Effect of background motion on the perceived shape of a 3-D object

The effect of the speed of a background surface on the judged shape of a moving object was investigated in four experiments. observers judged the magnitude of a concave dihedral angle translating or rotating against a planar background. Judged angle magnitude decreased (indicating an increase in perceived depth) with increasing background speed until the background speed reached the speed of the front edge of the angle. Judged angle magnitude then increased with background speed until the difference between the background and front edge speed was large. A model that was previously proposed to account for angle magnitude judgments from translations and rotations is extended to displays with a moving background. (C) 2004 Elsevier Ltd. All rights reserved.