The Language of Bargaining: Linguistic Effects in LLM Negotiations

Stuti Sinha, Himanshu Kumar, Aryan Raju Mandapati, Rakshit Sakhuja, Dhruv Kumar


Abstract
Negotiation is a core component of social intelligence, requiring agents to balance strategic reasoning, cooperation, and social norms. Recent work shows that LLMs can engage in multi-turn negotiation, yet nearly all evaluations occur exclusively in English. We systematically isolate language effects across English and three Indic framings (Hindi, Punjabi, Gujarati) by holding game rules, model parameters, and incentives constant for multi-agent simulations for Ultimatum, Buy-Sell, and Resource Exchange games. Our results indicate that language choice is correlated to agreement and process dynamics, while final payoffs are statistically unchanged, and that this correlation persists across model architectures. Crucially, effects are task-contingent: Indic languages lower acceptance and longer negotiations in the Ultimatum Game, and higher trade volume in Resource Exchange. Further, they suggest that findings obtained under English-only conditions may not generalize to other linguistic settings. Even within one related language family, we observe task-contingent divergence from English, which cautions against treating English-only evaluation as representative. Whether this extends to typologically distant languages remains open.
Anthology ID:
2026.aacl-long.51
Volume:
Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venues:
AACL | IJCNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1064–1088
Language:
URL:
https://aclanthology.org/2026.aacl-long.51/
DOI:
Bibkey:
Cite (ACL):
Stuti Sinha, Himanshu Kumar, Aryan Raju Mandapati, Rakshit Sakhuja, and Dhruv Kumar. 2026. The Language of Bargaining: Linguistic Effects in LLM Negotiations. In Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 1: Long Papers), pages 1064–1088, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
The Language of Bargaining: Linguistic Effects in LLM Negotiations (Sinha et al., AACL-IJCNLP 2026)
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PDF:
https://aclanthology.org/2026.aacl-long.51.pdf