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Stochastic Sampling is Epistemically Shallow: The Dimensionality Gap Between Temperature Variation and Model Diversity in LLMs

Research finds that answer variation from repeated runs of a single LLM via temperature sampling (self-consistency) only reveals a single dimension of structure, while an ensemble of multiple different models detects more cross-question signals, better revealing what the model does not know.

SourcearXiv AIAuthor: Izhar Ali

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[Submitted on 18 May 2026]

Title:Stochastic Sampling is Epistemically Shallow: The Dimensionality Gap Between Temperature Variation and Model Diversity in LLMs

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Abstract:When a language model gives different answers on repeated runs, does that variation reveal what it does not know? Self-consistency turns the variation into a per-question uncertainty estimate via majority voting. But does the same variation reveal cross-question structure -- related questions flipping together, the way a diverse ensemble does? We compare two regimes on the same questions: one model run $100$ times at $\tau=1$ versus an ensemble of $24$ LLMs run once each at $\tau=0$. A Marchenko--Pastur random-matrix test separates signal from sampling noise on both sides. Within any single model, at most one dimension rises above noise across five families and three benchmarks (MMLU, HellaSwag, GSM8K). Across the ensemble, four eigenvalues clear the noise edge, while a matched-difficulty Bernoulli null produces at most one in $500$ Monte Carlo draws. Self-consistency gives accurate per-question uncertainty but no detectable cross-question structure; only a diverse ensemble surfaces what a model does not know.

Comments: 8 pages, 4 figures, 3 tables. Accepted at EIML@ICML 2026

Subjects:

Artificial Intelligence (cs.AI)

Cite as: arXiv:2607.20464 [cs.AI]

(or arXiv:2607.20464v1 [cs.AI] for this version)

https://doi.org/10.48550/arXiv.2607.20464

arXiv-issued DOI via DataCite (pending registration)

Submission history

From: Izhar Ali [view email] [v1] Mon, 18 May 2026 14:40:37 UTC (179 KB)

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