What do Geometric Hallucination Detection Metrics Actually Measure?

Fuente: arXiv
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Hauptverfasser: Yeats, Eric, Buckheit, John, Scullen, Sarah, Kennedy, Brendan, Truong, Loc, Brown, Davis, Kay, Bill, Joslyn, Cliff, Emerson, Tegan, Henry, Michael J., Emanuello, John, Kvinge, Henry
Format: Preprint
Veröffentlicht: 2026
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author Yeats, Eric
Buckheit, John
Scullen, Sarah
Kennedy, Brendan
Truong, Loc
Brown, Davis
Kay, Bill
Joslyn, Cliff
Emerson, Tegan
Henry, Michael J.
Emanuello, John
Kvinge, Henry
author_facet Yeats, Eric
Buckheit, John
Scullen, Sarah
Kennedy, Brendan
Truong, Loc
Brown, Davis
Kay, Bill
Joslyn, Cliff
Emerson, Tegan
Henry, Michael J.
Emanuello, John
Kvinge, Henry
contents Hallucination remains a barrier to deploying generative models in high-consequence applications. This is especially true in cases where external ground truth is not readily available to validate model outputs. This situation has motivated the study of geometric signals in the internal state of an LLM that are predictive of hallucination and require limited external knowledge. Given that there are a range of factors that can lead model output to be called a hallucination (e.g., irrelevance vs incoherence), in this paper we ask what specific properties of a hallucination these geometric statistics actually capture. To assess this, we generate a synthetic dataset which varies distinct properties of output associated with hallucination. This includes output correctness, confidence, relevance, coherence, and completeness. We find that different geometric statistics capture different types of hallucinations. Along the way we show that many existing geometric detection methods have substantial sensitivity to shifts in task domain (e.g., math questions vs. history questions). Motivated by this, we introduce a simple normalization method to mitigate the effect of domain shift on geometric statistics, leading to AUROC gains of +34 points in multi-domain settings.
format Preprint
id arxiv_https___arxiv_org_abs_2602_09158
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle What do Geometric Hallucination Detection Metrics Actually Measure?
Yeats, Eric
Buckheit, John
Scullen, Sarah
Kennedy, Brendan
Truong, Loc
Brown, Davis
Kay, Bill
Joslyn, Cliff
Emerson, Tegan
Henry, Michael J.
Emanuello, John
Kvinge, Henry
Machine Learning
Artificial Intelligence
Hallucination remains a barrier to deploying generative models in high-consequence applications. This is especially true in cases where external ground truth is not readily available to validate model outputs. This situation has motivated the study of geometric signals in the internal state of an LLM that are predictive of hallucination and require limited external knowledge. Given that there are a range of factors that can lead model output to be called a hallucination (e.g., irrelevance vs incoherence), in this paper we ask what specific properties of a hallucination these geometric statistics actually capture. To assess this, we generate a synthetic dataset which varies distinct properties of output associated with hallucination. This includes output correctness, confidence, relevance, coherence, and completeness. We find that different geometric statistics capture different types of hallucinations. Along the way we show that many existing geometric detection methods have substantial sensitivity to shifts in task domain (e.g., math questions vs. history questions). Motivated by this, we introduce a simple normalization method to mitigate the effect of domain shift on geometric statistics, leading to AUROC gains of +34 points in multi-domain settings.
title What do Geometric Hallucination Detection Metrics Actually Measure?
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2602.09158