The Zöllner illusion is an
optical illusion
In visual perception, an optical illusion (also called a visual illusion) is an illusion caused by the visual system and characterized by a visual perception, percept that arguably appears to differ from reality. Illusions come in a wide varie ...
named after its discoverer, German astrophysicist
Johann Karl Friedrich Zöllner. In 1860, Zöllner sent his discovery in a letter to physicist and scholar
Johann Christian Poggendorff
Johann Christian Poggendorff (29 December 1796 – 24 January 1877) was a German physicist born in Hamburg. By far the greater and more important part of his work related to electricity and magnetism. Poggendorff is known for his electrostatic mo ...
, editor of ''
Annalen der Physik und Chemie'', who subsequently discovered the related
Poggendorff illusion in Zöllner's original drawing.
One depiction of the illusion consists of a series of parallel, black diagonal lines which are crossed with short, repeating lines, the direction of the crossing lines alternating between horizontal and vertical. This creates the illusion that the black lines are not parallel. The shorter lines are on an angle to the longer lines, and this angle helps to create the impression that one end of the longer lines is nearer to the viewer than the other end. This is similar to the way the
Wundt illusion appears. It may be that the Zöllner illusion is caused by this impression of depth.
This illusion is similar to the
Hering illusion,
Poggendorff illusion,
Müller-Lyer illusion, and
Café wall illusion. All these illusions demonstrate how lines can seem to be distorted by their background.
References
External links
A demonstration of the Zöllner illusion that allows for adjusting the angle of the shorter lines
Optical illusions
{{Optics-stub