Comments on "Rapid motor adaptations to subliminal frequency shifts during syncopated rhythmic sensorimotor synchronization" by Michael H. Thaut and Gary P. Kenyon (Human Movement Science 22 [2003] 321-338)

Thaut and Kenyon [Human Movement Sci. 22 (2003) 321] have shown that, in a task requiring tapping in antiphase with a metronome, the response period adapts rapidly to a small (+/-2%) change in the stimulus period, whereas the relative phase between stimulus and response returns to its pre-change value only very gradually. On the basis of these and earlier findings, Thaut and Kenyon argue that period adaptation is rapid and subconscious, whereas phase adaptation is slow and dependent on awareness of a phase error. This interpretation is at variance with results in the literature suggesting that phase correction is rapid and subconscious, whereas period correction is slow and dependent on awareness of a period mismatch. Although differences in terminology (adaptation versus correction) play a role in this conflict, it primarily reflects different conceptions of sensorimotor synchronization and different interpretations of empirical findings. By excluding from their model a central timekeeper or oscillator with a flexible period, Thaut and Kenyon have omitted an essential component of human timing control that is needed for a proper explanation of their results.