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![Adelbert Ames,
Fritz Heider and the
Ames Chair Demonstration
[continued | page 2 of 3]
by Roy R. Behrens](ChairDemo2_files/shapeimage_4.png)
![Del Ames was surely aware of the link between stellar constellations and his laboratory experiments. Among his constructions is a "star point demonstration," which consists of a light-tight box with three small star-like holes in front, each illuminated by a separate bulb within the box. By increasing or decreasing the illumination, Ames could make the three "stars" appear to be nearer or farther away (Ittelson 1968, 147-148).
Having studied optical physiology for more than three decades, Ames realized (as Helmholtz had in 1867) that an infinite variety of stimuli can produce the same retinal image. Thus, just as a limitless number of stars can produce the same constellation, it is theoretically possible to construct an infinite number of rooms, each uniquely distorted, which—providing we view them through designated peepholes—would result in the same retinal image as would a normal rectangular room.
Knowing this, Ames constructed at least one other laboratory-sized monocular distorted room. In that model, the distortion is vertical: Both the floor and ceiling are level and completely square, but the floor is one half the size of the ceiling, and all the walls are upended trapezoids, with the large end at the ceiling and the smaller sloping toward the floor (Ittelson 1968, 185).
Similarly, when he visited Ames in 1945, Heider realized that an infinite number of anamorphic wire models, none of which is actually a cube, can produce the same retinal image as would the presence of a real cube. "Obviously, the trick consists," as he explains in his autobiography, "in producing proximal stimuli which the distant [or distal] stimulus would ordinarily cause, and these stimuli can often be produced without having the object present" (Heider 1983, 141).
Heider believed that he influenced Ames by showing him his wire cube demonstration, which may or may not be the case. But it may be of parallel interest to note that Heider also was influenced. It is likely that his wire cube demonstration was inspired by experiments published in 1930 by Gestalt psychologist Herta Kopfermann, who had been Wertheimer and Kohler’s student at the Psychological Institute at the University of Berlin.
Kopfermann”s research, which is discussed and illustrated in Kurt Koffka’s Principles of Gestalt Psychology, includes three "projections of one and the same wire-edged cube," in Koffka’s words, "either of [which] could therefore be the retinal image of such a cube" (Koffka 1935, 159). They demonstrate that a single distal stimulus (which in this case might actually be a wire cube) can produce three dramatically different proximal stimuli (two-dimensional, three-dimensional, and spatially ambiguous) by slight changes in the observer’s point of view (that is, by shifting the peephole).
In Heider’s notebooks, there are repeated references to Kopfermann’s cube drawings, including the statement that "It is instructive to compare Kopfermann with Ames (or the cube demonstration)" (Benesh-Weiner 1988, 176).
Ames was "greatly pleased," according to Heider, when he was shown the wire cube demonstration in 1945. "When I visited him again in the fall," continues Heider, "he had constructed a very nice setup to demonstrate the effect that I described, but with one difference that he had introduced: he used a chair instead of a cube for the model of the object that would appear at a distance" (Heider 1983, 141).
The setup that Ames had constructed was a large wooden, covered box, five feet deep by four feet wide. Three identical peepholes are spaced equally on the front of the box, each fitted with a viewing lens. The observer is instructed to peer into each of the peepholes, with the result that in each case one experiences what appears to be a normal-looking chair. The three supposed chairs are of identical size, shape, and at the same distance from the peephole. However, when the lid of the box is removed, and the setup is examined from other points of view, it is obvious that only one of the objects is a miniature chair. The other two objects are extraordinary distortions: One is chair-like but dramatically stretched, while the other is a crisscross of seemingly unrelated wires and suspended wood pieces (Ittelson 1968, 170-173).
Having actually seen this demonstration (one of the originals has been archivally restored and is on public view at the Exploratorium in San Francisco), Gombrich writes that, for those of us who have seen only photographs of it, "what is hard to imagine is the tenacity of the illusion, the hold it maintains on us even after we have been undeceived [after the lid is removed]. We return to the three peepholes and, whether we want to or not, the illusion is there" (Gombrich 1961, 249).
This setup, which is usually called the Ames chair demonstration, is typical of Ames’s laboratory inventions. Virtually all require that the subject look through a designated monocular peephole, through which one witnesses a proximal stimulus (a retinal image) which appears to be that which would likely result from an identifiable common object, such as a chair, window, or room interior. However, when the setup is examined from other points of view, it is apparent that we have misjudged the proximal stimulus, and the distal stimulus is not at all as expected. More…](ChairDemo2_files/shapeimage_5.png)
![Everett L. Warner (Transactions of the Illuminating Engineering Society (1919)): “If a room were papered with a pattern of recurrent design, and if it were possible to take a photograph with a filter which would eliminate everything but the pattern, it would be quite possible to reconstruct the room from such a photograph and a piece of wallpaper.
Every change in the direction of the walls—every corner and projection—would all be indicated by an alteration in the apparent size and shapes of our units of pattern. When you have once thoroughly grasped this idea, marine camouflage holds no secrets for you.
You will realize that by changing the normal appearance of the pattern on one of walls—by distorting it, as it were—we could alter your visual impression of the wall. A regular pattern will have have the same appearance upon a curved surface as upon a flat surface, and if, upon the latter, we paint the pattern as it normal appears upon the curved surface we can give the illusion of a curving wall. This is exactly what was done on some of the [camouflaged] ships [during World War I, under Warner’s supervision].”](ChairDemo2_files/shapeimage_7.png)
![S. Howard Bartley
(A Bit of Human Transparency): “His [Ames’] core virtue was that he picked up and used some very fresh and new orientations with regard to visual perception. Although he became well acquainted with the principles of physiological optics, he looked upon perception from the organism-centered standpoint.”](ChairDemo2_files/shapeimage_16.png)
