To be fair, that's not my entire reasoning every time. There's usually some sort of initial catalyst that prompts me to study a particular language at a particular time. The French, for example, comes from the foreign language requirement at my high school. You needed two years to graduate, and if you didn't bother picking one, they threw you into Spanish. (I went to high school in Phoenix; as you might imagine, they had somewhere between three and five Spanish teachers at any given time, and one French instructor.) I decided I'd rather be stuck in a classroom with twenty people who had put forth some effort to be there, rather than thirty-five people who had failed to put forth enough effort to get out. It turned out to be a good decision for many other reasons, among them that I adore pulp literature, especially the old stuff, and you can't get much more pulpy than Alexandre Dumas' "Les trois mousquetaires", "Vingt ans aprés" and "Le Vicomte de Bragalonne, ou Dix ans aprés". There's also Gaston Leroux's "Le fantôme de l'opéra" and his lesser-known Joseph Rouletabille detective novels, and all of the strange, dreamy memoirs and novels of aviator Antoine de Saint-Exupéry, including his most famous story, "Le petit prince", which is on the bookcase behind me. (Someday I'll even find somewhere to buy the Arsène Lupin novels that won't charge me an arm and a leg for shipping -- I really need a book called "Arsène Lupin contre Sherlock Holmes", non?) It also turned out to be unexpectedly handy -- I didn't realize it when I was fourteen, but there's a substantial amount of logic and mathematics published in French, including the papers of Benoît Mandelbrot. Pop culture-wise, it's also the third-most common language for the study and industry news of videogaming, which ultimately became one of my favorite research subjects. Canada is generally considered to be in the same market as the US, and historically some of the more interesting production companies have been located in France, like Ubisoft and Infogrames. And I get to read un-mangled versions of Astérix and Les aventures de Tintin.
The Japanese, I also started in high school, with a private tutor. Back in the Dark Ages when I was a teenager, anime and manga had just started to cross over into American culture. There have always been some "classics", like "Kimba, the White Lion", "Astroboy", the movie Akira, and the whole Mobile Suit Gundam franchise, which is to Japan as Star Trek stuff is to the US. Around the mid-90s, though, Americans started to pay much more attention to newer shows and movies -- there was no real commercial market for most of it back then, and for the longest time I saw most of the new, interesting stuff via a membership in TASS, the Tucson Anime Screening Society, and some friends at the University of Arizona who let me crash on their floor during screening weekends. Almost all of it was fansubbed, with the concomitant interesting typoes and occasional half-screen of footnote, trying to explain some obscure pun. (Or just half-screens of dialog -- I distinctly remember Sana-chan from "Kodomo no Omocha" driving several fansubbing circles over the brink of insanity, and to this day I still haven't seen the whole series.) One of the Tucson people was actually from Oregon, where there miraculously existed an Uwajimaya, so we even had (occasional) access to Japanese-language materials. Manga translations at the time were also distinctly crap -- these have also gotten much, much better; Tokyopop used to be terrible, and now they're reasonably accurate -- so all in all, if I actually wanted to know what was going on, I sort of had to learn Japanese.
All three of us here in the
[Peter Greenaway, by the way, is insane. Do not watch any of his movies if you wanted to use that brain any time soon. I thought it might just be that one, but no, Prospero's Books is just as weird and ow.]
The university runs a limited number of Japanese classes, so when I came back after my BA, I took German instead. The Neverending Story was one of my favorite movies when I was a kid, although I do question now who thought it was a good idea to show that to a five-year-old, because it's one serious acid trip. The original novel, "Die unendliche Geschichte", was written in German by a man named Michael Ende, and I'd always wanted to read it to find out if it was just as bizarre as the film. (Yes. Oh god yes. Also, the movie is only the first third or so of the story -- believe it or not, it gets weirder after that.) I have a beautiful early edition hardcover now, with fully-illuminated pages at the beginning of each chapter, along with "Momo", another one of his hallucinatory fairy tales. Ende has the charming quirk of never wanting to print his books in plain black and white; "Die unendliche Geschichte" alternates between black for Bastian's parts and green for Atreju's, and "Momo" is entirely in chocolate brown. German is also useful if you like reading math and physics papers. "Die mathematische Grundlagen der Quantenmechanik" by John von Neumann is actually surprisingly easy to get through in German if you're already familiar with the math. German has also unexpectedly come in handy in the pop culture arena; Roommate the Blonde has had music by a band called Tokio Hotel sitting around for years now, and even though they've broken through into the American music scene, it's still much easier to keep track of them in German. The subtitles on their YouTube vlog are questionable at best, particularly on their singer, who likes lots of big words and has no mute button if he notices that you have brought a microphone into his near vicinity.
My Spanish is rather crap in comparison to those three. I had one class in high school, because they ran out of other things for me to take and wouldn't just let me stay home another hour, and I used to watch Telemundo and Univisión when I lived in Phoenix and they came in our cable package. I suppose it might have helped more if I'd been more interested in watching Plaza Sésamo. I can understand it all right, and I can read perfectly well, as you might guess from the copy of "Don Quixote de la Mancha" that's sitting back on the 'classic literature' shelf with my copy of La chanson de Roland and the Grail romances in French. I also used to have a little book called "Max y el ocito" when I was a very little kid, but it's either long gone or with my mother by now. I find it very frustrating to speak; I can reverse-engineer stuff that I hear or read with a combination of context and knowing other Romance languages, but I don't really have the vocabulary to generate an answer of my own.
I can understand a very small amount of Welsh. This is totally useless unless I want to read news stories on Torchwood or listen to BBC Radio Cymru online.
I speak some Esperanto, which is also mostly useless, unless you count being able to read Harry Harrison novels without checking footnotes, or watch Inkubo without the subtitles.
I can usually decipher Italian via Latin, French and Spanish. Likewise, when I was working for the university conferencing people one summer, I could understand all the Dutch kids we got storming through, via English and German, I just wasn't able to answer. I find the Scandinavian languages also partially-readable, except for Finnish, which is an abomination from Mars. I can extract information from some of Roommate the Blonde's Chinese homework, but of course everything is read differently in Chinese and Japanese, so I can't speak any of it.
I've had one class in Navajo, and one in Arabic. I was by far the whitest person in the beginning Navajo class, which wasn't actually beginning Navajo anyway -- we're right next to the reservation here, and the Navajo kids typically take the course for an easy A, so it was really more like "Navajo Grammar and Orthography for Native Speakers". The Arabic class was just a terrible bust. It was at 9:10 in the morning, which is much too early for me, and instead of being full of ROTC kids and international affairs majors like I thought it would be, it was me, one guy from the political science department, and twenty freshman idiots from the hotel and restaurant management program who had somehow gotten the notion that they were going to be using the language extensively when they opened up giant tourist trap hotels in Baghdad in a few years. I have no idea who told them this, but if I ever find out it'll be very hard to resist the temptation to beat the idea right out of them again. They were extremely rude to the instructor, never shut up no matter what was going on in the lesson, and eventually I just gave up trying to learn anything in there.