CINEMATOGRAPHICAL ANALYSIS OF MOVEMENT PATHWAY CONSTRAINTS IN RAPID TARGET-STRIKING TASKS

Several features of the actual movement pathway in two rapid target-st riking tasks were quantified by using high-speed cinematography, and w hether the movement pathway is constrained as a function of the accura cy demands imposed by the size of the subtended angle was determined. Subjects (N = 16) first hit an 8-cm-diameter target located 10 cm to t he left of a start position and then, depending on the condition, move d another 10 cm to hit either a 6-cm- or 1.5-cm-diameter target. Subte nded angles were 17.1 and 4.3 degrees for the large and small second-t arget conditions, respectively. Fifty trials per condition were perfor med, the last 3 of which were filmed at 120 Hz. The vertical dimension of move ment (peak height along the z-axis) was captured directly fro m the camera view, whereas the horizontal (y-axis) dimension, that is, the dimension orthogonal to the principal direction of motion, was ca ptured through a mirror positioned above the target board. Reaction ti mes and movement times were significantly longer in the small second-t arget condition, thus replicating the well-known response complexity e ffect. Kinematic analyses revealed that when the subtended angle was s maller, there was significantly less horizontal pathway deviation as w ell as significantly higher peak vertical displacement in the movement . Therefore, the accuracy demands imposed by a smaller subtended angle do constrain the actual movement pathway.