Limited-Resource Adapters Are Regularizers, Not Linguists

Marcell Fekete, Nathaniel Romney Robinson, Ernests Lavrinovics, Djeride Jean-Baptiste, Raj Dabre, Johannes Bjerva, Heather Lent


Abstract
Cross-lingual transfer from related high-resource languages is a well-established strategy to enhance low-resource language technologies. Prior work has shown that adapters show promise for, e.g., improving low-resource machine translation (MT). In this work, we investigate an adapter souping method combined with cross-attention fine-tuning of a pre-trained MT model to leverage language transfer for three low-resource Creole languages, which exhibit relatedness to different language groups across distinct linguistic dimensions. Our approach improves performance substantially over baselines. However, we find that linguistic relatedness—or even a lack thereof—does not covary meaningfully with adapter performance. Surprisingly, our cross-attention fine-tuning approach appears equally effective with randomly initialized adapters, implying that the benefit of adapters in this setting lies in parameter regularization, and not in meaningful information transfer. We provide analysis supporting this regularization hypothesis. Our findings underscore the reality that neural language processing involves many success factors, and that not all neural methods leverage linguistic knowledge in intuitive ways.
Anthology ID:
2025.acl-short.19
Volume:
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers)
Month:
July
Year:
2025
Address:
Vienna, Austria
Editors:
Wanxiang Che, Joyce Nabende, Ekaterina Shutova, Mohammad Taher Pilehvar
Venue:
ACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
222–237
Language:
URL:
https://preview.aclanthology.org/ingestion-acl-25/2025.acl-short.19/
DOI:
Bibkey:
Cite (ACL):
Marcell Fekete, Nathaniel Romney Robinson, Ernests Lavrinovics, Djeride Jean-Baptiste, Raj Dabre, Johannes Bjerva, and Heather Lent. 2025. Limited-Resource Adapters Are Regularizers, Not Linguists. In Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 2: Short Papers), pages 222–237, Vienna, Austria. Association for Computational Linguistics.
Cite (Informal):
Limited-Resource Adapters Are Regularizers, Not Linguists (Fekete et al., ACL 2025)
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PDF:
https://preview.aclanthology.org/ingestion-acl-25/2025.acl-short.19.pdf