Document Detail

Strength and variability of the backscroll illusion.
MedLine Citation:
PMID:  19236893     Owner:  NLM     Status:  MEDLINE    
When a walking person is presented in a movie, the background image appears to move in a direction opposite to that of the person's locomotion. This study aimed to quantify the strength of this backscroll illusion and to examine interobserver and intraobserver variability. Stimuli were movie clips that presented a walking person in profile against a background of dynamic grating composed of two vertical sinusoidal gratings moving in opposite directions. Employing a motion-nulling method, we controlled the ratio of luminance contrasts of the component gratings to determine points that canceled the percept of unidirectional motion in the grating background. Results across 50 observers showed that the backscroll illusion disappeared when a luminance contrast of moving grating components consistent with a walker's direction was about twice as high as that for the opposite motion direction. Intraobserver variability was relatively small. However, nulling points for individual observers were more variable under conditions with dynamically moving walkers than conditions presenting only a static picture of a walker. We speculated on the underlying mechanisms of the backscroll illusion in relation to similar phenomena.
Kiyoshi Fujimoto; Akihiro Yagi; Takao Sato
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2009-02-21
Journal Detail:
Title:  Vision research     Volume:  49     ISSN:  1878-5646     ISO Abbreviation:  Vision Res.     Publication Date:  2009 Mar 
Date Detail:
Created Date:  2009-04-20     Completed Date:  2009-07-01     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0417402     Medline TA:  Vision Res     Country:  England    
Other Details:
Languages:  eng     Pagination:  759-64     Citation Subset:  IM    
Department of Psychology, School of Humanities, Kwansei Gakuin University, 1-1-155 Uegahara, Nishinomiya, Hyogo, 662-8501, Japan.
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MeSH Terms
Motion Perception / physiology*
Motion Pictures as Topic
Observer Variation
Optical Illusions / physiology*
Photic Stimulation / methods
Young Adult

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