Constraints in the performance of bimanual tasks and their expression in unskilled and skilled subjects

Unskilled and skilled subjects were asked to perform a variety of bimanual tapping tasks. Three major effects were seen. First, right-handers performed dual tasks better when the preferred hand took the “figure” and when the nonpreferred hand took the “ground” of the dual movement. This effect was not seen in left-handers. Second, subjects performed a simple slow/fast dual task better when they commenced the task with the fast rather than with the slow hand. This effect was seen in right- and lefthanders. Third, both unskilled and skilled subjects showed marked interdependence of movements such that performance of one hand was a function of movements in the other hand. The results are in agreement with a model that postulates the presence of a superordinate control mechanism that initiates action in subordinate control mechanisms, which in turn set the movement trajectories in the two hands. The results also show that attention is an important factor in the interaction between these two levels of control.