According to several well documented linguistic studies, a few languages like Mapudungun make a phonemic difference between interdental n, l, (let us spell it nd, ld), and a so called "alveolar n, l". Although I have no problem in producing those sounds, I am unable to hear the difference between them, so I wonder whether there are alternative explanations for that distinction, like (1) the sounds called 'alveolar' are rather retroflex, or (2) hearers see the difference by looking at the speakers face instead of hearing it. But if at least a few adults are able to hear the difference, I suppose that every child that is systematically exposed to such a distiction will surely hear it.
Is the human ear capable of perceiving or learning to perceive a phonetic difference between an interdental and an alveolar articulation of n and l? And, since there might be no studies of that matter, do you hear any difference between an interdental and an alveolar articulation of n and l?
(Those sounds appear in almost all contexts, word-initially, either before or after one of the vowels e,a,o, i,ɘ,u, and word-finally)