Linguistic Cues for LLM-based Implicit Discourse Relation Classification

Yi Fan, Michael Strube, Wei Liu


Abstract
Large language models (LLMs) have achieved impressive success across many NLP tasks, yet implicit discourse relation classification (IDRC) is still dominated by encoder-only pre-trained language models such as RoBERTa. This may be due to earlier reports that ChatGPT performs poorly on IDRC in zero-shot settings. In this paper, we show that fine-tuned LLMs can perform on par with, or even better than, existing encoder-based approaches. Nevertheless, we find that LLMs alone struggle to capture subtle lexical relations between arguments for the task. To address this, we propose a two-step strategy that enriches arguments with explicit lexical-level semantic cues before fine-tuning. Experiments demonstrate substantial gains, particularly in cross-domain scenarios, with F1 scores improved by more than 10 points compared to strong baselines.
Anthology ID:
2026.findings-eacl.239
Volume:
Findings of the Association for Computational Linguistics: EACL 2026
Month:
March
Year:
2026
Address:
Rabat, Morocco
Editors:
Vera Demberg, Kentaro Inui, Lluís Marquez
Venue:
Findings
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Publisher:
Association for Computational Linguistics
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Pages:
4585–4602
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URL:
https://preview.aclanthology.org/ingest-eacl/2026.findings-eacl.239/
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Cite (ACL):
Yi Fan, Michael Strube, and Wei Liu. 2026. Linguistic Cues for LLM-based Implicit Discourse Relation Classification. In Findings of the Association for Computational Linguistics: EACL 2026, pages 4585–4602, Rabat, Morocco. Association for Computational Linguistics.
Cite (Informal):
Linguistic Cues for LLM-based Implicit Discourse Relation Classification (Fan et al., Findings 2026)
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