Anom3W: A Unified Benchmark for Video Anomaly Grounding and Understanding

Liang Liang, Yun Zhu, Juekai Lin, Haoyang Wang, Jinhui Li, Weilin Zhou, Yuehan Zhu, Lijun Wu, Wenqiao Zhang, Jun Xiao


Abstract
Understanding anomalies in real-world videos requires reasoning about when events occur, where they happen, and what actions unfold. Existing benchmarks, however, largely ignore one or more of these dimensions, making it difficult to evaluate whether multimodal large models (MLLMs) truly understand abnormal events beyond simple detection. To address this gap, we introduce Anom3W, a benchmark designed to evaluate MLLMs across temporal, spatial, and semantic dimensions. Our semi-automatic pipeline consolidates heterogeneous anomaly resources into verified spatio-temporal annotations, enabling rigorous, reasoning-oriented evaluation. By treating spatial boxes and tubes as evidence cues, Anom3W challenges models to reason about entities, locations, and behaviors, rather than merely flag anomalies. Experiments demonstrate that even state-of-the-art MLLMs struggle, highlighting the critical importance of spatial grounding and semantic understanding. Anom3W establishes a new standard for interpretable, context-aware video anomaly reasoning.
Anthology ID:
2026.findings-emnlp.1973
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
42074–42092
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1973/
DOI:
Bibkey:
Cite (ACL):
Liang Liang, Yun Zhu, Juekai Lin, Haoyang Wang, Jinhui Li, Weilin Zhou, Yuehan Zhu, Lijun Wu, Wenqiao Zhang, and Jun Xiao. 2026. Anom3W: A Unified Benchmark for Video Anomaly Grounding and Understanding. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 42074–42092, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Anom3W: A Unified Benchmark for Video Anomaly Grounding and Understanding (Liang et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1973.pdf