Does spending too much time on smartphones and tablets damage kids’ development?

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Jessica’s tiny fingers dart around the iPad, swiping through photos to get to a particularly entertaining video: a 12-second clip of her dancing clumsily to Beyoncé’s “Single Ladies”. The 18-month-old taps “play” and emits a squeal of delight. After watching the video twice, she navigates back to the home screen and opens up the YouTube app to watch an episode of the colourful animation Billy Bam Bam. Halfway through, she moves onto a Yo Gabba Gabba!game, which involves anthropomorphised fruits making their way into a character’s belly.

When Jessica’s mum, Sandy, tries to take away the iPad, there’s a tantrum that threatens to go nuclear: wobbly lip, tears, hands balled into fists and a high-pitched wail. “She does this a lot,” says Sandy. “She seems to prefer the iPad to everything else. Sometimes it’s the only thing that will keep her quiet,” she adds, frantically waving a pink fluffy unicorn in an attempt to appease her daughter.

Like many parents, she’s worried about her child’s obsession with screens. And the concern among some experts is that these devices, if used in particular ways, could be changing children’s brains for the worse – potentially affecting their attention, motor control, language skills and eyesight, especially in under-fives, for whom so much brain development is taking place. Technology companies and app developers are throwing their marketing prowess at the problem, slapping words like “educational” and “e-learning” on their products, often without any scientific basis. So what are parents to do?

Few technologies have invaded our lives – and those of our children – as stealthily as the mobile computer, most commonly the smartphone or tablet. These devices are the right size for little hands to handle them, and the touchscreen’s easy for tiny fingers to manipulate. Plus there’s so much you can do on these devices: watch videos, play games, draw pictures and talk to relatives thousands of miles away.

In 2011, a year after the iPad launched, just 10 per cent of US children under the age of two were found to have used tablets or smartphones, but by 2013 that figure had nearly quadrupled. A 2015 study in France found that 58 per cent of under-twos had used a tablet or mobile phone. And yet there’s little clarity around the consequences of long-term use of such devices. So why don’t we know more about the risks of children using screens? Because there’s a fundamental problem at the basis of all the research in this area: what do we even mean by “screen time”?

First, it’s important to distinguish between types of screen: do we mean a television screen, a tablet, a smartphone or an e-reader? Second, the nature of the content matters: is it an interactive drawing game, an e-book, a Skype call with Grandma or a stream of Netflix Kids videos? Thirdly, there’s the context: is there a caregiver in the room talking to the child as they interact with the screen or are they left on their own?

To date, we have comprehensive research about children and television exposure, if not about interactive screens. However, there are a few things we do know. Most child development experts agree that while passive screen time – such as putting your child in front of a device for a Peppa Pig marathon – might be entertaining, it isn’t going to provide a rich learning experience. They also can show that having a video or TV on when a child is doing something else can distract them from play and learning, negatively affecting their development.

Hours of background TV has also been found to reduce child–parent interaction, which has an adverse impact on language development. And this displacement is a big concern: if kids are left with screen-based babysitters, then they are not interacting with caregivers and the physical world. There are only so many hours in a day, and the time spent with screens comes at the expense of other, potentially better, activities. Under-threes, in particular, need a balance of activities, including instructed play, exploring the natural environment, manipulating physical toys and socialising with other children and grown-ups. The rise in screen use means less of all these things.

The problem is that tablets are extremely appealing to children and adults alike. Thanks to their design, versatility and intuitive interfaces, tablets are a perfect way for children to draw, solve puzzles and be entertained on the move. Combine that with marketing efforts of digital media companies and app developers – whose measure of success tends to be the amount of time people are glued to their creation – and you have a toy that’s difficult to prise out of tiny hands.

What’s more, many apps are designed to be stimulus-driven, with exciting audiovisual rewards for completing tasks. Experts call this the “I did it!” response, which triggers the reward pathway in the brain. Because of this, tablets and smartphones make for excellent pacifiers, particularly on long plane journeys and in restaurants. But while this can be helpful in the short term, it’s important for young children to be able to develop internal mechanisms of self-regulation, whether that’s learning without constant rewards or being able to sit patiently without constant digital stimulation.

And there’s another hitch, says Dimitri Christakis, a director at Seattle Children’s Research Institute. Anecdotally, he and others are starting to see younger and younger patients using these devices compulsively. “We know there’s such a thing as problematic internet use in older children and adolescents. It stands to reason that the same would happen with infants,” he says. And he’s doing research to find out more.

In Seattle’s Center for Integrative Brain Research, a cluster of tiny pink mouse pups wriggle in a mass behind their mother. The rodent family home is a sawdust-filled clear plastic container, one of hundreds stacked up in a rotating system of shelves. These are the “control” mice used by Christakis and neuroscientist Nino Ramirez, and their team, trying to understand the impact on young brains of being exposed to fast-paced media.

Across the corridor an experiment is underway. One of the mouse containers is surrounded by bright lights and speakers. For 42 days, six hours every day, baby mice are exposed to the high-octane soundtracks of Cartoon Network shows accompanied by synchronised flashing lights in red, blue and green. The apparatus has been designed to find out what happens to the rodents’ brains when they are overstimulated by media during a critical window for their development.

The results are startling. “Overstimulating them as babies primes [them] to become hyperactive for the rest of their life,” says Ramirez. The overstimulated mice take more risks and find it harder to learn and stay attentive. They get confused by objects they’ve seen before, for example, and find it more difficult to navigate through a maze. When given the option to dose themselves with cocaine, the overstimulated mice were much more prone to addiction than the control group. These behavioural changes are matched by changes in the mice’s brains.

The theory is that the same applies to children: overstimulating them with media – particularly in an age of tablets with endlessly streaming, hard-to-ration videos and flashy interactive games – may cause an imbalance in part of the cerebral cortex called the basal ganglia. It’s this part of the brain that allows us to pay attention to critical tasks and ignore distractions. Such overstimulation could lead to problems in later life, particularly with focus, memory and impulsivity.

But before we trigger mass panic about a generation of hyperactive, inattentive, cocaine-using post-millennials, it’s important to note that these experiments have attracted criticism for a number of reasons. Six hours of any activity per day is a huge amount of time, particularly when it involves nocturnal mammals

like mice (although the researchers say the mice show no signs of stress). Furthermore, Christakis, Ramirez and colleagues don’t actually show the mice a real screen with any meaningful content – it is just a flashing proxy for a screen.

Still, it is possible to observe what happens with children “in the wild”  – and from this, we can draw possible links to their habits with mobile devices. In California, for example, Maria Liu from UC Berkeley’s School of Optometry, has seen a sharp increase in young children with myopia (short-sightedness). “It’s increasing at an alarming rate worldwide and a well-accepted contributing factor is the early introduction of handheld devices to kids.”

Another problematic aspect of screens is that they have been shown to disrupt sleep. The blue light emitted by the super-sharp displays can interfere with our natural bodily rhythms, preventing melatonin, an important sleep hormone, from being released. This in turn can lead to sleep impairments in adults and children alike. Sandy says that if Jessica uses the tablet before bed she gets “noticeably riled up”. So, she says, they try to use books instead. This issue is why the latest version of Apple’s software for iPads and iPhones comes with “Night Shift”, which automatically swaps the blueish light for a warmer hue before bedtime.

In London. Max, who is 12 months old, might as well be on the night shift. Sitting on his mother Helen’s lap in a small, darkened room, on his head is a rubbery cap covered in electrodes. Scientists are measuring the electrical activity in his brain as he looks at physical objects and at digital representations of those objects on an iPad screen. On each of Max’s ankles is a smartwatch of sorts, one measuring his movements and the other his heart rate. The cap uses electroencephalography (EEG) to record his brain’s electrical activity, to understand whether real and virtual objects trigger different brain responses and how that relates to subsequent learning.

The experiment is part of the TABLET project in the Babylab at Birkbeck, University of London. It’s the first ever scientific study investigating how children aged six months to three years are using touchscreen devices and how this influences their cognitive, brain and social development.

In a second experiment, Max sits in a curtained-off booth facing a screen that displays a 15-minute loop of video that includes trippy abstract animations and sounds, as well as still pictures and videos starring PhD students as stand-in children’s TV presenters. He’s completely mesmerised, and his eyes dart from object to object on the screen. Eye-tracking cameras capture the dance of his gaze, and outside the booth research fellow Celeste Chung keeps track of how his eye movements match up with the items on screen.

“All the child is doing is looking at the screen, but their gaze behaviour tells us about their learning and anticipations,” says Tim Smith, a cognitive scientist who heads up the Babylab. The team is trying to understand how easily Max, and dozens of other babies like him, can focus attention and block out distractions when working on a particular task. In one of the tests, an object appears at the centre of the screen and then a second object appears, near the edge of the screen, shortly after. In order to look at the second object, the child needs to disengage from the central one, which requires self-control. This is a very important measure of executive function, the brain’s “air traffic control system”, which helps a child analyse tasks, break them into steps and focus on them until they are done – a key predictor of success in later life.

Like Christakis, Smith is interested in finding out whether there really is a link between the reward learning found in many apps and a child’s ability to focus. “We might find that if tablets are being used for a lot of reward learning and the child becomes driven by an external stimulus then they might develop an impairment in executive function because they aren’t used to controlling their own attention,” he says.

Smith isn’t entirely convinced by the mouse model used by Christakis and Ramirez in Seattle. But on the effects on language and motor development, he hypothesises that there could be displacement going on. Devices such as iPads may give lots of stimulation, he says, but they lack the nuanced real-time social feedback that helps develop language. Similarly, tablets and phones may make children dexterous at fine motor control with all the tapping and swiping, but they may have less motivation to get up and explore the world around them.