Figure 1. Bimanual tracking task (BTT).

(A) Task set-up. Subjects were seated in front of a computer screen on which the task was displayed. The response apparatus consisted of two dials which were fixated on a ramp. Direct vision of the forearms was prevented by a horizontal table-top bench. (B) Frequency ratios and coordination directions. Schematic drawing of the target lines shown on the screen, from which subjects can deduct the three frequency ratios (1∶1, 2∶3 and 1∶2) and coordination directions [clockwise (CW) and counterclockwise (CCW)]. The coordination directions inwards (IN) and outwards (OUT) are shown here, but are not a part of the training protocol.