Perceptual Grouping

A. How are sensations organized into meaningful perceptions? Figure-ground organization. The simplest organization involves grouping some sensations into an object, or figure, that stands out on a plainer background. It is probably inborn, since it is the first perceptual ability to appear after cataract patients regain sight. In normal figure-ground perception, only one figure is seen. Reversible figures: Figure and ground can be switched. As you shift from one pattern to the other, you should get a clear sense of what figure-ground organization means. Gestalt psychologists conclude a number of factors would bring some order to your perceptions causing the formation of a figure:

l. Nearness. Stimuli that are near each other tend to be grouped together. If three people stand near one another and a fourth person stands 10 feet away, the adjacent three will be seen as a group and the distant person an outsider--and how differently a group of a certain number can be perceptually organized depending upon their spacing.

2. Similarity. Stimuli that are similar in size, shape, color, or form tend to be grouped together. For instance, picture two bands marching side by side. If their uniforms differ, the bands will be seen as two separate groups, not as a single large group--and can be combined to produce new organization.

3. Continuation, or continuity. Perceptions tend toward simplicity and continuity. It is easier to visualize a wavy line on a squared-off line than it is to see a complex row of shapes.

4. Closure. Closure refers to the tendency to complete a figure, so that it has a consistent overall form. Our tendency to form shapes--even with minimal cues--is powerful.

5. Contiguity. Nearness in time and space. Contiguity is often responsible for the perception that one thing has caused another. Knocking on wood (out of sight) while knocking on ones head (simultaneously!) leads to the irresistible perception that the head is made of wood.

Perceptual Organization/Meaningful Pattern, Perceptual Hypothersis. In addition to these principles, Learning and past experience greatly affect perceptual organization. One can have an immediate recognition of letters and not be able to read handwriting. Camouflage patterns break up figure-ground organization. If you had not seen a similar camouflaged animal in a scene, for example, would you recognize it? In a way we are all detectives, seeking patterns in what we see. In this sense a meaningful pattern represents a perceptual hypothesis, or quess held until the evidence contradicts it. The active nature of organizing perceptions is perhaps most aparent for ambiguous stimuli (patterns allowing more than one interpretation). If you look at a cloud, you may discover dozens of ways to organize its contours into fanciful shapes and scenes. Even clearly defined stimuli may permit more than one interpretation. In some instances, a stimulus may offer such conflicting information that perceptual organization becomes impossible. A tendency to make a three-dimensional object out of a drawing is frustrated by the "three-pronged widget", an impossible figure. [NOTE: Visuals not included here.]

B. Is the ability to understand drawings learned? Humans almost always appear to understand lines that represent the edges of surfaces. We also have no problem with a single line used to depict the parallel edges of a narrow object, such as a rope. One thing that we do not easily recognize is lines showing color boundaries on the surface of an object.

To illustrate the last point, let's pay a brief visit to the Songe, a small tribe in Papua New Guinea. Before they were tested, the Songe had never made or seen line drawings--not even doodles scratched on the ground. As a test, the Songe were shown drawings of a hand and a parrot. They easily recognized the hand and the parrot from simple outlines, but lines showing color bondaries confused them. The half-moons on the fingernails, for example, made them think that the nails had been damaged and new ones were growing in. Similarly they thought that the parrot must have been cut repeatedly. They thought this even though the lines in the drawing match color markings of parrots found in Songe territory (Kennedy, 1983).