Customs deception

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The Zöllner illusion is a visual perception illusion in which parallel lines appear alternately diverging or converging when they are crossed obliquely by short parallel lines.


Fig. 1. The parallelism of lines is apparently canceled by the hatching.

The deception is named after the astrophysicist Karl Friedrich Zöllner (1834–1882) and was published by him in 1860. Zöllner drew the parallel lines vertically (Fig. 1; today they are mostly shown in a 45 ° direction). Zöllner reports that he discovered the deception in a pattern intended for a fabric print. He submitted his work to the journal Annalen der Physik und Chemie , whereby the editor Johann Christian Poggendorff noticed the perception phenomenon named after him in the drawing .


Figure 2. Even without main lines, hatchings arranged in mirror image show the illusion effect.

The broad lines in Figure 1 seem to deviate from their actual vertical course. They appear alternately wider and narrower at the ends, the greater distance being observed at the end to which the hatched lines point. An effect is retained even if the hatch patterns are shifted relative to one another. The intensity of the illusion is also determined by the orientation of the stimulus and is somewhat stronger if the main lines are diagonal. It is most noticeable when looking at the entire stimulus and is observed even when the main lines are missing (Figure 2).

Attempt at interpretation

The acute angle between a hatch line and the main line is perceived as being enlarged. This effect is repeated at every intersection angle and, in total, leads to an apparent inclination of the entire main line.

Similar effects

The Orbison illusion and the Münsterberg illusion also show an apparent change in the inclination of lines compared to their actual course . There is a continuous change in inclination in the curvature of lines in a bundle of rays discovered by Wundt and in that by Hering.

Individual evidence

  1. F. Zöllner: About a new kind of pseudoscopy and its relation to the movement phenomena described by Plateau and Oppel. In: Annals of Physics. 186, 1860, pp. 500-525. doi: 10.1002 / andp.18601860712 .
  2. B. Lingelbach: The Zöllner deception & the Jastrow deception. 2013.
  3. M. Fineman: The Nature of Visual Illusion. Dover Publications, 1996, ISBN 0-486-29105-7 .
  4. ^ H. Münsterberg: The displaced chessboard figure. In: Journal of Psychology and Physiology of the Sensory Organs. 15, 1897, pp. 184-188.
  5. ^ E. Hering: Contributions to Physiology. Part I. On the theory of the local sense of the retina. Engelmann, Leipzig 1861.