Source: Laboratory of Jonathan Flombaum—Johns Hopkins University

The most difficult challenge of visual perception is often described as one of recovering information about three-dimensional space from two-dimensional retinas. The retina is the light-sensitive tissue inside the human eye. Light is reflected from objects in the world, casting projections on the retina that stimulate these light sensitive cells. Objects that are side-by-side in the world will produce side-by-side stimulations on the retina. But objects that are more distant from the observer cannot produce more distant stimulations, compared to nearby objects that is. Distance-the third dimension-is collapsed on the retina.

So how do we see in three dimensions? The answer is that the human brain applies a variety of assumptions and heuristics in order to make inferences about distances given the inputs received on the retina. In the study of perception, there is a long tradition of using visual illusions as a way to identify some of these heuristics and assumptions. If researchers know what tricks the brain is using, they should be able to trick the brain into seeing things inaccurately. This video will show you how to build an Ames Room, a visual illusion that illustrates one of the assumptions applied by the human visual system in order to recover visual depth.

1. Materials

1. To build an Ames Room you will need four pieces of cardboard, each 1-ft high. The four pieces should vary in length, including a 2-ft piece, two 1-ft pieces, and one piece that is 1.5-ft long.
2. You will also need two figurines of some kind, action figures, toy soldiers, even stuffed animals will do the the trick. The two should be roughly the same height and shorter than ¾-ft tall.
3. A box cutter and glue or tape will also be necessary.

2. As

What do you see when you look into the Ames Room? Figure 3 schematizes the effect-the figurine on the right should look much larger than the one on the left, even though you know they are the same size.

Figure 3: Schematic representation of what people see in the Ames Room, compared to the fact of the matter, i.e., wha

Understanding how humans perceive the visual world in 3D has been a major area of research focus and a major achievement of the modern study of perception. Some of the important applications that have arisen, as a result, are in the development of 3D and virtual reality viewing technology. The Ames Room specifically has been used for a long time in the movies, as a sort of special effect. Suppose a movie needs to depict a giant, or someone very small. Shooting interior scenes inside an Ames Room can produce the illusion