I asked this question over on Facebook and it got quite a few comments!
Plus many more! Thank you everyone! 🙂
It’s generally agreed that the best time to learn is from birth. Especially the first year is where young children can assimilate and learn all the new sounds of an almost infinite amount of languages.
This ability tends to slow down a touch after one year and then again around 10 years or so.
So from this aspect, i.e. getting perfect pronunciation, then the earlier the better.
However from a time point of view, adults do actually learn languages more quickly than children.
So for a smart adult it only takes around 3 months to learn to speak a foreign language (and paradoxically it often takes longer when actually “in country”. I have a feeling this might have something to do with deadlines and goals)
Children usually take around 18 months to 2 years of speaking to learn a foreign or second language with the right amount of input and opportunity. ( The distinction between second and foreign language doesn’t have nearly as much influence in today’s world as it did say 20 years ago)
So when should kids learn languages? To get a perfect accent then as early as possible, ideally from birth or before. They’ll get the input and then once they start physically speaking they will automatically begin to speak all the languages they are exposed to.
But it all comes down to your priorities.
Kids do have a limited time (you only have 18 summers with your kids!) so if you value music, nature skills, art or something more than a 3rd or 4th language then you could leave those languages till later when they can learn them more quickly, but of course without a transparent accent. 🙂
P.S. The majority of kids in the world are already bilingual or trilingual, so be wary of arguments saying that languages can “interfere” with their own native language. That only happens in very rare cases and hardly ever if they are living in their native language country. Goethe said ““He who does not know foreign languages does not know anything about his own”. However, of course, certain politicians are often scared of their population getting their information from overseas so are very keen on spreading these “myths” to stop people learning so quickly! 🙂