From Saliency Ranking to Evidence Preservation: Visual Token Condensation for Efficient Multimodal Reasoning

Xin Zou, Di Lu, Yibo Yan, Shuliang Liu, Yizhou Wang, Xiang Liu, Linfeng Zhang, Xuming Hu


Abstract
Visual tokens dominate the inference cost of multimodal large language models (MLLMs), but aggressive token reduction often degrades reasoning. We argue that the fragility comes from a saliency-ranking view, i.e., existing training-free methods typically rank tokens by a scalar proxy, such as cross-attention, [CLS] attention, or feature similarity, and then prune or merge tokens independently. However, visual evidence is set-valued and structured: salient patches can be redundant, low-saliency tokens can be answer-critical, and feature-similar patches can be unsafe to merge when they are spatially incompatible. We propose CondenseVLM, a simple framework that formulates visual token compression as a budgeted evidence-preservation question. The formulation jointly optimizes salient evidence coverage, contextual coverage, and spatially constrained merge fidelity. It yields a monotone submodular coverage term, a marginal-gain interpretation of diversity-aware anchor selection, and a local distortion bound for spatial-semantic merging. Comprehensive experiments across six MLLM families and diverse general-purpose, grounding, text-dense, and video benchmarks demonstrate that improves the accuracy-efficiency trade-off, and achieves the SOTA performance.
Anthology ID:
2026.emnlp-main.771
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
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Pages:
17908–17935
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URL:
https://aclanthology.org/2026.emnlp-main.771/
DOI:
Bibkey:
Cite (ACL):
Xin Zou, Di Lu, Yibo Yan, Shuliang Liu, Yizhou Wang, Xiang Liu, Linfeng Zhang, and Xuming Hu. 2026. From Saliency Ranking to Evidence Preservation: Visual Token Condensation for Efficient Multimodal Reasoning. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 17908–17935, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
From Saliency Ranking to Evidence Preservation: Visual Token Condensation for Efficient Multimodal Reasoning (Zou et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.771.pdf