The Flash-Lag, Fröhlich and Related Motion Illusions Are Natural Consequences of Discrete Sampling in the Visual System.

Keith A Schneider

doi:10.3389/fpsyg.2018.01227

Abstract

The Fröhlich effect and flash-lag effect, in which moving objects appear advanced along their trajectories compared to their actual positions, have defied a simple and consistent explanation. Here, I show that these illusions can be understood as a natural consequence of temporal compression in the human visual system. Discrete sampling at some stage of sensory perception has long been considered, and if it were true, it would necessarily lead to these illusions of motion. I show that the discrete perception hypothesis, with a single free parameter, the perceptual moment or sampling rate, can quantitatively explain all of the scenarios of the Fröhlich and flash-lag effect. I interpret discrete perception as the implementation of data compression in the brain, and our conscious perception as the reconstruction of the compressed input.

Highlights

The human visual system makes consistent errors localizing the positions of moving objects (Linares et al, 2009)
I hypothesize that visual input is sampled into discrete perceptual moments of duration D, and that any moving objects that might occupy a range of positions during the moment are registered at their final position occupied during each moment
In the Fröhlich effect (Figure 1), when the moving object appears, its first location is not registered until the end of the current perceptual moment

Summary

Introduction

The human visual system makes consistent errors localizing the positions of moving objects (Linares et al, 2009). Attribute changes occurring within moving objects are perceived as, displaced (Zeki and Moutoussis, 1997; Eagleman and Sejnowski, 2007). These motion illusions have defied coherent explanation, but I demonstrate that they can be explained as artifacts of discrete temporal subsampling in the visual system (Stroud, 1954). The illusions are a natural consequence of a discrete perception hypothesis wherein visual input is broken into discrete perceptual moments, with moving objects registered only in their final positions during each moment. James (1909), influenced by Bergson, changed positions, writing, “Time itself comes in drops” I show that the discrete perception hypothesis elegantly explains a large class of visual illusions

Results

Discussion

Conclusion