🤖 AI Summary
This work explores the design space of natively multimodal foundation models, addressing how to effectively integrate vision and language beyond conventional language modeling. Building upon the Transfusion framework, the authors propose a unified pretraining approach from scratch that jointly leverages next-token prediction and diffusion-based generation, augmented with a Representation Autoencoder (RAE) to unify visual representations for both understanding and generation. The study reveals the complementary nature and asymmetric scaling behavior of vision and language data—where vision benefits more substantially from increased data volume—and employs a Mixture-of-Experts (MoE) architecture to enable efficient modality specialization and model expansion. Experiments demonstrate that unified pretraining naturally induces world modeling capabilities and significantly enhances performance on downstream tasks, laying a foundation for truly integrated multimodal foundation models.
📝 Abstract
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.