VITAL: Visual-Semantic Dual Supervision for Enhanced and Interpretable Latent Reasoning in Medical MLLMs

Qiaoru Li, Shaotian Liang, Jintao Chen, Haoran Sun, Yuxiang Cai, Jianwei Yin, Yankai Jiang


Abstract
Latent reasoning enables reasoning over continuous hidden states rather than explicit tokens, avoiding the language bottleneck and inference overhead of chain-of-thought for medical VQA. However, existing methods suffer from modality collapse, insufficient visual supervision, and train-inference mismatch. Moreover, their opaque latent states offer no interpretability, which is critical in clinical applications. We propose VITAL, a latent-space reasoning framework for medical MLLMs with visual-semantic dual supervision: an auxiliary text decoder reconstructs reasoning chains from latent states, while a visual projector regresses ROI features from a frozen, independent medical vision encoder. Both modules are discarded at inference with zero overhead, yet can be re-attached post-hoc for dual interpretability, providing textual and visual explanations of the reasoning process without sacrificing efficiency. We construct a 61K dataset spanning 9 imaging modalities, exceeding prior medical visual latent reasoning datasets by an order of magnitude. Experiments on 7 benchmarks show that VITAL consistently and substantially outperforms the backbone, all latent reasoning baselines, and medical MLLMs trained on far larger data, achieving state-of-the-art results competitive with trillion-parameter proprietary models.
Anthology ID:
2026.emnlp-main.97
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
2267–2294
Language:
URL:
https://aclanthology.org/2026.emnlp-main.97/
DOI:
Bibkey:
Cite (ACL):
Qiaoru Li, Shaotian Liang, Jintao Chen, Haoran Sun, Yuxiang Cai, Jianwei Yin, and Yankai Jiang. 2026. VITAL: Visual-Semantic Dual Supervision for Enhanced and Interpretable Latent Reasoning in Medical MLLMs. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 2267–2294, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
VITAL: Visual-Semantic Dual Supervision for Enhanced and Interpretable Latent Reasoning in Medical MLLMs (Li et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.97.pdf