Monkeys Spontaneously Sync Up Movements
Two snow monkeys at Jigokudani near Nagano, Japan.
Credit: Neale Cousland | Shutterstock

Without even thinking, people often coordinate their movements with others around them, from clapping to walking to making facial expressions. New research shows monkeys might spontaneously sync up with their peers as well.

A group of Japanese scientists trained three macaques to press two buttons in front of them repeatedly and alternately with one hand. During the first set of trials, the monkeys were paired up and seated facing each other as the timing of their button-pushing was recorded. Then, instead a live partner, each monkey was seated across from a video screen that showed another monkey performing the button-pushing task, which allowed researchers to control the speed of the movements. In other experiments, the researchers cut either the audio or visual elements of the monkey's video-partner.

The macaques adjusted the speed of their button-pushing to synchronize with both real partners and video ones, the researchers found, and they were better at coordinating the movements when they could both see and hear their partner.

In a paper detailing the study Jan. 28 in the journal Nature Scientific Reports, the researchers wrote that it's unclear why the monkeys matched up their movements. For humans, previous studies have shown that a similar behavior — imitation — promotes affection and empathy for the imitator in the people who are being imitated, which helps to lubricate social situations and foster bonds.

The team speculated that synchronization for the monkeys could be tied to similar behaviors that are important for survival in the wild, such as such as facial imitation in newborn macaques and apes. Moreover, the results suggest that the monkeys' mechanisms for adapting to their social environment are quite flexible, since synchronization occurred for an unnatural and learned behavior unrelated to survival (in this case, pressing a button), the researchers said.

"Our future goal is to record neural activity in multiple brain areas in monkeys performing the task described in this study, in order to identify the dynamic functional connections that initiate and maintain synchronization," the team wrote.

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