Neither Valid nor Reliable? Investigating the Use of LLMs as Judges

Fuente: arXiv
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Auteurs principaux: Chehbouni, Khaoula, Haddou, Mohammed, Cheung, Jackie Chi Kit, Farnadi, Golnoosh
Format: Preprint
Publié: 2025
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author Chehbouni, Khaoula
Haddou, Mohammed
Cheung, Jackie Chi Kit
Farnadi, Golnoosh
author_facet Chehbouni, Khaoula
Haddou, Mohammed
Cheung, Jackie Chi Kit
Farnadi, Golnoosh
contents Evaluating natural language generation (NLG) systems remains a core challenge of natural language processing (NLP), further complicated by the rise of large language models (LLMs) that aims to be general-purpose. Recently, large language models as judges (LLJs) have emerged as a promising alternative to traditional metrics, but their validity remains underexplored. This position paper argues that the current enthusiasm around LLJs may be premature, as their adoption has outpaced rigorous scrutiny of their reliability and validity as evaluators. Drawing on measurement theory from the social sciences, we identify and critically assess four core assumptions underlying the use of LLJs: their ability to act as proxies for human judgment, their capabilities as evaluators, their scalability, and their cost-effectiveness. We examine how each of these assumptions may be challenged by the inherent limitations of LLMs, LLJs, or current practices in NLG evaluation. To ground our analysis, we explore three applications of LLJs: text summarization, data annotation, and safety alignment. Finally, we highlight the need for more responsible evaluation practices in LLJs evaluation, to ensure that their growing role in the field supports, rather than undermines, progress in NLG.
format Preprint
id arxiv_https___arxiv_org_abs_2508_18076
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Neither Valid nor Reliable? Investigating the Use of LLMs as Judges
Chehbouni, Khaoula
Haddou, Mohammed
Cheung, Jackie Chi Kit
Farnadi, Golnoosh
Computation and Language
I.2.7
Evaluating natural language generation (NLG) systems remains a core challenge of natural language processing (NLP), further complicated by the rise of large language models (LLMs) that aims to be general-purpose. Recently, large language models as judges (LLJs) have emerged as a promising alternative to traditional metrics, but their validity remains underexplored. This position paper argues that the current enthusiasm around LLJs may be premature, as their adoption has outpaced rigorous scrutiny of their reliability and validity as evaluators. Drawing on measurement theory from the social sciences, we identify and critically assess four core assumptions underlying the use of LLJs: their ability to act as proxies for human judgment, their capabilities as evaluators, their scalability, and their cost-effectiveness. We examine how each of these assumptions may be challenged by the inherent limitations of LLMs, LLJs, or current practices in NLG evaluation. To ground our analysis, we explore three applications of LLJs: text summarization, data annotation, and safety alignment. Finally, we highlight the need for more responsible evaluation practices in LLJs evaluation, to ensure that their growing role in the field supports, rather than undermines, progress in NLG.
title Neither Valid nor Reliable? Investigating the Use of LLMs as Judges
topic Computation and Language
I.2.7
url https://arxiv.org/abs/2508.18076