Motion detection is dependent on spatial frequency not size.

The maximum displacement for the detection of apparent motion is measured using stimuli made up of micro-patterns randomly distributed across the stimulus field. The micro-patterns were Gabor functions or half-wave rectified Gabor functions. Dmax is shown to be dependent of the spatial frequency content of the stimulus, and to be largely independent of the size of the stimulus elements or the number of them in the stimulus field (within limits). Evidence is shown for Dmax to be considered a measure of motion detection that reveals properties of low level underlying motion mechanisms.