Prior knowledge on the illumination position

Visual perception is fundamentally ambiguous because an infinite number of three-dimensional scenes are consistent with our retinal images. To circumvent these ambiguities, the visual system uses prior knowledge such as the assumption that light is coming from above our head. The use of such assumpt...

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Bibliographic Details
Published in:Cognition 2001-08, Vol.81 (1), p.B1-B9
Main Authors: Mamassian, Pascal, Goutcher, Ross
Format: Article
Language:English
Subjects:
Adolescent
Adult
Biological and medical sciences
Cognition
Female
Functional Laterality
Fundamental and applied biological sciences. Psychology
Humans
Illumination position
Knowledge
Male
Memory
Middle Aged
Perception
Prior constraints
Psychology. Psychoanalysis. Psychiatry
Psychology. Psychophysiology
Shape-from-shading
Task Performance and Analysis
Vision
Visual Perception - physiology
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Summary:Visual perception is fundamentally ambiguous because an infinite number of three-dimensional scenes are consistent with our retinal images. To circumvent these ambiguities, the visual system uses prior knowledge such as the assumption that light is coming from above our head. The use of such assumptions is rational when these assumptions are related to statistical regularities of our environment. In confirmation of previous visual search experiments, we demonstrate here that the assumption on the illumination position is in fact biased to the above-left rather than directly above. This bias to the left reaches 26 degrees on average in a more direct shape discrimination task. Both right-handed and left-handed observers have a similar leftward bias. We discuss the possible origins of this singular bias on the illumination position.
ISSN:0010-0277
1873-7838
DOI:10.1016/S0010-0277(01)00116-0