
Someone asked me at the release party Thursday night if it's true that "it gets harder to learn a language as you get older". And I gave her my usual weasel answer: It depends. I don't really buy the "critical period" hypothesis. I haven't known too many people in my life who could pass for native in a language they only learned in adulthood, but you only need to meet one, right? It really comes down to how much damn effort are you going to put into "perfect" rather than "more than good enough for government work" and--with few exceptions--the answer is going to be "not much".
The hardest part is that language learning chiefly consists of rote memorisation, and as we all know the memory is the second thing to go. It annoys the hell out of me to find myself looking up a word that I know I've looked up a half dozen times before--maybe even earlier the same day! Perhaps I'm fooling myself when I muse that it would've taken me at most two glances to cement it back when I was twenty. Actually, I know I am, but it sure seems that was the case.
On the plus side, as I explained that evening, languages show more similarities than differences, and the more you see the firmer your sense of what the range of variation really is. Sure, you can find some crazy features out there, but unless you're studying Pirahã or Guugu Yimithirr, most everything will work the way it does in some language you already know. It's just a question of figuring out which of the handful of common alternatives is the one that counts.
Take, for instance, demonstratives (e.g. "this", "that"). The Eskimo-Aleut languages are notorious for making a plethora of distinctions--how close the item is, how much space it occupies, whether or not it is visible--over twenty combinations in all. But that's an outlier; most languages have only two degrees of what is called deixis. Some add a third, either distinguishing "by me", "by you", "by neither of us" (e.g. Spanish) or "by me", "away from me", and "way far away from me". When it comes to expressing deixis with nouns, some languages use distinct determiners while others use only one (usually identical to the definite article, if there is one) in combination with an adverb, cf. dialectal English "this here". Many languages allow demonstratives to double as pronouns third-person pronouns.
So when I took up Swedish, learning the grammar was chiefly a matter of going through a mostly-unconscious mental checklist: Okay, demonstratives. Two degrees or three? Two. Distinct stems? No. Double as pronouns? Yes. If anything it was even easier than that. Because if you know German, you'll readily recognise that those answers are all the same[*]. So more often than not, the question I was really asking was, "Same as German here, or different?"
Which is, in the end, why I decided to tackle Swedish in the first place. It's always bugged me that I can read most West Germanic languages easily, but put a North Germanic one in front of me and I just stare dumbly at the page. I knew it was mostly a question of knowing a relatively small stock of non-cognate (or at least not recognisably cognate) function words. Once you can map, say, någon to einig and ingen to kein, vast swathes of incomprehensible verbiage suddenly open up. (And, of course, studying one Scandinavian language is basically getting the others for free.)
[*] With minor qualifications. E.g. a distal demonstrative--jener--does exist in German, but it's literally, use of demonstratives as pronouns is colloquial, etc.