title: Sighting-down and the Poggendorff illusion: a mystery within a mystery.
abstract: As reported before, sighting-down one of the diagonal lines on a typical Poggendorff pattern will reduce the illusion even if that situation is only pictorial. But here it is also argued that sighting-down itself requires further understanding.
authors.affiliation: Department of Psychology, University of California, Davis 95616.
authors.forename: T E
authors.initials: TE
authors.lastname: Parks
mesh_terms: D003867:Depth Perception; D004215:Distance Perception; D005260:Female; D005556:Form Perception; D006801:Humans; D008297:Male; D009903:Optical Illusions