cs.LGMay 29, 2026

Emergence of Exploration in Policy Gradient Reinforcement Learning via Retrying

Authors: Soichiro NishimoriPaavo ParmasSotetsu KoyamadaTadashi KozunoToshinori KitamuraShin IshiiYutaka Matsuo

Abstract

In reinforcement learning (RL), agents benefit from exploration only because they repeatedly encounter similar states: trying different actions can improve performance or reduce uncertainty; without such retries, a greedy policy is optimal. We formalize this intuition with ReMax, an objective that evaluates a policy by the expected maximum return over MM samples, where MM is a positive integer, while accounting for return uncertainty. Optimizing this objective induces stochastic exploration as an emergent property, without explicit bonus terms. For efficient policy optimization, we derive a new policy-gradient formulation for ReMax and introduce ReMax PPO (RePPO), a PPO variant that optimizes ReMax while generalizing the discrete retry count MM to a continuous parameter m>0m > 0, enabling fine-grained control of exploration. Empirically, RePPO promotes exploration, without any explicit exploration bonuses, on the MinAtar and Craftax benchmarks.

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