Some Dialects are More Equal than Others: Non-Prestigious Arabic Dialectal Bias in LLMs

Mai Mohamed Eida, Ryan Dolan, Paul de Nijs, Jonathan Dunn


Abstract
Previous work on Egyptian Arabic in NLP has focused largely on the prestigious Cairene Egyptian Arabic (CEA) dialect, resulting in a lack of representation for the less prestigious Sa’idi Egyptian Arabic (SEA) dialect both in LLM and resource development. Does this lack of representation influence an LLM’s view of the acceptability of SEA (upstream), and does an upstream bias against SEA lead to worse performance (downstream)? We investigate the upstream effect of SEA dialectal features on LLM preferences in a Targeted Syntactic Evaluation (TSE) task which reveals a significant bias against SEA across multiple LLMs. We then analyze the effect of these same features on downstream model performance on MMLU benchmarks and show that models frequently experience a degradation in performance when presented with SEA. This work highlights the need for further exploration on how sub-dialectal variation impacts language technologies.
Anthology ID:
2026.arabicnlp-main.5
Volume:
Proceedings of The Fourth Arabic Natural Language Processing Conference
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Muhammad Abdul-Mageed, Tamer Elsayed, Houda Bouamor, Samhaa El-Beltagy, Hend Al-Khalifa, Ahmed Abdelali, AbdelRahim Elmadany, Abdellah El Mekki, Kareem Darwish, Sakhar Alkhereyf, Hamzah Luqman, Salam Khalifa, Samar Magdy, Zaid Alyafeai, Injy Hamed, Wajdi Zaghouani, Imed Zitouni
Venue:
ArabicNLP
SIG:
SIGARAB
Publisher:
Association for Computational Linguistics
Note:
Pages:
48–64
Language:
URL:
https://aclanthology.org/2026.arabicnlp-main.5/
DOI:
Bibkey:
Cite (ACL):
Mai Mohamed Eida, Ryan Dolan, Paul de Nijs, and Jonathan Dunn. 2026. Some Dialects are More Equal than Others: Non-Prestigious Arabic Dialectal Bias in LLMs. In Proceedings of The Fourth Arabic Natural Language Processing Conference, pages 48–64, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Some Dialects are More Equal than Others: Non-Prestigious Arabic Dialectal Bias in LLMs (Eida et al., ArabicNLP 2026)
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PDF:
https://aclanthology.org/2026.arabicnlp-main.5.pdf