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Hauptverfasser: Hagar, Nick, Agustianto, Wilma, Diakopoulos, Nicholas
Format: Preprint
Veröffentlicht: 2025
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Online-Zugang:https://arxiv.org/abs/2509.25498
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author Hagar, Nick
Agustianto, Wilma
Diakopoulos, Nicholas
author_facet Hagar, Nick
Agustianto, Wilma
Diakopoulos, Nicholas
contents Large language models (LLMs) are increasingly used in newsroom workflows, but their tendency to hallucinate poses risks to core journalistic practices of sourcing, attribution, and accuracy. We evaluate three widely used tools - ChatGPT, Gemini, and NotebookLM - on a reporting-style task grounded in a 300-document corpus related to TikTok litigation and policy in the U.S. We vary prompt specificity and context size and annotate sentence-level outputs using a taxonomy to measure hallucination type and severity. Across our sample, 30% of model outputs contained at least one hallucination, with rates approximately three times higher for Gemini and ChatGPT (40%) than for NotebookLM (13%). Qualitatively, most errors did not involve invented entities or numbers; instead, we observed interpretive overconfidence - models added unsupported characterizations of sources and transformed attributed opinions into general statements. These patterns reveal a fundamental epistemological mismatch: While journalism requires explicit sourcing for every claim, LLMs generate authoritative-sounding text regardless of evidentiary support. We propose journalism-specific extensions to existing hallucination taxonomies and argue that effective newsroom tools need architectures that enforce accurate attribution rather than optimize for fluency.
format Preprint
id arxiv_https___arxiv_org_abs_2509_25498
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Not Wrong, But Untrue: LLM Overconfidence in Document-Based Queries
Hagar, Nick
Agustianto, Wilma
Diakopoulos, Nicholas
Computation and Language
Artificial Intelligence
Large language models (LLMs) are increasingly used in newsroom workflows, but their tendency to hallucinate poses risks to core journalistic practices of sourcing, attribution, and accuracy. We evaluate three widely used tools - ChatGPT, Gemini, and NotebookLM - on a reporting-style task grounded in a 300-document corpus related to TikTok litigation and policy in the U.S. We vary prompt specificity and context size and annotate sentence-level outputs using a taxonomy to measure hallucination type and severity. Across our sample, 30% of model outputs contained at least one hallucination, with rates approximately three times higher for Gemini and ChatGPT (40%) than for NotebookLM (13%). Qualitatively, most errors did not involve invented entities or numbers; instead, we observed interpretive overconfidence - models added unsupported characterizations of sources and transformed attributed opinions into general statements. These patterns reveal a fundamental epistemological mismatch: While journalism requires explicit sourcing for every claim, LLMs generate authoritative-sounding text regardless of evidentiary support. We propose journalism-specific extensions to existing hallucination taxonomies and argue that effective newsroom tools need architectures that enforce accurate attribution rather than optimize for fluency.
title Not Wrong, But Untrue: LLM Overconfidence in Document-Based Queries
topic Computation and Language
Artificial Intelligence
url https://arxiv.org/abs/2509.25498