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Bibliographic Details
Main Authors: Tong, Shengbang, Fan, David, Nguyen, John, Brown, Ellis, Zhou, Gaoyue, Qian, Shengyi, Zheng, Boyang, Vallaeys, Théophane, Han, Junlin, Fergus, Rob, Murray, Naila, Ghazvininejad, Marjan, Lewis, Mike, Ballas, Nicolas, Bar, Amir, Rabbat, Michael, Verbeek, Jakob, Zettlemoyer, Luke, Sinha, Koustuv, LeCun, Yann, Xie, Saining
Format: Preprint
Published: 2026
Subjects:
Online Access:https://arxiv.org/abs/2603.03276
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Table of Contents:
  • The visual world offers a critical axis for advancing foundation models beyond language. Despite growing interest in this direction, the design space for native multimodal models remains opaque. We provide empirical clarity through controlled, from-scratch pretraining experiments, isolating the factors that govern multimodal pretraining without interference from language pretraining. We adopt the Transfusion framework, using next-token prediction for language and diffusion for vision, to train on diverse data including text, video, image-text pairs, and even action-conditioned video. Our experiments yield four key insights: (i) Representation Autoencoder (RAE) provides an optimal unified visual representation by excelling at both visual understanding and generation; (ii) visual and language data are complementary and yield synergy for downstream capabilities; (iii) unified multimodal pretraining leads naturally to world modeling, with capabilities emerging from general training; and (iv) Mixture-of-Experts (MoE) enables efficient and effective multimodal scaling while naturally inducing modality specialization. Through IsoFLOP analysis, we compute scaling laws for both modalities and uncover a scaling asymmetry: vision is significantly more data-hungry than language. We demonstrate that the MoE architecture harmonizes this scaling asymmetry by providing the high model capacity required by language while accommodating the data-intensive nature of vision, paving the way for truly unified multimodal models.