MERGE: Minimal Expression-Replacement GEneralization Test for Natural Language Inference

Mădălina Zgreabăn, Tejaswini Deoskar, Lasha Abzianidze


Abstract
As many benchmarks have become saturated, it is increasingly important to create new datasets that evaluate the generalization capacity of current state-of-the-art models in reasoning. However, creating high-quality reasoning datasets is challenging: manual construction is costly, and automatic generation is error-prone, with the community therefore relying on synthetic datasets with limited scope. In this paper, we propose the Minimal Expression Replacement GEneralization (MERGE) test, to evaluate the robustness of reasoning models against minimal and non-adversarial variants of existing evaluation datasets. First, high-quality variants are automatically obtained from the original instances using Masked Language Models (MLMs) for generation together with safeguarding filters, called Minimal Expression Replacement (MERE). We then apply the MERGE test to Natural Language Inference (NLI), a popular reasoning task, by using MERE on two popular existing NLI datasets. We evaluate multiple strong NLI models and LLMs, and the results indicate they generalize poorly: both struggle to consistently and correctly classify variants minimally different in form, but similar in reasoning, from the original ones. We also analyze how aspects of variant generation, such as word class and source MLMs, affect model performance.
Anthology ID:
2026.blackboxnlp-1.53
Volume:
Proceedings of the 9th BlackboxNLP Workshop: Analyzing and Interpreting Neural Networks for NLP
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Dana Arad, Yonatan Belinkov, Hanjie Chen, Nils Feldhus, Aaron Mueller, Hosein Mohebbi, Gabriele Sarti, Martin Tutek
Venues:
BlackboxNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
937–964
Language:
URL:
https://aclanthology.org/2026.blackboxnlp-1.53/
DOI:
Bibkey:
Cite (ACL):
Mădălina Zgreabăn, Tejaswini Deoskar, and Lasha Abzianidze. 2026. MERGE: Minimal Expression-Replacement GEneralization Test for Natural Language Inference. In Proceedings of the 9th BlackboxNLP Workshop: Analyzing and Interpreting Neural Networks for NLP, pages 937–964, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
MERGE: Minimal Expression-Replacement GEneralization Test for Natural Language Inference (Zgreabăn et al., BlackboxNLP 2026)
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PDF:
https://aclanthology.org/2026.blackboxnlp-1.53.pdf