Figure 4.
Speed–accuracy trade-off performance. Each panel shows values (means, across subjects, of subject's mean values, ±SE) of kinematic variables in the seven task conditions. The y-axis shows peak velocity (in centimeters per second; A), MT (in milliseconds; B), systematic (Syst.) extent error (in centimeters; C), and variable (Var.) error (σg, in square centimeters; D). The x-axis indicates condition (in order of execution), defined by target distance (6, 12, 16 cm) and required speed range (see Fig. 2). For every panel, open squares and solid lines refer to data from PD patients, and filled circles and dotted lines refer to data from control (CTL) subjects. For every variable in the four panels, each point indicates the mean, across subjects in each group, of every subject's mean value for valid trials in each condition. Error bars indicate SE. Note that Speed near the horizontal axis in all panels refers to range of required speeds, whereas peak velocity on the vertical axis in A refers to the speed actually attained by subjects. Where error bars are not visible, they are smaller than the plot symbol indicating the mean (e.g., in A and B).