phase dynamic model of systematic error in simple copying tasks

• Published in: Biological cybernetics Vol. 101; no. 3; pp. 201 - 213
• Main Authors: Dubey, Saguna, Sambaraju, Sandeep, Cautha, Sarat Chandra, Arya, Vednath, Chakravarthy, V. S
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Berlin/Heidelberg : Springer-Verlag 01.09.2009; Springer-Verlag; Springer Nature B.V
• Subjects: Adult; Algorithms; Bioinformatics; Biological Clocks - physiology; Biomedical and Life Sciences; Biomedicine; Central Nervous System - physiology; Complex Systems; Computer Appl. in Life Sciences; Computer Simulation; Copying; Cybernetics; Error analysis; Female; Handwriting; Handwriting analysis; Humans; Imitative Behavior - physiology; Male; Mathematical Concepts; Motor Skills - physiology; Movement - physiology; Neurobiology; Neurosciences; Nonlinear Dynamics; Nonlinear oscillators; Original Paper; Phase dynamics; Psychomotor Performance - physiology; Visuomotor transformation; Young Adult; Visuomotor transformation; Nonlinear oscillators; Handwriting; Phase dynamics; Copying
• ISSN: 0340-1200; 1432-0770; 1432-0770
• DOI: 10.1007/s00422-009-0330-9

A crucial insight into handwriting dynamics is embodied in the idea that stable, robust handwriting movements correspond to attractors of an oscillatory dynamical system. We present a phase dynamic model of visuomotor performance involved in copying simple oriented lines. Our studies on human performance in copying oriented lines revealed a systematic error pattern in orientation of drawn lines, i.e., lines at certain orientation are drawn more accurately than at other values. Furthermore, human subjects exhibit “flips” in direction at certain characteristic orientations. It is argued that this flipping behavior has its roots in the fact that copying process is inherently ambiguous—a line of given orientation may be drawn in two different (mutually opposite) directions producing the same end result. The systematic error patterns seen in human copying performance is probably a result of the attempt of our visuomotor system to cope with this ambiguity and still be able to produce accurate copying movements. The proposed nonlinear phase-dynamic model explains the experimentally observed copying error pattern and also the flipping behavior with remarkable accuracy.