Abstract
Humans tend to spontaneously align their movements in response to visual (e.g., swinging pendulum) and auditory rhythms (e.g., hearing music while walking). Particularly in the case of the response to auditory rhythms, neuroscientific research has indicated that motor resources are also recruited while perceiving an auditory rhythm (or regular pulse), suggesting a tight link between the auditory and motor systems in the human brain. However, the evolutionary origin of spontaneous responses to auditory rhythms is unclear. Here, we report that chimpanzees and humans show a similar distractor effect in perceiving isochronous rhythms during rhythmic movement. We used isochronous auditory rhythms as distractor stimuli during self-paced alternate tapping of two keys of an electronic keyboard by humans and chimpanzees. When the tempo was similar to their spontaneous motor tempo, tapping onset was influenced by intermittent entrainment to auditory rhythms. Although this effect itself is not an advanced rhythmic ability such as dancing or singing, our results suggest that, to some extent, the biological foundation for spontaneous responses to auditory rhythms was already deeply rooted in the common ancestor of chimpanzees and humans, 6 million years ago. This also suggests the possibility of a common attentional mechanism, as proposed by the dynamic attending theory, underlying the effect of perceiving external rhythms on motor movement.
Highlights
IntroductionIt was thought that the ability to synchronize movements to auditory beats was unique to humans [1, 2]
Until the past decade, it was thought that the ability to synchronize movements to auditory beats was unique to humans [1, 2]
The results indicate that chimpanzees and humans can show a similar distractor effect and this effect occurs only when the stimulus tempo is close to the spontaneous motor tempo of the participants (Fig 5)
Summary
It was thought that the ability to synchronize movements to auditory beats was unique to humans [1, 2]. We reported that a female chimpanzee named “Ai” spontaneously aligned tapping the keys of an electronic keyboard to an isochronous auditory sequence [7]. Her response was limited in that rhythmic entrainment appeared in only one of three tempi (i.e., ISI- 600 ms), notably, she showed rhythmic entrainment without any specific training.
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