Simultaneous bilingualism and the perception of a language-specific vowel contrast in the first year of life.

Behavioral studies have shown that while young infants can discriminate many different phonetic contrasts, a shift from a language-general to a language-specific pattern of discrimination is found during the second semester of life, beginning earlier for vowels than for consonants. This age-related decline in sensitivity to perceive non-native contrasts has been generally attested in monolinguals. In order to analyze the impact of bilingual exposure on the perception of native-sound contrasts and the early building of language-specific contrastive categories, four-month-old and eight-month-old infants from Spanish monolingual, Catalan monolingual and Spanish-Catalan bilingual environments have been tested with a familiarization-preference procedure on a vowel contrast present only in Catalan: /e/-/epsilon/. As expected, younger infants were all able to perceive this contrast, independently of the language of exposure. However, by eight months, only infants from Catalan monolingual environments succeeded. Although the decline in sensitivity with the monolingual Spanish group was expected, the results with the bilingual group challenge the view that mere exposure is enough to maintain the capacity to perceive a contrast. An additional experiment at 12 months of age indicated that bilinguals finally regained discrimination. Together these results suggest a specific developmental pattern of perceptual reorganization in bilingual exposure.