ABSTRACT
These two movement classes follow very different principles. The major difference is that the so-called rapid movements are essentially organized in advance and run off as a unit. The slower actions tend to be more controlled by interactions and compensations for sensory information delivered during the conduct of the action (termed “response-produced feedback,” or simply “feedback”), and hence they do not rely (so) heavily on advance organization. Of course, this distinction between the processes in rapid and slow movements blurs at their border. Movements that are in the region near this border (with MT of from ~ 400 to ~1500 ms) have components that are both pre-organized and feedback controlled (see, e.g. Principles of Simple Movement in this volume). The factors that determine the relative contributions of these two kinds of control processes have been examined and modeled recently (Meyer et al. 1990). But, at the polar extremes, rapid and slow movements appear to be quite differently controlled. We will be dealing with rapid actions in this section. Other sections in this volume deal with those processes in slower actions (see e.g. Tracking).
