PB$^2$: Preference Space Exploration via Population-Based Methods in Preference-Based Reinforcement Learning

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Hauptverfasser: Driss, Brahim, Davey, Alex, Akrour, Riad
Format: Preprint
Veröffentlicht: 2025
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author Driss, Brahim
Davey, Alex
Akrour, Riad
author_facet Driss, Brahim
Davey, Alex
Akrour, Riad
contents Preference-based reinforcement learning (PbRL) has emerged as a promising approach for learning behaviors from human feedback without predefined reward functions. However, current PbRL methods face a critical challenge in effectively exploring the preference space, often converging prematurely to suboptimal policies that satisfy only a narrow subset of human preferences. In this work, we identify and address this preference exploration problem through population-based methods. We demonstrate that maintaining a diverse population of agents enables more comprehensive exploration of the preference landscape compared to single-agent approaches. Crucially, this diversity improves reward model learning by generating preference queries with clearly distinguishable behaviors, a key factor in real-world scenarios where humans must easily differentiate between options to provide meaningful feedback. Our experiments reveal that current methods may fail by getting stuck in local optima, requiring excessive feedback, or degrading significantly when human evaluators make errors on similar trajectories, a realistic scenario often overlooked by methods relying on perfect oracle teachers. Our population-based approach demonstrates robust performance when teachers mislabel similar trajectory segments and shows significantly enhanced preference exploration capabilities,particularly in environments with complex reward landscapes.
format Preprint
id arxiv_https___arxiv_org_abs_2506_13741
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle PB$^2$: Preference Space Exploration via Population-Based Methods in Preference-Based Reinforcement Learning
Driss, Brahim
Davey, Alex
Akrour, Riad
Artificial Intelligence
Machine Learning
Preference-based reinforcement learning (PbRL) has emerged as a promising approach for learning behaviors from human feedback without predefined reward functions. However, current PbRL methods face a critical challenge in effectively exploring the preference space, often converging prematurely to suboptimal policies that satisfy only a narrow subset of human preferences. In this work, we identify and address this preference exploration problem through population-based methods. We demonstrate that maintaining a diverse population of agents enables more comprehensive exploration of the preference landscape compared to single-agent approaches. Crucially, this diversity improves reward model learning by generating preference queries with clearly distinguishable behaviors, a key factor in real-world scenarios where humans must easily differentiate between options to provide meaningful feedback. Our experiments reveal that current methods may fail by getting stuck in local optima, requiring excessive feedback, or degrading significantly when human evaluators make errors on similar trajectories, a realistic scenario often overlooked by methods relying on perfect oracle teachers. Our population-based approach demonstrates robust performance when teachers mislabel similar trajectory segments and shows significantly enhanced preference exploration capabilities,particularly in environments with complex reward landscapes.
title PB$^2$: Preference Space Exploration via Population-Based Methods in Preference-Based Reinforcement Learning
topic Artificial Intelligence
Machine Learning
url https://arxiv.org/abs/2506.13741