What new parent has stared at their speechless child in utter befuddlement? But now we have a peek into what’s going on inside that freshly baked mind: Practice. Enough practice that babies often amaze us by seeming to pick up new skills overnight. But babies’ brains are actually prepping for complicated tasks long before their first steps or words, according to new research.

Penn State researchers compared how we observe infants develop new skills with the unseen changes in electrical activity in their brains, or electroencephalography (EEG) power. They found that most babies appear to learn new skills in irregular bursts, while their EEG power grows steadily behind the scenes.

How babies learn skills “is a question that has bedeviled psychologists for most of the last century,” said Koraly Perez-Edgar, a psychology professor at Penn State and an author of the study published in the journal Child Development. “Psychologists have been suggesting that while on the surface development looks like these quick bursts, underneath there may be very continuous, slowly developing mechanisms that one day look like they popped out of nowhere.”

Perez Edgar pointed to skills like talking and walking, which suddenly (to a parents’ perspective) appear to just happen out of nowhere one day.

This view of development — that babies’ internal experiences don’t necessarily match up to what appears to us — has been a theory for some time, but the Penn State researchers’ use of new modeling methods has finally enabled scientists to find evidence of it.

A total of 28 six-month-old infants were recruited and brought to the lab once a month until they turned one year old. During each visit, the baby participated in a cognitive test called the “a-not-b task,” designed in the 1950s to measure an infant’s understanding of object permanence: knowing something exists even if it’s out of sight.

In the task, a researcher put a cardboard box with two wells — A and B — across from the infant. The researcher then hid a toy in one well and covered it with cloth, hiding it from view. The infant was considered successful if they correctly retrieved the toy twice from well A and then once from well B after the researcher hid it.

“How babies perform in this task tells us a lot about their development because it’s a coordination of multiple skills,” explained Leigha MacNeill, a Penn State graduate student and study researcher. “They have to remember where the ball was moved, which is working memory. They have to know an object exists even though it’s out of sight, and they need to track objects moving in space from one place to another. All of this also required them to pay attention. So there’s a lot going on.”

The researchers also measured the infants’ EEG in different brain regions at each visit. After analyzing the data, the researchers found that performance on the a-not-b task spiked between seven and eleven months — a period when they also found EEG power grew at a steady pace.

“Infant behavior varies so much from baby to baby, so it’s helpful to understand what’s going on beneath the surface,” MacNeill said. “This multi-method approach is helpful, because we can see both the infants’ behavior and also what’s going on in the brain. It gives us a better sense of where this variability comes from, and can help us see what’s happening in the brain when the infant isn’t getting better at the task verses when there’s rapid development.”