Children who play a game together have a stronger connection than kids who play the same game but not in a synchronous way, according to a new paper. 

The authors assert that a physical activity performed in unison helps children feel more positively toward each other and could perhaps increase their empathy. 

"Synchrony is like a glue that brings people together -- it's a magical connector for people," said lead author Tal-Chen Rabinowitch, a postdoctoral fellow at the Institute for Learning&Brain Sciences at the University of Washington.

Synchrony occurs when people interact together in time. It's a fundamental prerequisite for activities such as playing music, singing, dancing and rowing.  But the impact of synchrony goes beyond the ability to coordinate activities with other individuals, say psychologists In adults, synchrony has been linked to increased cooperation and teamwork, making work more efficient and productive. 

Few studies have examined whether the same is true among children because children don't fill out surveys as well as college undergraduates. 

"We wanted to see if a synchronous, rhythmic interaction could influence the attitudes of children toward peers they had never met before," said Rabinowitch, so she conducted the study at the Hebrew University of Jerusalem in Israel, where co-author Ariel Knafo is a professor of psychology. They tested 74 8-year-old children in pairs of two boys and two girls. Seated in a quiet laboratory room, the experimenter introduced herself and asked the children to introduce themselves to each other by name only.

After the experimenter explained the task, the children sat side by side in front of a video screen. An animated soccer ball bounced on both halves of the screen, and the children pressed a button whenever the ball on their side of the screen hit the floor.  For some pairs of children, the balls bounced in sync, so their fingers tapped the buttons simultaneously. Other pairs of children had out-of-sync bouncing, so they had asynchronous finger tapping. 

They did two 90-second trials of the game, with a short break in between. After the game, the children filled out questionnaires about how similar and close they felt to the child they had been paired with. A control group of pairs of children answered the same questions, but did not perform the game.  Children in the synchronous group reported a greater sense of similarity and closeness.

The findings suggest that time-based synchronized activities, including in music, dance and sports, could be useful tools in bringing children closer together.

"The important ingredient is joint synchronized activity -- it is a form of collaboration where individuals perform the same movements at the same time," Rabinowitch said.