Parents of four-year-olds from a low-income neighbourhood of Philadelphia have said in a survey that most of their children own mobile media devices, and now researchers who made that discovery say more study is urgently needed to draft guidelines for families.

As recently as 2013, studies pointed to a "digital divide" in ownership of devices such as tablets and smartphones based on income. To see if this gap persists, researchers surveyed parents of 350 children aged six months to four years.

"Our study found almost universal exposure, early adoption, and use of mobile media devices among young children in an urban, low-income, minority community," lead author Dr. Hilda Kabali of Einstein Medical Center in Philadelphia and her co-authors report in Monday's issue of the journal Pediatrics.

Currently, the American Academy of Pediatrics, the journal's publisher, advises eliminating screen time for children younger than two, because of concerns for how the use of the devices may delay how children learn language.

At age two, most children were using mobile devices daily and spending comparable amounts of time on television and mobile devices, the researchers found.For example, daily screen time in minutes for two-year-olds in the study was 44 minutes, time watching videos or TV shows on a mobile device was 29 minutes, and time spent using apps was 20 minutes.

Educational and entertainment apps were popular, as were sites such as YouTube and Netflix.

Almost all the 350 families said they had televisions (97 per cent), and most had tablets (83 per cent) and smartphones (77 per cent). More than half had video consoles such as Xbox (56 per cent), computers (58 per cent) and internet access (59 per cent).

Overall, 97 per cent of the children, or 338 kids, had used a mobile device. The researchers gave falling costs, marketing strategies and subsidies by cellular service providers as possible contributing factors.

Other findings from the survey included:

About 44 per cent of children under age one used a mobile device on a daily basis to play games, watch videos or use apps. The percentage increased to 77 per cent in two-year-olds and plateaued after that.

One-quarter (28 per cent) of two-year-olds did not need any help navigating a mobile media device, and 61 per cent needed help sometimes.

Of parents surveyed who allowed their child to use a mobile device, 70 per cent reported letting their children play with mobile devices to do chores, to keep the child calm in public places (65 per cent) or run errands (58 percent), and 28 per cent used a mobile device to put their children to sleep.

Parents completed the survey in English or Spanish during a visit to a pediatric practice in the Pennsylvania city in October and November 2014.

Multi-tasking with several devices

Child ownership of a device and age at first use weren't associated with ethnicity or parent education.

The study's authors also found one in three children used several media devices at the same time.

The high level of media by young children and reduced degree of parental involvement both in this study and in Canadian research is concerning, said Matthew Johnson, director of education at MediaSmarts, a Canadian digital literacy group that works on education, public awareness, and research and policy. It is funded by public and private-sector sponsors, donors and partners, according to its website.

Co-viewing with kids encouraged

"It's worrying that mobile devices are encouraging children and parents to use media reflexively rather than mindfully. We need to promote the idea that using media is something you choose to do, rather than something that just happens in the background, from an early age," Johnson said in an email.

"As well, when possible, parents should try to turn media use into an interactive experience, co-viewing with their kids to help them learn to engage critically with the messages they receive and encouraging the use of media as a springboard to creative play."

There are questions, too, about whether trying to pay attention to more than one medium at a time has long-term consequences on young children's ability to focus on a single task, he said.

Johnson also said there's no evidence young children get any benefit from educational media, whether apps or programs.

Little is known about how children's independent activity on mobile devices affects their cognitive, social and emotional development, Kabali and her team said. They urge further research to evaluate the impact of mobile device use on child development and to determine ways to approach it constructively.

Among the limitations of their study is that parents may have given answers they thought were expected, known as social desirability bias, and they may not have recalled use of devices correctly. Also, the apps were classified based on descriptions from the app developer rather than an independent source.

There was no external funding for the U.S. study.