Rhythmic finger tapping to cosine-wave modulated metronome sequences: Evidence of subliminal entrainment

Rhythmic finger tapping was examined during synchronization to metronome sequences whose base intervals were slightly perturbed by a cosine-wave function with the period of four samples. Data were collected under perturbation levels of 1%, 3%, 5% and 7% in conjunction with base intervals of 400, 500, and 600 ms. Statistical analysis examined the relationship between the inter-response interval (IRI), inter-stimulus interval (ISI) and synchronization error (SE). It was observed that IRI and SE entrain to the periodicity of the ISI patterns even at perturbation levels close to and below the conscious auditory perception threshold. Furthermore, the similarity between the IRI and ISI increased in proportion to the perturbation level. It was also found that the relative perturbation level had more influence on the synchronization behavior than the absolute level. Finally, the observed rhythmic tracking data were modeled mathematically to examine the likelihood of three possible synchronization strategies. (C) 1998 Elsevier Science B.V. All rights reserved.