Causal Intervention with LMMs: Generative Text Facilitates Fine-Grained Pedestrian Anomaly Behavior Retrieval

Weifeng Xu, Shaofei Huang, Yaxiong Wang, Zhedong Zheng


Abstract
Pedestrian anomaly behavior retrieval requires disambiguating subtle anomalous actions from routine ones using natural language. Existing cross-modal alignment methods often struggle with confounding biases: visual entanglement (dominant environments overshadowing target actions) and textual biases (limited stylistic diversity). These spurious correlations lead to erroneous matches among visually similar but semantically distinct samples. To address this, we reformulate the task from a causal intervention perspective. We propose a dual generative framework leveraging Large Multimodal Models (LMMs) to break environment-action and style-text confounders. Specifically, we synthesize causally meaningful hard negatives to decouple actions from environments, and augment positive queries with stylistically diverse rephrasings to eliminate narrative dependency. Extensive experiments on the Pedestrian Anomaly Behavior (PAB) benchmark yield consistent improvements of +1.71% in Recall@1 and +1.01% in mAP. Furthermore, zero-shot evaluation on the out-of-distribution UCC dataset demonstrates markedly enhanced generalization, achieving +3.23% and +2.46% gains in Recall@1 and mAP, respectively.
Anthology ID:
2026.findings-emnlp.225
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
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Pages:
4723–4738
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.225/
DOI:
Bibkey:
Cite (ACL):
Weifeng Xu, Shaofei Huang, Yaxiong Wang, and Zhedong Zheng. 2026. Causal Intervention with LMMs: Generative Text Facilitates Fine-Grained Pedestrian Anomaly Behavior Retrieval. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 4723–4738, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Causal Intervention with LMMs: Generative Text Facilitates Fine-Grained Pedestrian Anomaly Behavior Retrieval (Xu et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.225.pdf