Abstract
Interpersonal synchrony is the movement that matches in time with others. In humans, it is known to occur automatically and unintentionally during social interaction. If this synchronous movement is socially adaptive behavior, it may be shared with other highly social non-human primate species. However, there are few studies examining whether behavior change occurs in the presence of other individual in non-human primate species. Here we examined two pairs of mother and her biological offspring chimpanzees. Touch screen monitor was used to produce rhythmic finger-tapping movement from each chimpanzee. Two experimental conditions were presented: auditory exchange (AE) condition and no-auditory exchange (NAE) condition. In AE condition, auditory information of the rhythmic movements was bidirectionally exchanged between two chimpanzees through a short beep sound corresponding to each tapping event. On the other hand, in NAE condition, bidirectional auditory exchange of the rhythmic movements was eliminated. We found that one pair of chimpanzees showed tapping speed change between the two conditions. During AE condition, absolute difference in mean tapping speeds between two chimpanzees was significantly decreased in comparison with NAE condition. This suggests that chimpanzees’ rhythmic movement can be interfered by bidirectional auditory exchange. Moreover, the movements of the paired chimpanzees temporally change to converge with each other.
