JUDGED DISPLACEMENT - A MODULAR PROCESS

Effects of a prior verbal cue on memory for the final location of a moving target were examined. Subjects were presented with a cue informing them which of two types of trial (bounce or crash) would be presented, and cue validity was varied across subjects. After presentation of the cue, a circular target appeared at one side of the display and moved toward a barrier. The target collided with the barrier and either bounced off the barrier (bounce trials) or crashed through the barrier (crash trials). Shortly after the target either bounced or crashed, the target and barrier simultaneously vanished. Subjects then indicated the target's vanishing point by positioning a crosshair. For bounce trials, judged vanishing point was generally displaced forward in the direction of motion; for crash trials, judged vanishing point was displaced either slightly forward or backward. Changing the probability of cue validity did not change the overall displacement pattern of targets preceded by valid cues. Targets preceded by invalid cues, however, generally showed less forward displacement (or more backward. displacement) than targets preceded by valid cues. Content of the cue thus influenced the subsequent magnitude of displacement, demonstrating that displacement was not informationally encapsulated or cognitively impenetrable. Implications of the data for theories of displacement and representational momentum are discussed, and suggestions for a neural network model of the memory shift phenomenon are advanced.