Sebastian M\"oller
2026
Parallel Universes, Parallel Languages: A Comprehensive Study on LLM-based Multilingual Counterfactual Example Generation
Qianli Wang | Van Bach Nguyen | Yihong Liu | Fedor Splitt | Nils Feldhus | Christin Seifert | Hinrich Schuetze | Sebastian M\"oller | Vera Schmitt
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Qianli Wang | Van Bach Nguyen | Yihong Liu | Fedor Splitt | Nils Feldhus | Christin Seifert | Hinrich Schuetze | Sebastian M\"oller | Vera Schmitt
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Counterfactuals refer to minimally edited inputs that cause a model’s prediction to change, serving as a promising approach to explaining the model’s behavior. Large language models (LLMs) excel at generating English counterfactuals and demonstrate multilingual proficiency. However, their effectiveness in generating multilingual counterfactuals remains unclear. To this end, we conduct a comprehensive study on multilingual counterfactuals. We first conduct automatic evaluations on both directly generated counterfactuals in the target languages and those derived via English translation across six languages. Although translation-based counterfactuals offer higher validity than their directly generated counterparts, they demand substantially more modifications and still fall short of matching the quality of the original English counterfactuals. Second, we find the patterns of edits applied to high-resource European-language counterfactuals to be remarkably similar, suggesting that cross-lingual perturbations follow common strategic principles. Third, we reveal that multilingual counterfactual data augmentation (CDA) yields larger model performance improvements than cross-lingual CDA, especially for lower-resource languages. Yet, the imperfections of the generated counterfactuals limit gains in model performance and robustness. Finally, we identify and categorize four main types of errors that consistently appear in the generated counterfactuals across languages.
Fine-tuning with Hierarchical Prompting for Robust Propaganda Classification Across Annotation Schemas
Lukas St\"ahelin | Veronika Solopova | Max Upravitelev | David Kaplan | Premtim Sahitaj | Ariana Sahitaj | Charlott Jakob | Sebastian M\"oller | Vera Schmitt
Findings of the Association for Computational Linguistics: ACL 2026
Lukas St\"ahelin | Veronika Solopova | Max Upravitelev | David Kaplan | Premtim Sahitaj | Ariana Sahitaj | Charlott Jakob | Sebastian M\"oller | Vera Schmitt
Findings of the Association for Computational Linguistics: ACL 2026
Propaganda detection in social media is challenging due to noisy, short texts and low annotation agreements. We introduce a new intent-focused taxonomy of propaganda techniques and compare it against an established, higher-agreement schema. Along three dimensions (model portfolio, schema effects, and prompting strategy) we evaluate the taxonomies as a classification task with the help of four language models (GPT-4.1-nano, Phi-4 14B, Qwen2.5-14B, Qwen3-14B). Our results show that fine-tuning is essential, since it transforms weak zero-shot baselines into competitive systems and reveals methodological differences that are hidden using base models. Across schemas, the Qwen models achieve the strongest overall performance, and Phi-4 14B consistently outperforms GPT-4.1-nano. Our hierarchical prompting method (HiPP), which predicts fine-grained techniques before aggregating them, is especially beneficial after fine-tuning and on the more ambiguous, low-agreement taxonomy, while remaining competitive on the simpler schema. The HQP dataset, annotated with the new intent-based labels, provides a richer lens on propaganda’s strategic goals and a challenging benchmark for future work on robust, real-world detection.