PURPOSE: Classic distorted face illusion.
DESCRIPTION: Stare at the spiral disc at a fairly close distance (a few feet is best) for about thirty seconds while it is rotating at about one revolution per second. Then stare from a close distance (a couple of feet) at your neighbor's face. A distortion of the face will be perceived due to the optical channel activated by the rotating spiral.
REFERENCES: (PIRA unknown.)
EQUIPMENT: Slow rotator with spiral.
SETUP TIME: None.
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