When people feel they are working with others as a team to reach a goal, they are more motivated to achieve the goal, even without any extrinsic reward, than if they are working alone. They work harder and longer at the task, become more absorbed and perform better.
But how do you make people feel connected? It might be easier than you think.
Gregory Walton from Stanford found that when college students believed they shared a birthday with another student, they were more motivated to complete a task with that student and performed better on the task. He found the same effect with four and five year olds.
In another study Walton had people who were part of the experiment jog in place, raising their heart rate. Participants in the study who felt they were socially connected to this person (for example,were told they had the same birthday) had an increased heart rate, too.