The extent of interlimb transfer following adaptation to a novel visuomotor condition does not depend on awareness of the condition

There is a controversy in the literature as to whether transfer of motor learning across the arms occurs because of an individual's cognitive awareness of the learned condition. The purpose of this study was to test whether the extent of interlimb transfer following adaptation to a novel visuomotor rotation with one arm, as well as the rate of learning acquired by the other arm, would vary depending on the subjects' awareness of the rotation condition. Awareness of the condition was varied by employing three experimental conditions. In one condition, visual rotation of the display up to 32° was gradually introduced to minimize the subjects' awareness of the rotation during targeted reaching movement. In another condition, the 32° rotation was abruptly introduced from the beginning of the adaptation session. Finally, the subjects were informed regarding the rotation prior to the adaptation session. After adaptation with the left arm under the three conditions, subjects performed reaching movement with the right arm under the same 32° rotation condition. Our results showed that the amount of initial transfer, and also the changes in performance with the right arm, did not vary significantly across the three conditions. This finding suggests that interlimb transfer of visuomotor adaptation does not occur based on an individual's awareness of the manipulation, but rather as a result of implicit generalization of the obtained visuomotor transformation across the arms.