As Kolers (1972) has pointed out, the study of bilingualism offers a distinctive way to study some of the mental activities underlying the way that people use language. Code-switching (the introduction into the context of one language stretches of speech which exhibit primarily the other language's phonological and morphological features) offers a unique opportunity for studying some of the more complicated aspects of bilingual speech, particularly regarding the momentary choice of language. Researchers whose work has influenced this paper include Haugen, Weinreich, Mackey, Fishman, Rayfleld, Clyne, Hasselmo, Gumperz, Diebold, Lance, Valdés-Fallis, Pfaff, and Timm. Among the list of poorly understood phenomena in code-switching are (I) seemingly unpredictable switching, and (2) the possibility of formal, complex rules underlying different code-switching patterns. It is these open questions which modelling might illuminate.
