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Foot-Step Optical Illusion - Watch Video And Learn How It Works

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Foot-Step Optical Illusion Video

Video Credits: @AkiyoshiKitaoka

Nine rectangles, including 4 lighter yellow, and the other 5 dark blue, are moving continuously horizontally through vertical lines of white and black. 

Each rectangle has the exact dimensions as two stripes, meaning its back and front edges always share the same hue (black or white).

Anstis observed that the squares appear to accelerate and slow according to the local brightness.

If they are dark blue and are placed against white stripes, they have high contrast (dark contrast vs white) and seem to speed up for a short time. 

Suppose they are placed on black stripes, have low contrast (dark contrast vs black), and seem slow. This is not the case for the lighter yellow squares.

Therefore, the squares appear to move faster and slower as they move in a series, similar to walking feet; this is why it's called the "footsteps illusion." 

Because the difference drastically alters the speed that appears in real-time. 

For example, the two squares of each row appear to be alternating closer or further from each other, yet their actual distance remains the same.