The Mind's Eye

2. Our other two brothers seemed to have normal powers of facial recognition. My father, a general practitioner, was immensely gregarious and knew hundreds of people, not to mention the thousands of patients in his practice. My mother, in contrast, was almost pathologically shy. She had a small circle of intimates—family and colleagues—and was very ill at ease in large gatherings. I cannot help wondering, in retrospect, if some of her “shyness” was due to a mild prosopagnosia.

3. A most remarkable and creative reaction to face-blindness—the word “compensation” seems inadequate—is that of the artist Chuck Close, who is famous for his gigantic portraits of faces. Close himself has severe lifelong prosopagnosia. But this, he believes, played a crucial role in driving his unique artistic vision. He says, “I don’t know who anyone is and have essentially no memory at all for people in real space, but when I flatten them out in a photograph, I can commit that image to memory in a way; I have almost a kind of photographic memory for flat stuff.”

4. It is similar with milder degrees of colorblindness or stereo blindness. People may be unaware of these “deficits,” considering themselves normal, until the deficit is revealed through, for example, a routine eye examination or driver’s license test.

5. Once, as I was being interviewed on the radio about The Man Who Mistook His Wife for a Hat, a listener phoned in and said, “I can’t recognize my wife, either.” (This, he added, was because he had developed a brain tumor.) I arranged to see Lester C. and find out more about his experiences.

While Lester had found various strategies for recognizing people, he told me, he was distressed by his inability to appreciate the beauty of faces. He had had “a great eye for the girls,” he said, before the tumor. Now he had to judge beauty indirectly, by taking seven criteria (color of eyes, shape of nose, symmetry, etc.) and rating each of these on a scale of one to ten. This way he could construct a “mental histogram,” as he put it, for beauty. But he soon found that such histograms did not work and were sometimes ludicrously at odds with a direct or intuitive judgment of beauty such as he had once had.

Most people with prosopagnosia remain sensitive to facial expressions, seeing at a glance whether someone looks happy or sad, friendly or hostile, even though the faces themselves may be unidentifiable. The reverse also occurs: Antonio Damasio has described how people with damage to the amygdala (a part of the brain crucial to the perception and feeling of emotion) may have difficulty “reading” faces, judging their emotional expressions, even though they recognize faces normally. This may also be the case with some autistic people. Temple Grandin, who has Asperger’s syndrome, says, “I can recognize major expressions on a person’s face, but I do not pick up subtle cues. I did not know that people had little eye signals until I read about them in Simon Baron-Cohen’s book Mindblindness when I was fifty.” (Though Temple is a “visual thinker” and can easily visualize complicated engineering problems, she seems to be no better or worse than average at recognizing faces.)

Difficulty making social contact with others can also be a central problem in schizophrenia, and Yong-Wook Shin et al. have obtained preliminary results suggesting that schizophrenic people have difficulty not only in reading facial expressions but in face recognition, too.

6. Determined to provide some objective correlate, Gall went further, trying to measure and correlate personality and moral faculties of individuals with the shapes and bumps of their skulls, using a method he called “cranioscopy.” One of his students, Johann Spurzheim, went on to popularize this idea as “phrenology,” a pseudoscience that gained much attention in the early nineteenth century and influenced Lombroso’s theories of criminal physiognomy. Spurzheim and Lombroso’s work has long been discredited, but Gall’s idea of localization in the brain had a lasting impact.

7. In 1869, Hughlings Jackson debated this issue with Broca, insisting that “to locate the damage which destroys speech and to locate speech are two different things.” Jackson, it was generally thought, lost this debate, but he was not the only one with reservations. Freud, in his 1891 book On Aphasia, suggested that the use of language demanded many interconnected areas of the brain, and that Broca’s area was only one node in a vast cerebral network. The neurologist Henry Head, in his monumental 1926 treatise Aphasia and Kindred Disorders of Speech, inveighed against “the diagram-makers,” as he called the aphasiologists of the nineteenth century. Head argued, as Hughlings Jackson and Freud had, for a much more holistic view of speech.

8. Much that we now take for granted in neuroscience was very unclear when Gross began this work. Even in the late 1960s, it was widely believed that the visual cortex did not extend far beyond its main locus in the occipital lobes (as we now know it does). That the representation and recognition of specific categories of objects—faces, hands, etc.—might rely on individual neurons or clusters of neurons was considered improbable, even absurd; the idea was good-humoredly mocked by Jerome Lettvin in his famous comments about “grandmother cells.” Very little attention, therefore, was paid to Gross’s early findings, and it was not until the 1980s that they were confirmed and amplified by other researchers.

9. Different inferotemporal cells, they write, are “selective for different face parts and interactions between parts, and even the same cell can respond maximally to different combinations of face parts. Thus, there is no single blueprint for detecting the form of a face. . . . This diversity of feature tuning provides the brain with a rich vocabulary to describe faces and shows how a high-dimensional parameter space may be encoded even in a small region of [the inferotemporal cortex].”

10. Koch, Fried, and their colleagues have published many papers on their work; those most relevant here include Quian Quiroga et al., 2005 and 2009.

11. Yoichi Sugita points out, however, that this narrowing is easily reversible, at least in childhood, by experience.

12. Despite its unfamiliarity to modern physicians, congenital prosopagnosia entered the medical literature as early as 1844, when A. L. Wigan, an English doctor, described one of his patients:

A gentleman of middle age . . . lamented to me his utter inability to remember faces. He would converse with a person for an hour, but after an interval of a day could not recognise him again. Even friends, with whom he had been engaged in business transactions, he was unconscious of ever having seen. Being in an occupation in which it was essential to cultivate the good-will of the public, his life was made perfectly miserable by this unfortunate defect, and his time was passed in offending and apologizing. He was quite incapable of making a mental picture of anything, and it was not till he heard the voice, that he could recognise men with whom he had constant intercourse. . . . I endeavoured in vain to convince him that an acknowledgment of the defect would be the best means of removing the unfortunate effect it had produced in alienating friends. He was quite determined to conceal it, if possible, and it was impossible to convince him that it did not depend solely on the eyes.

13. Information is available at their website, www.faceblind.org.

Stereo Sue

1. Wheatstone’s name is more commonly associated with the invention of the Wheatstone bridge, an instrument used to measure electrical resistance. But like several other eminent nineteenth-century scientists, Wheatstone was also deeply interested in the physical basis of perception. All of these “natural philosophers” (we would now call them physicists), using ingenious experiments, contributed to our understanding of how the eye and brain construct our perceptions of depth and movement and color, as they also contributed to the technological development of stereo, cinematic, and color photography.

Michael Faraday, in addition to his electromagnetic studies, played a part in devising zoetrope-like instruments that presented a series of still drawings to the eyes in rapid succession, demonstrating that at a critical rate these could be fused by the brain to create a sensation of motion.

James Clerk Maxwell was intrigued by Thomas Young’s hypothesis that there were three—and only three—distinct types of color receptors in the retina, each responsive to light of a certain wavelength (roughly corresponding to red, green, and blue). He devised an elegant test of this by photographing a colored bow through red, green, and violet filters and then projecting the three photographs through their corresponding filters. When the three monochromatic images were perfectly superimposed, the picture burst into full color.

2. By the mid-1850s, a subspecialty of stereo photography, stereo pornography, was already well established, though this was of a rather static type, because the photographic processes used at the time required lengthy exposures.

3. There is one situation, as I learned by painful experience, when two eyes do not help. When I was growing up, we always had a clothesline strung across the garden, and since it traversed the entire visual field horizontally, it appeared exactly the same to both eyes, and I could never judge how far away it was. I had to approach it cautiously, since it was strung rather low, at about the height of my neck. Sometimes, forgetting this, I would run straight into it, almost garroting myself.

4. Richard Gregory, who studied visual illusions for many years, insisted that perceptions were, in fact, perceptual hypotheses (as, in the 1860s, Hermann von Helmholtz called them “unconscious inferences”). Gregory was a stereo enthusiast—he often sent his friends stereoscopic Christmas cards—but when I spoke to him about seeing faces as hollow masks, he was very surprised. With something as familiar and crucial as a face, he thought, probabilities and context would weigh the odds heavily against such a radical misperception. I agreed, but could not gainsay my own experience, and Gregory had to concede that such an improbable phenomenon might indeed occur in someone who is strongly biased towards binocular cues.

5. In The Forest People, Colin Turnbull described driving with a Pygmy man who had never left the jungle before:

He saw the buffalo, still grazing lazily several miles away, far down below. He turned to me and said, “What insects are those?” At first I hardly understood; then I realized that in the forest the range of vision is so limited that there is no great need to make an automatic allowance for distance when judging size. . . . When I told Kenge that the insects were buffalo, he roared with laughter and told me not to tell such stupid lies. . . . As we got closer, the “insects” must have seemed to get bigger and bigger. Kenge kept his face glued to the window, which nothing would make him lower. I was never able to discover what he thought was happening—whether he thought that the insects were changing into buffalo, or that they were miniature buffalo growing rapidly as we approached. His only comment was that they were not real buffalo, and he was not going to get out of the car again until we left the park.

6. More rarely, stereopsis may be lost, sometimes suddenly, with a stroke or other damage to the visual cortex. Macdonald Critchley, in his book The Parietal Lobes, also refers to the opposite condition as a rare consequence of cerebral lesions in the early visual cortex: an enhancement of stereo vision “whereby near objects seem to be abnormally close, and distant objects seem to be much too far away.” Enhancement or loss of stereo vision can also occur transiently in a migraine aura or with certain drugs.

7. A number of people with misaligned eyes may not only lack stereo vision but have double vision or shimmering effects, which can cause them problems with daily activities generally, and especially with reading or driving.

8. Photographers and cinematographers, concerned to create an illusion of three-dimensionality on a flat plane, must deliberately renounce their binocularity and stereoscopy, confining themselves to a one-eye, one-lens view, to better frame and compose their pictures.

In a 2004 letter to the editor of the New England Journal of Medicine, Harvard neurobiologists Margaret Livingstone and Bevil Conway suggested, after an examination of Rembrandt’s self-portraits, that the painter was so walleyed as to be stereo-blind, and that “stereoblindness might not be a handicap—and might even be an asset—for some artists.” Subsequently they proposed, after looking at photographs of other artists, that many of them—de Kooning, Johns, Stella, Picasso, Calder, Chagall, Hopper, and Homer, among others—also seemed to have significant misalignment of the eyes and were perhaps also stereo-blind.

9. Walleyed people enjoy an unusually wide field of vision due to the divergence of their eyes and may hesitate to sacrifice this for an operation that might align their eyes cosmetically but fail to give them stereoscopy. Intriguingly, several such people have written to me that they are able to converge their eyes and achieve stereo vision briefly.

10. Together, the three of us had collaborated on several cases, including that of the “colorblind painter,” who suddenly lost all ability to see in color, and that of Virgil, a man blind nearly from birth whose sight had been restored after almost fifty years of blindness. (Both of these case histories, “The Case of the Colorblind Painter” and “To See and Not See,” were published in An Anthropologist on Mars.)

11. If a stereo photograph is flashed on a screen for as little as twenty milliseconds, a person with normal stereoscopy can perceive some stereo depth straightaway. But what one sees in a flash is not the full depth; the perception of this requires several seconds, even minutes, in which the picture seems to deepen as one continues to gaze at it—it is as if the stereo system takes a certain time to warm up, to come to its full capacity. Such a deepening seems peculiar to the stereo system (colors, by contrast, do not normally become more pronounced as one looks at them). The underlying cause for this is unknown, though it has been suggested that it entails the recruitment of additional binocular cells in the visual cortex.

(There is, additionally, a clear practice effect, so that people who exercise their stereo powers—for example, by working with a binocular microscope—may experience striking improvements in stereo acuity and stereo depth over a longer period. Here, too, the underlying mechanism is unknown.)

12. Bela Julesz, the remarkable researcher who studied random-dot stereoscopy, spoke of “cyclopean vision,” and regarded it as entailing neural mechanisms over and above those employed in ordinary stereo vision. This too is suggested by the fact that it may take a minute or more to “get” random-dot stereograms, where ordinary stereograms can be seen instantly.

13. Brewster also invented, around 1844, a simple handheld stereoscope using lenses (Wheatstone’s mirror stereoscope was large and heavy and had to sit on a table). While Brewster was at first full of admiration for Wheatstone, he subsequently became jealous of his younger colleague and began publishing vindictive articles about him, pseudonymously. Finally, in 1856, in his otherwise charming book The Stereoscope: Its History, Theory and Construction, he attacked Wheatstone openly and denied him any claim to priority in the realm of stereoscopy.

14. This view, which I share, seems to be in contradiction with the views of the great visual pioneer J. J. Gibson. In his 1950 book The Perception of the Visual World, he wrote, “If the gradient theory is correct, binocular vision simply takes its place as a determinant, but only one determinant, of visual space.” Several eminent contemporary vision researchers hold similar views. Thus Dale Purves and R. Beau Lotto, in their book Why We See What We Do, write of “a seamless relationship” between the three-dimensional world we construct with one eye and its “augmentation” by stereopsis. Such views, while wholly consistent with a behavioral or empirical theory of vision, give no weight to the qualitative and subjective aspects of stereoscopy. Here one needs inside narratives, personal accounts of what it is like to suddenly gain stereo vision after a lifetime of stereo blindness (as Sue describes) or to suddenly lose it after a lifetime of seeing in stereo (as I describe in the following chapter).

Persistence of Vision: A Journal

1. Many people with macular degeneration still manage to lead pretty full and independent lives. One patient of mine, a feisty old lady, told me that for five years after she lost central vision from macular degeneration, she “operated quite well on peripheral vision.” She could still take walks and find her way around, even though she was legally blind, with vision of 20/200 or less.

2. Although Critchley coined the term “paliopsia,” most people now use “palinopsia.”

3. Frigyes Karinthy, in Journey Round My Skull, describes a very different sort of filling in when he is losing his vision. It is not the sort of low-level filling in that I have, but a much more complex filling in at a higher level, one that draws on association and memory:

By now, I had learnt to interpret every hint afforded by the shifting of light and to complete the general effect from memory. I was getting used to this strange semi-darkness in which I lived, and I almost began to like it. I could still see the outline of figures pretty well, and my imagination supplied the details, like a painter filling an empty frame. I tried to form a picture of any face I saw in front of me by observing the person’s voice and movements. People were often astonished to see that I could not distinguish between colours and shades, yet I would catch momentary facial expressions unnoticed by those with normal eyesight. I, too, was surprised. The idea that I might already have gone blind struck me with sudden terror. . . . I might only be using people’s words and voices to reconstruct the lost world of reality, just as our mind, at the moment we fall asleep, forms images resembling those of real life from the phosphenes that dance before our closing eyes. I stood on the threshold of reality and imagination, and I began to doubt which was which. My bodily eye and my mind’s eye were blending into one, and I could no longer be certain which of the two was really in control.

4. There have, however, been two incidents that I am hard put to explain. I had smoked a little cannabis both times, and I found myself totally absorbed, gazing in a sort of rapture at flowers—some narcissus in a pot on one occasion and morning glories twining up a fence on the other. Both times, it seemed to me, the flowers filled out before my eyes, thrust themselves into the space around them, assuming their full and proper three-dimensional glory. They deflated once again when the cannabis wore off. Was this vision “real” or an illusion? It was wholly different in quality from the pseudostereo, the confounding illusions of depth and distance I would sometimes have with lines on the ground, where there was not, in reality, any depth at all. The flowers did have depth, and I was seeing them as I used to when I had two good eyes. If it was an aberrant perception or an illusion, it was a veridical one, consonant with reality.

Some of my correspondents have occasionally experienced an opposite effect with cannabis—a loss of stereo, so that their visual world seems two-dimensional, like a painting.

5. Gradually the peripheral vision in my right eye got worse, as a cataract developed in reaction to the radiation treatment. With this, what little stereopsis I had diminished. When I had the cataract removed in the spring of 2009, I had a sudden resurgence of peripheral vision and stereopsis. Everything looked, with my right eye, brigher and bluer, and when I went to the orchid show at the botanical garden the next day, I not only saw colors with a startling brilliance and freshness, but I could see flowers thrusting towards me in the bottom of my visual field. I rejoiced in this, but did not realize how short-lived my return to (at least partial) stereo would be.

6. There may be various optical or mechanical ways to enlarge the visual field if an eye is lost. The use of a prism, for example, may allow an extra six or eight degrees of visual field, and there may be ingenious strategies with mirrors, too. A more drastic solution was attempted by Federico, a fifteenth-century duke of Urbino who had lost one eye in a tournament. Fearing the ever-present threat of assassination and wanting to preserve his prowess on the battlefield, he had his surgeons amputate the bridge of his nose to allow a wider field for the remaining eye.

7. I wrote about this patient in “Eyes Right!” in The Man Who Mistook His Wife for a Hat. Another example was provided by my colleague M.-Marsel Mesulam, who wrote, “When the neglect is severe, the patient may behave almost as if one half of the universe had abruptly ceased to exist in any meaningful form. . . . Patients with unilateral neglect behave not only as if nothing were actually happening in the left hemispace, but also as if nothing of any importance could be expected to occur there.”

8. John Hull, who became totally blind in midlife, describes this sense of suddenness in Touching the Rock:

For the blind, people are not there unless they speak. Many times I have continued a conversation with a sighted friend only to discover that he is not there. He may have walked away without telling me. He may have nodded or smiled, thinking the conversation was over. From my point of view, he has suddenly vanished.

When you are blind, a hand suddenly grabs you. A voice suddenly addresses you. There is no anticipation or preparation. . . . I am passive in the presence of that which accosts me. . . . The normal person can choose whom he wants to speak to, as he wanders around the streets or the market-place. People are already there for him; they have a presence prior to his greeting them. . . . For the blind person, people are in motion, they are temporal, they come and they go. They come out of nothing; they disappear.

The Mind’s Eye

1. Despite an initially overwhelming sense of despair on losing their sight, some people, like Hull, have found their full creative strength and identity on the other side of blindness. One thinks especially of John Milton, who started to lose his sight around the age of thirty (probably from glaucoma), but produced his greatest poetry after becoming completely blind a dozen years later. He meditated on blindness, how an inward sight may come in place of outward sight, in Paradise Lost, in Samson Agonistes, and—most directly—in letters to friends and in a very personal sonnet, “On His Blindness.” Jorge Luis Borges, another poet who became blind, wrote about the varied and paradoxical effects of his own blindness; he also wondered how it might have been for Homer, who, Borges imagined, lost the world of sight but gained a much deeper sense of time and, with this, a matchless epic power. (This is beautifully discussed by J. T. Fraser in his 1989 foreword for the Braille edition of Time, the Familiar Stranger.)

2. In his book The Invention of Clouds, Richard Hamblyn recounts how Luke Howard, the nineteenth-century chemist who first classified clouds, corresponded with many other naturalists of the time, including John Gough, a mathematician blinded by smallpox at the age of two. Gough, Hamblyn writes, “was a noted botanist, having taught himself the entire Linnean system by touch. He was also a master of the fields of mathematics, zoology and scoteography—the art of writing in the dark.” (Hamblyn adds that Gough “might also have become an accomplished musician had his father, a stern Quaker . . . not stopped him playing on the godless violin that an itinerant fiddler had given him.”)

3. Tenberken also has an intense synesthesia, which has persisted and been intensified, it seems, by her blindness:

As far back as I can remember, numbers and words have instantly triggered colors in me. . . . The number 4, for example, [is] gold. Five is light green. Nine is vermilion. . . . Days of the week as well as months have their colors, too. I have them arranged in geometrical formations, in circular sectors, a little like a pie. When I need to recall on which day a particular event happened, the first thing that pops up on my inner screen is the day’s color, then its position in the pie.

4. Although I myself am a poor visualizer, if I shut my eyes, I can still “see” my hands moving on the piano keyboard when I play a piece that I know well. (This may happen even if I just play the piece in my mind.) I feel my hands moving at the same time, and I am not entirely sure that I can distinguish the “feeling” from the “seeing.” In this context, they seem inseparable, and one wants to use an intersensory term like “seeing-feeling.”

The psychologist Jerome Bruner speaks of such imagery as “enactive”—an integral feature of a performance (real or imaginary)—in contrast to an “iconic” visualization, the visualization of something outside oneself. The brain mechanisms underlying these two sorts of imagery are quite different.

5. Though I have almost no voluntary imagery, I am prone to involuntary imagery. I used to have this only as I was falling asleep, in migraine auras, with some drugs, or with fever. But now that my sight is impaired, I have it all the time.

In the 1960s, during a period of experimenting with large doses of amphetamines, I experienced a different sort of vivid mental imagery. Amphetamines can produce striking perceptual changes and dramatic enhancements of visual imagery and memory (as I described in “The Dog Beneath the Skin,” a chapter in The Man Who Mistook His Wife for a Hat). For a period of two weeks or so, I found that I had only to look at an anatomical picture or specimen, and its image would remain vivid and stable in my mind for hours. I could mentally project the image onto a piece of paper—it was as clear and distinct as if projected by a camera lucida—and trace its outlines with a pencil. My drawings were not elegant, but they were, everyone agreed, quite detailed and accurate. But when the amphetamine-induced state faded, I could no longer visualize, no longer project images, no longer draw—nor have I been able to do so in the decades since. This was not like voluntary imagery—I did not summon images to my mind or construct them bit by bit. It was involuntary and automatic, more akin to eidetic or “photographic” memory, or to palinopsia, an exaggerated persistence of vision.

6. The physicist John Tyndall referred to these in an 1870 lecture, a few years before Galton’s Inquiries: “In explaining scientific phenomena, we habitually form mental images of the ultra-sensible. . . . Without the exercise of this power our knowledge of nature would be a mere fabulation of co-existences and sequences.”

7. I described Temple more fully in An Anthropologist on Mars, and she speaks about her visual thinking especially in her book Thinking in Pictures.

8. Kosslyn’s latest book on the matter, The Case for Mental Imagery, details the history of this debate.

9. Functional MRIs also showed that the two hemispheres of the brain behaved differently in regard to imagery, the left hemisphere concerned with generic, categorical images—e.g., “trees”—and the right hemisphere with specific images—e.g., “the maple in my front yard”—a specialization also present in visual perception. Thus prosopagnosia, an inability to recognize specific faces, is associated with damaged or defective visual function in the right hemisphere, though people with prosopagnosia have no problem with the category of faces in general, a left-hemisphere function.

10. Mr. I.’s case is described in An Anthropologist on Mars.

11. While it seems clear that perception and imagery share certain neural mechanisms at higher levels, this sharing is less evident in the primary visual cortex—hence the possibility of a dissociation such as occurs in Anton’s syndrome. In Anton’s syndrome, patients with occipital damage are cortically blind, but believe they are still sighted. They will move about without restraint or caution, and if they bump into a piece of furniture, they will ascribe this, perhaps, to the furniture being “out of place.”

Anton’s syndrome is sometimes attributed to the preservation of some visual imagery despite occipital damage, and to patients mistaking this imagery for perception. But there may be other, stranger mechanisms at work. The denial of blindness—or, more accurately, the inability to realize that one has lost one’s vision—is very like another “disconnection syndrome,” known as anosognosia. With anosognosia, following damage to the right parietal lobe, patients lose awareness of their left side, and of the left half of space, along with the awareness that anything is amiss. If one draws their attention to their left arm, they will say it is someone else’s—“the doctor’s arm,” or “my brother’s arm,” or even “an arm someone left here.” Such confabulations seem similar in a way to those of Anton’s syndrome, attempts to explain what, to the patient, is a bizarrely inexplicable situation.

12. Einstein described this in regard to his own thinking:

The psychical entities which seem to serve as elements in thought are certain signs and more or less clear images which can be “voluntarily” reproduced and combined. . . . [Some] are, in my case, of visual and some of muscular type. Conventional words or other signs have to be sought for laboriously only in a second stage.

Darwin, on the other hand, seemed to describe a very abstract, almost computational process in his own thinking, when he wrote in his autobiography, “My mind seems to have become a kind of machine for grinding general laws out of large collections of facts.” (What Darwin omitted here was that he had a fantastic eye for form and detail, an enormous observational and depictive power, and it was these which provided the “facts.”)

13. Dominic ffytche, who has investigated the neurobiology of conscious vision—imagery and hallucination as well as perception—feels that visual consciousness is a threshold phenomenon. Using fMRIs to study patients with visual hallucinations, he has shown that there may be evidence of unusual activity in a specific part of the visual system—for example, the fusiform face area—but this has to reach a certain intensity before it enters consciousness, before the subject actually “sees” faces.

14. The heightened (and sometimes morbid) sensitivity of the visual cortex when deprived of its normal perceptual input may also predispose it to intrusive imagery. A significant proportion of those who go blind—10 to 20 percent, by most estimates—become prone to involuntary images, or outright hallucinations, of an intense and sometimes bizarre kind. Such hallucinations were originally described in the 1760s by the Swiss naturalist Charles Bonnet, and we now speak of hallucinations secondary to visual impairment as Charles Bonnet syndrome.

Hull described something akin to this which occurred for a while after he lost the last of his sight:

About a year after I was registered blind, I began to have such strong images of what people’s faces looked like that they were almost like hallucinations. . . . I would be sitting in a room with someone, my face pointed towards my companion, listening to him or her. Suddenly, such a vivid picture would flash before my mind that it was like looking at a television set. Ah, I would think, there he is, with his glasses and his little beard, his wavy hair and his blue, pinstriped suit, white collar and blue tie. . . . Now this image would fade and in its place another one would be projected. My companion was now fat and perspiring with receding hair. He had a red necktie and waistcoat, and a couple of his teeth were missing.

15. Ben, who had retinoblastoma, had both eyes removed at the age of three, but then, tragically, died at sixteen from a recurrence of his cancer. Videos of Ben and his echolocation can be seen at the website www .benunderwood.com.

16. See Ostrovsky et al., for example.

17. Congenitally blind people, we might suppose, can have no visual imagery at all, since they have never had any visual experience. And yet they sometimes report having clear and recognizable visual elements in their dreams. Helder Bértolo and his colleagues in Lisbon, in an intriguing 2003 report, described how they compared congenitally blind subjects with normal sighted subjects and found “equivalent visual activity” (based on analysis of EEG alpha-wave attenuation) in the two groups while dreaming. The blind subjects were able, upon waking, to draw the visual components of their dreams, although they had a lower rate of dream recall. Bértolo et al. conclude, therefore, that “the congenitally blind have visual content in their dreams.”

18.Would acquiring “sight” if one has never seen before be bewildering or enriching? For my patient Virgil, who was given sight, through surgery, after a lifetime of blindness, it was utterly incomprehensible at first, as I described in An Anthropologist on Mars. Thus although sensory-substitution technologies are exciting and promise a new freedom for blind people, we need to consider equally their impact on a life that has already been constructed without sight.

19. In a recent letter to his colleague Simon Hayhoe, John Hull expanded on this:

For example, when the thought of a car occurs to me, although my front-line images are of recently touching the warm bonnet of a car, or of the shape of the car as I feel for the door handle, there are also traces of the appearance of the whole car, from pictures of cars in books, or memories of cars coming and going. Sometimes, when I have to touch a modern car, I am surprised to find that this memory trace does not correspond to reality, and that cars are not the same shape they were twenty-five years ago.

There is a second point. The fact that an item of knowledge is so much buried in the sense or senses that first received it, means for me that I am not always sure whether my image is visual or not. The trouble is that tactile images of the shape and feel of things also often seem to acquire a visual content, or one cannot tell if the three-dimensional memory shape is being mentally represented by a visual or a tactile image. So even after all these years, the brain can’t sort out where it is getting stuff from.

INDEX

Abbott, Edwin, ref 1

Abramson, David H., ref 1, ref 2, ref 3, ref 4, ref 5

agnosia (for objects), ref 1, ref 2, ref 3, ref 4n, ref 5, ref 6, ref 7, ref 8, ref 9, ref 10, ref 11, ref 12, ref 13

defined, ref 1, ref 2

see also prosopagnosia, topographical agnosia

agraphia, ref 1, ref 2, ref 3, ref 4, ref 5 and n, ref 6, ref 7, ref 8n, ref 9n, ref 8, ref 9, ref 10, ref 11, ref 12

isolated, ref 1n

alexia, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6n, ref 7n, ref 8n, ref 8

bilingualism and, ref 1n

defined, ref 1, ref 2, ref 3

history of, ref 1

musical, ref 1, ref 2, ref 3, ref 4

transient, ref 1n, ref 2

see also reading

alphabetic languages vs. iconic, ref 1, ref 2n, ref 3 and n

Alzheimer’s disease, ref 1, ref 2, ref 3, ref 4n, ref 5

amphetamines, imagery and, ref 1n

amygdala, ref 1n, ref 2

Anne F., ref 1

anomia, ref 1, ref 2

anosognosia, ref 1n

Anton’s syndrome, ref 1n

aphasia, ref 1, ref 2n, ref 3n, ref 4n, ref 5n, ref 6, ref 7, ref 8n

detection of lies and, ref 1

dreams and, ref 1

epilepsy and, ref 1n

forms of, ref 1

gesture, mime and, ref 1

lexicon for, ref 1

music and, ref 1, ref 2 and n

power of thought and, ref 1, ref 2n

recovery from, ref 1, ref 2n

social isolation and, ref 1 and nref 2, ref 3

transient, ref 1, ref 2n

Asperger’s syndrome, ref 1, ref 2n,

see also Grandin, Temple

audiobooks, ref 1, ref 2

Bach-y-Rita, Paul, ref 1

Barry, Sue, ref 1

Benson, Frank, ref 1, ref 2n

Bértolo, Helder, ref 1n

Beth Abraham Hospital, ref 1

Bigley, G. Kim, ref 1n

Bisiach, Eduardo, ref 1

blind spot, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7, ref 8, ref 9

blindness

dreams and, ref 1

experience of, ref 1n, ref 2n, ref 3n, ref 4, ref 5, ref 6n, ref 7n, ref 8n, ref 9n

sensory heightening or substitution and, ref 1n, ref 2, ref 3 and n, ref 4, ref 5, ref 6 and n, ref 7n, ref 8n

see also agnosia,

colorblindness, stereo blindness

blindsight, ref 1n

Bodamer, Joachim, ref 1

Book of Kells, ref 1

Borges, Jorge Luis, ref 1n, ref 2n

Brady, Frank, ref 1

Braille, ref 1, ref 2, ref 3, ref 4, ref 5

brain imaging, ref 1, ref 2, ref 3, ref 4 and n, ref ref 5, ref 6, ref 7, ref 8 and n, ref 9n, ref 8, ref 9, ref 10

Brewster, David, ref 1, ref 2n

Broca, Paul, ref 1, ref 2, ref 3n

Bruner, Jerome, ref 1n

cancer, ref 1 and ff

cannabis, ref 1n

Capgras syndrome, ref 1

cartoons, ref 1

Changizi, Mark, ref 1

Charcot, Jean-Martin, ref 1n, ref 2, ref 3

Charles Bonnet syndrome, ref 1n

Chinese ideograms, ref 1 and n, ref 2 and n

cinematography, ref 1n, ref 2, ref 3n

Cisne, John, ref 1

Close, Chuck, ref 1n

color

anomia, ref 1

as identifier, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6

difficulty recognizing, ref 1, ref 2, ref 3

distortion, ref 1, ref 2

filling in and, ref 1, ref 2, ref 3

migraine and, ref 1

recognition or perception of, ref 1, ref 2n, ref 3n, ref 4n

visualization or imagination of, ref 1, ref 2n, ref 3, ref 4

colorblind painter, ref 1, ref 2n, ref 3

colorblindness, ref 1n, ref 2, ref 3, ref 4

Conway, Bevil, ref 1n

Critchley, Macdonald, ref 1n, ref 2, ref 3n, ref 4 and n

crossword puzzle, ref 1n

cuttlefish, ref 1, ref 2

Damasio, Antonio, ref 1, ref 2n

Damasio, Hanna, ref 1

Darwin, Charles, ref 1, ref 2, ref 3, ref 4, ref 5n

deafness

cortical reallocation and, ref 1

multimodal sensation and, ref 1

Dehaene, Stanislas, ref 1, ref 2, ref 3n, ref 4, ref 5n

Déjerine, Joseph-Jules, ref 1, ref 2

depth perception

individual variation in, ref 1, ref 2

monocular cues for, ref 1, ref 2, ref 3

training effect, ref 1n, ref 2

see also stereo vision

developmental optometry, ref 1, ref 2

Devinsky, Orrin, ref 1, ref 2

Donald, Merlin, ref 1

Dr. P. (man who mistook his wife for a hat), ref 1, ref 2n, ref 3, ref 4

dreams, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6n

Duchaine, Brad, ref 1

dyslexia, ref 1n, ref 2

Einstein, Albert, ref 1n

Ellinwood, Everett, ref 1

Engel, Howard, ref 1, ref 2, ref 3

epilepsy, and alexia, ref 1n

Etcoff, Nancy, ref 1

face blindness

acquired vs. congenital, ref 1

adaptations to, ref 1, ref 2n, ref 3n

due to tumor, ref 1

genetic basis, ref 1 and n, ref 2, ref 3

public understanding of, ref 1

social consequences of, ref 1, ref 2n, ref 3n, ref 4, ref 5 and n, ref 6

face recognition, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7

early exposure and ethnic bias, ref 1 and n

expertise and, ref 1, ref 2

in infants, ref 1, ref 2 and n, ref 3 and n

neural correlates of, ref 1, ref 2n, ref 3n, ref 4n, ref 5n

in photographs and mirrors, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6n, ref 7 and n, ref 8, ref 9

range of ability, ref 1

facial expression, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6 and n

familiarity, sense of, ref 1

Faraday, Michael, ref 1n, ref 2

Farah, Martha, ref 1, ref 2

ffytche, Dominic, ref 1, ref 2, ref 3n

filling in

of blind spot, ref 1, ref 2, ref 3n

of color, ref 1, ref 2

of motion, ref 1

of pattern, ref 1, ref 2

Fleishman, John A., ref 1n

Flourens, Jean-Pierre, ref 1

Fox, Stephen, ref 1

Fraser, J. T., ref 1n

Freiwald, Winrich, ref 1 and n

Freud, Sigmund, ref 1, ref 2n

Fried, Itzhak, ref 1 and n

fusiform face area, ref 1, ref 2n

Gall, Franz Joseph, ref 1

Galton, Francis, ref 1, ref 2

Garrido, Lucia, ref 1

Gauthier, Isabel, ref 1

Gerstmann’s syndrome, ref 1

gesture and mime, ref 1, ref 2

Gibson, J. J., ref 1n

Goldberg, Elkhonon, ref 1

Goodall, Jane, ref 1, ref 2

Gordon, Arlene, ref 1, ref 2, ref 3

Gough, John, ref 1n

Gould, Stephen Jay, ref 1 and n

gradiental principle of cortical organization, ref 1

Grandin, Temple, ref 1n, ref 2, ref 3n

Gregory, Richard L., ref 1n

Gross, Charles, ref 1 and n

Hale, John and Sheila, ref 1n

hallucination, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7n, ref 8n

of faces, ref 1, ref 2, ref 3, ref 4, ref 5n

lexical, ref 1, ref 2, ref 3 see also filling in

Hamblyn, Richard, ref 1n

handwriting, recognition of, ref 1, see also writing

Head, Henry, ref 1n, ref 2

Helmholtz, Hermann von, ref 1n

hemianopia, ref 1, ref 2

hemi-inattention, ref 1, ref 2, ref 3, ref 4n

Holmes, Gordon, ref 1

Holmes, Oliver Wendell, ref 1

hospitals, chronic, ref 1

Howard, Luke, ref 1n

Hubel, David, ref 1, ref 2, ref 3, ref 4

Hull, John, ref 1n, ref 2, ref 3, ref 4, ref 5 passim, ref 6n, ref 7n

hyperlexia, ref 1n

imagery

enactive, ref 1, ref 2, ref 3n, ref 4, ref 5, ref 6n

of faces, ref 1, ref 2

see also visual imagery

inferotemporal cortex, see fusiform face area, visual word form area

Jackson, John Hughlings, ref 1, ref 2 and n

Japanese characters (kanji vs. kana), ref 1n, ref 2n

Joan C., ref 1, ref 2

Johnson, Dr. Samuel, ref 1n

Julesz, Bela, ref 1n

Kallir, Lilian, ref 1, ref 2n, ref 3

Kapur, Narinder, ref 1

Karinthy, Frigyes, ref 1n

Kekulé, August, ref 1

Klessinger, Nicolai, ref 1

Koch, Christof, ref 1 and n

Kosslyn, Steven M., ref 1, ref 2, ref 3n, ref 4

Landolt, Edmund, ref 1

Lester C., ref 1n

letterforms, evolution of, ref 1 and n

Lissauer, Heinrich, ref 1

Livingstone, Margaret, ref 1 and n, ref 2n

localization of cortical function, history of, ref 1, ref 2n, ref 3n

Lombroso, Cesare, ref 1n

Lordat, Jacques, ref 1

Luria, A. R., ref 1

Lusseyran, Jacques, ref 1, ref 2, ref 3

Luzzatti, Claudio, ref 1

Lynch, Alexandra, ref 1

macular degeneration, ref 1n

Magee, Brian, ref 1

Maxwell, James Clerk, ref 1n

McDonald, Ian, ref 1, ref 2n

McGinn, Colin, ref 1

Mehta, Ved, ref 1

melanoma, ocular, ref 1 and ff

memory, as substitute for sensory perception, see visual imagery

Merabet, Lotfi, ref 1

Mesulam, M.-Marsel, ref 1n

migraine

alexia and, ref 1n

aphasia and, ref 1

color and, ref 1

distinguished from tumor, ref 1, ref 2

involuntary imagery and, ref 1, ref 2

stereo blindness and, ref 1n

Milligan, Martin, ref 1, ref 2

Milton, John, ref 1n

modularity, cortical, ref 1

Morgan, W. Pringle, ref 1n

Morin, Bernard, ref 1

Morris, Errol, ref 1

Moss, Scott, ref 1

motion

filling in of, ref 1

perception or sensation of, ref 1n, ref 2

motion parallax ref 1, ref 2, ref 3, ref 4

motor imagery or memory, ref 1, ref 2n, ref 3, ref 4n, ref 5, ref 6, ref 7, ref 8, ref 9n

music

alexia for, ref 1, ref 2, ref 3, ref 4

aphasia and, ref 1, ref 2

blindness and, ref 1

memory and imagery for, ref 1, ref 2

notation, ref 1, ref 2n, ref 3n, ref 4, ref 5

performance of, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7, ref 8n

therapy, ref 1, ref 2

Nakayama, Ken, ref 1n, ref 2, ref 3n

names, visualization or recall of, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7, ref 8

neglect, visual, ref 1, ref 2, ref 3, ref 4n

neuroplasticity, ref 1, ref 2, ref 3, ref 4, ref 5n, ref 6, ref 7, ref 8, see also sensory substitution

Neville, Helen, ref 1

Nordby, Knut, ref 1

numbers, perception or recognition of, ref 1, ref 2 and n, ref 3, ref 4, ref 5, ref 6, ref 7, ref 8n

object recognition, ref 1, ref 2, see also agnosia

Ostrovsky, Yuri, ref 1n

palinopsia, ref 1 and n, ref 2n

Pallis, Christopher, ref 1

Pammer, Kristen, ref 1n

Pascalis, Olivier, ref 1

Pascual-Leone, Alvaro, ref 1, ref 2

Patricia H., ref 1

pattern, filling in or hallucination of, ref 1, ref 2, ref 3

peripheral vision, ref 1n, ref 2, ref 3, ref 4, ref 5

Petersen, Steven, ref 1

photographs and pictures, recognition of, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7, ref 8 and n, ref 9, ref 10, ref 11, ref 12, ref 13

photography, history of, ref 1 and n

phrenology, ref 1n

Pick’s disease, ref 1n

place recognition, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7, ref 8, ref 9, ref 10, ref 11, ref 12, ref 13, ref 14, ref 15, ref 16, ref 17

Poe, Edgar Allan, ref 1

Post, Wiley, ref 1

posterior cortical atrophy, ref 1, ref 2, ref 3n

Prescott, William, ref 1

Purves, Dale, ref 1n

Pylyshyn, Zenon, ref 1

Quian Quiroga, Rodrigo, ref 1n

Raichle, Marcus, ref 1

reading

evolution of, ref 1

meaning and, ref 1n

see also alexia

recognition

preconscious, ref 1

visual, see agnosia, prosopagnosia, topographical agnosia

Rembrandt van Rijn, ref 1

Rocke, Alan J., ref 1

Romano, Paul, ref 1

Rosenfield, Israel, ref 1n, ref 2n, ref 3n

Ruggiero, Theresa, ref 1, ref 2

Russell, Bertrand, ref 1

Russell, R., ref 1

schizophrenia, recognition of facial expression and, ref 1n

scotoma, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7, ref 8, ref 9

Scribner, Charles, Jr., ref 1, ref 2n

Sellers, Heather, ref 1

sensory substitution, ref 1, ref 2n, ref 3, ref 4 and n, ref 5, ref 6n, ref 7n, ref 8n

Sharp, Frank R., ref 1n

Shepard, Roger and Jacqueline Metzler, ref 1

Shimojo, Shinsuke, ref 1, ref 2

Shin, Yong-Wook, ref 1n

Shulman, Dennis, ref 1, ref 2, ref 3

Siegel, Ralph, ref 1

Sinha, Pawan, ref 1

Spurzheim, Johann, ref 1n

stereo blindness, ref 1n, ref 2, ref 3n, ref 4, ref 5, ref 6, ref 7n, ref 8n

artists and, ref 1 and n

incidence of, ref 1

transient, ref 1n

see also Barry, Sue; stereo vision, loss of

stereo illusions, ref 1n, ref 2, ref 3, ref 4n

stereo viewers and technologies, ref 1, ref 2, ref 3n

stereo vision, ref 1

in animals, ref 1

critical period for, ref 1, ref 2, ref 3

in dreams and imagination, ref 1, ref 2

intoxication and, ref 1n

loss of, ref 1, ref 2, ref 3, ref 4n

neural mechanisms of, ref 1

two-dimensional composition and, ref 1 and n, ref 2

vision therapy to achieve, ref 1, ref 2, ref 3

stereograms, ref 1, ref 2, ref 3n

Stereoscopic Society, New York, ref 1, ref 2

symbols, recognition of, ref 1, ref 2

synesthesia, ref 1n, ref 2

Tenberken, Sabriye, ref 1, ref 2n, ref 3

thought and imagery, ref 1, ref 2n, ref 3n, ref 4n

tongue, sensory substitution and, ref 1, ref 2n, ref 3, ref 4

topographical agnosia, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7, ref 8, ref 9, ref 10, ref 11, ref 12, ref 13 ref 14, ref 15, ref 16, ref 17

Torey, Zoltan, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6

Tsao, Doris, ref 1 and n

Turnbull, Colin, ref 1n

Tyndall, John, ref 1n

Underwood, Ben, ref 1n

Urbino, Duke Federico of, ref 1n

vegetative states, ref 1

Vermeij, Geerat, ref 1

Virgil (patient), ref 1n

vision therapy, ref 1, ref 2, ref 3

visual imagery, ref 1, ref 2n

alexia and, ref 1

aphasia and, ref 1

blindness and, ref 1, ref 2, ref 3n, ref 4, ref 5n, ref 6n, ref 7n

creative thought and, ref 1, ref 2n, ref 3n, ref 4n

descriptive vs. depictive, ref 1, ref 2

fMRI studies of, ref 1n, ref 2n

involuntary, ref 1, ref 2, ref 3, ref 4, ref 5n

loss or lack of, ref 1, ref 2, ref 3n, ref 4, ref 5, ref 6

voluntary, ref 1, ref 2n, ref 3

visual word form area, ref 1, ref 2, ref 3n, ref 4, ref 5n, ref 6

Vrba, Elisabeth, ref 1

Vygotsky, Lev, ref 1

Wallace, Alfred Russel, ref 1, ref 2n

Wasserman, Bob, ref 1, ref 2, ref 3, ref 4

Wells, H. G., ref 1

Wernicke, Carl, ref 1, ref 2

West, Thomas G., ref 1n

Wheatstone, Charles, ref 1, ref 2n, ref 3n

Wiesel, Torsten, ref 1, ref 2, ref 3

Wigan, A. L., ref 1n

Wilkens, Jeannette, ref 1 and n, ref 2, ref 3

Winchester, Simon, ref 1

Wittgenstein, Ludwig, ref 1

Wolf, Maryanne, ref 1n

writing

aphasia and, ref 1

difficulties with, see agraphia

evolution of, ref 1, ref 2n

hallucination of, ref 1, ref 2

handwriting, recognition of, ref 1

in the dark, ref 1n

learning of, ref 1n

preserved with alexia, ref 1, ref 2n

systems of, ref 1, ref 2n, ref 3 and n

Wundt, Wilhelm, ref 1

Young, Thomas, ref 1n

The Mind’s Eye

Oliver Sacks is a practising physician and the author of eleven books, including The Man Who Mistook His Wife for a Hat and Awakenings (which inspired the Oscar-nominated film). He lives in New York City, where he is professor of neurology and psychiatry at Columbia University Medical Center and Columbia’s first Columbia University Artist. For more about his work, visit www.oliversacks.com.

ALSO BY OLIVER SACKS

Migraine

Awakenings

A Leg to Stand On

The Man Who Mistook His Wife for a Hat

Seeing Voices

An Anthropologist on Mars

The Island of the Colour-blind

Uncle Tungsten

Oaxaca Journal

Musicophilia

PERMISSIONS ACKNOWLEDGMENTS

Grateful acknowledgment is made to the following for permission to reprint previously published material:

Basic Books: Excerpts from The Invention of Memory by Israel Rosenfield, copyright © 1998 by Israel Rosenfield. Reprinted by permission of Basic Books, a member of the Perseus Books Group, administered by Copyright Clearance Center.

Pantheon Books: Excerpts from Touching the Rock by John Hull, copyright © 1990 by John M. Hull. Reprinted by permission of Pantheon Books, a division of Random House, Inc.

First published as a Borzoi Book 2010 by Alfred A. Knopf,

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