Segmentation and coupling in complex movements.

Abstract

In two experiments we explore the structure of complex sequences of drawing movements. We find that in these movements a single parameter--the velocity gain factor--relates the geometrical and kinematic aspects of the movement trajectory via a two-thirds power law. In Experiment 1 we investigate the relation between the velocity gain factor and the linear extent of the trajectory. In Experiment 2 we demonstrate that the gain factor provides a criterion for segmenting the movement into distinct units of motor action, and we investigate the effects of the speed of execution on this segmentation. A theoretical analysis shows that the results of both Experiments 1 and 2 can be given a unitary interpretation by assuming a coupling function of variable strength between segments. The general problem of representing motor programs is discussed within this theoretical framework.

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2. Biological movements look uniform: Evidence of motor-perceptual interactions.
   Viviani, Paolo, Stucchi, Natale · 1992 · Journal of Experimental Psychology: Human Perception and Performance
3. Cognitive spatial-motor processes: 3. Motor cortical prediction of movement direction during an instructed delay period
   Georgopoulos, A.P., Crutcher, M.D., Schwartz, A.B. · 1989 · Experimental Brain Research
4. Dynamics systems vs. optimal control — a unifying view
   Schaal, Stefan, Mohajerian, Peyman, Ijspeert, Auke · 2007 · Progress in Brain Research
5. Smoothness Maximization Along a Predefined Path Accurately Predicts the Speed Profiles of Complex Arm Movements
   Todorov, Emanuel, Jordan, Michael I. · 1998 · Journal of Neurophysiology

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