Academic journal article Perception and Psychophysics

The Ground Dominance Effect in the Perception of 3-D Layout

Academic journal article Perception and Psychophysics

The Ground Dominance Effect in the Perception of 3-D Layout

Article excerpt

The relative effectiveness of the ground surface and other environmental surfaces (the ceiling and sidewalls) in determining perceived layout was investigated in five experiments and a real-world demonstration. In the first three experiments, two vertical or horizontal posts were positioned between two surfaces (ground and ceiling in all three experiments, left wall and right wall in Experiment 1), and optical contact was manipulated so that the two surfaces provided contradictory information about the relative distances of the posts. Observers judged which of the two posts appeared to be closer. In Experiment 4, to control the height on the posts at which the distance judgments were made, a blue dot was attached to both vertical posts at varying heights and observers judged which dot appeared closer. In Experiment 5, the posts were replaced by two gray ellipses to eliminate the effects of the regular shape and texture. Our findings were that (1) among all four surfaces tested, observers showed a preference to respond according to the optical contact information provided by the ground surface-a ground dominance effect, (2) this effect did not depend on the height of the posts in the image, (3) as the scene was tilted away from a ground/ceiling orientation, the ground dominance effect decreased, and (4) this effect was not due to the location of the judgment.

The perception of 3-D scenes usually involves an integration of information about overall scene depth, the layout or relative position of objects in the scene, and the properties of the objects within the scene (Andersen, Braunstein, & Saidpour, 1998). The information may be either viewer centered, providing absolute or relative distances from the observer to the locations in the scene, or object centered, providing distances among locations in the scene. There is a considerable body of research focusing on the effectiveness of different sources of information used in the perception of individual objects and surfaces in 3-D scenes, such as texture (e.g., Andersen et al., 1998; Stevens, 1981; Todd & Akerstrom, 1987), motion parallax (e.g., Braunstein & Andersen, 1981; Rogers & Graham, 1979), and binocular disparity (e.g., Gillam, Flagg, & Finlay, 1984; Norman & Todd, 1998). Another stream of research has studied the integration of different cues in indicating depth, such as motion and disparity (e.g., Turner, Braunstein, & Andersen, 1997), motion and texture (e.g., Braunstein, 1968), and disparity and shading (Tittle, Norman, Perotti, & Phillips, 1998). These studies have contributed to an understanding of different sources of information for the perception of objects and surfaces and how these sources of information interact, but relatively little is known about how information about scene depth, layout, and object properties from viewer-centered and object-centered sources is integrated to provide a perception of a 3-D scene. In this article, we will consider the role of the ground surface in providing the layout of objects in a 3-D scene.

Alhazen (1989) proposed that the continuous ground surface between objects is important in judging their relative distances. Gibson (1946, 1950; see also Sedgwick, 1983) emphasized the central role of a continuous surface in 3-D perception: "The problem of three-dimensional vision, or distance perception, is basically a problem of the perception of a continuous surface which is seen to extend away from the observer . . . . An array of objects by themselves does not make up visual space. . . . The visual world consists of object-surfaces on a background of an extended ground surface" (Gibson, 1946, p. 420). Gibson developed his ideas into a ground theory, which he defined as "the possibility that there is literally no such thing as a perception of space without the perception of a continuous background surface" (Gibson, 1950, p. 6).

If a continuous background surface underlies the perception of the layout of a 3-D scene, objects must be associated with positions along this surface. …

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