Twenty-two-month-old George sits on a tiny blue chair, at a baby-sized desk, playing with a grown-up toy -- an iPad, sign of a powerful trend that has set alarm bells ringing among child development experts.

Leaning over the tablet, the little Parisian finger-stabs the duck icon on "Moo Box", an application with animal images that let out moos, oinks and barks.

For his mother Aurelie Mercier, 32, the beauty of iPad apps is they can expand her son's world, like a virtual piano that lets him play music in the absence of the real thing.

"It's a window onto tons of things that we don't have at home and that can be condensed into a very small object," she told AFP.

Fuelled by the likes of George, the number of baby and toddler apps is booming, according to Heather Leister who has reviewed child applications at US website theiphonemom.com since 2009.

But psychologists and parents are divided on putting smartphones and tablets into such young hands, a high-stakes issue considering how pivotal the first couple of years are to child development.

Experts at a panel discussion in New York last month entitled "Baby Brains and Video Games" urged parents to set limits on electronic device use -- while acknowledging the magnetic appeal of iPads in particular.

"You can't pull it from their hands," said panelist Warren Buckleitner, editor of the Children's Technology Review.

George, who spends a half hour per week with the iPad, first asked for it at 10 months by pointing and cooing in its direction.

Both graphic artists, his parents recently developed their first app, which generates firework-like images to save as screenshots.

Though geared toward adults, Mercier lets George play with it, talking softly as he sends yellow stars swirling around the screen.

-- Pervasive culture of video --

Now they have seen first-hand what toddlers like -- catchy colours, sound, large buttons, simplicity -- the pair plan to develop child-friendly apps.

"We'll use George as our beta-tester," Mercier said. "We're counting on him to give good advice!"

For Katie Linendoll, a CNN technology expert in New York, apps are "the ultimate babysitter". Her favourites for using with her toddler niece -- in moderation -- include "Crazy Piano!" and "Crayola Color Studio HD", a high-tech colouring book where animals move once colored.

"If you have an app that's simple to understand, a kid will run with that," Linendoll told AFP.

But some parents worry about computer culture interfering with the way their children play with conventional toys.

Sarah Rotman Epps, a Boston-based consumer technology analyst, said her two-year-old son "loves drawing on paper with crayons.

"But he gets very frustrated when the pictures don't move, and I think that is really coming from the pervasive culture of video and animation."

In a nutshell: a hit YouTube video dubbed "A Magazine is an iPad that Does Not Work" shows a one-year-old trying in vain to scroll tablet-style through a print publication on her lap.

This is what troubles Paris child psychiatrist Serge Tisseron who worries apps fail to teach children to properly apprehend three-dimensional space, a key developmental milestone.

"We know the toddler absolutely needs to engage all his senses," he said.

Tisseron is by no means anti-technology -- the 64-year-old is himself an avid video gamer -- but until more research has been carried out he recommends keeping screens out of baby hands.

In the first two years of life the brain triples in size, synapses forming as young children experiment with objects they sniff, bite and throw.

Despite the iPhone and iPad's much-lauded interactivity, Tisseron says they remain limited in terms of sensory experience: they can engage sight, hearing and touch -- to an extent -- but not taste or smell.

That's where the simplest of toys, and baby games with no set rules, are crucial, says Texas paediatrician Ari Brown, lead author of a 2011 American Academy of Pediatrics report on screen use by children under two.

"There are some pretty good apps and activities that encourage problem solving, memory, ordering, sequencing -- virtual versions of games we used to play as kids," Brown said.

-- 'You don't need technology to play' --

But "no app can replace the value in taking two blocks and figuring out how to stack them one on top of the other."

The AAP discourages passive television viewing in this age group, but the jury is still out on smartphone use, as the technology is so new that long-term research is not yet available. The app store opened in 2008 and the iPad came out in 2010.

Brown suggests the main danger is a kind of opportunity cost: when youngsters play with iPads, they are not engaged in what may be more beneficial.

That view is shared by Jean-Philippe Vieira, 46, a Paris-area cook who has neither a tablet nor mobile phone and limits his children's television time to 20 minutes on Friday.

He believes toddlers need space to invent their own games, the way he did growing up in Portugal: "There were moments when we had nothing to do, but that was great because when you do nothing, you come up with ways to occupy yourself."

"You don't need technology to play," Vieira told AFP in a park full of yelling children.

Vieira, whose sons are three, six and eight, cautions against ushering children into a virtual world and is troubled by the idea of parents using the iPad as babysitter.

"Those who want to continue the life they led while single without children, well it's true these games can be the answer," he said. "But is it the right answer?"

But for George's mother Mercier, who never leaves her son unattended with the tablet, there is no harm in moderate use spaced out by other kinds of play.

In their case, keeping tabs on device use meant moving all the screens in their home behind a closed door, an out-of-sight-out-of-mind tactic to keep George from craving technology.

"But seeing as we live in a society with screens everywhere, I don't think I should keep him from playing with it."