Spatial sampling of motion: Seeing an object moving behind a picket fence.

Abstract

Spatially sampled motion (H.P. Snippe & J.J. Koenderink, 1994) leads to time-lagged correlations of luminance change at discrete spatial positions. Observers matched the perceived width of a bar whose motion path was sampled spatially to the width of a static bar; the width of the moving object was not directly observable. Observers did reasonably well on this task when the stimulus onset asynchrony (SOA) between adjacent samples was approximately 90 ms, but performance broke down completely when the SOA was doubled. Performance improved considerably as more samples became available, provided that these samples all fell along the same smooth motion path and were seen by the same eye. This spatiotemporal information in spatially sampled motion can specify the width of a moving object, but it is likely to be useful to observers only if the sampling preserves the impression of motion.

The impact of spatiotemporal sampling on time-to-contact judgments

“…Temporally and spatially alternating objects were first created on turntables (Wertheimer, 1912) by moving a radial line behind a stationary template that contained different apertures to produce the desired sampling rates. With the introductionof light-emittingdiodes (LEDs) and computer displays, discrete sampling became predominant.Aperture sampling has been referred to, somewhat confusingly, as spatial sampling (Dannemiller, Heidenreich, & Babler, 1997). Obviously, temporal and spatial sampling co-occur so long as the object in question is moving.…”