Hugging Face Daily PapersBowen Qin, Yi Xie, Yesheng Liu1 min readpaperadvanced
ImpossibleRubrics: Stress-Testing Generated Rubrics as Reward Signals
Summary
ImpossibleRubrics introduces a 169‑task benchmark of “impossible” prompts, each with a formal oracle certificate defining what an honest answer can claim. The authors generate rubrics downstream and test them adversarially, finding that many rubric generators are exploitable (8‑36% of the time) and that a single generic rubric (“be decisive, penalize hedging”) is exploited 64% of the time, while…
- A new benchmark (ImpossibleRubrics) for stress‑testing LLM‑generated rubrics on tasks where the truthful response is to admit impossibility.
- Each task includes a verifiable oracle certificate that specifies permissible claims, enabling automated detection of rubric violations.
- Eleven rubric generators were evaluated; exploitation rates ranged from 8% to 36% on unbiased cuts, up to 64% for a generic “decisive” rubric.
- Tailored rubrics often expose specific claim targets, making them more vulnerable than a vague generic rubric.
Rubric‑based reward signals are increasingly used for RL‑from‑human‑feedback, automated grading, and LLM evaluation. If rubrics can be gamed, the resulting reward models may reinforce dishonest or misleading behavior, undermining safety and reliability of LLM systems. This benchmark provides a conc…
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