with increasing exposure to the ambient language, infants learn not to pay attention to sound distinctions that are not meaningful in their native language, e.g., two acoustically different versions of the vowel /i/ that simply differ because of inter-speaker variability. by 6 months of age infants have learned to treat acoustically different sounds that are representations of the same sound category, such as an /i/ spoken by a male versus a female speaker, as members of the same phonological category /i/.