Role-Specific Strengths and Alignment in LLM Cross-Play and Self-Play

Kata Naszadi, Christof Monz


Abstract
Dialogue-game benchmarks usually pair a model with itself, and the resulting self-play score is treated as a measure of that model’s ability. We test whether self-play scores measure partner-independent ability by comparing them with cross-play evaluations. Across nine Clembench games, we evaluate every possible seating of three popular open-weight models. The cross-play reading exposes additional model strengths and weaknesses that are not detectable in self-play. In four of nine games, a mixed pair of two different models beats the best self-play score; in another four cases, a model does better paired with itself than paired with the strongest available partner. Looking at the transcripts, two mechanisms explain most of this: some pairs succeed because one partner writes more detailed messages that keep the interaction on track, while some self-play scores are inflated because both copies of a model make the same mistake and agree by accident.
Anthology ID:
2026.lmplayschool-1.4
Volume:
The Proceedings of Improving Language Models through Learning from Dialogue Game Interaction
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Alessandro Suglia, Mario Giulianelli, David Schlangen, Raffaella Bernardi, Raquel Fernández, Sherzod Hakimov, Sabrina McCallum, Davide Mazzaccara, Dieu-Thu Le, Oliver Lemon, Alexander Koller
Venues:
LM Playschool | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
41–48
Language:
URL:
https://aclanthology.org/2026.lmplayschool-1.4/
DOI:
Bibkey:
Cite (ACL):
Kata Naszadi and Christof Monz. 2026. Role-Specific Strengths and Alignment in LLM Cross-Play and Self-Play. In The Proceedings of Improving Language Models through Learning from Dialogue Game Interaction, pages 41–48, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Role-Specific Strengths and Alignment in LLM Cross-Play and Self-Play (Naszadi & Monz, LM Playschool 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.lmplayschool-1.4.pdf