Figure 2.
Visual, motor, and predicted CC performance versus elapsed time (participant 4). Visual accuracy, motor accuracy, and predicted CC condition reach endpoint offsets (dotted, dashed, and solid lines, respectively) are plotted as functions of reach initiation time (x-axis) for participant 4. For the VB and CC curves, reach initiation time is equivalent to tV. For the MB curve, reach initiation time is equivalent to (1200 − tM) and assumes that the participant used all of the remaining trial time after leaving the start button as tM, so that he or she finishes the reach at a trial time of 1200 ms. The y-axis represents the SD (std. dev.; here and in subsequent figures) of the reach endpoint offsets from the target position, and thus lower values mean higher accuracy and better performance. The three boxes represent low, medium (Med.; here and in subsequent figures), and high dot scatter levels. Visual accuracy curves were estimated using VB condition data (Eq. 3), motor accuracy curves were estimated using MB condition data (Eq. 4), and CC endpoint accuracy was predicted by combining the visual and motor variability functions (Eq. 5). The solid, vertical line in each box indicates the reach initiation time that minimizes the CC condition performance, σC (i.e., those tV values that are predicted to yield maximum performance). Across dot scatter levels, the visual accuracy curves differ, and the tV that is predicted to yield maximum performance increases (numbers with arrows).