[visionlist] Walter Gogel

[John Foley]

WALTER CHARLES GOGEL  (1918-2006)

         Walter C Gogel, Professor Emeritus of Psychology at the 
University of California, Santa Barbara (UCSB), died in Santa Barbara 
on October 20, 2006 at the age of 88, after a long and distinguished 
career.  He was born in New Jersey in 1918.  As a young man, Gogel 
served in WW II as a radar technician in the U.S. Army.  After army 
service, he went to Marietta College, where he majored in physics and 
psychology and graduated magna cum laude in 1948.  Three years later 
he received the Ph. D. in Psychology from the University of 
Chicago.  From 1951 to 1965 he was a research psychologist first at 
the U. S. Army Medical Research Laboratory at Fort Knox, Kentucky, 
and later at the Civil Aeromedical Research Institute in Oklahoma 
City, Oklahoma.  In 1965 he became Professor of Psychology at UCSB, 
where he taught until his retirement in 1989 and continued to be 
active in research for several more years.

         At the University of Chicago, Gogel began working with Louis 
Thurstone, who was using mathematics to develop methods for 
psychological measurement, but he switched early on to work with 
Eckhard Hess on visual perception in chicks.  This led him to his 
lifelong study of visual perception in humans focusing primarily on 
the perception of space and motion.  Throughout his career, his 
primary concern was with understanding perceptual experience, and he 
embraced phenomenology as a starting point for the study of space 
perception.  Indeed, many of his discoveries of perceptual phenomena 
and many of his ideas about perception came from his being 
exquisitely attentive to his own experience.  However, he was wary of 
relying exclusively on the phenomenological reports of his subjects 
and thus was motivated to develop non-verbal and indirect measures of 
perceptual experience, which he favored in cases where the two types 
of measures did not agree.

         In the field of space perception Walter Gogel was unexcelled 
as an experimentalist. During his early career, his focus was on 
phenomena of perceptual organization, phenomena in which the elements 
of a stimulus combine to produce a percept that is often quite 
different from the percepts evoked when the elements of the stimulus 
are presented one at a time. He started his career with very simple 
stimuli (one light in a dark room) and moved systematically to more 
and more complex stimuli.  He got verbal reports of distance, but he 
corrected the subjects' verbal reports of distance to take account of 
their different memories of the measuring unit.  He introduced 
several new measures of perceived extents, which included measuring 
distance by having subjects lean into a lighted "full-cue" alley and 
throw darts to the perceived distance of the target and by using hand 
separation to measure small extents.  Later he developed an indirect 
method in which an observer moves his head left and right while 
viewing visual targets and indicates the perceived left-right motion 
of the targets. Gogel showed how this perceived motion could be used 
to compute a relatively pure measure of perceived distance.

         Early in his career Gogel realized the complexity of space 
perception. He measured the perceived distance to a single light in a 
dark field and he showed that when a second light is introduced at a 
greater distance, the perceived distance of the first light 
decreases.  This led Gogel to make a sharp distinction between 
absolute and relative cues to distance, absolute cues being those 
that provide information about distance from oneself and relative 
cues those that provide only information about the relations between 
distances, for example, that one distance is two times another.   The 
convergence of the eyes to fixate a point is a good example of an 
absolute cue, and binocular disparity, the difference in the images 
in the two eyes when a 3-D scene is viewed, a good example of a 
relative cue.  Gogel asked how absolute and relative cues combine to 
determine the perceived distances of all the objects in a scene.  His 
answer was that relative cues, since they carry information only 
about relative distance, cannot determine absolute 
distances.  Relative distances are scaled by absolute cues and the 
Specific Distance Tendency. These determine the absolute distance to 
one point, which, together with the relative cues, provides the basis 
for computing the absolute distances of all the other points in the 
scene. Gogel and others have produced many experimental results that 
are consistent with this view.

         Gogel applied this same approach to motion perception.  It 
was already known that, if a static object is surrounded by a moving 
frame, the static object will appear to move in a direction opposite 
to the frame.  Gogel showed that this phenomenon generalizes to 
configurations of several points moving in different directions and 
that the perceived path of an object depends on the motions of other 
objects in its vicinity.

         Gogel's measurements of the perceived distance of a single 
object viewed in dark surroundings showed that it differs 
systematically from its physical distance.  Near objects appear 
farther than they are and far objects appear nearer than they 
are.  He hypothesized that there is a process independent of the 
stimulus that pulls the perceived distances toward a specific 
distance of about 2 meters (the Specific Distance Tendency).  When 
the field contains multiple objects, a second factor comes into play: 
the objects are more similar in perceived distance than would be 
expected on the basis of the relative cues (the Equidistance 
Tendency).   The Specific Distance Tendency affects absolute 
distance, while the Equidistance Tendency affects relative distance. 
Thus, in Gogel's view there are two kinds of factors, cues and 
tendencies, and two kinds of each, absolute and relative.  Where an 
object appears to be depends on the positions indicated by each of 
the cues present, and the relative strengths of these cues and the 
two tendencies.  He found that the strength of the relative factors 
increased as the distance between objects decreased (the Adjacency Principle).

         Although the major cues to distance had been discovered 
before Gogel's time, he did an extensive series of experiments to 
determine which of them were effective as cues to absolute distance 
and which to relative distance.  He was led to challenge commonly 
held views about some of the cues.  Familiar size is the best 
example.  It was widely held that if an observer knew the size of an 
object, the object would be perceived to be its familiar size and 
that the product of perceived size and the visual angle of the 
retinal image would determine its perceived distance (the 
size-distance invariance hypothesis).  Consistent with this, 
experiments had shown that, if all cues except the physical size of 
an object were eliminated, people report that perceived distance 
increases as image size decreases.  Gogel did such an experiment 
using transparencies of playing cards, but he had subjects judge the 
perceived size as well as the perceived distance.  The distance 
judgments followed the usual pattern, but subjects did not judge the 
cards to be of the same size.  Perceived size was reported to vary 
with image size.  This led Gogel to doubt that the reported perceived 
distances were accurate measures of perceived distance, and to 
propose that they were cognitive judgments based on the familiar 
experience that distant objects look small.  Gogel introduced his 
head motion procedure to obtain purer measures of perceived 
distance.  He found that there was at most a very small change in 
perceived distance when the image size of a familiar object 
changes.  He later used this same analysis to explain reports that 
the moon appears both large and close when it is near the horizon.

         Gogel came to view perception as arising from the resolution 
of unavoidable conflicts between absolute cues, relative cues, and 
tendencies in the visual system.  He provided much evidence that the 
resolution of these conflicts depends on the relative strengths of 
the competing factors and that the solution is a weighted average of 
the perceptions that would be produced by each factor alone.  He 
showed that the relative strengths of the factors vary continuously 
with the adjacency of objects, and he proposed that strength also 
co-varied with the precision of the factor.  The same analysis 
applies to cases where cues are deliberately put in conflict.  It 
accounts for several illusions including those occurring in the Ames' 
room and provides the basis for predicting new illusions.  Most of 
his work was concerned with size and distance, but he showed that 
these same ideas account well for the perceived path of the motion of 
a point when one or two points are moving relative to it.

         Besides being a superb experimentalist, Gogel gradually 
emerged as one of the field's major theorists.  His most important 
theoretical contribution is his article presenting "a theory of 
phenomenal geometry" published in 1990 at the age of 72.  This theory 
grew out of his earlier work on percept/percept relations, most 
notably his important elucidation of "apparent concomitant motion", 
which refers to perceived motion seen in stationary objects when the 
observer's head moves through space.  A familiar example occurs when 
one views an inverted facial mask while moving side to side.  The 
mask is often misperceived as facing the observer and turning as the 
observer moves. In a number of important papers in the 1970s and 
1980s, he showed conclusively that apparent concomitant motion occurs 
primarily when distance is misperceived while direction and the 
movement of one's own head are perceived correctly.   He eventually 
extended his analysis of perceived motion to the general case of 
stationary and moving stimuli viewed with the stationary and moving 
head (including motion in the sagittal plane).  His 1990 paper 
presenting a theory of phenomenal geometry was the final and most 
developed expression of his approach, for it provided an account of 
how the factors of perceived visual direction, perceived distance and 
depth, and the sensed movement of the head could account for the 
derived perceptual variables of size, orientation, shape, and 
motion.  With the development of this theory of phenomenal  geometry, 
he had moved from his earlier concern with how sensory cues and 
internal tendencies act as constraints on the mapping from physical 
to perceptual space to a greater concern with the relations of the 
perceptual dimensions of visual space, relations that act as 
fundamental constraints on the physical-perceptual mapping.

         Walter Gogel became a world leader in the field of space 
perception early in his career and subsequently influenced many other 
leading researchers.  He authored more than 100 scientific articles, 
which are frequently and widely cited.  He was active in research 
late into his seventies and, well after that, took great delight in 
talking about space perception with anyone who was interested.  He 
mentored some excellent researchers who continue to pursue the 
approach that he developed.  Numerous scientists visited his 
laboratory, where he was always prepared to demonstrate his latest 
perceptual discovery.  He was for many years consulting editor of the 
journal Perception and Psychophysics.
--------------------
         It was our great fortune to have Walt Gogel as a colleague 
and friend for many years.  We have never met anyone with a deeper 
interest in or more intense focus on science than Walt.  He loved to 
think about and do research on perception, and his passion was 
contagious for us all.  He had a deep understanding of 
perception.  During his career, he developed some strongly held views 
and was never one to shy away from argument.   Yet, while arguing his 
position, he was always gracious and good natured, and whether we 
agreed with him or not, we always learned something. He made very 
substantial contributions to the science of perception that will have 
lasting importance.  We will remember him with great fondness and respect.

         Although Walt did not often talk about his life outside the 
university, it was a full life.  From early childhood he participated 
in sports and became an expert gymnast.  Until he was well into his 
seventies, he worked out almost daily at a gym and was admired for 
his strength.  Walt loved nature.  He and his family traveled and 
camped throughout the United States, visiting almost all of the 
national monuments.  He had a tender heart for animals, which he 
expressed in his care of the many dogs that he had during his 
life.  He was a very loyal, kind, good-natured, and deeply 
philosophical man.  Walt leaves Nancy, his devoted wife, constant 
companion and supporter for more than 50 years, three children, 
Howard, David, and Susan, and two grandchildren.


John Foley
Jack Loomis
Donald Mershon
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