The Curse of Multilinguality in Lexical Normalization

Saman Rahbar


Abstract
Lexical normalization rewrites the noisy, nonstandard words that fill user-generated text (tmrw, u, gr8) into their standard forms. Because labelled data is scarce for most languages, a popular shortcut is to train a single model on many languages at once. We ask a simple question: how many languages should such a model be trained on? Using one fixed-capacity character-level model and twelve languages from a standard benchmark, we vary the number of jointly trained languages from one to twelve and measure per-language accuracy. We find a clear curse of multilinguality: accuracy is highest when a language is trained with only a few others, often just one to four, and then falls steadily and substantially, dropping by about forty percent as the rest are piled on. A control that holds the total amount of training data constant makes the decline arrive sooner and fall further, which points to competition among the languages for one fixed-size model rather than to how much data is available. We also test whether a language’s typological distance from the others predicts its ideal number of cotraining languages, and find no dependable rule: any apparent relationship rests on a couple of languages and does not hold up. For compact normalization models, less can be more: a few languages beat pooling everything into a single model.
Anthology ID:
2026.wnut-1.22
Volume:
Proceedings of the 11th Workshop on Natural User-generated Text
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
JinYeong Bak, Rob van der Goot, Hyeju Jang, Weerayut Buaphet, Alan Ramponi, Wei Xu, Alan Ritter
Venues:
WNUT | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
325–331
Language:
URL:
https://aclanthology.org/2026.wnut-1.22/
DOI:
Bibkey:
Cite (ACL):
Saman Rahbar. 2026. The Curse of Multilinguality in Lexical Normalization. In Proceedings of the 11th Workshop on Natural User-generated Text, pages 325–331, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
The Curse of Multilinguality in Lexical Normalization (Rahbar, WNUT 2026)
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PDF:
https://aclanthology.org/2026.wnut-1.22.pdf