Document Detail

Differential processing: towards a unified model of direction and speed perception.
MedLine Citation:
PMID:  23994486     Owner:  NLM     Status:  MEDLINE    
In two experiments, we demonstrate a misperception of the velocity of a random-dot stimulus moving in the presence of a static line oriented obliquely to the direction of dot motion. As shown in previous studies, the perceived direction of the dots is shifted away from the orientation of the static line, with the size of the shift varying as a function of line orientation relative to dot direction (the statically-induced direction illusion, or 'SDI'). In addition, we report a novel effect - that perceived speed also varies as a function of relative line orientation, decreasing systematically as the angle is reduced from 90° to 0°. We propose that these illusions both stem from the differential processing of object-relative and non-object-relative component velocities, with the latter being perceptually underestimated with respect to the former by a constant ratio. Although previous proposals regarding the SDI have not allowed quantitative accounts, we present a unified formal model of perceived velocity (both direction and speed) with the magnitude of this ratio as the only free parameter. The model was successful in accounting for the angular repulsion of motion direction across line orientations, and in predicting the systematic decrease in perceived velocity as the line's angle was reduced. Although fitting for direction and speed produced different best-fit values of the ratio of underestimation of non-object-relative motion compared to object-relative motion (with the ratio for speed being larger than that for direction) this discrepancy may be due to differences in the psychophysical procedures for measuring direction and speed.
Max Farrell-Whelan; Kevin R Brooks
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2013-08-30
Journal Detail:
Title:  Vision research     Volume:  92     ISSN:  1878-5646     ISO Abbreviation:  Vision Res.     Publication Date:  2013 Nov 
Date Detail:
Created Date:  2013-10-21     Completed Date:  2014-04-25     Revised Date:  2014-07-28    
Medline Journal Info:
Nlm Unique ID:  0417402     Medline TA:  Vision Res     Country:  England    
Other Details:
Languages:  eng     Pagination:  10-8     Citation Subset:  IM    
Copyright Information:
Copyright © 2013 Elsevier B.V. All rights reserved.
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MeSH Terms
Analysis of Variance
Models, Psychological
Models, Theoretical
Motion Perception / physiology*
Optical Illusions / physiology
Photic Stimulation / methods
Erratum In:
Vision Res. 2014 Mar;96(1):150

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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