Universal principles of perceptual organization
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 favored.
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, it has been argued that it is easier to see Rubin's vase when the area it occupies is smaller (Coren et al. 1994, 377). 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.