title: Context affects lightness at the level of surfaces.
abstract: Visual perception of object attributes such as surface lightness is crucial for successful interaction with the environment. How the visual system assigns lightness to image regions is not yet understood. It has been shown that the context in which a surface is embedded influences its perceived lightness, but whether that influence involves predominantly low-, mid-, or high-level visual mechanisms has not been resolved. To answer this question, we measured whether perceptual attributes of target image regions affected their perceived lightness when they were placed in different contexts. We varied the sharpness of the edge while keeping total target flux fixed. Targets with a sharp edge were consistent with the perceptual interpretation of a surface, and in that case, observers perceived significant brightening or darkening of the target. Targets with blurred edges rather appeared to be spotlights instead of surfaces; for targets with blurred edges, there was much less of a contextual effect on target lightness. The results indicate that the effect of context on the lightness of an image region is not fixed but is strongly affected by image manipulations that modify the perceptual attributes of the target, implying that a mid-level scene interpretation affects lightness perception.
authors.affiliation: Modelling of Cognitive Processes Group, Department of Software Engineering and Theoretical Computer Science, Technische Universität Berlin, Berlin, Germany.
authors.forename: Marianne
authors.initials: M
authors.lastname: Maertens
authors.affiliation: Modelling of Cognitive Processes Group, Department of Software Engineering and Theoretical Computer Science, Technische Universität Berlin, Berlin, GermanyAG Neuronale Informationsverarbeitung, Mathematisch-Naturwissenschaftliche Fakultät, Eberhard Karls Universität, Tübingen, GermanyBernstein Center für Computational Neuroscience, Tübingen, GermanyMax-Planck-Institut für Intelligente Systeme, Abteilung Empirische Inferenz, Tübingen, GermanyCenter for Neural Science, New York University, New York, NY, USA.
authors.forename: Felix A
authors.initials: FA
authors.lastname: Wichmann
authors.affiliation: Modelling of Cognitive Processes Group, Department of Software Engineering and Theoretical Computer Science, Technische Universität Berlin, Berlin, GermanyAG Neuronale Informationsverarbeitung, Mathematisch-Naturwissenschaftliche Fakultät, Eberhard Karls Universität, Tübingen, GermanyBernstein Center für Computational Neuroscience, Tübingen, GermanyMax-Planck-Institut für Intelligente Systeme, Abteilung Empirische Inferenz, Tübingen, GermanyCenter for Neural Science, New York University, New York, NY, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Shapley
mesh_terms: D000328:Adult; D015350:Contrast Sensitivity / Q000502:physiology; D005260:Female; D006801:Humans; D008027:Light; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology*; D012160:Retina / Q000502:physiology*; D013499:Surface Properties; D055815:Young Adult
keywords: assimilation; context; mid-level vision; surface lightness