Protocol.

<p>For each trial, the target was presented 15 cm away from the starting position in front of the subject (target presentation phase). The width of the target could either be 0.5 cm, or 8 cm while its length stayed constant (0.5 cm). As soon as the hand of the subject left the starting position (movement phase), the cursor indicating the position of the hand with respect to the target became a very large horizontal bar that spanned the width of the screen. Veridical hand position was provided after movement end in order to provide feedback about movement accuracy (feedback phase). The target became blue if movement duration was too long, yellow if movement duration was too short and green if movement duration was between 500 and 600 ms. One point could be earned for good movement speed and another point could be earned for good accuracy. The total number of points collected so far in the block was displayed at the end of each trial (94 points in the illustration). For experiments 3 and 4, subjects were instructed to pass through the opening in a circle rather than to stop on a rectangular target (right panel). The hand cursor was replaced by a circle whose radius increased with the distance travelled by the hand.