The Illusion Behind Ames Room


Ames Room.

An Ames room is a distorted room that creates an optical illusion. Likely influenced by the writings of Hermann Helmholtz[citation needed], it was invented by American scientist Adelbert Ames, Jr. in 1946, and constructed in the following year.

An Ames room is viewed with one eye through a peephole. Through the peephole the room appears to be an ordinary rectangular cuboid, with a back wall that is vertical and at right angles to an observer’s line of sight, two vertical side walls parallel to each other, and a horizontal floor and ceiling. The true shape of the room, however, is that of a six-sided convex polyhedron: depending on the design of the room, all surfaces can be regular or irregular quadrilaterals so that one corner of the room is farther from an observer than the other. (See overhead view diagram to the right.)

Explanation About Ames Room.

The illusion of an ordinary room is because most information about the true shape of the room does not reach the observer’s eye. The geometry of the room is carefully designed, using perspective, so that, from the peephole, the image projected onto the retina of the observer’s eye is the same as that of an ordinary room. Once the observer is prevented from perceiving the real locations of the parts of the room, the illusion that it is an ordinary room occurs.

One key aspect of preventing the observer from perceiving the true shape of the room is the peephole. It has at least three consequences:

  1. It forces the observer to be at the location where the image projected into his or her eye is of an ordinary room. From any other location, the observer would see the room’s true shape.
  2. It forces the observer to use one eye to look into the room, preventing him or her from getting any information about the real shape the room from stereopsis, which requires two eyes.
  3. It prevents the observer from moving his or her eye to a different location, preventing him or her from getting any information about real shape of the room from motion parallax.

Other sources of information about the true shape of the room are also removed by its designer. For example, by strategic lighting, the true far corner is as bright as the true near corner. For another example, patterns on the walls (such as windows) and floor (such as a black-and-white chequerboard of tiles) can be made consistent with its illusory geometry.

The illusion is powerful enough to overcome other information about the true locations of objects in the room, such as familiar size. For example, although the observer knows that adults are all about the same size, an adult standing in the true near corner appears to be a giant, while another adult standing in the true far appears to be a dwarf. For another example, although the observer knows that an adult cannot change size, he or she sees an adult who walks back and forth between the true far and true near corners appear to grow and shrink.

Studies have shown that the illusion can be created without using walls and a ceiling; it is sufficient to create an apparent horizon (which in reality will not be horizontal) against an appropriate background, and the eye relies on the apparent relative height of an object above that horizon.




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