Smile when you say that…

I always smile just before I slap someone up side the head, myself… in a nice, curving motion, of course…

Children and Youth – Play – Development – Science – New York Times

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.’’

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For all its variety, however, there is something common to play in all its protean forms: variety itself. The essence of play is that the sequence of actions is fluid and scattered. In the words of Marc Bekoff, an evolutionary biologist at the University of Colorado, play is at its core ‘‘a behavioral kaleidoscope.’’

In fact, it’s this kaleidoscopic quality that led Bekoff and others to think of play as the best way for a young animal to gain a more diverse and responsive behavioral repertory. Thus, the currently fashionable flexibility hypothesis, a revival of an idea Bekoff first proposed in the 1970s. If a single function can be ascribed to every form of play, in every playful species, according to this way of thinking, it is that play contributes to the growth of more supple, more flexible brains.

‘‘I think of play as training for the unexpected,’’ Bekoff says. ‘‘Behavioral flexibility and variability is adaptive; in animals it’s really important to be able to change your behavior in a changing environment.’’ Play, he says, leads to mental suppleness and a broader behavioral vocabulary, which in turn helps the animal achieve success in the ways that matter: group dominance, mate selection, avoiding capture and finding food.

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Why would such an enriching activity as play also be a source of so much anarchy and fear? Sutton- Smith found one possible answer by reading Stephen Jay Gould, the author and evolutionary biologist. The most highly adaptive organisms, Gould wrote, are those that embody both the positive and the negative, organisms that ‘‘possess an opposite set of attributes usually devalued in our culture: sloppiness, broad potential, quirkiness, unpredictability and, above all, massive redundancy.’’ Finely tuned specific adaptations can lead to blind alleys and extinction, he wrote; ‘‘the key is flexibility.’’

What Gould called quirkiness, Sutton-Smith called play. ‘‘Animal play has been described by many investigators as fragmentary, disorderly, unpredictable and exaggerated,’’ Sutton-Smith wrote, and ‘‘child play has been said to be improvised, vertiginous and nonsensical.’’ The adaptive advantage to a behavior that is multifaceted, then, is that pursuing it, enjoying it, needing it to get through the day, allows for a wider range in a play-loving person’s behavioral repertory, which is always handy, just in case.

Playing might serve a different evolutionary function too, he suggests: it helps us face our existential dread. The individual most likely to prevail is the one who believes in possibilities — an optimist, a creative thinker, a person who has a sense of power and control. Imaginative play, even when it involves mucking around in the phantasmagoria, creates such a person. ‘‘The adaptive advantage has often gone to those who ventured upon their possibility with cries of exultant commitment,’’ Sutton-Smith wrote. ‘‘What is adaptive about play, therefore, may be not only the skills that are a part of it but also the willful belief in acting out one’s own capacity for the future.’’