A Natural History of the Senses (39 page)

Animals indulge in such lavish and luscious forms of display that it would take a whole book just to list their color-mad graces. The peacock’s scintillating, many-eyed tail is so famous an example it’s become eponymous. “What a peacock he is!” we say of a gentleman dandied up beyond belief. Color as a silent language works so well that nearly every animal speaks it. Octopuses change color as they change mood. A scared freshwater perch automatically turns pale. A king penguin chick knows to peck at the apricot comet on its parent’s bill if it wants to be fed. A baboon flashes its blue rump in sexual or submissive situations. Confront a male robin with a handful of red feathers and it will attack it. A deer pops its white tail as a warning to its kin and then springs out of the yard. We lift our eyebrows to signal our disbelief. But many animals wear their gaudy colors as warnings, as well. The arrowpoison frog, which dwells in the Amazon rain forest, glistens with vibrant aqua blue and scarlet.
Don’t mess with me!
its color shrieks at would-be predators. I was with a group of people who came upon such a frog squatting on a log, and the temptation to touch its cloisonné-like back was so strong one man automatically began to reach out for it when his neighbor grabbed his wrist, just in time. That frog didn’t need to flee; it was coated with a slime so poisonous that if the man had touched it, and then touched his eye or mouth, he would have been poisoned on the spot.

When your cat stalks a low-lying slither at twilight, it’s tempting to believe the old wives’ tale that cats can see in the dark. After all, don’t their eyes glow? But no animal can see without light. Cats, and
other night-roving creatures, have a thin, iridescent
*
layer of reflecting cells behind the retina called the tapetum. Light strikes its mirror surface and bounces back at the retina, allowing an animal to see in faint light. If you hold a flashlight against your forehead at night and shine its light into the forest or along a swamp or ocean, you’re bound to “shine” the red or amber eyes of some nocturnal creature—a spider, a caiman, a cat, a moth, a bird. Even scallops, with their tiny stuffed-olive-looking eyes, have a tapetum to capture more light, so that late at night they can observe any whelk sneaking up on them. Results of scientific experiments seem to indicate that cold-blooded animals can see better in dim light than warm-blooded ones, so amphibians generally have better night vision than mammals. (In one test conducted by researchers from the University of Copenhagen and the University of Helsinki, humans needed eight times as much light to see a worm at night than a toad did.) Cats, like other predators, have their eyes set squarely in front; they often have relatively big eyes and great depth perception, so that they can sight and track their prey. Consider the owl, a pair of binoculars with wings, whose eyes make up a third of its head size. Arrowhead crabs, bright spiderlike reef creatures familiar to scuba-divers, have eyes set so far apart they can see in almost a complete circle. Horses have little depth perception, because their eyes are placed far around each side of the head. Like prey in general, they need peripheral vision to keep an eye out for an attack from a predator. I’ve always thought it was particularly brave of horses to be willing to take jumps they must lose sight of at the last moment. Predators frequently have vertical pupils, since they look forward for their prey; whereas sheep, goats, and many other hoofed animals, which must be vigilant across the fields in which they graze, have horizontal pupils. An interesting feature of the alligator’s pupil is that it can tilt a little as the angle of the head changes, so that prey will always be in focus. Roadside alligator wrestlers who flip a ’gator over, rub its stomach, and “put it to sleep” are actually giving it a bad case of vertigo. Upside down,
an alligator’s pupils can’t adjust, and the world becomes a confusing tumult of images. Many insects have compound eyes that iridesce, but few are as beautiful as the eye of the goldeneye lacewing: a background of black topped by a perfect six-pointed star, which shimmers blue at its tips, green as you move inward, then yellow, and finally red at the center.

Prairie dogs are color-blind to red and green, owls are entirely colorblind (because they have only rod cells), and ants don’t see red at all. The deer that stroll into my yard to feast on apples and rosebushes see me mainly as shades of gray, as do the rabbits that eat the wild strawberries on my back lawn and are tame enough to kick in the rump. A surprising number of animals do see in color, but the colors they see are different. Unlike us, some also see in infrared, or with radically different kinds of eyes (barred, compound, iridescent, tubular, at the ends of stalks). The world that greets them looks different. Horror films persuaded us that the fly’s compound eye meant that it saw the same image repeated many times, but scientists have now taken pictures through the eyes of insects, and we know that a fly sees a single complete scene, as we do, only a greatly curved one: It would be the equivalent of looking at the world through a glass paperweight. We assume that insects and animals don’t see very well, but birds can see the stars, some butterflies can see in the ultraviolet range, and some jellyfish create their own light to read by. Bees can judge the angle at which light hits their photoreceptors, and therefore locate the position of the sun in the sky, even on a partly cloudy day. There are orchids that look so much like bees that bees try to mate with them, spreading pollen in the process. This intricate and extreme adaptation wouldn’t work if bees’ vision were poor. The reason movies appear to be continuous is that they move at about twenty-four frames per second, whereas we process images at fifty to sixty per second. When we watch a movie, we’re actually watching a blank screen for about half the time. The rest of the time, many still photographs are flashed one after another, each slightly different and yet related to the preceding one. The eye dawdles over each photograph just long enough to slur into the next one, and they seem to be a single continuously moving picture. The
eye persists in linking up the separate images. Bees, on the other hand, are used to images flashing at three hundred per second, so
Lawrence of Arabia
would be just a series of stills to them. It used to be thought that a bee’s “waggle dance” included semaphore instructions for how to get to the great feeding places the bee had just been to; but now scientists think that the waggle dance also conveys messages in touch, smell, and hearing. Although it’s true that bees can see in ultraviolet, they’re weak on the red end of the spectrum, so a white flower looks blue to a bee, and a red flower is of little interest. Moths, birds, and bats, on the other hand, adore red flowers. Flowers that look drab and simple to us—nothing but white petals—to a bee may be lit up like a billboard flanked by neon signs pointing the way to the nectar. Bulls don’t have color vision, so the bright red of the matador’s cape could just as easily be black or orange. Red is for the benefit of the human audience, which finds the color intrinsically arousing and also suggestive of the soon-to-be-flowing blood of either the bull or the matador. The bull just focuses irritably on the large object moving in front of the man and charges.

The Boran people of Kenya are led to honeybees’ nests by the pantomiming of a bird, the African honey guide
(Indicator indicator)
. If the Boran are in the mood for honey, they whistle to call the bird. Or, if the bird is hungry for honey, it flies around the Boran, alerting them with its “
tin-tin-tin
.” Then it disappears briefly, apparently to check on the whereabouts of a honeybee nest, and returns to guide them with short flights and repeated calls. When the bird gets to the nest, it flies down to indicate the right spot and changes its call. Skillfully, the Boran break into the nest and take honey; they leave plenty for the bird, which would otherwise find the nest hard to invade. German ornithologists at the Max-Planck-Institut, who spent three years studying this strange symbiotic relationship, discovered that it takes the tribesmen almost three times as long to find honey without the help of the honey birds. Apparently, the birds also guide honey badgers in a similar way. Animals’ eyes may be quick and keen, but few eyes are as probing as those of the artist, another species of hunter, whose prey lives in both the outer world and the inner tundra.

In his later years, Cézanne suffered a famous paroxysm of doubt about his genius. Could his art have been only an eccentricity of his vision, not imagination and talent guarded by a vigilant esthetic? In his excellent essay on Cezanne in
Sense and Nonsense
, Maurice Merleau-Ponty says: “As he grew old, he wondered whether the novelty of his painting might not come from trouble with his eyes, whether his whole life had not been based upon an accident of the body.” Cézanne anxiously considered each brush stroke, striving for the fullest sense of the world, as Merleau-Ponty describes so well:

Opening up wide to the fullness of life, Cezanne felt himself to be the conduit where nature and humanity met—“The landscape thinks itself in me … I am its consciousness”—and would work on all the different sections of a painting at the same time, as if in that way he could capture the many angles, half-truths, and reflections a scene held, and fuse them into one conglomerate version. “He considered himself powerless,” Merleau-Ponty writes, “because he was not omnipotent, because he was not God and wanted nevertheless to portray the world, to change it completely into a spectacle, to make
visible
how the world
touches
us.” When one thinks of the masses of color and shape in his paintings, perhaps it won’t come as a surprise to learn that Cézanne was myopic, although he refused glasses, reputedly crying “Take those vulgar things away!” He also
suffered from diabetes, which may have resulted in some retinal damage, and in time he developed cataracts (a clouding of the clear lens). Huysmans once captiously described him as “An artist with a diseased retina, who, exasperated by a defective vision, discovered the basis of a new art.” Born into a different universe than most people, Cézanne painted the world his slightly askew eyes saw, but the random chance of that possibility gnawed at him. The sculptor Giacometti, on the other hand, whose long, stretched-out figures look as consciously distorted as one could wish, once confessed amiably: “All the critics spoke about the metaphysical content or the poetic message of my work. But for me it is nothing of the sort. It is a purely optical exercise. I try to represent a head as I see it.”

Quite a lot has been learned in recent years about the vision problems of certain artists, whose eyeglasses and medical records have survived. Van Gogh’s “Irises” sold at Christie’s in 1988 for forty-nine million dollars, which would surely have amused him, since he sold only one painting during his lifetime. Though he was known for cutting off his ear, van Gogh also hit himself with a club, went to many church services each Sunday, slept on a board, had bizarre religious hallucinations, drank kerosene, and ate paint. Some researchers now feel that a few of van Gogh’s stylistic quirks (coronas around streetlamps, for instance) may not have been intentional distortions at all but the result of illness, or, indeed, of poisoning from the paint thinners and resins he used, which could have damaged his eyes so that he saw halo effects around light sources. According to Patrick Trevor-Roper, whose
The World Through Blunted Sight
investigates the vision problems of painters and poets, some of the possible diagnoses for van Gogh’s depression “have included cerebral tumour, syphilis, magnesium deficiency, temporal lobe epilepsy, poisoning by digitalis (given as a treatment for epilepsy, which could have provoked the yellow vision), and glaucoma (some self-portraits show a dilated right pupil, and he depicted coloured haloes around lights).” Most recently, a scientist speaking before a meeting of neurologists in Boston added Geschwind’s syndrome, a personality disorder that sometimes accompanies epilepsy. Van Gogh’s own
doctor said of him: “Genius and lunacy are well known next-door neighbors.” Many of those ailments could have affected his vision. But, equally important, the most brilliant pigments used to include toxic heavy metals like copper, cadmium, and mercury. Fumes and poisons could easily get into food, since painters frequently worked and lived in the same rooms. When the eighteenth-century animal painter George Stubbs went on his honeymoon, he stayed in a two-room cottage, in one room of which he hung up the decaying carcass of a horse, which in free moments he studiously dissected. Renoir was a heavy smoker, and he probably didn’t bother to wash his hands before he rolled a cigarette; paint from his fingers undoubtedly rubbed onto the paper. Two Danish internists, studying the relationship between arthritis and heavy metals, have compared the color choices in paintings by Renoir, Peter Paul Rubens, and Raoul Dufy (all rheumatoid arthritis sufferers), with those of their contemporaries. When Renoir chose his bright reds, oranges, and blues, he was also choosing big doses of aluminum, mercury, and cobalt. In fact, up to 60 percent of the colors Renoir preferred contained dangerous metals, twice the amount used by such contemporaries of his as Claude Monet or Edgar Degas, who often painted with darker pigments made from safer iron compounds.