跟读练习: 2. Foundations: This Is Your Brain - 通过视频学习英语口语
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Dr. John L.
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We're going to begin the class proper, Introduction to Psychology, with a discussion about the brain.
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And in particular, I want to lead off the class with an idea that the Nobel Prize the prize -winning biologist,
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Francis Crick, described as the astonishing hypothesis.
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And the astonishing hypothesis is summarized like this.
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As he writes, the astonishing hypothesis is that you, your joys and your sorrows, your memories and your ambitions, your sense of personal identity
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and free will are in fact no more than the behavior of a vast assembly of nerve cells and their associated molecules.
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As Lewis Carroll's Alice might you might have phrased it, you're nothing but a pack of neurons.
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It is fair to describe this as astonishing.
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It is an odd and unnatural view.
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And I don't actually expect people to believe it at first.
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It's an open question whether you'll believe it when this class comes to an end.
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But I'd be surprised if many of you believe it now.
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Most people don't.
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Most people, in fact, hold a different view history.
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Most people are dualists.
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Now, dualism is a very different doctrine.
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It's a doctrine that can be found in every religion and in most philosophical systems throughout history.
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It was very explicit in Plato, for instance.
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But the most articulate and well -known defender of dualism is the philosopher René Descartes.
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And Rene Descartes explicitly asked a question,
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are humans merely physical machines, merely physical things?
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And he answered no. He agreed that animals are machines.
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In fact, he called them beast machines and said animals, non -human animals, are merely robots.
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But people are different.
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There's a duality of people.
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Like animals, we possess physical material bodies.
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But unlike animals, what we are is not physical.
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We are immaterial souls that possess physical bodies, that have physical bodies, that reside in physical bodies,
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that connect to physical bodies.
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So, this is known as dualism because the claim is, for humans at least, there are two separate things.
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There's our material bodies and there's our immaterial minds.
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Now, Descartes made two arguments for dualism.
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One argument involved observations about human action.
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So, Descartes lived in a fairly sophisticated time and his time did have robots.
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These were not electrical robots, of course.
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They were robots powered by hydraulics.
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So, Descartes would walk around the French royal gardens.
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And the French royal gardens were set up like a seventeenth -century Disneyland.
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They had these characters that would operate according to water flow.
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And so if you stepped on a certain panel, a swordsman would jump out with a sword.
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If you stepped somewhere else, a bathing beauty would cover herself up behind some bushes.
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And Descartes said, boy, these machines respond in certain ways to certain actions.
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So, machines can do certain things.
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In fact, he says our bodies work that way too.
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If you tap somebody on the knee your leg will jump out.
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Well, maybe that's all we are.
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But Descartes said that can't be because there are things that humans do that no machine could ever do.
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Humans are not limited to reflexive action.
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Rather, humans are capable of coordinated, creative, spontaneous things.
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We can use language, for instance.
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And sometimes my use of language can be reflexive.
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Somebody says, how are you?
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And I say, I am fine, how are you?
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But sometimes I could say what I choose to be.
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How are you?
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Pretty damn good.
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I could just choose.
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And machines, Descartes argued, are incapable of that sort of choice.
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Hence, we are not mere machines.
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The second argument is of course quite famous.
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And this he came to using the method of doubt.
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So, he started asking himself the question, what can I be sure of?
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And he said, well, I believe there's a God, but honestly, I can't be sure there's a God.
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I believe I live in a rich country, but maybe I've been fooled.
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He even said, I believe I have had friends and family, but maybe I am being tricked.
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Maybe an evil demon, for instance, has tricked me, has deluded me into thinking I have experiences that aren't real.
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And of course the modern version of this is the matrix.
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The idea that the matrix is explicitly built upon Cartesian Descartes' worries about an evil demon.
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Maybe everything you're now they're now experiencing is not real but rather is a product of some other perhaps malevolent creature.
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Descartes similarly could doubt he has a body.
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In fact, he noticed that mad men sometimes believe they have extra limbs
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or they believe they're of different sizes and shapes than they really are.
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And Descartes said, how do I know I'm not crazy?
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I mean, crazy people don't think they're crazy, so the fact I don't think I'm crazy doesn't mean I'm not crazy.
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He says, how do I know, Descartes said, I'm not dreaming right now.
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But there is one thing, Descartes concluded, that he cannot doubt.
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And the answer is he cannot doubt that he is himself thinking.
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That would be self -refuting.
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And so Descartes used the method of doubt to say, there's something really different about having a body.
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That's always uncertain from having a mind.
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And he used this argument as a way to support dualism, them as a way to support the idea that bodies and minds are separate.
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And so he concluded, I knew that I was a substance, a whole essence or nature of which is to think and
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that for its existence there is no need of any place nor does it depend on any material thing.
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That is to say the soul by which I am, what I am, is entirely distinct from body.
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Now, I said before that this is common sense
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and I want to illustrate the common sense nature of this in a few ways.
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One thing is our dualism is a mesh in our language.
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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.
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But we also extend that to my body and my brain.
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We talk about owning our brains as if we're somehow separate from them.
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Our dualism shows up in intuitions about personal identity.
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And what this means is that
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common sense tells us that somebody can be the same person even if their body undergoes radical and profound changes.
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The best examples of this are fictional.
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So we have no problem understanding a movie where where somebody goes to sleep as a teenager
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and wakes up as Jennifer Garner, as an older person.
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Now, nobody says, oh, that's a documentary.
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I believe that thoroughly true.
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But at the same time nobody, no adult, no teenager, no child ever leaves and says, I'm totally conceptually confused.
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Rather, we follow, we follow, we follow the story.
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We can also follow stories which involve more profound transformations as
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when a man dies and is reborn into the body of a child.
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Now, you might have different views around, people around this room will have different views as to whether reincarnation really exists.
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But we can imagine it.
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We can imagine a person dying and then re -emerging in another body.
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This is not Hollywood invention.
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One of the great short stories of the last century begins with a sentence by Franz Kafka.
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As Gregor Samsa awoke one morning from uneasy dreams, he found himself transformed in his bed into a gigantic insect.
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And again, Kafka invites us to imagine waking up into a body of a cockroach and we can.
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This is also not modern.
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Hundreds of years before the birth of Christ Homer described the
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fate of the companions of Odysseus who were transformed by a witch into pigs.
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Actually that's not quite right.
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Anyway, she didn't turn the men into pigs.
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She did something worse.
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She stuck them in the bodies of pigs.
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They had the head and voice and bristles and body of swine
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but their minds remained unchanged as before so they were penned there weeping.
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And we are invited to imagine the fate of, again, finding ourselves in the bodies of other creatures.
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And if you could imagine this, this is because you are imagining what you are as separate from the body that you reside in.
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We allow for the notion that many people can occupy one body.
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This is a mainstay of some slapstick humor, including the classic movie, All of Me, Steve Martin, Lily Tomlin, highly recommended.
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But many people think this sort of thing really happens.
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One analysis of multiple personality disorder.
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is that you have many people inside a single body fighting it out for control.
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Now, we will discuss multiple personalities sort of towards the end of the semester
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and it turns out things are a good deal more complicated than this.
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But still, my point isn't about how it really is but how we think about it.
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Common sense tells us you could have more than one person inside a single body.
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This shows up in a different context involving exorcisms, where many belief systems allow for the idea that people's behavior,
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particularly their evil or irrational behavior, could be because something else has taken over their bodies.
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Finally, most people around the world,
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all religions, and most people in most countries at most times believe that people can survive the destruction of their bodies.
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Now, cultures differ according to the fate of the body.
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Some cultures have the body going to, sorry, the fate of the soul.
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Some cultures have you going to heaven or descending to hell.
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Others have you occupy another body.
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Still others have you occupy an amorphous spirit world.
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But what they share is the idea
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that what you are is separable from this physical thing you carry around
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and the and the physical thing that you carry around can be destroyed while you live on.
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These views are particularly common in the United States.
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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.
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Most people in the sample were Christian and about 96 % of Christians said, when I die I'm going to go to heaven.
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Some of the sample was Jewish.
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Now, Judaism is actually a religion with a less than clear story about the afterlife.
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Still, most of the subjects who identified themselves as Jewish said when they die they will go to heaven.
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Some of the sample denied having any religion at all, said they have no religion at all.
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Still, when these people were asked what would happen when they would die, most of them answered, I'm going to go to heaven.
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So, dualism is a mesh.
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A lot rests on it.
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But as Crick points out, the scientific consensus now is that dualism is wrong.
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There is no you separable or separate from your body.
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In particular, there is no you separable from your brain.
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To put it the way cognitive scientists and psychologists and neuroscientists like to put it, the mind is what the brain does.
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The mind reflects the workings of the brain just like computation reflects the working of a computer.
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Now, why would you hold such an outrageous view?
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Why would you reject dualism in favor of this alternative?
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Well, a few reasons.
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One reason is dualism has always had its problems.
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For one thing, I think it's a profoundly unscientific doctrine.
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We want to know as curious people how children learn language, what we find attractive or unattractive,
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what's the basis for mental illness.
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And dualism simply says it's all non -physical as part of the ether and hence fails to explain it.
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More specifically, dualists like Descartes struggle to explain how a physical body connects to an immaterial immaterial soul.
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What's the conduit?
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How could this connection be made?
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After all, Descartes knew full well that there is such a connection.
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Your body obeys your commands.
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If you bang your toe, stub your toe, you feel pain.
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If you drink alcohol, it affects your reasoning.
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But he could only wave his hands as to how this physical thing in the world could connect to an immaterial mind.
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Descartes, when he was alive, was reasonable enough concluding that physical objects cannot do certain things.
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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,
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and that, such a capacity is beyond the capacity of the physical world and hence which you have to apply, you have to extend explanation to an immaterial soul.
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But now we know we have what scientists call an existence proof.
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We know physical objects can do complicated and interesting things.
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We know, for instance, machines can play chess.
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We know machines can manipulate symbols.
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We know machines have limited capacities to engage in mathematical and logical reasoning to recognize things,
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to do various forms of computations.
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And this makes it at least possible that we are such machines.
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So, one, you can no longer say, look, physical things just can't do that because we know physical things can do a lot.
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And this opens up the possibility that humans are physical things, in particular, that humans are brains.
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Finally, There's strong evidence that the brain is involved in mental life.
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Somebody who held a dualist view that said that what we do
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and what we decide and what we think
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and what we want are all… have nothing to do with the physical world would be embarrassed by the fact
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that the brain seems to correspond in intricate and elaborate ways to our mental life.
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Now, this has been known for a for a long time.
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Philosophers and psychologists knew for a long time that getting smacked in the head could change your mental faculties,
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that diseases like syphilis could make you deranged, that chemicals like caffeine and alcohol can affect how you think.
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But what's new is we can now in different ways see the direct effects of mental life.
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Somebody with a severe and and profound loss of mental faculties,
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the deficit will be shown correspondingly in her brain.
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Studies using imaging techniques like CAT scans,
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PET, and fMRI illustrate that different parts of the brain are active during different parts of mental life.
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For instance, the difference between seeing words,
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hearing words, reading words, and generating words can correspond to different aspects of what part of your brain is active.
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To some extent, if we put you in an fMRI scanner and observe what you're doing in real time, by looking at the activity patterns in your brain,
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we can tell whether you're thinking about music or thinking about sex.
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To some extent, we can tell whether you're solving a moral dilemma versus something else.
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And this is no surprise if what what we are is the workings of our physical brains.
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But it is extremely difficult to explain if one is a dualist.
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Now, so what you have is the scientific consensus is
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that all of mental life including consciousness and emotions and choice and morality are the products of brain activities.
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So, you would expect that when you rip open the skull and look If you look at the brain, you'd see something glorious.
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You'd see like, I don't know, a big shiny thing with glass tubes and blinding lights and sparks and wonderful colors.
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And actually though, the brain is just disgusting.
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It looks like an old meatloaf.
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It's gray when you take it out of the head.
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It's called gray matter.
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But that's just because it's out of the head inside the head it's bright red because it's pulsing with blood.
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It doesn't even taste good.
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Well, has anybody here ever eaten, brain?
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I mean, it's good with cream sauce, but everything's good with cream sauce.
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So, the question is, how can something like this give rise to us?
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And, I mean, you have to have some sympathy for Descartes.
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There's another argument Descartes could have made that's a lot less subtle than the ones he did make
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which is that thing responsible for free will and love and consciousness?
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Ridiculous.
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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,
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how the brain can give rise to thought.
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And what I want to do today is take a first stab at this question
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but it's something we'll continue to discuss throughout the course as we talk about different aspects of mental life.
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What I want to do though now is provide a big picture.
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So, I want to do is start off small with the smallest interesting part of the brain
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and then get bigger and bigger and bigger here, talk about how the small part of the brain, the neurons, the basic building blocks of thought,
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combine to other mental structures and then to different sub -parts of the brain and finally to the whole thing.
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So, one of the discoveries of psychology is that the basic unit of the brain appears to be the neuron.
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The neuron is a specific sort of cell.
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And the neuron has three major major parts as you can see illustrated here.
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Neurons actually look quite different from one another but this is a typical one.
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There are the dendrites, these little tentacles here.
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And the dendrites get signals from other neurons.
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Now, these signals can be either excitatory, which is that they raise the likelihood the neuron will fire,
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or inhibitory, in that they lower the likelihood that the neuron will fire.
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The cell body sums it up.
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And you could view it arithmetically.
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The excitatory signals are pluses, the inhibitory ones are minuses, and then if you get a certain number,
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plus sixty or something, the neuron will fire.
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And it fires along the axon, the thing to the right.
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The axon is much longer than the dendrites and in fact some axons are many feet long.
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There's an axon leading from your spinal cord to your big toe, for instance.
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It is so shocking, the lights go out.
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Surrounded, surrounding, to complete a mechanical metaphor that would have led Descartes to despair,
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thank you colleague, surrounding the axon is a myelin sheath which is actually just insulation.
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It helps the firing work quicker.
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So, here are some facts about neurons.
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There are a lot of them, about a thousand billion of them, and each neuron can be connected to around thousands,
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perhaps tens of thousands, other neurons.
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So, it's an extraordinarily complicated computing device.
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Neurons come in three flavors.
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There are sensory neurons which take information from the world.
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So, as you see me, for instance, there are neurons firing from your retina sending sending signals to your brain.
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There are motor neurons.
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If you decide to raise your hand, those are motor neurons telling the muscles what to do.
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And there are interneurons which connect the two.
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And basically the interneurons do the thinking.
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They make the connection between sensation and action.
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It used to be believed, and it's the sort of thing I would've, when I taught this course many years ago I would lecture on, that neurons do not once you lose them,
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they, you never get them back.
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This is actually not true.
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There are parts of the brain in which neurons can regrow.
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One interesting thing about neurons is a neuron is like a gun.
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It either fires or it doesn't.
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It's all or nothing.
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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 used it gently.
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Now, this seems to be strange.
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Why?
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How could neurons be all or nothing when sensation is very graded?
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If somebody next to you pushed on your hand the degree of pushing, you'd be able to notice it.
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It's not either pushing or not pushing.
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You can—degrees of pushing, degrees of heat, degrees of brightness.
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And the answer is although neurons are all or nothing, there are ways to code code intensity.
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So, one simple way to code intensity is the number of neurons firing.
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The more neurons, the more intense.
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Another way to increase intensity is the frequency of firing.
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So, I'll just use those two.
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The first one is the number of neurons firing.
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The second one is the frequency of firing in that something is more intense if it's bang, bang, bang, bang, bang, bang, bang, then bang, bang, bang, bang.
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And these are two ways through which neurons encode intensity.
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Now, neurons are connected and they talk to one another.
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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.
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You wrap them around and connect them.
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It turns out this isn't the case.
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It turns out that neurons relate to one another chemically in a kind of interesting way.
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Between any neurons, between the axon of one neuron and the dendrite of another, there's a tiny gap.
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The gap could be about one ten -thousandth of a millimeter wide, this infinitesimal gap.
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And this gap is known as a synapse.
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And what happens is when a neuron fires, an axon sends chemicals shooting through the gap.
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These chemicals are known as neurotransmitters and they affect the dendrites.
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So, neurons communicate to one another chemically.
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These, again, the chemicals could excite the other neuron, excitatory, bring up the chances it will fire,
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or inhibit the other neuron, inhibitory.
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Now, neurotransmitters become interesting because a lot of psychopharmacology,
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both of the medical sort and the recreational sort, consists of fiddling with neurotransmitters.
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And so you could see this through some examples.
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There are two sorts of ways you could fiddle with neurotransmitters and correspondingly two sorts of drugs.
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There are agonists
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and what an agonist does is increases the effect of neurotransmitters either by making more neurotransmitters
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or stopping the cleanup of neurotransmitters or in some cases by faking a neurotransmitter, by mimicking its effects.
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Then there are antagonists that slow down the amount of neurotransmitters either
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because they destroy neurotransmitters or they make it hard to create
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or in some cases they go to the dendrite of the neuron
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and they kind of put a paste over it so that the neurotransmitters can't connect.
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And it's through these clever ways that neurons can affect your mental life.
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So, for instance, there is a drug known as is called curare.
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And curare is an antagonist.
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It's a very particular sort of antagonist.
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It blocks motor neurons from affecting muscle fibers.
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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.
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You send the command to your leg to move, it doesn't work the motor neurons are deactivated
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and then because the way you breathe is through motor neurons you then die.
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There's alcohol.
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Alcohol is inhibitory.
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Now, this may be puzzling to people.
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It's mildly paradoxical because you may be thinking alcohol is not inhibitory.
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On the contrary, when I drink a lot of alcohol I lose my inhibitions
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and become a I become a more fun person.
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I become more aggressive and more sexually vibrant and simply more beautiful.
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And so in what way is alcohol inhibitory?
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Well, the answer is it inhibits the inhibitory parts of your brain.
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So you have parts of your brain that are basically telling you now, largely in the frontal lobes, Okay, keep your pants on.
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Don't hit anybody.
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Don't use bad words.
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Alcohol relaxes, shuts down those parts of the brain.
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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.
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Amphetamines increase the amount of arousal.
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In particular, they increase the amount of norepinephrine, a neurotransmitter that's responsible for just general arousal.
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And so, amphetamines include drugs like Speed and Coke.
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There are… Prozac works on serotonin.
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When we discuss clinical psychology and depression,
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we'll learn the extent to which neurotransmitter disorders are implicated in certain disorders like depression.
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And one problem is that for depression is that there's too little of a neurotransmitter known as serotonin.
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Prozac makes serotonin more prevalent and so in some extent might help alleviate depression.
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Parkinson's disease is a disease involving destruction of motor control and loss of motor control, difficulty moving.
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and one factor in Parkinson's is too little of a neurotransmitter known as dopamine.
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The drug L -dopa increases the supply of dopamine and so does something to alleviate, at least temporarily, the symptoms of Parkinson's.
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So, you have neurons and they're clustered together and they fire and they communicate to one another.
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So, how does this all work to give rise to creatures who could do interesting things like talk and think?
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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.
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But we know this can't be true.
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It can't be true because there's two ways in which the brain is better than a computer.
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For one thing, the brain is highly resistant to damage.
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If you have a laptop and I I persuade you to open it up.
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for me and I take the pliers and kind of snip just about anywhere, your laptop will be destroyed.
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But the brain is actually more resilient.
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You can take a lot of brain damage and still preserve some mental functioning.
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To some interesting sense, there's some sort of damage resistance built into the brain
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that allows different parts of the brain to take over if some parts are damaged.
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A second consideration is the The brain is extremely fast.
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Your computer works on wires and electricity but your brain uses tissue and tissue is extremely slow.
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The paradox then is how do you create such a fast computer with such slow stuff?
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And you can't, if the brain was wired up like a personal computer, it would take you four hours to recognize a face.
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But in fact, we could do things extremely quickly.
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So, the question then is, how is the brain wired up?
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And the answer is, unlike many, unlike commercially generated computers, the brain works through parallel processing,
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massively parallel distributed processing.
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There's a whole lot of research, and this is research some of which takes place outside psychology departments
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and in engineering departments and science departments trying to figure out how a computer can do the same things brains can do.
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And one way people do this is they take a hint from nature
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and they try to construct massively distributive networks to do aspects of reasoning.
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So, there's a very simple computational network that is interesting
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because it kind of looks to some extent like the the way neurons look and this is often known as neural networks.
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And people who study this often claim to be studying neural
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network modeling to try to build smart machines by modeling them after brains.
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And in the last twenty years or so this has been a huge
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and vibrant area of study where people are trying to wire up machines
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that can do brain -like things from components
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that look a lot like neurons and are are wired up together as neurons are.
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One consideration in all of this is that this is a very young field and nobody knows how to do it yet.
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There is no machine yet that can recognize faces or understand sentences at the level of a two -year -old human.
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There is no machine yet that can do just about anything people can do in an interesting way.
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And this is in part
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because the human brain is wired up in an extraordinarily more complicated complicated way than any sort of simple neural network.
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This is a sort of schematic diagram, you're not responsible for this, of parts of the visual cortex.
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And the thing to realize about this is it's extraordinarily simplified.
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So, the brain is a complicated system.
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Now, so we've talked a little bit about the basic building blocks of the brain, neurons.
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We've then talked about how neurons can communicate to one another then turned to how neurons are wired up together.
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Now let's talk a little bit about different parts of the brain.
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Now, there are some things you don't actually need your brain to do.
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The study of what you don't need your brain to do
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has often drawn upon this weird methodology where this was actually done in France a lot where they would decapitate people.
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And when after they decapitated psychologists would rush to the body of the headless person
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and sort of test out reflexes and stuff like that.
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It's kind of gruesome.
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But we know there are some things you don't need your brain for.
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You don't need your brain for newborn sucking, limb flexation and withdrawal from pain.
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Your limb will pull back even if your head is gone.
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Erection of the penis can be done without a brain.
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Vomiting, also done without a brain.
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Here, I need a volunteer.
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Very simple.
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This will not involve any of the excellent, any of the above.
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Could you stand up?
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Just, okay.
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This is a new shirt so I want to stay away.
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No, this is, if you hold out your hand and one hand flat, excellent, excellent.
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That's the textbook, fifth edition.
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Perfect.
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What you'll notice is, thank you very much, What you'll notice is this hit and this hand went back up.
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This is something automatic, instinctive and does not require your brain.
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So, your brain isn't needed for everything.
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What does your brain do?
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Well, some things that your brain does involve very low level internal structures.
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And these are called subcortical structures because they're below the cortex.
410
They're underneath the cortex.
411
So, for instance, what we have here is a diagram of the brain.
412
The way to read this diagram is it's as if it were my brain.
413
I'm facing this way.
414
My head gets cut in half, down here.
415
And then you can see the brain.
416
So, this is the front over here.
417
That's the back.
418
Some key parts are illustrated here.
419
The medulla, for instance, is responsible for heart rate and and respiration.
420
It's very deep within the brain and if it gets damaged you could, you're likely to die.
421
The cerebellum is responsible for body balance and muscular coordination.
422
And to give you again a feeling for the complexity of these systems, the cerebellum contains approximately thirty billion neurons.
423
The hypothalamus is responsible here for feeding,
424
hunger, thirst, and to some extent sleep deep and here is the same brain parts in close -up.
425
Now, all of these parts of the brain are essential
426
and many of them are implicated in interesting psychological processes but where the action is is the cortex.
427
Isn't this beautiful?
428
The cortex is the outer layer and the outer layer is all crumpled up.
429
You ever wonder why your brain looks wrinkled?
430
That's because it's all crumpled.
431
If you took out somebody's cortex and flattened it out, it would be about two feet square, sort of like a nice, like a rug.
432
And the cortex is where all the neat stuff takes place.
433
Fish don't have any of it.
434
So, no offense to fish, but I think that fish don't have much of a mental life.
435
Reptiles and birds have a of it and primates have a lot and humans have a real lot.
436
Eighty percent of the volume of our brain about is cortex.
437
And the cortex can be broken up into different parts or lobes.
438
There is the, and again this is facing in profile forward, there is the frontal lobe, easy to remember, this part in front,
439
the parietal lobe, the occipital lobe, and the temporal lobe.
440
And one theme we're going to return to is this is half the brain.
441
It's, this is in fact the left half of the brain.
442
On the other half, the right half, everything's duplicated with some slight and subtle differences.
443
What's really weird, one really weird finding about these lobes is that they They include topological maps.
444
They include maps of your body.
445
Here's a cartoon which actually illustrates a classic experiment
446
by some physiologists who for some reason had a dog's brain opened up and started shocking different parts of the brain.
447
You could do brain surgery while fully conscious because the brain itself has no sensed organs to it.
448
And it turns out that the dog, when he's at part of its brain, its leg would kick up.
449
And it took Dr. Penfield at McGill University to do the same thing with people.
450
So, they were doing some brain surgery.
451
He had a little electrical thing just on.
452
I don't know how he got to do this.
453
He started zapping it and boom, the person's parts of her body would move.
454
More than that, when he zapped other parts of the brain, people would claim to see colors.
455
And he zapped other parts of the brain, right, people would claim to hear sounds.
456
And other parts of the brain people would claim to experience touch.
457
And through his research and other research it was found that there are maps in the brain of the body.
458
There is a map in the motor part of the brain, the motor cortex of the sort up on the left
459
and the sensory cortex of the sort that you could see on the right body.
460
And if you…and you could tell what's what by opening up the brain
461
and shocking different parts and those parts would correspond to the parts of the body shown in the diagram there.
462
Now, two things to notice about these maps.
463
The first is they're topographical and what this means is that
464
if two parts of the…two parts are close together on the body they'll be close together on the brain brain.
465
So, your tongue is closer to your jaw than it is to your hip in the body.
466
So, too, in both the motor cortex and the somatosensory cortex.
467
Also, you'll notice
468
that the size of the body part represented in the brain
469
does not correspond to the size of the body part in the real world.
470
Rather, what determines the size in the brain
471
is the extent to which either they have motor command over it or sensory control.
472
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.
473
But your shoulder doesn't even make it on there because although your shoulder might be bigger than your tongue, there's not much going on.
474
In fact, if you draw a diagram of a person what their body is corresponding to the amount of somatosensory cortex,
475
you get something like that.
476
That's your sensory body.
477
Eww.
478
Now, so you have these maps in your head.
479
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
480
but less than one quarter of the cortex contains these maps or projection areas.
481
The rest is involved in language and reasoning and moral thought and so on.
482
And in fact the proportion as you go from rat, cat, monkey, humans, less and less of it is devoted to projection areas and more and more to other things.
483
So, how do we figure out what the other parts of the brain do?
484
Well, there's all sorts of methods.
485
Typically these are recent imaging methods like cat scan and pet scan and fMRI which,
486
as I said before, show parts of your brain at work.
487
If you want to know which part of your brain is responsible for or language,
488
you could put somebody into a scanner and have them exposed to language
489
or do a linguistic task or talk or something and then see what parts of their brain are active.
490
Another way to explore what the brain does is to consider what happens to people
491
when very bad things happen to their brain.
492
And these bad things could could happen through lesions, through tumors, through strokes, through injury.
493
For the most part, neuropsychologists don't like helmet laws.
494
Neuropsychologists love when motorcyclists drive without helmets because through their horrible accidents we gain great insights into how the brain works.
495
And the logic is if you find somebody crudely,
496
if you find somebody with damage to this part of the brain right here and that person person can't recognize faces,
497
for instance, there's some reason to believe that this part of the brain is related to face recognition.
498
And so through the study of brain damage
499
and the study of…we can gain some understanding of what different parts of the brain do.
500
And so people study brain damages, brain damage that implicates motor control such as apraxia.
501
And what's interesting about apraxia is it's not paralysis.
502
Somebody with apraxia can move, do simple movements just fine, but they can't coordinate their movements.
503
They can't do something like wave goodbye or light a cigarette.
504
There's agnosia.
505
And agnosia is a disorder which isn't blindness because a person could still see perfectly well.
506
Their eyes are intact.
507
But rather what happens in agnosia is they lose the ability to recognize certain things.
508
Sometimes this is described as psychic blindness.
509
And so they may get visual agnosia and lose the ability to recognize objects.
510
They may get prosopagnosia and lose the ability to recognize faces.
511
There are disorders of sensory neglect, some famous disorders.
512
Again, it's not paralysis, it's not blindness, but due to certain parts of your, damaged parts of your brain, you might lose, for instance,
513
the idea that there's a left side of your body or a left side of the world.
514
And these cases are
515
so interesting I want to devote some chunk to a class in the next few weeks to discussing them.
516
There are disorders of language like aphasia.
517
The classic case was discovered by Paul Broca in 1861, a patient who had damaged a part brain and can only say one word,
518
tan, and the person can say, tan, tan, tan, tan, and everything else was gone.
519
There's other disorders of language such as receptive aphasia where the person could speak very fluently
520
but the words don't make any sense and he can't understand anybody else.
521
Other disorders that we'll discuss later on include food -acquired psychopathy.
522
where damage to parts of your brain, particularly related to the frontal lobes, rob you of the ability to tell right from wrong.
523
The final, I want to end, we're talking about neurons, connections between neurons, how neurons are wired up, the parts of the brain, what the different parts do.
524
I want to end by talking about the two halves of the brain and ask the question, how many minds do you have?
525
Now, if you look at the brain, if you took the brain out and and held it up.
526
It would look pretty symmetrical, but it actually is not.
527
There are actual differences between the right hemisphere and the left hemisphere.
528
How many people here are right -handed?
529
How many people here are left -handed?
530
How many people here are sort of complicated, ambidextrous, don't know, bit of the right, bit of the left people?
531
Okay.
532
Those of you who are right -handed, which comprises about nine out of ten people, have language in your left hemisphere.
533
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.
534
Those of you who are left -handed are more complicated.
535
Some of you have language in your right hemisphere, some in your left hemisphere, some God knows where.
536
It's complicated.
537
Now, the idea is that some things are duplicated.
538
So, if you were to lose half your brain the other half can actually do a lot
539
but some things are more prevalent and more powerful in one part of the brain than the other.
540
And I want to show you a brief film clip from Scientific American that illustrates the differences between the hemispheres.
541
But before doing that I want to provide some introductory facts.
542
Some functions are lateralized.
543
So, typically language in the on the left.
544
Again, this is a right -handed centric thing but if you're right -handed language on the left, math and music on the right.
545
There's a crossover and this is important when we think about the studies
546
that will follow but the crossover is
547
that everything you see in the left visual field goes to the right side of your brain.
548
Everything in the right visual field goes to the left side of the brain and similarly there's a crossover in action.
549
So, your right hemisphere controls the left side of the body your left hemisphere controls the right side of the body.
550
Now, finally, the two halves are connected.
551
They're connected by this huge web called the corpus callosum.
552
And I'm just going to skip this because the movie illustration will go through some of this.
553
This illustrates certain themes
554
that are discussed in detail wrote in the great book concerning lateralization of different parts of different mental capacities,
555
some in the left hemisphere, some in the right hemisphere.
556
But it also serves as a useful methodological development,
557
which is a nice illustration as to how looking at people who are incredibly unusual,
558
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,
559
such extreme cases can provide us with some understanding of how we normally do things.
560
And this again is a theme we'll return to throughout the course.
561
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
562
so that I might later on make reference neurons or neurotransmitters
563
or the cortex or the left hemisphere and you'll sort of have the background to understand what I'm talking about.
564
But I want to end this first real class with a bit of humility as to what psychologists know and don't know.
565
So, the idea behind a lot of psychology, particularly a lot of neuroscience and cognitive psychology, is to treat the mind as an as an information processor, as an elaborate computer.
566
And so, we study different problems like recognizing faces or language or motor control or logic.
567
The strategy then often is to figure out how, what sort of program can solve these problems
568
and then we go on to ask how could this program be instantiated in a physical brain.
569
So we would have solved, we study people much as we'd study a computer from an alien planet or something.
570
And I think people, this strategy is one I'm very enthusiastic about.
571
But there still remains what's sometimes called the hard problem.
572
consciousness and this involves subjective experience.
573
What's it like?
574
So, my computer can play chess.
575
My computer can recognize numbers.
576
It can do math and maybe it does it kind of the same way
577
that I do it but my computer doesn't have feelings in the same sense.
578
This is, these are two classic illustrations.
579
This is from a very old Star Trek episode, it illustrates angst.
580
I think a starship is about to go into the sun or something.
581
And that's my older kid, Max, who's happy.
582
And so the question is, how does a thing like that give rise to consciousness and subjective experience?
583
And this is a deep puzzle.
584
And although some psychologists and philosophers think they've solved it, most of us are a lot more skeptical.
585
Most of us think we have so far far to go before we can answer questions like Huxley's question.
586
Huxley points out how it is that anything
587
so remarkable as a state of consciousness comes about as a
588
result of irritating nervous tissue is just as unaccountable as the appearance of the Dijin, of the genie, when Aladdin rubs his lap.
589
It seems like magic that a fleshy lump of gray, disgusting meat can give rise to these feelings.
590
The second bit of humility, while I'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.
591
I'm not going to be talking about how beautiful it is and how wonderful it is and how mysterious it is.
592
Rather, we're going to be trying to explain it.
593
We're going to be trying to explain fundamental aspects of ourselves including questions like how do we make decisions, why do we love our children,
594
what happens when we fall in love, and so on.
595
Now, you might find this sort of project in the end to be repellent.
596
You might worry about how this, well this meshes with humanist values.
597
For instance, when we deal with one another in a legal and a moral setting, we think in terms of free will and responsibility.
598
If we're driving you cut me off, you chose to do that.
599
It reflects badly on you.
600
If you save a life at risk to your own you deserve praise.
601
You did something wonderful.
602
It might be hard to mesh this with a conception in which all actions are the result of neurochemical physical processes.
603
It might also be hard to mesh notions such as the purported intrinsic value of people.
604
And finally, it might be hard to
605
mesh the mechanistic notion of the mind with the idea that that people have spiritual value.
606
Faced with this tension, there are three possibilities.
607
You might choose to reject the scientific conception of the mind.
608
Many people do.
609
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.
610
Alternatively, you might choose to embrace a scientific worldview and reject all these humanist values.
611
And there are some philosophers and psychologists who do just
612
who claim that free will and responsibility and spiritual value and intrinsic value are all illusions.
613
They're pre -scientific notions that get washed away in modern science.
614
Or you could try to reconcile them.
615
You could try to figure out how to mesh your scientific
616
view of the mind with these humanist values you might want to preserve.
617
And this is an issue which you're going to return to throughout the course.
618
Okay, I'll see you on Wednesday.
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本课的词汇与口语要点
这段视频共有 618 个句子、7892 个单词可供跟读。 讲话部分时长为 53:06。 说话人语速平稳，每分钟约 149 个词，很适合跟读。 82% 的单词属于英语最常用的 3,000 词，其余的词建议在练习前先学一下。
视频中的重点词汇
视频中 15 个值得学习的单词，附发音和释义：
| 单词 | 发音 | 释义 |
|---|---|---|
| cortex 名词 | /ˈkɔɹtɛks/ | 皮质 |
| bang 名词 | /ˈbæŋ/ | 轟 /轰, 砰 |
| hemisphere 名词 | /ˈhɛmɪsfɪə/ | 半球 |
| wire 名词 | /ˈwaɪɚ/ | 線 /线, 鐵絲 /铁丝 |
| complicated 形容词 | /ˈkɑm.plɪˌkeɪ.tɪd/ | 複雜 /复杂 |
| disorder 名词 | /dɪsˈɔɹdɚ/ | 混亂 /混乱, 紊亂 /紊乱 |
| illustrate 动词 | /ˈɪl.əˌstɹeɪt/ | 舉例說明 /举例说明, 闡明 /阐明 |
| extent 名词 | /ɪkˈstɛnt/ | 範圍 /范围 |
| psychology 名词 | /saɪˈkɑ.lə.d͡ʒi/ | 心理學 /心理学 |
| connect 动词 | /kəˈnɛkt/ | 連接 /连接 |
| psychologist 名词 | /ˌsaɪˈkɑl.ə.d͡ʒɪst/ | 心理學家 /心理学家 |
| mesh 名词 | /mɛʃ/ | 網孔 /网孔 |
| sensory 形容词 | /ˈsɛn.sə.ɹi/ | 感覺的 /感觉的 |
| consciousness 名词 | /ˈkɑnʃəsnəs/ | 意識 /意识 |
| diagram 名词 | /ˈdaɪ.ə.ɡɹæm/ | 圖 /图, 圖表 /图表 |
视频中出现的短语动词
| 单词 | 释义 |
|---|---|
| figure out 动词 | 弄清楚 |
| turn out 动词 | 原來 /原来 |
| point out 动词 | 指, 指出 |
| take over 动词 | 接管, 接手 |
| bring up 动词 | 撫養 /抚养, 養大 /养大 |
| go out 动词 | 出, 出口 |
| go through 动词 | 通過 /通过 |
| hold out 动词 | 等待 |
需要注意的发音
说话人用了 109 次缩略和弱读形式，例如 don't, I'm, can't。请按听到的简短形式来说。
- “th” 音: hypothesis /haɪˈpɒθɪsɪs/, mathematics /mæθ(.ə)ˈmæt.ɪks/, thirty /ˈθɝti/
- “sh” 和 “zh” 音: mesh /mɛʃ/, consciousness /ˈkɑnʃəsnəs/, notion /ˈnoʊʃən/, shock /ʃɔk/, tissue /ˈtɪʃ.(j)u/
- 长单词——注意重音位置: complicated /ˈkɑm.plɪˌkeɪ.tɪd/, psychology /saɪˈkɑ.lə.d͡ʒi/, psychologist /ˌsaɪˈkɑl.ə.d͡ʒɪst/, communicate /kəˈmjuːnɪkeɪt/, intensity /ɪnˈtɛnsɪti/
如何用这段视频练习
- 先完整听一遍视频，不要开口，记下不认识的单词。
- 用正常速度逐句跟读，每句重复到你的节奏与说话人一致为止。
- 录下自己的声音并与原声对比，特别注意 cortex, bang, hemisphere 这类单词。
视频中的语法
说话人最常用的结构，并附上视频中的原话：
| 结构 | 视频中的用法 |
|---|---|
| 条件句 if + 从句，will/would + 动词 — 条件及其结果 | If you look at the brain, you'd see |
| “used to” used to + 动词 — 过去的习惯或状态，现在已不再如此 | used to be |
| 被动语态 be + 过去分词 — 强调发生了什么，而不是谁做的 | is summarized · can be found · is known |
| 现在完成时 have/has + 过去分词 — 过去发生但与现在仍有关联的事 | I've been fooled · has tricked · has taken |
什么是跟读法？
跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。