Of all the things Spanish learners must get used to, the rules surrounding when to use the formal “usted” and when to use the informal “tu” are among the most vexing.

In some ways, we’re actually dealing with two languages, and they’re mostly the same, but you must size up a person and then decide which language to use. Your decision is loaded down, meanwhile, with questions about respect and friendship.

In Mexico, the rules went something like this: close friends, people much younger than you, and parents get the “tu.” Strangers and people older than you get “usted.”

The formal is meant to be used as a sign of respect, as a way of creating distance, since it is actually the same verb conjugation as is used for the third person. So for example, if you want to ask “are you alive,” in the formal way, you would literally say “is he alive,” and if it wasn’t clear who was being talked about, you would throw in an “usted” for good measure.

But it was those border lines that were confusing. What would you use with someone your age you just met at a very informal party? Usted or tu? How much younger did the stranger have to be before you could use tu? Ten years? Twenty? Just obviously younger?

And who made the rule that parents get tu but grandparents get usted? Aren’t we usually on pretty informal terms with our grandparents?

Why does God get tu but if you’re a bank teller and some guy comes up with a gun and demands money, you have to use usted? At the end of the day, which one is more deserving of formal respect?

But like with the rolled r sound, I didn’t let this confusion get to me. I just plugged away at it, and got to be pretty decent. Then I moved to Costa Rica, and all my hard-earned experience went out the window.

I noticed it on the first day, when some kids started using usted with each other. Odd, I thought, but maybe just an anomaly. Then I heard a husband use it with his wife. Then, someone used it on a pet dog.

Turns out the whole country uses usted for everything. Everyone understands tu when I use it (why does this gringo sound so much like a Mexican, they wonder), and since much of the available media is from other countries, they hear it all the time too. But tradition persists. Why? For that answer I went to my old Spanish teacher Wesley Curtis, who, besides being a serious traveler,  actually has some formal training in language acquisition. Here’s what he said:

“Good hearing from you, Pete. I didn’t realize you had already made it down to the “Suiza de Latinoamérica.” I’m kind of envious. Regarding your hosts’ tendency to use Usted, that’s not a phenomena entirely unique to them. In Mérida, Venezuela, where I spent around six weeks in the summer of 2004, this same “rule” applied.

“Although the rationale or impetus behind it is probably different where you are, there are a couple scenarios for Mérida. Given that there was formerly a large Andean indigenous population in the area, and the fact that they were essentially slaves or almost always subservient to their Spanish counterparts, it was natural that the tú form was virtually unnecessary or unusable for them.

“In the case of Costa Rica, the explanation is probably completely different given that the Taíno “Indians” were almost entirely wiped out by diseases brought by the Spaniards. However, we should take into consideration that the “Vos” form is still used widely in some regions of the country (and in varying forms throughout virtually all of Central America). This, combined with the sociolinguistic reality that “vos” was at this time a form of address for “inferiors,” resulted in an almost exclusive deference for the “Usted” form as a means of demonstrating respect and avoiding punishment or scolding. But given that I don’t know the actual village you are in, this is just conjecture.”

Thanks, Wesley! It sounds like the exact answer is something you might find buried in a masters thesis somewhere, but I guess those are the breaks with ancient language customs.