Chapter 23 Chapter Fourteen Perceptual Psychologist-1

The minnow has very little brain to speak of, but it can see (more or less); so does an ant, although its entire nervous system consists of only a few hundred neurons; The same is true for species not above.From this point of view, visual perception is a physiological function. Although it affects many psychological processes, it is not any physiological process itself. (Given that most psychological research deals only with vision, we'll set aside other perceptions for now.) For centuries, however, most philosophers and psychologists have argued that, at least in humans, perception is fundamentally a mental function; And of course only limited to what our senses tell us.Knowledge is deflected from perception, and thus raises a whole host of interesting questions (not in the usual sense of "fascinating", but of scientific "importance" or "potentially leading to new ideas" meaning).However, although philosophers have considered the question of perception for over 2,500 years, and physiologists and psychologists have studied it for nearly 400 years, some of the most interesting questions remain questions, while others Many of our problems have been solved in various ways, but the solutions themselves have created countless new problems that are equally troublesome.

Consider the fact that the ancient Greek philosophers were the first to ask the question: How do images of the outer world enter the inner intellect? Plato had an idea that the human eye is actively making a search for objects that can be touched—visually, so to speak.Democritus disagreed with him, arguing that perception works just the opposite: each object is constantly imprinting its equality in the atoms of the air, and these replicas can interact with the atoms of the eye when they are communicated to the recipient. function, and then re-construct the equality in the eyes, so it is conveyed to the mind at this time.The idea is a little stronger than Plato's, but wrong in every detail.

German astronomer Joanne Kepler made another giant leap in the understanding of vision in 1604.The developments in optics and optical instruments that were just emerging in Kepler's time gave him the ability to see that the clear object in front of his eyes was a lens that bends the light rays coming from the object and then formed a relevant one on the sieve-like retina inside the eye. The image of the object, the nerve impulses obtained from here are then transmitted to the brain. Since then, the idea that the eye is a kind of camera has spread, a metaphor that fits the phenomena of nearsightedness, farsightedness, and astigmatism, and that they can be corrected with the eye.But while it is true in some respects, it is completely untrue in many others.Ralph N. Harper, long known in the study of perception, said the metaphor of the human eye as a camera "is one of the most promising but at the same time misguided metaphors in the history of psychology," As a result, countless "harms" have been caused.

Which kind of hazard?On the one hand, in a camera the image formed by the lens is inverted, and in 1625 the astronomer Christopher Schinner proved that this is correct for the eye.He carefully peeled back the covering from the back of the bull's eye, and saw an upside-down object through the translucent retina.But if we see the images formed on the retina, why don't we see an upside-down world?This question will haunt psychologists for 300 years. The trouble with the metaphor of the eye as a camera became even more apparent with the advent of photography.In order for the camera to produce a clear image, it must be firmly grasped when exposing, and if it is a moving movie, its shutter must be opened and closed many times in a second.The human eye, however, keeps flickering back and forth, even when staring at something, but the human eye does not see blurry images.Although we are not aware of, and generally do not experience, these movements, we can see objects in very simple ways.We can stare at the black dot in the center of the picture below for about 20 seconds, then quickly move our eyes to look at the white dot.You'll see an optical illusion of black lines wobble back and forth.These black lines are an afterimage, which is caused by temporary fatigue caused by white lines falling on the retinal receptors for about 20 seconds.The cause of the shaking is the never-ending movement discussed in this chapter.

The implication of this demonstration is that the eyeball might be a kind of camera, but seeing things is quite different from taking a picture. Another interesting question: Are the things we see really there?And then infer a question: Is this thing what we see?The folklore is that what we see is there, and what we see is a faithful reflection of what really is.We see a door in front of us, reach for the handle, and the handle is where we think it is, and it responds as we expect it to.We lean down on the chair, and the chair is as real and solid as it appears to be.We fork a piece of food into our mouths and it's just as rich, meaty and juicy as we expected it to be.Both common sense and philosophy hold that perception is contact with reality.Only a few rare and extraordinary persons, such as Archbishop Berkeley, have raised some doubts that there is a world outside our bodies, which corresponds only to our perceptions.

However, despite the reasonable assumption that perceptions are real by nearly all of us, we often experience things that we know are misleading and false.The moon looks huge when it's far on the horizon, and we all know that the moon doesn't change its size when it's overhead, but we can't bring ourselves to make it look as big as it does when it's on the horizon.We stare at a bright line, and when we turn our heads we see an afterimage—a perception that is not anything that exists outside of us.In our dreams we see people, places, and actions that do not exist in front of us, things that seem to be around us, but may not exist at all.

Besides, there are many other delusions that have been studied by psychologists in the past and in the present century.In the image below: The grayscale areas in the middle of the two circles look very different from each other, but their grayscales are actually the same. You can cut a small hole on a piece of paper, and put the small hole facing one of the circles first. Gray area, and then face another gray area, so that it can be determined whether there is a difference in the gray level.The mind, or at least the cortex of the brain, judges its brightness by contrast, not by its absolute density.What we see is not necessarily what actually exists.

There are several classic examples, each named after its inventor: (1) Zellner's figure; (2) Pogendorf's figure; (3) Jestoro's figure; ( 4) Hering's graph: The straight lines in the first picture are parallel to each other, which is different from what the eye sees (you can use a ruler to measure it), the diagonal lines in the second picture are aligned with each other, not offset from each other, and the third The two bends in the first picture are also the same size, and the thick black line in the fourth picture is also straight. Another group of illusions consists of blurred figures that we can perceive as either between two different things.Here two examples:

In Figure (1), you can let yourself see the familiar Nacar’s box, as if you are overlooking it, and the X angle is closest to you; you can also let yourself look up at it, and at this time, the Y angle is closest to you .In picture (2), you can see that the handle is clinging to the two white walls inside the basket, or it can be seen as clinging to the black wall. Finally, in the image below, there appears to be a triangle that is much whiter than the surrounding area. However, it is you who created this triangle and its brightness.There is no such triangle, and the paper is not whiter than the rest of it.

Further down, we get an explanation for these illusions.Right now, what we care about is that human perception is not a simple physiological process, which only transfers external stimuli to the central nervous system.It often also includes higher mental processes that make (or render meaningless) the impulses transmitted through the optic nerve.At least, many perception researchers now believe so, although others insist that perception does not make use of higher mental processes. A third intriguing problem—which Ewen Poling called "the first visual puzzle" in his landmark work "History of Experimental Psychology"—we have two eyes, yet humans see every One thing is never double.Gallen correctly hypothesized long ago that this is because the nerve cells in both eyes go to the same brain area.However, this is only part of the answer.Except for distant objects, the two retinas receive slightly different images of all objects, as is easily evidenced by taking turns looking at a nearby object with both eyes open and closed. (Each eye sees more on one side of an object than the other, and objects relate differently to things in the surrounding background.) However, if these slightly different images are superimposed in the brain, the result Why is it not blurred?

Perception researchers replied that the "coincidence" of different images occurs in the visual cortex.A three-dimensional image is obtained.They even pinpointed the specific cells in the cortex that were fired differently between the eyes.But how these cells, or others into which they feed information, superimpose the different images to form a three-dimensional picture is still a mystery. Another interesting question, and one of the most puzzling, is how is the image on the retina reflected in the brain?The brain does not have a screen for projecting images, so how is the data stream entering the brain seen?And, if the image is somehow projected onto this screen, or somewhere else in the brain, who or what is seeing the image?This question brings to mind the old saying that there is a dwarf or dwarf - the thinking "I" - who perceives information reaching the inner cortex of the brain.But if the dwarf is looking at the image, what is it looking at?Is it some sort of eye thing too?So, who or what is observing what reaches the center of dwarf vision?Etc., etc. Closely tied to this mystery is another problem of visual memory.Every adult has a large number of images stored in his or her brain: familiar faces, houses, trees, blades of grass, clouds, beds in which one has slept.These things are somehow recorded after a little observation.Although we can't bring all of these into our brains at once, we can recognize things we see a second time through these memories. In 1973, Lionel Standing, a very patient Canadian psychologist, asked volunteers to watch more than 10,000 snapshots of different subjects. He displayed the photos at a rate of 2,000 per day for 5 consecutive days.Later, when he mixed these pictures with some other new pictures for the subjects to see, they could recognize two-thirds of the pictures they had seen.Where and in what form do they store all these fleeting images?When they saw the picture for the second time, how did they find the image in memory and compare it to the incoming image?Certainly not by projecting the stored one into a brain screen, because there is no such screen.And, no matter how they are displayed, what's inside looks at both stored and incoming images—ah!It's that annoying little man again. These are but a few examples of the mysteries of visual perception, and perhaps no field in psychology has yielded so much data and so few definitive answers.Not so long ago, James J. Gibson, a controversial but highly regarded perception theorist, put it bluntly that all that perception researchers have learned over the past few hundred years is "not a good idea of ​​the practical karma of perception." something related and incidental".The perceptual psychologists Stephen M. Koslin and James R. Pomeranz put it more lightly, saying that despite the vast amount of data collected, our understanding of perception is still quite superficial.Plus, they say, "We do know something about it." Indeed, many things—many questions enough to begin to understand it, enough to answer at least some of the interesting questions, leave others out to make room for more convincing some things. For centuries, philosophers have debated whether we are born with the mental ability to make sense of what we see (the Kantian or nativist view) or whether we must learn it through experience in order to explain What is seen (Locke's or experimentalist's point of view).When psychology entered the experimental stage, the findings of perception research not only did not answer this question, but added more evidence to the answer of both.Although today, the terms have been redefined and some of the assumptions have become more complex, so the debate is still ongoing. As we know, Locke and Berkeley, as well as other philosophers and psychologists, sometimes came up with imaginary test cases in an attempt to solve the problem one last time: a man who was born blind suddenly regains sight after surgery or some other intervention.Would he know, without touching the object he was looking at, that the object was a cube and not a sphere, a dog and not a mouse?Or are his perceptions meaningless unless he has learned the true meaning of objects?The experience of such a person holds the key to the matter. In recent centuries, such a number of cases have in fact appeared.The most well-reported example is that of an Englishman.Born with a white cornea, he finally saw the light of day in the 1960s at the age of 52.British psychologist and perception expert Richard L. Gregory called him Mr. SB and studied him carefully. SB is active and extremely intelligent, and he has adjusted well to life after blindness is gone: he reads Braille excellently, uses tools to make objects, and often likes to ditch the usual white guide rods for walks , even if it sometimes bumps into something else, it doesn't matter.He also asked a friend to hold his shoulders to help him ride his bike. By SB's middle age, a corneal transplant was a possibility and he had it done.As Gregory reported, when the straps were removed from the eyes, he heard the surgeon's voice and turned toward him, thinking he must see a face.He saw only a blur. However, experience soon clarified his perception: within a few days, he was able to see many faces, walked along hospital corridors without holding on to walls, and was aware of objects moving past windows It's cars and big trucks.Spatial perception, however, was much more difficult for him.For a while, if he grasped the window-sill with both hands, he thought that the distance from the window to the ground was as far as he could reach with his toes, but in reality, that distance was ten times higher. SB quickly recognizes objects he knows by touch, such as toys, at a glance, but objects that he has never touched unless someone tells him what it is or finds out what it is To him it was something mysterious.Gregory and colleagues took him to London, where he identified most of the zoo's animals, because he had owned cats and dogs and knew how other animals were different from them.But in a science museum, SB sees a lathe - a tool he's always wanted to use - but he can't turn anything out of it unless he closes his eyes and runs his hands around it.Then, having opened his eyes and looked at the thing, he said, "Now I have touched it, so I can see it." Interestingly, when Gregory showed SB some illusions, he wasn't misled by them.For example, he did not see the straight lines in Hering's figure illusion as curved lines, nor did he see the Zellner parallels as oblique lines.These illusions obviously depend on cues that one has learned, since these cues have perspective implications, whereas cues given by other lines in the illusion have no meaning to SB. The conclusions that one can draw from this example are rather disappointing and confusing; some of the evidence is biased towards nativism, and some towards empiricism.Also, the evidence for this is mixed: SB had a lifetime of sensory experience and a learning process through which he was able to explain his first visual perceptions, and his story doesn't show that the mind was primed to understand visual perception prior to experience. What is the degree of awareness.Experimental studies have also not answered this question with infants, because it is unclear to what extent infants' perceptual development at any time is due to maturity, or to experience.Only the impossible experiment of removing the infant's perceptual and other sensory experiences could separate them and measure their relative effects. This is further complicated by the question of whether perception is primarily a physiological or a psychological function. The founders of scientific psychology in the nineteenth century and earlier in this century tried to sidestep this problem by saying that the mind is unobservable, perhaps an illusion, and they had to confine themselves to the study of physiological reality.Those interested in perception have investigated the physiology of the sensory system, especially visual perception, and for more than a century, individuals in Europe and the Americas have collected a wealth of data on how this system works.By the early 20th century, they had determined that each eye's retina, a thin, specialized piece of nerve tissue, contained about 132 million visual receptors of both types cells, rods, and cones, all of which turn light into nerve impulses; rods are more common in the outer periphery of the retina, which are more sensitive and respond only to dimmer brightness, while cones are more common in the retina The heartland, which responds to higher levels of brightness.There are three different cones, one containing primarily a chemical that absorbs short-wavelength light (and thus responds to blue and green colors), and one containing primarily a chemical that absorbs mid-wavelength (green) light , and a third, which mainly contains chemicals that absorb longer wavelengths (yellow, orange, and red). They also figured out much of the intricate wiring diagram through which the cylinders and cones send impulses into the brain.Bundles of optic nerve fibers travel from the retina all the way to the visual cortex, a region lower in the back of the brain.These fibers, which carry information from the left and right halves of each eye's visual field, are sorted and distributed along the way.Information from the right half of the visual area of ​​each eye ends up in the left visual cortex, and information from the left half of the visual area ends up in the right visual cortex. (Why evolution should be arranged in such a crossover way, as of today, no one has been able to tell the fur.) Many psychologists have long been reluctant to accept evidence that visual functions are localized in the visual cortex; such a localization borders on phrenology.In the late 19th century, however, brain localization gained a certain reputation—not in the phrenological sense, but in partial functions—after Winick and Bullock discovered that speech function was located in the two parts of the left hemisphere of the brain. After doing it in a small area.This inspired researchers to search for a brain region that can receive and understand information, and they found this region through autopsy on humans with brain damage and surgery on monkeys. back of the head. The more precise positioning of the visual cortex is a by-product of the armaments of the Russo-Japanese War of 1904-1905.During that conflict, Russia introduced a new type of rifle, the Mauser Model 91, which fired smaller and faster bullets than before.Bullets can often enter the skull without blowing it open, and in some cases, the bullet can partially or completely destroy the victim's vision without killing him.When a young Japanese military doctor treating wounded soldiers mapped the extent of damage to the visual area of ​​each eye for each wounded man, and thus identified the parts of the brain damaged by the entry and exit of bullets, he put the data together, The exact part of the visual cortex was identified. He also found that the size of the visual cortex that receives retinal information is extremely disproportionate to the size of the area that receives retinal image information.A very large portion receives information from the center of vision, the small central area of ​​the retina where vision is sharpest, while a very small portion receives information from the larger peripheral area. (Later research found that the ratio was 35:1.) This solves a big problem: what reaches the brain is not the image on the page that corresponds to the image on the retina. The implications of the discoveries made by the Japanese military doctor and others inevitably slowly became accepted over the ensuing decades.The implication is that retinal cells are "converters" that can convert light signals into a different kind of energy -- bursts of nerve impulses -- and that these "encoded" pulses, or signals, are Sometimes, there is no regress to the image in the visual cortex, despite being "seen" there, or elsewhere in the brain.How they are seen remains a mystery, but perceptual psychologists dodge the question.The way they examine seeing deals only with the flow of nerve impulses and stops abruptly on the edge of thought. Another so-called style of perceptual research - which has only a little edge to perception - is Wundt's traditional approach.Its practitioners studied sensations (immediate and simple responses to sound, light, and touch) which they considered to be reflexive, fundamental, and open to scientific investigation.They also studied the perception of these simple sensations.They ignore, however, all the complex explanatory aspects of perception, which they rightly consider as the result of the processing of sensations by the mind, which they also rightly believe are beyond the scope of objective scrutiny.This approach, popular in the early twentieth century, yielded a wealth of data about sensation, but it added nothing new to the understanding of the psychology of perception. There is another style of perceptual research.That's psychophysics, and it's just the study of mental processes.Fechner and his followers, as we have seen, measured sensory thresholds (the faintest sound, light, or other stimulus a subject could perceive) and the "only ability to notice" between two stimuli. to the difference".When such studies touch on conscious mental processes, psychophysicists say nothing about how subjects notice a stimulus, or how they judge the difference. They stick to objective data—the intensity and What a subject says when they feel or do not feel a stimulus, or a difference between two stimuli.Thus psychophysics was acceptable in the heyday of behaviorism, when feeling was neglected because it assumed a re-existence of the world in the mind, which behaviorists rejected. Psychophysics, however, has been plagued by a perennial problem: subjects were inconsistent in their responses.If given the same threshold stimulus several times, they sometimes saw or heard it, and sometimes they didn't.If light of a certain intensity below a threshold is slowly increased in intensity by the subject, he may begin to see it at a given level, but if the light is emitted above this threshold, then Reduce the intensity of the light, which he may not see at a different level. To solve this problem, psychologist J.A. Switz proposed in 1961 that engineering concepts such as signal detection and information theory should be introduced into psychophysics, concepts that psychologists became exposed to during World War II.Switz and colleagues even gave their method a name that reflects the impersonal and objective nature of engineering—signal detection theory.It first considers that there must always be some random variation in the number of neurons excited by any signal, as well as random variation in the amount of "noise" (irrelevant and occasional firing) entering the nervous system, which may be possible through statistical theory to correct for these variables.Second, it argues that the subject's response to any attempt is partly determined by his expectations and attempts to maximize rewards and minimize costs, variables that can be explained by decision theory. Although "decision making" sounds like a mental activity, "signal detection theory" is outside the mind, predicting the probability of correct and incorrect responses in terms of purely mathematical parameters.Signal detection theory is a major advance in psychophysics, and it is also a part of the standard library of today's experimental methods. However, it only cares about some objective results of perception, and does not shed light on how perception is formed. During this period, however, a small group of psychologists had already begun to explore the internal or cognitive aspects of perception.They are idealists, but not idealists in the metaphysical sense.They, in turn, followed the tradition of James, Freud, and Binet in believing that higher mental processes were central to psychology and could be understood experimentally. In 1897, just as Thorndike and others were beginning to turn to animal experimentation and what would become behaviorist psychology, an American psychologist named George Stratton conducted a humane and apparently It is a perceptual experiment of cognitive nature.For a week, he wore glasses that turned the world upside down, nonstop.At first, he had so much trouble moving around and holding things that he often closed his eyes, relying on touch and memory to help him.However, by the 5th day, he had begun to move freely, and by the end of the week, he felt that things were where he saw them, and sometimes he felt that these things were "just there, rather than the other way around."Eventually, when he took off his glasses, everything was disorienting.For hours, he found himself reaching for objects in the wrong direction; then he regained his grasp of where these objects actually were when they looked normal.Experiments clearly show that spatial perception, at least in humans, is partly learned and therefore relearnable. Surprising as these findings are, the world view of most psychologists in the early decades of this century was anti-idealist, with no appreciation for Stratton's work and little recognition The perception of type was studied until half a century later.By the 1940s, however, several unrelated, cognitively oriented branches of psychology—Freudian psychology, Gestalt psychology, personality studies, and the fledgling social To gain strength, some psychologists who think these theories are right for their own mind also take a different approach to perception than psychophysiology and psychophysics. In the United States and elsewhere, some have rediscovered Stratton's work and experimented with new vision-distortions. In 1951, Austrian psychologist Evo Köller convinced volunteers to spend 50 days seeing the world through a prism eye patch that deflected their vision about 10 degrees to the right and slightly bent vertical lines.His subjects felt for a few days that the world was unstable and had difficulty walking and doing simple things, but after a week to ten days, most things seemed to them back to normal, After a few weeks, one volunteer was even able to skate.Like Stratton, they felt disoriented after removing the blindfolds, but quickly regained normal performance. Some other psychologists revived the study of illusions, which had been neglected for a long time, and by the 1950s, illusion studies had become a hot research project again.The most prominent subjective triangle in Figure 21 was invented in 1950 by the Italian psychologist Gitano Canesa.It is just one of many new optical illusion images used to investigate visual mental processes.A particular optical illusion is also used to explore psychological interpretations of ambiguous characters.The following classic pattern was invented by Pauline in 1930. People can look at this picture as they like. It can be an old witch turned slightly towards the observer, or her face is turned slightly away. of a young woman. The ability of people to be able to see two ambiguously different images, or in some figure-background reversible models like the Rubin Vase, cannot be known No mechanistic theory of physiology can explain it, says British psychologist Stuart Anstice, but it is the result of higher perceptual processes. [Some perception researchers attribute this reverse effect to neural saturation (retinal fatigue from one image so that another image replaces the original).However, this does not explain why we are free to switch between the two images at will. It is the same reason that the mind can accept, or be surprised by, the "impossible" invented by some perceptual psychologists in the 1940s and 1950s.We give a few such examples below.It is the mind, not the retina, the optic nerve, or some special cell in the neural cortex, that is interpreting a cue that it thinks it is a picture of an object and at the same time feels that such a thing cannot exist in the real world. Another cognitive approach to perception was conceived by several American psychologists who, starting in the 1940s, sought to discover the ways in which needs, motivations, and mental settings affect perception.Two of the better leaders in this area, Jerome Bruner and Leo Postman of Harvard University, showed young children toys and simple building blocks, each 3 inches high.They then asked the children to judge the size of the objects, and the children thought the toy was taller.Later in these experiments, they told the children that they could keep the toys, only to say no after a while.When these toys are out of reach, the children see these toys even bigger than they are.When other researchers asked hungry and non-hungry subjects to estimate the size of the food, the hungry people saw the food larger than the non-hungry people.These experiments, and similar ones, show that needs, desires, and frustrations influence perception. According to other studies of the same period, the same is true of certain traits of character.Ilse Frankel-Branswick, a psychologist who was educated in Vienna and then came to the United States, rated a group of children on levels of racial prejudice, a trait she says is incompatible with a blunt "authoritarian personality type" There is a close connection.She then showed the children a picture of a dog, followed by a series of transitional pictures in which the image of the dog slowly changed into a cat.Children who rated high on prejudice tended to think the pictures were of a dog for a longer period of time and were less resilient than those who scored low on prejudice.The same was true when she asked the children to identify a series of pictures in which colors varied from one depth to another. Other cognitive studies of perception in the 1940s and 1950s also explored "perceptual defenses"—psychological resistance to seeing something unpalatable.The researchers flashed some words on the screen quickly (about one hundredth of a second) using a speed-rotating stereoscope, and found that the subjects could recognize more neutral words than taboo words.当实验者为男性，受试者为女性时，效果最为明显。有一个小组用速转实体镜显示出一些与成就相关的词汇，如“竞争”和“掌握”，还有一些中性词，如“窗户”和“文章”；通过亨利·默里TAT法测试为极想成功的受试者认出与成就相关的词汇的速度，比认出一般中性词汇的速度快些。 心理设定，或者叫人们对可能看到的物体的预期，是这种研究的另一个课题。布鲁纳和波斯特曼利用速转实体镜让受试者们快速地看一些扑克牌，大部分牌都是标准的，可其中一些不是标准的，比如红色方块四。习惯和预期使28位受试者中的27位认为不正常的那些牌也是正常的，可是，一旦受试者了解情况后，他们的心理设定就发生了改变，辨认扑克牌时出错的机会也减少了。 到1949年，这类的研究非常之多，心理学家们从当时的流行女装中借来了一个词，他们谈到了知觉研究中的“新面孔”。在约10年的时间里，新面孔红极一时，收集了大量资料，涉及需要、动机和心理设定对知觉产生影响的范围。然后，因为缺少详细的理论，以解释这些东西发生的过程，这场运动最后也偃旗息鼓了。 可是，一种更新、更有威力的理论，即信息处理，也已经开始转变认知心理学了。这种理论认为，有一系列有序的过程，感觉是通过这些过程传递到思想，思想也是这样传递到行动中的。这种理论假定（并提出了实验证据）有一系列步骤的感觉输入变形，包括在感觉器官中暂时的记忆存储，编码变成神经冲动，在思维中短期存储，再用熟悉的物质进行检索或者连接，长期记忆力存储，检索等等。这个理论使心理学家能够具体地处理思维如何处理进入的感觉材料，而且，它还恢复了对知觉采取认知方法的兴趣。到70年代，这在认知领域里的研究已经结出了丰硕的成果。 可是，这时候，对于知觉的生理学已经有许多有意义的发现。从那以后，观察看这个动作的两种风格，即生理学和认知法，就并存一起了，它们表面看上去彼此对立，实际上都集中于同一些现象的不同方面，从现在起，我们会看到这些情况。 我们是怎样看见物体的外形的？这个问题好像根荒谬——我们怎么能不看见事物？可是，对外形的知觉既不是自动的，也不是完全不出错的。我们在晚上看见黑暗中一个阴影般的东西，不知道它是一片草丛还是潜伏在那里的一个人；我们看着一个签得十分潦草的签名，不知道这个签名到底是以C，G还是以O开头的。我们坐了很长时间的飞机后疲惫地回家，看见空荡荡的机场停车场里停着我们的车，然后拖着疲惫的身体朝它走出去，可到跟前时才发现，这只是跟自己的车看上去差不多的另一个牌号的车。我们很喜欢玩拼图游戏，就是因为我们觉得这游戏很难做，当我们把最后一片东西装到自己刚刚空下来的一个边子上的时候，我们会感到愉快。 对外形知觉进行的研究是想辨认出一些机械原理，既是神经学上的，也是认知理论上的。它会帮助我们辨认各种外形——而这一点却时常使我们感到为难。在过去的半个世纪里，这方面进行的很多研究都采取了认知的方法。格式塔学者们及其追随者探索了思维的倾向，如将有关联的元素集中在一起，变成一个连贯的整体；在我们看到的间隔之间填入衔接材料，从背景中辨别物体等。他们，还有其它一些人都还说，是人天生的高级心理过程在解释“恒定现象”——我们看事物的时候倾向于不变，哪怕视网膜的图象已经发生了扭曲，正如我们看见一本书从某种角度斜躺在我们面前，就好像它还有一些方方正正的角，哪怕在视网膜或者照相机里，这书看上去一定是一个偏菱形的东西，有两个锐角和一个钝角。 可是，这些知觉是结果，而不是过程。思维是通过什么样的一些步骤看到这些东西的呢？我们说，我们会把我们看到的一些很熟悉但不完整的形状之间的间隔填满，这是一回事，但是，要确定我们是通过哪些具体的办法来做到这一点的，这却又是另外一回事。以很详细的细节探索视觉信息的认知过程的最新研究已经找到了一些过程。下面就是这些发现的例子： ——对主观轮廓现象的研究（如上述图21中的错觉三角形）表明，我们一方面是通过联想（这三个角使我们想起以前见到过的某些三角形）来分析出这个想象的周边的，还有一部分是通过提示，即经验告诉我们要加以插补的的地方（一个物体挡住我们看见另一个物体的视线）。如知觉研究者斯坦利·科伦在1972年进行的一项研究中指出的，圆圈和图21已经存在的三角形中的间隔表明，某些别的东西——即错觉的三角形——挡在视线里，挡住了它们。由于明显的插入，思维“看见了”想象的三角形。 ——有些实验探索了我们如何辨认一个我们正在寻找的东西的外形，特别是当这个东西丢失在其它有外形的东西里面时。有一个重要的过程是“特征检测”——有意识地寻找某个特定的外形已知和可辨认的一些元素，以从类似的物体中区分这个东西。在下面这两栏字母中，各有一个Z在里面。如果你用秒表计时，看在哪一栏里找对象词快些，你会发现，在第二栏里找到这个词比在第一栏里快多了。 XEIMWV ODRUQC XIEWMV QCURDO VXIEWM OQCURD MVXIEW DOQCUR WMVXIE RDOQCU EQMVXI URDOQC IEQMVX CURDOQ XIEMWV QUCRDO WVZXIE DOZQUC MVXIEW DOQUCR WMVXIE RDOQUC 按照科伦及其同事（这两个栏目就是从他们的书中找出来的）的说法，将Z这个从记忆里面找出来的模式与我们正在寻找的东西相比较这个任务，当藏起来的Z这个字母是在圆形字母中时，找起来比它藏在由像Z本身一样的直线和角构成的字母中时容易得多，也快得多，因为在后者的情况下，我们得注意一些细小的差别。或者，如另一种解释所言，我们在寻找视觉图象时，经常会以“预注意”过程来进行，即与总体的图象相关的自动过程，可是，如果这个不行，我们就转移到“集中的注意力”上来，并有意识地寻找要找的这个东西细小的区别性特征。 ——1954年，俄勒岗大学的弗雷德·阿特尼夫请一些受试者用10个点来表示一些图形，他们倾向于把这些点放在一些使轮廓的方向转变最明显的地方。阿特尼夫的结论是，我们辨认模式的一个方法是通过对其“变化点”的分析进行的。他还画了一些图，这些图与现实中的实物相比已经做了极大的简化，是从一个变化点向另一个变化点来画直线的。尽管这使曲线变成直线，可是，图形还是立即能够辨认出来，如在下列中： ——懂技巧的阅读者把词汇当作一个整体看，而不去一个字母一个字母地辨认，而刚开始读书的人却是一个字母一个字母地看的。可是，哪怕是在快速的阅读中，还是有很多高速特征检测活动在进行着，如由艾林娜·J·吉布森（上述提及的詹姆斯·吉布森的妻子）和同事60年代在康奈尔大学进行的一些实验所显示的一样。他们生造了一大批根本不存在的单音节，其中一些符合英语拼音规则，因此是有可能发音的（“glurck，”“clerft”），然后把辅音组调来调去以生造另外一些音节，虽然字母是同一些，可违反了发育规则，因此无法发音（“rckugl，”“ftercl”）。当有技巧的阅读者在快速实体镜中看到这些词时，他们辨别合法组合比非法组合容易得多，尽管这些字母组都是不认识的词。一种可能的解释是，他们自己给这个词发音，因而更有可能将可发音的一些音节放入短时记忆中，而不可发音的音节就不行。可是，吉布森在加罗戴学院的聋哑儿童中进行试验，因为他们从来没有听到过人念单词，她得到的结果还是一样的。这只能意味着，在感知一个假词时，阅读者区分了这些字母，并且立即辨认出，哪些组遵守了合法的英语拼写模式规则，哪些没有。 ——在50年代晚期和60年代早期，欧文·罗克，一位后来成了知觉研究领袖人物的心理学家给受试者看一个倾斜了45度的方框，然后问他们说看上去像什么；他们说像钻石。然后，他让这些受试者也倾斜45度，使图象在他们的视网膜上呈方框图形。可是，他们是在一间屋子里，在屋子的参照下，知道哪一个被倾斜了。有了这两个信息来源，经过大脑的处理以后，使他们还是把方框看成一块钻石。这个简单的实验极大地影响了罗克对于知觉的认识，并使他得出结论说，除非知觉现象在一个心理视点上经过了分析，否则，在一个神经生理学的水平上来做这个工作是不成熟的。 可是，从40年代起至以后，神经生理学家们已经得出了有关视知觉的大量发现，这些发现对认知学家们也同样有着重大的意义。早在30年代，他们就已经能够记录小组神经细胞的电活动了，到40年代，实验室研究者们已经完善了装有电极的玻璃探针，其程度如此之精细——其顶端细如发丝，其直径兴许只有千分之一厘米——它们可以插入视网膜的单个细胞、膝状关节或者经局面部麻醉后插入猫或者猴子的视皮层里面去。有了这种仪器，研究者们就可以观察单个细胞在给动物照光或者进行其它显示时的电子释放情况。 这种技术给外形知觉带来了历史性的发现。50年代晚期，哈佛医学院的两位极聪明的神经生理学家大卫·胡贝尔和托恩斯顿·威塞尔测试了猫的视皮层细胞反应。他们把微电极埋在猫的视皮层中的细胞里，尽管他们不能选择某个特定的细胞，可是，他们可以把电极以大约正确的方式插在它们大约正确的地方，因此可以了解它们到达了什么地方。威塞尔有一次把这个过程比作用牙签在碗里刺樱桃。你可能不知道要刺中哪一只，可你知道一定会刺中一个。研究者在屏幕上打出一阵光或者一些光栅或者其它图形时，猫会用带子束好。把猫的头用东西固定好，研究者们就可以知道视网膜上的哪一个部分是图象落在上面的地方，并把这个与被刺进的皮层区域进行连接。通过放大器和扬声器，他们可以听到细胞启动的声音。安静的时候，细胞每秒可能会发出几声“卟卟'声，可是，当它受到刺激时，它会以每秒50或100个卟卟声不停地响。 由于视网膜和皮层都有比较复杂的结构，发现哪些细胞，在什么地方和在皮层的哪一层对来自视网膜的不同区域的信息产生反应，是一件极费耐心的事情。1958年的一天，这项令人极为痛苦的精细工作终于得出了令人惊讶和半是偶然的结果。胡贝尔和威塞尔已经把一根电极插在一个细胞里面了，可是，在几个小时的时间里，它并不能引发快速的启动。如胡贝尔几年以前回忆的： 为了让细胞启动起来，除了用脚踩我们自己的头以外，我们尝试过了无数的办法。（不时会有一阵间歇性的响动，因为大部分皮层细胞都会这样，可是，我们花了很多时间来证明，是我们施加的刺激引发这些活动的。）为了刺激细胞，我们使用的大部分都是白色和黑色的圆点。可是，在5个小时的斗争之后，我们突然产生了一个印象，上面带有「黑」点的玻璃偶尔会产生一种反应，可是，这种反应好像与这个点没有什么关系。最终，我们想到这一点了：在我们把幻灯片插入槽中时，是玻璃[幻灯]片边子上很尖锐但又很模糊的阴影在作怪。我们很快使自己相信，这条边只有在其阴影扫过视网膜上一个较小的部分时才起作用，扫描时应该让边子对着某个特定的方向才行。 简而言之，细胞对一个横向的线或者边有强烈反应，但对一个点、一条斜线或者一条竖线只有非常微弱的反应，或者根本就没有反应。 胡贝尔和威塞尔（及其他研究人员）继续表明，有些其它的细胞对某些处在一个角度上的线条、或者对垂直线条或者对直角或者对明显的边际都有特别的反应（在这里，一个物体与其周围的东西有一种对比）。很明显，视皮层的细胞是非常专业化的，它们只对视网膜上的图象的某些特定的细节有反应。胡贝尔和威塞尔为这项研究，以及其它相关的大脑研究而获得了1981年的诺贝尔奖。 有可能通过一个简单的试验来体验一个人自己的线条检测器神经元。支起这本书来，看着下面三个图案，然后慢慢朝后退。约在6英尺远的地方，你仍然能看见竖线和横线，可是，中间圆里的横线会成为一块模糊的灰色。知觉研究者把这叫做“斜线效应”。 有趣的是，尽管这是生理学上的，可有一部分也是后天学习得来的。在1970年进行的一项实验中，把一窝猫放在一个竖直的笼子里面养着，里面贴满竖条，从不让它们看见横条。5个月后，当对它们进行视力测试时，它们看不见横条或者横向的物体。神经学解释是，对横向线条作出反应的皮层细胞在小猫早年生活的阶段停止了发育。同样地，在城市长大的人在童年早期看见坚线和横线的机会多些，而看见其它方向线条的机会相对就少些，因而，他们对前者的反应就灵敏一些。一个研究小组对一组在城市长大的大学生，和一组在传统的帐逢和房屋里长大，很少看见横向和竖向线条的克里印第安人进行测试。在城市长大的大学生表现出了斜线效应，而克里人却没有。 固定不变地看着下面这个图案的中心，也可以体验你的视网膜上竖直、横向和斜向检测器细胞的专业性： 你看到的旋转和抖动，也许是因为，当你看着中心时，不同角度的光线都靠得很近，眼睛不断的移动使视网膜上的图象从一种角度的线条跳到另一根线条上，从而发出一大堆信号，使专业化的、有方向性的敏度皮层接受器产生了混乱。 微电极法使神经生理学家们能够解释视皮层的建筑——神经元是竖向排列着的，一栏里面约有100个，而且分层排列，一层层地穿过各栏——并能测量视皮层里面每一个部分的神经元对广泛刺激的反应。结果，人们得出了视皮层各个不同部分的不同细胞详细的图景，它们如何区分各种外形，亮度、色彩、运动和深度提示的对比。极为复杂的神经元对神经元，神经栏对神经栏的突触连接，把所有这些细胞的反应连接起来，给大脑提供视网膜上的图象这样一个复杂的编码信息。 这个集中起来的信息是在什么地方和怎样被思维“看见”的，这一点尚不太清楚，不过，从认知型知觉研究中可以明显地看出，视觉皮层专业化的反应不是最终的产品，至少在人类中不是如此。在简单动物中，神经反应也许足以产生合适的行动（要么逃跑，要么攻击）。在人类当中，神经信息经常是毫无意义的，除非这些信息得到认知过程的解释。在错觉三角形的例子中，观察者的思维，而不是皮层细胞，可以提供这个图象缺少的部分。其它许多不完整或者降级的图象也是这样的，观察者有意识地唤起较高级的心理过程，填入缺损的部分，然后看到一个根本就不在那里的东西。这里有一个例子： 一开始，大部分人会把这个图案看作一个毫无意义的黑块排列。反向的白色部分和里面藏着的那个字是怎样看出来的，这一点尚不清楚，可是，一旦看出来以后，思维几乎就再也不能认为这个图形是一些无意义的黑块了。 把眼睛当作照相机这个比喻的意思是，我们是以快门的方式来观察事物的，可是，我们的视觉经验是一种不间断运动的体验。的确，通过环境和环境中移动的物体来感知我们的运动，这是观察当中最为重要的一个方面。没有运动知觉的视力几乎是无价值的，也许比没有视力还要糟。这可以从1983年《大脑》期刊报道的一例罕见的个案中看出来。 病人是位妇女，因为严重的头疼、晕眩、恶心，最严重的是失去了运动感，这使她处处不便，因而住院。做脑电图和其它体检显示，她主要的视觉接受区域外的大脑皮层的一个部分有损伤，这个区域已知是对运动感觉至关重要的。报告摘抄如下： （她）失去了所有三个层面的运动视觉。比如，倒茶和咖啡时都有问题，因为这些液体看上去都像结了冰，就像一层冰块。另外，她也掌握不了倒水的时间，因为水快要倒满时，她不能够感知杯子（或壶）里面的运动……在有别人走动的屋子里，她感觉很不安全，很不舒服，而且很快就离开房间，因为“人们很快地走到这里或者那里，可是，我看不见他们的移动”……她不敢走过街道，因为她无法判断车辆的速度，可是，她可以很轻松地看到汽车本身。“当我首先看到车辆的时候，它好像在很远的地方。然后，当我准备穿过街道时，汽车突然就在很近的地方。” 哪怕没有这些证据，我们都可以判断出，运动视觉是极为重要的。我们对自身移动的感觉指导我们在环境中走动；对向我们移动而来的物体的感觉，使我们能够避开危险；我们对手的移动的感觉，给我们提供对何时伸向物体或者做一些精细手工活至关重要的数据；站着的时候，对我们身体精细运动的感觉使我们知道挥舞双手或者不要失去平衡。（如果你双脚并在一起站着，然后闭上眼睛，你会发现很难站得极稳。） 在过去的半个世纪里，很多对动知觉的研究都是处理外部的变量的：移动物体的大小、速度、位置和其它特点是如何影响它们在我们看上去的样子的。这样一些研究与心理物理学是差不多的：它获取一些客观数据，但对于经验的内部过程却只字不提。尽管如此，它提供了这些过程的重要提示，一方面是天生的神经过程，另一方面是获取的认知过程。 一项有关天生的低水平过程典型的发现：研究者在婴儿面前把一个阴影或者盒子样的图象打在屏幕上，然后让阴影或者图象快速地扩张。当图象扩大时，婴儿朝后靠一靠，就好像要避免被撞上一样。这个反应不是经验的作用，一个从没有被快速接近的物体撞上过的新生儿会以这种方式作出反应，就跟许多没有经验和新生的动物一样。这种对“快速放大”的物体作出的避开姿势，很明显就是一种保护性的反射，它是通过进化传达给我们的；一个快速接近我们的物体的视觉图象会触发回避的行为，它不涉及到任何更高的精神过程。 有关获取的高级过程的典型发现是：1974年，心理学家戴维·李和埃里克·阿伦森做了一个没有地板的小房间，它可以通过一块不能移动的地板从这里或者那边溜过去。当他们把一位13一16个月大的、刚刚学会走路的婴儿放在里面，然后偷偷把这个房间朝着婴儿面对的方向溜过去时，也就是说，从孩子面前溜走——这个孩子会向前扑过去，或者跌倒；如果他们把房间朝另外一个方向溜过去，孩子会朝后跌倒。这个解释是，当墙壁移走时，孩子感觉到，好象他或者她在朝后倒，因此自动地通过向前倾倒而加以补偿，反过来亦是一样。这好像是一种获取的行为。孩子在开始走路时，会学会使用“光学流动”信息。（光学流动是我们移动时反映在我们视野范围内的任何东西的移动。比如，当我们走向某个点时，其周围的任何东西会向外扩大，直到视野的尽头。） 这些，以及其它一些有成果的移动知觉研究，把长期以来认为眼睛是照相机的这个观点里更多的缺陷暴露了出来。其中一种缺陷是，尽管眼睛没有快门，可是，移动的物体并不会引起模糊，如我们在照相时，照相机在曝光时的移动并不会使我们看到一个模糊的东西。相应地，很多对移动感觉的研究已经在寻找发现为什么没有模糊的原因。一种不断得到同意的假设是以乌尔里克·赖塞尔和其它一些人的研究为基础的，即，当我们看到一个图象通过速转实体镜在屏幕上闪动哪怕多少分之一秒时，我们事后可以在思想里面粗略地看到它。1967年，赖塞使用“图标”这个词来形容这个非常短暂的视觉记忆，他测量它的持续约为半秒钟（后来的研究报告说只有四分之一秒）到2秒，并发现，如果新的模式在它完全消失以前出现的话，它就会被擦掉。其它一些视觉研究者们因此而认为，由于眼睛扫过视野或者以一系列叫做“飞速扫视”的跳跃方式跟踪物体，它在物体移动时什么也看不到，可是，在每一次短暂停留时，它会发出一个图标式的快照给大脑。这些快照都汇集在一起，变成了一种运动知觉，有点像看电影。 这种假设在70年代和80年代早期被广为接受。可是，一些处于先进行列的调查者开始怀疑，图标只是在不自然的实验室条件下观察到的，它不一定存在于正常的知觉之中。果真如此，有关移动知觉的飞速扫视——图标假设就会崩溃。拉尔夫·哈伯是这样看的： 在自然状态下是没有这样一些表现的，除非你想在闪电中阅读。没有自然的一种情形是视网膜可以在约四分之一秒的时间里受到静态刺激的，因为它的前后都是一片黑除……从来没有一个固定的、像快照一样的视网膜图象固定在时空中，而只有持续变化着的图象……图标是在实验室里诞生的，且只存在于实验室，而不可能存在于别的任何地方。 眼睛的屏幕不是一种感光剂，它上面移动的图象并不是以静止物的形式被捕获而不模糊的。反过来，视网膜是一种由成百万接收器构成的组织，当受到刺激的时候，每一个接收器每一秒钟启动的次数有好多次。当一个图象在视网膜上通过时，从一连串接收器上产生的连续脉冲流会向前进入视觉皮层。没有模糊不清的地方，因为这个系统生成的不是一连串静止的东西，而是一种不间断的、不断变化的信息之流。 的确，仅只在30年前才有的一项有关移动知觉问题的戏剧性发现是，视网膜和视觉皮层里的有些神经元会对移动作出反应，可是，其它的许多神经元却不会有反应。移动的检测在单细胞水平上开始。这个古老的进化性发展有助于一些猎物避免被吃掉，也有助于一些捕食者发现和抓住猎物。一只青蛙会有效地捕捉住任何小的移动物体，不过，如果只给它喂死苍蝇或者死虫子，它就会饿死，因为它不会认为这些死东西是食物。其它许多简单动物显示了相类似的行为。青蛙的视网膜和大脑明显具有一些可以对移动（和大小）作出反应的神经元，这种能力具有比视觉方面意义更大的生存价值。 在60年代和70年代，胡贝尔和威塞尔及其它人都显示了移动知觉器的存在。他们显示，当他们利用电极法记录老鼠和猴子的单细胞的活动时，视网膜和视觉皮层中的某些细胞，而且只有这些细胞，会对移动作出强烈反应。事实上，有些只对一种方向上的移动作出反应，有些对另一方向上的移动作出反应。 其他一些调查者通过完全不同的方法确证了这一点。1963年，罗伯特·塞库拉及一位同事将一只向上移动的栅栏投影，他们确立了人类受试者可以看见物体移动的临界值（最低速度），然后让每位受试者稳定地看着移动的物体。几分钟以后，受试者在栅栏以原来的临界速度慢慢走动时再也不能看见它移动了，不过，如果速度提高一倍，他们仍然能够看见它移动，而且还能够在更慢的速度上看见它向下移动。结果表明，有向上移动的检测器，它已经疲倦了，还有向下移动的检测器，而这些检测器却没有疲倦。比较结果以相反的方式得到，受试者这时候观察一个向下移动的栅栏有好几分钟。 我们大多数人都经历过移动检测器疲倦而不知道它的神经元基础。如果我们盯着一道瀑布长时间地看（或者其它长时间连续移动的物体，如生产流水线），然后扭过头去，我们会看见向相反方向的移动错觉。以高速对一个方向上的移动作出反应的细胞会暂时疲倦，而且不再产生反应，这时，对向另一个方向的移动产生反应的细胞却会不断地以其正常的低水平这样做，并以它们喜欢的方向临时产生一个移动感觉。 然而，这些都没有解释清楚其它两种移动知觉的未解之谜。如果我们移动眼睛或者头脑去追随一只飞鸟，或者其它移动的物体，我们会感觉到移动，哪怕这个图象在视网膜的中心保持不动。反过来，如果我们移动眼睛，图象会扫过视网膜，可是，我们会看到一个静止的世界。 那么，一定就是一些其它的信息来源来确认或者纠正来自视网膜的信息。自上个世纪以来，已经提出了两种可能性：要么大脑向眼睛和头脑发出了移动命令，以便使一个移动物体的图象保持在视网膜中心位置，要么眼睛和头的移动本身延缓进入视觉皮层，并在那里被解释为这个物体的移动。同样，当我们扫瞄一个静止的背景时，要么是大脑的命令，要么是眼睛的移动在向视觉皮层发出信号，以使它把移动视网膜图象当作一个末移动场景的图象。 这个问题尚没有得到解决，用动物进行的实验室实验为每种理论提供了一些证据。通过一种或者另一种方法，眼睛和头移动会提供一部分对于移动知觉至关重要的信息。对余象的研究证明了这一点。如果受试者盯住一个明亮的光线看～会儿，当扭开头去看一个相对黑暗的地区时，他们会看到光线的余象。如果他们移动眼睛，余象会在同一个方向上移动，尽管余象的来源，视网膜上已经疲倦的区域并不会移动。这意思是，视觉皮层尽管接受到眼睛在动而图象并没有在视网膜上移动的信息，可是，它还是会解释它们，并把它们当作眼睛在跟踪一个移动图象来解释。 另一项实验也证明了这一点，是在50年代由一位名叫冯赫尔斯特的德国人进行的。他暂时使一位志愿者的眼肌瘫痪，这样，眼睛就不能向左移动，然后告诉这位志愿者，让他朝这个方向移动。眼睛并没有移动，可是，观察者却看见物体在朝这个方向移动。接下来，他机械地使眼睛向左移动，果如所料，观察者看见视野向右移动。最后，他告诉观察者将瘫痪的眼睛向左移动，同时机械地将它移向右边，志愿者完全看不到移动，因为两种影响互相抵消了。