Exploring Language-Agnosticity in Function Vectors: A Case Study in Machine Translation

Nurkhan Laiyk, Gerard I. Gállego, Javier Ferrando, Fajri Koto


Abstract
Function vectors (FVs) are vector representations of tasks extracted from model activations during in-context learning. While prior work has shown that multilingual model representations can be language-agnostic, it remains unclear whether the same holds for function vectors. We study whether FVs exhibit language-agnosticity, using word-level machine translation as a case study. Across three decoder-only multilingual LLMs, we find that translation FVs extracted from word-to-word prompts in a single English→X direction transfer to other target languages, consistently improving the rank of correct translation tokens across multiple unseen languages. We further find that the highest-gain tokens span multiple languages and that translation FVs across directions share most of their top-ranked heads, indicating that the FV encodes a largely language-agnostic translation signal.
Anthology ID:
2026.findings-emnlp.1126
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
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SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
23840–23851
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1126/
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Bibkey:
Cite (ACL):
Nurkhan Laiyk, Gerard I. Gállego, Javier Ferrando, and Fajri Koto. 2026. Exploring Language-Agnosticity in Function Vectors: A Case Study in Machine Translation. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 23840–23851, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Exploring Language-Agnosticity in Function Vectors: A Case Study in Machine Translation (Laiyk et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1126.pdf