Figure-ground contrast, in the context of map design, is a property of a map in which the map image can be partitioned into a single feature or type of feature that is considered as an object of attention (the figure), with the remainder of the map being relegated to the background, outside the current focus of attention. It is thus based on the concept of figure–ground from Gestalt psychology. For example, in a street map with strong figure-ground contrast, the reader would be able to isolate and focus attention on individual features, like a given street, park, or lake, as well as layers of related features, like the street network. Strong figure-ground contrast has been seen as a desirable goal of map design, because it helps the map reader to perceive distinct geographic phenomena in the map. This allows more complex composition techniques such as visual hierarchy to organize these phenomena into clear structures that help readers use the map for its intended purposes. Related disciplines and history Fields other than cartography, such as psychology, neurology, and computer science, have studied differentiation of figure from ground. Many studies have employed different experiments, varying the shades, textures, and orientations of test pictures to determine the best method for figure–ground design with mixed results. A current application of figure–ground research is the development of computer vision for robots. By studying the way humans perceive figure and ground, methods can be developed to improve computer vision algorithms. Unlike some of these other applications, in which figures and grounds are discovered in a natural visual field that may or may not have this contrast, in cartography they are intentionally created by design, based on knowledge of the visual perception tendencies of map readers. Since the early days of academic cartography, there has been a recognition of the need for maps to have a conceptual structure. In The Look of Maps (1952), Arthur Robinson emphasized the need for visual contrast in making maps that are clearly organized, including the figure-ground relationship, "the visual relation of one or more components to the background on which they are seen." In 1972, Borden Dent appears to have been the first to use the principles of perceptual psychology to develop a theory of how the figure-ground relationship emerges on maps (as well as Visual hierarchy), and a set of guidelines for design to strengthen it. He identified heterogeneity (contrast),