Touch-screen devices have taken off since the release of the first iPad. It's unlikely that tablet makers had toddlers in mind when they developed the gadgets, but young children have gravitated to the new technology. A 2011 survey by US non-profit advocacy group Common Sense Media found that 39 per cent of children aged two to four years and 52 per cent of those aged five to eight have used a touch screen for videos, games or other apps. And software developers have taken note, along with producers of educational content.

The driving force for such early use of touch-screen technology is twofold. It used to be that children had to learn how to type on a keyboard, figure out how to use a mouse or a joystick and then have mum or dad negotiate the operating system to utilise educational software. Applications on tablets, on the other hand, open directly into play mode.

Moreover, interactive apps provide immediate feedback, unlike television, which is a passive experience for children.

According to Daniel Anderson, a psychology professor at the University of Massachusetts, children actually look away from television screens more than 150 times an hour because they have trouble knowing where on the screen to focus. A well-designed app is more engaging, however, because the child can control the action when he or she touches the screen.

That is clearly the case in the Chau family. Hong Kong clergyman Sherman Chau and his wife Becky Faubion are finding that none of their three children, Hannah, Allison and Zachery, watch any television.

Their eldest child, nine-year-old Hannah, appreciates having control when she uses their iPad. "On television, you have to watch whatever they are showing. But I can watch whatever I want on the iPad, whenever I want," she says.

An educator-turned-full-time-homemaker, Faubion typically favours pretend and exploratory play for her children rather than touch-screen devices. But, like many conflicted parents, she turns to them as a last resort when trying to keep two-year old Zachery engaged on trains and at restaurants. Her daughters, Hannah and Allison, six, use it to entertain themselves on Saturday mornings, before the rest of the family gets out of bed, and when mum wants them to keep quiet while their brother naps. Her biggest concern is that "they're only three clicks away from pornography, which is quite scary". But she concedes it gives her a much-needed break when she needs to focus her attention elsewhere.

The ability for such devices to hold children's attention means many parents turn to them as "portable babysitters". But experts are divided on how toddlers should be using these gadgets.

When young children are engaged in a touch-screen environment - drawing, colouring or moving pieces around - they enter what psychologists call the "flow experience". They are so absorbed in the activity that it becomes difficult to pry the tablet away from the child. That attention is physiologically the same as if the child was immersed in building blocks or playing a sport.

A good app, driven by content and engagement, encourages brain activity, unlike "zoning out" in front of the television, says Lisa Guernsey, director of the Early Education Initiative at the New America Foundation.

But British neuroscientist Susan Greenfield says that electronic devices that keep youngsters absorbed for long periods can also lead to shortened attention spans and other negative traits.

In the right hands, however, the ability of such devices to hold our children's attention can be a benefit. Touch-screen devices with assistive functions such as word prediction, screen magnifiers, talking software and multiple points of activity can help such children with Attention Deficit Hyperactivity Disorder (ADHD) handle stressful situations.

Hannah and Allison Chau, who both have ADHD, easily lose themselves when playing on their tablets, becoming quiet and still, their mother says. Because these devices handle multitasking so well, children who usually have difficulty paying attention remain stimulated and continue to pay attention.

A study of young children with ADHD by Southeastern Oklahoma State University found that after a six-week trial using iPads, students made up to one year's progress in reading development. Teachers turned the hyper-focus effects of tablet computers into a strength that ADHD children could use for learning benefit, researchers noted in the report published in the May-June issue of last year.

As Guernsey sees it, parental interaction is key to the effective use of touch-screen technology among children.

Digital media cannot replace the attachment and security young children need from their parents but it can be used to introduce new words and ideas that can help them deal better with life in the real world.

Unfortunately, instead of figuring out how to effectively use new technology to benefit youngsters, many parents simply plonk the devices in front of their children to keep them out of their hair.

"It is the kids who already have difficulty paying attention that are put in front of the screen to chill out," writes Dr Michael Rich, director of the Centre on Media and Child Health at the Boston Children's Hospital.

The physical impact of excessive screen time and whether any learning takes place are two major concerns that parents in Asia have about the use of touch-screen devices among very young children.

For Pemberton's wife, Maggie Chen, the biggest worry is whether too much time focused on a tablet screen might cause Perry to become shortsighted. Pemberton, however, would rather their little boy spend more time outdoors, running about or kicking a ball around.

American research psychologist and educator Dr Larry Rosen concurs. His findings at California State University show that insufficient time away from technology can affect young children's creativity and ability for free play.

There is little evidence connecting screen time with brain development but many child development experts reckon youngsters need time away from screens to sense the physical world and practise making connections that relate to motor skills and spatial relationships.

Rosen advises parents to adopt a ratio of five minutes of time away from technology for every minute spent with it. So if a young child plays on a tablet for 30 minutes, they should have 150 minutes engaged in other non-screen activities.

Even so, after seeing how educational apps helped Perry master the alphabets and identify shapes and objects around the house, Pemberton thinks that there is great potential in incorporating the material into children's learning.

American education specialist Jennifer Stroud, too, found that using tablet applications to replace some other activity like watching television, which her daughter Lillian was already doing, was more effective than having her learn from flash cards or workbooks.

Yet, the notion that young children's learning experiences can start with screens doesn't square well with Guernsey, author of . In her research, children below the age of two require social interaction as a foundation for learning. At that age, attachment and security are paramount. Only from 19 months onwards do pictures start to make sense to children as symbols.

The jury is still out on what the right thing is to do. Scientific studies on how technology affects development of young children take between three to five years to complete. So, in the meantime, the real experiment is unfolding in our homes.

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