Chartographer: Counterfactual Chart Generation for Evaluating Vision-Language Models

Yifan Jiang, Dae Yon Hwang, Jesse C. Cresswell, Freda Shi


Abstract
Chart question-answering (QA) benchmarks aim to pose questions that require visual reasoning to correctly answer, but vision-language models (VLMs) can often reach solutions through shortcuts or prior familiarity with a chart or question. To strictly evaluate visual reasoning, we propose counterfactual charts where the chart-question task remains fixed, but the underlying data and the corresponding answer are varied. We introduce CHARTOGRAPHER, a framework to reverse engineer charts into executable code, validate reconstruction fidelity, generate counterfactual variants, and derive new answers from executable QA logic. We apply this framework to existing chart QA datasets and evaluate proprietary and open-source VLMs, measuring variant sensitivity and generalizability. Counterfactual charts reveal failures hidden by single-chart performance: VLMs often fail to generalize after answering the original chart correctly. We find that failures are most prevalent when updated charts require novel visual reasoning pathways.
Anthology ID:
2026.emnlp-main.580
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
13272–13293
Language:
URL:
https://aclanthology.org/2026.emnlp-main.580/
DOI:
Bibkey:
Cite (ACL):
Yifan Jiang, Dae Yon Hwang, Jesse C. Cresswell, and Freda Shi. 2026. Chartographer: Counterfactual Chart Generation for Evaluating Vision-Language Models. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 13272–13293, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Chartographer: Counterfactual Chart Generation for Evaluating Vision-Language Models (Jiang et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.580.pdf