Proceedings of the Annual Meeting of the Cognitive Science Society

Play is a universal behavior widely held to be critical for learning and development. Recent studies suggest children’sexploratory play is consistent with formal accounts of learning. This ”play as rational exploration” view suggests thatchildren’s play is sensitive to costs, rewards, and expected information gain. By contrast, here we suggest that a definingfeature of human play is that children subvert normal utility functions in play, setting up problems where they incurneedless costs to achieve arbitrary rewards. Across three studies, we show that 4-5-year-old children not only infer playfulbehavior from observed violations of rational action (Experiment 1), but themselves take on unnecessary costs and performinefficient actions during play, despite acting efficiently in non-playful, instrumental contexts (Experiments 2-3). We endby discussing the value of apparently utility-violating behavior and why it might serve learning in the long run.