Symmetry, Causality, Mind

by Michael Leyton, MIT Press,

Now available in paperback (April, 1999)

From the cover of the hard-back edition:

"Michael Leyton's arguments about the nature of perception are fascinating, exciting, and sure to be controversial. In this investigation of the psychological relationship between shape and time, Leyton argues compellingly that shape is used by the mind to recover the past and as such it forms a basis for memory. He elaborates a system of rules by which the conversion to memory takes place and presents a number of detailed case studies - in perception, linguistics, art, and even political subjugation - that support these rules.

"Leyton observes that the mind assigns to any shape a causal history explaining how the shape was formed. We cannot help but perceive a deformed can as a dented can. Moveover, by reducing the study of shape to the study of symmetry, he shows that symmetry is crucial to our everyday cognitive processing. Symmetry is the means by which shape is converted into memory.

"Perception is usually regarded as the recovery of the spatial layout of the environment. Leyton however shows that perception is fundamentally the extraction of time from shape. In doing so, he is able to reduce the several areas of computational vision purely to symmetry principles. Examining grammar in linguistics, he argues that a sentence is psychologically represented as a piece of causal history, an archaeological relic disinterred by the listener so that the sentence reveals the past. Again, through a detailed analysis of art, he shows that what the viewer takes to be the experience of a painting is in fact the extraction of time from the shapes of the painting."

From reviews of the book:

"This is a remarkable book. Its claim is that perception is none other than the recovery of causal history. One cannot but be struck by the depth, novelty, and brilliance of Leyton's accounts, page after page, of even the most minute and ordinary perceptual phenomena - claims which contradict virtually every previous treatment of these phenomena." Eleanor Rosch, Professor, University of California, Berkeley.

"Leyton's work is a most engaging and utterly original treatment of some of the classical problems in perception and cognition." Barbara Landau, Associate Professor of Cognitive Science, University of California at Irvine.

"This is a superb book. The writing is extraordinarily clear and the theory is very original. It challenges the reader to think about basic questions and presents new concepts and bold new principles that give a new perspective on visual perception in particular and cognitive representation more generally." Wayne Wickelgren, Professor, Psychology Department, Columbia University.

Professor Leyton is on the faculty of the psychology department at Rutgers University. His theory of the relation between shape and time has been applied in numerous disciplines, such as anthropology, art, radiology, meteorology, computer vision, chemical engineering, forensic science, linguistics, and philosophy. He has been awarded several important prizes (1987-1992, Presidential Young Investigator Award in Cognitive Science;1988, Medal of Achievement of the Society for Applied Systems Research). He is President of The International Society for Mathematical and Computational Aesthetics.

For ordering information on the book, at Amazon, click: Leyton's book at