Primates Spontaneously Adjust Their Movements With Their Partners To Reach Synchrony
January 28, 2013

Monkeys Spontaneously Adjust Their Movements With Their Partners To Reach Synchrony

Lawrence LeBlond for - Your Universe Online

Previous research that has shown how humans synchronize their body movements without any conscious effort has been carried over to studies into primate behavior.

Much in the same manner that humans will fine-tune their gait to be in sync with those walking around them, or will slow or speed up their claps to be in unison with an applauding audience, researchers from the RIKEN Brain Science Institute in Japan have found that pairs of macaque monkeys will spontaneously adjust their movements to reach synchrony.

This is the first time researchers have identified such behavior in primates. The phenomenon of subconsciously adjusting movements is believed to reflect bonding and help facilitate interaction.

This new research may open the door to further neurophysiological studies of spontaneous synchronization in monkeys, which could shed light into human behavioral dysfunctions such as autism spectrum disorder, echopraxia and echolalia–where patients uncontrollably imitate others.

Lead researcher, Naotaka Fujii, along with colleagues from RIKEN, developed an experimental set-up to test whether pairs of macaque monkeys synchronize a simple push-button movement.

The researchers first trained the monkeys to push a button with one hand before conducting the experiments. Once monkeys learned to push the button, the first phase of the study began. In this experiment, the monkeys were paired and placed facing each other while team members recorded the timing of the push-button movements.

In the second phase of the study, the monkeys were placed in front of a video screen of other monkeys pushing the button at various speeds. In the final experiment the macaques were not allowed to either see or hear their video-partner.

The results showed that the monkeys modified their movements–either increased or decreased the speed of their push-button movements–to be in-sync with their partner, both when the partner was real and on video.

The speed of the button pressing movement changed to be in harmonic or sub-harmonic synchrony with their partners´ speed. However, different pairs of monkeys synchronized differently and reached different speeds, and the monkeys synced their movements most when they could see and hear their partner.

The researchers said this behavior could not have been learned during the experiment, as it has been proven extremely difficult for monkeys to learn intentional synchronization.

"The reasons why the monkeys showed behavioral synchronization are not clear,” noted the researchers. “It may be a vital aspect of other socially adaptive behavior, important for survival in the wild.”

The study was published today in the journal Scientific Reports.