Building a Lightweight Classifier to Distinguish Closely Related Language Varieties with Limited Supervision: The Case of Catalan vs Valencian

Raúl García-Cerdá, María Miró Maestre, Miquel Canal


Abstract
Dialectal variation among closely related languages poses a major challenge in low-resource NLP, as their linguistic similarity increases confusability for automatic systems. We introduce the first supervised classifier to distinguish standard Catalan from its regional variety Valencian. Our lightweight approach fine-tunes a RoBERTa-base model on a manually curated corpus of 20 000 sentences—without any Valencian-specific tools—and achieves 98 % accuracy on unseen test data. In a human evaluation of 90 mixed-variety items per reviewer, acceptance rates reached 96.7 % for Valencian and 97.7 % for Catalan (97.2 % overall). We discuss limitations with out-of-distribution inputs and outline future work on confidence calibration and dialect-aware tokenization. Our findings demonstrate that high-impact dialect classification is feasible with minimal resources.
Anthology ID:
2025.lowresnlp-1.2
Volume:
Proceedings of the First Workshop on Advancing NLP for Low-Resource Languages
Month:
September
Year:
2025
Address:
Varna, Bulgaria
Editors:
Ernesto Luis Estevanell-Valladares, Alicia Picazo-Izquierdo, Tharindu Ranasinghe, Besik Mikaberidze, Simon Ostermann, Daniil Gurgurov, Philipp Mueller, Claudia Borg, Marián Šimko
Venues:
LowResNLP | WS
SIG:
Publisher:
INCOMA Ltd., Shoumen, Bulgaria
Note:
Pages:
7–11
Language:
URL:
https://preview.aclanthology.org/corrections-2026-01/2025.lowresnlp-1.2/
DOI:
Bibkey:
Cite (ACL):
Raúl García-Cerdá, María Miró Maestre, and Miquel Canal. 2025. Building a Lightweight Classifier to Distinguish Closely Related Language Varieties with Limited Supervision: The Case of Catalan vs Valencian. In Proceedings of the First Workshop on Advancing NLP for Low-Resource Languages, pages 7–11, Varna, Bulgaria. INCOMA Ltd., Shoumen, Bulgaria.
Cite (Informal):
Building a Lightweight Classifier to Distinguish Closely Related Language Varieties with Limited Supervision: The Case of Catalan vs Valencian (García-Cerdá et al., LowResNLP 2025)
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PDF:
https://preview.aclanthology.org/corrections-2026-01/2025.lowresnlp-1.2.pdf