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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
Metzgers (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 Germanys Gestalt
movement of the twentieth century, Metzgers
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 Metzgers
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)
Spillmanns 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, Spillmanns
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
Metzgers 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.
Spillmanns 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.
Metzgers 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 Herings
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 Metzgers 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 Turrells 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,
Metzgers 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).
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