Have you read “The Curious Incident of the Dog in the Night Time” by Mark Haddon? There’s a strong chance that you have. It’s one of those books that you are likely to have read even if you only read occasionally. If you’re over 40 it’ll be up there with “Fever Pitch” (if you’re a guy), “Captain Corelli’s Mandolin”, “Life of Pi”, “Paddy Clark ha-ha-ha”, “Notes from a Small Island”, maybe “Small Island” too. (If you haven’t read the last one, and you’re only going to read one book this year, give it a go. You won’t regret it.)

Assuming that you have read Mark Haddon’s book, can you remember either Christopher’s favourite joke or his favourite book? (Christopher is the main character; for some reason his name has stuck in my mind; usually the character names don’t, unless they’re in the title.)

This came up in conversation with my brother in 2011. I had only just read the book, long after most people. If I had read it around 2004 when most people were reading it, and before my children were born, it would have been a very different experience. One of my Compartments (and I haven’t written much about it yet) is that I have a child with a diagnosis of autism. It affects our everyday life. Every reference to the condition, every inappropriate use of the word “autistic”, now resonates very differently from how it used to. I haven’t seen “Rain Man” since my children were born, but, you know, I’m a very good driver.

So, my brother asked me “Can you remember what the boy’s favourite joke was in the book?” I thought about it, remembered that there was a joke, couldn’t remember what it was, said “Nope”. And he said, “You see, NOBODY remembers the joke. I’ve asked lots of people and nobody remembers.” So I asked, “Can you remember what his favourite book is?” He thought about it, and couldn’t remember. I thought he’d guess, or work it out, or bring it up from somewhere. No. Can you remember? Think about it. I told him straight away, I’ll reveal it at the end of this piece so that you have a bit longer to think about it.

The favourite joke involves an economist, a logician and a mathematician on a train crossing the border into into Scotland. You can read it here. The point of the joke: mathematicians are best.

And my point here is this: we remember different things. Two people can read the same book or watch the same movie and remember different things about it. Don’t give other people a hard time if they can’t remember the same things as you. And don’t give yourself a hard time if you remember different things from other people, or if you remember nothing at all.

So what was his favourite book? “The Hound of the Baskervilles”, a detective story, with a dog in the title. Nobody I’ve asked remembers this either although it occupies an entire 6-page chapter in the paperback copy that I’m looking at right now (chapter 107, starting on page 88). The joke takes up less than half of page 177, in chapter 181.