JUDGED DISPLACEMENT - A MODULAR PROCESS

Effects of a prior verbal cue on memory for the final location of a mo ving target were examined. Subjects were presented with a cue informin g them which of two types of trial (bounce or crash) would be presente d, and cue validity was varied across subjects. After presentation of the cue, a circular target appeared at one side of the display and mov ed toward a barrier. The target collided with the barrier and either b ounced off the barrier (bounce trials) or crashed through the barrier (crash trials). Shortly after the target either bounced or crashed, th e target and barrier simultaneously vanished. Subjects then indicated the target's vanishing point by positioning a crosshair. For bounce tr ials, judged vanishing point was generally displaced forward in the di rection of motion; for crash trials, judged vanishing point was displa ced either slightly forward or backward. Changing the probability of c ue validity did not change the overall displacement pattern of targets preceded by valid cues. Targets preceded by invalid cues, however, ge nerally showed less forward displacement (or more backward. displaceme nt) than targets preceded by valid cues. Content of the cue thus influ enced the subsequent magnitude of displacement, demonstrating that dis placement was not informationally encapsulated or cognitively impenetr able. Implications of the data for theories of displacement and repres entational momentum are discussed, and suggestions for a neural networ k model of the memory shift phenomenon are advanced.