Exploring Confirmation Bias: LLMs Perceive Democratic Claims as More Truthful Independently of their Content

Charlott Jakob, Jing Yang, Daniel Renken, Veronika Solopova, Max Upravitelev, Sebastian Möller, Vera Schmitt


Abstract
Large Language Models (LLMs) are increasingly used to detect misinformation and support human fact-checkers. However, their truthfulness assessments may be affected by systematic political biases. Motivated by confirmation bias in humans, i.e., interpreting evidence in ways that are partial to existing beliefs or expectations, we investigate whether LLMs assess truthfulness in line with their political attitudes. We compare LLMs’ political attitudinal bias (PB-A) with political bias in truthfulness perception (PB-T). We assess PB-T by prompting LLMs to evaluate Democratic and Republican claims, including conditions where the claim-making party is explicitly stated. Across 20 instruction-tuned LLMs, all models exhibit a left-leaning tendency in PB-T, statistically significant for roughly half of them. Moreover, 16 out of 20 models significantly factor in the claim maker’s party affiliation when predicting truthfulness. PB-T and PB-A correlate weakly to moderately, and larger models tend to exhibit more left-leaning PB-T. The code for reproducibility is available on GitHub.
Anthology ID:
2026.emnlp-main.1615
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:
36718–36732
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1615/
DOI:
Bibkey:
Cite (ACL):
Charlott Jakob, Jing Yang, Daniel Renken, Veronika Solopova, Max Upravitelev, Sebastian Möller, and Vera Schmitt. 2026. Exploring Confirmation Bias: LLMs Perceive Democratic Claims as More Truthful Independently of their Content. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 36718–36732, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Exploring Confirmation Bias: LLMs Perceive Democratic Claims as More Truthful Independently of their Content (Jakob et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1615.pdf