Ability Transfer Through Language Mixing

Petr Hyner, Jan Mrógala, Jan Hula


Abstract
We systematically investigate cross-lingual ability transfer in language models through controlled experiments across three problem sets: algorithmic addition, graph navigation, and natural language modeling. Our experimental design creates high-resource and low-resource “language” pairs differing in vocabulary, grammar, and computational requirements. We show that training on mixed datasets consistently enables strong positive transfer, significantly improving low-resource language performance compared to training on low amount of data in isolation. We observe improvements from 0% to 100% accuracy in arithmetic tasks, from 24% to 98% accuracy in graph navigation tasks, and 69.6% perplexity reduction in natural language modeling. We demonstrate that transfer effectiveness depends on computational complexity and linguistic differences, where grammar modifications support stronger transfer than vocabulary modifications. These findings provide compelling evidence that cross-lingual ability transfer is a robust mechanism which contributes to the quality of large language models in low-resource languages.
Anthology ID:
2025.ijcnlp-long.76
Volume:
Proceedings of the 14th International Joint Conference on Natural Language Processing and the 4th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics
Month:
December
Year:
2025
Address:
Mumbai, India
Editors:
Kentaro Inui, Sakriani Sakti, Haofen Wang, Derek F. Wong, Pushpak Bhattacharyya, Biplab Banerjee, Asif Ekbal, Tanmoy Chakraborty, Dhirendra Pratap Singh
Venues:
IJCNLP | AACL
SIG:
Publisher:
The Asian Federation of Natural Language Processing and The Association for Computational Linguistics
Note:
Pages:
1374–1381
Language:
URL:
https://preview.aclanthology.org/ingest-ijcnlp-aacl/2025.ijcnlp-long.76/
DOI:
Bibkey:
Cite (ACL):
Petr Hyner, Jan Mrógala, and Jan Hula. 2025. Ability Transfer Through Language Mixing. In Proceedings of the 14th International Joint Conference on Natural Language Processing and the 4th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics, pages 1374–1381, Mumbai, India. The Asian Federation of Natural Language Processing and The Association for Computational Linguistics.
Cite (Informal):
Ability Transfer Through Language Mixing (Hyner et al., IJCNLP-AACL 2025)
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https://preview.aclanthology.org/ingest-ijcnlp-aacl/2025.ijcnlp-long.76.pdf