refers to a cognitive ability to separate elements based upon contrast, that is, dark and light, black and white. Many times this definition is expanded from a simple perception based on contrast to include abstract (i.e. non-visual) concepts such as melody/harmony, subject/background and positive/negative space. The famous optical illusion image depicting both a vase and two profiles of a human face (the Rubin vase) is often used to illustrate the concept of figure ground: Depending on whether the white or black color is seen as the figure (forefront) or the ground (background) the brain will interpret the picture as two different images, and it may be difficult (or even, according to gestalt psychological theory, impossible) to perceive both meaningful images simultaneously.
Classified under Perception Definition contributed by NPicchetti about eleven months ago.