Cross-lingual Functional Vectors for Emotion Detection in Large Language Models

Xue Jieying, Phuong Minh Nguyen, Le-Minh Nguyen, Shogo Okada


Abstract
Function vectors (FVs) have recently emerged as a promising mechanism for steering the behavior of large language models (LLMs) by injecting task-specific latent direction representations derived from in-context demonstrations. While prior studies have shown that FVs can recover task behavior in structured in-context learning settings, their effectiveness on semantically complex tasks and their ability to generalize across languages remain underexplored. We investigate the cross-lingual transferability of FVs using multilingual multi-label emotion recognition as a challenging semantic classification benchmark. Specifically, we examine whether FVs extracted from a source language can steer task behavior in another language under both standard clean and perturbed zero-shot settings without providing demonstrations during inference. Across diverse cross-lingual settings, applying FVs substantially improves performance, suggesting that FVs capture language-agnostic, task-relevant signals rather than purely language-specific lexical patterns, and highlighting their potential as a lightweight and transferable mechanism for multilingual task adaptation. We observe that each LLM exhibits a relatively stable optimal range of attention heads for constructing effective FVs, and the pattern remains consistent across languages. In addition, FVs can partially replicate the task-steering effects of standard few-shot in-context learning while avoiding the computational overhead of processing multiple demonstrations, making them effective for large-scale practical applications. Our code is available at https://github.com/yingjie7/cross_lingual_fvs.
Anthology ID:
2026.findings-emnlp.2030
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
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
43213–43225
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.2030/
DOI:
Bibkey:
Cite (ACL):
Xue Jieying, Phuong Minh Nguyen, Le-Minh Nguyen, and Shogo Okada. 2026. Cross-lingual Functional Vectors for Emotion Detection in Large Language Models. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 43213–43225, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Cross-lingual Functional Vectors for Emotion Detection in Large Language Models (Jieying et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.2030.pdf