Compression of space in visual memory

Human observers had to point to the location of a briefly presented target by means of a mouse after a brief delay following target offset. It was fou nd that observers systematically mislocalized the target closer to the cent er of gaze, and to visually salient markers in the visual display. A percep tual judgment task revealed that these errors in localization were independ ent of whether or not rye movements were made. and even of planning for the m, thereby demonstrating that the effect was a perceptual phenomenon, not a sensorimotor one. Further experiments demonstrated clearly that the magnit ude of the time interval between target presentation and judgment regarding its spatial location was the critical parameter. A longer time interval be tween the event and its report enhanced significantly the amplitude of comp ression, thus establishing this phenomenon as a visual memory effect. We co nclude that visual memory of spatial location is distorted over time in a s ystematic, monotonic fashion as a result of the sustained fixation of the o bserver on a fixed location during and shortly after target presentation, o r by the continual presence of stable. salient landmarks in the environment . (C) 2001 Elsevier Science Ltd. All rights reserved.