ABSTRACT
A series of experiments is reported, concerned with the advance planning of movements, that were themselves systematically varied in the complexity of their serial organization. Response complexity is defined in terms of the response units that are mapped onto an invariant motor schema. Response units are specified in three forms: (1) the number of muscle synergies; (2) the number of phases of muscle activity; (3) the number of sequencing instructions. Probe RT procedures are used with speed movements that varied systematically in terms of these three factors. Probes are presented both before and during the primary movement. The results show that probe RT is lengthened for probes presented during the latency phase of the movement, as well as during the early part of some of the movements. The lengthening of the probe RT is closely related to the number of sequencing instructions. It is proposed that two forms of advance planning have been observed: one in which the whole response is planned in advance of execution and another in which the planning continues into the early stages of the execution of the movement. The latter form of planning is associated with the more complex movements.
