The Hering illusion, an optical illusion discovered by the German physiologist Ewald Hering in 1861, consists of two vertical lines which are both straight, but they look as if they are bowing outwards. The distortion is produced by the lined pattern on the background, which simulates a perspective design, and creates a false impression of depth.

This illusion looks like bike spokes around a central point, with vertical lines on either side of this central point, called the vanishing point. The illusion tricks us into thinking that we are moving forward. Since we aren't actually moving and the figure is static, we misperceive the straight lines as curved ones.