arXiv Machine Learning

Uncertainty-Normalized Margins for Direct Preference Optimization

arXiv AI
Jun 29

Uncertainty-Aware Reward Discounting for Mitigating Reward Hacking

arXiv:2604. 26360v2 Announce Type: replace-cross Abstract: Reinforcement learning from human feedback (RLHF) systems face a compounding alignment challenge: not only are learned reward models uncertain about unseen state-action pairs, but the human preference annotations they are trained on are themselves inconsistent, context-dependent, and noisy.

By Disha Singha
arXiv AI
3d ago

On the Complexity of Preference-Based Bandits

The paper investigates preference-based bandits where a learner selects pairs of arms and receives binary preference feedback modeled by Bradley–Terry. It introduces the locally sensitive eluder dimension, a new complexity measure for logistic preference feedback, and proposes the GINOP algorithm that uses log-loss confidence sets to balance optimism and exploration. The authors prove a first-order regret bound showing that learning with preference feedback can be as statistically efficient as learning from direct rewards, and they validate their theory with empirical experiments.

By Ahmed Ben Yahmed (CREST, ENSAE Paris, FAIRPLAY), Marc Abeille (FAIRPLAY), Cl\'ement Calauz\`enes (FAIRPLAY)
arXiv AI
Aug 19

SCOPE: Selective Conformal Optimized Pairwise LLM Judging

SCOPE is a framework that calibrates an acceptance threshold for large language models used as pairwise judges, ensuring that the error rate among non-abstained judgments does not exceed a user-specified level α. It introduces Bidirectional Preference Entropy (BPE) to provide a bias-neutral uncertainty signal by querying the judge in both response positions and converting the averaged preference probability into an entropy-based score. Across multiple pairwise judging benchmarks, BPE outperforms standard confidence proxies in calibration and discrimination, while SCOPE consistently meets the target risk bound (empirical FDR ≈0.097–0.099 at α=0.10) and retains substantial coverage, accepting up to 2.4× more judgments under the same risk constraint.

By Sher Badshah, Ali Emami, Hassan Sajjad
arXiv Machine Learning
Sep 2

Patterning in Practice: Debiasing Reward Models with Susceptibilities

The paper introduces patterning, a reweighting technique that adjusts preference pairs based on their susceptibility to bias, to debias a Gemma 2 9B Instruct reward model trained on Skywork-Reward-Preference v0.2. Using this method, the authors achieve a +14.2 ± 1.2 percentage point improvement on the RM‑Bench Hard split while maintaining overall accuracy, matching the best reported Hard‑split gain from a comparable model. The study also demonstrates that the learned weights are interpretable, transferable across Gemma variants, and partially effective on Llama 3.1 8B.

By George Wang, Elizabeth Donoway, Daniel Murfet