The Concept of Play:

"Much of animal and human behaviour involves trade-offs between conflicting requirements. In making those trade-offs, the individual may be trapped on the metaphorical equivalent of a false mountain summit what engineers call a local optimum with a higher peak beyond. When that happens, the individual needs a way of getting off the lower peak in order to discover the most satisfactory solution the global optimum. We shall argue that play is an evolved biological adaptation that enables the individual to escape from local optima and discover better solutions."

Play, Playfulness, Creativity and Innovation
Bateson & Martin