The Role of Ambiguity in Error Prediction via Uncertainty Quantification

Ieva Raminta Staliunaite, James Bishop, Andreas Vlachos


Abstract
The task of Error Prediction, namely predicting whether a model output is correct, is commonly tackled with Uncertainty Quantification (UQ). However, while uncertainty metrics capture when models lack knowledge or capacity to make a prediction, they also reflect aleatoric uncertainty, inherent in the input and context. We improve error prediction for Large Language Models (LLMs) by disentangling input ambiguity from the UQ signal. We experiment on Question Answering (QA) with six UQ metrics and show that UQ metrics are more predictive of errors on unambiguous instances than on questions with multiple plausible answers. We use Gated Experts and Selective Prediction to incorporate gold and predicted ambiguity labels into the error prediction pipeline. We find that ambiguity information improves error prediction across model families, training and evaluation paradigms, and datasets (including allegedly unambiguous ones), with the gains concentrated on the UQ metrics that most entangle aleatoric and epistemic uncertainty, gaining over 10 PRR points for individual metrics.
Anthology ID:
2026.uncertainlp-main.22
Volume:
The Proceedings of the Third Workshop on Uncertainty-Aware NLP
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Wilker Aziz, Jonathan Berant, Bryan Eikema, Evgenia Ilia, Marie-Catherine de Marneffe, Barbara Plank, Artem Shelmanov, Swabha Swayamdipta, Jörg Tiedemann, Artem Vazhentsev, Raúl Vázquez, Chrysoula Zerva
Venues:
UncertaiNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
356–380
Language:
URL:
https://aclanthology.org/2026.uncertainlp-main.22/
DOI:
Bibkey:
Cite (ACL):
Ieva Raminta Staliunaite, James Bishop, and Andreas Vlachos. 2026. The Role of Ambiguity in Error Prediction via Uncertainty Quantification. In The Proceedings of the Third Workshop on Uncertainty-Aware NLP, pages 356–380, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
The Role of Ambiguity in Error Prediction via Uncertainty Quantification (Staliunaite et al., UncertaiNLP 2026)
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PDF:
https://aclanthology.org/2026.uncertainlp-main.22.pdf