Fig. 2.

Experimental timeline shown for a representative block There were 18 conditions in a 2 (tool) × 3 (target size = ID) × 3 (task) design. Verbal presentation of the word “execute” (for task conditions both with and without visual feedback) or “imagine” distinguished task conditions followed by the word “stick” or “laser” designating tool condition just prior to each block The stick condition is shown here for illustrative purposes. After the instructional cue, participants heard the word “go” and released the button with the left hand. At the release of the button, they also began performing the task (8 full cycles of pointing back and forth between the start box and one of the target boxes–20 mm, 40 mm, or 80 mm). When finished, they pressed the button with the left hand. The button presses allowed us to record durations for both imagined and executed trials. A depiction of the three task conditions is shown: closed-loop–saw hand/tool moving via live video, open-loop–saw a captured image of hand/tool, imagine—did not physically move, just mentally simulated the movements, but saw a live video of stationary hand/tool. After each 12 s experimental block, a black cross on a white screen appeared for participants to fixate during a 12 s rest period.