Asymmetrical intermanual transfer of learning in a sensorimotor task.

We examined the influence of the hand employed in sensorimotor learning on the acquired sequence knowledge in a serial reaction time task. Right-handed subjects trained either with the dominant or with the nondominant hand sequences of finger postures in response to a corresponding stimulus sequence. In the course of training, they were repeatedly asked to switch to the opposite hand, either responding to the original stimulus sequence with nonhomologues fingers or to the mirror-ordered sequence of stimuli with homologues fingers. When the right hand was used at acquisition, transfer to the same stimulus sequence increased with practice. In contrast, when the left hand was trained, transfer to the homologues finger sequence increased with practice. The results indicate qualitative differences in the acquired sequence knowledge controlling the dominant and the nondominant arm systems.