Color Wagon Wheel

from Michael’s   Visual Phenomena & Optical Illusions

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What to see

The wheel above rotates 9 times per second by 25° to the right – just 5° short of a perfect fit, since the disks are spaced every 30°. Since our brain associates each new position with the closest preceding one, we see a counter-clockwise rotation. This is the classic wagon wheel effect, as seen in the cinema in spoke wheels and explained on the preceding page. Nothing new so far – but wait: What is this yellow tail, and how can it convince us that the wheel really is rotating clockwise?

What to do

Comments

This beautiful extension of the basic Wagon Wheel Effect was awarded 3rd prize in the 2012 Illusion of the Year contest. My demonstration above is similar to theirs (with kind permission by Arthur Shapiro), but is based on a different animation technology.

The “colour blindness” of the motion system is relevant for more intesting phenomena, see Stepping Feet and Structure from Motion.

Sources

Arthur Shapiro, William Kistler, and Alex Rose-Henig (2012) Color Wagon Wheel

Wikipedia entry on the Wagon Wheel Effect