Babies soon hone in on the subtleties of their mother tongue's phonological idiosyncrasies at the expense of foreign sounds, and what this means for older people learning second languages.
Evidence for pedagogic sense in involving learners' knowledge of L1 to aid their acquisition of L2. Learners associate English letters with Japanese words as a mnemonic. Also, explicit differentiation of the two language systems' phonic systems seems to help better understanding of English in Japanese children.