I've been reading Tim Krabbé's book The Rider and one thing that really stood out is how much time he spends thinking about which gear he is in. For instance, during one of his long long climbs he recalls scouting the route and riding in the forty-three nineteen, and now, during the race, he's thinking about shifting up to twenty. This is something I never do. Sometimes I'll look down at my chain to see if it's high or low on the cassette, and I generally know whether I'm in the big or small ring simply by speed and cadence, but I don't pay attention to exactly which gear I'm in. I don't really see the point.. If I have a certain effort and cadence I'm looking to maintain, then I'll shift whenever I need to in order to keep them where I want them.

Does anyone else do this?

I don't. I fret about gears when I'm choosing a cassette, but once it's on I don't think about it too much.

You'll also notice that he talked about measuring his course by counting every single pedal stroke he took then doing the math between gears and tire circumference. He's using his cadence and gear as a relative speed measurement, which we now all get instantly via our bike computers. It's also a bit of a machismo thing...he doesn't want to resort to using his lowest gear to defeat the climb.

Things are different in the power-meter era. Back in the day, gear and cadence was used for lots of stuff.

I recall one tip about sprinting, was to put the bike in the most likely sprinting gear, say 53x16 for example, and pedal backwards from the finish line for 20 strokes to find the optimal starting point for the final kick. There were lots of rules of thumb like that.

Anyway, I glance down fairly often, mainly to make sure I'm not cross-chaining too badly.

It's psychological mostly.

On a really hard climb, especially one I don't know that well, I hate being in the last (biggest) cog. I always want a bail-out, just in case I go around a corner and it gets really steep.

Uh, wasn't the book published in the late 70's? Back when everyone had significantly less cogs in the rear than they do now? Meaning gear selection was more important?

There have been many a race when I would keep trying to find an easier gear and would look back to confirm that i do indeed suck on long climbs.
39x21.....ouch...39x23...grr this is steep...39x25...man this must be some sort of magnetic hill pulling me backwards! 39x....25...25.. Dammit.

Too much thinking.

I let my legs think about the gear, not my brain, so to speak.

My brain is too busy telling my legs to shut up, and cannot be bogged down with anything else.

I don't think it's at all unusual to look at a race profile, and figure out what kind of gear you need for it. And your estimate of the right gear for a climb will likely vary a bit, between the estimate and reality.

Now I would imagine that most folks would simply think as they were actually doing the climb that they needed to go up or down a cog to maintain their desired cadence without blowing up, rather than think I need to be in the 42/19.

But remember there's a bit of a literary device here where he's trying to explain what's going on to the reader. So you might not think in express terms all the concepts that the voice narrating the book has to state to explain to the reader, even though you're doing the same thing when you ride, just not narrating it to an audience in full sentences.

I do the same thing you do. I find myself pushing the hardest gear I can push at 80-90 rpm's. I couldn't recite gear combinations if I tried.