Why people play: artificial lives acquiring play-instinct to stabilize productivity

We propose a model to generate a group of artificial lives capable of coping with various environment which is a set of tasks, and show play or hobbies are necessary for the group of individuals to maintain the ability to cope with various changes of the environment as a whole. This may be an another aspect of the wide variety of essential group capabilities. If the variety in a species decreases it will become extinct. We show some simulation results: in a world where a greater variety of abilities are demanded in play the performance of the whole world calculated only from job tasks becomes steady and avoids the risk of extinction of the species. This is the effect of play.