A uniform flickering field is perceived as containing spatial and temporal articulations quite unlike the stimulus. Among these is an apparent oscillatory rotation of perceived patterns. The stimulus luminance required for the perception of such movement is determined for various stimulus frequencies. This threshold is found to lie consistently higher than the luminance threshold for one broad category of perceived patterns, namely, those exhibiting geometrical features. It is concluded that the oscillatory movement depends on such patterns exposed at a certain luminance increment above their threshold.
Arnulf Remole, "Luminance thresholds for perceived movement in a flickering field," J. Opt. Soc. Am. 64, 1133-1135 (1974)