Shared variance across FrACT visual tasks: Robust positive associations but inconclusive latent structure

A long-standing question in vision science is whether individual differences in visual performance reflect a general visual ability or a set of largely task-specific processes. Previous studies have often reported weak associations across heterogeneous perceptual tasks, challenging the idea of a common visual factor. Here, we asked whether shared variance becomes more evident when visual tasks are conceptually and procedurally similar. One hundred fifty-eight adults completed eight low-level acuity and hyperacuity paradigms implemented in FrACT₁₀: single letter, Landolt C, tumbling E, row of optotypes, flanking rings, frame ring, Vernier two-line, and Vernier three-line tasks. After outlier exclusion, analyses were conducted on 132 participants. Within-session test-retest reliability was moderate for most tasks. Pairwise correlations revealed a broad positive manifold: all correlations were positive, 27 of 28 survived false-discovery-rate correction, and Bayesian analyses provided strong evidence for nonzero associations in most task pairs. However, association strength depended strongly on task similarity, with robust correlations among optotype-based tasks and weaker links between optotype and Vernier paradigms. Exploratory factor analyses indicated substantial shared covariance but failed to support a stable latent structure: A one-factor model fit poorly, whereas two-factor and three-factor solutions produced improper estimates. These findings support an intermediate account of visual individual differences. Visual performance is neither fully independent across tasks nor reducible to a strong general visual factor; instead, commonality appears partial, task-dependent, and shaped by the composition of the task battery. OPEN PRACTICES STATEMENT: The data, data dictionary, analysis code, and rendered analysis reports that support the findings of this study are available on OSF ( https://doi.org/10.17605/OSF.IO/AKSN3 ). The study materials are described in the Method section and are based on FrACT₁₀. This study was not preregistered.