Low Spatial Frequecies prefered over sharp edges
The fact that a viewer is more likely to percieve the solid white square moving back and forth from/to the solid white circle (with the outlined square just blinking on and off) suggests that the brain prefers to resolve correspondence problems (when confronted with multiple choices), by viewing areas of Low Spatial Frequencies as opposed to sharp edges. One reason for this is again from an evolutionary point of view, where by a dark blur moveing in a forest was much more important to human survival than a tree swaying in the breeze. Thus, we see the important features and ignore the unimportant information.
Texture is the feature here that is causing motion to be observed
The above experiment is demonstrating that texture is the Salient feature that is being detected, and not a point by point comparison when the two images alternate because essentially there are no correlations in the above figures.