title: A long-distance stereoscopic detector for partially occluding surfaces.
abstract: An external noise technique was used to investigate the stereoscopic process that generates an illusory phantom occluder from binocularly unmatched elements. Observers were required to identify the quadrant in which a binocularly defined target was presented. We had three targets: (a) two vertical binocular bars with the unmatched portions arranged to induce a stable phantom occluder (valid), (b) the same stimuli except the image for the left eye was switched with that for the right eye therefore not inducing a stable occluder (invalid), and (c) a single binocular bar with the same unmatched portion (single-bar). For each target, the luminance contrast of the signal required for 75% correct responses was measured at four levels of external interocular noise. Contrast thresholds were found to be lower for the valid target than for both the invalid and the single-bar targets. The results suggest that the visual system has a stereoscopic detector that responds to stimuli that meet a long-distance requirement for the perception of partially occluding surfaces.
authors.affiliation: ATR Human Information Science Laboratories, 2-2-2 Hikaridai, Soraku-gun, Kyoto 6190288, Japan. hmitsudo@atr.jp
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mitsudo
authors.forename: Sachio
authors.initials: S
authors.lastname: Nakamizo
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ono
mesh_terms: D005556:Form Perception / Q000502:physiology; D006801:Humans; D009903:Optical Illusions; D010364:Pattern Recognition, Visual / Q000502:physiology; D010470:Perceptual Masking; D011601:Psychophysics; D015357:Vision Disparity; D015348:Vision, Binocular