Video-HOCA: A Diagnostic Benchmark for Physical Anomaly Reasoning in Video-LLMs

We introduce Video-HOCA, a diagnostic benchmark for physical anomaly reasoning in videos. Video-HOCA uses an Ontological-Causal taxonomy to distinguish violations of an entity's own properties or capabilities from violations of physical relations among entities and the environment. It contains more than 1,400 generated and real-world videos and 3,470 question-answer pairs, with human verification of labels and reference answers. The benchmark evaluates four levels of reasoning: plausibility checking, anomaly attribution, fine-grained recognition, and open-ended physical explanation. Across 20 Instruct-mode Video-LLMs, we find that recognition outpaces explanation: Task I scores cluster at 75-88, while Task II macro-F1 stays mostly below 50. We also find that the Ontological-Causal gap depends on the task and model configuration, and that Thinking-mode gains are not explained by sampling or output budget alone. Annotation agreement, Task-IV human-judge and judge-judge checks, alternative metrics, and temporal/decoding controls validate the evaluation pipeline and bound the claims supported by the benchmark.