A Natural History of the Senses

by Diane Ackerman

  For convenience, and perhaps in a kind of mental pout about how thickly demanding just being alive is, we say there are five senses. Yet we know there are more, should we but wish to explore and canonize them. People who dowse for water are probably responding to an electromagnetic sense we all share to a greater or lesser degree. Other animals, such as butterflies and whales, navigate in part by reading the earth’s magnetic fields. It wouldn’t surprise me to learn that we, too, have some of that magnetic awareness. We were nomads for so much of our history. We are as phototropic as plants, smitten with the sun’s light, and this should be considered a sense separate from vision, with which it has little to do. Our experience of pain is quite different from the other worlds of touch. Many animals have infrared, heat-sensing, electromagnetic, and other sophisticated ways of perceiving. The praying mantis uses ultrasonics to communicate. Both the alligator and the elephant use infrasonics. The duckbill platypus swings its bill back and forth underwater, using it as an antenna to pick up electrical signals from the muscles of the crustaceans, frogs, and small fish on which it preys. The vibratory sense, so highly developed in spiders, fish, bees, and other animals, needs to be studied more in human beings. We have a muscular sense that guides us when we pick up objects—we know at once that they are heavy, light, solid, hard, or soft, and we can figure out how much pressure or resistance will be required. We are constantly aware of a sense of gravity, which counsels us about which way is up and how to rearrange our bodies if we’re falling, or climbing, or swimming, or bent at some unusual angle. There is the proprioceptive sense, which tells us what position each component of our bodies is in at any moment in our day. If the brain didn’t always know where the knees or the lungs were, it would be impossible to walk or breathe. There seems to be a complex space sense that, as we move into an era of space stations and cities and lengthy space travel, we will need to understand in detail. Prolonged Earthlessness alters our physiology and also the evidence of our senses, in part because of the rigors of being in zero gravity,* and in part because of the lidless sprawl of deep space itself, in which there are few sensory handrails, guides or landmarks, and everywhere you look there is not scene but pure vista.

  Species evolve senses fine-tuned for different programs of survival, and it’s impossible to put ourselves into the sensory realm of any other species. We’ve evolved unique human ways of perceiving the world to cope with the demands of our environment. Physics sets the limits, but biology and natural selection determine where an animal will fall among all the sensory possibilities. When scientists, philosophers, and other commentators speak of the real world, they’re talking about a myth, a convenient fiction. The world is a construct the brain builds based on the sensory information it’s given, and the information is only a small part of all that’s available. We can modify our senses through bat detectors, binoculars, telescopes, and microscopes, broadening that sensory horizon, and there are instruments that allow us to become a kind of sensory predator that natural selection never meant us to be. Physicists explain that molecules are always moving: The book in front of you is actually squirming under your fingertips. But we don’t see this motion at that molecular level, because it’s not evolutionarily important that we do. We’re given only the sensory information crucial to our survival.

  Evolution didn’t overload us with unnecessary abilities. For example: We may use numbers in the millions and trillions, but they are basically meaningless to us. Many things are unavailable to us because they’re not part of our distant evolutionary background. In an odd way, one-celled animals may have a more realistic sense of the world than higher animals do, because they respond to every stimulus they encounter. We, on the other hand, select only a few. The body edits and prunes experience before sending it to the brain for contemplation or action. Not every whim of the wind triggers the hair on the wrist to quiver. Not every vagary of sunlight registers on the retina. Not everything we feel is felt powerfully enough to send a message to the brain; the rest of the sensations just wash over us, telling us nothing. Much is lost in translation, or is censored, and in any case our nerves don’t all fire at once. Some of them remain silent, while others respond. This makes our version of the world somewhat simplistic, given how complex the world is. The body’s quest isn’t for truth, it’s for survival.

  Our senses also crave novelty. Any change alerts them, and they send a signal to the brain. If there’s no change, no novelty, they doze and register little or nothing. The sweetest pleasure loses its thrill if it continues too long. A constant state—even of excitement—in time becomes tedious, fades into the background, because our senses have evolved to report changes, what’s new, something startling that has to be appraised: a morsel to eat, a sudden danger. The body takes stock of the world like an acute and observant general moving through a complex battleground, looking for patterns and stratagems. So it is not only possible but inevitable that a person will grow used to a city’s noises and visual commotion and not register these stimuli constantly. On the other hand, novelty itself will always rivet one’s attention. There is that unique moment when one confronts something new and astonishment begins. Whatever it is, it looms brightly, its edges sharp, its details ravishing, in a hard clear light; just beholding it is a form of revelation, a new sensory litany. But the second time one sees it, the mind says, Oh, that again, another wing walker, another moon landing. And soon, when it’s become commonplace, the brain begins slurring the details, recognizing it too quickly, by just a few of its features; it doesn’t have to bother scrutinizing it. Then it is lost to astonishment, no longer an extraordinary instance but a generalized piece of the landscape. Mastery is what we strive for, but once we have it we lose the precarious superawareness of the amateur. “It’s old hat,” we say, as if such an old, weatherbeaten article of clothing couldn’t yield valuable insights about its wearer and the era in which it was created and crushed. “Old news,” we say, even if the phrase is an oxymoron. News is new and should sound an alarm in our minds. When it becomes old, what happens to its truth? “He’s history,” we say, meaning that someone is no longer new for us, no longer fresh and stimulating, but banished to the world of fossil and ruin. So much of our life passes in a comfortable blur. Living on the senses requires an easily triggered sense of marvel, a little extra energy, and most people are lazy about life. Life is something that happens to them while they wait for death. Many millennia from now, will we evolve into people who will perceive the world differently, employ the senses differently, and perhaps know the world more intimately? Or will those future souls, perhaps further away from any physical sense of the world, envy us, the passionate and thrill-seeking ones, who gorged ourselves on life, sense by sense, dream by dream?

  Hold a glance a little longer than usual, let the eyes smolder and a smile creep onto the lips, and a small toboggan run forms in the chest as the heart gets ready to race. Novelty plays a large role in sexual arousal, as e. e. cummings, a master of sensuality and titivation, suggests in his poem “96”:

  i like my body when it is with your

  body. It is so quite new a thing.

  Muscles better and nerves more.

  i like your body, i like what it does,

  i like its hows, i like to feel the spine

  of your body and its bones, and the trembling

  firm-smooth ness and which i will

  again and again and again

  kiss, i like kissing this and that of you,

  i like, slowly stroking the shocking fuzz

  of your electric fur, and what-is-it comes

  over parting flesh.… And eyes big love-crumbs,

  and possibly i like the thrill

  of under me you so quite new

  When cummings wrote this beautiful love sonnet, he certainly didn’t know (or need to) that studies would later reveal how men’s testosterone levels jump when a new woman enters the room. The simple fact of her novelty is physically exciting. But the same is true f
or women and their hormones when a new man enters the room. For social, moral, esthetic, parental, religious, or even mystical reasons, we may choose to live with one partner for life, but our instincts nag at us. There is nothing like the thrill of being new for someone. And even though everything related to love—the roller coaster of flirtation, the thrust and parry of courtship, the razzle-dazzle of lovemaking—has probably evolved so that two people who have a good chance of producing and raising hearty offspring will find each other and mate with a strong biological sense of purpose, we don’t always feel obliged to play by nature’s rules. The challenge (and highwire fun) of love is finding ways to make each day a fresh adventure with one’s partner.

  Life teaches us to be guarded. We use words like vulnerable when we mean that we are letting down a drawbridge over the moat of our self-protection and trusting another inside the fortress of our lives. Lovers combine their senses, blend their electrical impulses, help sense for one another. When they touch, their bodies double in size. They get under each other’s skin, literally and emotionally. During intercourse, a man hides part of himself in a woman, a bit of his body disappears from view, while a woman opens up the internal workings of her body and adds another organ to it, as if it were meant to be there all along. These, in a starched, stiff, dangerous world, are ultimate risks.

  But suppose you could sense any world you wanted to? At NASA’s Ames Research Center, in Mountain View, California, researchers have been perfecting “Virtual Reality” garb—a mask and gloves that extend one’s senses, which are, both in appearance and power, reminiscent of the magic regalia heroes sometimes relied on in epic sagas. Don the sensor-equipped gloves, and you can reach into a computer-generated landscape and move things around. Wear the mask, and you can see an invisible or imaginary world as if it were perfectly viewable, full of depth and color—it might be the rolling sand dunes of Mars, or an approach to O’Hare Airport in fog, or perhaps a faulty space station generator. Why watch a murder mystery from across a room, when you can put on a mask and glove and walk right into the action and handle the clues. How could such a sleight of hand, mind, mask, and senses be possible?

  One of the most profound paradoxes of being human is that the thick spread of sensation we relish isn’t perceived directly by the brain. The brain is silent, the brain is dark, the brain tastes nothing, the brain hears nothing. All it receives are electrical impulses—not the sumptuous chocolate melting sweetly, not the oboe solo like the flight of a bird, not the tingling caress, not the pastels of peach and lavender at sunset over a coral reef—just impulses. The brain is blind, deaf, dumb, unfeeling. The body is a transducer (from Latin, transducere, to lead across, transfer), a device that converts energy of one sort to energy of another sort, and that is its genius. Our bodies take mechanical energy and convert it to electrical energy. I touch the soft petal of a red rose called “Mr. Lincoln,” and my receptors translate that mechanical touch into electrical impulses that the brain reads as soft, supple, thin, curled, dewy, velvety: rose petal-like. When Walt Whitman said: “I sing the body electric,” he didn’t know how prescient he was. The body does indeed sing with electricity, which the mind deftly analyzes and considers. So, to some extent, reality is an agreed-upon fiction. How silly, then, that philosophers should quarrel about appearance and reality. The universe will be knowable to other creatures in other ways.

  A dolphin has a brain as complex as our own; it has language, culture, and emotions. It has its own society, with codes of conduct, family groups, and a civilization, but it lives in a world on “our” planet, as we like to say with chauvinistic bravado, unimaginably different from our own. We may have much to learn from it. Deep down, we know our devotion to reality is just a marriage of convenience, and we leave it to the seers, the shamans, the ascetics, the religious teachers, the artists among us to reach a higher state of awareness, from which they transcend our rigorous but routinely analyzing senses and become closer to the raw experience of nature that pours into the unconscious, the world of dreams, the source of myth. “How do you know but that every bird that cleaves the aerial way is not an immense world of delight closed to your senses five?” William Blake wrote. We have much to learn from and about the senses of animals. Otherwise, how shall we hope to be good caretakers of the planet, should that turn out to be our role? How shall we appreciate our small part in the web of life on Earth? How shall we understand the minds of extraterrestrials, if we make contact with them? How shall we come to know one another deeply, compassionately, fulfillingly, unless we learn more of how the mind and senses work? Our several senses, which feel so personal and impromptu, and seem at times to divorce us from other people, reach far beyond us. They’re an extension of the genetic chain that connects us to everyone who has ever lived; they bind us to other people and to animals, across time and country and happenstance. They bridge the personal and the impersonal, the one private soul with its many relatives, the individual with the universe, all of life on Earth. In REM sleep, our brain waves range between eight and thirteen hertz, a frequency at which flickering light can trigger epileptic seizures. The tremulous earth quivers gently at around ten hertz. So, in our deepest sleep, we enter synchrony with the trembling of the earth. Dreaming, we become the Earth’s dream.

  It began in mystery, and it will end in mystery. However many of life’s large, captivating principles and small, captivating details we may explore, unpuzzle, and learn by heart, there will still be vast unknown realms to lure us. If uncertainty is the essence of romance, there will always be enough uncertainty to make life sizzle and renew our sense of wonder. It bothers some people that no matter how passionately they may delve, the universe remains inscrutable. “For my part,” Robert Louis Stevenson once wrote, “I travel not to go anywhere, but to go. I travel for travel’s sake. The great affair is to move.” The great affair, the love affair with life, is to live as variously as possible, to groom one’s curiosity like a high-spirited thoroughbred, climb aboard, and gallop over the thick, sun-struck hills every day. Where there is no risk, the emotional terrain is flat and unyielding, and, despite all its dimensions, valleys, pinnacles, and detours, life will seem to have none of its magnificent geography, only a length. It began in mystery, and it will end in mystery, but what a savage and beautiful country lies in between.

  *For example, the face swells as body fluids drift upward, and the brain signals the body to get rid of this excess fluid by urinating more and drinking less.

  FURTHER READING

  GENERAL

  Bachelard, Gaston. The Poetics of Space. Boston: Beacon Press, 1969.

  Bates, H. E. The Purple Plain. London: Penguin Books, 1974.

  Bodanis, David. The Secret House. New York: Simon & Schuster, Inc., 1986.

  Bonner, John Tyler. The Scale of Nature. New York: Harper & Row, 1969.

  Brash, R. How Did It Begin? Supersitions and Their Romantic Origins. Australia: Longmans, Green & Co., Ltd., 1965.

  Braudel, Fernand. The Structures of Everyday Life. New York: Harper & Row, 1982.

  Buddenbrock, Wolfgang von. The Senses. Ann Arbor, Michigan: The University of Michigan Press.

  Campbell, Joseph. The Power of Myth. Betty Sue Flowers, ed., introduction by Bill Moyers. Garden City, New York: Doubleday, 1988.

  Carcopino, Jerome. Daily Life in Ancient Rome. Harry T. Lowell, ed. New Haven, Connecticut: Yale University Press, 1940.

  Carr, Donald E. The Forgotten Senses. Garden City, New York: Doubleday, 1972.

  Dubkin, Leonard. The White Lady. London: Macmillan & Co., Ltd., 1952.

  Eiseley, Loren. The Immense Journey. New York: Random House, Inc./Vintage Books, 1957.

  ——. The Lost Notebooks of Loren Eiseley. Kenneth Hever, ed. Boston. Little, Brown & Co., 1987.

  Froman, Robert. The Many Human Senses. London: G. Bell and Sons, Ltd., 1966.

  Gass, William. On Being Blue. Boston: Godine, 1976.

  Glassner, Barry. Bodies: Why We Look the Way We Do. New York: G. P
. Putnam’s Sons, 1988.

  Guiness, Alma E., ed. ABC’s of the Human Body. Pleasantville, New York: Reader’s Digest Books, 1987.

  Huizinga, Johan. Homo Ludens: A Study of the Play Element in Culture. Boston: Beacon Press, 1955.

  Huysmans, J.-K. Against Nature. New York: Penguin Books, 1986.

  Lingis, Alphonso. Excesses: Eros and Culture. Albany, New York: State University of New York, 1978.

  Maeterlinck, Maurice. The Life of the Bee. New York: New American Library, 1954.

  Martin, Russell. Matters Gray & White. New York: Fawcett/Crest, 1986.

  Milne, Lorus and Margery. The Senses of Animals and Men. New York: Atheneum, 1964.

  Morris, Desmond. Bodywatching. New York: Crown, 1985.

  ——. Catwatching. New York: Crown, 1986.

  ——. Dogwatching. New York: Crown, 1987.

  ——. Intimate Behavior. New York: Bantam, 1973.

  ——. Manwatching. New York: Abrams, 1977.

  Murchie, Guy. The Seven Mysteries of Life: An Exploration in Science and Philosophy. Boston: Houghton Mifflin Company, 1978.

  Panati, Charles. The Browser’s Book of Beginnings. Boston: Houghton Mifflin Company, 1984.

  ——. Extraordinary Origins of Everyday Things. New York: Harper &Row, 1987.

  Parker, Arthur C. Indian How Book. New York: Dover, 1954.

  Polhemus, Ted, ed. The Body Reader: Social Aspects of the Human Body. New York: Pantheon Books, 1978.

  Poole, Robert M., ed. The Incredible Machine. Washington, D.C.: National Geographic Society, 1986.

  Rilke, Rainer Maria, trans. G. Craig Houston. Where Silence Reigns: Selected Prose. New York: New Directions, 1978.

  Rivlin, Robert, and Karen Gravelle. Deciphering the Senses: The Expanding World of Human Perception. New York: Simon & Schuster, 1984.