Is LLM's Moral Decision Compositional?

Title:Is LLM's Moral Decision Compositional?

Abstract:Moral evaluations of language models typically infer a model's values from its choices between single acts, yet in everyday life a person is judged on their history of good and bad acts. Such evaluations cannot capture how a model combines one person's acts. We test whether a model's moral judgment is compositional, that is, whether its judgment of a person follows from its judgments of each act. We introduce Moral Composition Arena, which asks which of two people is morally better to give Elo ratings to 229 human-validated acts across five Moral Foundations Theory foundations (act Elo) and to 160 controlled composite profiles, each a person described by two acts (composite Elo). Across ten frontier models and 29,134 choices, summed act Elo explains 73% of the variance in composite Elo, but the composition rule is not additive. With nearly equal mean summed act Elo, one extreme virtue with a minor wrong outranks two minor virtues in every model (mean +35.0 Elo), an extremity premium that survives a nonlinear baseline and human relabeling of act intensities. Single-act evaluations thus predict most of how these models judge people described by two acts, but miss a systematic premium on extreme acts.

Computation and Language (cs.CL); Artificial Intelligence (cs.AI)

arXiv:2606.11232 [cs.CL]

(or arXiv:2606.11232v2 [cs.CL] for this version)

https://doi.org/10.48550/arXiv.2606.11232 Focus to learn more arXiv-issued DOI via DataCite

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