The aim of this study is to test Macswan’s ((1999). A minimalist approach to intrasentential code switching. New York, NY: Garland; (2000). The architecture of the bilingual language faculty: Evidence from intrasentential code-switching. Bilingualism: Language and Cognition, 3, 37–54; (2005). Codeswitching and generative grammar: A critique of the MLF model and some remarks on "modified minimalism". Bilingualism: Language and Cognition, 8, 1–22.) PF Disjunction Theorem (PFDT), which was proposed based on Chomsky’s ((1995). The minimalist program. Cambridge, MA: MIT Press.) minimalist programme, to answer the following question: Is code-switching (CS) behaviour governed by CS-specific grammar or an innate mechanism that produces monolingual and bilingual utterances in our language faculty?

A quantitative approach was adopted to test the PFDT with the Southern Min/Mandarin CS data.

811 lexical items extracted from 343 bilingual clauses in my Southern Min/Mandarin CS corpus, and almost no violation against this model (i.e., a word-internal switch) was found, except one example that was regarded as the informant’s slip of tongue.

The results of this study confirm the prediction of the PFDT that phonological systems cannot be mixed within a word.

Although the morphosyntactic structures and in some cases the pronunciations of morphemes are identical, tonal differences of these two languages still prohibit word-internal switches.

This study thus supports the PFDT and argues that CS behaviour is governed by a single innate mechanism that governs both monolingual and bilingual language production and that the so-called CS-specific grammar/mechanism is not necessary.