Amodal Perception

The Ames demonstrations were not unprecedented, in the sense that they have much in common with an historic artistic distortion technique called anamorphosis, and to other perspective illusions employed in the design of theatrical sets. In anamorphic constructions, the image looks distorted when viewed frontally (as is customary) but correctly proportioned when seen from the side (often indicated by a peephole). For example, Ames was well acquainted with the work of scientist and philosopher Hermann von Helmholtz, who more than 50 years before had noted that an infinite variety of distorted rooms could be devised that, from a monocular peephole, would nonetheless seem to be normal. Far in advance of Helmholtz, this same kind of visual distortion was used as early as 1485 by Leonardo da Vinci (and probably even earlier by Chinese artists) as an offshoot of perspective. As early as the 16th century, a group of Dutch artists made anamorphic “peepshows” called perspectyfkas or perspective cabinets, a few of which still exist and are now on display in museums. These artistic constructions have much in common with the Ames distorted room, the chair demonstration, and the rotating trapezoid window. In fact, many of the Ames demonstrations make use of trapezoids that appear rectangular, tilted surfaces that appear to be flat, or flat surfaces that appear tilted. Most of the Ames demonstrations require (or at least work optimally with) a monocular peephole. This is because they rely on the fact that any number of external constructions could produce the same retinal image. Ames explicitly stated that (as Helmholtz had noted) he could have constructed an infinite number of distorted rooms, no two of which would have the same physical shape, yet each would appear to be normal. In the end, he only constructed a few.