There's a mirror in my building's lift. I have ridden in it perhaps nine hundred times. Today I wondered why it was there.

My first guess was vanity — a last check before you step out. Reasonable, and wrong, or at least not the origin.

The actual reason

When lifts first became common, people complained constantly about the wait. The engineering answer would be: make them faster. That's expensive, sometimes physically impossible, and in many buildings the lift was already near the limit of what the shaft allowed.

So someone tried a different thing. They put mirrors in the lobbies and the cars.

Complaints dropped. The lift wasn't faster. People now had something to do — look at themselves, discreetly look at everyone else — and the wait stopped registering as waiting.

Why I can't stop thinking about it

The complaint was "the lift is slow." The fix had nothing to do with speed.

That gap is the interesting part. The stated problem and the real problem were different, and if you'd taken the complaint literally you'd have spent a fortune on a marginally faster lift and received the same complaints.

I do this at work constantly. Someone says a page is slow. Sometimes the answer is to make it faster. Sometimes the answer is that it gives no feedback for two seconds, so it feels broken, and a spinner costs nothing and fixes the actual experienced problem.

Neither answer is a trick. The perceived wait is a real thing a real person experiences. Treating "make the number smaller" as the only legitimate fix is its own kind of laziness — it's the version of the problem that's easiest to measure, not necessarily the one that's hurting.

The caution

Obviously this can go wrong. A spinner on a query that takes forty seconds is a lie. The mirror works because the wait was already nearly reasonable, and the problem was attention, not duration.

Know which one you have. Then you can choose a mirror honestly.