Rats

When times get tough, many people turn serious - this is no time for girls'

giggly nights out or to go paintballing with the guys. Or is it? Some researchers believe that horsing around may be better in the long run than hunkering down. Play, they say, not only frees up your mind, it keeps you nimble for when the unexpected happens. "It's a survival drive that we have minimised in our culture," says Stuart Brown, a psychiatrist who founded the US National Institute for Play in Carmel Valley, California.

People are wrong to regard play as just a frill, says Marc Bekoff at the University of Colorado at Boulder. He studies play behaviour in social carnivores such as wolves, coyotes and dogs, and believes that it allows individuals to try out new things because they can make mistakes without penalty. "Play encourages taking reasonable risks," he says. "It allows you to be flexible and creative." Brown agrees. "The search for novelty and the desire for something fresh is a hallmark of the state of play." And of course novelty and freshness are also central to creativity.

Brown sees play as a special biological state, like sleep. It seems to be important throughout the human life cycle, but particularly so in childhood.

In this respect we are like other social species. Sergio Pellis at the University of Lethbridge in Alberta, Canada, put juvenile rats in cages that allowed them to sniff, groom and interact with others, but not to engage in rough-and-tumble play. These animals grew up unable to adapt to novel situations, says Pellis. Brown's studies of adults who were deprived of play in childhood reveal similar damaging effects.

At the very least, then, we should equip the next generation for the inevitable recessions of the future by encouraging water fights and inviting imaginary friends to join in.