When English Isn’t the Best Teacher: Source Language Effects in Cross-Lingual In-Context Learning

Fred Philippy, Siwen Guo, Jacques Klein, Tegawendé F. Bissyandé


Abstract
Cross-lingual transfer in multilingual NLP has been widely explored in supervised fine-tuning contexts, where factors like data availability and linguistic similarity largely determine transfer quality. As the field shifts toward few-shot In-Context Learning (ICL), it is often presumed that insights from fine-tuning carry over unchanged. Yet this assumption has not been rigorously evaluated, leaving open the question of how to choose source languages for cross-lingual ICL. We conduct a broad empirical study of cross-lingual transfer in ICL spanning seven tasks, six models, and a typologically diverse set of languages. We further analyze language confusion, a key obstacle for generative tasks in cross-lingual ICL. Our results show that conventional fine-tuning-based expectations do not consistently apply in the ICL regime and point to alternative heuristics for selecting source languages effectively..
Anthology ID:
2026.mellm-1.31
Volume:
Proceedings of the 1st Workshop on Multilinguality in the Era of Large Language Models (MeLLM 2026)
Month:
July
Year:
2026
Address:
San Diego, United States
Editors:
Kaiyu Huang, Fengran Mo, Pinzhen Chen, Meng Jiang
Venues:
MeLLM | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
317–326
Language:
URL:
https://preview.aclanthology.org/ingest-acl-workshops/2026.mellm-1.31/
DOI:
Bibkey:
Cite (ACL):
Fred Philippy, Siwen Guo, Jacques Klein, and Tegawendé F. Bissyandé. 2026. When English Isn’t the Best Teacher: Source Language Effects in Cross-Lingual In-Context Learning. In Proceedings of the 1st Workshop on Multilinguality in the Era of Large Language Models (MeLLM 2026), pages 317–326, San Diego, United States. Association for Computational Linguistics.
Cite (Informal):
When English Isn’t the Best Teacher: Source Language Effects in Cross-Lingual In-Context Learning (Philippy et al., MeLLM 2026)
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PDF:
https://preview.aclanthology.org/ingest-acl-workshops/2026.mellm-1.31.pdf