Ames Window Illusion

The Ames Window illusion from the 1940s still boggles minds today, and it’s basically an image on a flat piece of cardboard that seems to be a rectangular window but is, in fact, a trapezoid, with both sides of the piece of cardboard have the same image. The cardboard is hung vertically from a wire so it can rotate around continuously, or is attached to a vertical mechanically rotating axis for continuous rotation. When the rotation of the window is observed, the window appears to rotate through less than 180 degrees, though the exact amount of travel that is perceived varies with the dimensions of the trapezoid. It seems that the rotation stops momentarily and reverses its direction. It is therefore not perceived to be rotating continuously in one direction but instead is mis-perceived to be oscillating. Continue reading for two more videos and information.

The Ames Window was used in experiments to test this hypothesis by having subjects look through a pinhole to view the rotating window with a grey wooden rod placed through one pane at an oblique angle. Subjects were divided into two experimental groups; one told that the rod was rubber and the other that it was steel. The hypothesis held that there should be a statistically significant difference between these two groups; the steel group more often seeing the rod cutting through the pane while the rubber group more often saw it as wrapping around it. These experiments were popular in university experimental psychology courses, with results sometimes supporting the hypothesis while other times not.