Interpretable Meta-Policies for Neural Decision Making

Summary

Deep Reinforcement Learning remains difficult to interpret and align due to the black-box nature of neural networks. While (neuro-)symbolic approaches improve transparency by incorporating symbolic reasoning, applying them directly to low-level actions results in overly complex, unreadable policies. We introduce NEXUS, a hierarchical RL framework that resolves this tension by combining neural skills with symbolic meta-policies. By shifting transparent reasoning to high-level skills rather than atomic actions, NEXUS drastically reduces symbolic complexity without sacrificing environment performance. Object-centric observations enable high-level reasoning and the design of reward functions and meta-policies by interaction with LLMs. We demonstrate that NEXUS agents learn disentangled skills, are interpretable regarding high-level goals, are better aligned to goals described in the game manual, less prone to reward hacking and more robust to game simplifications than deep RL. Finally, we isolate and evaluate the impact of different meta-policy architectures (neural, symbolic, neuro-symbolic) on environmental return and aligned task performance.