http://articles.mercola.com/sites/articles/archive/2009/06/11/Go-Out-and-Play.aspx
Play is good for your health. A lot of play involves exercise, which is a good thing in and of itself, but there’s more to it than that. Play relieves stress and releases a whole range of feel-good chemicals in your brain, which not only make play fun but relieves tension across the whole of your body.
Play is good for your brain, too. Play lights up the entire right side of your brain, creating a state of hyper-creativity that literally changes the way you see the world.
Play unites your mind and body. In play, the gap between physical sensation and mental sensation is bridged.
Play creates social bonds. There’s evidence that the earliest social bonds are primarily playful ones. As an infant develops a sense of its own identity and begins to recognize other people as beings with identities of their own, it begins to learn play and socialize at the same time. That doesn’t go away as you get older -- play is still a rock-solid foundation for social behavior.
