My iPhone broke, so I went to the Genius Bar at the Apple store. (Too much brand terminology; my apologies.) They're not shy, Apple, are they? They could have called it the Helpdesk, or the Technicians' Bureau of Geek Know-How, but no, Genius Bar it is. As far as I know (and when it comes to phone technology it's a limited distance), the Genius Bar staff might be extraordinary individuals whose brains dwell in higher places. But they looked pretty normal to me - young, male, good with computers. Extreme helpfulness was probably their most exceptional characteristic. I'll spit it out. I'm just not 100 per cent convinced that everyone working at the Genius Bar was, in fact, a genius.

But how can you tell? No one seems quite sure what constitutes a genius. We have clear examples in history - a triple-headed monster of Shakespeare, Bach and Einstein swoops into view - but their genius is manifest in different ways, through different skills. And it's not quite enough to say that it's someone who's really brilliant at something, or incredibly clever. There's something mystical and other-worldly about genius - you can't put your finger on it, but you know it's there.

Unless you use an IQ test, which nails the matter handily (reductive alarm bells should sound now). I found a website called becomeagenius.net
which performed the useful task of breaking down levels of IQ by worldly function. So an IQ of about 80 made you a "high-school pupil/minimum-wage worker", 160 promotes you to "Rhodes scholar/army general" and 170 equals genius. And there you have a highly simplified, unwittingly hilarious and slightly disturbing lesson in eugenics.

The good news is that if, say, you are squatting low in the ranks, becomeagenius.net is able to direct you in three easy steps to a PayPal page selling The Complete Guide to Genius + Bonuses™, which will, if you're anything like the character in the case study, transform you from being a "dumb-ass" with no job to "a distinguished academic at a world-class university". So, there you have it: genius = $67.