Something that's come up in conversation a couple of times recently is my habit of looking out of the window shortly after I get out of bed. I don't feel quite comfortable until I've had a look at the world outside; but I'm not entirely sure what I'm looking for. There doesn't seem to be any specific thing I want to know when I pull back the hallway curtain and peer out.

It's at that point that I get my first idea of what the weather's like (unless it was audibly raining even before that), but I don't generally need to know that for another half hour or so, and don't feel any particular curiosity about it. So I don't think that's it.

It also grounds me in reality; if I've been having a weird and realistic dream set in some other world then it reminds me which of Cambridge and the dream-world is … well, I hesitate to say real because I probably look out of the window in some of those dreams too, but it tells me which world is the one I currently have to deal with. But although weird and immersive dreams set in other worlds are not unheard of in my dream-life, they're not common either, and my need to look out of the window isn't conditional on just having had one. So that doesn't seem like it either.

It also has the effect, I suppose, of reassuring me that the world outside still looks as I expect it to, that there's been no large and sudden change while I was asleep. Perhaps this is a natural consequence of having a brain that needs to be powered down for eight hours on a regular basis: I want to have some confidence that it didn't stay powered down for longer than that by accident.

But then, I thought, hang on a minute. What sort of large and sudden change might I be expecting or fearing? What sort of large and sudden change even makes sense?

And at this point an altogether more plausible answer occurred to me. As befits someone like me, I was of course raised on Hitch-Hiker's Guide from a very early age. So it's entirely possible that the true reason I feel a need to look out of my front window shortly after getting up is a subconscious desire to reassure myself of the absence of big yellow bulldozers.

I think, perhaps worryingly, that that answer is a lot more likely than any of the previous ones, or even all of them put together.