The Poggendorff Illusion is an optical illusion that occurs when two straight and parallel lines are interrupted by a third line. When viewed, the two lines appear to be misaligned and curved, even though they are actually straight and parallel. This illusion was first described by Johann Karl Friedrich Z
The Poggendorff illusion is a geometrical-optical illusion that involves the misperception of the position of one segment of a transverse line that has been interrupted by the contour of an intervening structure. It is named after Johann Christian Poggendorff, the editor of the journal, who discovered it in the figures Johann Karl Friedrich Zöllner submitted when first reporting on what is now known as the Zöllner illusion, in 1860. Although Zöllner was focused on a different illusion, the misalignment of the diagonal lines revealed a distinct visual phenomenon. The Poggendorff illusion has become a widely studied example of spatial misperception in vision science and psychology. It has been used to investigate theories of perceptual systems, neurological function, and cognitive development.