Perceived distance, shape and size

• Published in: Vision research (Oxford) Vol. 39; no. 5; pp. 975 - 986
• Main Authors: Brenner, Eli, van Damme, Wim J.M
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.03.1999; Elsevier Science
• Subjects: Biological and medical sciences; Cue interaction; Cues; Depth; Distance Perception - physiology; Form Perception - physiology; Fundamental and applied biological sciences. Psychology; Humans; Judgment; Motion parallax; Perception; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Size Perception - physiology; Spatial vision; Stereopsis; Vision; Vision Disparity - physiology; Stereopsis; Motion parallax; Spatial vision; Depth; Cue interaction; Human; Stimulus shape; Visual stimulus; Stimulus distance; Stimulus size; Perception; Space perception; Binocular vision; Experimental study
• ISSN: 0042-6989; 1878-5646
• DOI: 10.1016/S0042-6989(98)00162-X

If distance, shape and size are judged independently from the retinal and extra-retinal information at hand, different kinds of information can be expected to dominate each judgement, so that errors in one judgement need not be consistent with errors in other judgements. In order to evaluate how independent these three judgements are, we examined how adding information that improves one judgement influences the others. Subjects adjusted the size and the global shape of a computer-simulated ellipsoid to match a tennis ball. They then indicated manually where they judged the simulated ball to be. Adding information about distance improved the three judgements in a consistent manner, demonstrating that a considerable part of the errors in all three judgements were due to misestimating the distance. Adding information about shape that is independent of distance improved subjects’ judgements of shape, but did not influence the set size or the manually indicated distance. Thus, subjects ignored conflicts between the cues when judging the shape, rather than using the conflicts to improve their estimate of the ellipsoid’s distance. We conclude that the judgements are quite independent, in the sense that no attempt is made to attain consistency, but that they do rely on some common measures, such as that of distance.