I was out for a walk on Primrose Hill the other day, when I was stopped dead in my tracks by the sight of a toddler, head bowed, fingers expertly skimming the screen of an iPad that had been attached to the front of his pushchair. (Yes, there is such a thing as an iPad mount for pushchairs.) Neither the hooligan squirrels nor rampaging dogs could compete with the screen for his attention. I noted that the woman pushing was lost in her own world, listening to music.

Not for the first time I was left feeling slightly bewildered as I absorbed this latest digital incursion into everyday life. This was rapidly followed by a sense of relief that iPads weren't around when my own children were little. Because one of the most exhausting aspects of contemporary parenting has to be the relentless effort to monitor screen time and at least try to be seen to be keeping a weather eye on what children are doing online. Interesting to note that Apple founder Steve Jobs banned his own children from using an iPad.

I wasn't sure whether to be dispirited or heartened by recent research showing that the average six-year-old now understands more about technology than the average forty-five-year-old. I lost all technological credibility with my children years ago when I threatened to remove YouTube from the Internet after I caught them watching Charlie Bit My Finger on a loop. "How are you planning to do that, Mum?" asked my eldest son sarcastically. "With a hoover?"

Over the years I have tried to challenge my deep-held instinct that most screen time is bad. I recently berated my fourteen-year-old daughter for spending too much time on her phone only to discover that she was watching a really interesting, if disturbing, video on men catcalling a young woman as she walked through the streets of New York. A brief digital tour of my nephew's Minecraft account made me realise that online games can be creative and imaginative, the equivalent of digital bushcraft. Facebook helps my teenagers keep in touch with friends from primary school and Instagram has definitely encouraged my daughter's love of photography.

Yet certain inescapable facts that I have discovered while researching my new novel have convinced me that the ongoing debate with my children over screen time and online content is an argument worth having.
I note how digital gaming companies talk openly about creating games with a 'compulsion loop', which is morally questionable shorthand for making them as addictive as possible. The idea is that a player plays a game, achieves a goal, and is rewarded with new content that makes them want to continue playing with the new content and therefore re-run the loop. Hence the fact that allowing my youngest son 'just five more minutes' on Fifa never makes him happy when it's time to come off.

Neuroscientists have discovered that most of what we do online releases dopamine into the brain's pleasure centres. This is the same chemical reaction experienced while gambling or taking drugs. Self-disclosure is associated with increased activity in brain regions that form the mesolimbic dopamine system. So tweeting or updating your Facebook status is intrinsically rewarding. But also potentially addictive.

In an effort to challenge their belief in the infallibility of privacy settings on social media, I casually leave newspaper articles on the kitchen table. For example, the recent hacking of Snapchat, a hugely popular social media site, where all messages and images are meant to be destroyed within ten seconds. Or the iCloud hack that leaked intimate videos and photos of female celebrities, including Jennifer Lawrence, onto porn sites. If Jennifer Lawrence can end up at the wrong end of a sexting scandal, then anyone can.

Unlike human beings, the Internet remembers everything and forgets nothing. One moment of malice on social media really can end up defining the rest of your life.

Fiona's new book, The Good Girl is published by Penguin Books UK and is available from Amazon.