In a study of 370 parents released on April 25, 2015, more than one-third reported that their child was less than 12 months old when he or she began scrolling or manipulating a touch screen. In addition, over half said that their infants began watching “television” shows on a mobile device before turning 1.

By the age of four, every single child had used a touch screen, talked on the phone, watched video content, played games, and used apps. The majority of young children are using mobile devices for at least an hour per day by the time that they are two years old.

The author of the study, Dr. Hilda Kabali, a pediatric resident at the Einstein Medical Center in Philadelphia, told HealthDay that the consquences of this are still unknown.

“Although mobile devices are ubiquitous in young children’s lives, we don’t yet know the impact mobile devices can have on young children,” Kabali said. “What is realistic is for parents to guide their children’s media experience.”

There are a number of factors that contribute to these findings. Children model the behavior around them, and most adults are technology addicts. Mobile devices, with their bright lights, movement, and attractive icons, are inherently appealing to children. And parents are typically overwhelmed with the day-to-day challenges of home and work, making it far too tempting to use mobile devices as already-paid-for babysitters.

It will take years to determine the consequences of such early exposure to technology. Long before a scientific consensus emerges, a gut reaction may suffice: postpone for as long as possible each step in a child’s access to technology.