@inproceedings{yu-etal-2026-smart,
title = "{SMART}: Sink-based Modality-Aware Redistribution of Transformer Attention",
author = "Yu, Dian and
Yao, Yao and
Zhao, Hai",
editor = "Lee, Hung-Yi and
Dev, Sunipa and
Li, Jessy and
Elliott, Desmond",
booktitle = "Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.emnlp-main.2358/",
pages = "53547--53560",
ISBN = "979-8-89176-459-0",
abstract = "Multimodal Large Language Models (MLLMs) often exhibit modality bias, where predictions over-rely on one modality while underutilizing others. However, the mechanism underlying modality bias remains poorly understood. In this work, we first introduce Banana-Counting, a controlled diagnostic dataset for measuring modality preference under cross-modal conflicts. Evaluations across diverse MLLMs reveal pervasive modality imbalance. Then, through attention analysis, we show that modality bias is strongly associated with imbalanced cross-modal attention allocation and modality-specific attention sinks that absorb redundant attention mass. Motivated by these findings, we propose SMART, an inference-time method that mitigates modality bias by redistributing redundant sink attention toward under-attended modalities. SMART consistently improves multimodal balance across model families. On Banana-Counting, it reduces the modality gap from 27.73 to 0.66 on LLaVA-v1.5-7B while improving balanced multimodal accuracy. Moreover, SMART generalizes effectively to downstream multimodal reasoning tasks without retraining or parameter updates."
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<abstract>Multimodal Large Language Models (MLLMs) often exhibit modality bias, where predictions over-rely on one modality while underutilizing others. However, the mechanism underlying modality bias remains poorly understood. In this work, we first introduce Banana-Counting, a controlled diagnostic dataset for measuring modality preference under cross-modal conflicts. Evaluations across diverse MLLMs reveal pervasive modality imbalance. Then, through attention analysis, we show that modality bias is strongly associated with imbalanced cross-modal attention allocation and modality-specific attention sinks that absorb redundant attention mass. Motivated by these findings, we propose SMART, an inference-time method that mitigates modality bias by redistributing redundant sink attention toward under-attended modalities. SMART consistently improves multimodal balance across model families. On Banana-Counting, it reduces the modality gap from 27.73 to 0.66 on LLaVA-v1.5-7B while improving balanced multimodal accuracy. Moreover, SMART generalizes effectively to downstream multimodal reasoning tasks without retraining or parameter updates.</abstract>
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%0 Conference Proceedings
%T SMART: Sink-based Modality-Aware Redistribution of Transformer Attention
%A Yu, Dian
%A Yao, Yao
%A Zhao, Hai
%Y Lee, Hung-Yi
%Y Dev, Sunipa
%Y Li, Jessy
%Y Elliott, Desmond
%S Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-459-0
%F yu-etal-2026-smart
%X Multimodal Large Language Models (MLLMs) often exhibit modality bias, where predictions over-rely on one modality while underutilizing others. However, the mechanism underlying modality bias remains poorly understood. In this work, we first introduce Banana-Counting, a controlled diagnostic dataset for measuring modality preference under cross-modal conflicts. Evaluations across diverse MLLMs reveal pervasive modality imbalance. Then, through attention analysis, we show that modality bias is strongly associated with imbalanced cross-modal attention allocation and modality-specific attention sinks that absorb redundant attention mass. Motivated by these findings, we propose SMART, an inference-time method that mitigates modality bias by redistributing redundant sink attention toward under-attended modalities. SMART consistently improves multimodal balance across model families. On Banana-Counting, it reduces the modality gap from 27.73 to 0.66 on LLaVA-v1.5-7B while improving balanced multimodal accuracy. Moreover, SMART generalizes effectively to downstream multimodal reasoning tasks without retraining or parameter updates.
%U https://aclanthology.org/2026.emnlp-main.2358/
%P 53547-53560
Markdown (Informal)
[SMART: Sink-based Modality-Aware Redistribution of Transformer Attention](https://aclanthology.org/2026.emnlp-main.2358/) (Yu et al., EMNLP 2026)
ACL