How do monolingual and bilingual English and Spanish learning infants distinguish vowels?

Research on monolingual infants shows that speech perception abilities of infants are affected by their language experience.  Although there are no exact statistics available, it has been suggested that there are as many, if not more, children growing up bilingual than monolingual (Tucker, 1998). Despite the growing bilingual population, as researchers, we have few answers concerning the speech and language development of the sizeable, bilingual part of the population.

In this study we ask if bilingual infants learning Spanish and English are able to distinguish between English vowels at the same age as their monolingual peers. We are particularly interested in vowels that are present only in English not Spanish. We have tested 4-month-old monolingual English, monolingual Spanish, and bilingual English and Spanish learning infants on their ability to distinguish the vowels in the words “take” and “tic” (note Spanish only has the first type of /e/ sound, but not the second). Infants in all three groups are able to distinguish the contrast. This replicated previous findings that very young infants are “citizens of the world”.

We have also tested 8-month-olds and 12-month-olds in all 3 groups, however, and all three groups fail, including the monolingual English-learning infants fail. We believe this is because English-acquiring infants have not yet encountered enough examples in their input that allow them to conclude these two vowels are different phonological categories in English. We are currently testing 18-20mo infants to verify that English-acquiring infants go through a U-shaped learning path to vowel acquisition, and hope to find a similar pattern in the bilingual group.