Vision-language models (VLMs) allow to embed texts and images in a shared representation space. However, it has been shown that these models are subject to a modality gap phenomenon meaning there exists a clear separation between the embeddings from one modality and another in the embedding space. While this misalignment is detrimental for downstream tasks such as multimodal retrieval, multimodal clustering or zero-shot classification, etc. no generic and practical methods have so far been proposed to assess it precisely and even reduce it. We therefore propose novel measures and effective techniques (spectral- and optimal transport-based methods) to achieve this goal. Extensive experiments conducted on several image-text datasets and models demonstrate their effectiveness and beneficial effects on downstream tasks. Our code is available at the URL provided in the paper's abstract.
@article{arxiv.2505.03703,
title = {Fill the Gap: Quantifying and Reducing the Modality Gap in Image-Text Representation Learning},
author = {François Role and Sébastien Meyer and Victor Amblard},
journal= {arXiv preprint arXiv:2505.03703},
year = {2025}
}