Consistency of perceptual response variability in size estimation and reproduction tasks.

Measuring perceptual uncertainty is important for understanding how perception influences post-perception behavior, while it remains unknown whether measured perceptual responses in behavioral tasks reflect true perceptual uncertainty or methodological artifacts. This study compared two size perception approaches: a visual analog scale (VAS) estimation task and a reproduction task. We recruited 180 participants who completed both tasks by estimating circle diameters on a VAS and adjusting circle sizes to match specified diameters. Our analysis used two Bayesian multilevel models - a variance decomposition model computing intraclass correlation coefficients (ICCs) for overall response consistency, and a generative psychophysical model to characterize perceptual response patterns. Results revealed high overall response consistency across tasks, but detailed variance component analysis uncovered systematic method differences. Participant, stimulus, and interaction variances were consistently higher in the estimation task, indicating greater individual differences and more idiosyncratic responses. Psychophysical analyses further showed that the estimation task produced a steeper perceptual slope and a lower intercept compared to reproduction. Notably, while overall task-level perceptual uncertainty was nearly identical, the scaling of uncertainty with stimulus size was markedly stronger in estimation. These findings suggest that much of the observed variability reflects genuine perceptual uncertainty rather than measurement error, though distinct cognitive demands shape its expression. Our results confirm that both VAS and reproduction tasks yield consistent measures of perceptual variability, underscoring their value in behavioral research and the need for future studies to disentangle intrinsic perceptual processes from task-specific noise.