SylloBio-NLI: Evaluating Large Language Models on Biomedical Syllogistic Reasoning

Magdalena Wysocka, Danilo Carvalho, Oskar Wysocki, Marco Valentino, Andre Freitas


Abstract
Syllogistic reasoning is crucial for Natural Language Inference (NLI). This capability is particularly significant in specialized domains such as biomedicine, where it can support automatic evidence interpretation and scientific discovery. This paper presents SylloBio-NLI, a novel framework that leverages external ontologies to systematically instantiate diverse syllogistic arguments for biomedical NLI. We employ SylloBio-NLI to evaluate Large Language Models (LLMs) on identifying valid conclusions and extracting supporting evidence across 28 syllogistic schemes instantiated with human genome pathways. Extensive experiments reveal that biomedical syllogistic reasoning is particularly challenging for zero-shot LLMs, which achieve an average accuracy between 70% on generalized modus ponens and 23% on disjunctive syllogism. At the same time, we found that few-shot prompting can boost the performance of different LLMs, including Gemma (+14%) and LLama-3 (+43%). However, a deeper analysis shows that both techniques exhibit high sensitivity to superficial lexical variations, highlighting a dependency between reliability, models’ architecture, and pre-training regime. Overall, our results indicate that, while in-context examples have the potential to elicit syllogistic reasoning in LLMs, existing models are still far from achieving the robustness and consistency required for safe biomedical NLI applications.
Anthology ID:
2025.naacl-long.371
Volume:
Proceedings of the 2025 Conference of the Nations of the Americas Chapter of the Association for Computational Linguistics: Human Language Technologies (Volume 1: Long Papers)
Month:
April
Year:
2025
Address:
Albuquerque, New Mexico
Editors:
Luis Chiruzzo, Alan Ritter, Lu Wang
Venue:
NAACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
7235–7258
Language:
URL:
https://aclanthology.org/2025.naacl-long.371/
DOI:
Bibkey:
Cite (ACL):
Magdalena Wysocka, Danilo Carvalho, Oskar Wysocki, Marco Valentino, and Andre Freitas. 2025. SylloBio-NLI: Evaluating Large Language Models on Biomedical Syllogistic Reasoning. In Proceedings of the 2025 Conference of the Nations of the Americas Chapter of the Association for Computational Linguistics: Human Language Technologies (Volume 1: Long Papers), pages 7235–7258, Albuquerque, New Mexico. Association for Computational Linguistics.
Cite (Informal):
SylloBio-NLI: Evaluating Large Language Models on Biomedical Syllogistic Reasoning (Wysocka et al., NAACL 2025)
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PDF:
https://aclanthology.org/2025.naacl-long.371.pdf