Gestalt Principles of Visual Organization
In discussing the 'selectivity' of perception I have alluded to
foregrounding and backgrounding. We owe the concept of 'figure' and
'ground' in perception to the Gestalt psychologists: notably
Max Wertheimer (1880-1943), Wolfgang Köhler (1887-1967) and Kurt Koffka
(1886-1941). Confronted by a visual image, we seem to need to separate a
dominant shape (a 'figure' with a definite contour) from what our current
concerns relegate to 'background' (or 'ground'). An illustration of
this is the famous ambiguous figure devised by the Danish psychologist
Edgar Rubin.
Images such as this are ambiguous concerning figure and ground. Is the
figure a white vase (or goblet, or bird-bath) on a black background or
silhouetted profiles on a white background? Perceptual set operates in
such cases and we tend to favour one interpretation over the other (though
altering the amount of black or white which is visible can create a bias
towards one or the other). When we have identified a figure, the contours
seem to belong to it, and it appears to be in front of the ground.
In addition to introducing the terms 'figure' and 'ground', the
Gestalt psychologists outlined what seemed to be several
fundamental and universal principles (sometimes even called 'laws')
of perceptual organization. The main ones are as follows (some of the
terms vary a little): proximity, similarity, good continuation,
closure, smallness, surroundedness, symmetry and prägnanz.
The principle of proximity can be demonstrated thus:
What you are likely to notice fairly quickly is that this is not just
a square pattern of dots but rather is a series of columns of dots.
The principle of proximity is that features which are close together
are associated. Below is another example. Here we are likely to
group the dots together in rows.
The principle also applies in the illustration below. We are more likely
to associate the lines which are close together than those which are
further apart. In this example we tend to see three pairs of lines which
are fairly close together (and a lonely line on the far right) rather than
three pairs of lines which are further apart (and a lonely line on the far
left).
The significance of this principle on its own is likely to seem unclear
initially; it is in their interaction that the principles
become more apparent. So we will turn to a second major principle of
perceptual organization - that of similarity. Look at the
example below.
Here the little circles and squares are evenly spaced both horizontally
and vertically so proximity does not come into play. However, we do
tend to see alternating columns of circles and squares. This, the
Gestalt psychologists would argue, is because of the principle of
similarity - features which look similar are associated. Without
the two different recurrent features we would see either rows or columns
or both...
A third principle of perceptual organization is that of good
continuity. This principle is that contours based on smooth
continuity are preferred to abrupt changes of direction. Here, for
instance, we are more likely to identify lines a-b and c-d crossing than
to identify a-d and c-b or a-c and d-b as lines.
Closure is a fourth principle of perceptual organization:
interpretations which produce 'closed' rather than 'open' figures are
favoured.
Here we tend to see three broken rectangles (and a lonely shape on
the far left) rather than three 'girder' profiles (and a lonely shape
on the right). In this case the principle of closure cuts across the
principle of proximity, since if we remove the bracket shapes, we return
to an image used earlier to illustrate proximity...
A fifth principle of perceptual organization is that of smallness.
Smaller areas tend to be seen as figures against a larger background.
In the figure below we are more likely to see a black cross rather than
a white cross within the circle because of this principle.
As an illustration of this Gestalt principle, Coren, Ward and Enns
(1994, 377) argue that it is easier to see Rubin's vase when the area it
occupies is smaller. The lower portion of the illustration below offers
negative image versions in case this may play a part. To avoid
implicating the surroundedness principle I have removed the
conventional broad borders from the four versions. The Gestalt principle
of smallness would suggest that it should be easier to see the vase rather
than the faces in the two versions on the left below.
The principle of symmetry is that symmetrical areas tend to be
seen as figures against asymmetrical backgrounds.
Then there is the principle of surroundedness, according to which
areas which can be seen as surrounded by others tend to be perceived
as figures.
Now we're in this frame of mind, interpreting the image shown above
should not be too difficult. What tends to confuse observers initially is
that they assume that the white area is the ground rather than the figure.
If you couldn't before, you should now be able to discern the word 'TIE'.
All of these principles of perceptual organization serve the overarching
principle of pragnänz, which is that the simplest and most
stable interpretations are favoured.
What the Gestalt principles of perceptual organization suggest is that
we may be predisposed towards interpreting ambiguous images in one
way rather than another by universal principles. We may accept such a
proposition at the same time as accepting that such predispositions may also
be generated by other factors. Similarly, we may accept the Gestalt
principles whilst at the same time regarding other aspects of perception as
being learned and culturally variable rather than innate. The
Gestalt principles can be seen as reinforcing the notion that the world is
not simply and objectively 'out there' but is constructed in the process of
perception.
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