Text Readability Assessment for Second Language Learners
Summary
The paper addresses automatic readability grading for learners of English as a second language. The main obstacle is that almost all level-annotated corpora target native-speaking children, and their levels reflect native criteria. The authors build a small CEFR-graded set of reading passages from Cambridge English Exams. They also clean the larger native WeeBit corpus and design a rich feature set: surface measures, lexico-semantic cues, EVP-based vocabulary features, GR-based syntactic complexity and language-model scores. Using linear SVMs, they then test how native data can support the scarce L2 data. They compare classification with pairwise ranking, learn a mapping from ranking scores to CEFR levels, apply EasyAdapt domain adaptation, and use self-training that treats native texts as unlabelled data. The best L2 result comes from self-training (ACC 0.797, PCC 0.938). A ranking model trained on native texts also transfers to unseen CEFR data much better than a native classifier. This matters for picking reading material for learners when graded learner data is scarce.
Key points
- Cambridge Exams dataset (released publicly). It contains reading passages from KET, PET, FCE, CAE and CPE, mapped to CEFR A2–C2, with 60–71 documents per level.
- Cleaned WeeBit corpus. The authors re-extracted WeeBit (Weekly Reader + BBC-Bitesize, five age-based levels) from raw HTML. They removed boilerplate such as copyright notices and links, because it correlated with the labels. The cleaned corpus keeps 529–1288 texts per level.
- In-domain results with a linear SVM. On native data the model reaches ACC 0.803 / PCC 0.900. On L2 data alone it reaches ACC 0.785 / PCC 0.924.
- Cross-domain transfer from native to L2 data.
- Applying the native classifier directly to L2 texts gives only ACC 0.233 / PCC 0.730.
- A native ranking model followed by a learned mapping to CEFR levels reaches ACC 0.622 / PCC 0.864.
- EasyAdapt with ranking improves this to ACC 0.707 / PCC 0.899, but still stays below training on L2 data only.
- Self-training. The best setting adds the 10 most confident native texts per round for 9 rounds (270 texts in total). The added texts go only to the three lowest L2 levels. This gives ACC 0.797 / PCC 0.938, a significant gain over L2-only training.
Interesting ideas
- I1. Check scraped corpora for label-leaking boilerplate. Page leftovers such as footers and links can track the source and therefore the label, which inflates scores. Re-extracting clean text is a cheap safeguard for any web-derived benchmark.
- I2. Rank first, then calibrate. Learning relative difficulty and then fitting a separate score-to-level mapping lets a model move between incompatible level scales. This could work wherever label schemes differ across sources, for example native vs. learner grades, or ratings from different annotators.
- I3. Build ranking pairs only within one domain. When pooling data with mismatched scales for domain adaptation, the authors form preference pairs only inside each domain. This avoids meaningless cross-scale comparisons while still sharing features through EasyAdapt.
- I4. Restrict self-training to the label range the unlabelled data covers. Adding pseudo-labelled native texts to all levels hurt performance. Limiting them to the lower levels, where children's texts plausibly overlap with learner levels, helped. The general lesson is to filter pseudo-labels by where the auxiliary data actually fits.
- I5. Treat graded language-exam materials as labelled data. Past exam papers are already professionally levelled. This makes them a ready-made source of difficulty labels for low-resource settings, such as building learner-oriented corpora for other languages.
Cited by
- Arabic Word-level Readability Visualization for Assisted Text Simplification
- Supervised and Unsupervised Neural Approaches to Text Readability
- CEFR-Cymraeg: A Dataset and Baseline Models for Language Proficiency Assessment in Welsh
Cite
@inproceedings{xia2016text,
title = {{Text Readability Assessment for Second Language Learners}},
author = {Xia, Menglin and Kochmar, Ekaterina and Briscoe, Ted},
booktitle = {Proceedings of the 11th Workshop on Innovative Use of NLP for Building Educational Applications},
year = {2016},
doi = {10.18653/v1/w16-0502},
url = {https://doi.org/10.18653/v1/w16-0502}
}References
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