Abstract
Previous studies have shown a ground surface advantage in the organization of 3-D scenes (Bian, et. al., 2005, 2006). In the current study, we examined whether there was a ground surface advantage in exocentric distance judgments. Observers were presented with displays simulating either a ground plane or a ceiling surface with random black and white checkerboard texture. In Experiment 1, there were three vertical red poles standing on the ground plane or attached to the ceiling surface. The three poles formed an inverted L-shape so that poles 1 and 2 were separated in depth and poles 2 and 3 were separated horizontally. The observers' task was to use a joystick to adjust the distance between the two poles that were separated horizontally to match the perceived distance between the two poles separated in depth. In addition to the surface presented, we also manipulated motion parallax, the distance of the L-shape, and the size of the L-shape. In Experiment 2, there were 3 horizontal red poles lying on the ground plane or attached to the ceiling surface. The three poles were parallel to each other and separated in depth. The task of the observer was to bisect the distance between the front pole and the back pole, that is, to adjust the distance between the front pole and the middle pole so that it matched the distance between the middle pole and the back pole. In both experiments we found that judged depth on the ground plane was larger than that on the ceiling surface, suggesting less compression of space on a ground surface as compared to on a ceiling surface.
NIH AG031941 and EY18334-01.