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

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Main Authors: Laiyk, Nurkhan, Gállego, Gerard I., Ferrando, Javier, Koto, Fajri
Format: Preprint
Published: 2026
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author Laiyk, Nurkhan
Gállego, Gerard I.
Ferrando, Javier
Koto, Fajri
author_facet Laiyk, Nurkhan
Gállego, Gerard I.
Ferrando, Javier
Koto, Fajri
contents 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 machine translation as a case study. Across three decoder-only multilingual LLMs, we find that translation FVs extracted from a single English$\rightarrow$Target direction transfer to other target languages, consistently improving the rank of correct translation tokens across multiple unseen languages. Ablation results show that removing the FV degrades translation across languages with limited impact on unrelated tasks. We further show that base-model FVs transfer to instruction-tuned variants and partially generalize from word-level to sentence-level translation.
format Preprint
id arxiv_https___arxiv_org_abs_2604_19678
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Exploring Language-Agnosticity in Function Vectors: A Case Study in Machine Translation
Laiyk, Nurkhan
Gállego, Gerard I.
Ferrando, Javier
Koto, Fajri
Computation and Language
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 machine translation as a case study. Across three decoder-only multilingual LLMs, we find that translation FVs extracted from a single English$\rightarrow$Target direction transfer to other target languages, consistently improving the rank of correct translation tokens across multiple unseen languages. Ablation results show that removing the FV degrades translation across languages with limited impact on unrelated tasks. We further show that base-model FVs transfer to instruction-tuned variants and partially generalize from word-level to sentence-level translation.
title Exploring Language-Agnosticity in Function Vectors: A Case Study in Machine Translation
topic Computation and Language
url https://arxiv.org/abs/2604.19678