Competing motion paths in sequence of random dot patterns.

Global motion perception from a sequence of random dot patterns has been studied by means of the competition technique which consists of making a normally less salient motion path in a superimposed multiple-path stimulus more powerful by adding luminous energy to elements forming this path. The perceived motion direction of a sequence of random dot patterns can be dramatically changed by increasing luminance of some fraction of dots leaving all spatial and temporal intervals between dots unchanged. The threshold luminance increment delta I that is required in order to change the perceived motion direction indicates that differently oriented local motion vectors are resolved into a single common motion vector along which the whole pattern appears to move. An inverse spatial proximity rule was discovered: within a certain spatial limit the motion strength of a particular motion path is proportional to the distance between stimulus elements forming this path.