arXiv:2610.14186v1 Announce Type: new Abstract: Could model-free reinforcement learning algorithms actually be learning a model of the environment? In this work, we apply counterfactual interventions which hold everything about a state fixed, besides a targeted change, to explore if the value function of a Proximal Policy Optimization agent forms a world model of the Crafter environment. Despite only being trained to optimize reward, we discover that the value function learns concepts such as the rules governing when a diamond is collectible, water and food having an impact on health, heuristics regarding inventory, and more. Finally, we discuss the safety implications of our visualizations and some shortcomings of current reinforcement learning agents that will prevent us from building truly advanced machine intelligence.
Visualizing the World Model in an Agent's Value Function
A Proximal Policy Optimization agent trained only to optimize reward in the Crafter environment learns a world model inside its value function, according to an arXiv paper (2610.14186v1). Using counterfactual interventions that hold everything about a state fixed except a targeted change, the researchers found the value function encodes concepts including the rules governing when a diamond is collectible, water and food affecting health, and inventory heuristics. The paper also discusses safety implications of the visualizations and shortcomings of current reinforcement learning agents that it says will prevent the building of truly advanced machine intelligence.
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