When Linguistic and Internal Confidence Diverge in Large Language Models

Hefan Zhang, Bingquan Zhang, Ming Cheng, Saeed Hassanpour, Weicheng Ma, Soroush Vosoughi


Abstract
Users often ask large language models (LLMs) to report how confident they are, but it is unclear whether such linguistic confidence tracks the model’s internal confidence. We study this question across 8 classification tasks, 2 generation tasks and 30 models from three families. For classification, we compare linguistic confidence with logits-based confidence along three axes: association, magnitude agreement and calibration. For generation, we test whether linguistic confidence tracks semantic-entropy-based uncertainty. The axes frequently diverge. Instance-level association is weak on average, although it improves on easier items and for stronger base models. Instruction-tuned models often report higher confidence and sometimes show higher association, but they also have larger confidence gaps and worse calibration. Prompt design mostly changes the distribution of reported confidence. Attitude cues inflate confidence without improving alignment, while score exemplars can preserve rank-order signal when they avoid collapsed confidence values. Regression analyses show that distributional properties of confidence scores explain much of the observed alignment pattern, with model metadata playing a smaller role after controls. These results support a lossy-channel view of linguistic confidence. A more dispersed verbal confidence distribution can carry useful rank information, but it does not make the scores calibrated. Linguistic confidence should therefore be evaluated with multi-axis diagnostics before being used in downstream reliability pipelines.
Anthology ID:
2026.findings-emnlp.1300
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
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SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
27492–27517
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1300/
DOI:
Bibkey:
Cite (ACL):
Hefan Zhang, Bingquan Zhang, Ming Cheng, Saeed Hassanpour, Weicheng Ma, and Soroush Vosoughi. 2026. When Linguistic and Internal Confidence Diverge in Large Language Models. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 27492–27517, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
When Linguistic and Internal Confidence Diverge in Large Language Models (Zhang et al., Findings 2026)
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https://aclanthology.org/2026.findings-emnlp.1300.pdf