Monolingual and bilingual children can discriminate between different languages. According to research done in the area of phonological development by Sebastian-Galles and Bosh (2001), monolingual and bilingual infants are born with the innate ability to distinguish languages of different rhythmic classes, for example English and Spanish. As infants reach 2 months of age, this ability is reduced to the discrimination of their maternal language from other languages with different rhythm, showing that babies have already build up an initial representation of their maternal language. For example, a 2 month old Russian baby can discriminate between Russian and Spanish. At around 4 1/2 months, infants learn to use other cues such as prosody and phonotactics in order to discriminate languages that belong to the same rhythmic group such as Spanish and Catalan.
Another experiment conducted by Burns, Yoshiba, Hill, and Werker (2007) studied and compared voice onset time (VOT) recognition by infants in French and English. Results provided evidence that no differences in discrimination were observed in 6-8 month old monolingual and bilingual infants, showing a general language pattern of responding. On the other hand, experiments conducted with babies who were 10-12 month and 14-20 month old showed a more developed language specific pattern of responding since monolingual babies were able to discriminate the phonetic boundary in their native language while bilinguals were able to discriminate both boundaries.
These studies indicate that infants are able to discriminate languages and sounds without confusion. They also provide us with relevant evidence that bilingual infants develop from early in life two different phonological systems, and that these bilingual children follow the same time course and manner of language development and acquisition that their monolingual peers do.