The Devil is in the EOS: Sequence Training for Detailed Image Captioning

Fuente: arXiv
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Hauptverfasser: Mohamed, Abdelrahman, Kementchedjhieva, Yova
Format: Preprint
Veröffentlicht: 2025
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author Mohamed, Abdelrahman
Kementchedjhieva, Yova
author_facet Mohamed, Abdelrahman
Kementchedjhieva, Yova
contents Despite significant advances in vision-language models (VLMs), image captioning often suffers from a lack of detail, with base models producing short, generic captions. This limitation persists even though VLMs are equipped with strong vision and language backbones. While supervised data and complex reward functions have been proposed to improve detailed image captioning, we identify a simpler underlying issue: a bias towards the end-of-sequence (EOS) token, which is introduced during cross-entropy training. We propose an unsupervised method to debias the model's tendency to predict the EOS token prematurely. By reducing this bias, we encourage the generation of longer, more detailed captions without the need for intricate reward functions or supervision. Our approach is straightforward, effective, and easily applicable to any pretrained model. We demonstrate its effectiveness through experiments with three VLMs and on three detailed captioning benchmarks. Our results show a substantial increase in caption length and relevant details, albeit with an expected increase in the rate of hallucinations.
format Preprint
id arxiv_https___arxiv_org_abs_2507_20077
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The Devil is in the EOS: Sequence Training for Detailed Image Captioning
Mohamed, Abdelrahman
Kementchedjhieva, Yova
Computer Vision and Pattern Recognition
Computation and Language
Despite significant advances in vision-language models (VLMs), image captioning often suffers from a lack of detail, with base models producing short, generic captions. This limitation persists even though VLMs are equipped with strong vision and language backbones. While supervised data and complex reward functions have been proposed to improve detailed image captioning, we identify a simpler underlying issue: a bias towards the end-of-sequence (EOS) token, which is introduced during cross-entropy training. We propose an unsupervised method to debias the model's tendency to predict the EOS token prematurely. By reducing this bias, we encourage the generation of longer, more detailed captions without the need for intricate reward functions or supervision. Our approach is straightforward, effective, and easily applicable to any pretrained model. We demonstrate its effectiveness through experiments with three VLMs and on three detailed captioning benchmarks. Our results show a substantial increase in caption length and relevant details, albeit with an expected increase in the rate of hallucinations.
title The Devil is in the EOS: Sequence Training for Detailed Image Captioning
topic Computer Vision and Pattern Recognition
Computation and Language
url https://arxiv.org/abs/2507.20077