Identifying and Mitigating Bottlenecks in Role-Playing Agents: A Systematic Study of Disentangling Character Profile Axes

Yonghyun Jun, Junhyuk Choi, Jeonghyun Park, Jihyeong Park, Nicole Geumheon Liu, Hwanhee Lee


Abstract
While Large Language Model (LLM) role-playing agents have advanced rapidly, it remains unclear which profile elements genuinely drive role-playing quality. To bridge this gap, we introduce a systematic diagnostic framework that disentangles the impact of character profiles along three axes: Familiarity (Known vs. Unknown), Structure (Structured vs. Unstructured), and Disposition (Moral vs. Immoral). Utilizing a unified hierarchical schema (5 dimensions, 28 fields), we construct a controlled dataset of 211 personas and evaluate five LLMs on both single- and multi-turn interactions. Our results reveal a striking asymmetry: Familiarity and Structure show negligible impact, while Disposition produces large, consistent performance degradation for immoral characters across all conditions. Further analyses suggest that the Moral–Immoral gap is amplified by post-SFT alignment, and that this degradation varies substantially across profile attributes. To mitigate this bottleneck, we propose Field-Aware Contrastive Decoding (FACD), a training-free strategy that amplifies suppressed disposition-sensitive signals, significantly closing the performance gap without sacrificing moral-character performance.
Anthology ID:
2026.emnlp-main.1590
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
36152–36182
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1590/
DOI:
Bibkey:
Cite (ACL):
Yonghyun Jun, Junhyuk Choi, Jeonghyun Park, Jihyeong Park, Nicole Geumheon Liu, and Hwanhee Lee. 2026. Identifying and Mitigating Bottlenecks in Role-Playing Agents: A Systematic Study of Disentangling Character Profile Axes. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 36152–36182, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Identifying and Mitigating Bottlenecks in Role-Playing Agents: A Systematic Study of Disentangling Character Profile Axes (Jun et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1590.pdf