Selection and Boundary
Selection is a key aspect of figure-ground. One shape or the another is selected by the brain according to the task. If you are looking at a series of letters on a page looking for a Z, most of what you see is ground and the Z becomes figure when your eyes pass over one, but only because the task is to find the Z. During the search your eyes may focus for a split second on other letters that are similar to the shape of a Z, but once the search is done it is usually only the Z that can be recalled. The same happens when we are driving; we ignore the multitude of buildings, people and signs yet easily isolate the traffic signals and signs.
A number of diagnostic tests used in human sciences test the selection abilities of the subject. A number of them serve to illustrate the strength of figure-ground in perception. The most common example is the slat fence drawings below.
In the instance above, the lines are of equal spacing from one another. Depending on which space (slat) you are looking at, every other slat from that one will seem to be figure, in a space closer to the viewer. The other spaces will be perceived as ground, in a space farther from the viewer. It is possible to see the focused slat as ground but it requires time or effort to see the effect. The brain wants to see the object focused on as field.
In the second drawing, the lines are no longer evenly spaced. Do you see the wide slats as field or ground, how about the narrow slats? Most people will see the narrow groupings as figure and the wider groupings as ground. This makes it easier for the brain to hold the initial grouping it perceives, but the field and ground still reverse with a little effort. What you see as figure at any moment is the result of selection.
If we added an additional line to the right or left we would introduce more ambiguity because all of the elements would no longer be paired and “grouping” would influence perception. The closer elements are together the more likely they will be seen as figure and related. This is a result of “proximity grouping”, discussed later.
Boundary is an component of Gestalt showing how common edges can affect the perception of an object. A single expressive line can create multiple shapes that the brain associates with known objects creating a “contour rivalry”. Contour rivalry creates a tension within the frame as the figure and ground flip flop. Closure of one shape or another can help resolve the conflict. Closure is discussed later.
Above we see the classic example of boundary effect on figure and ground in the “Rubin Vase”. What do you see? Is it the shape of a goblet or a profile of two faces or what? Which did you see first and how long did it take to see the other? The second example is the same but with added information. So you still see the same forms that you did in the first example?
Boundary is a common element found in graphic symbols and logo design. Corporations and graphic designers often use a boundary element when creating logos as shown below. Here the brain perceives a sphere where none actually exists, only a series of horizontal lines.
Next Time: Artifice