Unexplored flaws in multiple-choice VQA evaluations

Fuente: arXiv
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Main Authors: Rosenthal, Fabio, Schmidt, Sebastian, Graf, Thorsten, Bagodonat, Thorsten, Günnemann, Stephan, Schwinn, Leo
Format: Preprint
Published: 2025
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author Rosenthal, Fabio
Schmidt, Sebastian
Graf, Thorsten
Bagodonat, Thorsten
Günnemann, Stephan
Schwinn, Leo
author_facet Rosenthal, Fabio
Schmidt, Sebastian
Graf, Thorsten
Bagodonat, Thorsten
Günnemann, Stephan
Schwinn, Leo
contents Multimodal Large Language Models (MLLMs) demonstrate strong capabilities in handling image-text inputs. A common way to assess this ability is through multiple-choice Visual Question Answering (VQA). Earlier works have already revealed that these benchmarks are sensitive to answer choice order, a limitation that can be mitigated through careful design. Yet, we highlight additional, unexplored biases in prompt formatting that question the reliability of current MLLM evaluations. Specifically, we identify three key variation factors in prompt formatting and analyze their impact through a large-scale study involving $\mathbf{\text{seven}}$ MLLMs and $\mathbf{\text{five}}$ VQA datasets, spanning $\mathbf{48}$ distinct $\mathbf{\text{prompt format variations}}$. Our findings reveal that multiple-choice VQA is highly sensitive to minor prompt format changes, even when these changes are semantically neutral. We further demonstrate that these biases persist independently of known order biases or the MLLM's confidence in the correct answer. Finally, we demonstrate that existing bias mitigation strategies fail to address these newly identified biases.
format Preprint
id arxiv_https___arxiv_org_abs_2511_22341
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Unexplored flaws in multiple-choice VQA evaluations
Rosenthal, Fabio
Schmidt, Sebastian
Graf, Thorsten
Bagodonat, Thorsten
Günnemann, Stephan
Schwinn, Leo
Computer Vision and Pattern Recognition
Machine Learning
Multimodal Large Language Models (MLLMs) demonstrate strong capabilities in handling image-text inputs. A common way to assess this ability is through multiple-choice Visual Question Answering (VQA). Earlier works have already revealed that these benchmarks are sensitive to answer choice order, a limitation that can be mitigated through careful design. Yet, we highlight additional, unexplored biases in prompt formatting that question the reliability of current MLLM evaluations. Specifically, we identify three key variation factors in prompt formatting and analyze their impact through a large-scale study involving $\mathbf{\text{seven}}$ MLLMs and $\mathbf{\text{five}}$ VQA datasets, spanning $\mathbf{48}$ distinct $\mathbf{\text{prompt format variations}}$. Our findings reveal that multiple-choice VQA is highly sensitive to minor prompt format changes, even when these changes are semantically neutral. We further demonstrate that these biases persist independently of known order biases or the MLLM's confidence in the correct answer. Finally, we demonstrate that existing bias mitigation strategies fail to address these newly identified biases.
title Unexplored flaws in multiple-choice VQA evaluations
topic Computer Vision and Pattern Recognition
Machine Learning
url https://arxiv.org/abs/2511.22341