Ex Ante Evaluation of AI-Induced Idea Diversity Collapse
It addresses the overlooked problem of population-level idea crowding from AI for developers and evaluators of creative AI systems, offering an actionable evaluation target.
The paper introduces a framework to evaluate AI-induced diversity collapse in creative outputs, showing that frontier LLMs produce more crowded ideas than humans across three tasks, with a diversity ratio below parity. The framework enables ex ante estimation of crowding risk without human-AI interaction data.
Creative AI systems are typically evaluated at the level of individual utility, yet creative outputs are consumed in populations: an idea loses value when many others produce similar ones. This creates an evaluation blind spot, as AI can improve individual outputs while increasing population-level crowding. We introduce a human-relative framework for benchmarking AI-induced human diversity collapse without requiring human-AI interaction data, providing an ex ante protocol to estimate crowding risk from model-only generations and matched unaided human baselines. By modeling ideas as congestible resources, we show that source-level crowding is identifiable from within-distribution comparisons, yielding an excess-crowding coefficient $Δ$ and a human-relative diversity ratio $ρ$. We show that $ρ\ge1$ is the no-excess-crowding parity condition and connect $Δ$ to an adoption game with exposure-dependent redundancy costs. Across short stories, marketing slogans, and alternative-uses tasks, three frontier LLMs fall below parity across crowding kernels. Estimates stabilize with feasible model-only sample sizes. Importantly, generation-protocol variants show that crowding can be reduced through targeted design, making diversity collapse an actionable, development-time evaluation target for population-aware creative AI.