Yeah, like I said, it's most unlikely that you're using vowel length correctly. You can't copy something you're not aware of. For example, without looking it up, would you say 'quit' and 'quid' are pronounced with the same vowel length or not?
Babies haven't already acquired another language, when they're learning to speak, and so there's no interference. That's not the case when someone learns a second language later in life.
> "Quid" is longer.
Feel free to post a voice recording, so we can check.
Interference doesn't matter if all you're doing is copying what people do with their mouths. You might have more or less trouble performing the movement at the mechanical level (for example a lot of people have trouble doing the French R) or listening for the precise positions of the tongue etc., but just copying what you can hear is trivial.
>Feel free to post a voice recording, so we can check.
Nah. I have no interest in convincing you; honestly accepting to be tested at all is probably more than I should have done. I'm merely relaying a personal experience for your edification. If you can't accept it for what it is then continue as you were.
Interference absolutely does matter. Interference manifests itself in the form of a foreign accent, which most people have when they speak a second language. You're making an extraordinary claim, namely that you're able to speak a second language without a foreign accent. I find your claim extremely unlikely to be true, especially since you provide no evidence and you've shown that you know very little about language acquisition.
"With correct pronunciation" and "without an accent" are not equivalent qualifiers. There's no such thing as the null accent. Obviously I will have an accent relative to any speaker, since I don't live in an English-speaking community and so I'm not copying the exact pronunciation of any single community, but rather approximately averaging the pronunciations of all the speakers I hear.
Like I said, I have no interest in convincing you. If you can't accept what I say for what it is, continue as you were.