. Anything flashed to the right of the cross goes only to his

left hemisphere. Things to the left go to his right hemisphere. Because the two don’t communicate,

each does only what its half of the brain sees.

Wow. Look at that. It’s really like two different people doing the same–

That’s right.

–same task

That’s the idea.

OK, Joe, I want you to keep your hands up–

In an experiment that’s now a classic in brain research, Mike Gazzaniga over 30 years ago used a

similar setup to find out if the two halves of the brain are specialized to do different things.

Ship.

Joe is being flashed a word only to one half of his brain. Words flashed to the right–

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Storm.

–are seen only by his left brain. And Joe can report seeing those words just fine.

Piano.

Good.

But when a word is flashed to his right brain–

Didn’t see that.

OK. Joe, I’m going to ask you to–

But now watch what happens.

Draw that with your left hand.

You’re getting me lost.

Why don’t you try drawing another picture of it right over here if it’ll help you?

Oh, phone.

Oh, OK.

It’s almost as though somebody has given him a secret communication.

That’s right.

Now he knows that that is a telephone. Up until then he was blind to it.

Exactly.

When Gazzaniga first did this experiment, it instantly proved that the ability to speak resides almost

exclusively in the left hemisphere. Not until he sees what his right brain is drawing is Joe able to name

it.

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He said church.

After looking at the picture.

But he had to figure it out about as long as we did. That’s really interesting. It’s a picture here of

somebody communicating, almost with another person.

The communication is not occurring inside the head; it’s occurring out on the piece of paper.

Yeah.

Blob. I don’t know.

You want to draw a little bit more?

So far, Joe has been seeing only one word. Things get even stranger when he’s flashed two words,

each to only one half of his brain.

The right hemisphere saw “toad.”

And so his left hand draws a toad.

So there’s the toad.

Oh, it’s a toad. This time, I was able to guess what was coming. Will he put a little three-legged stool in

there later? Joe’s speaking left brain saw stool. Saying the word lets the hand that’s controlled by his

right brain in on the secret.

That’s great. That’s really interesting. And if he had seen that with the corpus callosum intact, he would

have drawn a toadstool. Not a toad and a stool.

Right. Exactly the point. I’ve been doing this for 35 years. And it gets me every time.

It must. It must.

This time, instead of naming the word, I want you to point to the word.

Again, Joe sees two words simultaneously. ‘Bell” goes to his non-speaking right brain, “music” to his

speaking left brain. When asked to point to a picture of what he saw, he chooses “bell.” But when asked 4

 

 

why–

Joe, why’d you pick that one?

Music.

Music?

And when asked to explain–

There was music, and bell. And those few minutes ago, the last time I heard any music, it was coming

from the bells out here, banging away.

You said the bells outside here?

So– a good enough answer to me.

What’s extraordinary is that Joe’s speaking left brain concocts a plausible story of why he pointed to

“bell,” even when some of the other pictures more obviously represent music. Gazzaniga believes this

determination to find cause and effect, this desire to explain, is the left hemisphere’s most marvelous

property.

One of the unique things of the human brain is this need to interpret why two events occur. What was

the antecedent of this? What caused this? And if you can imagine that a species like us, that has that

little chip in its brain that asks those questions, is going to survive rather well. Because it’s going to

figure out more about the nature of the world than a species that doesn’t have it.

OK Joe, I want you to keep your hand–

But as I was about to discover, the right brain has a very useful survival skill all its own.

What do you think will happen here?

For you, we’re doing a live experiment. Never done it before.

The experiment involves the 16th-century Italian painter Arcimboldo, who made faces out of fruit,

flowers, meat, even books. From other research, there’s reason to believe that the ability to recognize

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faces is located exclusively in the right hemisphere. So Mike wondered if Arcimboldo’s paintings would

look different to each of Joe’s two brains.

So will his left hemisphere say, I saw a potato; I didn’t see a face? And will his right hemisphere say, I

saw the face– and not comment on the fact it was made out of a potato?

You’re going to see a figure, followed by a choice of two words.

If this works, it’ll be terrific. But we’ll see. So there it is, live.

OK?

Mmhmm.

The first painting goes to the right hemisphere. And Joe points to face. The next painting goes to his left

brain. And this time he points to fruits.

Mike seemed pleased. Are you having a moment?

This is too good.

Again, to the right brain. And Joe sees it as a face.

Point it down.

But to the left brain–

A face made out of books.

Point it up.

Are you happy with what you’re seeing?

It’s unbelievable! He’s doing it. You see that?

Because they’re going so fast, shifting from left to right so fast, I can’t keep up with you. You’re used to

looking at this.

When you show him a face, in the right side, the left hemisphere, he’s focusing in on the elements that

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made up the face. When you show him the exact same picture in the left field, going to the right

hemisphere, he’s focusing on the face, and not the elements.

And not the elements. If you came down from another planet and you saw faces and vegetables, you

might not think there was much of a difference among them. But the brain seems to be made up in a

certain way, to say faces are very different from other objects.

That’s right.

And one side of the brain specializes in faces.

Exactly right. Exactly right. It is an adaptation that we have to detect upright faces. It’s a very important–

you can imagine in an evolutionary time that all of a sudden, you have the ability to detect quickly an

upright face. You want to read the expression on that face. You want to know if it’s friend or foe. You

want to have a set of questions about that face.

The right brain might be skilled at recognizing faces, but when it comes to what gives the human mind

its power– the ability to reason, to invent, to interpret the world around it– Mike Gazzaniga’s 30 years

of research has taught him which hemisphere he wouldn’t want to be without.

The old phrase here around our lab is, don’t leave home without you left hemisphere. That’s where the

action is.

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