When two square-wave gratings, drifting in opposite directions, are added, there are one of two possible percepts: (1) a single coherent plaid pattern is seen; (2) the individual gratings are seen as transparent , i.e., sliding over one another. We have found that speed is one of the dominant factors in governing this percept. Illustrated to the right is an idealized plot of our results. We believe that this result suggests a perceptual preference for slower speeds in the human visual system.

(Collaborative work with Eero Simoncelli)