Purchase this article with an account.
Huiying Zhong, Myron L Braunstein; Effect of background motion on perceived object shape. Journal of Vision 2003;3(9):858. doi: 10.1167/3.9.858.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
A three-dimensional scene often contains several moving objects and perceived shape may depend on interactions between the motions of these objects. In the present study we address the question of how the speed of a background surface influences shape judgments for a moving object. The stimulus displays were perspective projections of a horizontally-oriented concave dihedral angle (20 or 40 ) shown against a frontal-parallel plane. The dihedral angles translated horizontally. The projected speed of the dihedral edge was 2 /sec and the projected speeds of the front edges were either 2.25 /sec or 2.5 /sec. The background plane was either stationary or translated horizontally at 1, 2, 2.25, 2.5, 4, 6, or 8 /sec. The subject's task was to judge the magnitude of the dihedral angle by adjusting a cross-section of the angle on a separate monitor. We found a significant effect of background speed on dihedral angle magnitude judgments. For each simulated angle magnitude, judged angle magnitude first decreased as the background speed approached the speed of the angle's front edge and then began to increase rapidly after the two speeds were equal. Judged angle magnitude continued to increase with background speed and then leveled off. Similar results, but with greater individual variability, were obtained with vertical dihedral angles and vertical translation of both the angles and background plane. A possible explanation of the results is that the motion of the angles is perceived as having both a translation and a rotation component, with the relative effects of the two components on judged angle magnitude determined by both the angle speed and background speed. A mathematical model of the interaction of background speed and object speed in determining perceived object shape was formulated based on this account of the results.
This PDF is available to Subscribers Only