Fluctuations of Human Tapping Intervals

Spectral analysis of fluctuations in tapping intervals has been performed when a subject listened to and did not listen to a metronome ticking. The power spectral density for metronome tapping is white above 0.1 Hz, and still white or decreasing toward the lower frequency; this means that memory of interval fluctuations within the subject is cleared by referring to metronome ticking. On the other hand, the spectrum for free tapping is white above 0.1 Hz, below which it increases so that the spectral density is inversely proportional to frequency (the 1/f spectrum). Furthermore, the white spectral level in free tapping is lower than that for metronome tapping. Subjects with Zen training showed a 1/f2 spectrum.