3. The psycholinguistics of bilingualism The psycholinguistics of bilingualism is aimed at studying the processes involved in the production, perception, comprehension and memorization of the bilingual's languages (spoken, written or signed) when used in a monolingual or a bilingual language mode. Until recently the emphasis has been put on the independence of the bilingual's languages (how does the bilingual keep the two languages separate? does the bilingual have one or two lexicons?) to the detriment of issues such as the on-line processing of language, be it in a monolingual or in a bilingual language mode. Much research was conducted, for example, on the coordinate-compound-subordinate distinction. According to it, there are three types of bilinguals: coordinate bilinguals who have two sets of meaning units and two modes of expression, one for each language (this means that the words of the two languages are totally separate entities); compound bilinguals who have one set of meaning units and two modes of expression ("equivalent" words in different languages have the same meaning); and subordinate bilinguals who have the meaning units of the first language and two modes of expression: that of the first language and that of the second, learned by means of the first (here the bilingual interprets words of the weaker language through the words of the stronger language). Despite the inherent appeal of this distinction, no amount of experimentation has brought conclusive evidence that bilinguals can be classified as coordinate, compound or subordinate.
Another area of considerable investigation has been whether bilinguals possess one or two internal lexicons. Proponents of the one-lexicon view (also referred to as interdependent storage) state that linguistic information is stored in a single semantic system. Words from both languages are organized in one large lexicon, but each word is "tagged" to indicate the language it belongs to. Other researchers have claimed that bilinguals have two lexicons (the independent storage view), and that the information acquired in one language is available in the other only through a translation process. Again, despite a large number of studies, no clear-cut results have been found. In fact, it has been proposed recently that bilinguals have three stores, one conceptual store corresponding to the bilingual's knowledge of the world and two language stores, one for each language.
A third issue of interest has been the ability of bilinguals to keep their two languages separate in the monolingual mode. Researchers have postulated the existence of a language switch which allows bilinguals to gate out the other language, and experimental studies have been conducted to find evidence for this proposal. The results obtained have been inconclusive or, at the very least, questionable, and currently it is felt that no switch, be it psycholinguistic or neurolinguistic, exits in bilinguals. Rather, it has been proposed that bilinguals are probably using various activation and deactivation procedures to maintain their languages separate in the monolingual mode and to make them interact in the bilingual mode.
Now that it is more generally accepted that the bilingual is not two monolinguals in one person, but a unique speaker-hearer using one language, the other language, or both together depending on the interlocutor, situation, topic, etc. (see above), current psycholinguistic research is trying to understand the processing of language in the bilingual's different language modes. Researchers are studying how bilinguals in the monolingual mode differ from monolinguals in terms of perception and production processes, and they are investigating the actual interaction of the two languages during processing in the bilingual mode. This latter issue has produced some interesting findings. For example, in the recognition of "guest" words (borrowings and code-switches) the phonotactics of the word (whether it is marked clearly as belonging to one or the other lexicon), the presence or absence of a base language homophone, the language phonetics of the word (the pronunciation of the guest word in one language or in the other), and the language that precedes the word (the base language context), all play a role in the recognition process. Actual models of bilingual processing are now being proposed to account for the data obtained. Thus, an interactive activation model appears to accommodate the word recognition results just presented. In the production domain, researchers are attempting to explain the underlying processes involved in the on-line production of code-switches and borrowings and a number of models are also being proposed.