The Illusion of Progress: Re-evaluating Hallucination Detection in LLMs

Fuente: arXiv
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Autori principali: Janiak, Denis, Binkowski, Jakub, Sawczyn, Albert, Gabrys, Bogdan, Shwartz-Ziv, Ravid, Kajdanowicz, Tomasz
Natura: Preprint
Pubblicazione: 2025
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author Janiak, Denis
Binkowski, Jakub
Sawczyn, Albert
Gabrys, Bogdan
Shwartz-Ziv, Ravid
Kajdanowicz, Tomasz
author_facet Janiak, Denis
Binkowski, Jakub
Sawczyn, Albert
Gabrys, Bogdan
Shwartz-Ziv, Ravid
Kajdanowicz, Tomasz
contents Large language models (LLMs) have revolutionized natural language processing, yet their tendency to hallucinate poses serious challenges for reliable deployment. Despite numerous hallucination detection methods, their evaluations often rely on ROUGE, a metric based on lexical overlap that misaligns with human judgments. Through comprehensive human studies, we demonstrate that while ROUGE exhibits high recall, its extremely low precision leads to misleading performance estimates. In fact, several established detection methods show performance drops of up to 45.9\% when assessed using human-aligned metrics like LLM-as-Judge. Moreover, our analysis reveals that simple heuristics based on response length can rival complex detection techniques, exposing a fundamental flaw in current evaluation practices. We argue that adopting semantically aware and robust evaluation frameworks is essential to accurately gauge the true performance of hallucination detection methods, ultimately ensuring the trustworthiness of LLM outputs.
format Preprint
id arxiv_https___arxiv_org_abs_2508_08285
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The Illusion of Progress: Re-evaluating Hallucination Detection in LLMs
Janiak, Denis
Binkowski, Jakub
Sawczyn, Albert
Gabrys, Bogdan
Shwartz-Ziv, Ravid
Kajdanowicz, Tomasz
Computation and Language
Artificial Intelligence
Machine Learning
Large language models (LLMs) have revolutionized natural language processing, yet their tendency to hallucinate poses serious challenges for reliable deployment. Despite numerous hallucination detection methods, their evaluations often rely on ROUGE, a metric based on lexical overlap that misaligns with human judgments. Through comprehensive human studies, we demonstrate that while ROUGE exhibits high recall, its extremely low precision leads to misleading performance estimates. In fact, several established detection methods show performance drops of up to 45.9\% when assessed using human-aligned metrics like LLM-as-Judge. Moreover, our analysis reveals that simple heuristics based on response length can rival complex detection techniques, exposing a fundamental flaw in current evaluation practices. We argue that adopting semantically aware and robust evaluation frameworks is essential to accurately gauge the true performance of hallucination detection methods, ultimately ensuring the trustworthiness of LLM outputs.
title The Illusion of Progress: Re-evaluating Hallucination Detection in LLMs
topic Computation and Language
Artificial Intelligence
Machine Learning
url https://arxiv.org/abs/2508.08285