Unfortunately, experimental psychometrical data about the FRI and its variants are scarce, and we can only speculate about the underlying mechanisms. However, neither rotational induced motion nor its aftereffect or motion capture seem to fully explain the illusions we present here. Rather, interactions between two branches of our motion visual system—one concerned with object-surround segregation located in the inferior temporal cortex, which receives inputs from MT and possibly from MST1 “motion border cells,” and one concerned with complex (rotational) motion situated in MSTd or higher up—may be a more suitable explanation for our illusions.