As you may have read, Professor Gary Small from the Semel Institute of Neuroscience and Human Behaviour put 24 old people in a Petri dish. Half of them were experienced computer users. Half of them were not. He found that when asked to perform simple internet searches, the techie old people had a higher level of brain activity than those who preferred a book and a nice cup of Horlicks. He and his team thus concluded that surfing the internet can sharpen the ageing brain.

This is an upsetting conclusion. I was looking forward to the time when life is simply a rocking chair, snooker on the telly, a postprandial snooze and sudoku. Now it appears we must cybersurf to keep the dribbling at bay. Well, I’m sorry, but I’m sticking with the “Google makes us stupid” lobby.

Since the internet arrived, powers of concentration have evaporated. A bibbling e-mail here, a need-a-bigger-penis spam there, a quick Facebook, an eBay flutter, a Viagra advert, check the headlines, check the e-mail again, log off, log on — it may be brain activity but it’s definitely not of the higher order. And it certainly isn’t going to offset dementia.

If you read too much, you become learned. If you spend too much time on the internet, you go blind. Or, if you aren’t addicted to porn, you become a troll. The phenomenon of trolling is perhaps the greatest indication that the internet is not a path to a lengthier, happier, sharper existence.

If you are a troll, you no longer get your kicks from straightforward surfing. Your main purpose in cyberlife is to spend your days lurking on online message boards, disrupting conversations with gratuitous abuse or spurious argument or conspiracy theory.

Trolling began as the ultimate geek joke in the 1990s. It was short for “trolling for newbies”. Trolls would post intentionally naive comments (“I think you’ll find glass does flow over time”, for example) and wait for people to correct them. The aim would be to create an endless online thread about the truth or otherwise of flowing glass when the original discussion was on, say, Iraq (it’s always on Iraq). The more people you frustrate with your random post, the better.

Now it has progressed into an entire online culture. All over the world, but mainly in America, trolls are delighting in the spread of mistruth, rumour and deviation.

Sometimes it’s funny — take Jason Fortuny, a passionate troller, who posted a hoax ad online posing as a woman seeking a “str8 brutal dom muscular male” in 2006. He got 100 eager responses and posted their personal details on his blog. Ensuing job losses and divorce aside, that’s funny. But sometimes it isn’t: in 2007 a 13-year-old girl hanged herself after receiving taunts from a boy she’d been flirting with on MySpace. The boy, it turned out, was in fact the mother of one of the 13-year-old’s friends. The trolling mother claimed she was trying to find out whether the girl was bullying her daughter.

Read any unmoderated debate online and it’s hard not to suspect the world is full of stupid people who are getting stupider. But that can’t be right — the internet makes you smarter. The prof says so.

My advice (not that you’ll have had the concentration to read this far): when the fog of old age begins to wrap itself soothingly around you, unplug the computer and throw the keyboard out of the window. You might lose your marbles quicker but it’s better that way. And you don’t need to be online to buy Viagra. You can get it from the chemist.