When I was the last class of high school, 6 VWO, aged around 17-18, I had a ‘boyfriend’. He was a clever fellow, bit of a geek and nerd of course. Then one day at his house, having tea with his mum as you do when you’re 17, he told me about the IQ test he had done. He told me of a question about logic and I asked for an example. He presented one, made up on the spot. It went something like: “If A – C – F – Z – A – what’s next?” (It was in fact a little more complex than this but it’s Friday, sue me.) I remember telling him that you couldn’t be sure, could you? And then he looked at me like he was half expecting me to not get it and explained that, yes, based on the sequence the next one had to be C. And I explained to him that, no, that was not certain since I had no clear indication yet that the sequence had been completed at all. How was I to know that no other letters would come after A first before the whole sequence was done, or that the second A was not an indication for a retrograde (making it A – C – F – Z – A – Z – F – C – A – etc.), or that the whole thing would modulate to another letter next? There were a hundred ways to go from there – or at least 26, if holding on to letters. He wasn’t buying it but I never forgot the look on his mother’s face as we had the conversation.