Basic demo 2
Forward jumps

Here most observers perceive an annulus undergoing fast rotations, alternatively clockwise and counterclockwise, but now seemingly without any preceding motion. The image actually rotates by 1° (alternating between clockwise and counter-clockwise, and lasting about 17 ms), immediately followed by a transient, consisting of two replacements of the random texture by new, independent random textures (duration 33 ms). Since these textures are uncorrelated, there is no coherent motion signal in the transient. Nevertheless, most observers perceive jumps of 20° to 50°, in alternating directions. Although the actual steps are themselves invisible—masked by the transient—they are amplified into the huge jumps that faithfully preserve the small steps' directions.

You can see a slowed-down version by clicking on the "Go to slow motion" button. You can also see a version without the transient by clicking on the "Remove transient" button. Note how small the actual motion seed looks compared to the perceived jumps with the transient.

We have found that for most observers, if the preceding motion lasts less than about 100 ms, the jump is seen in the same direction as the motion, as in this demonstration. For longer durations of preceding motion, jumps are usually seen in the opposite direction, as in Demonstration 1. Brief and long preceding motions—leading to forward and backward jumps, respectively—can be directly compared in this demonstration.