ABSTRACT

Each of these controllers is considered to possess limited performance resources-or performance capacities-necessary to carry out their control functions. Performance resources are characterized by dimensions of performance, which for controllers are accuracy of movement (including steadiness and stability) and speed of movement. Accuracy is the most important of these and can be divided into four major classes:

1. Spatial accuracy-Required by tasks which are self-paced and for which time taken is of secondary or minimal importance and includes tracing (e.g., map-tracking), walking, reaching, grasping, and, in fact, many activities of daily living. Limitation in speed performance resources should have no inuence on this class of accuracy.