PalNLP at BAREC Shared Task 2025: Predicting Arabic Readability Using Ordinal Regression and K-Fold Ensemble Learning
Paper · 2025 · Mutaz Ayesh
Summary
The paper tackles sentence-level readability prediction for Arabic on BAREC, a corpus of over 69 thousand texts graded on a 19-level scale adapted from the Taha/Arabi21 framework. The author competed in the strict track, so no outside data was used. Because the levels are ordered, the system treats them as a continuous target rather than as independent classes. It starts from CAMeL-Lab's readability-arabertv2-d3tok-CE model, which was originally trained with cross-entropy, and refits it with a single regression output trained on MSE. Continuous scores become levels through cut-points tuned to maximize Quadratic Weighted Kappa (QWK). The official training and development data were pooled into 5 stratified folds, rare levels were oversampled, and the best model from each fold was combined into an ensemble. The system scored 81.1 QWK on the blind test, ranking 18th of 24 and just below the 81.5 baseline. Its ±1 accuracy was competitive, but its exact-level accuracy was weak. Error analysis traced many large mistakes to very short sentences and to diacritized text.
Key points
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Model and training. The base model is readability-arabertv2-d3tok-CE with a regression head. Training used MSE loss, AdamW, a 2e-5 learning rate, batch size 16, and inputs padded to 512 tokens. Training ran up to 6 epochs, with early stopping (patience 3) and a scheduler combining linear warmup with ReduceLROnPlateau keyed to validation QWK.
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Thresholds and class balance. Multi-pass grid coordinate descent tuned the class thresholds, giving roughly 1–2% over plain rounding. Rare levels were oversampled with PyTorch's WeightedRandomSampler using inverse-frequency weights.
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Internal results. Cross-validation QWK stayed between about 79.85 and 80.21, and the provided test set reached 77.7. When diacritics were removed with PyArabic's strip_diacritics, the test set rose to 81.25 QWK. Exact accuracy went from 29.99% to 34.37%, ±1 accuracy from 65.88% to 69.48%, and the worst-error range narrowed from (-15, 12) to (-11, 8).
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Blind test versus baseline.
Metric PalNLP Baseline QWK 81.1 81.5 Exact accuracy 33.1% 58.1% ±1 accuracy 69.8% 72.0% 3-class accuracy 72.5% 76.5% The gap to the baseline shrinks steadily as the label scale gets coarser.
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Error analysis. The author examined the 100 most-wrong predictions, 50 in each direction. Among underestimated items, 94% had fewer than 5 words, and many came from specialized sources such as the Emirati curriculum and the Quran. In one case, a diacritized proper name with gold level 3 was predicted as level 15.
Interesting ideas
- I1. Fitting an ordered label as a regression score and then learning per-class cut-points by coordinate descent on the target metric beats simple rounding at no extra model cost.
- I2. Reporting exact, ±1, and collapsed 7/5/3-class accuracy side by side shows whether a model knows the broad picture but fails at fine distinctions.
- I3. Inspecting the worst errors separately for over- and under-estimation exposed a superficial cue: diacritics made texts look hard. Removing that cue at inference gave a large gain.
- I4. Each fold keeps its own tuned thresholds, and fold models are ensembled after their own calibration rather than with one global set of cut-points.
- I5. When the official dev split stops being informative, pooling train and dev into stratified k-folds gives steadier model selection, though results become less comparable with others.
For Mova
How these ideas could serve Mova, our small open language model — its files, stages and tests:
- I1 (answer): A school-course reader could grade passages or questions on an ordered difficulty scale this way, tuning the cut-points on held-out tests instead of rounding.
- I2 (learn): Evaluation of ordinal outputs, such as confidence tiers or level estimates, could always include coarsened views to locate where errors actually live.
- I3 (learn): Mova could add negative controls that strip or perturb surface marks (casing, quotes, punctuation) to check that decisions rest on structure, not orthographic noise.
- I4 (learn): When several witness models are trained on different splits, calibrating each one separately before voting may produce cleaner silver labels.
- I5 (tree): Small English treebanks for gparse could use stratified folds for checkpoint selection, while keeping the official test split untouched for honest reporting.
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 Mutaz Ayesh. 2025. PalNLP at BAREC Shared Task 2025: Predicting Arabic Readability Using Ordinal Regression and K-Fold Ensemble Learning. Proceedings of The Third Arabic Natural Language Processing Conference: Shared Tasks.
@inproceedings{ayesh2025palnlp,
title = {{PalNLP at BAREC Shared Task 2025: Predicting Arabic Readability Using Ordinal Regression and K-Fold Ensemble Learning}},
author = {Mutaz Ayesh},
booktitle = {Proceedings of The Third Arabic Natural Language Processing Conference: Shared Tasks},
year = {2025},
doi = {10.18653/v1/2025.arabicnlp-sharedtasks.47},
url = {https://doi.org/10.18653/v1/2025.arabicnlp-sharedtasks.47}
}References
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