Influence of stimulus amplitude on unintended visuomotor entrainment

Rhythmic limb movements have been shown to spontaneously coordinate with rhythmic environmental stimuli. Previous research has demonstrated how such entrainment depends on the difference between the movement periods of the limb and the stimulus, and on the degree to which the actor visually tracks the stimulus. Here we present an experiment that investigated how stimulus amplitude influences unintended visuomotor entrainment. Participants performed rhythmic forearm movements while visually tracking an oscillating stimulus. The amplitude and period of stimulus motion were manipulated. Larger stimulus amplitudes resulted in stronger entrainment irrespective of how participants visually tracked the movements of the stimulus. Visual tracking, however, did result in increased entrainment for large, but not small, stimulus amplitudes. Collectively, the results indicate that the movement amplitude of environmental stimuli plays a significant role in the emergence of unintended visuomotor entrainment.