Abstract:Creativity is core to being human. Generative artificial intelligence (GenAI) holds promise for humans to be more creative by offering new ideas, or less creative by anchoring on GenAI ideas. We study the causal impact of GenAI ideas on the production of an unstructured creative output in an online experimental study where some writers could obtain ideas for a story from a GenAI platform. We find that access to GenAI ideas causes stories to be evaluated as more creative, better written and more enjoyable, especially among less creative writers. However, objective measures of story similarity within each condition reveal that GenAI-enabled stories are more similar to each other than stories by humans alone. These results point to an increase in individual creativity, but at the same time there is a risk of losing collective novelty: this dynamic resembles a social dilemma where individual writers are better off using GenAI to improve their own writing, but collectively a narrower scope of novel content may be produced with GenAI. Our results have implications for researchers, policy-makers and practitioners interested in bolstering creativity, but point to potential downstream consequences from over-reliance.