| Taking Play Seriously pt I | 21/03/2008 |
| On a drizzly Tuesday night in late January, 200 people came out to hear a psychiatrist talk rhapsodically about play — not just the intense, joyous play of children, but play for all people, at all ages, at all times. (All species too; the lecture featured touching photos of a polar bear and a husky engaging playfully at a snowy outpost in northern Canada.) Stuart Brown, president of the National Institute for Play, was speaking at the New York Public Library’s main branch on 42nd Street. He created the institute in 1996, after more than 20 years of psychiatric practice and research persuaded him of the dangerous long-term consequences of play deprivation. In a sold-out talk at the library, he and Krista Tippett, host of the public-radio program ‘‘Speaking of Faith,’’ discussed the biological and spiritual underpinnings of play. Brown called play part of the ‘‘developmental sequencing of becoming a human primate. If you look at what produces learning and memory and well-being, play is as fundamental as any other aspect of life, including sleep and dreams.’’ The message seemed to resonate with audience members, who asked anxious questions about what seemed to be the loss of play in their children’s lives. Their concern came, no doubt, from the recent deluge of eulogies to play . Educators fret that school officials are hacking away at recess to make room for an increasingly crammed curriculum. Psychologists complain that overscheduled kids have no time left for the real business of childhood: idle, creative, unstructured free play. Public health officials link insufficient playtime to a rise in childhood obesity. Parents bemoan the fact that kids don’t play the way they themselves did — or think they did. And everyone seems to worry that without the chance to play stickball or hopscotch out on the street, to play with dolls on the kitchen floor or climb trees in the woods, today’s children are missing out on something essential. The success of ‘‘The Dangerous Book for Boys’’ — which has been on the best-seller list for the last nine months — and its step-by-step instructions for activities like folding paper airplanes is testament to the generalized longing for play’s good old days. So were the questions after Stuart Brown’s library talk; one woman asked how her children will learn trust, empathy and social skills when their most frequent playing is done online. Brown told her that while video games do have some play value, a true sense of ‘‘interpersonal nuance’’ can be achieved only by a child who is engaging all five senses by playing in the three-dimensional world. This is part of a larger conversation Americans are having about play. Parents bobble between a nostalgia-infused yearning for their children to play and fear that time spent playing is time lost to more practical pursuits. Alarming headlines about U.S. students falling behind other countries in science and math, combined with the ever-more-intense competition to get kids into college, make parents rush to sign up their children for piano lessons and test-prep courses instead of just leaving them to improvise on their own; playtime versus résumé building. Discussions about play force us to reckon with our underlying ideas about childhood, sex differences, creativity and success. Do boys play differently than girls? Are children being damaged by staring at computer screens and video games? Are they missing something when fantasy play is populated with characters from Hollywood’s imagination and not their own? Most of these issues are too vast to be addressed by a single field of study (let alone a magazine article). But the growing science of play does have much to add to the conversation. Armed with research grounded in evolutionary biology and experimental neuroscience, some scientists have shown themselves eager — at times perhaps a little too eager — to promote a scientific argument for play. They have spent the past few decades learning how and why play evolved in animals, generating insights that can inform our understanding of its evolution in humans too. They are studying, from an evolutionary perspective, to what extent play is a luxury that can be dispensed with when there are too many other competing claims on the growing brain, and to what extent it is central to how that brain grows in the first place. Scientists who study play, in animals and humans alike, are developing a consensus view that play is something more than a way for restless kids to work off steam; more than a way for chubby kids to burn off calories; more than a frivolous luxury. Play, in their view, is a central part of neurological growth and development — one important way that children build complex, skilled, responsive, socially adept and cognitively flexible brains. Their work still leaves some questions unanswered, including questions about play’s darker, more ambiguous side: is there really an evolutionary or developmental need for dangerous games, say, or for the meanness and hurt feelings that seem to attend so much child’s play? Answering these and other questions could help us understand what might be lost if children play less. ‘‘See how that little boy reaches for a pail?’’ Stuart Brown asked one morning last fall, standing with me on the fringes of a small playground just north of the Central Park Zoo. ‘‘See how he curves his whole body around it?’’ Brown had flown to New York from his home in California to pitch a book about play to publishers. (He sold the idea to an editor at Penguin.) He agreed to meet me at the zoo while he was in town, to help me observe playfulness in the young members of many animal species, including our own. Social play has its own vocabulary. Dogs have a particular body posture called the ‘‘play bow’’ — forelegs extended, rump in the air — that they use as both invitation and punctuation. A dog will perform a play bow at the beginning of a bout, and he will crouch back into it if he accidentally nips too hard and wants to assure the other dog: ‘‘Don’t worry! Still playing!’’ Other species have play signals, too. Chimps put on a ‘‘play face,’’ an open-mouthed expression that is almost like a face of aggression except that the muscles are relaxed into something like a smile. Baboons bend over and peer between their legs as an invitation to play, beavers roll around, goats gambol in a characteristic ‘‘play gait.’’ In fact, most species have from 10 to 100 distinct play signals that they use to solicit play or to reassure one another during play-fighting that it’s still all just in fun. In humans, the analogue to the chimp’s play face is a child’s smile, an open expression that indicates there is no real anger involved even in gestures that can look like a fight. The day Brown met me in the park was a cold one, and the kids were bundled up like Michelin Men, adding more than the usual heft and waddle to their frolicking. Even beneath the padding, though, Brown could detect some typical gestures that these 2- and 3-year-olds were using instinctively to let one another know they were playing. ‘‘Play movement is curvilinear,’’ he said. ‘‘If that boy was reaching for something in a nonplay situation, his body would be all straight lines. But using the body language of play, he curves and embraces.’’ In their play — climbing up a slide, running around, passing buckets back and forth — the kids we watched were engaging in a pattern of behavior that many scientists believe is hard-wired. Their mothers and nannies were watching, too, no doubt having dragged the kids out of comfortable Upper East Side apartments because they thought daily play was important somehow, perhaps the first step in the long march toward Yale. To me all that little-kid motion looked just a bit silly — because play is, in many ways, a silly thing. Indeed, an essential component of play is its frivolity; biologists generally use phrases like ‘‘apparently purposeless activity’’ in their definitions of play. The definition proposed by Gordon Burghardt, an evolutionary psychologist at the University of Tennessee, refines that phrase a little. In his 2005 book, ‘‘The Genesis of Animal Play,’’ he wrote that play is an activity of ‘‘limited immediate function.’’ Burghardt included several other factors in his definition too. Play is an activity that is different from the nonplay version of that activity (in terms of form, sequence or the stage of life in which it occurs), is something the animal engages in voluntarily and repeatedly and occurs in a setting in which the animal is ‘‘adequately fed, healthy and free from stress.’’ That last part of the definition — that play requires that an animal be stress-free and secure — suggests that play is the biological equivalent of a luxury item, the first thing to go when an animal or child is hungry or sick. This makes evolutionary scientists prick up their ears. How can a behavior be crucial and expendable at the same time? And play is indeed expendable. Studies of vervet monkeys found that playtime decreased to almost zero during periods of drought in East Africa. Squirrel monkeys won’t play when their favorite food sources are unavailable. In humans under stress, what happens with play is more complicated. Even under devastating circumstances, the drive to play is unquenchable. As George Eisen wrote in ‘‘Children and Play in the Holocaust’’: ‘‘Children’s yearning for play naturally burst forth even amidst the horror. . . . An instinctual, an almost atavistic impulse embedded in the human consciousness.’’ Yet play does diminish when children suffer long-term, chronic deprivation, either one at a time in abusive or neglectful homes, or on a massive scale in times of famine, war or forced relocation. And children can still survive, albeit imperfectly, without it. For humans and animals alike, truly vigorous, wholehearted, spontaneous play is something of a biological frill. This suggests one possible evolutionary function: that in its playfulness, an animal displays its own abundant health and suitability for breeding. But a skeptic might see it differently: if a behavior is this easy to dispense with when times are hard, it might suggest that the behavior is less essential than some advocates claim. If play is an extravagance, why has it persisted? It must have some adaptive function, or at least a benefit that outweighs its cost, or it would have been winnowed out by the forces of natural selection. One answer can be found through ethology, the study of animal behavior, which takes as one of its goals the explication of how and why a behavior evolved. Nonhuman animals can be more easily studied than humans can: the conditions under which they are raised can be manipulated, their brains altered and probed. And if there is an evolutionary explanation for a human behavior, it could reveal itself in the study of the analogous behavior in animals. Because of nature’s basic parsimony, many aspects of the brain and behavior have been conserved through evolution, meaning that many of the observations that ethologists make in rats, mice and monkeys could apply to humans too. When it comes to animal play, scientists basically agree that it’s mostly mammals that do it, and they basically agree that it’s a mystery why they do it, since there are so many good reasons not to. It all seems incredibly wasteful, and nature does not usually tolerate waste. Play can be costly in terms of energy expenditure. Juveniles spend an estimated 2 to 15 percent of their daily calorie budget on play, using up calories the young animal could more profitably use for growing. Frisky playing can also be dangerous, making animals conspicuous and inattentive, more vulnerable to predators and more likely to hurt themselves as they romp and cavort. Biologists have observed many play-related calamities, like bighorn lambs being injured on cactus plants as they frolicked. One of the starkest measures of the risk of play was made by Robert Harcourt, a zoologist now at Macquarie University in Sydney, Australia, who spent nine months in 1988 observing seal pups off the coast of Peru. Harcourt witnessed 102 seal pups attacked by southern sea lions; 26 of them were killed. ‘‘Of these observed kills,’’ Harcourt reported in the British journal Animal Behaviour, ‘‘22 of the pups were playing in the shallow tidal pools immediately before the attack and appeared to be oblivious to the other animals fleeing nearby.’’ In other words, nearly 85 percent of the pups that were killed had been playing. So play can be risky. And, under stress, it tends to disappear. What then would justify, in evolutionary terms, the prevalence of play? One popular view is the play-as-preparation hypothesis. In this perspective, play evolved because it is good preparation for adulthood. It is a chance for young animals to learn and rehearse the skills they will need for the rest of their lives, and to do so in a secure environment, where mistakes will have few consequences. Proponents of this hypothesis say play is a way — and, not incidentally, a pleasurable way — of getting into muscle memory the generalized movements of survival: chasing, running, probing, tussling. Through play, these movements can be learned when the stakes are low and then retrieved in adulthood, when the setting is less safe and the need more urgent. The play-as-preparation hypothesis seems logical, and each new observation seems to confirm it. Watch wolf pups at play, and it is easy to see how the biting and wrangling could be baby versions of the actions the pups will need later to assert their dominance or to help the pack kill its prey. Watch 2-year-olds playing at a toy workbench with little wooden mallets and blocks, and you can picture them as adults employing those same muscles to wield a full-size hammer. But one trouble with the hypothesis is that the gestures of play, while similar, are not literally the same as the gestures of real life. In fact, the way an animal plays is often the exact opposite of the way it lives. In play-fighting, if one player starts to edge toward victory, he will suddenly reverse roles and move from the dominant to the submissive posture. Or he will stop fighting as hard, something the ethologists call self-handicapping. This is rarely done in real fighting, when the whole point is winning. The targets of play are different, too. In rats, real fighters try to bite one another on the back and the lower flanks; in play fights, they go for the nape of the neck. The gestures players use to nuzzle the neck are not the same ones they need to rehearse if they are to win a serious fight. Nor is there much experimental evidence to support a connection between youthful playing and adult expertise. One Scottish study of kittens, for instance, tested the hypothesis that ample object play early in life would lead to better hunting later on. The investigator, a psychologist named T. M. Caro then at the University of St. Andrews, found no difference in hunting skills between one group of 11 cats that had been exposed to toys in their youth and a control group of 8 cats that had not. Now an alternative view is taking hold, based on a belief that there must be something else going on — play not as a literal rehearsal, but as something less direct and ultimately more important. It focuses on the way that play might contribute to the growth and development of the brain. John Byers started thinking about the brain and play almost by accident. A zoologist at the University of Idaho, Byers had spent years studying the playful antics of deer, pronghorn antelopes and the wild mountain goats called ibex. He knew that play was risky — he had observed ibex kids falling off steep cliffs as they romped — and at first he thought maybe the animals were taking such risks because the motor training helped them get in physical shape for adulthood. But something about this idea troubled him. Play can be exercise, he reasoned, but it was of too short duration to lead to long-term fitness or build muscle tone. Byers preferred an alternate theory. In almost every species studied, a graph of playfulness looked like an inverted U, increasing during the juvenile period and then falling off around puberty, after which time most animals don’t play much anymore. One winter afternoon in 1993, Byers was roaming the stacks at the University of Idaho library, flipping through books the way you do when you’re not quite sure what you’re looking for. One book contained a graph of the growth curve of one important region of the brain, the cerebellum, over the juvenile period in the mouse. The growth curve of the mouse cerebellum was nearly identical to the curve of mouse playfulness. ‘‘It was like a light went on in my head,’’ Byers told me from Washington, D.C., where he is temporarily working at the National Science Foundation. ‘‘I wasn’t thinking specifically about play, but I sort of had a long-term interest in behavioral development.’’ And there it was: a chart that made it look as if rates of play in mice synchronized almost perfectly with growth rates in one critical region of the brain, the area that coordinates movements originating in other parts of the brain. Intrigued, Byers enlisted the help of a graduate student, Curt Walker, who looked through the scientific literature on cerebellum development in rats and cats. ‘‘Then we compared those rates to what was known about the rates of play in those species,’’ Byers said. ‘‘And rats and cats showed the same relationship as mice: a match between when they were playing and when the cerebellum was growing.’’ The synchrony suggested a few things to Byers: that play might be related to growth of the cerebellum, since they both peak at about the same time; that there is a sensitive period in brain growth, during which time it’s important for an animal to get the brain-growth stimulation of play; and that the cerebellum needs the whole-body movements of play to achieve its ultimate configuration. This opened up new lines of research, as neuroscientists tried to pinpoint just where in the brain play had its most prominent effects — which gets to the heart of the question of what might be lost when children do not get enough play. Most of this work has been done in rats. Sergio Pellis, a neuroscientist at the University of Lethbridge in Alberta, Canada, is one of these investigators. He studies how brain damage in rats affects play behavior, and whether the relationship works in reverse: that is, not only whether brain-damaged rats play abnormally but also whether play-deprived rats develop abnormalities in their brains. Pellis’s research indicates that the relationship might indeed work in both directions. In a set of experiments conducted last year, Pellis and his colleagues raised 12 female rats from the time they were weaned until puberty under one of two conditions. In the control group, each rat was caged with three other female juveniles. In the experimental group, each rat was caged with three female adults. Pellis knew from previous studies that the rats caged with adults would not play, since adult rats rarely play with juveniles, even their own offspring. They would get all the other normal social experiences the control rats had — grooming, nuzzling, touching, sniffing — but they would not get play. His hypothesis was that the brains in the experimental rats would reflect their play-deprived youth, especially in the region known as the prefrontal cortex. At puberty the rats were euthanized so the scientists could look at their brains. What Pellis and his collaborators found was the first direct evidence of a neurological effect of play deprivation. In the experimental group — the rats raised in a play-deprived environment — they found a more immature pattern of neuronal connections in the medial prefrontal cortex. (This is distant from the cerebellum; it is part of the cerebrum, which constitutes the bulk of the mammalian brain.) Rats, like other mammals, are born with an overabundance of cortical brain cells; as the animal matures, feedback from the environment leads to the pruning and selective elimination of these excess cells, branchings and connections. Play is thought to be one of the environmental influences that help in the pruning — and, this research showed, play deprivation interferes with it. Figuring out what these findings mean in terms of function involves a certain amount of conjecture. Pellis interprets his observation of a more tangled, immature medial prefrontal cortex in play-deprived rats to mean that the rat will be less able to make subtle adjustments to the social world. But maybe the necessary pruning can happen later in life, through other feedback mechanisms having little to do with play. Maybe there were already compensatory changes happening elsewhere in the brains of these young rats where no one had thought to look. Current research in Pellis’s lab, in which the brain is damaged first and the rat’s playing ability is measured afterward, seems to confirm that the medial prefrontal cortex has an important role in play. But the exact nature of its action is still not clear. |
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