From Vision to Language: Investigating Causal Information Flow in Multimodal Decision-Making

Davide Testa, Hugh Mee Wong, Alessandro Lenci, Bernardo Magnini, Albert Gatt


Abstract
Vision-Language Models are commonly evaluated through their final predictions, but understanding whether these decisions are grounded in visual evidence requires tracing how visual information contributes to language-based decisions. With this purpose in mind, we investigate cross-modal information flow in a video-based generative multiple-choice-like setting by applying a layer-wise causal intervention on video-text attention pathways. We target spatial, causal, and temporal visual reasoning. Our results show that visual information is mainly integrated while the model processes the candidate answer options, which serve as the primary textual grounding sites for the final decision. We further show that nouns play an important role as semantic anchors during multimodal enrichment, while verbs are more relevant when temporal relations are processed. Finally, we identify a distinct pattern in temporal reasoning, suggesting that VLMs struggle to reconstruct sequential information across video frames, but we remark that such fragility may also reflect linguistic biases associated with specific temporal expressions used for defining the relation between events within a scene.
Anthology ID:
2026.findings-emnlp.1887
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:
40231–40247
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1887/
DOI:
Bibkey:
Cite (ACL):
Davide Testa, Hugh Mee Wong, Alessandro Lenci, Bernardo Magnini, and Albert Gatt. 2026. From Vision to Language: Investigating Causal Information Flow in Multimodal Decision-Making. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 40231–40247, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
From Vision to Language: Investigating Causal Information Flow in Multimodal Decision-Making (Testa et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1887.pdf