Free Exuberance: The Passion for Life by Kay Redfield Jamison Page B

the immune system and increasing resilience under stress.
    Panksepp believes thatplay probably increases gene expression in the frontal lobe for a protein involved in brain development. Experimenters have also shown that mice raised in cages filled with tunnels and toys play more, explore more, and ultimately generate more new neurons than mice raised in standard cages. Extensive psychological research in humans, to which we shall return, shows a highly beneficial effect of positive mood on learning and flexibility in thinking, in addition to its significant influence on social behavior. Play is the headwater of this elated, shaping mood.
    We tend, as a thinking species, to emphasize the beholdenness of our emotions to our thoughts, rather than to trace our thinking to the ancient powers of our emotions. Yet our emotions were laiddown far earlier than language or imaginative thought, sculpted by the realities of survival that we share with all other animals: to explore and to know our territories, to stay out of the grasp of our predators, to scavenge food and mate, and to set up safe havens. Each requires the complex yoking of swift and intense emotion to physical agility and, increasingly, with the evolution of higher animals, to mental acumen. Survival depends on comprehending the elements of the environment and then acting effectively upon that comprehension.Trout raised in hatcheries, for example, have smaller brains than trout born in the wild, who must learn to recognize and evade predators and to spot, chase, and capture prey. Charles Darwin had observed this more than a century earlier. “I have shewn,” he wrote in
The Descent of Man
, “thatthe brains of domestic rabbits are considerably reduced in bulk, in comparison with those of the wild rabbit or hare; and this may be attributed to their having been closely confined during many generations, so that they have exerted their intellect, instincts, senses, and voluntary movements but little.” To explore further is to learn more, and to learn more is to acquire the means of dealing with an unpredictable and changing world. Play promotes and encourages this.
    Play helps the animal acquire knowledge about both the potential and the dangers of its world; it sets and becomes the physical arena for exploring new objects and for combining physical activities with sensory experiences in ways that might otherwise remain untried. Play increases the scope of the animal’s experience and the range of its skills, generates a greater sense of control, and allows the animal to test its competence. Jane Goodall has emphasized the central role of play in making young chimpanzees familiar with their environment. The young ape, she writes, “learns during play which type of branch is safe to jump onto and which will break, and he practices gymnastic skills, such as leaping down from one branch and catching another far below, which when he is older willserve him in good stead—during an aggressive encounter with a higher-ranking individual in the treetops, for instance.” The young chimps, in short, learn to go out on a limb.
    Behavior that expends such energy, that is potentially dangerous yet intensely reinforcing, and that is nearly universal in the more cognitively complex animals must be of consequence. Play is unscripted. In being so, it introduces and rewards flexibility, prepares the animal for the unpredictable, and makes enjoyable the animal’s testing of the boundaries of what it knows and what it has yet to know. Play is about learning how to learn. It is a kind of controlled adventure, an exploration of both new and familiar worlds. Play and curiosity are inevitably linked.
    “Inasmuch as new objects may always be advantageous,” wrote William James, “it is better that an animal should not
absolutely
fear them.” It is important to explore new objects, he went on, and to ascertain “what they may be likely to bring forth.” In that light, James suggested,