Barber pole illusion

The rotation of the axis is perceived as a movement of the strips vertically or 45 ° upwards

The barber pole illusion is an optical illusion of perceived movement.

The barber-pole illusion is one of the most famous movement illusions. It takes its name from the bars painted with blue and red diagonal stripes that can be found in front of many hair salons in the USA. It is triggered by the rotation of a vertical cylinder provided with helical strips . The observer does not perceive this as a purely horizontal movement, but rather interprets it, depending on the direction of rotation, as if the stripes were moving up or down.

The aperture problem states that in the case of homogeneous lines which move within an otherwise empty field, their movement is always perceived as running perpendicular to their line orientation. In the barber pole illusion, however, the lines are not continued horizontally, which means that there is no straight line orientation, but rather they are bent backwards around the roll. The appearance of a movement of the strips by 45 ° upwards therefore only occurs when viewing a section, instead a vertical movement of the strips along the axis can be perceived.

Individual evidence

1. ↑ Vilayanur S. Ramachandran & Diane Rogers-Ramachandran: Caution, Wrong Direction . In: Brain & Mind . No. 4/2009 . Spectrum of Science , ISSN  1618-8519 , p. 62 .
2. ^ Manfred Fahle: Visual illusions . In: Hans-Otto Karnath & Peter Thier (eds.): Neuropsychology . 2nd Edition. Springer Medizin Verlag , Heidelberg 2006, ISBN 3-540-28448-6 , chap. 6 ( p. 73, online [accessed December 17, 2011]).