What do Reward Models Memorize?

Title:What do Reward Models Memorize?

Abstract:This paper studies what discriminatively trained reward models (RMs) memorize by measuring counterfactual memorization on two human preference datasets. We show that RMs 1) misallocate memorization to easy, high margin preference pairs, 2) memorize dataset-specific shortcuts (e.g., model identity, user sampling strategy), and 3) overgeneralize simple heuristic correlates of human preference (e.g., length, compliance) when confronted with unseen preference pairs. Overall, our findings indicate that discriminative training of RMs from human preference data results in biased RMs not yet capable of judging response quality in context-dependent scenarios.

Machine Learning (cs.LG); Computation and Language (cs.CL)

arXiv:2607.24484 [cs.LG]

(or arXiv:2607.24484v1 [cs.LG] for this version)

https://doi.org/10.48550/arXiv.2607.24484 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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