The influence of external and internal motor processes on human auditory rhythm perception

Musical rhythm is composed of organized temporal patterns, and the
processes underlying rhythm perception are found to engage both
auditory and motor systems. Despite behavioral and neuroscience
evidence converging to this audio-motor interaction, relatively
little is known about the effect of specific motor processes on
auditory rhythm perception. This doctoral thesis was devoted to
investigating the influence of both external and internal motor
processes on the way we perceive an auditory rhythm. The first half
of the thesis intended to establish whether overt body movement had
a facilitatory effect on our ability to perceive the auditory
rhythmic structure, and whether this effect was modulated by
musical training. To this end, musicians and non-musicians
performed a pulse-finding task either using natural body movement
or through listening only, and produced their identified pulse by
finger tapping. The results showed that overt movement benefited
rhythm (pulse) perception especially for non-musicians, confirming
the facilitatory role of external motor activities in hearing the
rhythm, as well as its interaction with musical training. The
second half of the thesis tested the idea that indirect, covert
motor input, such as that transformed from the visual stimuli,
could influence our perceived structure of an auditory rhythm.
Three experiments examined the subjectively perceived tempo of an
auditory sequence under different visual motion stimulations, while
the auditory and visual streams were presented independently of
each other. The results revealed that the perceived auditory tempo
was accordingly influenced by the concurrent visual motion
conditions, and the effect was related to the increment or
decrement of visual motion speed. This supported the hypothesis
that the internal motor information extracted from the visuomotor
stimulation could be incorporated into the percept of an auditory
rhythm. Taken together, the present thesis concludes that, rather
than as a mere reaction to the given auditory input, our motor
system plays an important role in contributing to the perceptual
process of the auditory rhythm. This can occur via both external
and internal motor activities, and may not only influence how we
hear a rhythm but also under some circumstances improve our ability
to hear the rhythm.