格式塔疗法的基本原则Gestalt principles

Gestalt principles

DejanTodorovic (2008), Scholarpedia, 3(12):5345.

doi:10.4249/scholarpedia.53 45

revision #91314 [

link to/cite this article

]

Post- publication activity

Curator:

Dejan Todorovic

?

Prof. Dejan Todorovic

, Laboratory of Experimental Psychology, Department of Psychology, University of Belgrade, Belgrade, Serbia

Gestalt principles

, or gestalt laws, are rules of the organization of perceptual scenes. When we look at the world, we usually perceive complex scenes

composed of many groups of objects on some background, with the objects themselves consisting of parts, which may be composed of smaller parts,

etc. How do we accomplish such a remarkable perceptual achievement, given that the visual input is, in a sense, just a spatial distribution of variously

colored individual points? The beginnings and the direction of an answer were provided by a group of researchers early in the twentieth century,

known as Gestalt psychologists. Gestalt is a German word meaning 'shape' or 'form'. Gestalt principles aim to formulate the regularities according to

which the perceptual input is organized into unitary forms, also referred to as (sub)wholes, groups, groupings, or Gestalten (the plural form of Gestalt).

These principles mainly apply to

vision

, but there are also analogous aspects in auditory and somatosensory perception. In visual perception, such

forms are the regions of the visual field whose portions are perceived as grouped or joined together, and are thus segregated from the rest of the visual

field. The Gestalt principles were introduced in a seminal paper by Wertheimer (1923/1938), and were further developed by K?

hler (1929), Koffka

(1935), and Metzger (1936/2006;

see review by Todorovi?, 2007). For a modern textbook presentation, including more recent contributions, see

Palmer (1999).

Contents

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1 Figure-ground articulation

2 Proximity principle

3 Common fate principle

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4 Similarity principle

5 Continuity principle

6 Closure principle

7 Good gestalt principle

8 Past experience principle

9 Auditory Gestalten

10 Contemporary work

11 Unresolved issues

12 References

13 Recommended reading

14 External links

15 See also

Figure-ground articulation

Figure 1: Figure-ground articulation.

If the visual field is homogeneous throughout, a situation labeled as Ganzfeld (German for 'whole field'), it has no consistent internal organization. A

simple case of an inhomogeneous field is a display with a patch of one color surrounded by another color, as in Figure

1

.

In such cases the visual field is perceived as articulated into two components, the

figure

(patch) on the

ground

(surround). This

figure-ground

articulation

may seem obvious, but it is not trivial. This type of field organization has a number of remarkable features, first described in the work of

Rubin (1915/1921), predating Wertheimer's publication. The two components are perceived as two segments of the visual field differing not only in

color, but in some other phenomenal characteristics as well. The figure has an object- like character, whereas the ground has less perceptual saliency

and appears as 'mere' background. The areas of the figure and the ground usually do not appear juxtaposed in a common plane, as in a mosaic, but

rather as stratified in depth: there is a tendency to see the figure as positioned in front, and the ground at a further depth plane and continuing to

extend behind the figure, as if occluded by it. Furthermore, the border separating the two segments is perceived as belonging to the figure rather than

to the ground, and as delineating the figure's shape as its contour, whereas it is irrelevant to the shape of the ground. Certain displays are bi- stable, in

that what is perceived as figure can also be perceived as ground and vice- versa. However, in displays structured such as Figure

1

, in which a smaller

region is wholly surrounded by a larger region, it is usually the former that appears as figure (although it may also be seen as a hole), and the latter as

ground.

The described organization of the display into the figure and the ground is not its only conceivable segmentation. To illustrate this, consider that

Figure

1

, as presented on the computer screen, is a set composed of a certain number of pixels, and that the segmentation into figure and ground

corresponds to a particular partition of this set into two subsets. However, this same set may be partitioned into a huge number of other pairs of

subsets (such as the subset of pixels in the left half of the figure and the subset in the right half, or the subset at one side of any arbitrary line

meandering through the display and the subset at the other side, or the subset consisting of even pixels in odd rows plus odd pixels in even rows and

the complementary subset), or into any conceivable three subsets, or four subsets etc. Nevertheless, while an enormous number of such alternative

partitions are conceivable, none of them is perceivable, save one or very few. The partition that is actually seen is not a matter of geometric

combinatorics and

attention

to arbitrarily selected subsets: the natural, and often the only way that we can perceive such a display, given the structure

of the visual input, is as segmented into the figure and the ground. Such articulation, in which a virtual infinity of geometrical possibilities is pruned

down to a single or only a couple of perceptual realizations, is a very basic feature of the working of the visual system.

Although

figure-ground perception

is a fundamental aspect of field organization, it is not usually itself referred to as a Gestalt law or principle of

grouping. Rather, such terms are mostly used for describing the rules of the organization of somewhat more complex visual fields. There is no

definitive list of Gestalt principles, but some of the most commonly discussed are listed and described below, illustrated with examples mainly based

on Wertheimer (1923/1938) and Metzger (1936/2006). As demonstrated by these examples, the perceptual groupings are in some cases strong and

unambiguous, but in other cases they are better described as tendencies, especially when different factors compete with each other.

Proximity principle

Figure

2

a contains six patches,each of which is perceived as a visual unit, a figure on a common ground. However, they are also collectively the

elements of a higher-order visual unit, the horizontal row. According to Gestalt theory, this type integration of individual components into a

superordinate whole can be accounted for by the

proximity principle

: elements tend to be perceived as aggregated into groups if they are near each

other.

Figure 2: Proximity principle.

The effect of varying proximity is illustrated in Figure

2

b. Due to the change of distance between some of the components, here the patches are

perceived not just collectively as a sextuple, but also as being subdivided into a triple of doublets, an organization that in Wertheimer's notation is

designated as 12/34/56.

Note that a number of other potential partitions of the set in Figure

2

b exist, such as into a doublet of triples (123/456), or into a quartet and a pair

(1234/56), or even into combinations of non-adjacent items such as 16/25/34/, or 135/246 etc. However, it is extremely hard, if not impossible, to

actually

perceive

groupings of patches other than 12/34/56 in this figure. On the other hand, it is not impossible to see some subdivisions in Figure

2

a.

For example, with deliberate effort and concentrated attention one may eventually succeed in mentally partitioning the row of patches into three pairs.

However, such a percept is usually only partially and locally successful (one clearly sees only one or two segregated pairs), appears contrived, and is

fleeting. In contrast, perceiving the same partition in Figure

2

b is spontaneous and effortless, and the percept is global and

stable

. Attention may

contribute to figural perception, but, except in special cases, its role is usually limited: generally, it is not attention that creates the forms, but rather

the forms, organized in accord with Gestalt principles, that draw attention.

With a different spatial distribution of the six components, such as in Figure

2

c, another naturally perceived partition into sub-wholes arises, denoted

as 1/23/45/6. The partition 12/34/56, although arguably simpler and more regular, is hard to perceptually realize in Figure

2

c: it would violate the

proximity principle, as it would involve grouping together some elements across relatively larger distances, but assigning other, relatively near

elements, into different groups.

Common fate principle

The

common fate principle

states that elements tend to be perceived as grouped together if they move together. Thus if some of the elements in

Figure

2

would begin to displace they would be perceived as a group, even across larger distances. This is shown in Figure 3, in the following manner.

If you move the cursor within the area of this figure, some of the patches will move up some distance, and if you then click on the left mouse button,

they will move down. Repeatedly pressing and releasing the left mouse button provides a simple demonstration of the grouping power of the common

fate principle.

Similarity principle

The

similarity principle

claims that elements tend to be integrated into groups if they are similar to each other. It is illustrated in Figure

3

a-e, in

which proximity is held constant, since the individual figures are at (approximately) the same distance from each other, as in Figure 2a. Nevertheless,

they are perceptually partitioned into three adjacent pairs, due to the similarity of visual attributes such as lightness (Figure

3

a), color (Figure

3

b), size

(Figure

3

c), orientation (Figure

3

d), or shape (Figure

3

e).

Figure 3: Similarity principle.

The 12/34/56 partition becomes more salient when the within-group similarities and between-group differences are compounded, by making the

doublets similar / different in more than one visual attribute ( Figure

3

f). An important manipulation, studied already by Wertheimer (1923), is to vary

both similarity and proximity, in order to investigate their joint effects on perceived groupings. Note that by increasing the distance between elements

2 and 3, and elements 4 and 5 (as in Figure

2

b), the salience of the 12/34/56 organization is strengthened (Figure

3

g), since similarity and proximity

co-operate by favoring the same organization. On the other hand, when the inter-element distances are changed as in Figure

2

c, the resulting

perceptual organization, Figure

3

h, is less clear, because similarity still favors partition 12/34/56, but proximity favors partition 1/23/45/6. This type

of manipulation can thus be used to quantify the effects of different Gestalt principles and compare their strength.

Continuity principle

The display in Figure

4

a can be described as consisting of a number of elements arranged in three sub-wholes or branches, converging at X. According

to the principle of proximity, one would expect branch BX to group with branch CX, but instead it groups with branch AX, forming the sub-whole AXB.

Figure 4: Continuity principle.

This grouping is an instance of the

continuity principle

: oriented units or groups tend to be integrated into perceptual wholes if they are aligned

with each other. The principle applies in the same way for elements arranged along lines (Figure

4

a) as well as for patterns built from corresponding

lines themselves (Figure

4

b). The balance between continuity and proximity in the formation of salient sub-wholes may be shifted by varying similarity,

which can be accomplished by coloring different branches differently. Thus coloring BX same as AX but different from CX makes AXB a still more

salient unit (Figure

4

c), whereas coloring BX same as CX but different than AX tends to increase the saliency of CXB (Figure

4

d).

Closure principle

Figure

5

a-b is constructed by adding some appropriate elements to Figure

4

a-b. Whereas in Figure

4

a and Figure

4

b the component BX is grouped

with AX, in Figure

5

a and Figure

5

b there is a tendency for this component to rather group with CX, both BX and CX being sides of shape BCX, which

itself constitutes one half of a bow- tie shaped figure. This is an instance of the

closure principle

: elements tend to be grouped together if they are

parts of a closed figure. However, in this particular example, continuity is still relatively effective, and is in strong competition with closure. Using

similarity, the salience of BCX as a visual sub-whole can be increased, as in Figure

5

c, or decreased, as in Figure

5

d.

Figure 5: Closure principle.

Note that the patterns in Figure

4

a and Figure

4

b, although physically contained in Figure

5

a and Figure

5

b, are hard to see there: they can be sought

out with directed attention, but do not appear spontaneously as natural visual wholes. The reason for this is not simply that more elements are added

in the display. This is demonstrated in Figure 7, in which the pattern in

a

is readily discernible in

b

in spite of many added elements, but is practically

invisible in

c

,

d

, and

e

, although geometrically it is just as present there (and in the same place) as in

a

and

b

. The loss of the visual identity of the

pattern is due to the effectiveness of the Gestalt principles, mainly continuity and closure, according to which its elements are perceptually integrated

with other present elements, and assigned to other, new visual wholes. One way in which its visual identity can be recovered is by simply changing its

color to make it dissimilar from the surround. For a demonstration, position the cursor anywhere within the area of Figure 7. Note also that when the

cursor is removed from the figure and the pattern again assumes the same color as the added elements, it quickly (though not necessarily

instantaneously) fades from view, and no effort of attention can restore it to a salient visual whole. For a further demonstration, hold the left mouse

button depressed while positioned within the area of the figure, which will remove the pattern and reveal only the added elements. A classical study of

such 'hidden figure' effects was reported by Gottschaldt (1926).

These examples are instances of

camouflage

, the phenomenon in which objects are hidden from view but not by being occluded: instead, they are

perceptually subdivided (broken up internally) and repartitioned, that is, their parts are grouped with parts of the surrounding environment. As used

by animals in the struggle for survival and by humans in warfare, the power of Gestalt principles thus makes it possible for organisms and things which

are in plain sight to become effectively invisible and therefore undetectable by adversaries. Thus whether a physical object that is optically present

exists or does not exist visually, depends on the interplay of perceptual laws.

Good gestalt principle

The pattern in Figure

6

a is readily partitioned into two components, a straight line and a wavy line that cross each other. This perceptual

decomposition is strengthened by similarity (Figure

6

b). An alternative decomposition of Figure

6

a into two abutting corners, depicted in Figure

6

c,

does not seem to arise spontaneously; this can be explained by noting that it would violate the continuity principle. However, an appeal to continuity

does not explain why the partition in Figure

6

d does not spontaneously arise easily in Figure

6

a either, although both of its components are continuous

lines.

Figure 6: Good Gestalt principle 1.

In another, related example, Figure

7

a spontaneously decomposes into a semi-wheel with curved cogs touching a rectangular 'snake'. However, this

perceptual outcome actually violates the continuity principle, because at the point at which the two components touch, this decomposition involves

angles, instead of following the directions of the crossing continuous lines. An even clearer decomposition is achieved by introducing similarity as well

(Figure

7

b). However, similarity can also be used to enhance a radically different decomposition into two crossing twisted threads, favored by

continuity, as indicated in Figure

7

c.

Figure 7: Good Gestalt principle 2.

According to the Gestalt viewpoint, the dominant percepts in Figure

6

a and Figure

7

a are instances of the

good Gestalt principle

: elements tend to

be grouped together if they are parts of a pattern which is a good Gestalt, meaning as simple, orderly, balanced, unified, coherent, regular, etc as

possible, given the input. In this sense, the straight line and the wavy line perceived in Figure

6

a are better forms than the pairs of lines in Figure

6

c

and Figure

6

d, and in Figure

7

a the cog wheel and the snake are better forms than the hybrid shapes in Figure

7

c, that would be generated in Figure

7

a

by conforming to the continuity principle at the crossing point. In such cases global regularity takes precedence over local relations. This principle is

also called the 'law of good form' or the 'law of Pr?

gnanz', a German word that translates roughly as salience, incisiveness, conciseness, impressiveness,

or orderliness.

Past experience principle

In some cases the visual input is organized according to the

past experience principle

: elements tend to be grouped together if they were together

often in the past experience of the observer. For example, we tend to perceive the pattern in Figure

8

a as a meaningful word, built up from strokes

which are grouped to form particular letters of the Roman alphabet (such as 'm', 'i', 'n', etc). Note that the individual letters are rather clearly and

distinctly perceived as 'natural' parts of the connected figure, and are only slightly easier to discern and discriminate if further individuated through

separation (Figure

8

b) or coloration (Figure

8

c). However, in addition to this standard segmentation into letters, the pattern Figure

8

a has many other

alternate partitions, such as the one demonstrated through separation and coloration in Figure

8

d and Figure

8

e. But, in contrast to the standard

segmentation, discerning and discriminating these alternate components (some of which are 'non-letters') within Figure

8

a is a cumbersome task,

similar to the laborious search for the hidden shape in Figures 6c-e; furthermore, the standard segmentation is to some extent perceivable even in

Figure

8

e, where it competes with the segmentation based on the similarity principle. The spontaneity and ease of the standard, dominantly perceived

organization of the strokes into letters, is plausibly mainly due to past experience, that is, to our familiarity with words as written in the script form of

the Roman alphabet. This particular organization might not occur for observers lacking such familiarity; furthermore, the alternate partition would

presumably be natural for observers used to an alphabet whose letters would correspond to the sub-wholes in Figure

8

d and Figure

8

e. Note also that

in print perhaps the most potent Gestalt principle is proximity: simply inserting larger blank spaces between words than between letters (a device not

used in antiquity) helps group together the letters correctly, and establish

words

as the salient visual units in the text. The importance of blank spaces

is demonstrated by the difficulty wehav ewhenreadingtextnotseparatedbyblanksandevenmorewhe nbl an kspacesap pea rinwrongpl aces.

Figure 8: Past experience principle 1.

Although acknowledged by the gestaltists, the experience-based principle was deemed of secondary importance, compared with the other,

stimulus-based principles, and easily dominated by them. As an example, in the pattern in Figure

8

f, in which a slightly overlapping inverted version is

added, the original stimulus is much harder to see, due to the appearance of numerous new salient sub-patterns, generated by continuity and closure.

Auditory Gestalten

Similar as in vision, issues of organization, grouping, and segmentation arise in the auditory domain as well (Bregman, 1990; Kubovy& van

Valkenburg, 2001). The acoustic input is just a one-dimensional temporally varying air pressure waveform, but based on it we can perceive an auditory

scene involving multiple sources of human speech, vocal and instrumental music, animal sounds and other nature noises, occasionally all occurring at

the same time, each with its own sub-phrasing and structure. Some visual Gestalt principles directly apply in the acoustic domain, but mainly in a

temporal rather than spatial form. For example, silence or background noise, interrupted by a loud sound, followed again by silence or noise, is an

auditory analogue of a figure on a ground. Similarly, a regular series of identical short clicks is an analogue of Figure

2

a, with equal temporal intervals

between sound events playing the role of equal spatial distances. With deliberate attention, one can mentally superimpose a structure on this sequence,

such as hearing consecutive pairs of clicks, as in 12/34/56. However, such a phenomenal segmentation is achieved much more naturally and easily by

simply increasing the intervals between some clicks, analogously to Figure

2

b. This is an instance of an auditory temporal analogue of the visual spatial

proximity principle; there is also a spatial auditory variant, involving pairs of identical sounds separated by equal intervals, but coming from different

directions, such as left, left/in front, in front/right, right. Auditory analogues of instances of the visual similarity principle, as illustrated in Figure

3

,

are also readily established, but with differences and similarities of color, size etc being replaced by differences and similarities of loudness, pitch, and

timbre of sounds. Auditory analogues of some other Gestalt principles may also be constructed.

Contemporary work

Figure 9: Past experience principle 2.

The principles described above, together with others not illustrated here, such as the

symmetry principle

(symmetrical components will tend to

group together), the

convexity principle

(convex rather than concave patterns will tend to be perceived as figures), and others, are part of the

classical heritage of perception studies. In contemporary research, of which only a few examples will be noted below, the seminal insights and issues

raised by the gestaltists are developed and extended in various directions.

For example, contrary to the classical views, more recent research has indicated that even such a basic feature as figure-ground articulation may in

some instances be based on experience (Peterson &Skow- Grant, 2003). For example, although in displays with two homogeneous regions, neither of

which surrounds the other, assignment to figure and ground is often ambiguous, in some cases in which one region resembles an object, such as a tree

in Figure

9

, that region is preferably perceived as figure.

Palmer and colleagues have developed some new principles of visual field organization. For example, Palmer (1992) has proposed the

common

region principle

: elements tend to be grouped together if they are located within the same closed region. An illustration is provided in Figure

10

a. It

depicts the same spatial distribution of elements which, in Figure

2

c, elicited the grouping 1/23/45/6; however, with superimposed closed contours

the preferred grouping becomes 12/34/56.

Palmer & Rock (1994) proposed the

element connectedness principle

: elements tend to be grouped together if they are connected by other

elements. This principle is illustrated in Figure

10

b. Like Figure

10

a, Figure

10

b is also based on Figure

2

c, but, due to some elements being connected,

the preferred perceived grouping is 12/34/56.

Figure 10: Principles of common region and element connectedness.

Researchers have also presented computational models of some Gestalt principles (Kubovy& van der Berg, 2008), studied their possible

neural

bases

(Sasaki, 2007; Han et al., 2005; Qiu& von der Heydt, 2005; Roelfsema, 2006), and attempted to relate them to natural image statistics (Geisler et al.,

2001; Elder & Goldberg, 2002).

Unresolved issues

As formulated by Wertheimer, Gestalt principles involve a 'ceteris paribus' (all other things being equal) clause (Palmer, 1999). That is, each principle

is supposed to apply given that the other principles do not apply or are being held constant. In case two (or more) principles apply for the same input,

and they favor the same grouping, it will tend to become strengthened; however, if they disagree, usually one wins or the organization of the percept is

unclear. Several examples of the domination of one principle over another are presented above. However, although it has been addressed to some