A Basic Asymmetry in Motion Perception

The admitted interpretation of the apparent motion phenomenon (and of motion perception in general) is that the visual system matches across space and time the invariant attributes of the displaced image. However, motion perception does not require that all image attributes be matched in space and time. Our experiments lead to the distinction of two clas- ses of visual attributes whose spatio-temporal matching is either "uncritical" or "critical" in motion perception. Luminance (contrast) and orientation belong to the first class.