Spontaneous Synchronized Tapping to External Rhythms in Chimpanzees

Humans actively use behavioral synchrony such as dancing and singing when they intend to make affiliative relationships. Such advanced synchronous movement occurs even unconsciously when we hear rhythmically complex music. A foundation for this tendency may be an evolutionary adaptation for group living but evolutionary origins of human synchronous activity is unclear. Here I introduce our study showing that our closest living relatives, chimpanzees, spontaneously synchronize their movements with auditory rhythms: After a training to tap illuminated keys on an electric keyboard, one chimpanzee spontaneously aligned her tapping with the sound when she heard an isochronous distractor sound. Another chimpanzee also spontaneously coordinated his tapping timing to the auditory rhythm. These results suggest that sensitivity to, and tendency toward synchronous movement with an auditory rhythm already existed in the common ancestor of chimpanzees and humans, although humans may have expanded it to unique forms of auditory and visual communication during the course of human evolution.