Spatiotopic apparent motion

At the bottom of this page is a looping movie that allows you to test spatiotopic apparent motion (a simpler version of a test originally run by Rock & Ebenholtz, 1962).

Fixate on the red disc and when it moves, refixate it at its new location. After a few cycles you should be able to synchronize your saccades with the exchanges of the red and green discs.

As you move your eyes back and forth, make a judgment of the black dots at the center. Do you see one dot moving or do you see two independent dots flashing on and off independently.

If you see motion is is vertical or is it oblique? By how much? On the retina, the motion of the black discs is close to horizontal.

Compare that motion (if you see any) to the motion you see 1) when you hold fixation continuously at one disc and 2) when you track the green disc with your eyes rather than the red one.