title: Perceptual belongingness determines the direction of lightness induction depending on grouping stability and intentionality.
abstract: Contrast and assimilation are two opposite perceptual phenomena deriving from the relationships among perceptual elements in a visual field. In contrast, perceptual differences are enhanced; while, in assimilation, they are decreased. Indeed, if contrast or assimilation occurs depends on various factors. Interestingly, Gestalt scientists explained both phenomena as the result of perceptual belongingness, giving rise to an intriguing paradox. Benary suggested that belongingness determines contrast; conversely, Fuchs suggested that it determines assimilation. This paradox can be related both to the grouping stability (stable/multi-stable) and to the grouping intentionality (intentional/non-intentional). In the present work we ran four experiments to test whether the contrast/assimilation outcomes depend on the above-mentioned variables. We found that, intentionality and multi-stability elicit assimilation; while, non-intentionality and stability elicit contrast.
authors.affiliation: Department of Life Sciences, University of Trieste, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Murgia
authors.affiliation: Department of Life Sciences, University of Trieste, Italy.
authors.forename: Valter
authors.initials: V
authors.lastname: Prpic
authors.affiliation: Department of Life Sciences, University of Trieste, Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Santoro
authors.affiliation: Department of Life Sciences, University of Trieste, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Sors
authors.affiliation: Department of Life Sciences, University of Trieste, Italy.
authors.forename: Tiziano
authors.initials: T
authors.lastname: Agostini
authors.affiliation: Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Italy. Electronic address: alessandra.galmonte@univr.it.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Galmonte
mesh_terms: D015350:Contrast Sensitivity / Q000502:physiology*; D004192:Discrimination, Psychological / Q000502:physiology*; D006801:Humans; D009903:Optical Illusions; D010775:Photic Stimulation / Q000379:methods; D011601:Psychophysics; D014796:Visual Perception / Q000502:physiology*
keywords: Assimilation; Attention; Belongingness; Contrast; Grouping; Lightness