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arxiv: 2606.20347 · v1 · pith:R6X2YCE4new · submitted 2026-06-18 · 💻 cs.LG · cond-mat.dis-nn

Critical Percolation as a Synthetic Data Model for Interpretability

Pith reviewed 2026-06-26 17:39 UTC · model grok-4.3

classification 💻 cs.LG cond-mat.dis-nn
keywords synthetic datainterpretabilitypercolationhierarchical modelsprobinglatent variablesneural networkspower-law distributions
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The pith

Critical percolation clusters with taxonomic latents produce synthetic data whose ground-truth hierarchy is linearly decodable from neural network activations.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper constructs synthetic datasets by embedding critical mean-field percolation clusters into high-dimensional space and assigning target values via latent variables arranged in a taxonomic hierarchy. These clusters are sparse and fractal, exhibit power-law size distributions, and have properties fixed by known critical exponents so that no hyperparameter tuning is needed. An efficient sampling algorithm based on a mapping to random trees and additive coalescence lets the data be generated at large scale. Probing experiments then demonstrate that the latent variables can be recovered by linear readouts from trained network activations. A reader would care because current synthetic datasets lack the multi-scale structure of natural data, so this model offers a controlled setting in which interpretability claims can be checked against known ground truth.

Core claim

By placing critical percolation clusters in high-dimensional space and generating labels from a taxonomic hierarchy of latent variables, the resulting data exhibits sparsity, self-similarity, and power-law statistics while remaining analytically tractable; linear probes recover the ground-truth latents from network activations.

What carries the argument

The mapping from percolation clusters to random trees via additive coalescence that jointly samples the tree and its hierarchical latent decomposition in almost linear time.

If this is right

  • The dataset supplies a scalable testbed with known ground truth for evaluating interpretability methods.
  • Because critical exponents fix all statistical properties, experiments can be reproduced without hidden tuning.
  • The same generative process can be used to create data at any desired scale while preserving the hierarchy.
  • Sparsity and fractal geometry allow direct study of how networks handle multi-scale features.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The linear decodability result suggests that future work could test whether other interpretability techniques, such as feature visualization, also align with the known hierarchy.
  • The tree-coalescence construction may connect this model to generative processes used in other areas of network science.
  • If the power-law statistics prove essential, the same percolation backbone could be reused with different label hierarchies to isolate the role of each property.

Load-bearing premise

The multi-scale hierarchical structure produced by critical percolation is close enough to natural data that interpretability conclusions transfer.

What would settle it

A linear probing experiment on networks trained on this data that recovers the latent variables at no better than chance accuracy would falsify the decodability claim.

Figures

Figures reproduced from arXiv: 2606.20347 by Aryeh Brill, Tom Ingebretsen Carlson.

Figure 1
Figure 1. Figure 1: The percolation data model. (a) Inputs are distributed as self-similar fractal clusters with power-law sizes. (b) Targets are generated by hierarchical latent variables decomposing each cluster. lent reconstruction while recovering interpretable features at different levels of abstraction (Bussmann et al., 2025; Costa et al., 2025). Compositional hierarchical structure in data can be modeled using a probab… view at source ↗
Figure 2
Figure 2. Figure 2: Bethe lattice percolation. Red: infinite cluster. Blue: finite clusters. p, forming contiguous clusters.2 We consider a hypercu￾bic lattice of dimension d and scale L. Percolation’s most notable property is a phase transition. Above a critical occu￾pation probability p = pc, the system percolates: an infinite cluster emerges that scales with the system size. Below this transition, only finite clusters exis… view at source ↗
Figure 3
Figure 3. Figure 3: Example run of the cyclic coalescent. (a) Initialize nodes in a random cycle. (b–f) At each step, connect a random node to a random node in its block’s successor, merging those blocks. d-dimensional vector space. The dimension d is a hyperpa￾rameter that can be set arbitrarily. Each cluster is embedded by first randomly choosing a root node and then iteratively embedding each node’s neighbors following a b… view at source ↗
Figure 4
Figure 4. Figure 4: Per-latent linear probe performance for individual latent values zi, showing (a) the one-cluster dataset and (b) the multi-cluster dataset. Dots (squares) mark the median MSE for the residual stream (hidden activations). Error bars show 25th and 75th percentiles. The ratio panels show each layer’s per-latent MSE normalized by the MSE of probes trained on the raw input [PITH_FULL_IMAGE:figures/full_fig_p00… view at source ↗
Figure 5
Figure 5. Figure 5 [PITH_FULL_IMAGE:figures/full_fig_p007_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: A comparison of taxonomic and compositional hierarchi￾cal structures [PITH_FULL_IMAGE:figures/full_fig_p008_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Per-latent linear probe performance for partial cumulative sums of latent values zi, showing (a) the one-cluster dataset and (b) the multi-cluster dataset. Dots (squares) mark the median MSE for the residual stream (hidden activations). Error bars show 25th and 75th percentiles. The ratio panels show each layer’s per-latent MSE normalized by the MSE of probes trained on the raw input. 10 0 10 1 10 2 10 3 1… view at source ↗
Figure 8
Figure 8. Figure 8: Cluster size distribution. A maximum-likelihood power-law fit to clusters with s ≥ 35 is shown as a dashed red line. Each cluster (not data point) is counted once in the distribution. 19 [PITH_FULL_IMAGE:figures/full_fig_p019_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: shows plots validating the correctness of the cyclic coalescent algorithm. A well-known bijection, called a Prufer ¨ sequence (Prufer, 1918), exists between the set of n n−2 labeled trees on n nodes and the set of sequences of length n − 2 on the labels 1 to n. This bijection permits a powerful check of uniformity tractable at small tree sizes. Fig. 9a confirms that trees of size n = 6 generated by the cyc… view at source ↗
Figure 10
Figure 10. Figure 10: Performance validation for the cyclic coalescent. Panel (a) shows the time required to generate a random tree as a function of tree size for the cyclic coalescent and two O(n) baseline methods, described in the text. The data points show the mean and standard deviation over 20 trials. The black dashed lines show linear fits. The slopes are consistent among the methods. Panel (b) shows the performance rati… view at source ↗
read the original abstract

Neural networks learn features that reflect the hierarchical, multi-scale structure of natural data. Synthetic datasets used to evaluate interpretability methods typically lack this structure, limiting their value as realistic toy models. To close this gap, we introduce a family of synthetic datasets consisting of hierarchical functions defined on critical mean-field percolation clusters embedded in a high-dimensional data space. The percolation data consists of sparse, low-dimensional fractal clusters with a power-law size distribution. Latent variables modeling a taxonomic hierarchy generate each data point's target value. The data model is analytically tractable with known critical exponents that fix its properties without requiring hyperparameter tuning. We leverage a mapping between percolation clusters, random trees, and additive coalescence to propose an almost linear-time algorithm to jointly sample a random tree and its hierarchical latent decomposition, enabling data generation at arbitrary scale. Using probing experiments, we find that the model's ground-truth latent variables can be linearly decoded from neural network activations. Together, sparsity, self-similarity, power-law statistics, and analytical tractability make critical percolation a principled testbed for interpretability research.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The paper introduces a family of synthetic datasets generated from hierarchical latent variables defined on critical mean-field percolation clusters embedded in high-dimensional space. These clusters exhibit sparsity, self-similarity, and power-law size distributions fixed by known critical exponents, eliminating the need for hyperparameter tuning. A sampling algorithm is derived from mappings between percolation clusters, random trees, and additive coalescence, enabling near-linear-time generation at scale. Probing experiments are reported to show that the ground-truth taxonomic latent variables are linearly decodable from neural network activations, positioning the model as a tractable testbed for interpretability research.

Significance. If the linear decodability result is robust, the model supplies a scalable, analytically tractable synthetic data source whose multi-scale hierarchical structure is fixed by external percolation theory rather than fitted parameters. The efficient sampling procedure and explicit use of critical exponents constitute concrete strengths that could support reproducible, large-scale interpretability experiments.

major comments (2)
  1. [Probing experiments section] Probing experiments section: the central claim that ground-truth latent variables are linearly decodable from network activations is load-bearing for the utility as an interpretability testbed, yet the manuscript provides no details on network architecture (depth/width), training objective, probe training protocol (held-out sets, regularization), baseline comparisons, or controls for confounders arising from the data-generation procedure itself.
  2. [Data model section] Data model section: the claim that the constructed hierarchical structure is sufficiently similar to natural data for interpretability conclusions to transfer rests on the overlay of taxonomic latents onto percolation clusters, but no quantitative comparison (e.g., matching of multi-scale correlation functions or power-law exponents against real datasets) is supplied to support transferability.
minor comments (2)
  1. [Abstract] The abstract states the algorithm is 'almost linear-time' without providing the precise complexity bound or empirical scaling measurements.
  2. [Algorithm description] Notation for the hierarchical latent decomposition and the coalescence mapping could be introduced with an explicit diagram or pseudocode to improve readability.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the detailed review and constructive comments. We address each major point below, agreeing where additional details or clarifications are warranted and outlining specific revisions to improve the manuscript.

read point-by-point responses
  1. Referee: [Probing experiments section] Probing experiments section: the central claim that ground-truth latent variables are linearly decodable from network activations is load-bearing for the utility as an interpretability testbed, yet the manuscript provides no details on network architecture (depth/width), training objective, probe training protocol (held-out sets, regularization), baseline comparisons, or controls for confounders arising from the data-generation procedure itself.

    Authors: We agree that these experimental details are necessary for reproducibility and to substantiate the central claim. The revised manuscript will expand the probing experiments section to specify the network architecture (depth and width), training objective, probe training protocol (including held-out sets and regularization), baseline comparisons, and controls for any confounders from the data-generation procedure. revision: yes

  2. Referee: [Data model section] Data model section: the claim that the constructed hierarchical structure is sufficiently similar to natural data for interpretability conclusions to transfer rests on the overlay of taxonomic latents onto percolation clusters, but no quantitative comparison (e.g., matching of multi-scale correlation functions or power-law exponents against real datasets) is supplied to support transferability.

    Authors: The manuscript positions the model primarily as an analytically tractable testbed whose hierarchical structure is fixed by known critical exponents rather than as a direct proxy for natural data whose conclusions transfer via similarity. We do not make a strong claim of transferability based on quantitative matching. That said, we will add a brief discussion or appendix noting relevant power-law statistics from percolation theory and any available comparisons to real datasets to clarify the model's intended scope and limitations. revision: partial

Circularity Check

0 steps flagged

No significant circularity; derivation draws on external percolation theory

full rationale

The paper constructs a synthetic data model by embedding critical mean-field percolation clusters (with known external critical exponents) into high-dimensional space and overlaying a taxonomic latent hierarchy. The sampling algorithm is derived from a mapping to random trees and additive coalescence, presented as a new contribution rather than a reduction of fitted quantities. Linear decodability is reported from probing experiments, not from any closed-form derivation or self-referential fit. No equations or claims reduce by construction to the paper's own inputs; critical exponents and percolation properties are cited as independent, analytically fixed facts from established theory. This is self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 1 invented entities

The central claim rests on the domain assumption that critical percolation supplies the desired statistical properties without tuning and that the added latent hierarchy is a faithful model of taxonomic structure; no free parameters are introduced because critical exponents fix the properties.

axioms (1)
  • domain assumption Critical mean-field percolation clusters possess known critical exponents that determine sparsity, fractality, and power-law size distribution without hyperparameter tuning.
    Explicitly stated in the abstract as the reason the model requires no tuning.
invented entities (1)
  • Hierarchical latent variables defined on percolation clusters no independent evidence
    purpose: To generate target values via a taxonomic hierarchy.
    Introduced by the authors to add structure to the percolation data.

pith-pipeline@v0.9.1-grok · 5716 in / 1238 out tokens · 24541 ms · 2026-06-26T17:39:05.961800+00:00 · methodology

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