Motion

Overview

The relationship between objects, retinal images and observer are rarely, if ever, static. Any theory of vision must thus deal with the perceptions of motion that are generated by sequences of images. As in the perception of luminance, spectral differences, geometrical form, distance and depth, there are many long-standing puzzles about the genesis of motion percepts. Preeminent among these are the odd way that the speed of motion is seen, apparent in phenomena such as the flash-lag effect. Equally puzzling are the dramatic changes in the apparent direction of motion that occur when moving objects viewed through apertures. These peculiarities have been the subject of debates for decades, and it is clear that any theory of perceived motion must be able to rationalize them. The upshot is that, much as in other visual perceptual categories, the way humans see motion can be also understood in terms of a scheme of neural processing that generates percepts according to past experience arising from the need to generate useful behavior in response to image sequences that cannot specify moving sources in any direct way.