Onset of illusory figures attenuates change blindness.

We examined whether the onset of a new object defined by illusory contours is detected with greater frequency than offset when neither is associated with a unique sensory transient. Observers performed a "one-shot" change detection task in which offsetting or onsetting elements of high luminance contrast circles generated the appearance or disappearance of a Kanizsa figure. Presenting "illusory figures" via this "flicker" method ensures that (1) any unique luminance transients associated with the two types of change are eliminated, and (2) the objects themselves can only be represented at a relatively high level. Results showed that offsets were detected more frequently than onsets only when they generated the onset of a Kanizsa figure. We argue that object appearance dominates object disappearance via mechanisms that operate at the level at which objects are constructed.