Document Detail

Shape from shadows.
MedLine Citation:
PMID:  2522531     Owner:  NLM     Status:  MEDLINE    
The colors, textures, and shapes of shadows are physically constrained in several ways in natural scenes. The visual system appears to ignore these constraints, however, and to accept many patterns as shadows even though they could not occur naturally. In the stimuli that we have studied, the only requirements for the perception of depth due to shadows were that shadow regions be darker than the surrounding, nonshadow regions and that there be consistent contrast polarity along the shadow border. Three-dimensional shape due to shadows was perceived when shadow areas were filled with colors or textures that could not occur in natural scenes, when shadow and nonshadow regions had textures that moved in different directions, or when they were presented on different depth planes. The results suggest that the interpretation of shadows begins with the identification of acceptable shadow borders by a cooperative process that requires consistent contrast polarity across a range of scales at each point along the border. Finally, we discuss how the identification of a shadow region can help the visual system to patch together areas that are separated by shadow boundaries, to identify directions of surface curvature, and to select a preferred three-dimensional interpretation while rejecting others.
P Cavanagh; Y G Leclerc
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Journal of experimental psychology. Human perception and performance     Volume:  15     ISSN:  0096-1523     ISO Abbreviation:  J Exp Psychol Hum Percept Perform     Publication Date:  1989 Feb 
Date Detail:
Created Date:  1989-05-05     Completed Date:  1989-05-05     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7502589     Medline TA:  J Exp Psychol Hum Percept Perform     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  3-27     Citation Subset:  IM    
Département de Psychologie, Université de Montréal, Québec, Canada.
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MeSH Terms
Color Perception
Depth Perception
Discrimination Learning*
Dominance, Cerebral
Form Perception*
Motion Perception
Pattern Recognition, Visual*
Size Perception
Erratum In:
J Exp Psychol Hum Percept 1990 Nov;16(4):910

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