[xormapmap]

The idea that child brains are better at learning languages is a myth. Adults struggle with languages because traditional language education is not fit for purpose. If you took a child and isolated them in such a way that they never got comprehensible input, and instead only gave them traditional language lessons (think textbooks, grammar drills) - they too would struggle. The good news is that if you take an adult and give them comprehensible input like you would a child, they will learn at least as effectively as a child.

[ThrownOffGame]

What about pronunciation? Many of the assertions I've heard about adults in a foreign language is about our ability to recognize, differentiate, and reproduce the different phonemes, many which do not exist in our language.

These phonemes are even more difficult to recognize when we're not conversing face-to-face and in-person! So if you're listening to "comprehensible input" if it's on audio, or video voice-over, it is much inferior to seeing/feeling/hearing a native speaker make sound-shapes with their mouth!

I made many efforts to imitate my Spanish teachers in my youth, in terms of pronounciation, mouth shapes, accent and emphasis, etc. I credit the in-person instruction with achieving a nearly fluent comprehension and ability to make myself understood.

So the argument goes: if an adult is set in their ways and knows a particular set of phonemes, (or even tones, etc.) is it more difficult than a blank-slate child who has no prejudice about hearing and learning new sounds?

[thaumasiotes]

> if an adult is set in their ways and knows a particular set of phonemes, (or even tones, etc.) is it more difficult than a blank-slate child who has no prejudice about hearing and learning new sounds?

The answer is sort of "yes". If an adult is set in their ways and knows a particular set of phonemes, they will have a more difficult time with the phonemes of a new language than an infant would.

However, "learning new sounds" is not a correct way to think about it. You're born knowing all the sounds. You unlearn the differences between certain ones. If you, as an adult, have unlearned a difference that matters in your target language (because it didn't matter in your native language), you will have trouble with that difference. An infant can't have this problem.

Note that the cutoff point where an immersed child will fail to learn the pronunciation of a new language "automatically" is somewhere in the late teens, though.