Beyond Caption Loss: Generative Distillation for Modality Alignment in Vision-Language Models

Nam Kha Nguyen, Wei Emma Zhang, Xiang Dai, Mong Yuan Sim, Weitong Chen


Abstract
Vision-language models align frozen vision encoders to language models using only a next-token prediction loss, an asymmetric signal that discards rich visual signals not captured in the captions. We propose GenDA (Generative Distillation Alignment), a novel training framework that augments the captioning loss with a generative distillation objective from a frozen text-to-image diffusion model. GenDA concatenates selected visual tokens with the encoded caption to form a joint conditioning signal, encouraging these tokens to encode visual information not already captured by the caption. Across five vision encoders and four language models, GenDA gains 3-9 CIDEr points over LLaVA-1.5 on five captioning benchmarks. These gains also transfer to downstream VLM benchmarks while preserving the encoders’ discriminative performance. Visual preservation and modality-gap analyses suggest that visual information is retained deeper within the LLM, while visual features become more closely aligned with the language representation space.
Anthology ID:
2026.findings-emnlp.1876
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
40021–40034
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1876/
DOI:
Bibkey:
Cite (ACL):
Nam Kha Nguyen, Wei Emma Zhang, Xiang Dai, Mong Yuan Sim, and Weitong Chen. 2026. Beyond Caption Loss: Generative Distillation for Modality Alignment in Vision-Language Models. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 40021–40034, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Beyond Caption Loss: Generative Distillation for Modality Alignment in Vision-Language Models (Nguyen et al., Findings 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.findings-emnlp.1876.pdf