Fig. 2

Raw data. A Finger recognition task. 10 successive trials. Stippled colored line: one color per target finger. Solid lines: one corresponding color per finger. Y-axis > 0: vertical position (pixel) of the respective fingertip in contact with the tablet (horizontal x-position not shown). Y-axis = 0: fingertip lift-off. A finger tap is indicated as a lift-off from the initial position on the tablet and a subsequent touch down. Correct tap: target and effector (finger) color correspond and tap occurs during target finger display. Note error tap on trial 4: target finger = ring finger, but the tap involved the ring and the middle finger. Similar type of data were recorded for Rhythm tapping and Multi-finger tapping. B Line tracking. Entire target trajectory (black trace) and effected index finger trajectory (blue) over the surface of the tablet. At any given time only a segment of 5 cm of the continuously but unpredictably moving target curve was visible. The tracking error (orange) corresponds to the area between the target and the effected trajectory