Document Detail

Three-dimensional arm movements at constant equi-affine speed.
MedLine Citation:
PMID:  18678364     Owner:  NLM     Status:  MEDLINE    
It has long been acknowledged that planar hand drawing movements conform to a relationship between movement speed and shape, such that movement speed is inversely proportional to the curvature to the power of one-third. Previous literature has detailed potential explanations for the power law's existence as well as systematic deviations from it. However, the case of speed-shape relations for three-dimensional (3D) drawing movements has remained largely unstudied. In this paper we first derive a generalization of the planar power law to 3D movements, which is based on the principle that this power law implies motion at constant equi-affine speed. This generalization results in a 3D power law where speed is inversely related to the one-third power of the curvature multiplied by the one-sixth power of the torsion. Next, we present data from human 3D scribbling movements, and compare the obtained speed-shape relation to that predicted by the 3D power law. Our results indicate that the introduction of the torsion term into the 3D power law accounts for significantly more of the variance in speed-shape relations of the movement data and that the obtained exponents are very close to the predicted values.
Frank E Pollick; Uri Maoz; Amir A Handzel; Peter J Giblin; Guillermo Sapiro; Tamar Flash
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2008-06-28
Journal Detail:
Title:  Cortex; a journal devoted to the study of the nervous system and behavior     Volume:  45     ISSN:  0010-9452     ISO Abbreviation:  Cortex     Publication Date:  2009 Mar 
Date Detail:
Created Date:  2009-02-02     Completed Date:  2009-06-24     Revised Date:  2009-11-11    
Medline Journal Info:
Nlm Unique ID:  0100725     Medline TA:  Cortex     Country:  Italy    
Other Details:
Languages:  eng     Pagination:  325-39     Citation Subset:  IM    
Department of Psychology, University of Glasgow, United Kingdom.
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MeSH Terms
Biomechanics / physiology
Generalization (Psychology) / physiology
Imitative Behavior / physiology*
Middle Aged
Motion Perception / physiology*
Movement / physiology*
Psychomotor Performance / physiology*
Space Perception / physiology*
Young Adult

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