TounsiBench: Benchmarking Large Language Models for Tunisian Arabic
Paper · 2025 · Souha Ben Hassine, Asma Arrak, Marouene Addhoum et al.
Summary
Tunisian Arabic (Derja) is spoken by more than 12 million people. It differs strongly from MSA, borrows heavily from French, Italian, Turkish and Berber, and has no fixed spelling. Until this paper, nobody had systematically checked how well chat LLMs handle it.
The authors built a set of 744 Tunisian Arabic instructions. Some were collected from native speakers describing how they would actually query a chatbot. The rest were rendered into Derja from an existing English instruction set. Native-speaker authors also wrote a reference answer for every item. Ten Arabic-capable LLMs were told to answer strictly in Tunisian Arabic. Their outputs were then compared in pairs by human annotators and by LLM judges on four axes: quality, correctness, relevance and dialectal adherence. GPT-4o tracked human preferences most closely, so it was adopted as the automatic judge for the final leaderboard.
The central finding is that most models fail to recognise the dialect or to stay within it. Data, gold answers and evaluation code are public, so other teams can test their own models.
Key points
- Dataset composition: 744 instructions in total.
- 417 were crowdsourced from 48 native speakers (32 female, 16 male, aged 15–48, from various regions).
- 327 were translated from the HuggingFace Helpful Instructions dataset.
- Every item carries topic labels and a human-written gold response.
- Models tested: GPT-4o, GPT-4o-mini, GPT-4, GPT-3.5 Turbo, LLaMA-3.3-70B, LLaMA-3.1-8B-Instruct, Aya-23-8B, jais-13B-chat, SILMA-9B-Instruct-v1.0 and Mixtral-8x7B-Instruct-v0.1.
- Evaluation design: all 45 possible model pairs were compared, giving 900 pairwise evaluation instances. The order of the two responses was randomised to counter position bias.
- Length bias:
- Humans chose the longer answer 45% of the time.
- Among LLM judges, the rate ranged from 47% (Aya-23-8B) and 64% (GPT-4o) up to 75% (Mixtral).
- Yet GPT-4o's rankings correlated only weakly with average response length (Spearman 0.42 for quality down to 0.115 for Tunisian usage).
- Other judge and model failures:
- Models picked their own outputs more often than humans did. The gap was largest for Mixtral (78 vs 29) and LLaMA-3.1-8B (94 vs 46).
- Annotators flagged Mixtral 30 times out of 180 for answers that were not in Arabic at all.
Interesting ideas
- I1. Before trusting an automatic judge at scale, the authors scored several candidate judges against human ratings and kept the one that agreed best; this turns "which judge?" into a measured choice rather than an assumption.
- I2. A self-preference audit compares how often a model picks its own output with how often humans pick it, exposing judges that reward their own style.
- I3. Length bias was checked in two ways: the share of "longer wins" per judge, and the correlation between final rankings and mean response length.
- I4. Language/dialect adherence was scored as its own criterion, separate from correctness and relevance, so a factually right answer in the wrong variety still loses points.
- I5. The benchmark mixes genuinely user-written queries with adapted items from an existing dataset, balancing realism against coverage.
For Mova
How these ideas could serve Mova, our small open language model — its files, stages and tests:
- I1 (learn): Each LLM teacher tier could be certified by its agreement with a small hand-checked gold set before its labels are allowed into training data.
- I2 (learn): When witness parsers vote on silver trees, we could measure whether any witness systematically backs analyses identical to its own output and down-weight it.
- I3 (answer): When grading Mova's readers on school tests or fable QA, a length-only baseline could serve as a negative control, ensuring verbose answers are not mistaken for better ones.
- I4 (back): Generation from the meaning graph could be scored separately on content fidelity and on register or style, revealing cases where facts survive but the wording drifts.
- I5 (answer): Test sets for the readers could combine naturally phrased questions from real users with converted standard items, catching failures that clean curated questions hide.
Institutions
Fields, topics and concepts
📚 Shelves 4The field of science this work belongs to (OpenAlex fields).Computer Science · 18,614 worksArtificial Intelligence · 17,965 worksArts and Humanities · 17,450 worksLanguage and Linguistics · 17,296 works
🧭 Topics 1Research subjects and languages the work is about.Semitic languages · 3,066 works
Cite
Cite as Souha Ben Hassine, Asma Arrak, Marouene Addhoum and Steven R. Wilson. 2025. TounsiBench: Benchmarking Large Language Models for Tunisian Arabic. Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing.
@inproceedings{hassine2025tounsibench,
title = {{TounsiBench: Benchmarking Large Language Models for Tunisian Arabic}},
author = {Souha Ben Hassine, Asma Arrak, Marouene Addhoum and Steven R. Wilson},
booktitle = {Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing},
year = {2025},
doi = {10.18653/v1/2025.emnlp-main.1756},
url = {https://doi.org/10.18653/v1/2025.emnlp-main.1756}
}References
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