An Anthropologist on Mars (1995)

by Oliver Sacks

  A certain mild pleasure came from looking at drawings; he had been a fine draftsman in his earlier years. Could he not go back to drawing again? This thought was slow to occur to him, and it only took hold after being suggested repeatedly by others. His own first impulse was to paint in color. He insisted that he still “knew” what colors to use, even though he could no longer see them. He decided, as a first exercise, to paint flowers, taking from his palette what tints seemed “tonally right.” But the pictures were unintelligible, a confusing welter of colors to normal eyes. It was only when one of his artist friends took black-and-white Polaroids of the paintings that they made sense. The contours were accurate, but the colors were all wrong. “No one will get your paintings”, one of his friends said, “unless they are as colorblind as you.”

  “Stop pushing it”, said another. “You can’t use color now.” Mr. I. reluctantly allowed all his colored paints to be put away. It’s only temporary, he thought. I’ll be back to color soon.

  These first weeks were a time of agitation, even desperation; he was constantly hoping that he would wake up one fine morning and find the world of color miraculously restored. This was a constant motif in his dreams at the time, but the wish was never fulfilled, even in his dreams. He would dream that he was about to see in color, but then he would wake and find that nothing had changed. He constantly feared that whatever had happened would happen again, this time depriving him of all his sight completely. He thought he had probably had a stroke, caused by (or perhaps causing) his accident in the car, and feared that there could be another stroke at any moment. In addition to this medical fear, there was a deeper bewilderment and fear that he found almost impossible to articulate, and it was this that had come to a head in his month of attempted color painting, his month of insisting that he still “knew” color. It had gradually come upon him, during this time, that it was not merely color perception and color imagery that he lacked, but something deeper and difficult to define. He knew all about color, externally, intellectually, but he had lost the remembrance, the inner knowledge, of it that had been part of his very being. He had had a lifetime of experience in color, but now this was only a historical fact, not something he could access and feel directly. It was as if his past, his chromatic past, had been taken away, as if the brain’s knowledge of color had been totally excised, leaving no trace, no inner evidence, of its existence behind. 7

  7. The question of “knowing” color is very complex and has paradoxical aspects that are difficult to dissect. Certainly Mr. I. was intensely aware of a profound loss with the change in his vision, so clearly some sort of comparison with past experience was possible for him. Such a comparison is not possible if there is a complete destruction of the primary visual cortex on both sides, say from a stroke, as in Anton’s syndrome. Patients with this syndrome become totally blind, but make no complaint or report of their blindness. They do not know they are blind; the whole structure of consciousness is completely reorganized—instantly so—at the moment they are stricken.

  Similarly, patients with massive strokes in the right parietal cortex may lose not only the sensation and use but the very knowledge of their left sides, of everything to the left, and indeed of the very concept of leftness. But they are “anosognosic”—they have no knowledge of their loss; we may say their world is bisected, but, for them, it is whole and complete.

  By the beginning of February, some of his agitation was calming down; he had started to accept, not merely intellectually, but at a deeper level, too, that he was indeed totally colorblind and might possibly remain so. His initial sense of helplessness started to give way to a sense of resolution—he would paint in black and white, if he could not paint in color; he would try to live in a black-and-white world as fully as he could. This resolution was strengthened by a singular experience, about five weeks after his accident, as he was driving to the studio one morning. He saw the sunrise over the highway, the blazing reds all turned into black: “The sun rose like a bomb, like some enormous nuclear explosion”, he said later. “Had anyone ever seen a sunrise in this way before?”

  Inspired by the sunrise, he started painting again—he started, indeed, with a black-and-white painting that he called Nuclear Sunrise, and then went on to the abstracts he favored, but now painting in black and white only. The fear of blindness continued to haunt him but, creatively transmuted, shaped the first “real” paintings he did after his color experiments. Black-and-white paintings he now found he could do, and do very well. He found his only solace working in the studio, and he worked fifteen, even eighteen, hours a day. This meant for him a kind of artistic survival: “I felt if I couldn’t go on painting”, he said later, “I wouldn’t want to go on at all.”

  His first black-and-white paintings, done in February and Marh, gave a feeling of violent forces—rage, fear, despair, excitement—but these were held in control, attesting to the powers of artistry that could disclose, and yet contain, such intensity of feeling. In these two months he produced dozens of paintings, marked by a singular style, a character he had never shown before. In many of these paintings, there was an extraordinary shattered, kaleidoscopic surface, with abstract shapes suggestive of faces—averted, shadowed, sorrowing, raging—and dismembered body parts, faceted and held in frames and boxes. They had, compared with his previous work, a labyrinthine complexity, and an obsessed, haunted quality—they seemed to exhibit, in symbolic form, the predicament he was in.

  Starting in May—it was fascinating to watch—he moved from these powerful but rather terrifying and alien paintings toward themes, living themes, he had not touched in thirty years, back to representational paintings of dancers and racehorses. These paintings, even though still in black and white, were full of movement, vitality, and sensuousness; and they went with a change in his personal life—a lessening of his withdrawal and the beginnings of a renewed social and sexual life, a lessening of his fears and depression, and a turning back to life.

  At this time, too, he turned to sculpture, which he had never done before. He seemed to be turning to all the visual modes that still remained to him—form, contour, movement, depth—and exploring them with heightened intensity. He also started painting portraits, although he found that he could not work from life, but only from black-and-white photographs, fortified by his knowledge of and feeling for each subject. Life was tolerable only in the studio, for here he could reconceive the world in powerful, stark forms. But outside, in real life, he found the world alien, empty, dead, and grey.

  This was the story Bob Wasserman and I got from Mr. I.—a story of an abrupt and total breakdown of color vision, and his attempts to live in a black-and-white world. I had never been given such a history before, I had never met anyone with total colorblindness before, and I had no idea what had happened to him—nor whether his condition could be reversed or improved.

  The first thing was to define his impairments more precisely with various tests, some quite informal, making use of everyday objects or pictures, whatever came to hand. For instance, we first asked Mr. I. about a shelf of notebooks—blue, red, and black—by my desk. He instantly picked out the blue ones (a bright medium blue to normal eyes)—“they’re pale.” The red and the black were indistinguishable—both, for him, were “dead black.”

  We then gave him a large mass of yarns, containing thirty-three separate colors, and asked him to sort these: he said he could not sort them by color, but only by grey-scale tonal values. He then, rapidly and easily, separated the yarns into four strange, chromatically random piles, which he characterized as 0-2,5%, 25-50%, 50-75%, and 75-100% on a grey-tone scale (though nothing looked to him purely white, and even white yarn looked slightly “dingy” or “dirty”).

  We ourselves could not confirm the accuracy of this, because our color vision interfered with our ability to visualize a grey scale, just as normally sighted viewers had been unable to perceive the tonal sense of his confusingly polychromatic flower paintings. But a black-and-
white photograph and a black-and-white video camera confirmed that Mr. I. had indeed accurately divided the colored yarns in a grey scale that basically coincided with their own mechanical reading. There was, perhaps, a certain crudeness in his categories, but this went with the sense of sharp contrast, the paucity of tonal gradations, that he had complained of. Indeed, when shown an artist’s grey scale of perhaps a dozen gradations from black to white, Mr. I. could distinguish only three or four categories of tone. 8

  8. One anomaly showed itself in the yarn-sorting test; he ranked bright saturated blues as “pale” (as he had complained that the blue sky seemed almost white). But was this an anomaly? Could we be sure that the blue wool was not, under its blueness, rather washed-out or pale? We had to have hues that were otherwise identical—identical in brightness, saturation, reflectivity, so we obtained a set of carefully produced color buttons known as the Farnsworth-Munsell test and gave this to Mr. I. He was unable to put the buttons in any order, but he did separate out the blue ones as “paler” than the rest.

  We also showed him the classic Ishihara color-dot plates, in which configurations of numerals in subtly differentiated colors may stand out clearly for the normally sighted, but not for those with various types of colorblindness. Mr. I. was unable to see any of these figures (although he was able to see certain plates that are visible to the colorblind but not to normally sighted people, and thus designed to catch pretended or hysterical colorblindness). 9

  9. Further testing with the Nagel anomaloscope and the Sloan achromatopsia cards confirmed Mr. I.’s total colorblindness. With Dr. Ralph Siegel, we did tests of depth and motion perception (using Julesz random-dot stereograms and moving random-dot fields)—these were normal, as were tests of his ability to generate structure and depth from motion. There was, however, one interesting anomaly: Mr. I. was unable to “get” red and green stereograms (bicolor anaglyphs), presumably because color vision is needed to segregate the two images. We also obtained electroretinograms, and these were quite normal, indicating that all three cone mechanisms in the retina were intact, and that the colorblindness was indeed of cerebral origin.

  We happened to have a postcard that could have been designed for testing achromatopes—a postcard of a coastal scene, with fishermen on a jetty silhouetted against a dark red sunset sky. Mr. I. was totally unable to see the fishermen or the jetty, and saw only the half-engulfed hemisphere of the setting sun.

  Though such problems arose when he was shown colored pictures, Mr. I. had no difficulty describing black-and-white photographs or reproductions accurately; he had no difficulty recognizing forms. His imagery and memory of objects and pictures shown to him were indeed exceptionally vivid and accurate, though always colorless. Thus, after being given a classic test picture of a colored boat, he looked intensely, looked away, and then rapidly reproduced it in black and white paint. When asked the colors of familiar objects, he had no difficulties in color association or color naming. (Patients with color anomia, for instance, can match colors perfectly but have lost the names of colors, and might speak, uncertainly, of a banana being “blue.” A patient with a color agnosia, by contrast, could also match colors, but would evince no surprise if given a blue banana. Mr. I., however, had neither of these problems.) 10

  10. In 1877, Gladstone, in an article entitled “On the Colour Sense of Homer”, spoke of Homer’s use of such phrases as “the wine-dark sea.” Was this just a poetic convention, or did Homer, the Greeks, actually see the sea differently? There is indeed considerable variation between different cultures in the way they will categorize and name colors—individuals may only “see” a color (or make a perceptual categorization) if there is an existing cultural category or name for it. But it is not clear whether such categorization may actually alter elementary color perception.

  Nor did he (now) have any difficulties reading. Testing up to this point, and a general neurological examination, thus confirmed Mr. I.’s total achromatopsia.

  We could say to him at this point that his problem was real—that he had a true achromatopsia and not a hysteria. He took this, we thought, with mixed feelings: he had half hoped it might be merely a hysteria, and as such potentially reversible. But the notion of something psychological had also distressed him and made him feel that his problem was “not real” (indeed, several doctors had hinted at this). Our testing, in a sense, legitimized his condition, but deepened his fear about brain damage and the prognosis for recovery.

  Although it seemed that he had an achromatopsia of cerebral origin, we could not help wondering whether a lifetime of heavy smoking could have played a part; nicotine can cause a dimming of vision (an amblyopia) and sometimes an achromatopsia—but this is predominantly due to its effects on the cells of the retina. But the major problem was clearly cerebral: Mr. I. could have sustained tiny areas of brain damage as a result of his concussion; he could have had a small stroke either following, or conceivably precipitating, the accident.

  The history of our knowledge about the brain’s ability to represent color has followed a complex and zigzag course. Newton, in his famous prism experiment in 1666, showed that white light was composite—could be decomposed into, and recomposed by, all the colors of the spectrum. The rays that were bent most (“the most refrangible”) were seen as violet, the least refrangible as red, with the rest of the spectrum in between. The colors of objects, Newton thought, were determined by the “copiousness” with which they reflected particular rays to the eye. Thomas Young, in 1802, feeling that there was no need to have an infinity of different receptors in the eye, each tuned to a different wavelength (artists, after all, could create almost any color they wanted by using a very limited palette of paints) postulated that three types of receptors would be enough. 11

  11. “As it is almost impossible to conceive each sensitive point of the retina to contain an infinite number of particles, each capable of vibrating in perfect unison with every possible undulation”, Young wrote, “it becomes necessary to suppose the number limited, for instance to the three principal colours, red, yellow, and blue. ”

  The great chemist John Dalton, just five years earlier, had provided a classic description of red-green colorblindness in himself. He thought this was due to a discoloration in the transparent media of the eye—and, indeed, willed an eye to posterity to test this. Young, however, provided the correct interpretation—that one of the three types of color receptor was missing. Dalton’s eye still resides, pickled, on a shelf in Cambridge.

  Lindsay T. Sharpe and Knut Nordby discuss this and many other aspects of the history of colorblindness research in “Total Colorblindness: An Introduction.”

  Young’s brilliant idea, thrown off casually in the course of a lecture, was forgotten, or lay dormant, for fifty years, until Hermann von Helmholtz, in the course of his own investigation of vision, resurrected it and gave it a new precision, so that we now speak of the Young-Helmholtz hypothesis. For Helmholtz, as for Young, color was a direct expression of the wavelengths of light absorbed by each receptor, the nervous system just translating one into the other: “Red light stimulates the red-sensitive fibres strongly, and the other two weakly, giving the sensation red.” 12

  12. In 1816, the young Schopenhauer proposed a different theory of color vision, one that envisaged not a passive, mechanical resonance of tuned particles or receptors, as Young had postulated, but their active stimulation, competition, and inhibition—an explicit “opponens” theory such as Ewald Hering was to create seventy years later, in apparent contradiction of the Young-Helmholtz theory. These opponens theories were ignored at the time, and continued to be ignored until the 1950s. We now envisage a combination of Young-Helmholtz and opponens mechanisms: tuned receptors, which converse with one another, are continually linked in an interactional balance. Thus integration and selection, as Schopenhauer divined, start in the retina.

  In 1884, Hermann Wilbrand, seeing in his neurological practice patients with a range of visual losses—in some
predominantly the loss of visual field, in others predominantly of color perception, and in still others predominantly of form perception—suggested that there must be separate visual centers in the primary visual cortex for “light impressions”, “color impressions”, and “form impressions”, though he had no anatomical evidence for this. That achromatopsia (and even hemi-achromatopsia) could indeed arise from damage to specific parts of the brain was first confirmed, four years later, by a Swiss ophthalmologist, Louis Verrey. He described a sixty-year-old woman who, in consequence of a stroke affecting the occipital lobe of her left hemisphere, now saw everything in the right half of her visual field in shades of grey (the left half remained normally colored). The opportunity to examine his patient’s brain after her death showed damage confined to a small portion (the fusiform and lingual gyri) of the visual cortex—it was here, Verrey concluded, that “the centre for chromatic sense will be found.” That such a center might exist, that any part of the cortex might be specialized for the perception or representation of color, was immediately contested and continued to be contested for almost a century. The grounds of this contention go very deep, as deep as the philosophy of neurology itself.

  Locke, in the seventeenth century, had held to a “sensationalist” philosophy (which paralleled Newton’s physicalist one): our senses are measuring instruments, recording the external world for us in terms of sensation. Hearing, seeing, all sensation, he took to be wholly passive and receptive. Neurologists in the late nineteenth century were quick to accept this philosophy and to embed it in a speculative anatomy of the brain. Visual perception was equated with “sense-data” or “impressions” transmitted from the retina to the primary visual area of the brain, in an exact, point-to-point correspondence—and there experienced, subjectively, as an image of the visual world. Color, it was presumed, was an integral part of this image. There was no room, anatomically, it was thought, for a separate color center—or indeed, conceptually, for the very idea of one. Thus when Verrey published his findings in 1888, they flew in the face of accepted doctrine. His observations were doubted, his testing criticized, his examination regarded as flawed—but the real objection, behind these, was doctrinal in nature.