Figure 1. Experimental task.

A: Sketch of the real Skittles task. A ball is suspended on a string and swings around the center post with the objective of knocking down the skittle at the opposite side. B: Experimental set-up. Participants operate a lever to throw the virtual ball on the screen in front of them with the goal to hit the target located behind the center post. The angular displacement of the participant's forearm is measured by a potentiometer and recorded by the computer. C: Execution and result space of the Skittles task. For each combination of the execution variables release angle and velocity the color codes the result variable, the minimal distance (d) of the resulting ball trajectory to the target (error). White denotes the solution manifold with zero-error solutions. Superimposed in white is the trajectory of one throw with its moment of release (white circle) at 98° and 4 m/s.