Behaviorally Grounded User Profiles from the Wild for Personalized Alignment and Multi-Perspective Reasoning

Yuxuan Li, Victor Zhong, Ehsan Kamalloo


Abstract
Persona-driven techniques increasingly adapt large language models (LLMs) to diverse contexts. However, existing methods predominantly rely on rigid, synthetic personas that flatten individual variation, rely on stereotypes, and miss the nuanced signals driving actual human preferences. We introduce profile behavioral grounding, a framework for extracting open-ended, high-fidelity user profiles directly from authentic, anonymized social media posts. We evaluate these profiles across two paradigms: train-time personalization via supervised fine-tuning (SFT) and non-parametric test-time multi-perspective reasoning. Across complex recommendation and open-ended query benchmarks, behaviorally grounded profiles consistently improve base models and outperform synthetic profile baselines, driving stronger parametric alignment and enabling richer, multifaceted reasoning. Our findings establish open-ended, behavior-derived profiles as a highly diverse and effective foundation for the next generation of personalized language systems.
Anthology ID:
2026.findings-aacl.201
Volume:
Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
4003–4024
Language:
URL:
https://aclanthology.org/2026.findings-aacl.201/
DOI:
Bibkey:
Cite (ACL):
Yuxuan Li, Victor Zhong, and Ehsan Kamalloo. 2026. Behaviorally Grounded User Profiles from the Wild for Personalized Alignment and Multi-Perspective Reasoning. In Findings of the Association for Computational Linguistics: IJCNLP-AACL 2026, pages 4003–4024, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
Behaviorally Grounded User Profiles from the Wild for Personalized Alignment and Multi-Perspective Reasoning (Li et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-aacl.201.pdf