The Zöllner illusion is an
optical illusion
Within 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 v ...
named after its discoverer, German astrophysicist
Johann Karl Friedrich Zöllner
Johann Karl Friedrich Zöllner (8 November 1834, Berlin25 April 1882, Leipzig) was a German astrophysicist who studied optical illusions. He was also an early psychical investigator.
Biography
From 1872 he held the chair of astrophysics at Leip ...
. 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 ...
, editor of ''
Annalen der Physik und Chemie
''Annalen der Physik'' (English: ''Annals of Physics'') is one of the oldest scientific journals on physics; it has been published since 1799. The journal publishes original, peer-reviewed papers on experimental, theoretical, applied, and math ...
'', 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
The Wundt illusion is an optical illusion that was first described by the German psychologist Wilhelm Wundt
Wilhelm Maximilian Wundt (; ; 16 August 1832 – 31 August 1920) was a German physiologist, philosopher, and professor, known today as ...
appears. It may be that the Zöllner illusion is caused by this impression of depth.
This illusion is similar to the
Hering illusion
The Hering illusion is one of the geometrical-optical illusions and was discovered by the German physiologist Ewald Hering in 1861. When two straight and parallel lines are presented in front of radial background (like the spokes of a bicycle), ...
,
Poggendorff illusion,
Müller-Lyer illusion, and
Café wall illusion
The café wall illusion is a geometrical-optical illusion in which the parallel straight dividing lines between staggered rows with alternating dark and light "bricks" appear to be sloped, not parallel as they really are.
It was first described ...
. All these illusions demonstrate how lines can seem to be distorted by their background.
External links
A demonstration of the Zöllner illusion that allows for adjusting the angle of the shorter lines
References
Optical illusions
{{Optics-stub