Mechanics' Meaningful Music
It is often claimed that an adult cannot learn the sound system of a new language. This claim is followed by the caveat that some adults do, but these adults are dismissed as exceptional, and non-typical. Certainly, they are exceptions, because most people don't, but there's a big difference between "don't" and "can't".
A sound system is composed of phonemes, which are often defined as minimal units of meaning in sound. Every human is capable of producing a whole range of sounds, regardless of their language, and to process every single detail of the sound produced would simply be too much for the brain, so we bundle the sounds up together, and even though the sounds of the T in "try" and "butter" may be slightly different (or completely different, depending on your accent), we still recognise them as being the same thing.
As a general strategy, this works. The adult human meets lots of people with slightly different accents, but the phonemes are all roughly the same, so the detail of the differences is irrelevant.
As a language learner, though, this starts to pose problems. Our brains believe that only certain sounds are meaningful, and therefore discard any information they believe to be irrelevant. If you have a language with two phonemes equivalent to one in your language, you will not believe the distinction is meaningful. Just take a look at Japanese, where they have one phoneme equivalent to the English L and R. Many Japanese learners of English cannot hear the difference between "law" and "raw" or "appear" and "appeal" without active concentration.
Most people get stuck in this rut their whole lives, and this is used as evidence that you can never learn the sound system. But if we step outside the world of language, we might just find reason to be more optimistic.
It's amazing what an experienced mechanic can determine about a car or other machine just by listening to it. Sounds that to you or me would just be squeaks and squeals are to him a full description of the workings and faults of the engine.
Mechanics develops this skill over time through a mixture of direct instruction and experiential learning. The engines they work on give constant feedback that develops into a meaningful structure -- if a given whine co-occurs with a drop in revs, the two become associated and the sound takes on meaning.
But by this reasoning, surely language itself should give a meaningful framework to sounds?
Unfortunately, it would appear not, and it isn't actually that hard to see why.
Language has evolved to have a certain amount of redundancy, a certain level of "fault tolerance". It is very difficult indeed to find any complete sentences that function as minimal pairs (ie that differ by one phoneme only), particularly within the restricted language set that most beginners are faced with.
Going back to my earlier examples, "law" is a noun, "raw" is an adjective. There will always be enough information in the context to tell the two apart. "Appeal" and "appear" are both verbs, but the usages are distinct.
Essentially, I believe that the average learner is never really forced to build a meaningful framework for these differences. The end result is that they get deeper and deeper into the language, building more and more coping mechanisms that a native speaker would never rely on. The model of the language they build is wrong, and while they can understand most things they hear, the person they are speaking to often cannot understand them because, as I said, the native speaker doesn't employ the same strategies as the learner.
What is needed is for the teacher to force a meaningful framework, and the only way I can see that happening is through early teaching of pronunciation. If a learner has to pronounce the difference between ż and ź in Polish, and is corrected when using the wrong one, his brain will know there's a meaningful difference.
It may not be fashionable, but some negative feedback is definitely necessary....