MODULE 8

Gestalt Theories of Perceptual Organization

During the 1920's and 1930's Gestalt psychologists dominated the study of perception. Gestalt means form, configuration, or whole. The goal of Gestalt psychology, under the leadership of Max Wertheimer, Kurt Koffka, and Wolfgang Kohler, was to identify the ''natural" units of perception and to explain them in terms of a revised picture of how the nervous system works. While the search for the so-called natural unit still continues, and much of Gestalt neurological theory has been proven incorrect, these men have made a significant contribution to our understanding of perception through the systematic investigation`.of some fascinating phenomena.

As you read the text, keep the following questions in mind.

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FIGURE-GROUND

When you look at something you never see just the thing you look at; rather, you see it in relation to its surroundings. A word on this page is seen against the background of the paper. The page is seen against the background of your desk, and so on. In each case you distinguish between the figure or shape and the space surrounding it (called the background or ground). The Danish psychologist Edgar Rubin (1915, 1921 ) was the first to systematically investigate this phenomenon. He found that it was possible to see any well-marked area of the visual field as the figure, leaving the rest as the ground. In some instances, the figure and the ground may fluctuate. Thus, if in Figure 21 you consider the "faces" (dark part) as the figure, the "goblet" (light part) is the ground, and vice versa.

The importance of the figure-ground relationship lies in the fact that this early work by Rubin was the starting point from which the Gestalt psychologists began investigating what they called the organizing principles of perception.

GROUPING

It is not often that ambiguity is the starting point for a systematic investigation of a given phenomenon. The question of which shape will be perceived in an ambiguous figure such as Figure 21 inspired the Gestalt psychologists to investigate the variables that influence this perceptual discrimination.

Figure 21. A goblet or two faces? (After Rubin 1915)

The patterns shown on the left in Figure 22 below are all ambiguous. The Gestalt psychologists found that changing the patterns in various ways changes the ease with which each of the alternative arrangements of shapes can be seen. They then systematically studied the conditions which cause one form rather than another to be perceived.

A number of principles of organization or grouping emerged from the study of ambiguous stimuli. Three principles of grouping are summarized in Figure 23 -- similarity, closure, and proximity. Those stimuli which are "similar" will tend to be perceived as being together. Some figures force themselves on us as whole patterns, by the principle of "closure," even if there is a part missing, as in thne circle below. Those stimuli which are near each other are perceived as belonging together by the principle of "proximity".

Figures 22 and 23

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ILLUSIONS

An illusion exists when observations made with the help of physical instruments, such as a ruler, are different from those made without such instruments. The classic example of a distortion illusion is the MUller-Lyer arrow figures. (Figure 24)

This illusion has been investigated by psychologists for the past 100 years, and to date no theory has fully explained the phenomenon, despite the fact that the illusion is constant for almost all observers. Ipsen (1926) found that the perceived difference in line length in the Sander parallelogram (Figure 25) was even greater than that produced by the Muller-Lyer arrows.

Several other visual illusions concerned with how we perceive visual space are presented in Figure 26. Figure 27 illustrates how it is possible to make line drawings of "impossible" three-dimensional objects.

Figure 24. Muller-Lyer illusion. Note that llines A and B appear different in length; and that C and D appear different in length +

Figure 25. The Sander parallelogram. AB = BC (After Sander, 1926)

Figure 26. Optical illusions. In these illusions,

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Figure 27 Some impossible" objects

MOVEMENT

One of the most useful characteristics of our eyes is their ability to perceive motion. This ability provides us with much useful information about our environment. Our eyes tell us not only where objects are at present, but allow us to predict, from their speed and direction of travel, where they will be in the near future. Try to picture what would happen if you tried to walk down a busy city sidewalk at noon without this ability.

Generally speaking there are two kinds of movement that concern us -- real movement and apparent movement. Real movement is just that -- the displacement of objects in our environment. Understanding the variables involved in real movement is of particular importance in industry. When men work with machines that have exposed moving parts, safety dictates that the men must be able to determine their direction and speed of movement. In addition, detection equipment, such as me radarscope, must be constructed so that the visual display is within the threshold limits of the operators.

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When you look out of a car window, your eyes follow one moving point until it passes to the periphery of the retina, and then shift to fixate on another object which appears in the opposite periphery. This is called saccadic movement and is a combination of both eye pursuit and alternating kinesthetic movements similar to those involved in reading this module. In reading, your eyes follow a line to the end and return to pursue the next line. Eye pursuit and kinesthetic movements are the two most important factors in the perception of real movement.

Gestalt psychologists have done extensive research on apparent movement. We have all seen neon signs and other illuminated displays where lights flash in sequential order; we see movement but nothing is moving. This is known experimentally as the phi phenomenon and was a major research interest in psychology for many years. In an experimental situation, lights are arranged in a manner similar to that illustrated in Figure 28. When one flash follows another at the appropriate interval, you see the light move from one position to another. This interval depends on the distance between the lights, their size, and their brightness.

The phi phenomenon is not dependent on eye movement, since the apparatus can be adjusted so that an observer experiences apparent movement in both directions simultaneously. Some evidence suggests that this illusion is caused by a stereotyped reaction of the visual receptors or of the central nervous system, or perhaps some combination of the two.

Figure 28 Phi-phenomenon apparatus

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MODULE 8
PROGRESS CHECK 1

Now test yourself without looking back.

Which of the following were goals in the study of perception by Gestalt psychologists?
a. To identify the "natural" units of perception
b. To develop ambiguous stimuli
c. To explain "natural" units in terms of a revised picture of how the nervous system works

2. (Drawing of goblet/ladies figure ground This drawing illustrates:

a. an ambiguous stimulus.
b. a figure-ground relationship.
c. (neither)

4. Which principle of grouping is illustrated by this drawing?

0000 0000

_____________________________________

5. Which principle of grouping is illustrated by the organization below?

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6. Whenever observations made with the aid of physical instruments differ from those made without such aid, we have a(n) _______________________________________

7. What are the two most important factors in perception of real movement?___________________

8. When lights flash in sequential order and we see movement, we are experiencing the _________________________________

ANSWER KEY PAGE 144

7 OR MORE CORRECT UNIT TEST
FEWER THAN 7 CORRECT PAGE 138

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MODULE 8
EXERCISES

Write the principle of grouping illustrated by each of the following:

a . Circle with gap in it

b.
+ - + - +
+ - + - +
+ - + - +

c. Triangle with gap

d.
+ + +
+ + + ______________________________________4

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Gestalt psychology deals with organization of forms. Which of the grouping principles is (are) involved in Gestalt psychology?

__________________________________________________________3

Whenever we observe an object we also see its background. For example the face-goblet figure can be seen as two faces, in which case the goblet shape is the background. This is called a(n):
a. figure-ground relationship.
b. grouping principle.
c. ambiguous figure.
____________________________________________________ 2

The two horizontal lines above represent an optical illusion. These lines are the same length when measured with a ruler, but one is perceived as shorter. An illusion exists, therefore,when measurement with a physical instrument __________________________________1

ANSWERS

1 differs from that without an intrument.
2 a, c
3 all of them
4
a. closure
b. similarity
c. closure
d. proximity


We perceive both real and apparent movements. Two important factors in the perception of real movements are eye pursuit and kinesthetic movements. How we perceive real movement is useful in work with:
a. illusions.
b. machines.
c. ambiguous stimuli.
_________________________________________________ 3

Lights can be arranged and flashed so that an observer perceives a light to be moving. The phi-phenomenon apparatus is used for Stratton of the experimentation with this type of movement, which is called_____________________________________________________2

Which of the following are the most important factors in the perception of real movement?
a. Eye pursuit
b. The phi phenomenon
c. Kinesthetic movement
d. Apparent movement
___________________________________________________ 4

A neon sign frequently shows apparent movement. This is a demonstration of the ___________________________1

NOW TAKE PROGRESS CHECK 2 ANSWERS

1 phi phenomenon
2 apparent movement
3 b
4 a c

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MODULE 8
PROGRESS CHECK 2

1. What are Gestalt psychologists interested in?_____________________________________________

2. An ambiguous stimulus such as the goblet-faces picture illustrates the:
a. figure-space relationship.
b. figure-ground relationship.
c. first principle of grouping.
d. (none of these)

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5. Three common principles of grouping are:_____________________________________________________________

6. We perceive real movement by means of:
a. eye pursuit.
b. kinesthetic movements.
c. (neither)

7. When does an optical illusion exist?
_______________________________
8. What is a phi-phenomenon apparatus used for?__________________________________________________

ANSWER KEY PAGE 144

UNIT 6 Table of Contents

7 OR MORE CORRECT TAKE UNIT TEST

FEWER THAN 7 CORRECT CONFERENCE

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