1) Optical illusion
Found on
https://www.crosswordclues.com/clue/hering-illusion
The Hering illusion is a 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), the lines appear as if they were bowed outwards. The Orbison illusion is one of its variants, while th...
Found on
http://en.wikipedia.org/wiki/Hering_illusion
No exact match found.
