Hidden in plain sight: VLMs overlook their visual representations

Fuente: arXiv
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Main Authors: Fu, Stephanie, Bonnen, Tyler, Guillory, Devin, Darrell, Trevor
Format: Preprint
Published: 2025
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author Fu, Stephanie
Bonnen, Tyler
Guillory, Devin
Darrell, Trevor
author_facet Fu, Stephanie
Bonnen, Tyler
Guillory, Devin
Darrell, Trevor
contents Language provides a natural interface to specify and evaluate performance on visual tasks. To realize this possibility, vision language models (VLMs) must successfully integrate visual and linguistic information. Our work compares VLMs to a direct readout of their visual encoders to understand their ability to integrate across these modalities. Across a series of vision-centric benchmarks (e.g., depth estimation, correspondence), we find that VLMs perform substantially worse than their visual encoders, dropping to near-chance performance. We investigate these results through a series of analyses across the entire VLM: namely 1) the degradation of vision representations, 2) brittleness to task prompt, and 3) the language model's role in solving the task. We find that the bottleneck in performing these vision-centric tasks lies in this third category; VLMs are not effectively using visual information easily accessible throughout the entire model, and they inherit the language priors present in the LLM. Our work helps diagnose the failure modes of open-source VLMs, and presents a series of evaluations useful for future investigations into visual understanding within VLMs.
format Preprint
id arxiv_https___arxiv_org_abs_2506_08008
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Hidden in plain sight: VLMs overlook their visual representations
Fu, Stephanie
Bonnen, Tyler
Guillory, Devin
Darrell, Trevor
Computer Vision and Pattern Recognition
Artificial Intelligence
Machine Learning
Language provides a natural interface to specify and evaluate performance on visual tasks. To realize this possibility, vision language models (VLMs) must successfully integrate visual and linguistic information. Our work compares VLMs to a direct readout of their visual encoders to understand their ability to integrate across these modalities. Across a series of vision-centric benchmarks (e.g., depth estimation, correspondence), we find that VLMs perform substantially worse than their visual encoders, dropping to near-chance performance. We investigate these results through a series of analyses across the entire VLM: namely 1) the degradation of vision representations, 2) brittleness to task prompt, and 3) the language model's role in solving the task. We find that the bottleneck in performing these vision-centric tasks lies in this third category; VLMs are not effectively using visual information easily accessible throughout the entire model, and they inherit the language priors present in the LLM. Our work helps diagnose the failure modes of open-source VLMs, and presents a series of evaluations useful for future investigations into visual understanding within VLMs.
title Hidden in plain sight: VLMs overlook their visual representations
topic Computer Vision and Pattern Recognition
Artificial Intelligence
Machine Learning
url https://arxiv.org/abs/2506.08008