figure–ground the discrimination of an object or figure from the context or background against which it is set. Even when a connected region is grouped together properly, as in the famous figure that can be seen either as a pair of faces or as a vase, it is possible to interpret the region alternately as figure and as ground. This fact was originally elaborated in 1921 by Edgar Rubin (1886– 1951). Figure–ground effects and the existence of other ambiguous figures such as the Necker cube and the duck–rabbit challenged the prevailing assumption in classical theories of perception – maintained, e.g., by J. S. Mill and H. von Helmholtz – that complex perceptions could be understood in terms of primitive sensations constituting them. The underdetermination of perception by the visual stimulus, noted by Berkeley in his Essay of 1709, takes account of the fact that the retinal image is impoverished with respect to threedimensional information. Identical stimulation at the retina can result from radically different distal sources. Within Gestalt psychology, the Gestalt, or pattern, was recognized to be underdetermined by constituent parts available in proximal stimuli. M. Wertheimer (1880–1943) observed in 1912 that apparent motion could be induced by viewing a series of still pictures in rapid succession. He concluded that perception of the whole, as involving movement, was fundamentally different from the perception of the static images of which it is composed. W. Köhler An example of visual reversal from Edgar Rubin: the object depicted can be seen alternately as a vase or as a pair of faces. The reversal occurs whether there is a black ground and white figure or white figure and black ground. (1887–1967) observed that there was no figure– ground articulation in the retinal image, and concluded that inherently ambiguous stimuli required some autonomous selective principles of perceptual organization. As subsequently developed by Gestalt psychologists, form is taken as the primitive unit of perception. In philosophical treatments, figure–ground effects are used to enforce the conclusion that interpretation is central to perception, and that perceptions are no more than hypotheses based on sensory data.
See also KÖHLER, PERCEPTIO. R.C.R.