Tapping force variability influences temporal precision in paced finger tapping.

The ideas about the origins and role of motor variability have been revised in recent years after realizing that a strictly peripheral origin is not sufficient to explain many observed aspects of brain function. Among these, time processing is emerging as one of the least studied functions where motor variability might have a critical role. Time processing in the range of hundreds of milliseconds includes sensorimotor synchronization (SMS), where both sensory and motor timing processes play in parallel. Paced finger tapping, where a person taps in synchrony with a periodic sequence of brief stimuli as in keeping pace with music, is one of the most common tasks to study SMS. The main observable is the asynchrony, that is the time difference between every response and the corresponding stimulus along the sequence. Here we report that the variability of asynchronies in a paced finger-tapping experiment ([Formula: see text]) is correlated with the variability of the tapping force such that participants with smaller force variability have a better timing precision-but only in the absence of auditory feedback from the taps. We explain our observation by describing a potential mechanism based on empirical and theoretical results bridging the gap between timing variability and force variability. Our results suggest that tactile feedback in the presence of auditory feedback is mostly irrelevant in the perceptual determination of the occurrence time of the tap, and that the precision of a centrally organized rhythmic action depends on the reliability of sensory consequences generated by the action itself. PUBLIC SIGNIFICANCE STATEMENT: Motor variability, that is the natural variation of a repeated action, is a fundamental part of many brain functions. Among these, time processing is being recognized as critical for a wide range of behaviors. In particular, the cognitive processes underlying sensorimotor synchronization remain among the least understood. In this work we show that participants with smaller motor variability also have a better timing precision, but the correlation disappears in the presence of auditory feedback.