Laws of Seeing

by Wolgang Metzger, Translated by Lothar Spillman, Steven Lehar, Mimsey Stromeyer, and Michael Wertheimer
The MIT Press, Cambridge, MA, 2006
194 pp. illus. Trade, US$48; £30.95
ISBN: 0-262-13467-5.

Reviewed by Amy Ione
The Diatrope Institute

ione@diatrope.com

Originally published as Gesetze des Sehens (in 1936) and recently translated from German into English, Wolfgang Metzger’s (1899-1979) Laws of Seeing is a necessary addition to the library of anyone drawn to Gestalt Psychology. As a whole, the book demonstrates the degree to which perceptual phenomena influence studies of sensory physiology and our understanding of why we see the way we do. In this case, the analysis of ambiguous figures, hidden forms, camouflage, shadows and depth, and three-dimensional representations in paintings is so skillfully rendered that reading through the slim volume is fun in a way that belies its rigor and depth. This rigor is not the rigor of mathematics or psychophysics. Rather, Metzger is an experimenter who pays scrupulous attention to the details of his observations. Indeed, one of the fascinating aspects of Laws of Seeing is that the studies are not quantification but, instead, depend on pure perceptual research that is shared with us through drawings, photographs, and pictures. His examples let us "see" what he means when he speaks of dissolving typical ideas about scientific versus subjective points of view. This idea of blurring our sense of the observer in relation to the observed is clearly important to his thesis.

A leading figure in Germany’s Gestalt movement of the twentieth century, Metzger’s Laws of Seeing places the visual in the context of human experience. Using simple and testable demonstrations, the studies encourage the reader to grapple with the arguments using his or her own eyes. It is an interactive format, and the playful quality used to present the research aids Metzger in conveying his thesis that we do not decide what we see, and that the law of greatest order, or good Gestalt (prägnanz) means that stimuli will be perceived in a manner that is most regular, orderly, symmetrical, and simple. While most of the examples suggest that the organization of the visual array occurs essentially without our involvement, Chapter 11, where Metzger looks at motion, is an exception. Here he presents several examples of the influence of experience on vision. [This translation notes that the second edition included a chapter on motion perception that was absent from the first edition, which is the one the MIT published in this translation. That chapter, translated by Ulric Neisser, is available online at http://people.brandeis.edu/~sekuler/metzgerChapter/.]

One of the hardest aspects of the book for me to get a handle on was Metzger’s position on the relationship between physics and physiology. He opens Laws of Seeing by telling the reader that it deals almost exclusively with external objects, their forms and colors, their substance, and their behavior. Then, he notes that it is his intention to say little about the observer. Nevertheless, according to Metzger, the Laws of Seeing is not a physics book, but a book about human nature. It is only in the last chapter that he finally asks: "Are the laws of seeing psychological or physiological laws?" Answering this question, he sums up his position:

[W]e have proceeded exclusively and without a side glance into physics, chemistry, anatomy, and physiology, from within, from the immediate percept, and without even thinking of rejecting any aspect of our findings or even just changing its (sic) place, just because it does not fit with our contemporary knowledge of nature so far. With our perceptual theory we do not bow to physiology, but rather we present challenges to it. Whether physiology will be able to address these challenges, whether on its course, by external observation of the body and its organs, it will be able to penetrate to the laws of perception, is pointless to argue about in advance. (p. 197)

Spillmann’s introduction offers some insight here:

When discussing the physiological route, Metzger shies away from attributing the laws of seeing to the physiology of the eye because of the inadequacy of physiological explanations and the problem of overcoming the discrete (point-like) nature of the receptor mosaic, nerve fibers, and brain cells. Many years later, he would call this an Aporie, i.e., an unresolvable problem. He also shows convincingly that eye movements cannot bring about form vision, nor can shifts of attention. At the end of the book, Metzger exclaims that "We do not bow to physiology, but rather we present challenges." Although still true, this credo has changed in modern visual psychophysics as Gestalt concepts are being increasingly integrated into mainstream neuroscience by researchers proposing stimulus processing beyond the classical receptive field." (pp ix-x)

Indeed, Spillmann’s penetrating introduction, although brief, adds to the book immeasurably. As noted, Spillmann also helps to place Metzger in a larger sense and in terms of contemporary vision science. Also, in pointing out Metzger’s failure to reference original Gestalt thinkers (Max Wertheimer, Wolfgang Köhler, Kurt Koffka, etc), although he draws on their research, Spillman concludes that maybe political considerations were to blame. Many of the leaders of the Gestalt School were forced to flee Germany while Metzger stayed and continued his academic career during the Nazi regime. This conclusion is buttressed by the addition of these "missing" references to the expanded second (1954) and third (1975) editions, with the third edition dedicated to Max Wertheimer. Spillmann’s thought that it makes one wonder what course research into vision and perception might have taken had the Laws of Seeing been available to the English-speaking scientific community at the time of its writing is also noteworthy. Many of the ideas presented, for example in the fields of shape-from-motion, depth-from-shading, context dependency, and viewpoint invariance were re-discovered although the facts were already known several decades before.

I have always found that people are drawn to study vision on the basis of their own excitement about visual experience. Metzger’s own background seems, at least in part, to affirm this. Metzger had served on the front lines during World War I. He was hit by a grenade and the left part of his face was severely wounded. Although a French military surgeon tried to save his injured eye while he was a prisoner, the operation was unsuccessful. The eye was removed, and this trauma haunted him for the rest of his life. After the war, he returned to the university, where he had been a German Literature student. After enrolling in an introductory seminar presented by Wolfgang Köhler and Max Wertheimer, he revised his career path. The studies of perceptual problems, particularly perceptual constancy and contrast, fascinated the young student who then decided to study under these two men. A central feature in Metzger's career was his intense interest in monocular factors of depth perception. It seems the loss of his eye led him to wonder why his depth perception did not seem to be affected, since shortly before his entry into the military he had learned that depth perception is a function of the disparity between the images of the two retinae. This comes up early in the volume, when he mentions Hering’s hypothesis that the depth of binocularly seen objects is not mentally reconstructed on the basis of the two retinal images.

Finally, as a perceptual rather than a quantitative study, it is perhaps not surprising that Metzger’s approach brings to mind the intuitive searching for visual "tricks" that artists use as they move their work along. Several chapters in the book are related to traditional art. His discussions of brightness and spatial form extend to include how we see art and the devices artists use (e.g. shading) to render naturalistic images. The depth of perspective, brightness constancy and shape cues are also reviewed in terms of prägnanz. What I found particularly intriguing is that the type of perceptual process Metzger highlights is often associated with the Space and Light artists (e.g., James Turrell, Robert Irwin, Bruce Nauman, Eric Orr, Larry Bell, etc.) whose work with perceptual modalities took form late in the twentieth century. Ironically, before writing the Laws of Seeing Metzger discovered the perception of the homogeneous visual field (Ganzfeld). This work was so widely read that ganzfeld is now a generally accepted term, and many of James Turrell’s installations are Ganzfield pieces in which he floods interior spaces with colored light. Within these environments, viewers feel absorbed into dense, haze-like atmospheres of color.

Artists interested in perception are frequently drawn to the psychophysical arena to learn more about how their own intuitive perceptual sense works and perceive how/where their probing intersects with the actual workings of the eye. It would be fascinating to see whether Metzger would react similarly to the new techniques for studying vision if he were alive today. Regardless of where he would position himself now, this classic study on visual perception remains an astonishingly current work, although many of the ideas are dated. Spillmann points out that the underlying concepts remain cornerstones of vision research. Despite substantial advances in our understanding of the structural, functional, and computational properties of the brain, the study of perceptual phenomena remains the most solid basis for sensory physiology and for the understanding of how we see. Finally, Metzger’s sensitivity to our visual experience recommends the work. Given its accessibility and historical importance, this book will appeal to all in fields that intersect with vision and perception, (psychologists, biologists, neurophysiologists, and researchers in computational vision, artists, designers, and philosophers).