Research shows that children don't need explicit teaching from adults to see an action as following a social norm; they only need to see that adults expect things to work a certain way.
"Social norms are crucial for understanding human social interactions, social arrangements, and human cooperation more generally. But we can only fully grasp the existence of social norms in humans if we look into the cradle," Marco Schmidt from the Max Planck Institute for Evolutionary Anthropology said.
Researchers aim to get a better understanding of social norms by reviewing research on children's enforcement of this 'social glue'.
Schmidt and Tomasello, along with Hannes Rakoczy of the University of Gottingen, have conducted several studies with the aim of examining how children use constitutive norms.
They aimed to identify the point at which they stop thinking of game rules as dictates handed down by powerful authorities and begin thinking of them as something like a mutual social agreement.
In one study, 2- and 3-year-old children watched a puppet, who announced that she would now 'dax.' The puppet proceeded to perform an action that was different from what the children had seen an adult refer to as 'daxing' earlier.
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Many of the children objected to this rule violation and the 3-year-olds specifically made norm-based objections, such as "It doesn't work like that. You have to do it like this."
Another study found that children only enforce game norms on members of their own cultural in-group - for example, people who speak the same language.
Together, these studies suggest that children not only understand social norms at an early age, they're able to apply the norms in appropriate contexts and to the appropriate social group.
"Every parent recognizes this kind of behaviour - young children insisting that people follow the rules - but what is surprising is how sophisticated children are in calibrating their behaviour to fit the circumstances," Tomasello said.
The study has been published in 'Psychological Science'.