An animated version of the Cafe Wall Illusion

If the left-slanting and right-slanting versions of the Cafe Wall Illusion are alternated more rapidly than 3 times per second, the perception of slant starts to disappear. When these figures alternate twice a second, the alternation of the illusory slant is quite clear. This shows that the visual system takes about 1/3 of a second to form the illusory slant percept.