Evaluating LLM-based Text Simplification for German: Effects on Post-Editing Effort, Quality Ratings, and User Comprehension

Luisa Carrer, Andreas Säuberli, Martin Kappus, Lukas Fischer, Sarah Ebling


Abstract
Automatic text simplification (ATS) seeks to automate the process of rewording within the same language to enhance readability and comprehension. Current evaluation practices for ATS systems predominantly rely on automatic metrics or assessments by experts and crowdworkers, often excluding the intended end users and other stakeholders, and thus limiting insights into the actual effectiveness of ATS models. In this study, we address this gap by conducting a multi-faceted, mixed-method evaluation of two LLM-based ATS systems for German (capito.ai and GPT-4o) and by involving end users, post-editors, and Easy Language experts. The findings highlight the effectiveness of the LLM-based ATS systems examined across several dimensions, including post-editing efficiency, expert quality assessments, and, in the case of GPT-4o-generated simplifications, user comprehension. Post-editing effort metrics, in particular, show an increase in productivity of around 30% compared to full manual simplification. Moreover, the results reveal substantial differences in perception and understanding among participant groups. These outcomes clearly indicate that ATS for German has recently made considerable progress and, crucially, underscore the importance of incorporating multiple stakeholders into ATS evaluation to better align system performance with accessibility goals.
Anthology ID:
2026.lrec-1.571
Volume:
Proceedings of the Fifteenth Language Resources and Evaluation Conference
Month:
May
Year:
2026
Address:
Palma de Mallorca, Spain
Editors:
Stelios Piperidis, Núria Bel, Henk van den Heuvel, Nancy Ide, Simon Krek, Antonio Toral
Venue:
LREC
SIG:
Publisher:
ELRA Language Resource Association
Note:
Pages:
7192–7208
Language:
External URL:
https://lrec.elra.info/lrec2026-main-571
DOI:
10.63317/3688akbpcnjn
Bibkey:
Cite (ACL):
Luisa Carrer, Andreas Säuberli, Martin Kappus, Lukas Fischer, and Sarah Ebling. 2026. Evaluating LLM-based Text Simplification for German: Effects on Post-Editing Effort, Quality Ratings, and User Comprehension. In Proceedings of the Fifteenth Language Resources and Evaluation Conference, pages 7192–7208, Palma de Mallorca, Spain. ELRA Language Resource Association.
Cite (Informal):
Evaluating LLM-based Text Simplification for German: Effects on Post-Editing Effort, Quality Ratings, and User Comprehension (Carrer et al., LREC 2026)
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