They know when you are sleeping…and will proceed to scream and holler at precisely that moment to ensure there will be no more of that under their watch. They know when you’re awake…and will demand your full, undivided attention. (Either that, or they’ll cunningly utilize that time to sleep.) As it turns out, babies are also quite adept at knowing who’s being naughty or nice.

A study by researchers at Yale University’s Infant Cognition Center, published in November of 2007 in the journal Nature, revealed that babies are able to distinguish helpful versus hostile intentions much younger than was previously suspected.

To test this ability, researchers put on a puppet show for a group of infants, and presented the babies with two virtually identical goggle-eyed toys. One toy was depicted helping another over a mountain, while the other more naughty toy pushed the other one backwards over it. Researchers then gave the group of 6- to 10-month-olds a choice of which toy they wanted to play with. The babies weren’t fooled: nearly all of the tots chose the ‘nice’ toy over the naughty one.

This experiment illustrates that babies aren’t as naive as adults often presume they are. It also has big implications for home environments and how we all interact with them. Infants and small children can tell when there is conflict in the home, and they can also tell when a caretaker doesn’t have their best interests in mind. They can read an adult’s emotions, and also observe others and determine helpful versus hurtful actions. And all of this appears to be an innate ability that they possess virtually from the start.

So in contradiction to the song we all know so well, it’s really the grown-ups who are being watched and judged on whether they are naughty or nice.