The Orbison illusion (or Orbison's illusion) is an

optical illusion Within visual perception, an optical illusion (also called a visual illusion) is an illusion caused by the visual system and characterized by a visual perception, percept that arguably appears to differ from reality. Illusions come in a wide v ...

first described by American psychologist William Orbison (1912–1952) in 1939. The illusion consists of a two dimensional figure, such as a

circle A circle is a shape consisting of all points in a plane that are at a given distance from a given point, the centre. Equivalently, it is the curve traced out by a point that moves in a plane so that its distance from a given point is const ...

square In Euclidean geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles (90-degree angles, π/2 radian angles, or right angles). It can also be defined as a rectangle with two equal-length a ...

, superimposed over a background of

radial line A cylindrical coordinate system is a three-dimensional coordinate system that specifies point positions by the distance from a chosen reference axis ''(axis L in the image opposite)'', the direction from the axis relative to a chosen reference d ...

s or concentric circles. The result is an optical illusion in which both the figure and the rectangle which contains it appear distorted; in particular, squares appear slightly bulged, circles appear elliptical, and the containing rectangle appears tilted.

References

* * Optical illusions {{psych-stub