Asymmetric interlimb interference during the performance of a dynamic bimanual task.

The control of a dynamic bimanual task was examined by manipulating two independent factors that potentially influence interlimb interference. Subjects attempted to perform a unidirectional movement with either their preferred or nonpreferred arm while concurrently producing a sequential movement with the contralateral arm. The magnitude of force required to produce the more complex, sequential action was manipulated in addition to the arm with which it was performed. The degree of interlimb interference was determined through an analysis of limb kinematics. A clear performance asymmetry was noted, with greater interference evident when the sequential action was generated by the nonpreferred left arm than by the preferred right arm. The level of force needed to produce the sequential movement also directly influenced interlimb interference, but this effect was bilaterally symmetrical. The findings are generally consistent with a hierarchical view of movement organization comprising lateralized hemispheric specialization for the organization of time-domain characteristics of sequential actions, followed by nonlateralized metrical scaling of force parameters. Implications of the findings for "dynamical" descriptions of bimanual actions are also discussed.