150 years of research on Vierordt’s law - Fechner’s fault?

150 years ago, the physiologist Karl Vierordt discovered one type of systematic errors in time perception – an overestimation of long durations and underestimation of short durations, now known as Vierordt’s law. Here we review the original study in its historical context and ask whether Vierordt’s law is a result of an unnatural experimental randomization protocol. Using iterative Bayesian updating, we simulated the original results with astonishing accuracy. To validate whether the experimental protocol matters, we compared duration reproduction from two sequences with the same sampled distribution and found that trial-wise variation determines the reproduction error. We conclude that Vierordt’s law is caused by an unnatural yet widely used experimental protocol. One Sentence Summary Probabilistic modeling reveals that a classical perceptual error - Vierordt’s law - is caused by an unnatural yet widely used experimental protocol.