2. Introduction to Perception:
Perceptual Organization

Gestalt Laws of Grouping | Figure and Background

Organizing raw sensory stimuli into meaningful experiences involves cognition, a set of mental activities that includes thinking, knowing, and remembering. Knowledge and experience are extremely important to perception, because they help us make sense of the input to our sensory systems.


Gestalt Laws of Grouping

How people perceive a well-organized pattern or whole, instead of many separate parts, is a topic of interest in Gestalt psychology. According to Gestalt psychologists, the whole is different than the sum of its parts. Gestalt is a German word meaning configuration or pattern.

A major goal of Gestalt theory in the 20th century was to specify the brain processes that might account for the organization of perception. Gestalt theorists, chief among them the German-U.S. psychologist and philosopher, the founder of Gestalt theory, Max Wertheimer and the German-U.S. psychologists Kurt Koffka and Wolfgang Köhler, rejected the earlier assumption that perceptual organization was the product of learned relationships (associations), the constituent elements of which were called simple sensations. Although Gestaltists agreed that simple sensations logically could be understood to comprise organized percepts, they argued that percepts themselves were basic to experience. One does not perceive so many discrete dots (as simple sensations), for example; the percept is that of a dotted line.

Without denying that learning can play some role in perception, many theorists took the position that perceptual organization reflects innate properties of the brain itself. Indeed, perception and brain functions were held by Gestaltists to be formally identical (or isomorphic), so much so that to study perception is to study the brain. Much contemporary research in perception is directed toward inferring specific features of brain function from such behaviour as the reports (introspections) people give of their sensory experiences. More and more such inferences are gratifyingly being matched with physiological observations of the brain itself.

Many investigators relied heavily on introspective reports, treating them as though they were objective descriptions of public events. Serious doubts were raised in the 1920s about this use of introspection by the U.S. psychologist John B. Watson and others, who argued that it yielded only subjective accounts and that percepts are inevitably private experiences and lack the objectivity commonly required of scientific disciplines. In response to objections about subjectivism, there arose an approach known as behaviourism that restricts its data to objective descriptions or measurements of the overt behaviour of organisms other than the experimenter himself.


Figure and Background

Not only does perception involve organization and grouping, it also involves distinguishing an object from its surroundings. Notice that once you perceive an object, the area around that object becomes the background. Gestalt psychologists have devised ambiguous figure-ground relationsips - that is, drawings in which the figure and ground can be reversed - to illustrate their point that the whole is different from the sum of its parts.

illustration of a black vaseThe "figure and ground" illusion is commonly experienced when one gazes at the illustration of a black vase the outline of which is created by two white profiles. At any moment one will be able to see either the black vase (in the centre area) as "figure" or the white profiles on each side (in which case the black is seen as "ground"). The fluctuations of figure and ground may occur even when one fails deliberately to shift attention, appearing without conscious effort. Seeing one aspect apparently excludes seeing the other.

Although such illustrations may fool our visual systems, people are rarely confused about what they see. In real world, vases do not change into faces as we look at them. Instead, our perceptions are remarkably stable.

Note: The Gestaltist's concept is "figure-ground segregation" is not only referring to foreground-background, but also covers situations, e.g., in which you look through a window outside at a tree. The frame of the window is then the ground the tree the "figure", although it is behind the "ground."

See: Ehrenstein, W. (1930). Untersuchungen über Figur-Grund-Fragen. Zeitschrift für Psychologie, 117, 339-412.


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Source:  Optical Illusions