Evaluation of Multilingual Text Simplification for the Mental Health Domain: Exploring Small Language Models
Summary
The paper looks at how to judge automatic simplification of mental health texts in languages other than English, where such work is scarce. The authors took five ICD-11 articles on primary psychotic disorders (6A20–6A24, with sub-definitions) and simplified them in English, German and French. They used nine small models: LingConv, PRISM, six Ascle variants and a quantized BioMistral 7B that was prompted to rewrite the text for laypeople. Rather than relying on similarity scores like BLEU, ROUGE and BERTScore, which barely separated good from bad outputs, they measured how much lexical complexity and readability changed between the source and each output. Manual inspection of the English results, plus a small human ranking of BioMistral runs, showed that MTLD and FRE together were the most informative pair. Only BioMistral produced usable simplifications, and only in English. German and French outputs stayed dense or contained grammatical errors. The authors call the study preliminary but suggest that the combined MTLD/FRE shift could serve as a cheap language-agnostic check before human review.
Key points
- Data: ICD-11 definitions 6A20–6A24, retrieved via the ICD API. Models: LingConv (T5-Base), PRISM (39 languages), Ascle (BigBird-Pegasus Large, BART Large and BioBART v2 Base, each in two fine-tuned versions) and BioMistral 7B SLERP with 4-bit GPTQ.
- Metrics: 3 lexical complexity measures (TTR, MATTR, MTLD) and 9 readability indices (FRE, FKGL, ARI, SMOG, Fog, CLI, DCR, LIX, RIX), computed with textstat and LexicalRichness. Each was scored as a difference between the original and the simplified text, which makes cross-language comparison easier.
- Interpreting the two key metrics:
- Good simplifications raised both MTLD and FRE.
- A rise in MTLD combined with a drop in FRE signals overly dense text.
- A drop in MTLD signals repetitive wording.
- Human check: Three annotators ranked 10 BioMistral runs on English 6A20, with low agreement (Cohen's κ ≈ 0).
- The best runs (8, 9) had moderate MTLD gains of about 27–37.
- The worst runs had extreme gains: 82 for run 1 and 8 for run 5.
- Multilingual results: PRISM produced no German or French paraphrases. Code is released at github.com/uit-hdl/multilingual-text-simplification-icd-11.
Cite
@inproceedings{pelloni2026evaluation,
title = {{Evaluation of Multilingual Text Simplification for the Mental Health Domain: Exploring Small Language Models}},
author = {Pelloni, Olga and Just, Sandra and Bongo, Lars},
booktitle = {BioNLP 2026},
year = {2026},
doi = {10.18653/v1/2026.bionlp-1.36},
url = {https://doi.org/10.18653/v1/2026.bionlp-1.36}
}References
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