mlsanityData to 14 Oct 2026

Learning Hierarchical Polynomials with Three-Layer Neural Networks

arXiv 2311.13774 ↗First posted 23 Nov 2023cs.LG stat.MLcited by 9

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Abstract (arXiv)

We study the problem of learning hierarchical polynomials over the standard Gaussian distribution with three-layer neural networks. We specifically consider target functions of the form h = g circ p where p : ℝd rightarrow ℝ is a degree k polynomial and g: ℝ rightarrow ℝ is a degree q polynomial. This function class generalizes the single-index model, which corresponds to k=1, and is a natural class of functions possessing an underlying hierarchical structure. Our main result shows that for a large subclass of degree k polynomials p, a three-layer neural network trained via layerwise gradient descent on the square loss learns the target h up to vanishing test error in widetildeO(dk) samples and polynomial time. This is a strict improvement over kernel methods, which require widetilde Theta(dkq) samples, as well as existing guarantees for two-layer networks, which require the target function to be low-rank. Our result also generalizes prior works on three-layer neural networks, which were restricted to the case of p being a quadratic. When p is indeed a quadratic, we achieve the information-theoretically optimal sample complexity widetildeO(d2), which is an improvement over prior work~citepnichani2023provable requiring a sample size of widetildeTheta(d4). Our proof proceeds by showing that during the initial stage of training the network performs feature learning to recover the feature p with widetildeO(dk) samples. This work demonstrates the ability of three-layer neural networks to learn complex features and as a result, learn a broad class of hierarchical functions.

Key facts. Cited by 9 papers in the map (data through 14 Oct 2026). Builds on 26 of its 38 references that are in the map. First posted on arXiv 23 Nov 2023.

Builds on

26 of 38 references.

References · 26

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14 more
  1. 2023SGD learning on neural networks: leap complexity and saddle-to-saddle dynamicscited by 143
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Cited by year (2026 to 14 Oct)

Citing papers per year: 2024: 5; 2025: 0; 2026: 4.

9 papers.