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home / papers / 2026 / What's Missing in Vision-Language Models? Probing Their Struggles with Causal Order Reasoning

What's Missing in Vision-Language Models? Probing Their Struggles with Causal Order Reasoning

Paper · 2026 · Zhaotian Weng, Haoxuan Li, Xin Eric Wang et al.

Summary

Vision-language models score well on many benchmarks, but it is unclear whether they understand cause-and-effect relations in images. Existing reasoning datasets mix question types and often let models succeed just by spotting objects or actions. The authors build two diagnostic benchmarks, VQA-Causal and VCR-Causal, derived from "Why" questions in VQA and from VCR. Each image comes with caption pairs that are identical except that cause and effect are swapped. These pairs use 12 different causal conjunctions, some placing the cause first and others placing the effect first. The authors test twelve VLMs, including CLIP, NegCLIP, BLIP, FLAVA, LLaVA and Qwen2.5-VL. Most perform close to chance on causal order, even though a controlled variant shows they recognize objects and activities well. The authors trace this gap to the near absence of explicit causal phrasing in common training corpora. Fine-tuning NegCLIP with hard negatives that invert the causal direction produces CausalCLIP. It improves on both in-domain and out-of-domain tests without hurting retrieval. The work exposes a concrete blind spot and offers both a resource and a data-level remedy.

Key points

  • VQA-Causal has 1,947 instances and VCR-Causal has 3,511. Each image is paired with 12 caption pairs, one per causal conjunction. Data and code are at github.com/limenlp/CausalVLM.
  • Ten of the twelve evaluated models reach at most 52% accuracy, against a 50% random baseline and 98% for humans.
  • Only 0.92% of VQA validation questions and 35.43% of VCR validation questions involve causal reasoning. In a sample of 100 VCR questions, 46% could be solved through object or activity shortcuts.
  • Explicit causal expressions appear in just 0.08% of LAION-400M and 0.01% of MSCOCO instances.
  • CausalCLIP was trained on 4,891 causal instances from the VQA training set using 10 conjunctions. It was evaluated on all 12 conjunctions, with VCR-Causal as a zero-shot test. It keeps downstream performance and outperforms OpenCLIP on MSCOCO and Flickr30k retrieval.

Our summary of the paper, in our own words — not its text. The work belongs to its authors; read it at the links above.

 Institutions

 Fields, topics and concepts

Cite

Cite as Zhaotian Weng, Haoxuan Li, Xin Eric Wang, Kuan-Hao Huang and Jieyu Zhao. 2026. What's Missing in Vision-Language Models? Probing Their Struggles with Causal Order Reasoning. Proceedings of the 19th Conference of the European Chapter of the Association for Computational Linguistics (Volume 1: Long Papers).

The paper itself, not this page. BibTeX from the library's record of the work. DOI 10.18653/v1/2026.eacl-long.266

@inproceedings{weng2026what,
  title = {{What's Missing in Vision-Language Models? Probing Their Struggles with Causal Order Reasoning}},
  author = {Zhaotian Weng, Haoxuan Li, Xin Eric Wang, Kuan-Hao Huang and Jieyu Zhao},
  booktitle = {Proceedings of the 19th Conference of the European Chapter of the Association for Computational Linguistics (Volume 1: Long Papers)},
  year = {2026},
  doi = {10.18653/v1/2026.eacl-long.266},
  url = {https://doi.org/10.18653/v1/2026.eacl-long.266}
}

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