What Influences the Relative Proportion of ‘Rigid Rotation’ Versus ‘Non-Rigid Deformation’ in a Bistable Stroboscopic Motion Display

Abstract

When observers are presented with a bistable stroboscopic display of an object that appears to transform over time in three-dimensional (3D) space, the dominance of one percept over another is influenced both by stimulus parameters and by cognitive factors. Two experiments were designed to reveal which of several manipulated variables influence most strongly which of two responses is more often observed, one being termed ‘Rigid Rotation’ and the other termed ‘Non-rigid Deformation.’ These two responses were clearly distinguished when drawings of a 3D rectangular box were presented stroboscopically in a two-frame animation with precise control over the Interstimulus Interval (ISI). In the first experiment, the relative dominance of the ‘Rigid Rotation’ response was reduced by changing the colour of one surface of the rectangular box in a manner that was inconsistent with the rotation of the box. Similarly, the relative dominance of the ‘Non-rigid Deformation’ response was reduced by changing the colour of one surface of the rectangular box in a manner that was inconsistent with deformation of the box. In the second experiment, the changes in the relative dominance of the competing motion percepts were observed after prolonged viewing of four different adapting stimuli. The adaptation aftereffects were shown to depend more upon the Interstimulus Interval (ISI) of the stroboscopic display of the adapting stimulus than upon what motion was reportedly ‘seen’ during the viewing of the adapting stimulus. Ultimately, the adaption aftereffect revealed that the relative dominance of the two movement percepts was affected most strongly by the manipulation of a single temporal variable – the ISI. Nonetheless, the results of the first experiment confirmed the influence of surface colour variations on ‘Rigid Rotation’ versus ‘Non-rigid Deformation’ responses