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Main Authors: Moll, Johannes, Graf, Markus, Lemke, Tristan, Lenhart, Nicolas, Truhn, Daniel, Delbrouck, Jean-Benoit, Pan, Jiazhen, Rueckert, Daniel, Adams, Lisa C., Bressem, Keno K.
Format: Preprint
Published: 2025
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Online Access:https://arxiv.org/abs/2510.11196
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author Moll, Johannes
Graf, Markus
Lemke, Tristan
Lenhart, Nicolas
Truhn, Daniel
Delbrouck, Jean-Benoit
Pan, Jiazhen
Rueckert, Daniel
Adams, Lisa C.
Bressem, Keno K.
author_facet Moll, Johannes
Graf, Markus
Lemke, Tristan
Lenhart, Nicolas
Truhn, Daniel
Delbrouck, Jean-Benoit
Pan, Jiazhen
Rueckert, Daniel
Adams, Lisa C.
Bressem, Keno K.
contents Vision-language models (VLMs) often produce chain-of-thought (CoT) explanations that sound plausible yet fail to reflect the underlying decision process, undermining trust in high-stakes clinical use. Existing evaluations rarely catch this misalignment, prioritizing answer accuracy or adherence to formats. We present a clinically grounded framework for chest X-ray visual question answering (VQA) that probes CoT faithfulness via controlled text and image modifications across three axes: clinical fidelity, causal attribution, and confidence calibration. In a reader study (n=4), evaluator-radiologist correlations fall within the observed inter-radiologist range for all axes, with strong alignment for attribution (Kendall's $τ_b=0.670$), moderate alignment for fidelity ($τ_b=0.387$), and weak alignment for confidence tone ($τ_b=0.091$), which we report with caution. Benchmarking six VLMs shows that answer accuracy and explanation quality can be decoupled, acknowledging injected cues does not ensure grounding, and text cues shift explanations more than visual cues. While some open-source models match final answer accuracy, proprietary models score higher on attribution (25.0% vs. 1.4%) and often on fidelity (36.1% vs. 31.7%), highlighting deployment risks and the need to evaluate beyond final answer accuracy.
format Preprint
id arxiv_https___arxiv_org_abs_2510_11196
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Evaluating Reasoning Faithfulness in Medical Vision-Language Models using Multimodal Perturbations
Moll, Johannes
Graf, Markus
Lemke, Tristan
Lenhart, Nicolas
Truhn, Daniel
Delbrouck, Jean-Benoit
Pan, Jiazhen
Rueckert, Daniel
Adams, Lisa C.
Bressem, Keno K.
Computation and Language
Computer Vision and Pattern Recognition
Vision-language models (VLMs) often produce chain-of-thought (CoT) explanations that sound plausible yet fail to reflect the underlying decision process, undermining trust in high-stakes clinical use. Existing evaluations rarely catch this misalignment, prioritizing answer accuracy or adherence to formats. We present a clinically grounded framework for chest X-ray visual question answering (VQA) that probes CoT faithfulness via controlled text and image modifications across three axes: clinical fidelity, causal attribution, and confidence calibration. In a reader study (n=4), evaluator-radiologist correlations fall within the observed inter-radiologist range for all axes, with strong alignment for attribution (Kendall's $τ_b=0.670$), moderate alignment for fidelity ($τ_b=0.387$), and weak alignment for confidence tone ($τ_b=0.091$), which we report with caution. Benchmarking six VLMs shows that answer accuracy and explanation quality can be decoupled, acknowledging injected cues does not ensure grounding, and text cues shift explanations more than visual cues. While some open-source models match final answer accuracy, proprietary models score higher on attribution (25.0% vs. 1.4%) and often on fidelity (36.1% vs. 31.7%), highlighting deployment risks and the need to evaluate beyond final answer accuracy.
title Evaluating Reasoning Faithfulness in Medical Vision-Language Models using Multimodal Perturbations
topic Computation and Language
Computer Vision and Pattern Recognition
url https://arxiv.org/abs/2510.11196