@inproceedings{vaquet-etal-2026-probing,
title = "A Probing-Based Explanation of the Effect of Existential Presuppositions on Hallucinations in Large Language Models",
author = {Vaquet, Jonas and
P{\"u}tz, Ole and
Paassen, Benjamin},
editor = "Lee, Hung-Yi and
Dev, Sunipa and
Li, Jessy and
Elliott, Desmond",
booktitle = "Findings of the {A}ssociation for {C}omputational {L}inguistics: {EMNLP} 2026",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.findings-emnlp.26/",
pages = "519--535",
ISBN = "979-8-89176-462-0",
abstract = "With the recent commercial availability of Large Language Models (LLMs), end users increasingly turn to them for encyclopedic knowledge. Doing so, users may inadvertently inject incorrect assumptions (as presuppositions) into LLM prompts, which are then affirmed by LLMs. In this work, we investigate the effect that existential presuppositions have on LLM responses. We introduce the Dataset for Evaluating and Explaining the Effect of Existential Presuppositions (D4EP) and use it to quantify their effect. We further develop a probing-based explanation that analyzes the LLM as a classifier and finds that the effect of presuppositions corresponds to a change of the classifier{'}s operating point."
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<abstract>With the recent commercial availability of Large Language Models (LLMs), end users increasingly turn to them for encyclopedic knowledge. Doing so, users may inadvertently inject incorrect assumptions (as presuppositions) into LLM prompts, which are then affirmed by LLMs. In this work, we investigate the effect that existential presuppositions have on LLM responses. We introduce the Dataset for Evaluating and Explaining the Effect of Existential Presuppositions (D4EP) and use it to quantify their effect. We further develop a probing-based explanation that analyzes the LLM as a classifier and finds that the effect of presuppositions corresponds to a change of the classifier’s operating point.</abstract>
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%0 Conference Proceedings
%T A Probing-Based Explanation of the Effect of Existential Presuppositions on Hallucinations in Large Language Models
%A Vaquet, Jonas
%A Pütz, Ole
%A Paassen, Benjamin
%Y Lee, Hung-Yi
%Y Dev, Sunipa
%Y Li, Jessy
%Y Elliott, Desmond
%S Findings of the Association for Computational Linguistics: EMNLP 2026
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-462-0
%F vaquet-etal-2026-probing
%X With the recent commercial availability of Large Language Models (LLMs), end users increasingly turn to them for encyclopedic knowledge. Doing so, users may inadvertently inject incorrect assumptions (as presuppositions) into LLM prompts, which are then affirmed by LLMs. In this work, we investigate the effect that existential presuppositions have on LLM responses. We introduce the Dataset for Evaluating and Explaining the Effect of Existential Presuppositions (D4EP) and use it to quantify their effect. We further develop a probing-based explanation that analyzes the LLM as a classifier and finds that the effect of presuppositions corresponds to a change of the classifier’s operating point.
%U https://aclanthology.org/2026.findings-emnlp.26/
%P 519-535
Markdown (Informal)
[A Probing-Based Explanation of the Effect of Existential Presuppositions on Hallucinations in Large Language Models](https://aclanthology.org/2026.findings-emnlp.26/) (Vaquet et al., Findings 2026)
ACL