English and Korean stop productions of monolingual versus bilingual children

A long-standing issue in the theory and description of bilingualism is whether bilingual children develop one or two linguistic systems in the learning of their two languages. The one-system hypothesis (Swain, 1972; Volterra & Taeschner, 1978) suggests that children initially posit linguistic rules common to both languages; then they differentiate the two as they master higher linguistic knowledge. The two system hypothesis (Padilla & Liebmann, 1975; Genesse, 1989), conversely, holds that bilingual children differentiate both systems at an early age, and that children are capable of keeping the two linguistic systems separate as these develop. Although researchers have made attempts to answer this question in several linguistic domains, including phonology, semantics, and syntax, there continues to be a marked lack of research on whether bilingual children develop one or two distinct phonetic systems. The results reported in this paper are part of an ongoing project investigating phonetic category formation in Korean-English bilingual children. We have investigated the underlying phonetic systems in bilingual children (Lee & Iverson, 2011) by examining whether they can manifest language specific phonetic (acoustic) values for two languages when two phones fall into the same phonological category. For example, although Voice Onset Time (VOT) values of /p/ in English and /ph/ in Korean are similar, the vowel-onset fundamental frequency (f0) value of Korean aspirated stops is higher than that of their English counterparts. If a Korean-English bilingual child produces both