The “Exorcist illusion” is a tricky variation of the hollow-face illusion. We rigidly fused a concave mask and convex torso and vice versa (a challenging sculpting task around the neck). We then painted these rigid “statues” realistically and rotated them. Even though they have no moving parts, they create a compelling paradoxical illusion of twisting necks! The torso rotates in one direction and the face rotates in the opposite direction; thus the neck twists in a strange fashion, similar to the “Exorcist” movie (1973). Also, if a viewer moves in front of the statue, the neck appears to twist dangerously.
Rolling Eyes on a Hollow Mask
The well-known hollow-mask illusion: hollow masks appear as normal faces that “follow” viewers who move in front of them. Also, when a hollow mask rotates on a turntable, it appears to turn opposite to the actual direction of the turntable.
An interesting variant: If we add 3-D objects to the mask (e.g., a cigarette) or attach 3-D eyeballs on the whites of the eyes, what will the percept be when we turn the mask? Answer: The result is a compelling illusion in its own right; these objects appear to rotate in the opposite direction to that of the mask.
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Read more about the illusion and possible explanations