The synchronization of human arm movements to external events.

Previous research revealed the existence of coupling mechanisms (e.g. iso-directionality) at the level of perception and action. The present experiment investigated how the strength of the perception-action coupling affected synchronization performance. Arm movements were to be synchronized with a moving light that traveled back and forth from the left to the right side of a runway. Four experimental conditions were administered representing the orthogonal combination of two viewing conditions (intermittent vs. continuous) and two synchronization modes (in-phase, i.e. arm moving in the same direction as the light vs. anti-phase, i.e. arm moving in the opposite direction). Performance outcome measures, movement kinematics, and relative phase were used to examine the data. The results revealed a better synchronization performance when the arm and light traveled in the same direction (iso-directionality) during the continuous viewing condition. Apparently, the strength of the perception-action coupling has a severe impact on the quality of the synchronization of an arm movement to an external event.