his document pre-registers operational definitions for a test of the Morphological Complexity Hypothesis (MCH) on the SPARC galaxy rotation curve sample (Lelli, McGaugh, Schombert 2016). MCH hypothesizes that residuals between observed and baryonic rotation velocities are correlated with morphological complexity of the host galaxy, beyond what is predicted by baryonic mass alone. Note on terminology: MCH (this work) is distinct from BCP (Boundary Completeness Principle, Bojanowski 2026 framework paper). MCH is a domain-specific empirical hypothesis testable on SPARC data; BCP is a structural meta-principle spanning multiple domains. A null result for MCH does not falsify BCP, and a positive MCH result does not by itself confirm BCP. To prevent post-hoc rationalization and p-hacking, this pre-registration fixes — before any Galaxy Zoo morphological data are fetched — the following decisions: Dynamical residual: r = Vₒbs (Rₑff) - Vbar (Rₑff), evaluated at the photometric half-light radius from SPARC tables, with fixed stellar mass-to-light ratio Υ★ = 0. 5 M☉/L☉ (3. 6 μm band). Complexity proxy: κ = B + A + T, an unweighted sum of three Galaxy Zoo 2 (or DECaLS-DR5) features: B: bar strength (normalized classifier fraction) A: arm count (expected value from classifier responses, normalized to 0, 1) T: tidal feature score (normalized classifier fraction) Statistical model: Linear regression r = α·κ + β₁·log (Mbar) + β₂·log (Rₑff) + c + ε, with mass and size as controls. Partial correlation between r and κ is the reported test statistic. Pre-registered prediction (strong form): α > 0. 5 · SD (r), at p < 0. 01 after Bonferroni correction for three features tested, on the full SPARC sample (N = 175, expected N ≈ 130-150 after quality cuts). Falsification criteria: MCH in its dominant-effect form is falsified if α is not significantly different from zero, or if effect size is below 0. 5·SD (r), or if sign reverses across mass bins. A null result will be published with the same visibility as a positive result. Sample: Full SPARC catalog (175 galaxies). Intermediate-mass bin (log Mbar ∈ 9. 4, 10. 1) is reported separately as exploratory context, not as confirmatory test. Scope note: ARG does not claim to explain or replace dark matter. This test examines whether morphological complexity is a non-trivial predictor of rotation curve residuals after controlling for baryonic mass. A positive result would motivate further physical investigation of the complexity-dynamics link; a null result falsifies the dominant-effect version of MCH. This document is the pre-registration only. Analysis, pipeline code, and results will be published as a separate Zenodo record cross-referencing this DOI. The time gap between this registration and the result publication will be explicitly reported.
Bojanowski Łukasz (Sun,) studied this question.