Optical illusions have been found in cave paintings, so an optical illusion is not considered an invention but instead is the result of man imitating the geometric forms seen in nature through architecture and art. Arab astronomer Alhazen wrote about the optical illusions in the sky in the 10th century.
Johann Oppel conducted one of the earliest investigations on optical illusions in 1854. The Oppel-Kundt illusion is a geometric model in which a set distance, separated by a graduation of lines, looks longer than the same distance without the lines. The illusion caught the scientist's attention, after he noted recurring errors in his students' sketches.
Although the phrase "optical illusion" suggests that it is a visual phenomena, it is actually caused by the brain's interpretation of these images.