A Finite-State Description of Coordination in a Two-Handed Target Acquisition Task

A position control stick with one hand and a velocity control stick with the other hand were manipulated in order to capture a moving target displayed on an oscilloscope screen. The two control sticks were additively coupled. In order to understand the coordination of the two control sticks, event-based first-order Markov "activity sequence generators" were constructed for individual subjects. These discrete probabilistic structures are closely related to each subject\´s overall plan or general strategy for the capture task. Striking individual differences and strategic errors in performance were revealed. When combined with additional time-conditioned (open-loop) and error-conditioned (closed-loop) details, the activity sequence generators provide a basis for a hierarchic description of this perceptual-motor skill.