Structural Uncertainty from Self-Preference in Black-Box Language Models

Baishali Chaudhury, Mengdie Flora Wang, Hyunji Hayley Park, Rahul Ghosh, Sungmin Hong, Jae Oh Woo


Abstract
Large language models can be confidently wrong, making uncertainty estimation especially important in black-box settings where token probabilities are unavailable. Existing post-hoc methods estimate uncertainty from output dispersion, treating sampled responses largely as exchangeable. We propose structural uncertainty, an observable signal derived from self-preference-induced ranking stability: given multiple sampled candidates, we elicit sparse pairwise self-preferences, aggregate them into ranking distributions via Bradley–Terry modeling with PageRank, and decompose uncertainty into two complementary entropy-based components—across-trial ranking instability and within-trial candidate ambiguity. Across five LLMs and eight benchmarks, self-preference-derived structural signals can provide information complementary to output dispersion, and their combination improves selective prediction on several reasoning and knowledge tasks. The two components relate differently to accuracy: on math reasoning, within-trial ambiguity can be positively correlated with correctness—consistent with settings where multiple plausible candidates remain competitive under self-preference ranking—whereas on factual retrieval the structural signal collapses toward uniformity, diagnosing a regime where preference-based uncertainty is uninformative. Structural uncertainty is not a universal replacement for dispersion but a regime-sensitive complementary signal.
Anthology ID:
2026.emnlp-main.699
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:
16119–16147
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URL:
https://aclanthology.org/2026.emnlp-main.699/
DOI:
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Cite (ACL):
Baishali Chaudhury, Mengdie Flora Wang, Hyunji Hayley Park, Rahul Ghosh, Sungmin Hong, and Jae Oh Woo. 2026. Structural Uncertainty from Self-Preference in Black-Box Language Models. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 16119–16147, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Structural Uncertainty from Self-Preference in Black-Box Language Models (Chaudhury et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.699.pdf