Cinematographical Analysis of Movement Pathway Constraints in Rapid Target-Striking Tasks.

Several features of the actual movement pathway in two rapid target-striking tasks were quantified by using high-speed cinematography, and whether the movement pathway is constrained as a function of the accuracy 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 the left of a start position and then, depending on the condition, moved another 10 cm to hit either a 6-cm- or 1.5-cm-diameter target. Subtended angles were 17.1 and 4.3 degrees for the large and small second-target conditions, respectively. Fifty trials per condition were performed, the last 3 of which were filmed at 120 Hz. The vertical dimension of movement (peak height along the z-axis) was captured directly from the camera view, whereas the horizontal (y-axis) dimension, that is, the dimension orthogonal to the principal direction of motion, was captured through a mirror positioned above the target board. Reaction times and movement times were significantly longer in the small second-target condition, thus replicating the well-known response complexity effect. Kinematic analyses revealed that when the subtended angle was smaller, there was significantly less horizontal pathway deviation as well 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.