Compose and Fuse: Revisiting the Foundational Bottlenecks in Multimodal Reasoning

Fuente: arXiv
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Autori principali: Wang, Yucheng, Hou, Yifan, Javadov, Aydin, Akhtar, Mubashara, Sachan, Mrinmaya
Natura: Preprint
Pubblicazione: 2025
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author Wang, Yucheng
Hou, Yifan
Javadov, Aydin
Akhtar, Mubashara
Sachan, Mrinmaya
author_facet Wang, Yucheng
Hou, Yifan
Javadov, Aydin
Akhtar, Mubashara
Sachan, Mrinmaya
contents Multimodal large language models (MLLMs) promise enhanced reasoning by integrating diverse inputs such as text, vision, and audio. Yet cross-modal reasoning remains underexplored, with conflicting reports on whether added modalities help or harm performance. These inconsistencies stem from a lack of controlled evaluation frameworks and analysis of models' internals to isolate when and why modality interactions support or undermine reasoning. We address this gap through a logic-grounded evaluation framework that categorizes multimodal reasoning into six interaction patterns, varying how facts are distributed across modalities and logically combined. Empirically, additional modalities enhance reasoning only when they provide independent and sufficient reasoning paths, while redundant or chained entailment support often hurts performance. Moreover, reasoning degrades in three systematic ways: weaker modalities drag down overall performance, conflicts bias preference toward certain modalities, and joint signals from different modalities fail to be integrated effectively. Therefore, we identify two core failures: task-composition bottleneck, where recognition and reasoning cannot be jointly executed in one pass, and fusion bottleneck, where early integration introduces bias. For further investigation, we find that attention patterns fail to encode fact usefulness, but a simple two-step prompting (recognize then reason) restores performance, confirming the task-composition bottleneck. Moreover, modality identity remains recoverable in early layers, and softening attention in early fusion improves reasoning, highlighting biased fusion as another failure mode. Overall, our findings show that integration, not perception, is the main barrier to multimodal reasoning, suggesting composition-aware training and early fusion control as promising directions.
format Preprint
id arxiv_https___arxiv_org_abs_2509_23744
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Compose and Fuse: Revisiting the Foundational Bottlenecks in Multimodal Reasoning
Wang, Yucheng
Hou, Yifan
Javadov, Aydin
Akhtar, Mubashara
Sachan, Mrinmaya
Computation and Language
Artificial Intelligence
Multimodal large language models (MLLMs) promise enhanced reasoning by integrating diverse inputs such as text, vision, and audio. Yet cross-modal reasoning remains underexplored, with conflicting reports on whether added modalities help or harm performance. These inconsistencies stem from a lack of controlled evaluation frameworks and analysis of models' internals to isolate when and why modality interactions support or undermine reasoning. We address this gap through a logic-grounded evaluation framework that categorizes multimodal reasoning into six interaction patterns, varying how facts are distributed across modalities and logically combined. Empirically, additional modalities enhance reasoning only when they provide independent and sufficient reasoning paths, while redundant or chained entailment support often hurts performance. Moreover, reasoning degrades in three systematic ways: weaker modalities drag down overall performance, conflicts bias preference toward certain modalities, and joint signals from different modalities fail to be integrated effectively. Therefore, we identify two core failures: task-composition bottleneck, where recognition and reasoning cannot be jointly executed in one pass, and fusion bottleneck, where early integration introduces bias. For further investigation, we find that attention patterns fail to encode fact usefulness, but a simple two-step prompting (recognize then reason) restores performance, confirming the task-composition bottleneck. Moreover, modality identity remains recoverable in early layers, and softening attention in early fusion improves reasoning, highlighting biased fusion as another failure mode. Overall, our findings show that integration, not perception, is the main barrier to multimodal reasoning, suggesting composition-aware training and early fusion control as promising directions.
title Compose and Fuse: Revisiting the Foundational Bottlenecks in Multimodal Reasoning
topic Computation and Language
Artificial Intelligence
url https://arxiv.org/abs/2509.23744