When Does Auxiliary Classification Help Regression in Practice? A Case Study in Arabic Dialectness Modeling

Abdelrahman Sakr, Marwan Torki, Nagwa El-Makky


Abstract
Estimating the Arabic Level of Dialectness (ALDi) is a continuous regression task that quantifies how much a sentence diverges from Modern Standard Arabic (MSA). While auxiliary classification is often used to support regression, its effectiveness depends critically on how the auxiliary task is designed. We conduct a systematic study of auxiliary classification for ALDi estimation, showing that naive auxiliary supervision can degrade regression performance under skewed target distributions. We identify two key factors that determine when auxiliary tasks become beneficial: the granularity of discretization and the choice of loss function. Specifically, 7-bin discretization combined with focal loss substantially improves performance. Our approach achieves an RMSE of 0.1275 on the NADI 2024 blind test set, outperforming previous systems by over 9%, and the same design transfers to English toxicity regression. Detailed error analysis reveals how auxiliary classification reshapes model behavior across the Arabic dialect spectrum. We release our code and model predictions to facilitate future research
Anthology ID:
2026.emnlp-main.30
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
639–649
Language:
URL:
https://aclanthology.org/2026.emnlp-main.30/
DOI:
Bibkey:
Cite (ACL):
Abdelrahman Sakr, Marwan Torki, and Nagwa El-Makky. 2026. When Does Auxiliary Classification Help Regression in Practice? A Case Study in Arabic Dialectness Modeling. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 639–649, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
When Does Auxiliary Classification Help Regression in Practice? A Case Study in Arabic Dialectness Modeling (Sakr et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.30.pdf