Planning and execution of hand movements.

The presented approach focuses on the attempt to specify strategies of visually organizing sequences of different hand movements and the resulting fine-control of movement close to the target, since in skilled activities our ability to sequence a number of separate movements each having different spatiotemporal characteristics is of central importance. Sequences of different moves have been analysed here. After a gross distance covering part of the move, small correction movements are performed close to the target to reduce the position error. The length of the required correction movements and the corresponding positioning time increase with target distance. In order to investigate motor control strategies two different tasks, with and without time pressure, have been designed. Time pressure forces the subjects to finish the previous move and to prepare the next move simultaneously. Absolute, constant and variable errors revealed that under time pressure the subject changes the control strategy by increasing the constant and reducting the variable error.