Strategy Differences in Oscillatory Tracking: Stimulus-Hand Versus Stimulus-Manipulandum Coupling

In 3 experiments, participants matched the rotations of a unimanually grasped wheel to a visual oscillation. Two coordination modes were studied: in-phase coordination (no phase difference between stimulus and movement) and anti-phase coordination (180 degrees phase difference). The hand grasped the wheel at either the 12:00 or the 6:00 position. Stimulus frequency, hand placement, phasing, and visibility (whether the hand and wheel were visible) all affected movement amplitude and stability. There were large individual differences especially at the 6:00 position; some participants appeared to couple movements of the wheel to stimulus oscillations, some coupled movements of the hand, and some did both. The results parallel stimulus-response compatibility effects in a similar choice reaction time task and reiterate J. A. S. Kelso's (1995) emphasis on studying intrinsic coupling dynamics at the level of the individual, where apparent differences in strategy can be observed.