Professor Paul Bloom: Two follow-ups on yesterday's--I'm sorry, on Monday's lecture. One is that somebody came up after class and asked when the preference for your own language emerges in development and fortunately, [A graduate teaching assistant] studies pretty much exactly this sort of infant understanding. She knew the answer. There's been studies looking at newborn babies finding that pretty much the moment they pop out they favor their own language over other language--over other languages. And this suggests that they are listening while in utero, while in the womb, to the rhythms of their language and developing a preference for it.
ZlW*HGY4c(z0A second issue is, I talked very briefly about a court case in which the person was--said at a moment where someone else was pointing a gun at a police officer, "Let him have it!" and a police officer was killed. And that person was charged with murder but I admitted I didn't actually know how things turned out and [a graduate teaching assistant] was kind enough to do extensive research. Well, he went to Wikipedia and [laughter] found out the answer. The answer is he was tried and found guilty for murder. He was then subsequently pardoned. In fact, he was pardoned in 1988, which is really nice except he was executed in 1957. But they did it into a movie. So, it's a movie.
Okay. So, I want to do today, for the first part of the lecture, is continue the language lecture and then move to perception, attention, and memory. And what we had spoken about was--We first talked about universals of language, then moved to some detail about the different aspects of language including phonology, morphology, and syntax. We discussed the ways in which language does the amazing things it does, including the fact that language has used arbitrary science or sounds to convey concepts, and that languages exploit a combinatorial system including recursion to put together these symbols into a virtually limitless set of meaningful sentences. We then talked about development and made some remarks about the developmental time course – talking about the emergence of language from babies to – where babies are really good at learning language to you who are not, whose brains have atrophied, whose language capacities are dead.
Final issue is to shift to animals. Now that we know something about language, we could then ask do animals use--possess the same sort of language? And if not, can they learn it? Now, there is absolutely no doubt at all that nonhuman animals possess communication systems. This has been known forever and is not a matter of controversy. And if you want to use the term "language" to mean "communication," then the answer is obviously "yes." Dogs and bees and monkeys have language. If you want to use language though in the more technical, narrow sense as anything that has the properties that we discussed earlier, using English and ASL and Spanish and so on as our background, the answer's almost certainly "no."
Animal communication systems fall into sort of one of three categories. Either there is a finite list of calls, so vervet monkeys, for instance, have a small list of calls to convey different warnings like "attack from a snake" or "attack from a leopard." There is a continuous analog signal. So, bee dance, for instance, works on this way. Bee dance communicates the location of food sources but doesn't do it in any syntactically structured way. Rather, the intensity of the dance corresponds to the richness of the food source. And then, you get things like random variation on a theme such as birdsong. But what you don't find in any real sense is phonology, morphology, syntax, combinatorial systems or arbitrary names.心理学空间^LviZ*I8Q8w
Now, this much is not particularly controversial. There gets to be a lot of controversy though. This is the summary about nonhuman communication systems. It gets more controversial when we get to famous cases of primates trained by humans such as Kanzi, Nim Chimpsky, and other famous primates that you may well have seen on the Discovery channel and other venues. And this is fairly controversial. If you read the Gray textbook, while nothing in it is particularly inaccurate, I think Gray is actually a little bit too credulous, too believing in the claims that have been made about the abilities of the animals. So many scientists argue, for instance, that animals like Kanzi, even if they can be said to be learning words at all, learn very few of them. And it takes them extensive years of training to learn, unlike a normally developing child who could learn a word in a day or a word in an hour. The utterances often have order but this order tends to be very limited and lacks the recursive properties. And in fact, the lack of recursion is not controversial.心理学空间.T8w?(@8t tJr2K$p
7d0gT6^bX%I,W0Finally, the utterances of chimpanzees--trained chimpanzees are extremely repetitive so what you often see on TV and in documentaries is sort of a sampling. And the sampling could often be very impressive but if you take just what they say at random it tends to look like this. This is typical chimpanzee utterances just taken at random: "Nim eat, Nim eat. Drink, eat, me Nim. Me gum, me gum. Tickle me, Nim play. Me eat, me eat. Me banana, you banana, me you give. Banana me, me eat. Give orange, me give, eat orange, me eat orange." Lila Gleitman once commented that if any normally developing child spoke like this, his parents would rush him screaming to a neurologist.
There's a broader question here, which is, "Why would we ever expect a chimpanzee to learn a human language?" We don't normally expect one species to have the capacities associated with another species. So, bats use echolocation to get around and some birds navigate by the stars, but there's not an active research program seeing if cats can use echolocation or dogs could navigate by the stars. And I think one reason why you might be tempted to think, "well, of course chimps must be able to learn language" is because you might be caught in the grips of some bad ideas about language.心理学空间1{H4zI7Q0H U
So, one idea is you might say, "Look. Chimps should use language because chimps are so smart." But the response to this is, "they are smart but we know that smart isn't enough." We know that the human capacity for language is not totally a result of smartness. There are smart children who, due to some deficit in their language capacity, don't speak or understand a language. So, the smartness of chimpanzees does not in itself demonstrate that they should be able to learn language.心理学空间$M M#DsGQ(?b/A
You might also point out correctly that chimps are our nearest evolutionary relatives, which is right, so you--one would expect on the face of it--it's not unreasonable to expect us to share a lot of abilities with them. On the other hand, we split from them a long time ago and plainly humans are different from chimps. And there was five million years either way and that's more than enough time for a language capacity to evolve.心理学空间;g.efp `
Now, none of this is to say that the study of nonhuman communication systems isn't interesting. From my own--This is my personal opinion I'll raise here. From my own opinion, the study of the attempts to try to teach chimpanzees, or gibbons, or gorillas, a human language like ASL are misguided. It would be as if a team of monkeys kidnapped a human child and tried to train him how to hoot like a monkey. It might be enjoyable but it does not seem to give us any rich insights. What I think is a lot more interesting is the study of these animal communication systems in the wild. There's a linguistics of human language that has delineated the principles that underlie all human languages. It would be as extraordinarily interesting to attempt the same linguistic program to the other communication systems used in the wild such as the cries of vervet monkeys and bee dance.心理学空间5wn2K-r9W;{:n
So, this brings the section on language to a close but I want to tell you a few things we didn't talk about. One of the problems with an Intro Psych course is we have to whip through a lot of topics very fast. So, if you were to take a course that focused directly on language you might learn, for instance, more about language in the brain, something touched about very briefly in the textbook but something that has a large literature associated with it. Similarly, and related to this, there's language disorders, disorders like aphasias and disorders like specific language impairment and dyslexia. There is the study of language perception and production. How is it that we do this amazing feat of understanding and producing words in a fraction of a second? Where does that ability come from?
There is the study of reading which is, in many ways, different from the study of a language. Remember when Darwin described language as an instinct. He carefully distinguished it from other things that don't come natural to us including reading. And in fact, reading is difficult. Reading is a cultural invention, not every human has it. And unlike language, reading is acquired with tremendous difficulty over many years. On the other hand, reading plainly intersects with language. It's a new way of conveying language, moving out from speech to writing. And the psychology and neuroscience of reading is thus very interesting.
#uMrEmO0There's bilingualism and multilingualism. The questions people in this room typically are going to be interested in is does it matter for how well you learn language whether you're learning one or two or three or four. How is it that a multilingual encodes all these different languages inside a single brain? And so on. Finally, a very hot issue is that of the relationship between language and thought and I'm actually--A few years ago I taught an entire seminar called "Language and Thought" devoted to precisely this question. And it's a cool question and it could break up into two very general questions. One is, "Is language necessary for abstract thought?" And one way to answer that question is to look at creatures without language like babies and chimpanzees and see how smart they are. It might be that they're not--that they're very smart, in which case it would suggest you don't need language for abstract thought. On the other hand, it might be that they have certain cognitive limitations, which would suggest that language is essential for abstract thought.
:W jCe L B4f5g~7f0Then there's the related question. Even once you know a language, does the structural properties of the language that you know affect the way you think? And the claim that the language you know affects how you think is sometimes described as linguistic relativity or the Sapir-Whorf hypothesis. So for instance, there's a lot of research looking at speakers of different languages such as English versus Korean and seeing whether structural differences in these languages affect how you think. Now, some of this work is discussed in the readings, the book--the Gray textbook, and the selections fromThe Norton Anthology.And this makes up--again, I've showed this to you on Monday--your reading response where you have to address this question and take your best shot at answering it. What are your questions about language? Yes.
Student:[inaudible]
+QlJOH0Professor Paul Bloom:The question was raised, "Some people learn languages easier than others and how do we explain this?" And the answer is you could ask the question both with regard to first language learning – so some children learn language very quickly, some are very slow – and also with regard to second language learning. Some of you are breezing through your second language requirement here at Yale. Others are struggling and miserable. And there's considerable variation. There's the story of Einstein who was very slow to learn language and didn't speak at all until he was four. And in fact, he was a--He said his first words when all of a sudden he was having supper with his parents and he put down the spoon and he said, "The soup is too hot." And his parents stared in astonishment and said, "You've never spoken before." And he said, "Well, up to now everything's been fine." [laughter] It's not a true story. [laughter]
The question of why and where these differences come from, nobody really knows and it's surprisingly hard. There's a slight advantage for being female. Girls are slightly more advanced in language than boys but it's not a big one and you need a hundred people to just see it statistically. There's a big genetic factor. If your parents learned language quickly and learned other languages quickly, you are more likely to. But an understanding of the brain bases of these differences or the cognitive bases or the social bases is just--is largely an open question. Yes.心理学空间M7ezFa4y B)U(z
5` eFLV*K*_^l py0Student:What happens when parents [inaudible]心理学空间V8q8K@4}r
&TtnD:o3Q ]0Professor Paul Bloom:This is actually more the norm around the world than the situation in the United States where kids are exposed to a single language. What happens is children learn both languages. Children are very good, as adults are, of distinguishing different languages on the basis of their sound system and their rhythms so they don't typically confuse them. And then they just learn more than one language. And that's actually more the average state of affairs around the world. Yes.心理学空间w7`5Rh9[(F\[c
3N M5ZHja0ty8lq0Student:You said that people who are right-handed learn languages [inaudible]
Professor Paul Bloom:The question is about the hemispheric specialization for language. And I don't have actually much more to say than what I said before, which I agree is deeply unsatisfying. If you're right-handed, language is probably in the left side of your brain. How many people here are left-handed? For you we don't know. It varies. Some of you have it in the left side. Some of you have it in the right side. For some of you it's kind of diffuse. Now, why is this? And in fact, why are some people right-handed and others left-handed in the first place? Those are really good questions. Yes.心理学空间m_k1eZl;N8Ag-p0H
mhIf%cfwj7pq5Y0Professor Paul Bloom:Yes. I'll--Yes, that's--I'll answer that question. And unfortunately, it's going to be the last one and then I'll go to vision. The question is, "Does learning more than one language cause you to learn them slower than just learning one language?" And it would stand to reason that it would. There's a finite amount of mental resources. If I'm just learning English, I use all of it for English. And if I'm learning English and Spanish I kind of got to split. And you'd expect them to be each learned slower. It's one of the surprises of the study of language development that that common-sense view does not appear to be true. Children learning more than one language seem to show no deficit relative--in each of their languages, relative to a child learning just one language. In other words, if I am just learning English and I'm a kid and you're learning English and Spanish and you're a kid, you'll reach the milestones in English the same time I will. Your extra learning of Spanish doesn't seem to affect you. There doesn't seem to be any detriment for learning multiple languages.
%]\X~H/UC6k0Another question which comes up is, "Is there any cognitive deficit?" In other words, some people have argued that learning multiple languages sometimes harms children in certain ways. This is a claim that's been made in Quebec, for instance, over the debate over how children should be taught English and French. It does not appear to be the case. There appears to be, as far as we know, no down side to learning many languages when you're young. Does that answer your question?心理学空间A/{F9]+R*f-P+@
g1qF!YX.@#Q0I want to move now to the topic that will take us through today and through the beginning of next week – perception, attention, and memory. And I'm putting them together instead of treating them as separate lectures because there's a sense in which they're the same story. You see a scene. You see this scene and you're looking at it and you're perceiving it. It's coming through your eyes and you're interpreting it and you see something. You see a man and you see a house. If you were to shut your eyes, you could still hold that scene in memory. And a week later, if I'm to ask you about that, "What season was it?" you would do pretty well. This is the story I want to talk about – how we do this.
And in the course of this I want to make a series of claims that go something like this. For perception, I want to first persuade you the problem of perception's hard and that successful perception involves educated and unconscious guesses about the world. For attention, I want to suggest that we attend to some things and not others and we miss a surprising amount of what happens in the world. For memory, there are many types of memory. The key to memory is organization and understanding. And you can't trust some of your memories.心理学空间VN5l w2p@m GJMD
HM@k7t3e0C9m0How many of you remember where you were at 9/11? Many of you are wrong. And I am never going to persuade you of this because you have certain memories. And you could tell the story. Everybody could tell the story where they were when the towers went down. But clever psychologists on September 12 said, "Let's do a study." And they asked people, "Where were you yesterday when you heard the news?" And they told them. And then they went back to them later, a year later, two years later, and said, "Tell me about what happened September 11." And they said, "I remember totally where I was. I have a very--" And then--And often the story was wrong. There is a lot like that which we're going to talk about. And the biggest moral then--so, I put it really, in really big print--We are often wrong about our experiences, both of the present and of right now. So, let's start with perception.
There is a story--I went to graduate school at MIT and there was a story there about Marvin Minsky who is the A.I. [artificial intelligence] guru. He--If you've heard the words--the phrase "artificial intelligence," that was him. And if you heard the claim that people are nothing more than machines made of meat--also him. Well, there's a story where he was doing work on robotics and he was interested in building a robot that could do all sorts of cool things that's like a robot. And the story goes the robot had to among--had to write--had to see the world. It had to be able to pick up things and recognize people and see chairs and navigate its way and Minsky said, "That's a tough problem. It's going to take a graduate student a whole summer to figure it out." And he assigned it to a graduate student for a summer project.心理学空间Q!rl.gy)CXz
nix)w8f0k0Visual psychologists, perception psychologists, love that story because the study of computer vision and robotics vision and the attempts to make machines that can identify and recognize objects has been a profound failure. There is, at this point, no machine on earth that could recognize people and objects and things at the level of a really dumb one-year-old. And the reason why is that it's a much harder problem than anybody could have expected. Well, what makes it such a hard problem?
Well, one reason why you might think it's an easy problem is you say, "Okay. We have to figure out the problem of how people see. Well, here's what we do." [pointing to a slide that caricatures the inside of a person's head as containing a little man, the real "you," sitting in a control room watching a television monitor that is connected to the larger-head's eyeballs] You're in--You're over there and here's your eye. And somehow it has to get to this television monitor and then you look at it and that'll solve the problem of how you see. So, sometimes people say, "Hey. I hear the eye flips things upside down. I guess this guy [the guy in your head] is going to have to get used to looking at things upside down. That's an interesting problem." No. That's not the way to look at it because that doesn't answer any questions. That just pushes the question back. Fine. How does "he" see? We're not answering anything.
U"u*^1D0f:H[0Similarly, although the Terminator's [the cyborg assassin from the movie "The Terminator"] view of the world may correspond to that [showing a slide of what vision looks like to the Terminator – a series of gauges and numbers], that doesn't solve any problem of how he actually sees. So, he has all these numbers shooting out there. Well, he has to read the numbers. He has to see this. This [pointing to some icons at the edge of his slide] is my iTunes. [laughter] That's inadvertent.
Here's the right way to think about perception. You got the eye, which is very ugly and bloody, and then around here you have the retina. And the retina is a bunch of nerve cells. And the nerve cells fire at--for some stimulus and not others. And from this array of firings, "firing… not firing… firing… not firing," you have to figure out what the world is. So, a better view is like this. The firings of the neurons could be viewed as an array of numbers. You have to figure out how to get from the numbers to objects and people, and to actions and events. And that's the problem. It's made particularly a difficult problem because the retina is a two-dimensional surface and you have to infer a 3D world from a two-dimensional surface. And this is, from a mathematical point of view, impossible. And what this means is that there--For any two-dimensional image there is an indefinite number of three-dimensional images that correspond to it.心理学空间C~7i9p\$i2l
So for instance, suppose you have this on your retina, an array of light shaped like that [referring to a slide portraying a square and an irregular polygon that could be a square that is tilted backwards in space]. What does that correspond to in the world? Well, it could correspond to a thing just like that that you're looking for or it could correspond to a square that's tilted backwards. And so, you have to figure out which is which. And the way we solve this problem is that we have unconscious assumptions about how the world works. Our minds contain certain assumptions about how things should be that enable us to make educated guesses from the two-dimensional array on to the three-dimensional world.心理学空间;K WMg&au
And I purposefully did not make the slides available for this class ahead of time because I don't want people to cheat, but there are several points where you could look at the slides and confirm that some of the things I'm going to tell you are actually true. And I want to give you three examples. One is color. And I'm going to conflate here color and brightness. The other is objects. The other is depth.心理学空间-|X%x|i.\Z7jZ
*r8G e/BX#t&A ?-BeE0First, the problem of color. How do you tell a lump of coal from a snowball? Well, that's a lump of coal and that's a snowball, and it's from Google images. How do you know which is which? Well, a lump of coal you say is black and a snowball is white. How do you know? Well, maybe you have on your retina--Your retina responds to sort of color that hits it. It's oversimplified, but let's assume that this is true. So, this is black coming out and that's white and that's how you tell. But in fact, that can't be right. It can't be right because objects' color is not merely a matter of what material they're made of but of the amount of light that hits it. So, as I walk across the stage I fall into shadow and light, and none of you screams out, "Professor Bloom is changing colors!" Rather, you automatically factor out the change in illumination as this is happening.
And this could actually be quite striking. So, you see this display over here. Take a look at those two blocks. [a slide portrays two blocks of different luminance, one under a table, one in the middle of a lit room.] I take it you see this one [the object under the table] as lighter than that one. You do. You might imagine this is because this strip [the block under the table] is lighter than this [the block out in the open] but it isn't. They're the same. And you won't believe me until you actually print it out and take a look, but they are in fact the same. I'll show it to you. And you could say I'm tricking you but this is the way it works. There's the close-up. So, remember we're comparing this and this [the two blocks]. Now, let's take away other parts of the environment and you'll see they're the same. [As Professor Bloom covers the background surrounding both of the blocks they suddenly appear to be the same color as one another.]
"i I1X0A{qn2K j0Now you say, "But hold it. This can't be the same as this" but the answer is--goes like this. We know shadows make surfaces darker. We don't know this like "Here's something I know." Rather, we know this in that it's wired up in our brains. So when we see a surface in shadow we automatically assume that it's lighter than it looks, and we see it as lighter. And you could show this by removing the cues to the shadow. And you see it as it really is. And this is an illustration of how the information to your eyes is just one bit of information; the degree of light coming from a single source is one bit of information that you use to calculate certain assumptions and come to a conclusion.心理学空间`1JQ6r2Jx
)K;f6\6YblN!}{0Here's a different kind of example: Objects. You see this [a picture of a man walking down a path, in front of his house] and you automatically and intuitively segment it into different objects. You segment it into a man and a house and birds and trees. How do you do this? It turns out, to program a computer to segment a scene into different objects is hugely difficult and the question of how we do it is, to some extent, unknown. But one answer to this question is there are certain cues in the environment that are signals that you're dealing with different objects. And these cues are often described as Gestalt principles.
:JS:Jh%t Hj0So, one example is "proximity." When you see things that are close to each other, you're more likely than not to assume that they belong to the same thing. There's "similarity." That display [a group of many objects that are all the same shape, but all the objects on one side have a different texture than those on the other side] could correspond to an indefinite number of objects but you naturally tend to see it as two. You do one with one texture pattern, the other with the other texture pattern. "Closure." The fact that this is a closed square here suggests it's a single object [referring to a line drawing of a square overlapping a circle]. "Good continuation." If you had to judge, this [referring to a picture of two overlapping lines, line AB and line CD] could just as well be two shapes, one that runs from A to C, the other one that runs from D to B. But you don't tend to see it that way. Rather, you tend to see it as one that runs from A to B, the other one that runs from C to D. "Common movement." If things move together they're a single object. And "good form." You see the object over there [two overlapping and perpendicular rectangles]. In the absence of any other information, you might be tempted to say that's a single thing, a plus sign maybe. This [pointing to two overlapping but non-perpendicular rectangles], because it has lousy form, you're more tempted to say it's two things, one thing lying on top of each other.心理学空间2?-\4P3dG'T
.~9l5`-Vj7yjB,P0And these are the sort of cues, expectations; none of them are right. There's cases where they could all fool you. But these are useful cues that guide our parceling of the world, our segmenting of the world into distinct objects. Here they are summarized [pointing to a slide showing all the cues on the same page]. And here's a case where they fool you [pointing to a slide showing a Kanizsa Triangle, an illusory triangle induced by three incomplete circles]. So you might think, if you're suggestible, that there is a triangle here. And this is a case where there are certain cues driving you to think that there's a triangle here. There is, however, no triangle here. If you cover up these little Pacmen here, the triangle goes away. Similarly, there is no square in the middle [referring to a picture of a Kanizsa Square]. There is no square. It's veryMatrix. And these are illusions because these are cues that there should be a square there, the regularity of form.
/H9oH7[ q/Vl0Finally, "depth." You see this [the picture of the man walking away from his house] and you don't--You see it on one level as a flat thing. Another level you look inside the picture and you see, for instance, the man is in front of the house. You look at me and you see the podium. And if you have a terrible neurological disorder you see this strange creature that's half podium leading on to a chest and up to a head that's sort of--the top of him is wiggling and the podium staying still. If you are neurologically normal, you see a man walking back and forth behind a podium. How do you do that? Well, this is really a problem because, I could give you a technical reason why vision is hard, but crudely, you got a two-dimensional retina and you have to figure out a three-dimensional world. How do you do it? And the answer once again is assumptions or cues. There are certain assumptions the visual system makes that aren't always right and in fact, in cases of visual illusions, can be wrong but will guide you to perceive the world in a correct and accurate way.
:R#Y dF]+C[$|/~9A0So for example, there is binocular disparity. This is actually a sort of interesting one. This is the only depth cue that involves two eyes. If I look at you [a student sitting in the front row] pretty close, the image I get here [pointing to his right eye] and the image I get here [pointing to his left eye] are somewhat different while--or I have to focus my eyes together to get the same image. If I look at you in back, they're almost identical because the further away, given the two eyes that are static, the closer the images look. And it's not, again, that you say to yourself, "Oh. Back there an orange. It's the same image in my right eye and my left eye. You must be far away." Rather, unconsciously and automatically you make estimations on how far people are in depth based on binocular disparity.
C-E2@){ E:H0There is "interposition." How do you know I'm in front of the podium and the podium's not in front of me? No. How do you know the podium's in front of me? Well, from where I'm standing it's right. How do you know the podium is in front of me? Well, because I'm walking here and then it cuts into me. And unless I'm going through a grotesque metamorphosis, what's happening is it makes sense to say I'm moving behind the podium. Interposition. You take the guy. How do you know the guy is standing in front of the house? Well, because there is--you see all of him and he's blocking a lot of the house.
"p!Cf6D S z5TA0There's relative size. How far away am I? Well, if you looked at me and you had to estimate how far away I am, part of the way you'll figure that out is you know how tall a human's supposed to be. If you thought that I was fifty feet tall, you would assume I'm further away than I am. And so, your judgments on size dictate your judgments about distance. Usually, this cue isn't necessary but if you look at the Empire State Building--If you go into a field and you see a tower and you look, your judgment of how far away the tower's going to be depends on your knowledge of how tall a tower should be. If it's this tall, you say, "Oh. It must be--" And then you'd be surprised. There's texture gradient, which I'll explain in a second, and linear perspective, which I'll also explain in a second.心理学空间/am&k u4T@&t
d|o-q9y"ha-K9x@0Texture gradient goes like this. Remember the problem we had before. How do you know if that thing [a spotted rectangle that's tilted backwards] is this object [a spotted rectangle standing upright] or an object in and of itself? Well, the answer is things with textures will show themselves because the textures will get smaller from a distance. Now, logically, this could still be a single thing standing upright with just dots going up smaller. But the natural assumption is the reason why the dots recede in this regular fashion is because it's receding in depth.
/F3DRp\ \ h9b0Classic illusion – the Mueller-Lyer illusion. People will see this as longer than this [referring to one of two arrow-like lines, one with both ends pointing inward, the other with both ends pointing outward]. It's not. If you don't believe me, print it out and measure it. Related to the Ponzo illusion, once again people see this one [showing a picture of two gradually converging lines crossed by several horizontal lines, like a train-track receding in the distance] as--you get illusions named after you when you discover these--this one [a horizontal line at the top] as longer than this [a horizontal line at the bottom]. Again, it's not.
What's going on here? Well, the top line looks longer even though it isn't. And one explanation for why is, these other lines in the scene cause your visual system to make guesses about distance. And then you correct for distance by making assumptions about size. If you have two lines--You'll get--We'll get in more detail in a second, but if you have two lines and they take up the same amount of space on your retina, but you believe that one is 100 feet away and the other's 50 feet away, the one that's 100 feet away you will see as bigger because your brain will say, "Well, if it takes up just this much space but it's further away, it must be bigger than something that's closer and takes up that much space." And that's what goes on here.
j6~I~"\dq|,[0For the top line, for the Mueller-Lyer illusion, we assume that this is further away and this is closer based on the cues to distance. And the cue is factored in. And because we assume that this is further away, we assume it must be bigger to take up the same space as this which is closer. Similarly for the Ponzo illusion. There's linear perspective. Parallel lines tend to recede in distance. If this top one is further away than this but they take up the same size in your eye, this one must be bigger and you see it as bigger. And the book offers more details on how these illusions work.
1S4j$meREu6L0I'm going to end with an illusion that I'm not even going to bother explaining. I'll just show it to you because you should be able to, based on thinking about these other illusions, figure it out. It was developed by Roger Shepard. Well, you know that. And they are called Shepard tables [pointing to a picture of what looks like two simple dining tables, or desks. One that looks longer and skinnier than the other]. And the thing about it is, these look like two tables. If you ask people--You don't frame in terms of here's a lecture on visual perception. You ask people, "Which of these tables would be easier to get through a door if you have a thin door?" People would say the one on the left. This one looks sort of thicker and harder to get through. This one looks longer and leaner. In fact, they're the same size. What I mean by that is that this [rectangle] is exactly the same as this [rectangle].
Now, I'm going to prove it to you by showing you something which took me--on the computer which took me about seven hours to do. And nobody's going to believe it because I could have faked it. But if you want, print it out and do it yourself. You just take a piece of paper, put it on here. Then you move it [he demonstrates that a piece of paper, cut to be the same size as one of the tables, fits perfectly over the other table] and [they're] the same. I showed it to somebody and they called me a liar. Anyway, you could do it yourself in the privacy of your own home or study. But what I'd really like you to do after you do it is say, "Okay. Fine. Why does this one look longer and thinner than this one?" And the answer is the same answer that will explain the Mueller-Lyer illusion and the Ponzo illusion, having to do with cues to depth and the way your mind corrects the perception of depth. And that's all I have to say at this point about perception.
I want to move now to attention and memory and I'm going to treat attention and memory together. We are fascinated with memory and, in particular, it's particularly interesting when memory goes wrong. It's particularly fascinating what happens in cases of amnesia. So for example, I need a volunteer who is willing to do a little bit of acting, a very little bit, an incredibly little bit. [a student volunteers] Excellent. Okay. So well, you just stay there. So pretend you have amnesia. Okay? What's your name?心理学空间 Awd zYc}?g8v?