A central question in this area concerns whether infants respond to phonetic differences in a manner similar to that of adults.

Studies examining cross-language and native-language speech perception suggest that infants are born with universal sensitivity to the phonemes that are present in all languages.  For example, a study of English-speaking adults, Hindi-speaking adults, and six- to eight-month-old infants from English-speaking families demonstrated that infants distinguished two distinct phonemes with similar sounds in both English and Hindi—/ta/ and /da/ in English and the retroflex /D/ and dental /d/ in Hindi—whereas adults distinguished only between different phonemes in their native language. 

Infants are born with the ability to perceive just those sounds that  are phonemic in some ;language; it s possible for them to learn any human language they are exposed to. They have begun to learn of their parents. Before that, they appear to know the sounds of human language in general. 

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