DUTH at SemEval-2026 Task 9: Joint Multilingual Fine-Tuning for Online Polarization Detection

Georgios Arampatzis, Avi Arampatzis


Abstract
Online polarization on social media presentssubstantial challenges for public discourse, content moderation, and large-scale social analytics across diverse linguistic and cultural contexts. A recent multilingual benchmark enablessystematic evaluation of polarization detectionacross 22 languages and multiple sociopoliticalevents, providing a unified setting for studying socially grounded NLP under multilingualconditions.Wepresent DUTH, a unified multilingual system for binary polarization detection based onjoint fine-tuning of XLM-RoBERTa on the 22languages of SemEval-2026 Task 9 Subtask1. Our system uses a single shared encoderwith a linear classification head and is trainedjointly on the multilingual training set usingmixed-precision optimization. On the officialevaluation, the system achieved an average Accuracy of 0.822 and an average Macro-F1 of0.780 across 22 languages. The results showthat a simple jointly fine-tuned multilingualtransformer provides a competitive and scalable baseline for online polarization detection,while still facing difficulties in implicit, sarcastic, and culturally grounded cases.
Anthology ID:
2026.semeval-1.86
Volume:
Proceedings of the 20th International Workshop on Semantic Evaluation (2026)
Month:
July
Year:
2026
Address:
San Diego, California, USA
Editors:
Ekaterina Kochmar, Debanjan Ghosh, Kai North, Mamoru Komachi
Venues:
SemEval | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
599–604
Language:
URL:
https://preview.aclanthology.org/ingest-acl-workshops/2026.semeval-1.86/
DOI:
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Cite (ACL):
Georgios Arampatzis and Avi Arampatzis. 2026. DUTH at SemEval-2026 Task 9: Joint Multilingual Fine-Tuning for Online Polarization Detection. In Proceedings of the 20th International Workshop on Semantic Evaluation (2026), pages 599–604, San Diego, California, USA. Association for Computational Linguistics.
Cite (Informal):
DUTH at SemEval-2026 Task 9: Joint Multilingual Fine-Tuning for Online Polarization Detection (Arampatzis & Arampatzis, SemEval 2026)
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PDF:
https://preview.aclanthology.org/ingest-acl-workshops/2026.semeval-1.86.pdf
Supplementarymaterial:
 2026.semeval-1.86.SupplementaryMaterial.zip