The ability to differentiate visually between an object and its background.
A person's ability to separate an object from its surrounding visual field is referred to as figure-ground perception. The object that a person focuses on is called the figure; everything else is referred to as background, or simply ground.
Psychologists have created different kinds of stimuli in order to study how people separate figure from ground. In some cases, these stimuli involve simple ambiguous figures like the famous face-vase figure that can be interpreted as two faces looking at one another or a goblet, depending on what aspect a person focuses on. In other situations, complex stimuli can be used to demonstrate figure-ground relationships. For example, the 3-D Magic Eye pictures involve relaxing the muscles of the eyes to see a three-dimensional figure-ground picture. Until a viewer positions the eyes appropriately, the stimulus is invisible; when the eye muscles are appropriately relaxed, the three-dimensional figure emerges. Easily distracted children are often unable to focus on one object as they ignore or block out the background.
The interpretations that people derive from these stimuli are real, even though the objects are ambiguous or are nonexistent. A good example of this involves illusory or subjective contours. In the illustration, people will see an entire square, complete with borders (contours), even though the borders do not really exist.
Psychologists have also demonstrated figure-ground principles with auditory stimuli. For example, some people have claimed that there are satanic or otherwise harmful lyrics embedded backwards in some rock music. In most cases, when people first listen to the music backwards, they hear absolutely nothing that resembles speech. When somebody tells them to listen for particular words or phrases, however, people report hearing satanic words. As with illusory contours, the words are not really there until someone's attention is focused appropriately on a particular set of sounds.
Dance, Sandy. Picture Interpretation: A Symbolic Approach. River Edge, NJ: World Scientific, 1995.
Pavel, Monique. Fundamentals of Pattern Recognition 2nd ed. New York: M. Dekker, 1993.