The Coordination of Bimanual Synchronous and Alternating Tapping Sequences

Abstract

The present article reports two experiments addressing the question of how we achieve bimanual coordination. The simple reaction time (RT) paradigm was used, employing a repetitive tapping task involving sequences of five taps in which speed and force of tapping were manipulated. In the first experiment, subjects were required to tap synchronously with the right and left index finger. In Experiment 2, subjects were required to produce alternating taps with the right and left index fingers. Three force conditions and four speed conditions were employed in both experiments. Subjects were required to tap all five taps with the same force (no-stress condition), or they were required to accentuate the force on either Tap 2 (stress Tap 2 condition) or Tap 4 (stress Tap 4 condition) with the left hand only. They were instructed to maintain the interval between the taps at either 150, 250, 350, or 450 ms. The results suggest that in synchronous tapping the two hands are coupled temporally and that there is entrainment of force across the two hands. That is, the two hands appear to be under the control of one motor program. Although the hands appeared to be temporally coupled when the subjects were required to perform alternating tapping, there was no evidence of a coupling with force gradation. The implication of these results for motor program theory are discussed.

Key Words:

• bimanual coordination
• force gradation
• motor programming