Title: Probing the Limits of Embodied Spatial Planning in LLMs
Primary area: datasets and benchmarks
Keywords: LLM-based planning

Abstract: Can the symbolic reasoning of Large Language Models (LLMs) extend to the physical world, or do they lack a fundamental "mind's eye" for grounded physical reasoning? This paper investigates this question by probing the ability of LLMs to reason about a dynamic physically-grounded environment. We introduce a novel methodology centered on indoor bouldering, a task that demands spatial imagination to (1) construct a mental environment from coordinates, (2) simulate an embodied agent's movement within that environment, and (3) adhere to physical constraints from the agent. Using our purpose-built dataset, EmbodiedPlan, which incorporates multiple agent profiles to test embodied reasoning, we challenge state-of-the-art LLMs (e.g., GPT-4o, Gemini Pro) to generate plans for different embodied agents. Our experiments reveal a consistent gap between syntactic fluency and physical plausibility: models can generate plans that are syntactically correct yet physically naive and poorly adapted to the agent's body. The results suggest that current LLMs possess a "brittle" mind's eye, capable of manipulating spatial symbols but lacking the grounded imagination required for true physical reasoning.