A Natural History of the Senses

  Schanberg first began his rat experiments as a result of his work in pediatrics; he was especially interested in psychosocial dwarfism. Some children who live in emotionally destructive homes just stop growing. Schanberg found that even growth-hormone injections couldn’t prompt the stunted bodies of such children to grow again, but tender loving care did. The affection they received from the nurses when they were admitted to a hospital was often enough to get them back on the right track. What’s amazing is that the process is reversible at all. When Schanberg’s experiments with infant rats produced identical results, he began to think about human preemies, who are typically isolated and spend much of their early life without human contact. Animals depend on being close to their mothers for basic survival. If the mother’s touch is removed (for as little as forty-five minutes in rats), the infant lowers its need for food to keep itself alive until the mother returns. This works out well if the mother is away only briefly, but if she never comes back, then the slower metabolism results in stunted growth. Touch reassures an infant that it’s safe; it seems to give the body a go-ahead to develop normally. In many experiments conducted all over the country, babies who were held more became more alert and developed better cognitive abilities years later. It’s a little like the strategy one adopts on a sinking ship: First you get into a life raft and call for help. Baby animals call their mothers with a high-pitched cry. Then you take stock of your water and food, and try to conserve energy by cutting down on high-energy activities—growth, for instance.

  At the University of Colorado School of Medicine, researchers conducted a separation experiment with monkeys, in which they removed the mother. The infant showed signs of helplessness, confusion, and depression, and only the return of its mother and continuous holding for a few days would help it return to normal. During separation, changes occurred in the heart rate, body temperature, brain-wave patterns, sleep patterns, and immune system function. Electronic monitoring of deprived infants showed that touch deprivation caused physical and psychological disturbances. But when the mother was put back, only the psychological disturbances seemed to disappear; true, the infant’s behavior reverted to normal, but the physical distresses—susceptibility to disease, and so on—persisted. Among this experiment’s implications is that damage is not reversible, and that the lack of maternal contact may lead to possible long-term damage.

  Another separation study with monkeys took place at the University of Wisconsin, where researchers separated an infant from its mother by a glass screen. They could still see, hear, and smell each other, only touch was missing, but that created a void so serious that the baby cried steadily and paced frantically. In another group, the dividing screen had holes, so the mother and baby could touch through it, which was apparently sufficient because the infants didn’t develop serious behavior problems. Those infants who suffered short-term deprivation became adolescents who clung to one another obsessively instead of developing into independent, confident individuals. When they suffered long-term deprivation, they avoided one another and became aggressive when they did come in contact, violent loners who didn’t form good relationships.

  In University of Illinois primate experiments, researchers found that a lack of touch produced brain damage. They posed three situations: (1) touch was not possible, but all other contact was, (2) for four hours out of twenty-four the glass divider was removed so the monkeys could interact, and (3) total isolation. Autopsies of the cerebellum showed that those monkeys who were totally isolated had brain damage; the same was true of the partially separated animals. The untampered-with natural colony remained undamaged. Shocking though it sounds, a relatively small amount of touch deprivation alone caused brain damage, which was often displayed in the monkeys as aberrant behavior.

  As I rearrange the preemie in his glass home, I notice that on the walls a bright circus design shows clowns, a merry-go-round, tents, balloons, and a repeat banner that says “Wheel of Fortune.” “Touch is far more essential than our other senses,” I recall Saul Schanberg saying when we spoke, on Key Biscayne, at Johnson & Johnson’s extraordinary conference on touch in spring, 1989, a three-day exchange of ideas that brought together neurophysiologists, pediatricians, anthropologists, sociologists, psychologists, and others interested in how touch and touch deprivation affect the mind and body. In many ways, touch is difficult to research. Every other sense has a key organ to study; for touch that organ is the skin, and it stretches over the whole body. Every sense has at least one key research center, except touch. Touch is a sensory system, the influence of which is hard to isolate or eliminate. Scientists can study people who are blind to learn more about vision, and people who are deaf or anosmic to learn more about hearing or smell, but this is virtually impossible to do with touch. They also can’t experiment with people who are born without the sense, as they often do with the deaf or blind. Touch is a sense with unique functions and qualities, but it also frequently combines with other senses. Touch affects the whole organism, as well as its culture and the individuals it comes into contact with. “It’s ten times stronger than verbal or emotional contact,” Schanberg explained, “and it affects damn near everything we do. No other sense can arouse you like touch; we always knew that, but we never realized it had a biological basis.”

  “You mean how adaptive it is?”

  “Yes. If touch didn’t feel good, there’d be no species, parenthood, or survival. A mother wouldn’t touch her baby in the right way unless the mother felt pleasure doing it. If we didn’t like the feel of touching and patting one another, we wouldn’t have had sex. Those animals who did more touching instinctively produced offspring which survived, and their genes were passed on and the tendency to touch became even stronger. We forget that touch is not only basic to our species, but the key to it.”

  As a fetus grows in the womb, surrounded by amniotic fluid, it feels liquid warmth, the heartbeat, the inner surf of the mother, and floats in a wonderful hammock that rocks gently as she walks. Birth must be a rude shock after such serenity, and a mother re-creates the womb comfort in various ways (swaddling, cradling, pressing the baby against the left side of her body where her heart is). Right after birth, human (and monkey) mothers hold their babies very close to their bodies. In primitive cultures, a mother keeps her baby close day and night. A baby born to one of the Pygmies of Zaire is in physical contact with someone at least 50 percent of the time, and is constantly being stroked or played with by other members of the tribe. A Kung! mother carries her baby in a curass, a sling that holds it upright at her side so that it can nurse, play with her bead necklaces, or interact with others. Kung! infants are in touch with others about 90 percent of the time, whereas our culture believes in exiling babies to cribs, baby carriages, or travel seats, keeping them at arm’s length and out of the way.

  An odd feature of touch is that it doesn’t always have to be performed by another person, or even by a living thing. Maternity Hospital in Cambridge, England, discovered that if a premature baby were just placed on a lamb’s-wool blanket for a day it would gain an average of fifteen grams more than usual. This was not due to additional heat from the blanket, since the ward was kept warm, but more akin to the tradition of “swaddling” infants, which increases tactile stimulation, decreases stress, and makes them feel lightly cuddled. In other experiments, snug-fitting blankets or clothes reduced the infants’ heart rate, relaxed them; they slept more often in their womblike bindings.

  All animals respond to being touched, stroked, poked in some way, and, in any case, life itself could not have evolved at all without touch—that is, without chemicals touching one another and forming liaisons. In the absence of touching and being touched, people of all ages can sicken and grow touch-starved.* In fetuses, touch is the first sense to develop, and in newborns it’s automatic before the eyes open or the baby begins to make sense of the world. Soon after we’re born, though we can’t see or speak, we instinctively begin touching. Touch cells in the lips make nur
sing possible, clutch mechanisms in the hands begin to reach out for warmth. Among other things, touch teaches us the difference between I and other, that there can be someone outside of ourselves, the mother. Mothers and infants do an enormous amount of touching. The first emotional comfort, touching and being touched by our mother, remains the ultimate memory of selfless love, which stays with us life long.

  The little three-pound universe named Geoffrey, which I am stroking in long gentle caresses, has idly twisted his mouth and just as quickly untwisted it again. In other incubators around the room, other lives are stirring, other volunteers continue reaching in through portholes to help the infants begin to make sense of the world. The head research nurse of the ward, a graduate student in neonatal care, gives the Brazelton sensory test to a baby boy, who responds to a bright-red egg-rattle. Picking the baby up, she swings it gently around and its eyes go in the direction of the spin, as they should, then return to the midline. Next she rings a small schoolbell for ten seconds at each side, and repeats this four times. It is a very Buddhist scene. In a nearby crib, a preemie who is having his hearing tested wears a headset that makes him look like a telegraph operator. The policy with premature babies used to be not to disturb them any more than necessary, and they lived in a kind of isolation booth, but now the evidence about touch is so plentiful and eloquent that many hospitals encourage touching. “Did you hug your child today?” asks the bumper sticker. As it turns out, this is more than a casual question. Touch seems to be as essential as sunlight.

  WHAT IS A TOUCH?

  Touch is the oldest sense, and the most urgent. If a saber-toothed tiger is touching a paw to your shoulder, you need to know right away. Any first-time touch, or change in touch (from gentle to stinging, say), sends the brain into a flurry of activity. Any continuous low-level touch becomes background. When we touch something on purpose—our lover, the fender of a new car, the tongue of a penguin—we set in motion our complex web of touch receptors, making them fire by exposing them to a sensation, changing it, exposing them to another. The brain reads the firings and stop-firings like Morse code and registers smooth, raspy, cold.

  Touch receptors can be blanked out simply by tedium. When we put on a heavy sweater, we’re acutely aware of its texture, weight, and feel against our skin, but after a while we completely ignore it. A constant consistent pressure registers at first, activating the touch receptors; then the receptors stop working. So wearing wool or a wristwatch or a necklace doesn’t bother us much, unless the day heats up or the necklace breaks. When any change occurs, the receptors fire and we become suddenly aware. Research suggests that, though there are four main types of receptors, there are many others along a wide spectrum of response. After all, our palette of feelings through touch is more elaborate than just hot, cold, pain, and pressure. Many touch receptors combine to produce what we call a twinge. Consider all the varieties of pain, irritation, abrasion; all the textures of lick, pat, wipe, fondle, knead; all the prickling, bruising, tingling, brushing, scratching, banging, fumbling, kissing, nudging. Chalking your hands before you climb onto uneven parallel bars. A plunge into an icy farm pond on a summer day when the air temperature and body temperature are the same. The feel of a sweat bee delicately licking moist beads from your ankle. Reaching blindfolded into a bowl of Jell-O as part of a club initiation. Pulling a foot out of the mud. The squish of wet sand between the toes. Pressing on an angel food cake. The near-orgasmic caravan of pleasure, shiver, pain, and relief that we call a back scratch.* On a cattle ranch some years ago, in birthing season, I helped the cowhands with the herd. Whenever we found a cow in trouble, someone had to reach into her vagina and check her condition. “You’re a female,” they’d invariably say, “you do it,” meaning that I was bound to know, by feel, the internal landscape of another female, even if she was only distantly related to me and her organs were horizontal. “Look for the two big boulders just over a rise …,” a Spanish-American cowhand had said helpfully on one occasion. Up to your shoulder inside a cow, you feel the hot heavy squeeze of her, but I’ll never forget my startled delight the first time I withdrew my hand slowly and felt the cow’s muscles contract and release one after another, like a row of people shaking hands with me in a receiving line. I wonder if this is how it feels to be born. Also, scientists have discovered that most of the nerve receptors will respond to pressure, as well as to whatever they specialize in. For the longest time we assumed that each sensation had its own receptor and that that receptor had its own pathway to the brain, but it looks now as if the body’s grasslands of neurons relate any sensation according to electrical codes. Pain produces irregular bleats from the nerves at jagged intervals. Itching produces a fast, regular pattern. Heat produces a crescendo as the area heats up. A little pressure produces a flurry of excitement, then fades, and a stronger pressure just extends the burst of activity.

  After a while, as suggested, a touch receptor “adapts” to the stimuli and stops responding, which is just as well or we would be driven crazy by the feel of a light sweater against the skin on a cool summer’s evening, or go berserk if a breeze didn’t quit. This fatigue doesn’t happen among the deep Pacinian corpuscles and Ruffini’s organs (joints) or the Golgi’s organs (tendons), which give us information about our internal climate, because if they nodded we would fall down midstride. But the other receptors, so alert at first, so hungry for novelty, after a while say the electrical equivalent of “Oh, that again,” and begin to doze, so we can get on with life. We may feel self-conscious much of the time, but we’re not often conscious of our physical selves, or we’d be exhausted in a typhoon of sensation.

  Some forms of touch irritate and delight us simultaneously. Tickling may be a combination of the signals for, say, pressure and pain. Wetness may be a mix of temperature and pressure. But when we lose touch (the dentist gives you a shot of novocaine; an arm or leg falls asleep from lowered blood supply), we feel odd and alien. Imagine how frightening it must be to lose touch permanently. Touch loss can be maddeningly specific: A person loses a sense of temperature, or of pain. When my dentist gave me a shot of Carbocaine, my jaw dropped like a slab of pottery. I could still feel pressure and temperature—though the temperature sensation was reversed (ice water tasted like water but felt hot)—but I no longer felt any level of pain in the jaw. The absence of pain’s minute markers—a scratch, a pinch, a twinge—made the flesh feel cadaverous. In St. Louis, Missouri, one day a couple of years ago, I was going to a reading with novelist Stanley Elkin, who has suffered from MS for many years. Stanley could still drive, and we decided to take his car. But when we got to it and he went around to the driver’s door, he stopped and stood for what seemed ages, groping in his pocket. Finally he pulled out the entire contents of the pocket and set it all on the car hood so he could see his keys. Many sufferers of MS can feel an object in their pocket (a set of car keys), but they can’t identify it by touch. The brain won’t decode the shape correctly. As those who are simultaneously deaf and blind have shown, it’s possible to get on predominantly by touch, but to be without touch is to move through a blurred, deadened world, in which you could lose a leg and not know it, burn your hand without feeling, and lose track of where you stop and the featureless day begins.

  THE CODE SENDERS

  It takes a troupe of receptors to make the symphonic delicacy we call a caress. Between the epidermis and the dermis lie tiny egg-shaped Meissner’s corpuscles, which are nerves enclosed in capsules. They seem to specialize in hairless parts of the body—the soles of the feet, fingertips (which have 9,000 per square inch), clitoris, penis, nipples, palms, and tongue—the erogenous zones and other ultrasensitive ports of call—and they respond fast to the lightest stimulation. Inside a Meissner corpuscle, like the many filaments inside a light bulb, branching, looping nerve endings lie parallel to the surface of the skin and pick up a wealth of sensation. Their parallel arrangement may make them especially sensitive to something touching them at a perpendicular angle. Furt
hermore, they are extremely specific because each area of the corpuscle can respond independently. As one researcher describes it, “It’s as though the receptor were composed of separate coils like an innerspring mattress; one can be depressed without disturbing the others.” What they record is low-frequency vibrations, the feeling of a finger stroking a beautifully woven sari, for example, or the soft angled skin inside another’s elbow.

  The Pacinian corpuscles respond very quickly to changes in pressure, and they tend to lie near joints, in some deep tissues, and in the genitals and mammary glands. Thick, onion-shaped sensors, they tell the brain what is pressing and also about the movement of joints or how the organs may be shifting their position when we move. It doesn’t take much pressure to make them respond fast and rush messages to the brain. But they’re also adept with vibrating or varying sensations, especially high-frequency ones (a violin string, for instance); indeed, it may be the onionlike layers of the corpuscle that decipher differing vibrations so well. What the Pacinian corpuscles do is convert mechanical energy into electrical energy, as Bernhard Katz of University College, London, showed in 1950 in electrical experiments with muscles. Subsequent research has led to a better understanding of this process, as Donald Carr describes in The Forgotten Senses: