Rewarding Bad Physics Habits: What VLMs Learn When You Pay Them to Reason
A factory camera sees a pressure gauge. The AI reads the image, explains the mechanism, applies the formula, and recommends an action. Everyone in the meeting relaxes, because the model has produced a neat chain of reasoning. That is usually the moment to become nervous. The dangerous part is not that a vision-language model can be wrong. We know that. The more interesting problem is that a model can become wrong in a very specific way because we trained it to chase the wrong reward. Pay it for clean formatting, and it learns to look organized. Pay it for final answers, and it may sacrifice the reasoning path. Pay it to stare at the image, and it may do better on spatial problems while forgetting that physics also contains formulas. Apparently, “look harder” is not a complete theory of mechanics. ...