It has been suggested that the structural composition of mixed languages and the linguistic processes through which they emerge are to some extent predictable, and that they therefore constitute a language “type” (e.g. Bakker and Mous, 1994b; Bakker and Muysken, 1995). This view is challenged here. Instead, it is argued that the compartmentalisation of structures observed in mixed languages (i.e. the fact that certain structural categories are derived from one “parent” language, others from another) is the result of the cumulative effect of different contact mechanisms. These mechanisms are defined in terms of the cognitive and communicative motivations that lead speakers to model certain functions of language on an alternative linguistic system; each mechanism will typically affect particular functional categories. Four relevant processes are identified: lexical re-orientation, selective replication, convergence, and categorial fusion. Different combinations of processes will render different outcomes, hence the diversity of mixed languages as regards their structure, function, and development.

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.