Comparison with reverse phi
Click on:
Real motion clockwise:
Counter-clockwise:

The "high phi" illusion seems to be closely related to the "reverse phi" phenomenon (Reichardt, 1961; Anstis, 1970). In reverse phi, an object simulatenously moves and reverses contrast—and seems to jump the other way. Using the buttons above, "reverse phi" can be compared with "high phi". In reverse phi, the texture turns by 1° and reverses contrast on the same frame; in high phi (with brief adapter), the texture turns by 1° and reverses contrast on the next frame.

Many observers have a clearer perception of reverse phi in the periphery (when looking at the edge of your monitor, for instance).

There's a great deal of variation in the amplitude of the two illusions from one observer to the next, but we have shown that they are closely correlated across observers.