Abstract
Previous research (Bian, Braunstein, and Andersen, 2005, 2006) has shown that observers organize the 3D layout in scenes based on ground surface information. We also found that changes on a ground surface were faster and easier to detect than changes on a ceiling surface (VSS, 2006). In the current study, we examined whether this ground surface advantage in change detection depends on the existence of a coherent surface or on the layout of objects in the scene. On each trial observers fixated a cross and were presented an original scene and a modified scene for 250ms each in a sequence of A, A, A', A'. The original scene contained a surface, which was either a ground surface, a ceiling surface defined by a randomized black-white checkerboard texture and contained 12 colored objects (6 pyramids and 6 cubes). The variable of interest was the coherent structure of the ground or ceiling surface, which was altered by rearranging regions of the scene in the visual field. When a scrambled surface was presented, the objects either formed a ground-like layout (objects further away from observers were higher in the image) or a ceiling-like layout (objects further away from observers were lower in the image). A change was introduced in the display by changing an objects location in depth. The two scenes were alternated until subjects detected a change. Control trials with no change were also included. The results showed a significant advantage for objects forming a ground-like layout compared to objects forming a ceiling-like layout, suggesting the importance of the layout of objects in a scene. However, a local analysis showed that this ground-like layout advantage was only present when a coherent surface was presented, indicating the importance of a coherent ground surface in organizing 3-D scenes.
Supported by NIH AG13419-06 and EY18334-01.