title: Two dimensions of visibility revealed by multidimensional scaling of metacontrast.
abstract: An increasing number of studies use subjective reports of visibility, so as to delineate the domain of perceptual awareness. It is generally assumed that degrees of visibility can be ordered on a single unidimensional scale. Here, I put this assumption to test with metacontrast, one of the most studied visual masking paradigms. By means of multidimensional scaling, I show that even though metacontrast stimuli only differ along the dimension of time, the perceptual space they generate unfolds in three dimensions: time and two kinds of visibilities, that are confounded when projected onto a unitary visibility scale. I argue that metacontrast creates multidimensional complex percepts, a property that may run counter to its use as a simple modulator of visibility. More broadly the results cast doubt on the use of visibility scales that ignore the qualities of the percepts.
authors.affiliation: Laboratoire de Sciences Cognitives et Psycholinguistique, EHESS/CNRS/DEC-ENS, Institut d'Études Cognitives, École Normale Supérieure, 29, rue d'Ulm, 75005 Paris, France. jerome.sackur@gmail.com
authors.forename: Jérôme
authors.initials: J
authors.lastname: Sackur
mesh_terms: D000328:Adult; D015350:Contrast Sensitivity / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D010470:Perceptual Masking / Q000502:physiology*; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*