Problems in depth perception : equidistance judgments in the vicinity of a binocular illusion.

PDFTech ReportAM 66-24DOT/FAA/AM-66/24Visual perceptionDepth perceptionDistance perceptionDepthSizeDistanceJudgment (Human characteristics)VisionVision testsHuman subject testingExperimentsUnited StatesCivil Aerospace Medical InstituteAgee, Frank L.Gogel, Walter C.United States. Office of Aviation MedicineNTL-AVIATION-AVIATIONUS Transportation CollectionJudgments of the size and distance of objects are sometimes made in aircraft under background-viewing conditions that may themselves create false sensory impressions (illusions). In this study, the effects of a background illusion on judgments of the size and distance of objects that were independent of that background were examined. Misleading size cues associated with a binocularly observed trapezoidal window produced an apparent depth orientation of the window that was different from its physical orientation.As expected, it was found that errors occurred in adjusting two other objects (disks) to apparent equidistance with each other in the presence of the window and that the direction of the errors in apparent equidistance was related to the direction of the errors in the perceived slant of the trapezoidal window. It was less clear that errors in the judgment of apparent equidistance occurred when the orientation of the window and the separation of the disks were vertical rather than horizontal. Possible explanations for discrepancies between the magnitude of the perceptual errors associated with the trapezoidal window and those associated with the equidistance judgments are discussed