Shared Doubt: Zero-Shot Cross-Lingual Confidence Estimation for Language Models

Athina Kyriakou, Dennis Ulmer, Ivan Titov


Abstract
Confidence estimation (CE), i.e. quantifying the reliability of a model’s prediction, has attracted great interest in the context of large language models (LLMs). However, most studies focus on English, ignoring the multilingual reality of LLM usage, while many CE methods degrade or require retraining across languages. To address this gap, we investigate whether multilingual LLMs encode shared, language-transferable confidence features in open-ended question answering. We use a lightweight linear probe that predicts answer correctness directly from intermediate representations. Trained monolingually, the probe generalizes zero-shot to unseen, linguistically diverse languages without target-language supervision. Multiple ablations and learned layer weights reveal that confidence features concentrate in middle layers across languages, suggesting a shared confidence subspace. While zero-shot cross-lingual performance depends on similarity to the source language, the probe provides a strong baseline without any retraining and compares favorably to other popular confidence estimation methods.
Anthology ID:
2026.emnlp-main.2654
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:
60407–60437
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2654/
DOI:
Bibkey:
Cite (ACL):
Athina Kyriakou, Dennis Ulmer, and Ivan Titov. 2026. Shared Doubt: Zero-Shot Cross-Lingual Confidence Estimation for Language Models. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 60407–60437, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Shared Doubt: Zero-Shot Cross-Lingual Confidence Estimation for Language Models (Kyriakou et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.2654.pdf