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Zheng Bian, Myron L. Braunstein, George J. Andersen; The ground dominance effect depends both on the surface and its location in the visual field. Journal of Vision 2005;5(8):64. doi: 10.1167/5.8.64.
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© ARVO (1962-2015); The Authors (2016-present)
We reported (2004, in press) that when objects were in optical contact with both a ground and ceiling surface, layout was determined by ground contact (a ground dominance effect). Here we report two experiments that examined whether this effect is due to the difference in layout of ground and ceiling surfaces (whether the surface recedes in depth from bottom to top or from top to bottom in the image) or to the location of the surface in the visual field. In the first experiment the observer fixated on a central cross, with fixation controlled using a go-no-go digit identification task. A scene containing a ground surface, a ceiling surface and two vertical posts was then presented for 250 ms. Optical contact with the ground indicated that one post was closer, whereas optical contact with the ceiling indicated that the other post was closer. Either the ground surface was below fixation and the ceiling surface was above fixation, both surfaces were below fixation, or both surfaces were above fixation. Control conditions were included to examine effects of distance from fixation. The proportion of judgments consistent with optical contact with the ground surface was highest in the ground-below-ceiling-above condition (0.80), followed by both surfaces above fixation (0.70) and both surfaces below fixation (0.63). In the second experiment only one surface was presented on each trial. The proportion of judgments consistent with optical contact with the surface that was presented was generally higher for the ground surface than for the ceiling. The proportion consistent with the ground surface dropped as the ground surface was moved away from fixation in either direction, but the proportion consistent with the ceiling surface increased when the ceiling surface was moved below fixation. Overall, the results suggest that the ground dominance effect is a result of an interaction between the type of surface and its location in the visual field.
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