Do the Principles of Motor Program Editing Apply to Longer Sequences of Rapid Aiming Movements? Part II

In Part I of this study, it was shown that performing a shorter distance aiming movement prior to a longer distance aiming movement resulted in overshooting of the short movement and undershooting of the longer movement compared to control conditions. However, the finding was limited, unexpectedly, to the nondominant hand. To replicate the prior result and to determine the effect of practice organization on movement accuracy, right-handed (n =24) participants (aged 18-22) produced a sequence of three rapid lever reversals combining short (20°) and long (60°) movements with an intermovement interval of 2.5 s with the dominant hand. Greater overshooting of the short movements and greater undershooting of the long movement was shown with random practice compared to blocked practice for both same distance and different distance sequences, although spatial errors were greater in the different conditions compared to the same conditions. Overall, the experiment demonstrated parameter value switching and practice organization as two major sources of spatial inaccuracy in sequential aiming movements.