Recognition of random shapes followed at varying delays by attended or unattended shapes, digits, and line grids.

Three experiments evaluated the effect of poststimulus distractor characteristics in altering recognition of random shapes. Experiment 1 demonstrated that when 150 msec or 300 msec were allowed for processing the initial shape stimulus, recognition was lowered only when it was followed by an attended shape or digit distractor. Unattended shapes, digits, and line grids and attended line grids left recognition essentially perfect. Attended shapes lowered recognition more than attended digits. Experiment 2 found that attended shapes, digits, and line grids all masked random shapes when presented immediately upon offset of a random shape displayed for 50 msec. As processing time increased, digit distractors became less effective than shape distractors, while line grids lost all effect. The shape distractors lowered recognition up to 1,200 msec. Experiment 3 showed that the larger recognition loss produced by the shape distractor than by the digit distractor could not be attributed to differences in response procedure. It was suggested that memory for random shapes moves from brief visual storage to a limited capacity visual short-term memory. Attended shape distractors may eliminate the stimulus shape from visual short-term memory thus preventing long-term storage.