Untangling Input Language from Reasoning Language: A Diagnostic Framework for Cross-Lingual Moral Alignment in LLMs

Nan Li, Bo Kang, Tijl De Bie


Abstract
When LLMs judge moral dilemmas, do they reach different conclusions in different languages, and if so, why? Two factors could drive such differences: the language of the dilemma itself, or the language in which the model is instructed to express its reasoning. Standard evaluation conflates these by testing only matched conditions (e.g., English dilemma with English reasoning). We introduce a methodology that separately manipulates each factor, covering also mismatched conditions (e.g., English dilemma with Chinese reasoning), enabling decomposition of their contributions. To study what changes, we propose an approach to interpret the moral judgments in terms of Moral Foundations Theory. As a side result, we identify evidence for splitting the Authority dimension into a family-related and an institutional dimension. Applying this methodology to English-Chinese moral judgment with 13 LLMs, we demonstrate its diagnostic power: (1) in this EN–CN case study, the framework isolates the language of generated rationale as contributing roughly twice the variance of input-language effects; (2) it detects context-dependency in 4 of 9 EN–CN-tested models that standard evaluation misses; and (3) a diagnostic taxonomy translates these patterns into deployment guidance. We release our code and datasets at https://github.com/aida-ugent/LLMCrossCulturalMoralJudgement.
Anthology ID:
2026.findings-emnlp.5
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
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
68–94
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.5/
DOI:
Bibkey:
Cite (ACL):
Nan Li, Bo Kang, and Tijl De Bie. 2026. Untangling Input Language from Reasoning Language: A Diagnostic Framework for Cross-Lingual Moral Alignment in LLMs. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 68–94, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Untangling Input Language from Reasoning Language: A Diagnostic Framework for Cross-Lingual Moral Alignment in LLMs (Li et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.5.pdf