Interlimb coordination during a cooperative bimanual object manipulation task.

This experiment examined asymmetries in the execution of an object manipulation task that requires the coordinated use of both hands. To this end, twenty right-hand-dominant participants performed a bimanual object manipulation task, which required that they reach for and grasp two objects located on a tabletop, fit the two objects through a hole in a horizontally or vertically oriented fitting board, and then rotate the objects 180° to produce a "beep" tone. Overall, the two hands were highly synchronized at the start, but not at end, of each movement phase. The decrease in interlimb coupling at later stages of the movement phase was primarily driven by the shorter movement time values for the dominant right hand. In addition, degree of left object rotation was greater than the right object, irrespective of board orientation. In sum, the results suggest that manual asymmetries and role assignment are not hardwired constraints, but depend on the overall task constraints and the manner in which the task is conceptualized.