Abstract
Past research on figure ground assignment to contours has largely considered static contours. Here we report a simple and extremely robust dynamic cue to figural assignment, based on whether the bounding region of a contour is advancing or receding. Subjects saw a straight or jagged contour moving behind a virtual aperture; after a brief time, a probe appeared slightly offset from the contour and the subject had to report whether the probe was ‘on’ or ‘off’ the moving ‘surface’, effectively assigning figure and ground to the two sides of the moving contour. Subjects showed a strong preference (∼95–98%) to assign figure so that the surface that the contour was bounding was growing larger within the aperture (advancing) rather than smaller (receding). This was true regardless of the direction of motion of the contour and regardless of the initial/ending size of the bounded regions (i.e. the motion cue served to override the conventional cue of smaller area). This is a somewhat surprising result in that a moving object produces both receding and advancing motion within different regions of the visual field. This finding highlights the importance of dynamic factors in figure/ground assignment and perceptual organization, as well as suggesting a possible link between figure-ground assignment and motion perception.
JV funded by an NSF Graduate Research Fellowship EB & MT funded by NGA Award #HM1582-04-C-0051