The Zöllner Illusion
Variation 1

The pattern of lines in the background are perfectly straight and parallel. Do you see a distortion in the background lines where they go under the overlay?

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When scientists first studied this illusion more than 100 years ago, they began to suspect all human observations.

Credits: Johann Zöllner, 1860
Java Applet: ©1997 Tony Azevedo

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