Beyond RLHF and NLHF: Population-Proportional Alignment under an Axiomatic Framework

Fuente: arXiv
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Auteurs principaux: Kim, Kihyun, Zhang, Jiawei, Ozdaglar, Asuman, Parrilo, Pablo A.
Format: Preprint
Publié: 2025
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author Kim, Kihyun
Zhang, Jiawei
Ozdaglar, Asuman
Parrilo, Pablo A.
author_facet Kim, Kihyun
Zhang, Jiawei
Ozdaglar, Asuman
Parrilo, Pablo A.
contents Conventional preference learning methods often prioritize opinions held more widely when aggregating preferences from multiple evaluators. This may result in policies that are biased in favor of some types of opinions or groups and susceptible to strategic manipulation. To address this issue, we develop a novel preference learning framework capable of aligning aggregate opinions and policies proportionally with the true population distribution of evaluator preferences. Grounded in social choice theory, our approach infers the feasible set of evaluator population distributions directly from pairwise comparison data. Using these estimates, the algorithm constructs a policy that satisfies foundational axioms from social choice theory, namely monotonicity and Pareto efficiency, as well as our newly-introduced axioms of population-proportional alignment and population-bounded manipulability. Moreover, we propose a soft-max relaxation method that smoothly trades off population-proportional alignment with the selection of the Condorcet winner (which beats all other options in pairwise comparisons). Finally, we validate the effectiveness and scalability of our approach through experiments on both tabular recommendation tasks and large language model alignment.
format Preprint
id arxiv_https___arxiv_org_abs_2506_05619
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Beyond RLHF and NLHF: Population-Proportional Alignment under an Axiomatic Framework
Kim, Kihyun
Zhang, Jiawei
Ozdaglar, Asuman
Parrilo, Pablo A.
Artificial Intelligence
Machine Learning
Conventional preference learning methods often prioritize opinions held more widely when aggregating preferences from multiple evaluators. This may result in policies that are biased in favor of some types of opinions or groups and susceptible to strategic manipulation. To address this issue, we develop a novel preference learning framework capable of aligning aggregate opinions and policies proportionally with the true population distribution of evaluator preferences. Grounded in social choice theory, our approach infers the feasible set of evaluator population distributions directly from pairwise comparison data. Using these estimates, the algorithm constructs a policy that satisfies foundational axioms from social choice theory, namely monotonicity and Pareto efficiency, as well as our newly-introduced axioms of population-proportional alignment and population-bounded manipulability. Moreover, we propose a soft-max relaxation method that smoothly trades off population-proportional alignment with the selection of the Condorcet winner (which beats all other options in pairwise comparisons). Finally, we validate the effectiveness and scalability of our approach through experiments on both tabular recommendation tasks and large language model alignment.
title Beyond RLHF and NLHF: Population-Proportional Alignment under an Axiomatic Framework
topic Artificial Intelligence
Machine Learning
url https://arxiv.org/abs/2506.05619