Poggendorf Illusion
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The Poggendorff Illusion is an optical illusion that involves the brain's perception of the interaction between diagonal lines and horizontal and vertical edges. It is named after Johann Poggendorff, who first described it in 1860.
In the picture to the left, a straight black line is obscured by a red rectangle. The black line appears disjointed, although it is in fact straight; the second picture illustrates this fact.
External links
- Poggendorf Illusion (http://www.cut-the-knot.org/Curriculum/Geometry/Illusion.shtml)
- Circular Poggendorf Illusion (http://www.cut-the-knot.org/Curriculum/Geometry/CircularPoggendorf.shtml)
- Poggendorf Illusion (http://epsych.msstate.edu/descriptive/Vision/Poggendorf/pog02.html)
- Explanation of the Poggendorff, Hering, and Zoellner illusions (http://www.enane.de/ontoform.htm)