NATURAL UNCONSTRAINED MOVEMENTS OBEY RULES DIFFERENT FROM CONSTRAINEDELEMENTARY MOVEMENTS

The concept of a conservative control strategy minimizing the number o f degrees of freedom used is criticised with reference to 3-D simple r eaching and grasping experiments. The vector error in a redundant syst em would not be the prime controlled variable, but rather the posture for reaching, as exemplified by nearly straight displacements in joint space as opposed to curved ones in task space.