Shape Recognition and Figure-Ground Organization

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Theoretical attempts to understand visual perception often partition perceptual processes into those processes that can be performed simultaneously and those that must be performed successively. Most theorists have assumed that figure-ground organization and shape recognition are performed successively. Figure-ground organization is the determination of which regions in the visual field represent figures and which constitute the backgrounds against which the figures are viewed. Figure and ground regions are separated by a contour; the region to which the contour is assigned appears to be the recognizable figure, whereas the other region appears to be an undifferentiated ground which simply appears to continue behind the figure. Despite the linkage between shape recognition and figure-ground organization, these theorists have argued that figure-ground organization must precede shape recognition, appealing either explicitly or implicitly to the argument that one cannot recognize a figure until there is a figure to be recognized. Consequently, figure-ground relationships are generally conceived to be determined by stimulus variables only (i.e., variables such as the relative areas, symmetries, convexities, and enclosure of the two regions on either side of a contour). Contrary to this argument, however, previous studies in Peterson's laboratory have shown that certain shape recognition analyses are conducted prior to the determination of figure and ground. These experiments can be readily integrated into current theoretical approaches to shape recognition, thereby rendering this argument obsolete. The planned experiments will examine the conditions under which shape recognition processes can contribute to figure-ground computations. One series of experiments will identify which specific types of contours (e.g., luminance contours, binocular disparity contours, and/or color contours) permit shape recognition computations to be performed simultaneously with the analysis of the stimulus variables relevant to figure-ground organization. Another series of experiments will test whether the shape representations corresponding to both interpretations of a reversible figure-ground stimulus are activated simultaneously prior to the assignment of the figure-ground contour. A third series of experiments will attempt to explicate the rules governing the interactions between shape recognition variables and stimulus variables in figure-ground computations. These experiments will provide information about fundamental aspects of visual processing, including the manner in which analyses of physical variables interact with cognitive variables in perceptual organization. These experiments are certain to be relevant to the design of surrogates for physical scenes.