Massively Multimodal Foundation Models: A Framework for Capturing Interactions with Specialized Mixture-of-Experts

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Main Authors: Han, Xing, Chung, Hsing-Huan, Ghosh, Joydeep, Liang, Paul Pu, Saria, Suchi
Format: Preprint
Published: 2025
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author Han, Xing
Chung, Hsing-Huan
Ghosh, Joydeep
Liang, Paul Pu
Saria, Suchi
author_facet Han, Xing
Chung, Hsing-Huan
Ghosh, Joydeep
Liang, Paul Pu
Saria, Suchi
contents Modern applications increasingly involve many heterogeneous input streams, such as clinical sensors, wearable device data, imaging, and text, each with distinct measurement models, sampling rates, and noise characteristics. We define this as massively multimodal setting, where each sensor constitutes a separate modality. As modality counts grow, capturing their complex, time-varying interactions such as delayed physiological cascades between sensors, has becomes essential yet challenging. Mixture-of-Experts (MoE) architectures are naturally suited for this setting since their sparse routing mechanism enables efficient scaling across many modalities. However, existing MoE architectures route tokens based on similarity alone, overlooking the rich temporal dependencies across modalities: this prevents the model from capturing delayed cross-modal effects, leading to suboptimal expert specialization and reduced accuracy. We propose a framework that explicitly quantifies temporal dependencies between modality pairs across multiple discrete time intervals, defined as delays between an event in one input stream and its manifested effect in another, and uses these to guide MoE routing. A interaction-aware router dispatches tokens to specialized experts based on interaction type. This principled routing enables experts to learn generalizable interaction-processing skills. Experiments across healthcare, activity recognition, and affective computing benchmarks demonstrate substantial performance gains and interpretable routing patterns aligned with domain knowledge.
format Preprint
id arxiv_https___arxiv_org_abs_2509_25678
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Massively Multimodal Foundation Models: A Framework for Capturing Interactions with Specialized Mixture-of-Experts
Han, Xing
Chung, Hsing-Huan
Ghosh, Joydeep
Liang, Paul Pu
Saria, Suchi
Machine Learning
Modern applications increasingly involve many heterogeneous input streams, such as clinical sensors, wearable device data, imaging, and text, each with distinct measurement models, sampling rates, and noise characteristics. We define this as massively multimodal setting, where each sensor constitutes a separate modality. As modality counts grow, capturing their complex, time-varying interactions such as delayed physiological cascades between sensors, has becomes essential yet challenging. Mixture-of-Experts (MoE) architectures are naturally suited for this setting since their sparse routing mechanism enables efficient scaling across many modalities. However, existing MoE architectures route tokens based on similarity alone, overlooking the rich temporal dependencies across modalities: this prevents the model from capturing delayed cross-modal effects, leading to suboptimal expert specialization and reduced accuracy. We propose a framework that explicitly quantifies temporal dependencies between modality pairs across multiple discrete time intervals, defined as delays between an event in one input stream and its manifested effect in another, and uses these to guide MoE routing. A interaction-aware router dispatches tokens to specialized experts based on interaction type. This principled routing enables experts to learn generalizable interaction-processing skills. Experiments across healthcare, activity recognition, and affective computing benchmarks demonstrate substantial performance gains and interpretable routing patterns aligned with domain knowledge.
title Massively Multimodal Foundation Models: A Framework for Capturing Interactions with Specialized Mixture-of-Experts
topic Machine Learning
url https://arxiv.org/abs/2509.25678