Phi motion Phi motion (Wertheimer, 1912) refers to apparent motion experienced without the movement of objects. A bright spot will appear to move clockwise. Phi experiences represent a 'pure' or disembodied form of apparent motion. You may note, especially if the screen display on your computer is relatively slow, that the phi phenomenon appears more vivid in your peripheral vision while you read this than it is when you look directly at the figure. Rod vision is more sensitive to motion than cone vision and you can see the distribution of rods as more in the periphery and cones in the fovea in another part of this gallery. The phenomenon is not merely attributable to chromatic aftereffects. The spot appears similar to the background and not as the complementary color appearance of the target. It may assume a darker appearance as your fixation moves from the target. Try fixating at different distances and you may be able to see a very bright or very dark appearing spot moving.