Correlating with the EEGs, Dr. Law and her colleagues found that with every hour increase in average screen time, the children had more difficulties with attention and struggled more with executive functioning. However, because screen time is just one aspect of an infant’s environment, it is likely that multiple factors come into play, such as the quality of time with parents, the researchers say. It’s also possible that more active infants unintentionally receive more screen time as their parents try to manage their daily routines.

“A higher theta/beta ratio indicates a less-alert state, and has been associated with inattention,”

The more time the children had spent with screens at 12 months of age, the stronger were their slower-frequency brain waves, known as theta waves, compared with high-frequency beta waves.

“The infant brain thrives on enriching interactions with the environment, and excessive infant screen time can reduce opportunities for real-world interactions that are important for brain development,”

But a new study suggests that too much screen time during infancy may lead to changes in brain activity, as well as problems with executive functioning — the ability to stay focused and control impulses, behaviors, and emotions — in elementary school.