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?

Click on the image to turn off the overlay, reverse the overlay, or to reset.

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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