Syntactic Framing Fragility: An Audit of Robustness in LLM Ethical Decisions
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Abstract (arXiv)
Large language models exhibit systematic negation sensitivity, yet no operational framework exists to measure this vulnerability at deployment scale, especially in high-stakes decisions. We introduce Syntactic Framing Fragility (SFF), a framework for quantifying decision consistency under logically equivalent syntactic transformations. SFF isolates syntactic effects via Logical Polarity Normalization, enabling direct comparison across positive and negative framings while controlling for polarity inversion, and provides the Syntactic Variation Index (SVI) as a robustness metric suitable for CI/CD integration. Auditing 23 models across 14 high-stakes scenarios (39,975 decisions), we establish ground-truth effect sizes for a phenomenon previously characterized only qualitatively and find that open-source models exhibit 2.2x higher fragility than commercial counterparts. Negation-bearing syntax is the dominant failure mode, with some models endorsing actions at 80-97% rates even when asked whether agents not act. These patterns are consistent with negation suppression failure documented in prior work, with chain-of-thought reasoning reducing fragility in some but not all cases. We provide scenario-stratified risk profiles and offer an operational checklist compatible with EU AI Act and NIST RMF requirements. Code, data, and scenarios will be released upon publication.
Key facts. Cited by 2 papers in the map (data through 14 Oct 2026). Builds on 27 of its 45 references that are in the map. First posted on arXiv 27 Dec 2025.
Builds on
27 of 45 references.
References · 27
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15 more
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- 2023Evaluating the Moral Beliefs Encoded in LLMscited by 215
- 2021What Will it Take to Fix Benchmarking in Natural Language Understanding?cited by 203
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Citing papers per year: 2026: 2.
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