The meaningfulness of searching for minimal exposure duration to understand visual perception

Two centuries ago, Joseph Plateau remarked that when a piece of burning coal moves quickly in the dark, we see a continuous luminous streak, thus proving that the sensations produced by light have a certain duration 1 . The term “visual persistence” was later coined to describe the phenomenon that the visual perception of an object lingers for some time after its physical disappearance. This perceived duration varies with some stimulus properties, most notably its luminance, but it cannot be below a critical value known as the flicker fusion threshold. This threshold in humans is estimated to be around one sixtieth of a second 2 , so that two flashes separated by less than about 15 ms cannot be distinguished. In light of these well-established phenomena, when Lanfranco and collaborators 3 report some behavioural effects for durations as short of 0.4 ms (see their Experiment 3), their results may not be related to duration per se.