Picture this: it's Sunday afternoon, the Cluedo game has been tidied away, the fire is lit, it's the perfect time to watch a family film, snuggled on the sofa.
It was a common enough scenario until recently, but it's rapidly becoming as quaint as a museum tableau, replaced by an altogether less cosy modern reality: children in separate corners or rooms, their headphones plugged into iPads, one chortling away at a YouTube video you don't understand, the other glued to a tutorial about gaming or fashion. Meanwhile, the TV sits in the corner, standby light gleaming plaintively.
According to an annual survey by the research agency Childwise, children aged five to 16 now spend more time online each day than they do watching conventional television: three hours online, compared with 2.1 hours watching TV programmes.
Among teenagers, the switch is even more pronounced: fewer than a quarter of 15- to 16-year-olds watch television as it is broadcast, rather than on-demand or via YouTube.
A third of them have no favourite TV programme, yet can spend up to five hours a day online. YouTube's funny videos and "how to" tutorials make it the most popular destination, now used by half of all five- to 16-year-olds on a daily basis.
So just how much of a problem is this? Parents would once have welcomed the news that their children were watching less TV. Who can't remember being told to "turn off the TV and do something more interesting"? Mightn't it be better, in fact, for children to seek out the kind of thing that genuinely interests them, whether it's a TV programme on-demand or a tutorial on how to make a model spaceship, than passively watching whatever is served up by the TV schedule?
The problem is that with the proliferation of screens (67 per cent of British children now own a tablet such as an iPad), viewing is becoming a solitary experience. When I was younger, we would pore over the TV schedules and pounce on a family-friendly programme: The A-Team, The Dukes of Hazzard, Bond movies.
Even if the plots were lame and the sets wooden, we hardly noticed; it was as much about being together as being entertained. As a family, we'd chat about it, laugh about it - bond over it. All the children in my class would watch the same TV shows: Blue Peter and The Magic Roundabout when we were small; Rent-a-Ghost and Grange Hill when we were older.
But now the bonds of such shared experiences are being loosened by the rise of screen-time. Not only are children spending less time playing with each other outside, but when they are at home they are isolated, as each retreats to their own screen, their own world. It might reduce the sibling fights over the remote control, but it's yet another sign of the atomisation of our lives: each to their own, but also on their own.
When my children flop down on the sofa, they are more likely to get out their iPhones and plug into the tablet than to watch CBBC or CITV. And I now find myself in the ludicrous position of virtually begging them to watch TV, so we can sit together, and laugh along to it.
Yet it appears almost impossible for them to agree on something that is acceptable to both of them, and to me, other than The Simpsons. Now they are 12 and 10, it should be easier to find things we will all enjoy. But despite the plethora of channels, it's not.
The greater the choice, the pickier they are, anxious not to squander a precious minute of their limited screen time on something that does not perfectly fit their requirements. They will scroll through Netflix and Amazon's movie menus and still be unable to compromise - my son is a sci-fi and action movie aficionado, my daughter likes classics and rom-coms.
More often than not they will retreat with their iPads to their niche YouTube worlds - tutorials on how to make movie props in my son's case, and make-up videos in my daughter's. The whole jeopardy of watching things you didn't know you were interested in, discovering worlds you didn't know existed, disappears if you are on a loop of watching things you know you like.
Once I had persuaded everyone to watch Walking the Himalayas, they loved it. Dickensian, despite its dark themes, appeals to my daughter. Any programme about dogs is a winner. But beyond those, there is little they will join us to watch.
So what to do? It's easier to surrender, of course, and let them watch their tablets. But it's harder to keep track of what they are watching and for how long. There is also the risk of developing "iPad neck" - by looking down at their tablets, they create a strain on their necks equivalent to 60lb of weight.
But more worrying is that by opting for the internet and its infinite choice, children will zone in ever more closely on their niche tastes, rather than discovering new subjects that could broaden their horizons.
Online viewing is, in other words, creating a generation of anoraks.