[ken]

> My understanding is that the younger you are the easier it is to pick up a foreign language.

The latest research I've seen indicates that this is false. When you look at vocabulary in "words learned per hour of study", adults actually do much better than children. (I'm sure I've seen a study of this involving the U.S. State Department or some such, but I can't find it right now.) This isn't surprising to me: adults already know noun/verb/adjective/adverb, how [a] grammar works, a big pile of cognates/loanwords, etc.

The reason children seem to learn quicker is because they're exposed to the language every hour of the day. They have no choice. If they want to do anything at all, it requires using the target language. They make up for lower efficiency by brute force.

Adults tend to do poorly at learning foreign languages because they only spend an hour or two a day with it. Learning a language feels like a lot of work, and adults usually fail because they have the resources to be able to avoid interacting with it. This is also why "full immersion" (living in a place where they speak that language) is fast and effective even for adults.

(Think you're going overboard by spending 3 hours a day studying French? That's less than 1/5 of your waking hours. Any child in Paris will learn French 5 times faster, not because they're younger but because they're putting in an extra 13+ hours a day exposed to French.)

> I know lots of people that regret not learning a 2nd language earlier in life.

Sure, and I know people who regret not learning to dance, getting in shape, playing a musical instrument, etc. I also know people who started these things as adults and are just as accomplished as those who started young. And I know many people who started these things when they were young, and then gave them up -- and have basically lost all the effort they put into it. (After long enough, you can even forget your first language.) This fascination with youth needs to end.

[SilasX]

>The reason children seem to learn quicker is because they're exposed to the language every hour of the day. They have no choice.

They also have an environment of understanding adults willing to explain their mistakes and teach how to say what they want.

If you’re already an adult, this is hard to find. People will either switch to your language, ignore you, or find some common language (even ad hoc hand signs) to communicate.

[gringoDan]

This is sometimes the case. But in my experience, a lot of people (strangers even) are more than willing to help you out. They are excited that you are learning their native language and want to see you succeed.

A good portion of the time, what you're describing stems from the language learner defaulting to an easier version of communication or trying to avoid embarrassment.

[amaccuish]

I see it more as several stages of life, some easier than others:

baby/toddler growing up in a multilingual environment = fairly easy

baby/toddler growing up in a monolingual environment = difficult

Young child -> teenager (e.g. I actually began learning french in primary school) = slow and difficult

Late teens -> young adult = the best time after baby/toddler

+40 = more difficult but not impossible

[shard]

Learning a foreign language is more than just learning grammar and vocabulary. It is also learning to distinguish the different sounds of that language and the ways to make those sounds. I can't do the searches for it right now, but from what I recall, people lose the ability to distinguish sounds that they don't hear often by a very young age, since their brain figures it's not important to distinguish those, so that it becomes increasingly harder to pronounce and understand those languages which use different sounds. This is why L and R differentiation is very hard for Asian speakers, and tonal languages like Chinese and Vietnamese are very hard for English speakers.