Abstract
The current study was conducted to examine whether the minimal deformation hypothesis can explain a stereokinetic percept. Stereokinetic stimuli are 2D configurations that lead to 3D percepts when rotated in the image plane. A rotating ellipse with an eccentric dot gives rise to the percept of a cone with defined height. The dot is perceived as the apex of the cone, which is constantly deforming except when the dot is on the minor axis of the ellipse. In the current study, the spatial relationship between the ellipse and dot varied across trials in terms of the dot's location (0º [minor axis], 30º, 60º, 90º [major axis]), the aspect ratio of the ellipse (0.6 or 0.8), and rotation speed (60º/sec or 90º/sec). During each trial, participants (n = 8) adjusted the length of a 2D bar to indicate their perceived height of the cone. This 2D bar was oriented along the ellipse's minor axis and was perceived to be perpendicular to the circular base of the cone. Our results were quantitatively consistent with the traditional hypothesis of minimal deformation, which is similar to the maximal rigidity assumption (Ullman, 1979). As the dot shifted position from the minor axis towards the major axis, observers consistently reported an increasingly shorter cone. The results illustrate the tendency of observers to perceive the apex of the cone at a height that minimized its distance to the axis of rotation in order to reduce the relative motion between the dot and circular base of the cone. Therefore, the hypothesis can also be considered as a 3D extension of the more recent "slow and smooth" hypothesis (Yuille & Grzywacz, 1988; Weiss, Simoncelli, & Adelson, 2002).
Meeting abstract presented at VSS 2017