Perturbation of Induced Rotation as an Index of Pattern Structure

Abstract

Most previous attempts to quantify the organizational complexity of visual stimuli have focussed upon stimulus attributes rather than on the perceptual consequences of stimulus processing. We believe that it is more profitable to emphasize perceptual effects and have developed a methodology whereby the smoothness of induced rotation is used to quantify the organizational structure of geometric figures. Our subjects were presented with two-dimensional perspective views of figures in which the azimuth was successively changed. When the tachistoscopic presentation times ranged from 60 to 100 msec, smooth rotation was always perceived for azimuth orders of 0°, 15°, 30°, 30°, 15°, 0°. When a 15° azimuth view was interposed between the two 30° views, an irregularity in rotation was apparent if the presentation duration exceeded a critical value. We used this value as an index of structural detail. Our figures were computer-generated plots of stacked cubes that were produced in either shaded or outline patterns. Subjects viewed two cycles of rotation of either shaded (textured) or outline figures then judged whether the induced rotation was smooth or interrupted. We found that outline figures generally required longer interposition durations than the more solid patterns for rotation to appear interrupted. It seemed as though structural detail, such as texture, provided more information for induced rotation thereby accentuating any flaws in the smoothness of movement.