through long training in the mother tongue (quite properly) get into the habit of noticing by and large only the parts that are relevant to catching the meaning, and of paying no attention to–literally not noticing–anything else. (p. 213)
For vowels in particular, learning to listen to English will often require that the student develop vowel categorizations appropriate for English. English vowels are distinguished by the following characteristics: tongue position and height within the oral cavity, lip rounding or spreading, tension, and gliding (vs. simple vowels). Length is not a distinguishing feature, but instead is influenced by the vowel’s environment (Celce-Murcia, Brinton, & Goodwin, 2010).