According to Byers-Heinlein et al. (2010), Infants are born with linguistic capacity. While different studies has shown that monolingual infants are capable of differentiating between their native language and a foreign language, In Byers-Heinlein et al (2010) study, two sets of five days old infants whose parent spoke Tagalog and English during pregnancy were tested . They also tested monolingual infants whose parents only spoke English during pregnancy, for language preference. In the study, Byers-Heinlein et al.(2010) recorded the amount of sucking that occurred when either one of the languages spoken by their family to see which one they showed preference to. The researchers also recorded the Sucking of children who are monolingual in English. They found that the children whose native language is English responded more to English than Tagalog. The children whose native language was both Tagalog and English showed an indifference reaction, showing that these children are able to recognize their languages even at 5 days. Code switching video

  • Research investigating early childhood bilingualism suggests two opposing theories explaining how the child learns to separate the two languages; a one-system theory in which the languages are gradually differentiated and a two-system theory in which the child is able to differentiate the two languages from the earliest stages of linguistic development. Earlier studies have used changes in language mixing patterns as the main source of support for either a one- or a two-system theory. This approach is criticized on the grounds that a decrease in language mixing may reflect both a growing awareness of the difference between the languages as well as other factors such as an increase in the number of translation equivalents. In the present study a different approach was taken, i.e., using other measures of code differentiation and investigating the extent to which these correlated with language mixing. The results showed that children who avoided using their other language in a word test situation when naming pictures of objects which were not known in one of the languages (thus classified as having differentiated the two languages) showed significantly less mixing in their speech than children who freely substituted words from their other language for items not known. These results give support for a one-system theory of bilingual language acquisition.