A theory of learning data statistics in diffusion models, from easy to hard
- URL: http://arxiv.org/abs/2603.12901v1
- Date: Fri, 13 Mar 2026 11:07:01 GMT
- Title: A theory of learning data statistics in diffusion models, from easy to hard
- Abstract summary: We show that diffusion models trained on natural images exhibit a distributional simplicity bias, learning simple, pair-wise input statistics before specializing to higher-order correlations.<n>We reproduce this behaviour in simple denoisers trained on a minimal data model, the mixed cumulant model.<n>Our work describes a key mechanism for how diffusion models can learn distributions of increasing complexity.
- Score: 11.841482748098327
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: While diffusion models have emerged as a powerful class of generative models, their learning dynamics remain poorly understood. We address this issue first by empirically showing that standard diffusion models trained on natural images exhibit a distributional simplicity bias, learning simple, pair-wise input statistics before specializing to higher-order correlations. We reproduce this behaviour in simple denoisers trained on a minimal data model, the mixed cumulant model, where we precisely control both pair-wise and higher-order correlations of the inputs. We identify a scalar invariant of the model that governs the sample complexity of learning pair-wise and higher-order correlations that we call the diffusion information exponent, in analogy to related invariants in different learning paradigms. Using this invariant, we prove that the denoiser learns simple, pair-wise statistics of the inputs at linear sample complexity, while more complex higher-order statistics, such as the fourth cumulant, require at least cubic sample complexity. We also prove that the sample complexity of learning the fourth cumulant is linear if pair-wise and higher-order statistics share a correlated latent structure. Our work describes a key mechanism for how diffusion models can learn distributions of increasing complexity.
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