If two men began a boisterous tug-of-war over the wine list at a posh restaurant, more than a few heads would turn. Yet two six-year-old kids quarreling over a pack of crayons at a diner would hardly seem unusual. It is normal for kindergartners to act out and for grown-ups to show restraint. But social pressure alone cannot explain why adults are so much better at thinking before they act and recognizing how others view them.

According to a new study, the development of social awareness and the introspection it requires may be linked to the development of the default network, a group of regions in the brain that are active when our mind is wandering instead of focused. The research, presented in November at the annual meeting of the Society for Neuroscience, suggests this network is not fully coordinated until around the age of 13.

Neuroscientist Stuart Washington of Georgetown University Medical Center asked 42 participants aged six to 27 to stay inside a functional MRI scanner and play a simple game, searching groups of arrows for one pointing in a different direction from the rest. But the researchers were not interested in brain activity during the active task—they wanted to observe the brain during periods of rest between tasks. In the past decade scientists have a discovered that a particular network of brain regions consistently stirs to life whenever people are at wakeful rest inside fMRI machines, not focusing on anything in particular. Studies have tied this default network to daydreaming [see “Living in a Dream World”], introspection, moral reasoning, thinking of the future and the ability to see the world through others’ eyes.

When Washington compared the activity of the default network in people of different ages, he found a clear pattern. The older the participant, the more synchronized the interaction of the default network’s five primary nodes, which are spread throughout the brain. Children aged six to nine showed hardly any synchronized communication in the default network. But by 13 years of age, the participants began to demonstrate neural coordination typical of an adult.

“Our results imply that children are less able than teens and adults to comprehend the consequences of their actions, think about future events or realistically gauge how other people view their actions,” Washington explains. “Since these behavioral attributes are not fully formed in children, they are more likely to make rash decisions that do not account for consequences or other people’s perceptions.” So the next time you are stuck in earshot of squabbling youngsters, try to pardon their lack of consideration. They probably have not yet been able to imagine themselves as others see them.