window, and chair. These were called "equivalent configurations" by Ittelson (1952), defined as "configurations [in which] identical 'incoming messages' can come from different external physical arrangements. In the absence of other information,... equivalent configurations will be perceived as identical, no matter how different they be physically" (p. 55). Ames also developed the concept of "transactional ambiguity" holding that "mental set" or expectation could materially affect one's perception of visual and other stimuli, as with the Ames trapezoid. This hypothesis extended the impact of mental set from the widely believed impact on one's conclusions about stimuli (the eyewitness phenomenon) to actual perception of the stimuli itself. If true, it calls seriously into question the value of eyewitness reports even by individuals with no prejudices about their observations. In 1941 Ames began to make notes in the morning on his transactional analysis of perception. In 1960 his collaborator Hadley Cantril published an edited selection from these notes, with a Preface, and included Ames' correspondence with John Dewey. In 1954, Ames was awarded an honorary Doctor of Laws by Dartmouth. In 1955 he won the Tillyer Medal, awarded by the Optical Society of America. Ames died on July 3, 1955, and was buried at the Dartmouth Cemetery. His name, and that of his siblings, is also inscribed on the gravestone of his parents at the Hildreth family cemetery in Lowell. In the address given on the presentation of the Tillyer Medal, the president of the society listed 38 books and scientific papers Ames wrote, and 21 patents awarded to Ames. Publications in psychology 1946: "Binocular vision as affected by uniocular stimulus patterns in commonplace environments", American Journal of Psychology 59:333–57 1949: "Architectural Form and Visual Sensations", pages 82–91 in Building for Modern Man, edited by Thomas Creighton, Princeton University Press. 1949: (with Hadley Cantril, A. H. Hastorf & W. H.Ittelson) "Psychology and Scientific Research", Science 110: 461–4, 491–7, 517–22. 1950: Sensations, their Nature and Origin, Transformation 1: 11,2 1950: (with W. H. Ittelson) "Accommodation, Convergence and their relation to Apparent Distance", The Journal of Psychology 30:43–62. 1951: "Visual Perception and the Rotating Trapezoidal Window", Psychological Monographs 65(7): #324 1953: "Reconsideration of the Origin and Nature of Perception", in Vision and Action, edited by S. Ratner, Rutgers University Press 1955: An Interpretive Manual: The Nature of our Perceptions, Prehensions and Behavior Additional information Ames family papers Sophia Smith Collection, Smith College References Bibliography Behrens,