PsyBer-Agent: A Psychology-Driven User Agent for Recommender Systems

Hugging Face Daily Papers Papers

Summary

The paper proposes PsyBer-Agent, a psychology-inspired LLM user simulator for recommender systems that models evolving latent states like fatigue and shifting preferences, calibrated via Unbalanced Gromov-Wasserstein optimal transport, along with the WebSim platform and PsyBer Benchmark for evaluating behavioral fidelity at scale.

Evaluating recommender systems before deployment requires simulators that remain realistic over long, closed-loop interaction cycles. Current LLM-based agents generally function as surface imitators that generate realistic short-term responses but fail to capture the underlying user dynamics such as fatigue, affect, and shifting preferences. We propose PsyBer-Agent, a psychology-inspired simulator that models these dynamics through its Psy-Engine. This engine represents each user with three evolving, model-defined latent states. To calibrate simulated behavior against real interaction logs, we align log-conditioned reference trajectories with simulator-generated latent-state trajectories via Unbalanced Gromov--Wasserstein optimal transport. This approach provides structured supervision for a lightweight policy without the computational burden of fine-tuning the backbone LLM. We also introduce WebSim and the PsyBer Benchmark, which encompass multimodal scenarios and seven recommender backbones. Our framework evaluates behavioral fidelity, latent-state consistency, robustness, and responses to social-cue perturbations. On the tested horizons, PsyBer-Agent shows lower behavioral discrepancy than the prompt-only simulators while maintaining stable performance under large-scale concurrent simulation for up to 5M queued simulation tasks under bounded concurrency. Code is available in the supplementary material and at: PsyBer-Agent: https://anonymous.4open.science/r/CC66F/, WebSim Platform: https://anonymous.4open.science/r/D8EAX/.
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Source: https://huggingface.co/papers/2610.13989

Abstract

Evaluatingrecommendersystemsbeforedeploymentrequiressimulatorsthatremainrealisticoverlong,closed-loopinteractioncycles.CurrentLLM-basedagentsgenerallyfunctionassurfaceimitatorsthatgeneraterealisticshort-termresponsesbutfailtocapturetheunderlyinguserdynamicssuchasfatigue,affect,andshiftingpreferences.WeproposePsyBer-Agent,apsychology-inspiredsimulatorthatmodelsthesedynamicsthroughitsPsy-Engine.Thisenginerepresentseachuserwiththreeevolving,model-definedlatentstates.Tocalibratesimulatedbehavioragainstrealinteractionlogs,wealignlog-conditionedreferencetrajectorieswithsimulator-generatedlatent-statetrajectoriesviaUnbalancedGromov--Wassersteinoptimaltransport.Thisapproachprovidesstructuredsupervisionforalightweightpolicywithoutthecomputationalburdenoffine-tuningthebackboneLLM.WealsointroduceWebSimandthePsyBerBenchmark,whichencompassmultimodalscenariosandsevenrecommenderbackbones.Ourframeworkevaluatesbehavioralfidelity,latent-stateconsistency,robustness,andresponsestosocial-cueperturbations.Onthetestedhorizons,PsyBer-Agentshowslowerbehavioraldiscrepancythantheprompt-onlysimulatorswhilemaintainingstableperformanceunderlarge-scaleconcurrentsimulationforupto5Mqueuedsimulationtasksunderboundedconcurrency.Codeisavailableinthesupplementarymaterialandat:PsyBer-Agent:https://anonymous.4open.science/r/CC66F/,WebSimPlatform:https://anonymous.4open.science/r/D8EAX/.

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