VIB-Simp: IB-Inspired Output-Logit Regularization for German Text Simplification

Mofan Duan, Yanyan Yang, Xiufeng Liu


Abstract
German text simplification requires reducing lexical and structural complexity while preserving meaning, yet standard fine-tuning optimizes reference imitation without directly controlling the predictive distribution where lexical choices are made. We propose VIB-Simp, a lightweight output-logit regularization framework inspired by the Variational Information Bottleneck (VIB) literature. Instead of estimating mutual information or adding latent variables, VIB-Simp regularizes the mean and variance of output logits using a closed-form Gaussian Kullback–Leibler (KL) surrogate, providing a lightweight way to stabilize lexical choices during fine-tuning. An optional unlikelihood-style lexical penalty further suppresses probability mass assigned to difficult lexical candidates.

Experiments on TextComplexityDE and 20Min show consistent gains across LLaMA-3.2-3B, Qwen-2.5-3B, mBART, GerPT-2, and mGPT, with consistent SARI improvements. Additional baselines, length-controlled analysis, ablations, expert ratings, and logit diagnostics show that the gains are not explained by shortening or dictionary-only effects. The results support an IB-style view of simplification: preserve meaning-critical content while suppressing unnecessary lexical complexity.
Anthology ID:
2026.emnlp-main.710
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
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SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
16483–16495
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URL:
https://aclanthology.org/2026.emnlp-main.710/
DOI:
Bibkey:
Cite (ACL):
Mofan Duan, Yanyan Yang, and Xiufeng Liu. 2026. VIB-Simp: IB-Inspired Output-Logit Regularization for German Text Simplification. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 16483–16495, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
VIB-Simp: IB-Inspired Output-Logit Regularization for German Text Simplification (Duan et al., EMNLP 2026)
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https://aclanthology.org/2026.emnlp-main.710.pdf