In this article, the author addresses the question of how the mind represents two languages in simultaneous bilingualism. Some linguistic theories of intrasentential code switching are reviewed, with a focus on the Minimalist approach of MacSwan (1999b); the author concludes that evidence from code switching suggests that bilinguals have discrete and separate Lexicons for the languages they speak, each with its own internal principles of word formation, as well as separate phonological systems. However, the author argues that computational resources common to the two languages generate monolingual and bilingual syntactic derivations alike. Advantages of the Minimalist Program for the analysis of code switching data are discussed at some length.

This study examined the recognition of English words by groups of native speakers of Italian who differed in age of arrival in Canada and amount of continued native language use. The dependent variable was the number of words correctly repeated in English sentences presented in noise. Significantly higher word recognition scores were obtained for early than late bilinguals, and for early bilinguals who used Italian seldom than for early bilinguals who used Italian relatively often. A hierarchical regression analysis showed that the native Italian participants' ability to perceive English vowels and consonants accounted for a significant amount of variance in the word-recognition scores independently of age of arrival, amount of L1 use, and length of residence in Canada. The native language use effect was interpreted to have arisen from differences in the extent to which the early bilinguals' Italian phonetic system influenced the representations they developed for English vowels and consonants.

This study examined pronunciation proficiency in both the first (Korean) and second (English) languages of bilinguals. The participants were adult immigrants whose age of arrival in the USA ranged from 1–23 years. English and Korean sentences were rated by native listeners to obtain measures of pronunciation proficiency. English pronunciation of participants with ages of arrival of 1–5 years was close to monolinguals, heavier accents were noted as ages of arrival increased from 6 to 23 years. Korean pronunciation of participants with ages of arrival of 1–7 years was distinctly accented, while those with ages of arrival of 12–23 years were rated the same as monolinguals. Participants with ages of arrival of 1–9 years pronounced English better than Korean, whereas the reverse was true for ages of arrival of 12–23 years. Overall, the results were more consistent with the view that deviations from native pronunciation result from interactions between the languages of bilinguals rather than with the view of a maturationally defined critical period for language learning.

The longitudinal study reported in the present paper examines L1 vocabulary decline by a child whose native language input effectively ceased after her immersion into the L2 environment. The subject of the study was a Russian girl adopted by an American family, brought to the USA, and completely isolated from any contact with the Russian-speaking environment. The analysis of the data was based on the results of picture naming tasks and reaction time measurements. Three groups of words showed high vulnerability to forgetting: high frequency words, cognates, and semantically convergent pairs (pairs of words lexically distinguished in L2 and non-distinguished in L1). Fast forgetting of these lexical items in L1 was related to the acquisition of their equivalents in L2. The comparison of noun versus verb retention/acquisition suggested that there might be a delay in L1 verb forgetting / L2 verb acquisition at the early stage of an extensive exposure to the second language.

We contrasted the effect of instruction-induced expectancies and language intermixing in an English lexical decision task performed by Dutch–English bilinguals. At the start of the experiment, participants were instructed to respond to interlingual homographs and exclusively English words by giving a “yes” response, and to English non-words and exclusively Dutch words by giving a “no” response. In the first part of the experiment the stimulus list did not contain any Dutch words. In the second part of the experiment, Dutch items were introduced. No significant differences were found between interlingual homographs and controls in the first part of the experiment, while strong inhibition effects were obtained for interlingual homographs in the second part. These results indicate that language intermixing rather than instruction-based expectancies drives the bilingual partipants' performance. Consequences for current views on bilingual word recognition are discussed.