A new study from the National Institutes of Health shows infants can actually learn, even while they're sleeping.
Researchers used a machine to record the brain's electrical activity in sleeping infants and a camera to record facial activity.
A tone was played and a puff of air was blown on their eyelids.
After repeating the exercise numerous times, the babies scrunched their faced in response to the tone with the air puff.
This type of learning involves a part the brain central to areas of developmental disorders.
Tests like this one may help diagnose babies at risk for certain disorders.