MoralTrajectories: Evaluating Moral Steerability in Large Language Models

Daniel Russo, Marco Antonio Stranisci, Oscar Araque, Marco Guerini


Abstract
Large language models are increasingly deployed in contexts where contested social and political values are at stake, yet we lack a systematic understanding of how their moral priors shape what they generate. We introduce **‘MoralTrajectories‘**, a benchmark for probing morally grounded generation across contentious political and social topics. The benchmark pairs questions from the AllSides Red Blue Translator with first-person belief statements operationalizing the six foundations of Moral Foundations Theory to construct, for each model and topic, a full *moral trajectory*: seven responses spanning an unconstrained baseline and one condition per foundation. We evaluate eight instruction-tuned models across families and sizes using lexical and semantic similarity, distributional divergence, and token-level uncertainty analysis, supported by a human annotation study. Three findings emerge consistently: unconstrained models default to CARE-oriented language, attributable to the empathy-rewarding objectives of instruction tuning; moral prompting shifts generation in foundation-consistent ways, but the effect is predominantly surface-level; and steerability varies substantially across model families and topics. Together, these results suggest that current alignment training collapses moral diversity into a narrow register, and that recovering genuine moral plurality in generation remains an open challenge.
Anthology ID:
2026.findings-emnlp.2432
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
Note:
Pages:
52200–52216
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.2432/
DOI:
Bibkey:
Cite (ACL):
Daniel Russo, Marco Antonio Stranisci, Oscar Araque, and Marco Guerini. 2026. MoralTrajectories: Evaluating Moral Steerability in Large Language Models. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 52200–52216, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
MoralTrajectories: Evaluating Moral Steerability in Large Language Models (Russo et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.2432.pdf