Experimental apparatus and stimuli used in the experiments.

<p>(A) Side view of participants' initial position before the execution of an actual movement. (B) Trajectories used for experiments 1, 3, and 4. Trajectories 2, 3 and 4 are characterized by two curves with an increasing curvature. The radius of curvature (defined as the inverse of the curvature) at these curves is 15.2 cm, 8.8 cm, and 2.7 cm, respectively. Trajectories 2, 3 and 4 induced 45deg, 90deg and 135deg changes of directions at each curve, respectively. Thus, the absolute cumulative amount of direction change ranged from 0deg (trajectory 1) to 270deg (trajectory 4). (C) Trajectories used for Experiment 2 and 4. Trajectories in Panels B and C have the same length (160 cm). Additionally, trajectories in Panel C have the same curvature at curves (radius of curvature of 10 cm) and an increasing number of inflexions from 1 to 5. The absolute cumulated changes of direction always summed to 360deg.