VISUAL-PERCEPTION OF EGOCENTRIC DISTANCE AS ASSESSED BY TRIANGULATION

Two triangulation methods for measuring perceived egocentric distance were examined. In the triangulation-by-pointing procedure, the observe r views a target at some distance and, with eyes closed, attempts to p oint continuously at the target while traversing a path that passes by it. In the triangulation-by-walking procedure, the observer views a t arget and, with eyes closed, traverses a path that is oblique to the t arget; on command from the experimenter, the observer turns and walks toward the target. Two experiments using pointing and 3 using walking showed that perceived distance, averaged over observers, was accurate out to 15 m under full-cue conditions. For target distances between 15 and 25 m, the evidence indicates slight perceptual underestimation. R esults also show that observers, an average, were accurate in imaginal ly updating the locations of previously viewed targets.