THE DEPENDENCE OF DISCRETE MOVEMENTS ON RHYTHMIC MOVEMENTS - SIMPLE RT DURING OSCILLATORY TRACKING

Four experiments examined the time taken to initiate a discrete moveme nt of the fingers while performing rhythmical tracking movements with an arm. Simple reaction time (RT - finger flexion to a tone) was measu red at various phases of oscillations of the forearm as it tracked a v isual stimulus either in phase or antiphase. In Experiments 1 and 2, d iscrete responses were made by the oscillating hand, either parallel o r orthogonal to the plane of motion of the oscillation. In both experi ments, RT differed as a function of phase of the response cycle rather than phase of the stimulus cycle. Experiment 3, which tested RTs at d ifferent locations of a stationary hand, demonstrated that these diffe rences are not attributable to the locations at which responses were s olicited. Experiment 4 measured RT in a stationary right hand while th e left hand oscillated; again dependence on response phase was observe d. Tracking condition effects and frequency effects were interpreted i n terms of the coupling of the arm as oscillator to the visual oscilla tor; phase effects were interpreted in terms of the phase relation bet ween the rhythmic action and the discrete action.