The Experience of Touch: Research Points to a Critical Role
THE experience of being touched, new research shows, has direct and crucial effects on the growth of the body as well as the mind.
Touch is a means of communication so critical that its absence retards growth in infants, according to researchers who are for the first time determining the neurochemical effects of skin-to-skin contact.
The new work focuses on the importance of touch itself, not merely as part of, say, a parent's loving presence. The findings may help explain the long-noted syndrome in which infants deprived of direct human contact grow slowly and even die.
Psychological and physical stunting of infants deprived of physical contact, although otherwise fed and cared for, had been noted in the pioneering work of Harry Harlow, working with primates, and the psychoanalysts John Bowlby and Renee Spitz, who observed children orphaned in World War II.
The new research suggests that certain brain chemicals released by touch, or others released in its absence, may account for these infants' failure to thrive.
The studies on the physiology of touch come against a backdrop of continuing research on the psychological benefits of touch for emotional development.
In some of the most dramatic new findings, premature infants who were massaged for 15 minutes three times a day gained weight 47 percent faster than others who were left alone in their incubators - the usual practice in the past. The massaged infants also showed signs that the nervous system was maturing more rapidly: they became more active than the other babies and more responsive to such things as a face or a rattle.
''The massaged infants did not eat more than the others,'' said Tiffany Field, a psychologist at the University of Miami Medical School, who did the study. ''Their weight gain seems due to the effect of contact on their metabolism.''
The infants who were massaged were discharged from the hospital an average of six days earlier than premature infants who were not massaged, saving about $3,000 each in hospital costs, Dr. Field said.
Eight months later, long after their discharge, the massaged infants did better than the infants who were not on tests of mental and motor ability and held on to their advantage in weight, according to a report by Dr. Field in The Journal of Pediatrics.
''The standard policy in caring for premature infants has been a minimal-touch rule,'' Dr. Field said. Word of her continuing findings and others that support them has led to a change in this policy in some hospitals.
Babies born prematurely are kept in incubators and fed intravenously. They had been touched as little as possible because they had been observed becoming agitated when someone approached or handled them. The agitation sometimes put a dangerous strain on their tiny lungs, putting the infants in danger of hypoxia, an inability to oxygenate the blood.
However, Dr. Field found that a light massage of the babies' backs, legs and necks and gentle movement of their arms and legs proved to have a tonic effect, immediately soothing them and eventually speeding their growth.
Dr. Field had decided to try massages because of findings by Saul Schanberg of the department of pharmacology at Duke University. Beta-Endorphin Inhibited
The strongest evidence is from studies of other mammals, but it seems to apply to humans. Dr. Schanberg's studies of infant laboratory rats showed that a particular pattern of touch by the mother rat - particularly licking - inhibited the infant rat's production of beta-endorphin, a chemical that affects the levels of insulin and growth hormone.
The slowed production of beta-endorphin did not depend on the presence of the mother; researchers were able to induce it by simulating the stroke of the mother's rough tongue with a wet paintbrush.
While levels of beta-endorphin decreased in response to licking, the levels rose when the infants were taken from their mothers. If the separation persisted, the infant rats' growth was stunted.
But resumption of the mother's touch, even when simulated with a brush, again lowered the beta-endorphin levels and quickened growth.
''We believe that the brain effects we found in rats will also hold for humans, because the basic neural and touch systems are the same,'' Dr. Schanberg said. Primitive Survival Mechanism
He hypothesizes that the touch system is part of a primitive survival mechanism found in all mammals. Because mammals depend on maternal care for survival in their early weeks or months, the prolonged absence of a mother's touch - more than 45 minutes in a rat, for instance - triggers a slowing of the infant's metabolism, and thus a lowering of its need for nourishment. Such a reaction heightens its chances of surviving until it is once again in contact with the mother.
While the slower metabolism is beneficial in the short term, it stunts growth if very prolonged. According to Dr. Schanberg, part of the response in rats, which includes huddling down and becoming still, is a change in metabolism that conserves the store of energy and slows the rate of growth. The mother's touch, however, reverses the process, so that growth resumes at normal rates.
In related findings, physical contact with the mother appears essential to reducing the release of hormones by an infant when subjected to stress, according to Seymour Levine, a psychologist in the department of psychiatry at Stanford University Medical School. When infant rats or monkeys are separated from their mothers, activity in the pituitary-adrenal system rises, a response that is also typical for humans under stress. In Dr. Levine's studies, physical contact with the infant's mother lowered this stress response. Beyond Mere Proximity
Contact and touch have a significant role in the infant's ability ''to regulate its own responses to stress,'' Dr. Levine said. His work does not allow him to separate touch in itself from the more general effect of the mother's presence, but he theorizes that in humans a touch-induced reduction of stress hormones may account for the soothing effects of skin-to-skin contact.
In an article published in a recent issue of Child Development, Dr. Schanberg and Dr. Field review data indicating that it was touch, rather than mere proximity or motion, that regulated infants' growth rate.
Other research suggests that all babies benefit from touch, not just the premature infants Dr. Field studied. Research by Theodore Wacks, a psychologist at Purdue, showed that infants who experienced more skin-to-skin contact had an advantage in mental development in the first six months of life. The Best Kind of Touch
Such findings have encouraged the formation of some infant massage groups outside of hospitals, for parents to learn the best ways to massage their babies. The best stroke for an infant, Dr. Field said, is gentle, firm and slow. If the touch is too light, it can overstimulate and even irritate an infant.
Different areas of an infant's body respond differently to touch. If a parent wants to soothe an infant, gentle strokes or light massage on its back and legs will relax it. On the other hand, stroking a baby's face, belly or feet tends to stimulate it.
''In most parts of the world, people massage babies,'' said Dr. Field. ''The Western countries are about the only place this is not routine.''
The primacy of touch in infancy, experts say, is tied to touch's being the most mature sensory system for the first several months of life.
''It's the first way an infant learns about the environment,'' said Kathryn Barnard, a professor of nursing at the University of Washington. ''About 80 percent of a baby's communication is through its body movement. It's easier to read a baby's communication with skin-to-skin contact.'' Conveying Subtle Needs
Babies resort to crying when their needs become urgent, while they use movements to show more subtle feelings and needs, Dr. Barnard said.
Her research has shown that the more a mother holds her baby the more aware she is of the baby's needs. And Dr. Barnard found that those infants who were held more showed superior cognitive development as long as eight years later, apparently because they were more alert.
''We touch each other too little,'' Dr. Field said. ''Body contact is very beneficial between parents and children right up to adolescence.'' Psychological Development
While a warm touch is part of loving contact and is difficult to separate from it, research is suggesting that touch has an importance over and above other expressions of affection and that its presence has consequences for psychological development.
For instance, physical contact is the ultimate signal to infants or small children that they are safe. When a small child is frightened, for instance, the most effective way to calm him is for someone he trusts to hold him; simply being there or reassuring him is not enough, touch researchers believe.
In addition, ''how - and whether -parents touch their children may influence how they feel about their bodies,'' said Sandra Weiss, a professor in the department of mental health and community nursing at the University of California medical school at San Francisco.
In a study of how families of children 7 to 10 years old play together, Dr. Weiss found that rough-housing seemed to give children more positive feelings about themselves and a more accurate sense of their bodies. To measure the perceptions, the children are asked what they like about their bodies, then they are asked to draw a body.
''The physical play gives a child the message, 'I like to be close to you; it's fun to be around you,' '' Dr. Weiss said. ''It affects both their feelings about themselves and about how they are put together.'' Individual Differences
People differ, however, in the intensity of physical contact they find comfortable. While some of the difference may be an innate property of the person's nervous system, some of it may be shaped by the experience of being touched or not being touched.
Work in rats by Marion Diamond, a professor of anatomy at the University of California at Berkeley, showed that those who had more tactile experience had better-developed nerve cells in the area of the cortex that processes the sensations of touch. Lack of that experience, however, led to a decrease of the richness of connection and size of those brain cells.
''People who touch little, as opposed to those who like to cuddle,'' Dr. Diamond said, ''probably experience the same effect. Those who have had little physical contact over the years might become hypersensitive to such touch, so that they found it physically uncomfortable.''
Why humans and animals rely on touch
When you run your hands through your lover’s hair, you’re probably not thinking about your place in the social hierarchy. Give your team-mate or colleague a pat on the back after a setback, and the chances are you’re not consciously seeking to change the mix of signalling chemicals in their brain. It may not seem like it, but these socially important rituals and others like them predate the time our species first walked the African savannah.
Human behaviours that involve physical social contact have a lot more in common with social grooming activities we typically associate with other species than we might initially think. When rhesus monkeys or chimpanzees pick through their friends' fur, they're not just helping them remove dirt and parasites from hard to reach spots. There is undoubtedly a hygienic benefit, but this behaviour, which animal behaviour researchers call “allogrooming”, has far greater significance. The gelada baboon, for example, spends 17% of its waking hours doing this when just 1% would be sufficient to achieve good hygiene, according to one estimate. Allogrooming is the currency of what primatologist Frans de Waal calls the "marketplace of services" in chimpanzee life: it defines the social hierarchy, which in turn dictates access to food, sex, and social support.
For example, one chimpanzee is more likely to share food with another that has previously groomed it. Grooming also serves to ease tensions in a chimp troop following an aggressive situation. One of the most complex forms of reconciliation among chimpanzees occurs when two rival males reach a point of stalemate, neither backing down nor escalating the aggressive interaction. Sometimes, a female breaks the deadlock and eases the tension by grooming first one male, and then the other, until the two become relaxed enough to end what amounted to an angry staring contest.
According to anthropologist Robin Dunbar, this works because grooming stimulates the release of endorphins – opiates produced by the brain that trigger feelings of relaxation by lowering the heart rate, reducing overt nervous behaviours like scratching, and even bringing on sleep. Female chimps that use grooming as a peacekeeping strategy may also experience their own rush of endorphins and enjoy many of the same benefits.
Humans, lacking the fur of our more hirsute evolutionary cousins, had to find a replacement for allogrooming. Like grooming, gossip establishes and maintains our place in the social hierarchy. Also like grooming, the social information that makes up gossip is itself a form of currency in human culture. Or, at least, that's the theory put forward by Dunbar. He argued, in his book Grooming, Gossip and the Evolution of Language, that the faculty of language allowed our species to substitute gossip for grooming.
Pleasure principle
But grooming, and related forms of social physical contact, hasn't gone away entirely. While we humans don't make a habit of picking through our friends' hair for parasites – nurses searching for lice on the first day of summer camp notwithstanding – the truth is that gossip hasn't completely replaced our need for physical touch. Indeed, words don't always make adequate tools for communicating our feelings. Far more can be said by a heartfelt hug or squeeze on the shoulder after a friend suffers the loss of a relative than through words.
In the same way, one's love and desire for a partner can be conveyed with a seductive stroke far more effectively than even the words "I want you" ever could. Indeed, Dunbar writes, "the physical stimulation of touch tells us more about the inner feelings of the 'groomer', and in a more direct way" than words are able. And those forms of touch stimulate within us the same endorphin release that chimpanzees enjoy during social grooming.
Some scientists have even gone as far as calling the skin a "social organ". This makes good intuitive sense: we both crave touch and are repulsed by it when it is unwanted, uninvited, or inappropriate. Even simple, brief touches on a hand or arm can have tremendous effects. India Morrison and colleagues at Goteborg University, in Sweden, have presented a laundry list of such findings. Hand-on-hand touches by librarians and salespersons have, for example, been found to lead to more favourable impressions of libraries and shops. People perceive others as more attractive following even a simple, non-sexual touch, and as a result are more likely to act altruistically by returning change left in a pay phone, giving bigger tips in restaurants, or giving away a cigarette to a stranger.
And yet these effects might be thought of as simple parlour tricks compared to the power that touch has between lovers, or between parents and their children.
In one study, US psychologists investigated social grooming in humans by asking participants to indicate their closest emotional relationship and report behaviours such as running their fingers through the person’s hair, wiping away their tears, scratching their back and non-sexual massage. They found levels of relationship satisfaction and trust were both positively correlated with self-reported grooming frequency among romantic partners. And one finding hinted at a causal relationship: people who were more anxious about their relationships "groomed" their partners more often than those who felt more secure with their partners, suggesting that grooming may serve to reduce relationship-related anxiety and to promote the development of romantic bonds. The pattern was true both for men and women.
Survival instinct
Babies also crave touch. It has long been known among animal behaviour researchers that physical contact is critical for proper social and emotional development. When developmental psychologist Harry Harlow deprived infant rhesus monkeys of access to a monkey mother in his 1950s experiments at the University of Wisconsin-Madison, they became withdrawn, depressed, and anxious. They refused food, and entered into what he called a "state of emotional shock." When allowed access to a surrogate mother, the infant monkeys overwhelmingly chose the tactile sensations provided by a doll covered by terry cloth over a wire doll that provided food and water. The young monkeys preferred the comfort of even an inanimate mother's touch to physical sustenance.
More recent research with rats replicates Harlow's early findings. Canadian researchers found that when infant rats were licked and groomed more by their mothers, they grew up to be relatively well adjusted. But their counterparts who were deprived of grooming often grew up, like Harlow's monkeys, to be anxious and fearful. Touch-deprived rats also had weakened immune systems. It appears as if touch helps to maintain not only social and emotional health, but also physical health.
According to the World Health Organization, more than 20 million infants each year are born pre-term, which means that they weigh less than 5lb 8oz (2.5kg) upon birth. These babies have increased risk of death in the first few weeks of life. Caring for low-birth-weight infants in hospitals is expensive and requires highly skilled personnel, however research suggests a therapy called kangaroo care is both cheaper and just as effective. Originally developed in Bogota, Colombia, as a way of keeping preterm infants warm in overcrowded nurseries, the practice is deceptively simple. The mother or father simply has to repeatedly place their baby against their bare chest, ideally for prolonged periods.
A meta-analysis of three randomised control trials (the gold standard in biomedical research), conducted in Colombia, Bangladesh, Ethiopia, Indonesia and Mexico found that babies born weighing 4lb 6oz (2kg) or less given kangaroo care in the first week of life were 51% less likely to die in the first four weeks after birth, compared with infants who received standard care.
Other research has found that kangaroo care helps to stabilise preterm infants' vital signs, maintains adequate oxygen levels in the blood, and helps them to sleep better. It also reduces crying, increases weight gain, and allows preterm infants to spend fewer days in incubators, ultimately allowing them to be discharged from neonatal intensive care units sooner than those who are treated with conventional care.
All primates, from monkey to man, rely on social touch. Among non-human primates, grooming is a tool used to garner favours, earn social standing, and increase access to resources. Gossip may have replaced parasite removal as a mechanism for defining and enhancing one's place in human society, but the desire to be touched is carved so deeply within our primate heritage that it remained even as we shed our fur. For an infant born prematurely, social touch can literally mean the difference between life and death. For the rest of us, being touched simply reminds us that we are loved.
Article source: http://www.bbc.com/future/story/20131014-the-touching-moments-we-all-need
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https://learn.genetics.utah.edu/content/epigenetics/rats/
