Jastrow Illusion

The Jastrow illusion is an optical illusion attributed to the Polish-American psychologist Joseph Jastrow, also known by several other names including the Ring-Segment illusion, the Wundt Area illusion, the Wundt-Jastrow illusion, and the Boomerang illusion. In its classic demonstration, two identical curved, boomerang-shaped figures, such as two toy railway tracks, are placed one above the other, and although the two figures are exactly the same size, the lower one consistently appears larger than the upper one. Researchers have proposed three competing theories to explain why the illusion occurs, and the effect has found its way into everyday novelty use, appearing in magic kits and being sold in magic shops under the name Boomerang illusion.