Invariants in loaded goal directed movements

Goal directed movements, executed by means of a manipulator with various dynamics, were investigated in order to establish to what extent the loading affects the executed movement. The desired movement concept, together with a describing function model for goal directed movements, was applied to parameterize the movements. Analysis of the results showed that the position trajectories, when scaled by means of a fundamental scale property, with respect to the maximum velocity of the desired movements, were invariant under variation of the manipulator dynamics. From this invariance in the phasing of the movements, it was concluded that the subjects fully adapted to the applied loads.